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Sample records for beam ct reconstruction

  1. Evaluation of the OSC-TV iterative reconstruction algorithm for cone-beam optical CT.

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    Matenine, Dmitri; Mascolo-Fortin, Julia; Goussard, Yves; Després, Philippe

    2015-11-01

    The present work evaluates an iterative reconstruction approach, namely, the ordered subsets convex (OSC) algorithm with regularization via total variation (TV) minimization in the field of cone-beam optical computed tomography (optical CT). One of the uses of optical CT is gel-based 3D dosimetry for radiation therapy, where it is employed to map dose distributions in radiosensitive gels. Model-based iterative reconstruction may improve optical CT image quality and contribute to a wider use of optical CT in clinical gel dosimetry. This algorithm was evaluated using experimental data acquired by a cone-beam optical CT system, as well as complementary numerical simulations. A fast GPU implementation of OSC-TV was used to achieve reconstruction times comparable to those of conventional filtered backprojection. Images obtained via OSC-TV were compared with the corresponding filtered backprojections. Spatial resolution and uniformity phantoms were scanned and respective reconstructions were subject to evaluation of the modulation transfer function, image uniformity, and accuracy. The artifacts due to refraction and total signal loss from opaque objects were also studied. The cone-beam optical CT data reconstructions showed that OSC-TV outperforms filtered backprojection in terms of image quality, thanks to a model-based simulation of the photon attenuation process. It was shown to significantly improve the image spatial resolution and reduce image noise. The accuracy of the estimation of linear attenuation coefficients remained similar to that obtained via filtered backprojection. Certain image artifacts due to opaque objects were reduced. Nevertheless, the common artifact due to the gel container walls could not be eliminated. The use of iterative reconstruction improves cone-beam optical CT image quality in many ways. The comparisons between OSC-TV and filtered backprojection presented in this paper demonstrate that OSC-TV can potentially improve the rendering of

  2. Minimizing image noise in on-board CT reconstruction using both kilovoltage and megavoltage beam projections

    International Nuclear Information System (INIS)

    Zhang Junan; Yin Fangfang

    2007-01-01

    We studied a recently proposed aggregated CT reconstruction technique which combines the complementary advantages of kilovoltage (kV) and megavoltage (MV) x-ray imaging. Various phantoms were imaged to study the effects of beam orientations and geometry of the imaging object on image quality of reconstructed CT. It was shown that the quality of aggregated CT was correlated with both kV and MV beam orientations and the degree of this correlation depended upon the geometry of the imaging object. The results indicated that the optimal orientations were those when kV beams pass through the thinner portion and MV beams pass through the thicker portion of the imaging object. A special preprocessing procedure was also developed to perform contrast conversions between kV and MV information prior to image reconstruction. The performance of two reconstruction methods, one filtered backprojection method and one iterative method, were compared. The effects of projection number, beam truncation, and contrast conversion on the CT image quality were investigated

  3. Motion tolerant iterative reconstruction algorithm for cone-beam helical CT imaging

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    Takahashi, Hisashi; Goto, Taiga; Hirokawa, Koichi; Miyazaki, Osamu [Hitachi Medical Corporation, Chiba-ken (Japan). CT System Div.

    2011-07-01

    We have developed a new advanced iterative reconstruction algorithm for cone-beam helical CT. The features of this algorithm are: (a) it uses separable paraboloidal surrogate (SPS) technique as a foundation for reconstruction to reduce noise and cone-beam artifact, (b) it uses a view weight in the back-projection process to reduce motion artifact. To confirm the improvement of our proposed algorithm over other existing algorithm, such as Feldkamp-Davis-Kress (FDK) or SPS algorithm, we compared the motion artifact reduction, image noise reduction (standard deviation of CT number), and cone-beam artifact reduction on simulated and clinical data set. Our results demonstrate that the proposed algorithm dramatically reduces motion artifacts compared with the SPS algorithm, and decreases image noise compared with the FDK algorithm. In addition, the proposed algorithm potentially improves time resolution of iterative reconstruction. (orig.)

  4. A combination-weighted Feldkamp-based reconstruction algorithm for cone-beam CT

    International Nuclear Information System (INIS)

    Mori, Shinichiro; Endo, Masahiro; Komatsu, Shuhei; Kandatsu, Susumu; Yashiro, Tomoyasu; Baba, Masayuki

    2006-01-01

    The combination-weighted Feldkamp algorithm (CW-FDK) was developed and tested in a phantom in order to reduce cone-beam artefacts and enhance cranio-caudal reconstruction coverage in an attempt to improve image quality when utilizing cone-beam computed tomography (CBCT). Using a 256-slice cone-beam CT (256CBCT), image quality (CT-number uniformity and geometrical accuracy) was quantitatively evaluated in phantom and clinical studies, and the results were compared to those obtained with the original Feldkamp algorithm. A clinical study was done in lung cancer patients under breath holding and free breathing. Image quality for the original Feldkamp algorithm is degraded at the edge of the scan region due to the missing volume, commensurate with the cranio-caudal distance between the reconstruction and central planes. The CW-FDK extended the reconstruction coverage to equal the scan coverage and improved reconstruction accuracy, unaffected by the cranio-caudal distance. The extended reconstruction coverage with good image quality provided by the CW-FDK will be clinically investigated for improving diagnostic and radiotherapy applications. In addition, this algorithm can also be adapted for use in relatively wide cone-angle CBCT such as with a flat-panel detector CBCT

  5. Region-of-interest reconstruction for a cone-beam dental CT with a circular trajectory

    International Nuclear Information System (INIS)

    Hu, Zhanli; Zou, Jing; Gui, Jianbao; Zheng, Hairong; Xia, Dan

    2013-01-01

    Dental CT is the most appropriate and accurate device for preoperative evaluation of dental implantation. It can demonstrate the quantity of bone in three dimensions (3D), the location of important adjacent anatomic structures and the quality of available bone with minimal geometric distortion. Nevertheless, with the rapid increase of dental CT examinations, we are facing the problem of dose reduction without loss of image quality. In this work, backprojection-filtration (BPF) and Feldkamp–Davis–Kress (FDK) algorithm was applied to reconstruct the 3D full image and region-of-interest (ROI) image from complete and truncated circular cone-beam data respectively by computer-simulation. In addition, the BPF algorithm was evaluated based on the 3D ROI-image reconstruction from real data, which was acquired from our developed circular cone-beam prototype dental CT system. The results demonstrated that the ROI-image quality reconstructed from truncated data using the BPF algorithm was comparable to that reconstructed from complete data. The FDK algorithm, however, created artifacts while reconstructing ROI-image. Thus it can be seen, for circular cone-beam dental CT, reducing scanning angular range of the BPF algorithm used for ROI-image reconstruction are helpful for reducing the radiation dose and scanning time. Finally, an analytical method was developed for estimation of the ROI projection area on the detector before CT scanning, which would help doctors to roughly estimate the total radiation dose before the CT examination. -- Highlights: ► BPF algorithm was applied by using dental CT for the first time. ► A method was developed for estimation of projection region before CT scanning. ► Roughly predict the total radiation dose before CT scans. ► Potential reduce imaging radiation dose, scatter, and scanning time

  6. GPU-Based 3D Cone-Beam CT Image Reconstruction for Large Data Volume

    Directory of Open Access Journals (Sweden)

    Xing Zhao

    2009-01-01

    Full Text Available Currently, 3D cone-beam CT image reconstruction speed is still a severe limitation for clinical application. The computational power of modern graphics processing units (GPUs has been harnessed to provide impressive acceleration of 3D volume image reconstruction. For extra large data volume exceeding the physical graphic memory of GPU, a straightforward compromise is to divide data volume into blocks. Different from the conventional Octree partition method, a new partition scheme is proposed in this paper. This method divides both projection data and reconstructed image volume into subsets according to geometric symmetries in circular cone-beam projection layout, and a fast reconstruction for large data volume can be implemented by packing the subsets of projection data into the RGBA channels of GPU, performing the reconstruction chunk by chunk and combining the individual results in the end. The method is evaluated by reconstructing 3D images from computer-simulation data and real micro-CT data. Our results indicate that the GPU implementation can maintain original precision and speed up the reconstruction process by 110–120 times for circular cone-beam scan, as compared to traditional CPU implementation.

  7. Cardiac cone-beam CT

    International Nuclear Information System (INIS)

    Manzke, Robert

    2005-01-01

    This doctoral thesis addresses imaging of the heart with retrospectively gated helical cone-beam computed tomography (CT). A thorough review of the CT reconstruction literature is presented in combination with a historic overview of cardiac CT imaging and a brief introduction to other cardiac imaging modalities. The thesis includes a comprehensive chapter about the theory of CT reconstruction, familiarizing the reader with the problem of cone-beam reconstruction. The anatomic and dynamic properties of the heart are outlined and techniques to derive the gating information are reviewed. With the extended cardiac reconstruction (ECR) framework, a new approach is presented for the heart-rate-adaptive gated helical cardiac cone-beam CT reconstruction. Reconstruction assessment criteria such as the temporal resolution, the homogeneity in terms of the cardiac phase, and the smoothness at cycle-to-cycle transitions are developed. Several reconstruction optimization approaches are described: An approach for the heart-rate-adaptive optimization of the temporal resolution is presented. Streak artifacts at cycle-to-cycle transitions can be minimized by using an improved cardiac weighting scheme. The optimal quiescent cardiac phase for the reconstruction can be determined automatically with the motion map technique. Results for all optimization procedures applied to ECR are presented and discussed based on patient and phantom data. The ECR algorithm is analyzed for larger detector arrays of future cone-beam systems throughout an extensive simulation study based on a four-dimensional cardiac CT phantom. The results of the scientific work are summarized and an outlook proposing future directions is given. The presented thesis is available for public download at www.cardiac-ct.net

  8. The noise power spectrum in CT with direct fan beam reconstruction

    International Nuclear Information System (INIS)

    Baek, Jongduk; Pelc, Norbert J.

    2010-01-01

    The noise power spectrum (NPS) is a useful metric for understanding the noise content in images. To examine some unique properties of the NPS of fan beam CT, the authors derived an analytical expression for the NPS of fan beam CT and validated it with computer simulations. The nonstationary noise behavior of fan beam CT was examined by analyzing local regions and the entire field-of-view (FOV). This was performed for cases with uniform as well as nonuniform noise across the detector cells and across views. The simulated NPS from the entire FOV and local regions showed good agreement with the analytically derived NPS. The analysis shows that whereas the NPS of a large FOV in parallel beam CT (using a ramp filter) is proportional to frequency, the NPS with direct fan beam FBP reconstruction shows a high frequency roll off. Even in small regions, the fan beam NPS can show a sharp transition (discontinuity) at high frequencies. These effects are due to the variable magnification and therefore are more pronounced as the fan angle increases. For cases with nonuniform noise, the NPS can show the directional dependence and additional effects.

  9. 3D dictionary learning based iterative cone beam CT reconstruction

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    Ti Bai

    2014-03-01

    Full Text Available Purpose: This work is to develop a 3D dictionary learning based cone beam CT (CBCT reconstruction algorithm on graphic processing units (GPU to improve the quality of sparse-view CBCT reconstruction with high efficiency. Methods: A 3D dictionary containing 256 small volumes (atoms of 3 × 3 × 3 was trained from a large number of blocks extracted from a high quality volume image. On the basis, we utilized cholesky decomposition based orthogonal matching pursuit algorithm to find the sparse representation of each block. To accelerate the time-consuming sparse coding in the 3D case, we implemented the sparse coding in a parallel fashion by taking advantage of the tremendous computational power of GPU. Conjugate gradient least square algorithm was adopted to minimize the data fidelity term. Evaluations are performed based on a head-neck patient case. FDK reconstruction with full dataset of 364 projections is used as the reference. We compared the proposed 3D dictionary learning based method with tight frame (TF by performing reconstructions on a subset data of 121 projections. Results: Compared to TF based CBCT reconstruction that shows good overall performance, our experiments indicated that 3D dictionary learning based CBCT reconstruction is able to recover finer structures, remove more streaking artifacts and also induce less blocky artifacts. Conclusion: 3D dictionary learning based CBCT reconstruction algorithm is able to sense the structural information while suppress the noise, and hence to achieve high quality reconstruction under the case of sparse view. The GPU realization of the whole algorithm offers a significant efficiency enhancement, making this algorithm more feasible for potential clinical application.-------------------------------Cite this article as: Bai T, Yan H, Shi F, Jia X, Lou Y, Xu Q, Jiang S, Mou X. 3D dictionary learning based iterative cone beam CT reconstruction. Int J Cancer Ther Oncol 2014; 2(2:020240. DOI: 10

  10. The Reconstruction Toolkit (RTK), an open-source cone-beam CT reconstruction toolkit based on the Insight Toolkit (ITK)

    International Nuclear Information System (INIS)

    Rit, S; Vila Oliva, M; Sarrut, D; Brousmiche, S; Labarbe, R; Sharp, G C

    2014-01-01

    We propose the Reconstruction Toolkit (RTK, http://www.openrtk.org), an open-source toolkit for fast cone-beam CT reconstruction, based on the Insight Toolkit (ITK) and using GPU code extracted from Plastimatch. RTK is developed by an open consortium (see affiliations) under the non-contaminating Apache 2.0 license. The quality of the platform is daily checked with regression tests in partnership with Kitware, the company supporting ITK. Several features are already available: Elekta, Varian and IBA inputs, multi-threaded Feldkamp-David-Kress reconstruction on CPU and GPU, Parker short scan weighting, multi-threaded CPU and GPU forward projectors, etc. Each feature is either accessible through command line tools or C++ classes that can be included in independent software. A MIDAS community has been opened to share CatPhan datasets of several vendors (Elekta, Varian and IBA). RTK will be used in the upcoming cone-beam CT scanner developed by IBA for proton therapy rooms. Many features are under development: new input format support, iterative reconstruction, hybrid Monte Carlo / deterministic CBCT simulation, etc. RTK has been built to freely share tomographic reconstruction developments between researchers and is open for new contributions.

  11. Reconstruction of a cone-beam CT image via forward iterative projection matching

    International Nuclear Information System (INIS)

    Brock, R. Scott; Docef, Alen; Murphy, Martin J.

    2010-01-01

    Purpose: To demonstrate the feasibility of reconstructing a cone-beam CT (CBCT) image by deformably altering a prior fan-beam CT (FBCT) image such that it matches the anatomy portrayed in the CBCT projection data set. Methods: A prior FBCT image of the patient is assumed to be available as a source image. A CBCT projection data set is obtained and used as a target image set. A parametrized deformation model is applied to the source FBCT image, digitally reconstructed radiographs (DRRs) that emulate the CBCT projection image geometry are calculated and compared to the target CBCT projection data, and the deformation model parameters are adjusted iteratively until the DRRs optimally match the CBCT projection data set. The resulting deformed FBCT image is hypothesized to be an accurate representation of the patient's anatomy imaged by the CBCT system. The process is demonstrated via numerical simulation. A known deformation is applied to a prior FBCT image and used to create a synthetic set of CBCT target projections. The iterative projection matching process is then applied to reconstruct the deformation represented in the synthetic target projections; the reconstructed deformation is then compared to the known deformation. The sensitivity of the process to the number of projections and the DRR/CBCT projection mismatch is explored by systematically adding noise to and perturbing the contrast of the target projections relative to the iterated source DRRs and by reducing the number of projections. Results: When there is no noise or contrast mismatch in the CBCT projection images, a set of 64 projections allows the known deformed CT image to be reconstructed to within a nRMS error of 1% and the known deformation to within a nRMS error of 7%. A CT image nRMS error of less than 4% is maintained at noise levels up to 3% of the mean projection intensity, at which the deformation error is 13%. At 1% noise level, the number of projections can be reduced to 8 while maintaining

  12. SU-D-206-03: Segmentation Assisted Fast Iterative Reconstruction Method for Cone-Beam CT

    International Nuclear Information System (INIS)

    Wu, P; Mao, T; Gong, S; Wang, J; Niu, T; Sheng, K; Xie, Y

    2016-01-01

    Purpose: Total Variation (TV) based iterative reconstruction (IR) methods enable accurate CT image reconstruction from low-dose measurements with sparse projection acquisition, due to the sparsifiable feature of most CT images using gradient operator. However, conventional solutions require large amount of iterations to generate a decent reconstructed image. One major reason is that the expected piecewise constant property is not taken into consideration at the optimization starting point. In this work, we propose an iterative reconstruction method for cone-beam CT (CBCT) using image segmentation to guide the optimization path more efficiently on the regularization term at the beginning of the optimization trajectory. Methods: Our method applies general knowledge that one tissue component in the CT image contains relatively uniform distribution of CT number. This general knowledge is incorporated into the proposed reconstruction using image segmentation technique to generate the piecewise constant template on the first-pass low-quality CT image reconstructed using analytical algorithm. The template image is applied as an initial value into the optimization process. Results: The proposed method is evaluated on the Shepp-Logan phantom of low and high noise levels, and a head patient. The number of iterations is reduced by overall 40%. Moreover, our proposed method tends to generate a smoother reconstructed image with the same TV value. Conclusion: We propose a computationally efficient iterative reconstruction method for CBCT imaging. Our method achieves a better optimization trajectory and a faster convergence behavior. It does not rely on prior information and can be readily incorporated into existing iterative reconstruction framework. Our method is thus practical and attractive as a general solution to CBCT iterative reconstruction. This work is supported by the Zhejiang Provincial Natural Science Foundation of China (Grant No. LR16F010001), National High-tech R

  13. SU-D-206-03: Segmentation Assisted Fast Iterative Reconstruction Method for Cone-Beam CT

    Energy Technology Data Exchange (ETDEWEB)

    Wu, P; Mao, T; Gong, S; Wang, J; Niu, T [Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, Institute of Translational Medicine, Zhejiang University, Hangzhou, Zhejiang (China); Sheng, K [Department of Radiation Oncology, University of California, Los Angeles, Los Angeles, CA (United States); Xie, Y [Institute of Biomedical and Health Engineering, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong (China)

    2016-06-15

    Purpose: Total Variation (TV) based iterative reconstruction (IR) methods enable accurate CT image reconstruction from low-dose measurements with sparse projection acquisition, due to the sparsifiable feature of most CT images using gradient operator. However, conventional solutions require large amount of iterations to generate a decent reconstructed image. One major reason is that the expected piecewise constant property is not taken into consideration at the optimization starting point. In this work, we propose an iterative reconstruction method for cone-beam CT (CBCT) using image segmentation to guide the optimization path more efficiently on the regularization term at the beginning of the optimization trajectory. Methods: Our method applies general knowledge that one tissue component in the CT image contains relatively uniform distribution of CT number. This general knowledge is incorporated into the proposed reconstruction using image segmentation technique to generate the piecewise constant template on the first-pass low-quality CT image reconstructed using analytical algorithm. The template image is applied as an initial value into the optimization process. Results: The proposed method is evaluated on the Shepp-Logan phantom of low and high noise levels, and a head patient. The number of iterations is reduced by overall 40%. Moreover, our proposed method tends to generate a smoother reconstructed image with the same TV value. Conclusion: We propose a computationally efficient iterative reconstruction method for CBCT imaging. Our method achieves a better optimization trajectory and a faster convergence behavior. It does not rely on prior information and can be readily incorporated into existing iterative reconstruction framework. Our method is thus practical and attractive as a general solution to CBCT iterative reconstruction. This work is supported by the Zhejiang Provincial Natural Science Foundation of China (Grant No. LR16F010001), National High-tech R

  14. The completeness condition and source orbits for exact image reconstruction in 3D cone-beam CT

    International Nuclear Information System (INIS)

    Mao Xiping; Kang Kejun

    1997-01-01

    The completeness condition for exact image reconstruction in 3D cone-beam CT are carefully analyzed in theory, and discussions about some source orbits which fulfill the completeness condition are followed

  15. Task-driven image acquisition and reconstruction in cone-beam CT

    International Nuclear Information System (INIS)

    Gang, Grace J; Stayman, J Webster; Siewerdsen, Jeffrey H; Ehtiati, Tina

    2015-01-01

    This work introduces a task-driven imaging framework that incorporates a mathematical definition of the imaging task, a model of the imaging system, and a patient-specific anatomical model to prospectively design image acquisition and reconstruction techniques to optimize task performance. The framework is applied to joint optimization of tube current modulation, view-dependent reconstruction kernel, and orbital tilt in cone-beam CT. The system model considers a cone-beam CT system incorporating a flat-panel detector and 3D filtered backprojection and accurately describes the spatially varying noise and resolution over a wide range of imaging parameters in the presence of a realistic anatomical model. Task-based detectability index (d′) is incorporated as the objective function in a task-driven optimization of image acquisition and reconstruction techniques. The orbital tilt was optimized through an exhaustive search across tilt angles ranging ±30°. For each tilt angle, the view-dependent tube current and reconstruction kernel (i.e. the modulation profiles) that maximized detectability were identified via an alternating optimization. The task-driven approach was compared with conventional unmodulated and automatic exposure control (AEC) strategies for a variety of imaging tasks and anthropomorphic phantoms. The task-driven strategy outperformed the unmodulated and AEC cases for all tasks. For example, d′ for a sphere detection task in a head phantom was improved by 30% compared to the unmodulated case by using smoother kernels for noisy views and distributing mAs across less noisy views (at fixed total mAs) in a manner that was beneficial to task performance. Similarly for detection of a line-pair pattern, the task-driven approach increased d′ by 80% compared to no modulation by means of view-dependent mA and kernel selection that yields modulation transfer function and noise-power spectrum optimal to the task. Optimization of orbital tilt identified the

  16. Single-slice rebinning method for helical cone-beam CT

    International Nuclear Information System (INIS)

    Noo, F.; Defrise, M.; Clackdoyle, R.

    1999-01-01

    In this paper, we present reconstruction results from helical cone-beam CT data, obtained using a simple and fast algorithm, which we call the CB-SSRB algorithm. This algorithm combines the single-slice rebinning method of PET imaging with the weighting schemes of spiral CT algorithms. The reconstruction is approximate but can be performed using 2D multislice fan-beam filtered backprojection. The quality of the results is surprisingly good, and far exceeds what one might expect, even when the pitch of the helix is large. In particular, with this algorithm comparable quality is obtained using helical cone-beam data with a normalized pitch of 10 to that obtained using standard spiral CT reconstruction with a normalized pitch of 2. (author)

  17. A technique for on-board CT reconstruction using both kilovoltage and megavoltage beam projections for 3D treatment verification

    International Nuclear Information System (INIS)

    Yin Fangfang; Guan Huaiqun; Lu Wenkai

    2005-01-01

    The technologies with kilovoltage (kV) and megavoltage (MV) imaging in the treatment room are now available for image-guided radiation therapy to improve patient setup and target localization accuracy. However, development of strategies to efficiently and effectively implement these technologies for patient treatment remains challenging. This study proposed an aggregated technique for on-board CT reconstruction using combination of kV and MV beam projections to improve the data acquisition efficiency and image quality. These projections were acquired in the treatment room at the patient treatment position with a new kV imaging device installed on the accelerator gantry, orthogonal to the existing MV portal imaging device. The projection images for a head phantom and a contrast phantom were acquired using both the On-Board Imager TM kV imaging device and the MV portal imager mounted orthogonally on the gantry of a Varian Clinac TM 21EX linear accelerator. MV projections were converted into kV information prior to the aggregated CT reconstruction. The multilevel scheme algebraic-reconstruction technique was used to reconstruct CT images involving either full, truncated, or a combination of both full and truncated projections. An adaptive reconstruction method was also applied, based on the limited numbers of kV projections and truncated MV projections, to enhance the anatomical information around the treatment volume and to minimize the radiation dose. The effects of the total number of projections, the combination of kV and MV projections, and the beam truncation of MV projections on the details of reconstructed kV/MV CT images were also investigated

  18. Three-dimensional focus of attention for iterative cone-beam micro-CT reconstruction

    International Nuclear Information System (INIS)

    Benson, T M; Gregor, J

    2006-01-01

    Three-dimensional iterative reconstruction of high-resolution, circular orbit cone-beam x-ray CT data is often considered impractical due to the demand for vast amounts of computer cycles and associated memory. In this paper, we show that the computational burden can be reduced by limiting the reconstruction to a small, well-defined portion of the image volume. We first discuss using the support region defined by the set of voxels covered by all of the projection views. We then present a data-driven preprocessing technique called focus of attention that heuristically separates both image and projection data into object and background before reconstruction, thereby further reducing the reconstruction region of interest. We present experimental results for both methods based on mouse data and a parallelized implementation of the SIRT algorithm. The computational savings associated with the support region are substantial. However, the results for focus of attention are even more impressive in that only about one quarter of the computer cycles and memory are needed compared with reconstruction of the entire image volume. The image quality is not compromised by either method

  19. GPU-based streaming architectures for fast cone-beam CT image reconstruction and demons deformable registration

    International Nuclear Information System (INIS)

    Sharp, G C; Kandasamy, N; Singh, H; Folkert, M

    2007-01-01

    This paper shows how to significantly accelerate cone-beam CT reconstruction and 3D deformable image registration using the stream-processing model. We describe data-parallel designs for the Feldkamp, Davis and Kress (FDK) reconstruction algorithm, and the demons deformable registration algorithm, suitable for use on a commodity graphics processing unit. The streaming versions of these algorithms are implemented using the Brook programming environment and executed on an NVidia 8800 GPU. Performance results using CT data of a preserved swine lung indicate that the GPU-based implementations of the FDK and demons algorithms achieve a substantial speedup-up to 80 times for FDK and 70 times for demons when compared to an optimized reference implementation on a 2.8 GHz Intel processor. In addition, the accuracy of the GPU-based implementations was found to be excellent. Compared with CPU-based implementations, the RMS differences were less than 0.1 Hounsfield unit for reconstruction and less than 0.1 mm for deformable registration

  20. Ultrafast and scalable cone-beam CT reconstruction using MapReduce in a cloud computing environment.

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    Meng, Bowen; Pratx, Guillem; Xing, Lei

    2011-12-01

    Four-dimensional CT (4DCT) and cone beam CT (CBCT) are widely used in radiation therapy for accurate tumor target definition and localization. However, high-resolution and dynamic image reconstruction is computationally demanding because of the large amount of data processed. Efficient use of these imaging techniques in the clinic requires high-performance computing. The purpose of this work is to develop a novel ultrafast, scalable and reliable image reconstruction technique for 4D CBCT∕CT using a parallel computing framework called MapReduce. We show the utility of MapReduce for solving large-scale medical physics problems in a cloud computing environment. In this work, we accelerated the Feldcamp-Davis-Kress (FDK) algorithm by porting it to Hadoop, an open-source MapReduce implementation. Gated phases from a 4DCT scans were reconstructed independently. Following the MapReduce formalism, Map functions were used to filter and backproject subsets of projections, and Reduce function to aggregate those partial backprojection into the whole volume. MapReduce automatically parallelized the reconstruction process on a large cluster of computer nodes. As a validation, reconstruction of a digital phantom and an acquired CatPhan 600 phantom was performed on a commercial cloud computing environment using the proposed 4D CBCT∕CT reconstruction algorithm. Speedup of reconstruction time is found to be roughly linear with the number of nodes employed. For instance, greater than 10 times speedup was achieved using 200 nodes for all cases, compared to the same code executed on a single machine. Without modifying the code, faster reconstruction is readily achievable by allocating more nodes in the cloud computing environment. Root mean square error between the images obtained using MapReduce and a single-threaded reference implementation was on the order of 10(-7). Our study also proved that cloud computing with MapReduce is fault tolerant: the reconstruction completed

  1. A new approximate algorithm for image reconstruction in cone-beam spiral CT at small cone-angles

    International Nuclear Information System (INIS)

    Schaller, S.; Flohr, T.; Steffen, P.

    1996-01-01

    This paper presents a new approximate algorithm for image reconstruction with cone-beam spiral CT data at relatively small cone-angles. Based on the algorithm of Wang et al., our method combines a special complementary interpolation with filtered backprojection. The presented algorithm has three main advantages over Wang's algorithm: (1) It overcomes the pitch limitation of Wang's algorithm. (2) It significantly improves z-resolution when suitable sampling schemes are applied. (3) It avoids the waste of applied radiation dose inherent to Wang's algorithm. Usage of the total applied dose is an important requirement in medical imaging. Our method has been implemented on a standard workstation. Reconstructions of computer-simulated data of different phantoms, assuming sampling conditions and image quality requirements typical to medical CT, show encouraging results

  2. Algorithms of CT value correction for reconstructing a radiotherapy simulation image through axial CT images

    International Nuclear Information System (INIS)

    Ogino, Takashi; Egawa, Sunao

    1991-01-01

    New algorithms of CT value correction for reconstructing a radiotherapy simulation image through axial CT images were developed. One, designated plane weighting method, is to correct CT value in proportion to the position of the beam element passing through the voxel. The other, designated solid weighting method, is to correct CT value in proportion to the length of the beam element passing through the voxel and the volume of voxel. Phantom experiments showed fair spatial resolution in the transverse direction. In the longitudinal direction, however, spatial resolution of under slice thickness could not be obtained. Contrast resolution was equivalent for both methods. In patient studies, the reconstructed radiotherapy simulation image was almost similar in visual perception of the density resolution to a simulation film taken by X-ray simulator. (author)

  3. 3D algebraic iterative reconstruction for cone-beam x-ray differential phase-contrast computed tomography.

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    Fu, Jian; Hu, Xinhua; Velroyen, Astrid; Bech, Martin; Jiang, Ming; Pfeiffer, Franz

    2015-01-01

    Due to the potential of compact imaging systems with magnified spatial resolution and contrast, cone-beam x-ray differential phase-contrast computed tomography (DPC-CT) has attracted significant interest. The current proposed FDK reconstruction algorithm with the Hilbert imaginary filter will induce severe cone-beam artifacts when the cone-beam angle becomes large. In this paper, we propose an algebraic iterative reconstruction (AIR) method for cone-beam DPC-CT and report its experiment results. This approach considers the reconstruction process as the optimization of a discrete representation of the object function to satisfy a system of equations that describes the cone-beam DPC-CT imaging modality. Unlike the conventional iterative algorithms for absorption-based CT, it involves the derivative operation to the forward projections of the reconstructed intermediate image to take into account the differential nature of the DPC projections. This method is based on the algebraic reconstruction technique, reconstructs the image ray by ray, and is expected to provide better derivative estimates in iterations. This work comprises a numerical study of the algorithm and its experimental verification using a dataset measured with a three-grating interferometer and a mini-focus x-ray tube source. It is shown that the proposed method can reduce the cone-beam artifacts and performs better than FDK under large cone-beam angles. This algorithm is of interest for future cone-beam DPC-CT applications.

  4. Development of a cone-beam CT system for radiological technologist education

    International Nuclear Information System (INIS)

    Teramoto, Atsushi; Ohara, Ken; Ozaki, Kaho; Miyashita, Mariko; Ohno, Tomoyuki; Tsuzaka, Masatoshi; Fujita, Hiroshi

    2011-01-01

    For radiological technologists, it is very important to understand the principle of computed tomography (CT) and CT artifacts derived from mechanical and electrical failure. In this study, a CT system for educating radiological technologists was developed. The system consisted of a cone-beam CT scanner and educational software. The cone-beam CT scanner has a simple structure, using a micro-focus X-ray tube and an indirect-conversion flat panel detector. For the educational software, we developed various educational functions of image reconstruction and reconstruction parameters as well as CT artifacts. In the experiments, the capabilities of the system were evaluated using an acrylic phantom. We verified that the system produced the expected results. (author)

  5. Parameter selection in limited data cone-beam CT reconstruction using edge-preserving total variation algorithms

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    Lohvithee, Manasavee; Biguri, Ander; Soleimani, Manuchehr

    2017-12-01

    There are a number of powerful total variation (TV) regularization methods that have great promise in limited data cone-beam CT reconstruction with an enhancement of image quality. These promising TV methods require careful selection of the image reconstruction parameters, for which there are no well-established criteria. This paper presents a comprehensive evaluation of parameter selection in a number of major TV-based reconstruction algorithms. An appropriate way of selecting the values for each individual parameter has been suggested. Finally, a new adaptive-weighted projection-controlled steepest descent (AwPCSD) algorithm is presented, which implements the edge-preserving function for CBCT reconstruction with limited data. The proposed algorithm shows significant robustness compared to three other existing algorithms: ASD-POCS, AwASD-POCS and PCSD. The proposed AwPCSD algorithm is able to preserve the edges of the reconstructed images better with fewer sensitive parameters to tune.

  6. General surface reconstruction for cone-beam multislice spiral computed tomography

    International Nuclear Information System (INIS)

    Chen Laigao; Liang Yun; Heuscher, Dominic J.

    2003-01-01

    A new family of cone-beam reconstruction algorithm, the General Surface Reconstruction (GSR), is proposed and formulated in this paper for multislice spiral computed tomography (CT) reconstructions. It provides a general framework to allow the reconstruction of planar or nonplanar surfaces on a set of rebinned short-scan parallel beam projection data. An iterative surface formation method is proposed as an example to show the possibility to form nonplanar reconstruction surfaces to minimize the adverse effect between the collected cone-beam projection data and the reconstruction surfaces. The improvement in accuracy of the nonplanar surfaces over planar surfaces in the two-dimensional approximate cone-beam reconstructions is mathematically proved and demonstrated using numerical simulations. The proposed GSR algorithm is evaluated by the computer simulation of cone-beam spiral scanning geometry and various mathematical phantoms. The results demonstrate that the GSR algorithm generates much better image quality compared to conventional multislice reconstruction algorithms. For a table speed up to 100 mm per rotation, GSR demonstrates good image quality for both the low-contrast ball phantom and thorax phantom. All other performance parameters are comparable to the single-slice 180 deg. LI (linear interpolation) algorithm, which is considered the 'gold standard'. GSR also achieves high computing efficiency and good temporal resolution, making it an attractive alternative for the reconstruction of next generation multislice spiral CT data

  7. An Approximate Cone Beam Reconstruction Algorithm for Gantry-Tilted CT Using Tangential Filtering

    Directory of Open Access Journals (Sweden)

    Ming Yan

    2006-01-01

    Full Text Available FDK algorithm is a well-known 3D (three-dimensional approximate algorithm for CT (computed tomography image reconstruction and is also known to suffer from considerable artifacts when the scanning cone angle is large. Recently, it has been improved by performing the ramp filtering along the tangential direction of the X-ray source helix for dealing with the large cone angle problem. In this paper, we present an FDK-type approximate reconstruction algorithm for gantry-tilted CT imaging. The proposed method improves the image reconstruction by filtering the projection data along a proper direction which is determined by CT parameters and gantry-tilted angle. As a result, the proposed algorithm for gantry-tilted CT reconstruction can provide more scanning flexibilities in clinical CT scanning and is efficient in computation. The performance of the proposed algorithm is evaluated with turbell clock phantom and thorax phantom and compared with FDK algorithm and a popular 2D (two-dimensional approximate algorithm. The results show that the proposed algorithm can achieve better image quality for gantry-tilted CT image reconstruction.

  8. An analytical simulation technique for cone-beam CT and pinhole SPECT

    International Nuclear Information System (INIS)

    Zhang Xuezhu; Qi Yujin

    2011-01-01

    This study was aimed at developing an efficient simulation technique with an ordinary PC. The work involved derivation of mathematical operators, analytic phantom generations, and effective analytical projectors developing for cone-beam CT and pinhole SPECT imaging. The computer simulations based on the analytical projectors were developed by ray-tracing method for cone-beam CT and voxel-driven method for pinhole SPECT of degrading blurring. The 3D Shepp-Logan, Jaszczak and Defrise phantoms were used for simulation evaluations and image reconstructions. The reconstructed phantom images were of good accuracy with the phantoms. The results showed that the analytical simulation technique is an efficient tool for studying cone-beam CT and pinhole SPECT imaging. (authors)

  9. A theoretically exact reconstruction algorithm for helical cone-beam differential phase-contrast computed tomography

    International Nuclear Information System (INIS)

    Li Jing; Sun Yi; Zhu Peiping

    2013-01-01

    Differential phase-contrast computed tomography (DPC-CT) reconstruction problems are usually solved by using parallel-, fan- or cone-beam algorithms. For rod-shaped objects, the x-ray beams cannot recover all the slices of the sample at the same time. Thus, if a rod-shaped sample is required to be reconstructed by the above algorithms, one should alternately perform translation and rotation on this sample, which leads to lower efficiency. The helical cone-beam CT may significantly improve scanning efficiency for rod-shaped objects over other algorithms. In this paper, we propose a theoretically exact filter-backprojection algorithm for helical cone-beam DPC-CT, which can be applied to reconstruct the refractive index decrement distribution of the samples directly from two-dimensional differential phase-contrast images. Numerical simulations are conducted to verify the proposed algorithm. Our work provides a potential solution for inspecting the rod-shaped samples using DPC-CT, which may be applicable with the evolution of DPC-CT equipments. (paper)

  10. A hybrid reconstruction algorithm for fast and accurate 4D cone-beam CT imaging.

    Science.gov (United States)

    Yan, Hao; Zhen, Xin; Folkerts, Michael; Li, Yongbao; Pan, Tinsu; Cervino, Laura; Jiang, Steve B; Jia, Xun

    2014-07-01

    4D cone beam CT (4D-CBCT) has been utilized in radiation therapy to provide 4D image guidance in lung and upper abdomen area. However, clinical application of 4D-CBCT is currently limited due to the long scan time and low image quality. The purpose of this paper is to develop a new 4D-CBCT reconstruction method that restores volumetric images based on the 1-min scan data acquired with a standard 3D-CBCT protocol. The model optimizes a deformation vector field that deforms a patient-specific planning CT (p-CT), so that the calculated 4D-CBCT projections match measurements. A forward-backward splitting (FBS) method is invented to solve the optimization problem. It splits the original problem into two well-studied subproblems, i.e., image reconstruction and deformable image registration. By iteratively solving the two subproblems, FBS gradually yields correct deformation information, while maintaining high image quality. The whole workflow is implemented on a graphic-processing-unit to improve efficiency. Comprehensive evaluations have been conducted on a moving phantom and three real patient cases regarding the accuracy and quality of the reconstructed images, as well as the algorithm robustness and efficiency. The proposed algorithm reconstructs 4D-CBCT images from highly under-sampled projection data acquired with 1-min scans. Regarding the anatomical structure location accuracy, 0.204 mm average differences and 0.484 mm maximum difference are found for the phantom case, and the maximum differences of 0.3-0.5 mm for patients 1-3 are observed. As for the image quality, intensity errors below 5 and 20 HU compared to the planning CT are achieved for the phantom and the patient cases, respectively. Signal-noise-ratio values are improved by 12.74 and 5.12 times compared to results from FDK algorithm using the 1-min data and 4-min data, respectively. The computation time of the algorithm on a NVIDIA GTX590 card is 1-1.5 min per phase. High-quality 4D-CBCT imaging based

  11. A hybrid reconstruction algorithm for fast and accurate 4D cone-beam CT imaging

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Hao; Folkerts, Michael; Jiang, Steve B., E-mail: xun.jia@utsouthwestern.edu, E-mail: steve.jiang@UTSouthwestern.edu; Jia, Xun, E-mail: xun.jia@utsouthwestern.edu, E-mail: steve.jiang@UTSouthwestern.edu [Department of Radiation Oncology, The University of Texas, Southwestern Medical Center, Dallas, Texas 75390 (United States); Zhen, Xin [Department of Biomedical Engineering, Southern Medical University, Guangzhou, Guangdong 510515 (China); Li, Yongbao [Department of Radiation Oncology, The University of Texas, Southwestern Medical Center, Dallas, Texas 75390 and Department of Engineering Physics, Tsinghua University, Beijing 100084 (China); Pan, Tinsu [Department of Imaging Physics, The University of Texas, MD Anderson Cancer Center, Houston, Texas 77030 (United States); Cervino, Laura [Department of Radiation Medicine and Applied Sciences, University of California San Diego, La Jolla, California 92093 (United States)

    2014-07-15

    Purpose: 4D cone beam CT (4D-CBCT) has been utilized in radiation therapy to provide 4D image guidance in lung and upper abdomen area. However, clinical application of 4D-CBCT is currently limited due to the long scan time and low image quality. The purpose of this paper is to develop a new 4D-CBCT reconstruction method that restores volumetric images based on the 1-min scan data acquired with a standard 3D-CBCT protocol. Methods: The model optimizes a deformation vector field that deforms a patient-specific planning CT (p-CT), so that the calculated 4D-CBCT projections match measurements. A forward-backward splitting (FBS) method is invented to solve the optimization problem. It splits the original problem into two well-studied subproblems, i.e., image reconstruction and deformable image registration. By iteratively solving the two subproblems, FBS gradually yields correct deformation information, while maintaining high image quality. The whole workflow is implemented on a graphic-processing-unit to improve efficiency. Comprehensive evaluations have been conducted on a moving phantom and three real patient cases regarding the accuracy and quality of the reconstructed images, as well as the algorithm robustness and efficiency. Results: The proposed algorithm reconstructs 4D-CBCT images from highly under-sampled projection data acquired with 1-min scans. Regarding the anatomical structure location accuracy, 0.204 mm average differences and 0.484 mm maximum difference are found for the phantom case, and the maximum differences of 0.3–0.5 mm for patients 1–3 are observed. As for the image quality, intensity errors below 5 and 20 HU compared to the planning CT are achieved for the phantom and the patient cases, respectively. Signal-noise-ratio values are improved by 12.74 and 5.12 times compared to results from FDK algorithm using the 1-min data and 4-min data, respectively. The computation time of the algorithm on a NVIDIA GTX590 card is 1–1.5 min per phase

  12. Implementation techniques and acceleration of DBPF reconstruction algorithm based on GPGPU for helical cone beam CT

    International Nuclear Information System (INIS)

    Shen Le; Xing Yuxiang

    2010-01-01

    The derivative back-projection filtered algorithm for a helical cone-beam CT is a newly developed exact reconstruction method. Due to its large computational complexity, the reconstruction is rather slow for practical use. General purpose graphic processing unit (GPGPU) is an SIMD paralleled hardware architecture with powerful float-point operation capacity. In this paper,we propose a new method for PI-line choice and sampling grid, and a paralleled PI-line reconstruction algorithm implemented on NVIDIA's Compute Unified Device Architecture (CUDA). Numerical simulation studies are carried out to validate our method. Compared with conventional CPU implementation, the CUDA accelerated method provides images of the same quality with a speedup factor of 318. Optimization strategies for the GPU acceleration are presented. Finally, influence of the parameters of the PI-line samples on the reconstruction speed and image quality is discussed. (authors)

  13. Advanced single-slice rebinning for tilted spiral cone-beam CT

    International Nuclear Information System (INIS)

    Kachelriess, Marc; Fuchs, Theo; Schaller, Stefan; Kalender, Willi A.

    2001-01-01

    Future medical CT scanners and today's micro CT scanners demand cone-beam reconstruction algorithms that are capable of reconstructing data acquired from a tilted spiral trajectory where the vector of rotation is not necessarily parallel to the vector of table increment. For the medical CT scanner this case of nonparallel object motion is met for nonzero gantry tilt: the table moves into a direction that is not perpendicular to the plane of rotation. Since this is not a special application of medical CT but rather a daily routine in head exams, there is a strong need for corresponding reconstruction algorithms. In contrast to medical CT, where the special case of nonperpendicular motion is used on purpose, micro CT scanners cannot avoid aberrations of the rotational axis and the table increment vector due to alignment problems. Especially for those micro CT scanners that have the lifting stage mounted on the rotation table (in contrast to setups where the lifting stage holds the rotation table), this kind of misalignment is equivalent to a gantry tilt. We therefore generalize the advanced single-slice rebinning algorithm (ASSR), which is considered a very promising approach for medical cone-beam reconstruction due to its high image quality and its high reconstruction speed [Med. Phys. 27, 754-772 (2000)], to the case of tilted gantries. We evaluate this extended ASSR approach (which we will denote as ASSR + , for convenience) in comparison to the original ASSR algorithm using simulated phantom data for reconstruction. For the case of nonparallel object motion ASSR + shows significant improvements over ASSR, however, its computational complexity is slightly increased due to the broken symmetry of the spiral trajectory

  14. Parallel statistical image reconstruction for cone-beam x-ray CT on a shared memory computation platform

    International Nuclear Information System (INIS)

    Kole, J S; Beekman, F J

    2005-01-01

    Statistical reconstruction methods offer possibilities of improving image quality as compared to analytical methods, but current reconstruction times prohibit routine clinical applications. To reduce reconstruction times we have parallelized a statistical reconstruction algorithm for cone-beam x-ray CT, the ordered subset convex algorithm (OSC), and evaluated it on a shared memory computer. Two different parallelization strategies were developed: one that employs parallelism by computing the work for all projections within a subset in parallel, and one that divides the total volume into parts and processes the work for each sub-volume in parallel. Both methods are used to reconstruct a three-dimensional mathematical phantom on two different grid densities. The reconstructed images are binary identical to the result of the serial (non-parallelized) algorithm. The speed-up factor equals approximately 30 when using 32 to 40 processors, and scales almost linearly with the number of cpus for both methods. The huge reduction in computation time allows us to apply statistical reconstruction to clinically relevant studies for the first time

  15. WE-AB-207A-08: BEST IN PHYSICS (IMAGING): Advanced Scatter Correction and Iterative Reconstruction for Improved Cone-Beam CT Imaging On the TrueBeam Radiotherapy Machine

    Energy Technology Data Exchange (ETDEWEB)

    Wang, A; Paysan, P; Brehm, M; Maslowski, A; Lehmann, M; Messmer, P; Munro, P; Yoon, S; Star-Lack, J; Seghers, D [Varian Medical Systems, Palo Alto, CA (United States)

    2016-06-15

    Purpose: To improve CBCT image quality for image-guided radiotherapy by applying advanced reconstruction algorithms to overcome scatter, noise, and artifact limitations Methods: CBCT is used extensively for patient setup in radiotherapy. However, image quality generally falls short of diagnostic CT, limiting soft-tissue based positioning and potential applications such as adaptive radiotherapy. The conventional TrueBeam CBCT reconstructor uses a basic scatter correction and FDK reconstruction, resulting in residual scatter artifacts, suboptimal image noise characteristics, and other artifacts like cone-beam artifacts. We have developed an advanced scatter correction that uses a finite-element solver (AcurosCTS) to model the behavior of photons as they pass (and scatter) through the object. Furthermore, iterative reconstruction is applied to the scatter-corrected projections, enforcing data consistency with statistical weighting and applying an edge-preserving image regularizer to reduce image noise. The combined algorithms have been implemented on a GPU. CBCT projections from clinically operating TrueBeam systems have been used to compare image quality between the conventional and improved reconstruction methods. Planning CT images of the same patients have also been compared. Results: The advanced scatter correction removes shading and inhomogeneity artifacts, reducing the scatter artifact from 99.5 HU to 13.7 HU in a typical pelvis case. Iterative reconstruction provides further benefit by reducing image noise and eliminating streak artifacts, thereby improving soft-tissue visualization. In a clinical head and pelvis CBCT, the noise was reduced by 43% and 48%, respectively, with no change in spatial resolution (assessed visually). Additional benefits include reduction of cone-beam artifacts and reduction of metal artifacts due to intrinsic downweighting of corrupted rays. Conclusion: The combination of an advanced scatter correction with iterative reconstruction

  16. Radiation dose reduction in medical x-ray CT via Fourier-based iterative reconstruction.

    Science.gov (United States)

    Fahimian, Benjamin P; Zhao, Yunzhe; Huang, Zhifeng; Fung, Russell; Mao, Yu; Zhu, Chun; Khatonabadi, Maryam; DeMarco, John J; Osher, Stanley J; McNitt-Gray, Michael F; Miao, Jianwei

    2013-03-01

    A Fourier-based iterative reconstruction technique, termed Equally Sloped Tomography (EST), is developed in conjunction with advanced mathematical regularization to investigate radiation dose reduction in x-ray CT. The method is experimentally implemented on fan-beam CT and evaluated as a function of imaging dose on a series of image quality phantoms and anonymous pediatric patient data sets. Numerical simulation experiments are also performed to explore the extension of EST to helical cone-beam geometry. EST is a Fourier based iterative algorithm, which iterates back and forth between real and Fourier space utilizing the algebraically exact pseudopolar fast Fourier transform (PPFFT). In each iteration, physical constraints and mathematical regularization are applied in real space, while the measured data are enforced in Fourier space. The algorithm is automatically terminated when a proposed termination criterion is met. Experimentally, fan-beam projections were acquired by the Siemens z-flying focal spot technology, and subsequently interleaved and rebinned to a pseudopolar grid. Image quality phantoms were scanned at systematically varied mAs settings, reconstructed by EST and conventional reconstruction methods such as filtered back projection (FBP), and quantified using metrics including resolution, signal-to-noise ratios (SNRs), and contrast-to-noise ratios (CNRs). Pediatric data sets were reconstructed at their original acquisition settings and additionally simulated to lower dose settings for comparison and evaluation of the potential for radiation dose reduction. Numerical experiments were conducted to quantify EST and other iterative methods in terms of image quality and computation time. The extension of EST to helical cone-beam CT was implemented by using the advanced single-slice rebinning (ASSR) method. Based on the phantom and pediatric patient fan-beam CT data, it is demonstrated that EST reconstructions with the lowest scanner flux setting of 39 m

  17. Radiation dose reduction in medical x-ray CT via Fourier-based iterative reconstruction

    International Nuclear Information System (INIS)

    Fahimian, Benjamin P.; Zhao Yunzhe; Huang Zhifeng; Fung, Russell; Zhu Chun; Miao Jianwei; Mao Yu; Khatonabadi, Maryam; DeMarco, John J.; McNitt-Gray, Michael F.; Osher, Stanley J.

    2013-01-01

    Purpose: A Fourier-based iterative reconstruction technique, termed Equally Sloped Tomography (EST), is developed in conjunction with advanced mathematical regularization to investigate radiation dose reduction in x-ray CT. The method is experimentally implemented on fan-beam CT and evaluated as a function of imaging dose on a series of image quality phantoms and anonymous pediatric patient data sets. Numerical simulation experiments are also performed to explore the extension of EST to helical cone-beam geometry. Methods: EST is a Fourier based iterative algorithm, which iterates back and forth between real and Fourier space utilizing the algebraically exact pseudopolar fast Fourier transform (PPFFT). In each iteration, physical constraints and mathematical regularization are applied in real space, while the measured data are enforced in Fourier space. The algorithm is automatically terminated when a proposed termination criterion is met. Experimentally, fan-beam projections were acquired by the Siemens z-flying focal spot technology, and subsequently interleaved and rebinned to a pseudopolar grid. Image quality phantoms were scanned at systematically varied mAs settings, reconstructed by EST and conventional reconstruction methods such as filtered back projection (FBP), and quantified using metrics including resolution, signal-to-noise ratios (SNRs), and contrast-to-noise ratios (CNRs). Pediatric data sets were reconstructed at their original acquisition settings and additionally simulated to lower dose settings for comparison and evaluation of the potential for radiation dose reduction. Numerical experiments were conducted to quantify EST and other iterative methods in terms of image quality and computation time. The extension of EST to helical cone-beam CT was implemented by using the advanced single-slice rebinning (ASSR) method. Results: Based on the phantom and pediatric patient fan-beam CT data, it is demonstrated that EST reconstructions with the lowest

  18. Tilted cone-beam reconstruction with row-wise fan-to-parallel rebinning

    International Nuclear Information System (INIS)

    Hsieh Jiang; Tang Xiangyang

    2006-01-01

    Reconstruction algorithms for cone-beam CT have been the focus of many studies. Several exact and approximate reconstruction algorithms were proposed for step-and-shoot and helical scanning trajectories to combat cone-beam related artefacts. In this paper, we present a new closed-form cone-beam reconstruction formula for tilted gantry data acquisition. Although several algorithms were proposed in the past to combat errors induced by the gantry tilt, none of the algorithms addresses the scenario in which the cone-beam geometry is first rebinned to a set of parallel beams prior to the filtered backprojection. We show that the image quality advantages of the rebinned parallel-beam reconstruction are significant, which makes the development of such an algorithm necessary. Because of the rebinning process, the reconstruction algorithm becomes more complex and the amount of iso-centre adjustment depends not only on the projection and tilt angles, but also on the reconstructed pixel location. In this paper, we first demonstrate the advantages of the row-wise fan-to-parallel rebinning and derive a closed-form solution for the reconstruction algorithm for the step-and-shoot and constant-pitch helical scans. The proposed algorithm requires the 'warping' of the reconstruction matrix on a view-by-view basis prior to the backprojection step. We further extend the algorithm to the variable-pitch helical scans in which the patient table travels at non-constant speeds. The algorithm was tested extensively on both the 16- and 64-slice CT scanners. The efficacy of the algorithm is clearly demonstrated by multiple experiments

  19. A three-dimensional-weighted cone beam filtered backprojection (CB-FBP) algorithm for image reconstruction in volumetric CT-helical scanning

    International Nuclear Information System (INIS)

    Tang Xiangyang; Hsieh Jiang; Nilsen, Roy A; Dutta, Sandeep; Samsonov, Dmitry; Hagiwara, Akira

    2006-01-01

    Based on the structure of the original helical FDK algorithm, a three-dimensional (3D)-weighted cone beam filtered backprojection (CB-FBP) algorithm is proposed for image reconstruction in volumetric CT under helical source trajectory. In addition to its dependence on view and fan angles, the 3D weighting utilizes the cone angle dependency of a ray to improve reconstruction accuracy. The 3D weighting is ray-dependent and the underlying mechanism is to give a favourable weight to the ray with the smaller cone angle out of a pair of conjugate rays but an unfavourable weight to the ray with the larger cone angle out of the conjugate ray pair. The proposed 3D-weighted helical CB-FBP reconstruction algorithm is implemented in the cone-parallel geometry that can improve noise uniformity and image generation speed significantly. Under the cone-parallel geometry, the filtering is naturally carried out along the tangential direction of the helical source trajectory. By exploring the 3D weighting's dependence on cone angle, the proposed helical 3D-weighted CB-FBP reconstruction algorithm can provide significantly improved reconstruction accuracy at moderate cone angle and high helical pitches. The 3D-weighted CB-FBP algorithm is experimentally evaluated by computer-simulated phantoms and phantoms scanned by a diagnostic volumetric CT system with a detector dimension of 64 x 0.625 mm over various helical pitches. The computer simulation study shows that the 3D weighting enables the proposed algorithm to reach reconstruction accuracy comparable to that of exact CB reconstruction algorithms, such as the Katsevich algorithm, under a moderate cone angle (4 deg.) and various helical pitches. Meanwhile, the experimental evaluation using the phantoms scanned by a volumetric CT system shows that the spatial resolution along the z-direction and noise characteristics of the proposed 3D-weighted helical CB-FBP reconstruction algorithm are maintained very well in comparison to the FDK

  20. Image reconstruction from multiple fan-beam projections

    International Nuclear Information System (INIS)

    Jelinek, J.; Overton, T.R.

    1984-01-01

    Special-purpose third-generation fan-beam CT systems can be greatly simplified by limiting the number of detectors, but this requires a different mode of data collection to provide a set of projections appropriate to the required spatial resolution in the reconstructed image. Repeated rotation of the source-detector fan, combined with shift of the detector array and perhaps offset of the source with respect to the fan's axis after each 360 0 rotation(cycle), provides a fairly general pattern of projection space filling. The authors' investigated the problem of optimal data-collection geometry for a multiple-rotation fan-beam scanner and of corresponding reconstruction algorithm

  1. Soft-tissue imaging with C-arm cone-beam CT using statistical reconstruction

    International Nuclear Information System (INIS)

    Wang, Adam S; Stayman, J Webster; Otake, Yoshito; Siewerdsen, Jeffrey H; Kleinszig, Gerhard; Vogt, Sebastian; Gallia, Gary L; Khanna, A Jay

    2014-01-01

    The potential for statistical image reconstruction methods such as penalized-likelihood (PL) to improve C-arm cone-beam CT (CBCT) soft-tissue visualization for intraoperative imaging over conventional filtered backprojection (FBP) is assessed in this work by making a fair comparison in relation to soft-tissue performance. A prototype mobile C-arm was used to scan anthropomorphic head and abdomen phantoms as well as a cadaveric torso at doses substantially lower than typical values in diagnostic CT, and the effects of dose reduction via tube current reduction and sparse sampling were also compared. Matched spatial resolution between PL and FBP was determined by the edge spread function of low-contrast (∼40–80 HU) spheres in the phantoms, which were representative of soft-tissue imaging tasks. PL using the non-quadratic Huber penalty was found to substantially reduce noise relative to FBP, especially at lower spatial resolution where PL provides a contrast-to-noise ratio increase up to 1.4–2.2× over FBP at 50% dose reduction across all objects. Comparison of sampling strategies indicates that soft-tissue imaging benefits from fully sampled acquisitions at dose above ∼1.7 mGy and benefits from 50% sparsity at dose below ∼1.0 mGy. Therefore, an appropriate sampling strategy along with the improved low-contrast visualization offered by statistical reconstruction demonstrates the potential for extending intraoperative C-arm CBCT to applications in soft-tissue interventions in neurosurgery as well as thoracic and abdominal surgeries by overcoming conventional tradeoffs in noise, spatial resolution, and dose. (paper)

  2. A local region of interest image reconstruction via filtered backprojection for fan-beam differential phase-contrast computed tomography

    International Nuclear Information System (INIS)

    Qi Zhihua; Chen Guanghong

    2007-01-01

    Recently, x-ray differential phase contrast computed tomography (DPC-CT) has been experimentally implemented using a conventional source combined with several gratings. Images were reconstructed using a parallel-beam reconstruction formula. However, parallel-beam reconstruction formulae are not directly applicable for a large image object where the parallel-beam approximation fails. In this note, we present a new image reconstruction formula for fan-beam DPC-CT. There are two major features in this algorithm: (1) it enables the reconstruction of a local region of interest (ROI) using data acquired from an angular interval shorter than 180 0 + fan angle and (2) it still preserves the filtered backprojection structure. Numerical simulations have been conducted to validate the image reconstruction algorithm. (note)

  3. Segmentation-free empirical beam hardening correction for CT

    Energy Technology Data Exchange (ETDEWEB)

    Schüller, Sören; Sawall, Stefan [German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, Heidelberg 69120 (Germany); Stannigel, Kai; Hülsbusch, Markus; Ulrici, Johannes; Hell, Erich [Sirona Dental Systems GmbH, Fabrikstraße 31, 64625 Bensheim (Germany); Kachelrieß, Marc, E-mail: marc.kachelriess@dkfz.de [German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, 69120 Heidelberg (Germany)

    2015-02-15

    Purpose: The polychromatic nature of the x-ray beams and their effects on the reconstructed image are often disregarded during standard image reconstruction. This leads to cupping and beam hardening artifacts inside the reconstructed volume. To correct for a general cupping, methods like water precorrection exist. They correct the hardening of the spectrum during the penetration of the measured object only for the major tissue class. In contrast, more complex artifacts like streaks between dense objects need other techniques of correction. If using only the information of one single energy scan, there are two types of corrections. The first one is a physical approach. Thereby, artifacts can be reproduced and corrected within the original reconstruction by using assumptions in a polychromatic forward projector. These assumptions could be the used spectrum, the detector response, the physical attenuation and scatter properties of the intersected materials. A second method is an empirical approach, which does not rely on much prior knowledge. This so-called empirical beam hardening correction (EBHC) and the previously mentioned physical-based technique are both relying on a segmentation of the present tissues inside the patient. The difficulty thereby is that beam hardening by itself, scatter, and other effects, which diminish the image quality also disturb the correct tissue classification and thereby reduce the accuracy of the two known classes of correction techniques. The herein proposed method works similar to the empirical beam hardening correction but does not require a tissue segmentation and therefore shows improvements on image data, which are highly degraded by noise and artifacts. Furthermore, the new algorithm is designed in a way that no additional calibration or parameter fitting is needed. Methods: To overcome the segmentation of tissues, the authors propose a histogram deformation of their primary reconstructed CT image. This step is essential for the

  4. Segmentation-free empirical beam hardening correction for CT.

    Science.gov (United States)

    Schüller, Sören; Sawall, Stefan; Stannigel, Kai; Hülsbusch, Markus; Ulrici, Johannes; Hell, Erich; Kachelrieß, Marc

    2015-02-01

    The polychromatic nature of the x-ray beams and their effects on the reconstructed image are often disregarded during standard image reconstruction. This leads to cupping and beam hardening artifacts inside the reconstructed volume. To correct for a general cupping, methods like water precorrection exist. They correct the hardening of the spectrum during the penetration of the measured object only for the major tissue class. In contrast, more complex artifacts like streaks between dense objects need other techniques of correction. If using only the information of one single energy scan, there are two types of corrections. The first one is a physical approach. Thereby, artifacts can be reproduced and corrected within the original reconstruction by using assumptions in a polychromatic forward projector. These assumptions could be the used spectrum, the detector response, the physical attenuation and scatter properties of the intersected materials. A second method is an empirical approach, which does not rely on much prior knowledge. This so-called empirical beam hardening correction (EBHC) and the previously mentioned physical-based technique are both relying on a segmentation of the present tissues inside the patient. The difficulty thereby is that beam hardening by itself, scatter, and other effects, which diminish the image quality also disturb the correct tissue classification and thereby reduce the accuracy of the two known classes of correction techniques. The herein proposed method works similar to the empirical beam hardening correction but does not require a tissue segmentation and therefore shows improvements on image data, which are highly degraded by noise and artifacts. Furthermore, the new algorithm is designed in a way that no additional calibration or parameter fitting is needed. To overcome the segmentation of tissues, the authors propose a histogram deformation of their primary reconstructed CT image. This step is essential for the proposed

  5. High-speed fan-beam reconstruction using direct two-dimensional Fourier transform method

    International Nuclear Information System (INIS)

    Niki, Noboru; Mizutani, Toshio; Takahashi, Yoshizo; Inouye, Tamon.

    1984-01-01

    Since the first development of X-ray computer tomography (CT), various efforts have been made to obtain high quality of high-speed image. However, the development of high resolution CT and the ultra-high speed CT to be applied to hearts is still desired. The X-ray beam scanning method was already changed from the parallel beam system to the fan-beam system in order to greatly shorten the scanning time. Also, the filtered back projection (DFBP) method has been employed to directly processing fan-beam projection data as reconstruction method. Although the two-dimensional Fourier transform (TFT) method significantly faster than FBP method was proposed, it has not been sufficiently examined for fan-beam projection data. Thus, the ITFT method was investigated, which first executes rebinning algorithm to convert the fan-beam projection data to the parallel beam projection data, thereafter, uses two-dimensional Fourier transform. By this method, although high speed is expected, the reconstructed images might be degraded due to the adoption of rebinning algorithm. Therefore, the effect of the interpolation error of rebinning algorithm on the reconstructed images has been analyzed theoretically, and finally, the result of the employment of spline interpolation which allows the acquisition of high quality images with less errors has been shown by the numerical and visual evaluation based on simulation and actual data. Computation time was reduced to 1/15 for the image matrix of 512 and to 1/30 for doubled matrix. (Wakatsuki, Y.)

  6. Accelerated Compressed Sensing Based CT Image Reconstruction.

    Science.gov (United States)

    Hashemi, SayedMasoud; Beheshti, Soosan; Gill, Patrick R; Paul, Narinder S; Cobbold, Richard S C

    2015-01-01

    In X-ray computed tomography (CT) an important objective is to reduce the radiation dose without significantly degrading the image quality. Compressed sensing (CS) enables the radiation dose to be reduced by producing diagnostic images from a limited number of projections. However, conventional CS-based algorithms are computationally intensive and time-consuming. We propose a new algorithm that accelerates the CS-based reconstruction by using a fast pseudopolar Fourier based Radon transform and rebinning the diverging fan beams to parallel beams. The reconstruction process is analyzed using a maximum-a-posterior approach, which is transformed into a weighted CS problem. The weights involved in the proposed model are calculated based on the statistical characteristics of the reconstruction process, which is formulated in terms of the measurement noise and rebinning interpolation error. Therefore, the proposed method not only accelerates the reconstruction, but also removes the rebinning and interpolation errors. Simulation results are shown for phantoms and a patient. For example, a 512 × 512 Shepp-Logan phantom when reconstructed from 128 rebinned projections using a conventional CS method had 10% error, whereas with the proposed method the reconstruction error was less than 1%. Moreover, computation times of less than 30 sec were obtained using a standard desktop computer without numerical optimization.

  7. Accelerated Compressed Sensing Based CT Image Reconstruction

    Directory of Open Access Journals (Sweden)

    SayedMasoud Hashemi

    2015-01-01

    Full Text Available In X-ray computed tomography (CT an important objective is to reduce the radiation dose without significantly degrading the image quality. Compressed sensing (CS enables the radiation dose to be reduced by producing diagnostic images from a limited number of projections. However, conventional CS-based algorithms are computationally intensive and time-consuming. We propose a new algorithm that accelerates the CS-based reconstruction by using a fast pseudopolar Fourier based Radon transform and rebinning the diverging fan beams to parallel beams. The reconstruction process is analyzed using a maximum-a-posterior approach, which is transformed into a weighted CS problem. The weights involved in the proposed model are calculated based on the statistical characteristics of the reconstruction process, which is formulated in terms of the measurement noise and rebinning interpolation error. Therefore, the proposed method not only accelerates the reconstruction, but also removes the rebinning and interpolation errors. Simulation results are shown for phantoms and a patient. For example, a 512 × 512 Shepp-Logan phantom when reconstructed from 128 rebinned projections using a conventional CS method had 10% error, whereas with the proposed method the reconstruction error was less than 1%. Moreover, computation times of less than 30 sec were obtained using a standard desktop computer without numerical optimization.

  8. Scatter correction, intermediate view estimation and dose characterization in megavoltage cone-beam CT imaging

    Science.gov (United States)

    Sramek, Benjamin Koerner

    The ability to deliver conformal dose distributions in radiation therapy through intensity modulation and the potential for tumor dose escalation to improve treatment outcome has necessitated an increase in localization accuracy of inter- and intra-fractional patient geometry. Megavoltage cone-beam CT imaging using the treatment beam and onboard electronic portal imaging device is one option currently being studied for implementation in image-guided radiation therapy. However, routine clinical use is predicated upon continued improvements in image quality and patient dose delivered during acquisition. The formal statement of hypothesis for this investigation was that the conformity of planned to delivered dose distributions in image-guided radiation therapy could be further enhanced through the application of kilovoltage scatter correction and intermediate view estimation techniques to megavoltage cone-beam CT imaging, and that normalized dose measurements could be acquired and inter-compared between multiple imaging geometries. The specific aims of this investigation were to: (1) incorporate the Feldkamp, Davis and Kress filtered backprojection algorithm into a program to reconstruct a voxelized linear attenuation coefficient dataset from a set of acquired megavoltage cone-beam CT projections, (2) characterize the effects on megavoltage cone-beam CT image quality resulting from the application of Intermediate View Interpolation and Intermediate View Reprojection techniques to limited-projection datasets, (3) incorporate the Scatter and Primary Estimation from Collimator Shadows (SPECS) algorithm into megavoltage cone-beam CT image reconstruction and determine the set of SPECS parameters which maximize image quality and quantitative accuracy, and (4) evaluate the normalized axial dose distributions received during megavoltage cone-beam CT image acquisition using radiochromic film and thermoluminescent dosimeter measurements in anthropomorphic pelvic and head and

  9. Partial volume and aliasing artefacts in helical cone-beam CT

    International Nuclear Information System (INIS)

    Zou Yu; Sidky, Emil Y; Pan, Xiaochuan

    2004-01-01

    A generalization of the quasi-exact algorithms of Kudo et al (2000 IEEE Trans. Med. Imaging 19 902-21) is developed that allows for data acquisition in a 'practical' frame for clinical diagnostic helical, cone-beam computed tomography (CT). The algorithm is investigated using data that model nonlinear partial volume averaging. This investigation leads to an understanding of aliasing artefacts in helical, cone-beam CT image reconstruction. An ad hoc scheme is proposed to mitigate artefacts due to the nonlinear partial volume and aliasing artefacts

  10. Image quality in thoracic 4D cone-beam CT: A sensitivity analysis of respiratory signal, binning method, reconstruction algorithm, and projection angular spacing

    OpenAIRE

    Shieh, Chun-Chien; Kipritidis, John; O’Brien, Ricky T.; Kuncic, Zdenka; Keall, Paul J.

    2014-01-01

    Purpose: Respiratory signal, binning method, and reconstruction algorithm are three major controllable factors affecting image quality in thoracic 4D cone-beam CT (4D-CBCT), which is widely used in image guided radiotherapy (IGRT). Previous studies have investigated each of these factors individually, but no integrated sensitivity analysis has been performed. In addition, projection angular spacing is also a key factor in reconstruction, but how it affects image quality is not obvious. An inv...

  11. A BPF-FBP tandem algorithm for image reconstruction in reverse helical cone-beam CT

    International Nuclear Information System (INIS)

    Cho, Seungryong; Xia, Dan; Pellizzari, Charles A.; Pan Xiaochuan

    2010-01-01

    Purpose: Reverse helical cone-beam computed tomography (CBCT) is a scanning configuration for potential applications in image-guided radiation therapy in which an accurate anatomic image of the patient is needed for image-guidance procedures. The authors previously developed an algorithm for image reconstruction from nontruncated data of an object that is completely within the reverse helix. The purpose of this work is to develop an image reconstruction approach for reverse helical CBCT of a long object that extends out of the reverse helix and therefore constitutes data truncation. Methods: The proposed approach comprises of two reconstruction steps. In the first step, a chord-based backprojection-filtration (BPF) algorithm reconstructs a volumetric image of an object from the original cone-beam data. Because there exists a chordless region in the middle of the reverse helix, the image obtained in the first step contains an unreconstructed central-gap region. In the second step, the gap region is reconstructed by use of a Pack-Noo-formula-based filteredbackprojection (FBP) algorithm from the modified cone-beam data obtained by subtracting from the original cone-beam data the reprojection of the image reconstructed in the first step. Results: The authors have performed numerical studies to validate the proposed approach in image reconstruction from reverse helical cone-beam data. The results confirm that the proposed approach can reconstruct accurate images of a long object without suffering from data-truncation artifacts or cone-angle artifacts. Conclusions: They developed and validated a BPF-FBP tandem algorithm to reconstruct images of a long object from reverse helical cone-beam data. The chord-based BPF algorithm was utilized for converting the long-object problem into a short-object problem. The proposed approach is applicable to other scanning configurations such as reduced circular sinusoidal trajectories.

  12. SU-G-206-16: Investigation of Dosimetric Consequence Via Cone-Beam CT Based Dose Reconstruction in Hepatocellular Carcinoma Radiotherapy

    Energy Technology Data Exchange (ETDEWEB)

    Huang, P; Gang, Y; Qin, S; Li, D [Shandong Province Key Laboratory of Medical Physics and Image Processing Technology, School of Physics and Electronics, Shandong Normal University (China); Li, H; Chen, J; Ma, C; Yin, Y [Department of Radiation Oncology, Shandong Cancer Hospital and Institute (China)

    2016-06-15

    Purpose: Many patients with technically unresectable or medically inoperable hepatocellular carcinoma (HCC) had hepatic dosimetric variations as a result of inter-fraction anatomical deformation. This study was conducted to assess the hepatic dosimetric consequences via reconstructing weekly dose in HCC patients receiving three dimensional conformal radiation therapy. Methods: Twenty-one HCC patients with 21 planning CT (pCT) scans and 63 weekly Cone-beam CT (CBCT) scans were enrolled in this investigation. Among them, six patients had been diagnosed of radiation induced liver disease (RILD) and the other fifteen patients had good prognosis after treatment. And each patient had three weekly CBCT before re-planning. In reconstructing CBCT-based weekly dose, we registered pCT to CBCT to provide the correct Hounsfield units for the CBCT using gradient-based deformable image registration (DIR), and this modified CBCT (mCBCT) were introduced to enable dose calculation.To obtain the weekly dosimetric consequences, the initial plan beam configurations and dose constraints were re-applied to mCBCT for performing dose calculation, and the mCBCT were extrapolated to 25 fractions. Besides, the manually delineated contour was propagated automatically onto the mCBCT of the new patient by exploiting the deformation vectors field, and the reconstructed weekly dose was mapped back to pCT to understand the dose distribution difference. Also, weekly dosimetric variations were compared with the hepatic radiation tolerance in terms of D50 and Dmean. Results: Among the twenty-one patients, the three weekly D50 increased by 0.7Gy, 5.1Gy and 6.1Gy, respectively, and Dmean increased by 0.9%, 4.7% and 5.5%, respectively. For patients with RILD, the average values of the third weekly D50 and Dmean were both high than hepatic radiation tolerance, while the values of patients without RILD were below. Conclusion: The planned dose on pCT was not a real dose to the liver, and the liver overdose

  13. An efficient polyenergetic SART (pSART) reconstruction algorithm for quantitative myocardial CT perfusion

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Yuan, E-mail: yuan.lin@duke.edu; Samei, Ehsan [Carl E. Ravin Advanced Imaging Laboratories, Duke University Medical Center, 2424 Erwin Road, Suite 302, Durham, North Carolina 27705 (United States)

    2014-02-15

    Purpose: In quantitative myocardial CT perfusion imaging, beam hardening effect due to dense bone and high concentration iodinated contrast agent can result in visible artifacts and inaccurate CT numbers. In this paper, an efficient polyenergetic Simultaneous Algebraic Reconstruction Technique (pSART) was presented to eliminate the beam hardening artifacts and to improve the CT quantitative imaging ability. Methods: Our algorithm made threea priori assumptions: (1) the human body is composed of several base materials (e.g., fat, breast, soft tissue, bone, and iodine); (2) images can be coarsely segmented to two types of regions, i.e., nonbone regions and noniodine regions; and (3) each voxel can be decomposed into a mixture of two most suitable base materials according to its attenuation value and its corresponding region type information. Based on the above assumptions, energy-independent accumulated effective lengths of all base materials can be fast computed in the forward ray-tracing process and be used repeatedly to obtain accurate polyenergetic projections, with which a SART-based equation can correctly update each voxel in the backward projecting process to iteratively reconstruct artifact-free images. This approach effectively reduces the influence of polyenergetic x-ray sources and it further enables monoenergetic images to be reconstructed at any arbitrarily preselected target energies. A series of simulation tests were performed on a size-variable cylindrical phantom and a realistic anthropomorphic thorax phantom. In addition, a phantom experiment was also performed on a clinical CT scanner to further quantitatively validate the proposed algorithm. Results: The simulations with the cylindrical phantom and the anthropomorphic thorax phantom showed that the proposed algorithm completely eliminated beam hardening artifacts and enabled quantitative imaging across different materials, phantom sizes, and spectra, as the absolute relative errors were reduced

  14. An efficient polyenergetic SART (pSART) reconstruction algorithm for quantitative myocardial CT perfusion

    International Nuclear Information System (INIS)

    Lin, Yuan; Samei, Ehsan

    2014-01-01

    Purpose: In quantitative myocardial CT perfusion imaging, beam hardening effect due to dense bone and high concentration iodinated contrast agent can result in visible artifacts and inaccurate CT numbers. In this paper, an efficient polyenergetic Simultaneous Algebraic Reconstruction Technique (pSART) was presented to eliminate the beam hardening artifacts and to improve the CT quantitative imaging ability. Methods: Our algorithm made threea priori assumptions: (1) the human body is composed of several base materials (e.g., fat, breast, soft tissue, bone, and iodine); (2) images can be coarsely segmented to two types of regions, i.e., nonbone regions and noniodine regions; and (3) each voxel can be decomposed into a mixture of two most suitable base materials according to its attenuation value and its corresponding region type information. Based on the above assumptions, energy-independent accumulated effective lengths of all base materials can be fast computed in the forward ray-tracing process and be used repeatedly to obtain accurate polyenergetic projections, with which a SART-based equation can correctly update each voxel in the backward projecting process to iteratively reconstruct artifact-free images. This approach effectively reduces the influence of polyenergetic x-ray sources and it further enables monoenergetic images to be reconstructed at any arbitrarily preselected target energies. A series of simulation tests were performed on a size-variable cylindrical phantom and a realistic anthropomorphic thorax phantom. In addition, a phantom experiment was also performed on a clinical CT scanner to further quantitatively validate the proposed algorithm. Results: The simulations with the cylindrical phantom and the anthropomorphic thorax phantom showed that the proposed algorithm completely eliminated beam hardening artifacts and enabled quantitative imaging across different materials, phantom sizes, and spectra, as the absolute relative errors were reduced

  15. SU-E-T-143: Effect of X-Ray and Cone Beam CT Reconstruction Parameters On Estimation of Bone Volume of Mice Used in Aging Research

    Energy Technology Data Exchange (ETDEWEB)

    Russ, M; Pang, M; Troen, B; Rudin, S; Ionita, C [University at Buffalo, Buffalo, NY (United States)

    2014-06-01

    Purpose: To investigate the variations in bone volume calculations in mice involved in aging research when changing cone beam micro-CT x-ray and reconstruction parameters. Methods: Mouse spines were placed on an indexed turn table that rotated 0.5° per projection and imaged by a self-built micro CT machine containing a CCD-based high-resolution x-ray detector. After the full 360° rotation data set of object images was obtained, a standard filtered back-projection cone beam reconstruction was performed. Four different kVp's between 40–70 kVp in 10kVp increments were selected. For each kVp two mAs settings were used. Each acquisition was reconstructed using two voxel sizes (12 and 25μm) and two step angles, 0.5° and 1°, respectively. A LabView program was written to determine the total bone volume contained in the mouse's total spine volume (bone plus gaps) as a measure of spine health. First, the user selected the desired 512×512 reconstruction to view the whole spine volume which was then used to select a gray-level threshold that allowed for viewing of the bone structure, then another threshold to include gaps. The program returned bone volume, bone × gap volume, and their ratio, BVF. Results: The calculated bone volume fractions were compared as a function of tube potential. Cases with 25μm slice thickness showed trials with lower kVp's had greater image contrast, which resulted in higher calculated bone volume fractions. Cases with 12μm reconstructed slice thickness were significantly noisier, and showed no clear maximum BVF. Conclusion: Using the projection images and reconstructions acquired from the micro CT, it can be shown that the micro-CT x-ray and reconstruction parameters significantly affect the total bone volume calculations. When comparing mice cohorts treated with different therapies researchers need to be aware of such details and use volumes which were acquired and processed in identical conditions.

  16. NUFFT-Based Iterative Image Reconstruction via Alternating Direction Total Variation Minimization for Sparse-View CT

    Directory of Open Access Journals (Sweden)

    Bin Yan

    2015-01-01

    Full Text Available Sparse-view imaging is a promising scanning method which can reduce the radiation dose in X-ray computed tomography (CT. Reconstruction algorithm for sparse-view imaging system is of significant importance. The adoption of the spatial iterative algorithm for CT image reconstruction has a low operation efficiency and high computation requirement. A novel Fourier-based iterative reconstruction technique that utilizes nonuniform fast Fourier transform is presented in this study along with the advanced total variation (TV regularization for sparse-view CT. Combined with the alternating direction method, the proposed approach shows excellent efficiency and rapid convergence property. Numerical simulations and real data experiments are performed on a parallel beam CT. Experimental results validate that the proposed method has higher computational efficiency and better reconstruction quality than the conventional algorithms, such as simultaneous algebraic reconstruction technique using TV method and the alternating direction total variation minimization approach, with the same time duration. The proposed method appears to have extensive applications in X-ray CT imaging.

  17. A reconstruction method for cone-beam differential x-ray phase-contrast computed tomography.

    Science.gov (United States)

    Fu, Jian; Velroyen, Astrid; Tan, Renbo; Zhang, Junwei; Chen, Liyuan; Tapfer, Arne; Bech, Martin; Pfeiffer, Franz

    2012-09-10

    Most existing differential phase-contrast computed tomography (DPC-CT) approaches are based on three kinds of scanning geometries, described by parallel-beam, fan-beam and cone-beam. Due to the potential of compact imaging systems with magnified spatial resolution, cone-beam DPC-CT has attracted significant interest. In this paper, we report a reconstruction method based on a back-projection filtration (BPF) algorithm for cone-beam DPC-CT. Due to the differential nature of phase contrast projections, the algorithm restrains from differentiation of the projection data prior to back-projection, unlike BPF algorithms commonly used for absorption-based CT data. This work comprises a numerical study of the algorithm and its experimental verification using a dataset measured with a three-grating interferometer and a micro-focus x-ray tube source. Moreover, the numerical simulation and experimental results demonstrate that the proposed method can deal with several classes of truncated cone-beam datasets. We believe that this feature is of particular interest for future medical cone-beam phase-contrast CT imaging applications.

  18. A characteristic of angiographic cone-beam CT

    International Nuclear Information System (INIS)

    Takase, Tadashi; Take, Toshio; Nakazawa, Yasuo; Kinouchi, Katsunori

    2009-01-01

    Angiographic cone-beam CT, called DynaCT by SIEMENS, is a 3D imaging tool reconstructed from projection data by a rotational C-arm with a flat panel detector. It can visualize low-contrast objects such as soft tissue or small vessels as well as high-contrast structures such as enhanced vessels or bone. We need to understand its image characteristics and dose distribution during 200 degree rotation around a patient. In this research, we evaluated fundamental characteristics and dose effectiveness for optimized clinical images. DynaCT, including soft tissue information and isochronal voxel data along the z-axis, could provide enough CT-like image quality for interventional radiology (IVR) use. In addition, evaluation of accumulated dose distribution helped us to predict and avoid the occurrence of radiodermatitis. Thus, DynaCT is useful as a support and navigation tool for IVR. (author)

  19. Characterization of CT beams using Compton spectrometry; Caracterização de feixes de TC utilizando Espectrometria Compton

    Energy Technology Data Exchange (ETDEWEB)

    Terini, Ricardo A.; Nerssissian, Denise Y.; Campelo, Maria Carolina S.; Yoshimura, Elisabeth M., E-mail: rterini@if.usp.br [Universidade de São Paulo (LDRFM/USP), SP (Brazil). Lab. de Dosimetria das Radiações e Física Médica

    2017-07-01

    Obtaining the energy spectra of computed tomography (CT) X-ray beams is essential, helping to obtain parameters that characterize beam quality and equipment performance. However, CT photon fluxes are too high to have the spectra measured directly with common photon counting detectors. In this work, a Compton spectrometer was designed, with Al-Pb-Al collimators and shields, as well as a cadmium telluride (CdTe) detector to get the spectrum of CT beams, from the measurement of the spectrum of a beam scattered at 90 deg by a polymethyl-methacrylate (PMMA) rod. A MatLab® computer code was developed, using the Waller-Hartree formalism, to reconstruct the spectrum of the incident beam, from the measured scattered beam spectrum. Tests at IF-USP Laboratory of Radiation Dosimetry and Medical Physics with standard CT beams showed that the reconstructed spectrum is alike the directly measured beam. Shielding influence and scatterer thickness were investigated. The system was tested in measurements on a GE 690 CT scanner, showing practical positioning on the exam table, and alignment with CT lasers refined by scan projection radiography. Spectra obtained with the properly shielded system presented values of half-value layer (HVL) compatible with those measured in QC tests and kVp values with accuracy to evaluate the scanner voltage calibration. (author)

  20. Projection matrix acquisition for cone-beam computed tomography iterative reconstruction

    Science.gov (United States)

    Yang, Fuqiang; Zhang, Dinghua; Huang, Kuidong; Shi, Wenlong; Zhang, Caixin; Gao, Zongzhao

    2017-02-01

    Projection matrix is an essential and time-consuming part in computed tomography (CT) iterative reconstruction. In this article a novel calculation algorithm of three-dimensional (3D) projection matrix is proposed to quickly acquire the matrix for cone-beam CT (CBCT). The CT data needed to be reconstructed is considered as consisting of the three orthogonal sets of equally spaced and parallel planes, rather than the individual voxels. After getting the intersections the rays with the surfaces of the voxels, the coordinate points and vertex is compared to obtain the index value that the ray traversed. Without considering ray-slope to voxel, it just need comparing the position of two points. Finally, the computer simulation is used to verify the effectiveness of the algorithm.

  1. SU-F-J-23: Field-Of-View Expansion in Cone-Beam CT Reconstruction by Use of Prior Information

    Energy Technology Data Exchange (ETDEWEB)

    Haga, A; Magome, T; Nakano, M; Nakagawa, K [University of Tokyo Hospital, Tokyo (Japan); Kotoku, J [Teikyo University, Tokyo (Japan)

    2016-06-15

    Purpose: Cone-beam CT (CBCT) has become an integral part of online patient setup in an image-guided radiation therapy (IGRT). In addition, the utility of CBCT for dose calculation has actively been investigated. However, the limited size of field-of-view (FOV) and resulted CBCT image with a lack of peripheral area of patient body prevents the reliability of dose calculation. In this study, we aim to develop an FOV expanded CBCT in IGRT system to allow the dose calculation. Methods: Three lung cancer patients were selected in this study. We collected the cone-beam projection images in the CBCT-based IGRT system (X-ray volume imaging unit, ELEKTA), where FOV size of the provided CBCT with these projections was 410 × 410 mm{sup 2} (normal FOV). Using these projections, CBCT with a size of 728 × 728 mm{sup 2} was reconstructed by a posteriori estimation algorithm including a prior image constrained compressed sensing (PICCS). The treatment planning CT was used as a prior image. To assess the effectiveness of FOV expansion, a dose calculation was performed on the expanded CBCT image with region-of-interest (ROI) density mapping method, and it was compared with that of treatment planning CT as well as that of CBCT reconstructed by filtered back projection (FBP) algorithm. Results: A posteriori estimation algorithm with PICCS clearly visualized an area outside normal FOV, whereas the FBP algorithm yielded severe streak artifacts outside normal FOV due to under-sampling. The dose calculation result using the expanded CBCT agreed with that using treatment planning CT very well; a maximum dose difference was 1.3% for gross tumor volumes. Conclusion: With a posteriori estimation algorithm, FOV in CBCT can be expanded. Dose comparison results suggested that the use of expanded CBCTs is acceptable for dose calculation in adaptive radiation therapy. This study has been supported by KAKENHI (15K08691).

  2. Identification of dental root canals and their medial line from micro-CT and cone-beam CT records

    Directory of Open Access Journals (Sweden)

    Benyó Balázs

    2012-10-01

    Full Text Available Abstract Background Shape of the dental root canal is highly patient specific. Automated identification methods of the medial line of dental root canals and the reproduction of their 3D shape can be beneficial for planning endodontic interventions as severely curved root canals or multi-rooted teeth may pose treatment challenges. Accurate shape information of the root canals may also be used by manufacturers of endodontic instruments in order to make more efficient clinical tools. Method Novel image processing procedures dedicated to the automated detection of the medial axis of the root canal from dental micro-CT and cone-beam CT records are developed. For micro-CT, the 3D model of the root canal is built up from several hundred parallel cross sections, using image enhancement, histogram based fuzzy c-means clustering, center point detection in the segmented slice, three dimensional inner surface reconstruction, and potential field driven curve skeleton extraction in three dimensions. Cone-beam CT records are processed with image enhancement filters and fuzzy chain based regional segmentation, followed by the reconstruction of the root canal surface and detecting its skeleton via a mesh contraction algorithm. Results The proposed medial line identification and root canal detection algorithms are validated on clinical data sets. 25 micro-CT and 36 cone-beam-CT records are used in the validation procedure. The overall success rate of the automatic dental root canal identification was about 92% in both procedures. The algorithms proved to be accurate enough for endodontic therapy planning. Conclusions Accurate medial line identification and shape detection algorithms of dental root canal have been developed. Different procedures are defined for micro-CT and cone-beam CT records. The automated execution of the subsequent processing steps allows easy application of the algorithms in the dental care. The output data of the image processing procedures

  3. GPU accelerated CT reconstruction for clinical use: quality driven performance

    Science.gov (United States)

    Vaz, Michael S.; Sneyders, Yuri; McLin, Matthew; Ricker, Alan; Kimpe, Tom

    2007-03-01

    We present performance and quality analysis of GPU accelerated FDK filtered backprojection for cone beam computed tomography (CBCT) reconstruction. Our implementation of the FDK CT reconstruction algorithm does not compromise fidelity at any stage and yields a result that is within 1 HU of a reference C++ implementation. Our streaming implementation is able to perform reconstruction as the images are acquired; it addresses low latency as well as fast throughput, which are key considerations for a "real-time" design. Further, it is scaleable to multiple GPUs for increased performance. The implementation does not place any constraints on image acquisition; it works effectively for arbitrary angular coverage with arbitrary angular spacing. As such, this GPU accelerated CT reconstruction solution may easily be used with scanners that are already deployed. We are able to reconstruct a 512 x 512 x 340 volume from 625 projections, each sized 1024 x 768, in less than 50 seconds. The quoted 50 second timing encompasses the entire reconstruction using bilinear interpolation and includes filtering on the CPU, uploading the filtered projections to the GPU, and also downloading the reconstructed volume from GPU memory to system RAM.

  4. Truncation artifact suppression in cone-beam radionuclide transmission CT using maximum likelihood techniques: evaluation with human subjects

    International Nuclear Information System (INIS)

    Manglos, S.H.

    1992-01-01

    Transverse image truncation can be a serious problem for human imaging using cone-beam transmission CT (CB-CT) implemented on a conventional rotating gamma camera. This paper presents a reconstruction method to reduce or eliminate the artifacts resulting from the truncation. The method uses a previously published transmission maximum likelihood EM algorithm, adapted to the cone-beam geometry. The reconstruction method is evaluated qualitatively using three human subjects of various dimensions and various degrees of truncation. (author)

  5. A new cone-beam X-ray CT system with a reduced size planar detector

    International Nuclear Information System (INIS)

    Li Liang; Chen Zhiqiang; Zhang Li; Xing Yuxiang; Kang Kejun

    2006-01-01

    In a traditional cone-beam CT system, the cost of product and computation is very high. The authors propose a transversely truncated cone-beam X-ray CT system with a reduced size detector positioned off-center, in which X-ray beams only cover half of the object. The reduced detector size cuts the cost and the X-ray dose of the CT system. The existing CT reconstruction algorithms are not directly applicable in this new CT system. Hence, the authors develop a BPF-type direct backprojection algorithm. Different from the traditional rebinding methods, our algorithm directly backprojects the pretreated projection data without rebinding. This makes the algorithm compact and computationally more efficient. Finally, some numerical simulations and practical experiments are done to validate the proposed algorithm. (authors)

  6. Cone-beam local reconstruction based on a Radon inversion transformation

    International Nuclear Information System (INIS)

    Wang Xian-Chao; Yan Bin; Li Lei; Hu Guo-En

    2012-01-01

    The local reconstruction from truncated projection data is one area of interest in image reconstruction for computed tomography (CT), which creates the possibility for dose reduction. In this paper, a filtered-backprojection (FBP) algorithm based on the Radon inversion transform is presented to deal with the three-dimensional (3D) local reconstruction in the circular geometry. The algorithm achieves the data filtering in two steps. The first step is the derivative of projections, which acts locally on the data and can thus be carried out accurately even in the presence of data truncation. The second step is the nonlocal Hilbert filtering. The numerical simulations and the real data reconstructions have been conducted to validate the new reconstruction algorithm. Compared with the approximate truncation resistant algorithm for computed tomography (ATRACT), not only it has a comparable ability to restrain truncation artifacts, but also its reconstruction efficiency is improved. It is about twice as fast as that of the ATRACT. Therefore, this work provides a simple and efficient approach for the approximate reconstruction from truncated projections in the circular cone-beam CT

  7. Regularization design for high-quality cone-beam CT of intracranial hemorrhage using statistical reconstruction

    Science.gov (United States)

    Dang, H.; Stayman, J. W.; Xu, J.; Sisniega, A.; Zbijewski, W.; Wang, X.; Foos, D. H.; Aygun, N.; Koliatsos, V. E.; Siewerdsen, J. H.

    2016-03-01

    Intracranial hemorrhage (ICH) is associated with pathologies such as hemorrhagic stroke and traumatic brain injury. Multi-detector CT is the current front-line imaging modality for detecting ICH (fresh blood contrast 40-80 HU, down to 1 mm). Flat-panel detector (FPD) cone-beam CT (CBCT) offers a potential alternative with a smaller scanner footprint, greater portability, and lower cost potentially well suited to deployment at the point of care outside standard diagnostic radiology and emergency room settings. Previous studies have suggested reliable detection of ICH down to 3 mm in CBCT using high-fidelity artifact correction and penalized weighted least-squared (PWLS) image reconstruction with a post-artifact-correction noise model. However, ICH reconstructed by traditional image regularization exhibits nonuniform spatial resolution and noise due to interaction between the statistical weights and regularization, which potentially degrades the detectability of ICH. In this work, we propose three regularization methods designed to overcome these challenges. The first two compute spatially varying certainty for uniform spatial resolution and noise, respectively. The third computes spatially varying regularization strength to achieve uniform "detectability," combining both spatial resolution and noise in a manner analogous to a delta-function detection task. Experiments were conducted on a CBCT test-bench, and image quality was evaluated for simulated ICH in different regions of an anthropomorphic head. The first two methods improved the uniformity in spatial resolution and noise compared to traditional regularization. The third exhibited the highest uniformity in detectability among all methods and best overall image quality. The proposed regularization provides a valuable means to achieve uniform image quality in CBCT of ICH and is being incorporated in a CBCT prototype for ICH imaging.

  8. Statistical reconstruction for cone-beam CT with a post-artifact-correction noise model: application to high-quality head imaging

    International Nuclear Information System (INIS)

    Dang, H; Stayman, J W; Sisniega, A; Xu, J; Zbijewski, W; Siewerdsen, J H; Wang, X; Foos, D H; Aygun, N; Koliatsos, V E

    2015-01-01

    Non-contrast CT reliably detects fresh blood in the brain and is the current front-line imaging modality for intracranial hemorrhage such as that occurring in acute traumatic brain injury (contrast ∼40–80 HU, size  >  1 mm). We are developing flat-panel detector (FPD) cone-beam CT (CBCT) to facilitate such diagnosis in a low-cost, mobile platform suitable for point-of-care deployment. Such a system may offer benefits in the ICU, urgent care/concussion clinic, ambulance, and sports and military theatres. However, current FPD-CBCT systems face significant challenges that confound low-contrast, soft-tissue imaging. Artifact correction can overcome major sources of bias in FPD-CBCT but imparts noise amplification in filtered backprojection (FBP). Model-based reconstruction improves soft-tissue image quality compared to FBP by leveraging a high-fidelity forward model and image regularization. In this work, we develop a novel penalized weighted least-squares (PWLS) image reconstruction method with a noise model that includes accurate modeling of the noise characteristics associated with the two dominant artifact corrections (scatter and beam-hardening) in CBCT and utilizes modified weights to compensate for noise amplification imparted by each correction. Experiments included real data acquired on a FPD-CBCT test-bench and an anthropomorphic head phantom emulating intra-parenchymal hemorrhage. The proposed PWLS method demonstrated superior noise-resolution tradeoffs in comparison to FBP and PWLS with conventional weights (viz. at matched 0.50 mm spatial resolution, CNR = 11.9 compared to CNR = 5.6 and CNR = 9.9, respectively) and substantially reduced image noise especially in challenging regions such as skull base. The results support the hypothesis that with high-fidelity artifact correction and statistical reconstruction using an accurate post-artifact-correction noise model, FPD-CBCT can achieve image quality allowing reliable detection of

  9. Task-based statistical image reconstruction for high-quality cone-beam CT

    Science.gov (United States)

    Dang, Hao; Webster Stayman, J.; Xu, Jennifer; Zbijewski, Wojciech; Sisniega, Alejandro; Mow, Michael; Wang, Xiaohui; Foos, David H.; Aygun, Nafi; Koliatsos, Vassilis E.; Siewerdsen, Jeffrey H.

    2017-11-01

    Task-based analysis of medical imaging performance underlies many ongoing efforts in the development of new imaging systems. In statistical image reconstruction, regularization is often formulated in terms to encourage smoothness and/or sharpness (e.g. a linear, quadratic, or Huber penalty) but without explicit formulation of the task. We propose an alternative regularization approach in which a spatially varying penalty is determined that maximizes task-based imaging performance at every location in a 3D image. We apply the method to model-based image reconstruction (MBIR—viz., penalized weighted least-squares, PWLS) in cone-beam CT (CBCT) of the head, focusing on the task of detecting a small, low-contrast intracranial hemorrhage (ICH), and we test the performance of the algorithm in the context of a recently developed CBCT prototype for point-of-care imaging of brain injury. Theoretical predictions of local spatial resolution and noise are computed via an optimization by which regularization (specifically, the quadratic penalty strength) is allowed to vary throughout the image to maximize local task-based detectability index ({{d}\\prime} ). Simulation studies and test-bench experiments were performed using an anthropomorphic head phantom. Three PWLS implementations were tested: conventional (constant) penalty; a certainty-based penalty derived to enforce constant point-spread function, PSF; and the task-based penalty derived to maximize local detectability at each location. Conventional (constant) regularization exhibited a fairly strong degree of spatial variation in {{d}\\prime} , and the certainty-based method achieved uniform PSF, but each exhibited a reduction in detectability compared to the task-based method, which improved detectability up to ~15%. The improvement was strongest in areas of high attenuation (skull base), where the conventional and certainty-based methods tended to over-smooth the data. The task-driven reconstruction method presents a

  10. [Accurate 3D free-form registration between fan-beam CT and cone-beam CT].

    Science.gov (United States)

    Liang, Yueqiang; Xu, Hongbing; Li, Baosheng; Li, Hongsheng; Yang, Fujun

    2012-06-01

    Because the X-ray scatters, the CT numbers in cone-beam CT cannot exactly correspond to the electron densities. This, therefore, results in registration error when the intensity-based registration algorithm is used to register planning fan-beam CT and cone-beam CT. In order to reduce the registration error, we have developed an accurate gradient-based registration algorithm. The gradient-based deformable registration problem is described as a minimization of energy functional. Through the calculus of variations and Gauss-Seidel finite difference method, we derived the iterative formula of the deformable registration. The algorithm was implemented by GPU through OpenCL framework, with which the registration time was greatly reduced. Our experimental results showed that the proposed gradient-based registration algorithm could register more accurately the clinical cone-beam CT and fan-beam CT images compared with the intensity-based algorithm. The GPU-accelerated algorithm meets the real-time requirement in the online adaptive radiotherapy.

  11. GPU-based fast cone beam CT reconstruction from undersampled and noisy projection data via total variation

    International Nuclear Information System (INIS)

    Jia Xun; Lou Yifei; Li Ruijiang; Song, William Y.; Jiang, Steve B.

    2010-01-01

    Purpose: Cone-beam CT (CBCT) plays an important role in image guided radiation therapy (IGRT). However, the large radiation dose from serial CBCT scans in most IGRT procedures raises a clinical concern, especially for pediatric patients who are essentially excluded from receiving IGRT for this reason. The goal of this work is to develop a fast GPU-based algorithm to reconstruct CBCT from undersampled and noisy projection data so as to lower the imaging dose. Methods: The CBCT is reconstructed by minimizing an energy functional consisting of a data fidelity term and a total variation regularization term. The authors developed a GPU-friendly version of the forward-backward splitting algorithm to solve this model. A multigrid technique is also employed. Results: It is found that 20-40 x-ray projections are sufficient to reconstruct images with satisfactory quality for IGRT. The reconstruction time ranges from 77 to 130 s on an NVIDIA Tesla C1060 (NVIDIA, Santa Clara, CA) GPU card, depending on the number of projections used, which is estimated about 100 times faster than similar iterative reconstruction approaches. Moreover, phantom studies indicate that the algorithm enables the CBCT to be reconstructed under a scanning protocol with as low as 0.1 mA s/projection. Comparing with currently widely used full-fan head and neck scanning protocol of ∼360 projections with 0.4 mA s/projection, it is estimated that an overall 36-72 times dose reduction has been achieved in our fast CBCT reconstruction algorithm. Conclusions: This work indicates that the developed GPU-based CBCT reconstruction algorithm is capable of lowering imaging dose considerably. The high computation efficiency in this algorithm makes the iterative CBCT reconstruction approach applicable in real clinical environments.

  12. GPU-based fast cone beam CT reconstruction from undersampled and noisy projection data via total variation.

    Science.gov (United States)

    Jia, Xun; Lou, Yifei; Li, Ruijiang; Song, William Y; Jiang, Steve B

    2010-04-01

    Cone-beam CT (CBCT) plays an important role in image guided radiation therapy (IGRT). However, the large radiation dose from serial CBCT scans in most IGRT procedures raises a clinical concern, especially for pediatric patients who are essentially excluded from receiving IGRT for this reason. The goal of this work is to develop a fast GPU-based algorithm to reconstruct CBCT from undersampled and noisy projection data so as to lower the imaging dose. The CBCT is reconstructed by minimizing an energy functional consisting of a data fidelity term and a total variation regularization term. The authors developed a GPU-friendly version of the forward-backward splitting algorithm to solve this model. A multigrid technique is also employed. It is found that 20-40 x-ray projections are sufficient to reconstruct images with satisfactory quality for IGRT. The reconstruction time ranges from 77 to 130 s on an NVIDIA Tesla C1060 (NVIDIA, Santa Clara, CA) GPU card, depending on the number of projections used, which is estimated about 100 times faster than similar iterative reconstruction approaches. Moreover, phantom studies indicate that the algorithm enables the CBCT to be reconstructed under a scanning protocol with as low as 0.1 mA s/projection. Comparing with currently widely used full-fan head and neck scanning protocol of approximately 360 projections with 0.4 mA s/projection, it is estimated that an overall 36-72 times dose reduction has been achieved in our fast CBCT reconstruction algorithm. This work indicates that the developed GPU-based CBCT reconstruction algorithm is capable of lowering imaging dose considerably. The high computation efficiency in this algorithm makes the iterative CBCT reconstruction approach applicable in real clinical environments.

  13. Reconstruction-of-difference (RoD) imaging for cone-beam CT neuro-angiography

    Science.gov (United States)

    Wu, P.; Stayman, J. W.; Mow, M.; Zbijewski, W.; Sisniega, A.; Aygun, N.; Stevens, R.; Foos, D.; Wang, X.; Siewerdsen, J. H.

    2018-06-01

    Timely evaluation of neurovasculature via CT angiography (CTA) is critical to the detection of pathology such as ischemic stroke. Cone-beam CTA (CBCT-A) systems provide potential advantages in the timely use at the point-of-care, although challenges of a relatively slow gantry rotation speed introduce tradeoffs among image quality, data consistency and data sparsity. This work describes and evaluates a new reconstruction-of-difference (RoD) approach that is robust to such challenges. A fast digital simulation framework was developed to test the performance of the RoD over standard reference reconstruction methods such as filtered back-projection (FBP) and penalized likelihood (PL) over a broad range of imaging conditions, grouped into three scenarios to test the trade-off between data consistency, data sparsity and peak contrast. Two experiments were also conducted using a CBCT prototype and an anthropomorphic neurovascular phantom to test the simulation findings in real data. Performance was evaluated primarily in terms of normalized root mean square error (NRMSE) in comparison to truth, with reconstruction parameters chosen to optimize performance in each case to ensure fair comparison. The RoD approach reduced NRMSE in reconstructed images by up to 50%–53% compared to FBP and up to 29%–31% compared to PL for each scenario. Scan protocols well suited to the RoD approach were identified that balance tradeoffs among data consistency, sparsity and peak contrast—for example, a CBCT-A scan with 128 projections acquired in 8.5 s over a 180°  +  fan angle half-scan for a time attenuation curve with ~8.5 s time-to-peak and 600 HU peak contrast. With imaging conditions such as the simulation scenarios of fixed data sparsity (i.e. varying levels of data consistency and peak contrast), the experiments confirmed the reduction of NRMSE by 34% and 17% compared to FBP and PL, respectively. The RoD approach demonstrated superior performance in 3D angiography

  14. Superiorized algorithm for reconstruction of CT images from sparse-view and limited-angle polyenergetic data

    Science.gov (United States)

    Humphries, T.; Winn, J.; Faridani, A.

    2017-08-01

    Recent work in CT image reconstruction has seen increasing interest in the use of total variation (TV) and related penalties to regularize problems involving reconstruction from undersampled or incomplete data. Superiorization is a recently proposed heuristic which provides an automatic procedure to ‘superiorize’ an iterative image reconstruction algorithm with respect to a chosen objective function, such as TV. Under certain conditions, the superiorized algorithm is guaranteed to find a solution that is as satisfactory as any found by the original algorithm with respect to satisfying the constraints of the problem; this solution is also expected to be superior with respect to the chosen objective. Most work on superiorization has used reconstruction algorithms which assume a linear measurement model, which in the case of CT corresponds to data generated from a monoenergetic x-ray beam. Many CT systems generate x-rays from a polyenergetic spectrum, however, in which the measured data represent an integral of object attenuation over all energies in the spectrum. This inconsistency with the linear model produces the well-known beam hardening artifacts, which impair analysis of CT images. In this work we superiorize an iterative algorithm for reconstruction from polyenergetic data, using both TV and an anisotropic TV (ATV) penalty. We apply the superiorized algorithm in numerical phantom experiments modeling both sparse-view and limited-angle scenarios. In our experiments, the superiorized algorithm successfully finds solutions which are as constraints-compatible as those found by the original algorithm, with significantly reduced TV and ATV values. The superiorized algorithm thus produces images with greatly reduced sparse-view and limited angle artifacts, which are also largely free of the beam hardening artifacts that would be present if a superiorized version of a monoenergetic algorithm were used.

  15. A Fourier-based compressed sensing technique for accelerated CT image reconstruction using first-order methods

    International Nuclear Information System (INIS)

    Choi, Kihwan; Li, Ruijiang; Nam, Haewon; Xing, Lei

    2014-01-01

    As a solution to iterative CT image reconstruction, first-order methods are prominent for the large-scale capability and the fast convergence rate O(1/k 2 ). In practice, the CT system matrix with a large condition number may lead to slow convergence speed despite the theoretically promising upper bound. The aim of this study is to develop a Fourier-based scaling technique to enhance the convergence speed of first-order methods applied to CT image reconstruction. Instead of working in the projection domain, we transform the projection data and construct a data fidelity model in Fourier space. Inspired by the filtered backprojection formalism, the data are appropriately weighted in Fourier space. We formulate an optimization problem based on weighted least-squares in the Fourier space and total-variation (TV) regularization in image space for parallel-beam, fan-beam and cone-beam CT geometry. To achieve the maximum computational speed, the optimization problem is solved using a fast iterative shrinkage-thresholding algorithm with backtracking line search and GPU implementation of projection/backprojection. The performance of the proposed algorithm is demonstrated through a series of digital simulation and experimental phantom studies. The results are compared with the existing TV regularized techniques based on statistics-based weighted least-squares as well as basic algebraic reconstruction technique. The proposed Fourier-based compressed sensing (CS) method significantly improves both the image quality and the convergence rate compared to the existing CS techniques. (paper)

  16. A Fourier-based compressed sensing technique for accelerated CT image reconstruction using first-order methods.

    Science.gov (United States)

    Choi, Kihwan; Li, Ruijiang; Nam, Haewon; Xing, Lei

    2014-06-21

    As a solution to iterative CT image reconstruction, first-order methods are prominent for the large-scale capability and the fast convergence rate [Formula: see text]. In practice, the CT system matrix with a large condition number may lead to slow convergence speed despite the theoretically promising upper bound. The aim of this study is to develop a Fourier-based scaling technique to enhance the convergence speed of first-order methods applied to CT image reconstruction. Instead of working in the projection domain, we transform the projection data and construct a data fidelity model in Fourier space. Inspired by the filtered backprojection formalism, the data are appropriately weighted in Fourier space. We formulate an optimization problem based on weighted least-squares in the Fourier space and total-variation (TV) regularization in image space for parallel-beam, fan-beam and cone-beam CT geometry. To achieve the maximum computational speed, the optimization problem is solved using a fast iterative shrinkage-thresholding algorithm with backtracking line search and GPU implementation of projection/backprojection. The performance of the proposed algorithm is demonstrated through a series of digital simulation and experimental phantom studies. The results are compared with the existing TV regularized techniques based on statistics-based weighted least-squares as well as basic algebraic reconstruction technique. The proposed Fourier-based compressed sensing (CS) method significantly improves both the image quality and the convergence rate compared to the existing CS techniques.

  17. A backprojection-filtration algorithm for nonstandard spiral cone-beam CT with an n-PI-window

    International Nuclear Information System (INIS)

    Yu Hengyong; Ye Yangbo; Zhao Shiying; Wang Ge

    2005-01-01

    For applications in bolus-chasing computed tomography (CT) angiography and electron-beam micro-CT, the backprojection-filtration (BPF) formula developed by Zou and Pan was recently generalized by Ye et al to reconstruct images from cone-beam data collected along a rather flexible scanning locus, including a nonstandard spiral. A major implication of the generalized BPF formula is that it can be applied for n-PI-window-based reconstruction in the nonstandard spiral scanning case. In this paper, we design an n-PI-window-based BPF algorithm, and report the numerical simulation results with the 3D Shepp-Logan phantom and Defrise disk phantom. The proposed BPF algorithm consists of three steps: cone-beam data differentiation, weighted backprojection and inverse Hilbert filtration. Our simulated results demonstrate the feasibility and merits of the proposed algorithm

  18. A framelet-based iterative maximum-likelihood reconstruction algorithm for spectral CT

    Science.gov (United States)

    Wang, Yingmei; Wang, Ge; Mao, Shuwei; Cong, Wenxiang; Ji, Zhilong; Cai, Jian-Feng; Ye, Yangbo

    2016-11-01

    Standard computed tomography (CT) cannot reproduce spectral information of an object. Hardware solutions include dual-energy CT which scans the object twice in different x-ray energy levels, and energy-discriminative detectors which can separate lower and higher energy levels from a single x-ray scan. In this paper, we propose a software solution and give an iterative algorithm that reconstructs an image with spectral information from just one scan with a standard energy-integrating detector. The spectral information obtained can be used to produce color CT images, spectral curves of the attenuation coefficient μ (r,E) at points inside the object, and photoelectric images, which are all valuable imaging tools in cancerous diagnosis. Our software solution requires no change on hardware of a CT machine. With the Shepp-Logan phantom, we have found that although the photoelectric and Compton components were not perfectly reconstructed, their composite effect was very accurately reconstructed as compared to the ground truth and the dual-energy CT counterpart. This means that our proposed method has an intrinsic benefit in beam hardening correction and metal artifact reduction. The algorithm is based on a nonlinear polychromatic acquisition model for x-ray CT. The key technique is a sparse representation of iterations in a framelet system. Convergence of the algorithm is studied. This is believed to be the first application of framelet imaging tools to a nonlinear inverse problem.

  19. Beam-hardening correction in CT based on basis image and TV model

    International Nuclear Information System (INIS)

    Li Qingliang; Yan Bin; Li Lei; Sun Hongsheng; Zhang Feng

    2012-01-01

    In X-ray computed tomography, the beam hardening leads to artifacts and reduces the image quality. It analyzes how beam hardening influences on original projection. According, it puts forward a kind of new beam-hardening correction method based on the basis images and TV model. Firstly, according to physical characteristics of the beam hardening an preliminary correction model with adjustable parameters is set up. Secondly, using different parameters, original projections are operated by the correction model. Thirdly, the projections are reconstructed to obtain a series of basis images. Finally, the linear combination of basis images is the final reconstruction image. Here, with total variation for the final reconstruction image as the cost function, the linear combination coefficients for the basis images are determined according to iterative method. To verify the effectiveness of the proposed method, the experiments are carried out on real phantom and industrial part. The results show that the algorithm significantly inhibits cup and strip artifacts in CT image. (authors)

  20. Low-dose dual-energy cone-beam CT using a total-variation minimization algorithm

    International Nuclear Information System (INIS)

    Min, Jong Hwan

    2011-02-01

    Dual-energy cone-beam CT is an important imaging modality in diagnostic applications, and may also find its use in other application such as therapeutic image guidance. Despite of its clinical values, relatively high radiation dose of dual-energy scan may pose a challenge to its wide use. In this work, we investigated a low-dose, pre-reconstruction type of dual-energy cone-beam CT (CBCT) using a total-variation minimization algorithm for image reconstruction. An empirical dual-energy calibration method was used to prepare material-specific projection data. Raw data at high and low tube voltages are converted into a set of basis functions which can be linearly combined to produce material-specific data using the coefficients obtained through the calibration process. From much fewer views than are conventionally used, material specific images are reconstructed by use of the total-variation minimization algorithm. An experimental study was performed to demonstrate the feasibility of the proposed method using a micro-CT system. We have reconstructed images of the phantoms from only 90 projections acquired at tube voltages of 40 kVp and 90 kVp each. Aluminum-only and acryl-only images were successfully decomposed. We evaluated the quality of the reconstructed images by use of contrast-to-noise ratio and detectability. A low-dose dual-energy CBCT can be realized via the proposed method by greatly reducing the number of projections

  1. A parallel implementation of 3-d CT image reconstruction on a hypercube multiprocessor

    International Nuclear Information System (INIS)

    Chen, C.M.; Lee, S.Y.; Cho, Z.H.

    1990-01-01

    In this paper, the authors describe how image reconstruction in computerized tomography (CT) can be parallelized on a message-passing multiprocessor. In particular, the results obtained from parallel implementation of 3-D CT image reconstruction for parallel beam geometries on the Intel hypercube, iPSC/2, are presented. A two stage pipelining approach is employed for filtering (convolution) and backprojection. The conventional sequential convolution algorithm is modified such that the symmetry of the filter kernel is fully utilized for parallelization. In the backprojection stage, the 3-D incremental algorithm, the authors' recently developed backprojection scheme which is shown to be faster than conventional algorithm, is parallelized

  2. Four-dimensional cone beam CT with adaptive gantry rotation and adaptive data sampling

    International Nuclear Information System (INIS)

    Lu Jun; Guerrero, Thomas M.; Munro, Peter; Jeung, Andrew; Chi, P.-C. M.; Balter, Peter; Zhu, X. Ronald; Mohan, Radhe; Pan Tinsu

    2007-01-01

    We have developed a new four-dimensional cone beam CT (4D-CBCT) on a Varian image-guided radiation therapy system, which has radiation therapy treatment and cone beam CT imaging capabilities. We adapted the speed of gantry rotation time of the CBCT to the average breath cycle of the patient to maintain the same level of image quality and adjusted the data sampling frequency to keep a similar level of radiation exposure to the patient. Our design utilized the real-time positioning and monitoring system to record the respiratory signal of the patient during the acquisition of the CBCT data. We used the full-fan bowtie filter during data acquisition, acquired the projection data over 200 deg of gantry rotation, and reconstructed the images with a half-scan cone beam reconstruction. The scan time for a 200-deg gantry rotation per patient ranged from 3.3 to 6.6 min for the average breath cycle of 3-6 s. The radiation dose of the 4D-CBCT was about 1-2 times the radiation dose of the 4D-CT on a multislice CT scanner. We evaluated the 4D-CBCT in scanning, data processing and image quality with phantom studies. We demonstrated the clinical applicability of the 4D-CBCT and compared the 4D-CBCT and the 4D-CT scans in four patient studies. The contrast-to-noise ratio of the 4D-CT was 2.8-3.5 times of the contrast-to-noise ratio of the 4D-CBCT in the four patient studies

  3. A fast iterative soft-thresholding algorithm for few-view CT reconstruction

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Junfeng; Mou, Xuanqin; Zhang, Yanbo [Jiaotong Univ., Xi' an (China). Inst. of Image Processing and Pattern Recognition

    2011-07-01

    Iterative soft-thresholding algorithms with total variation regularization can produce high-quality reconstructions from few views and even in the presence of noise. However, these algorithms are known to converge quite slowly, with a proven theoretically global convergence rate O(1/k), where k is iteration number. In this paper, we present a fast iterative soft-thresholding algorithm for few-view fan beam CT reconstruction with a global convergence rate O(1/k{sup 2}), which is significantly faster than the iterative soft-thresholding algorithm. Simulation results demonstrate the superior performance of the proposed algorithm in terms of convergence speed and reconstruction quality. (orig.)

  4. Improved compressed sensing-based cone-beam CT reconstruction using adaptive prior image constraints

    Science.gov (United States)

    Lee, Ho; Xing, Lei; Davidi, Ran; Li, Ruijiang; Qian, Jianguo; Lee, Rena

    2012-04-01

    Volumetric cone-beam CT (CBCT) images are acquired repeatedly during a course of radiation therapy and a natural question to ask is whether CBCT images obtained earlier in the process can be utilized as prior knowledge to reduce patient imaging dose in subsequent scans. The purpose of this work is to develop an adaptive prior image constrained compressed sensing (APICCS) method to solve this problem. Reconstructed images using full projections are taken on the first day of radiation therapy treatment and are used as prior images. The subsequent scans are acquired using a protocol of sparse projections. In the proposed APICCS algorithm, the prior images are utilized as an initial guess and are incorporated into the objective function in the compressed sensing (CS)-based iterative reconstruction process. Furthermore, the prior information is employed to detect any possible mismatched regions between the prior and current images for improved reconstruction. For this purpose, the prior images and the reconstructed images are classified into three anatomical regions: air, soft tissue and bone. Mismatched regions are identified by local differences of the corresponding groups in the two classified sets of images. A distance transformation is then introduced to convert the information into an adaptive voxel-dependent relaxation map. In constructing the relaxation map, the matched regions (unchanged anatomy) between the prior and current images are assigned with smaller weight values, which are translated into less influence on the CS iterative reconstruction process. On the other hand, the mismatched regions (changed anatomy) are associated with larger values and the regions are updated more by the new projection data, thus avoiding any possible adverse effects of prior images. The APICCS approach was systematically assessed by using patient data acquired under standard and low-dose protocols for qualitative and quantitative comparisons. The APICCS method provides an

  5. Image reconstruction design of industrial CT instrument for teaching

    International Nuclear Information System (INIS)

    Zou Yongning; Cai Yufang

    2009-01-01

    Industrial CT instrument for teaching is applied to teaching and study in field of physics and radiology major, image reconstruction is an important part of software on CT instrument. The paper expatiate on CT physical theory and first generation CT reconstruction algorithm, describe scan process of industrial CT instrument for teaching; analyze image artifact as result of displacement of rotation center, implement method of center displacement correcting, design and complete image reconstruction software, application shows that reconstructed image is very clear and qualitatively high. (authors)

  6. Simultaneous motion estimation and image reconstruction (SMEIR) for 4D cone-beam CT

    International Nuclear Information System (INIS)

    Wang, Jing; Gu, Xuejun

    2013-01-01

    Purpose: Image reconstruction and motion model estimation in four-dimensional cone-beam CT (4D-CBCT) are conventionally handled as two sequential steps. Due to the limited number of projections at each phase, the image quality of 4D-CBCT is degraded by view aliasing artifacts, and the accuracy of subsequent motion modeling is decreased by the inferior 4D-CBCT. The objective of this work is to enhance both the image quality of 4D-CBCT and the accuracy of motion model estimation with a novel strategy enabling simultaneous motion estimation and image reconstruction (SMEIR).Methods: The proposed SMEIR algorithm consists of two alternating steps: (1) model-based iterative image reconstruction to obtain a motion-compensated primary CBCT (m-pCBCT) and (2) motion model estimation to obtain an optimal set of deformation vector fields (DVFs) between the m-pCBCT and other 4D-CBCT phases. The motion-compensated image reconstruction is based on the simultaneous algebraic reconstruction technique (SART) coupled with total variation minimization. During the forward- and backprojection of SART, measured projections from an entire set of 4D-CBCT are used for reconstruction of the m-pCBCT by utilizing the updated DVF. The DVF is estimated by matching the forward projection of the deformed m-pCBCT and measured projections of other phases of 4D-CBCT. The performance of the SMEIR algorithm is quantitatively evaluated on a 4D NCAT phantom. The quality of reconstructed 4D images and the accuracy of tumor motion trajectory are assessed by comparing with those resulting from conventional sequential 4D-CBCT reconstructions (FDK and total variation minimization) and motion estimation (demons algorithm). The performance of the SMEIR algorithm is further evaluated by reconstructing a lung cancer patient 4D-CBCT.Results: Image quality of 4D-CBCT is greatly improved by the SMEIR algorithm in both phantom and patient studies. When all projections are used to reconstruct a 3D-CBCT by FDK, motion

  7. Fast 4D cone-beam CT from 60 s acquisitions

    Directory of Open Access Journals (Sweden)

    David C. Hansen

    2018-01-01

    Full Text Available Background & purpose: Four dimensional Cone beam CT (CBCT has many potential benefits for radiotherapy but suffers from poor image quality, long acquisition times, and/or long reconstruction times. In this work we present a fast iterative reconstruction algorithm for 4D reconstruction of fast acquisition cone beam CT, as well as a new method for temporal regularization and compare to state of the art methods for 4D CBCT. Materials & methods: Regularization parameters for the iterative algorithms were found automatically via computer optimization on 60 s acquisitions using the XCAT phantom. Nineteen lung cancer patients were scanned with 60 s arcs using the onboard image on a Varian trilogy linear accelerator. Images were reconstructed using an accelerated ordered subset algorithm. A frequency based temporal regularization algorithm was developed and compared to the McKinnon-Bates algorithm, 4D total variation and prior images compressed sensing (PICCS. Results: All reconstructions were completed in 60 s or less. The proposed method provided a structural similarity of 0.915, compared with 0.786 for the classic McKinnon-bates method. For the patient study, it provided fewer image artefacts than PICCS, and better spatial resolution than 4D TV. Conclusion: Four dimensional iterative CBCT reconstruction was done in less than 60 s, demonstrating the clinical feasibility. The frequency based method outperformed 4D total variation and PICCS on the simulated data, and for patients allowed for tumor location based on 60 s acquisitions, even for slowly breathing patients. It should thus be suitable for routine clinical use.

  8. Simulation and experimental studies of three-dimensional (3D) image reconstruction from insufficient sampling data based on compressed-sensing theory for potential applications to dental cone-beam CT

    International Nuclear Information System (INIS)

    Je, U.K.; Lee, M.S.; Cho, H.S.; Hong, D.K.; Park, Y.O.; Park, C.K.; Cho, H.M.; Choi, S.I.; Woo, T.H.

    2015-01-01

    In practical applications of three-dimensional (3D) tomographic imaging, there are often challenges for image reconstruction from insufficient sampling data. In computed tomography (CT), for example, image reconstruction from sparse views and/or limited-angle (<360°) views would enable fast scanning with reduced imaging doses to the patient. In this study, we investigated and implemented a reconstruction algorithm based on the compressed-sensing (CS) theory, which exploits the sparseness of the gradient image with substantially high accuracy, for potential applications to low-dose, high-accurate dental cone-beam CT (CBCT). We performed systematic simulation works to investigate the image characteristics and also performed experimental works by applying the algorithm to a commercially-available dental CBCT system to demonstrate its effectiveness for image reconstruction in insufficient sampling problems. We successfully reconstructed CBCT images of superior accuracy from insufficient sampling data and evaluated the reconstruction quality quantitatively. Both simulation and experimental demonstrations of the CS-based reconstruction from insufficient data indicate that the CS-based algorithm can be applied directly to current dental CBCT systems for reducing the imaging doses and further improving the image quality

  9. Exact Reconstruction From Uniformly Attenuated Helical Cone-Beam Projections in SPECT

    International Nuclear Information System (INIS)

    Gullberg, Grant T.; Huang, Qiu; You, Jiangsheng; Zeng, Gengsheng L.

    2008-01-01

    In recent years the development of cone-beam reconstruction algorithms has been an active research area in x-ray computed tomography (CT), and significant progress has been made in the advancement of algorithms. Theoretically exact and computationally efficient analytical algorithms can be found in the literature. However, in single photon emission computed tomography (SPECT), published cone-beam reconstruction algorithms are either approximate or involve iterative methods. The SPECT reconstruction problem is more complicated due to degradations in the imaging detection process, one of which is the effect of attenuation of gamma ray photons. Attenuation should be compensated for to obtain quantitative results. In this paper, an analytical reconstruction algorithm for uniformly attenuated cone-beam projection data is presented for SPECT imaging. The algorithm adopts the DBH method, a procedure consisting of differentiation and backprojection followed by a finite inverse cosh-weighted Hilbert transform. The significance of the proposed approach is that a selected region of interest can be reconstructed even with a detector with a reduced field of view. The algorithm is designed for a general trajectory. However, to validate the algorithm, a numerical study was performed using a helical trajectory. The implementation is efficient and the simulation result is promising

  10. Evaluation of accelerated iterative x-ray CT image reconstruction using floating point graphics hardware

    International Nuclear Information System (INIS)

    Kole, J S; Beekman, F J

    2006-01-01

    Statistical reconstruction methods offer possibilities to improve image quality as compared with analytical methods, but current reconstruction times prohibit routine application in clinical and micro-CT. In particular, for cone-beam x-ray CT, the use of graphics hardware has been proposed to accelerate the forward and back-projection operations, in order to reduce reconstruction times. In the past, wide application of this texture hardware mapping approach was hampered owing to limited intrinsic accuracy. Recently, however, floating point precision has become available in the latest generation commodity graphics cards. In this paper, we utilize this feature to construct a graphics hardware accelerated version of the ordered subset convex reconstruction algorithm. The aims of this paper are (i) to study the impact of using graphics hardware acceleration for statistical reconstruction on the reconstructed image accuracy and (ii) to measure the speed increase one can obtain by using graphics hardware acceleration. We compare the unaccelerated algorithm with the graphics hardware accelerated version, and for the latter we consider two different interpolation techniques. A simulation study of a micro-CT scanner with a mathematical phantom shows that at almost preserved reconstructed image accuracy, speed-ups of a factor 40 to 222 can be achieved, compared with the unaccelerated algorithm, and depending on the phantom and detector sizes. Reconstruction from physical phantom data reconfirms the usability of the accelerated algorithm for practical cases

  11. Evaluation of tilted cone-beam CT orbits in the development of a dedicated hybrid mammotomograph

    International Nuclear Information System (INIS)

    Madhav, P; Crotty, D J; Tornai, M P; McKinley, R L

    2009-01-01

    A compact dedicated 3D breast SPECT-CT (mammotomography) system is currently under development. In its initial prototype, the cone-beam CT sub-system is restricted to a fixed-tilt circular rotation around the patient's pendant breast. This study evaluated stationary-tilt angles for the CT sub-system that will enable maximal volumetric sampling and viewing of the breast and chest wall. Images of geometric/anthropomorphic phantoms were acquired using various fixed-tilt circular and 3D sinusoidal trajectories. The iteratively reconstructed images showed more distortion and attenuation coefficient inaccuracy from tilted cone-beam orbits than from the complex trajectory. Additionally, line profiles illustrated cupping artifacts in planes distal to the central plane of the tilted cone-beam, otherwise not apparent for images acquired with complex trajectories. This indicates that undersampled cone-beam data may be an additional cause of cupping artifacts. High-frequency objects could be distinguished for all trajectories, but their shapes and locations were corrupted by out-of-plane frequency information. Although more acrylic balls were visualized with a fixed-tilt and nearly flat cone-beam at the posterior of the breast, 3D complex trajectories have less distortion and more complete sampling throughout the reconstruction volume. While complex trajectories would ideally be preferred, negatively fixed-tilt source-detector configuration demonstrates minimally distorted patient images.

  12. Auto calibration of a cone-beam-CT

    International Nuclear Information System (INIS)

    Gross, Daniel; Heil, Ulrich; Schulze, Ralf; Schoemer, Elmar; Schwanecke, Ulrich

    2012-01-01

    Purpose: This paper introduces a novel autocalibration method for cone-beam-CTs (CBCT) or flat-panel CTs, assuming a perfect rotation. The method is based on ellipse-fitting. Autocalibration refers to accurate recovery of the geometric alignment of a CBCT device from projection images alone, without any manual measurements. Methods: The authors use test objects containing small arbitrarily positioned radio-opaque markers. No information regarding the relative positions of the markers is used. In practice, the authors use three to eight metal ball bearings (diameter of 1 mm), e.g., positioned roughly in a vertical line such that their projection image curves on the detector preferably form large ellipses over the circular orbit. From this ellipse-to-curve mapping and also from its inversion the authors derive an explicit formula. Nonlinear optimization based on this mapping enables them to determine the six relevant parameters of the system up to the device rotation angle, which is sufficient to define the geometry of a CBCT-machine assuming a perfect rotational movement. These parameters also include out-of-plane rotations. The authors evaluate their method by simulation based on data used in two similar approaches [L. Smekal, M. Kachelriess, S. E, and K. Wa, “Geometric misalignment and calibration in cone-beam tomography,” Med. Phys. 31(12), 3242–3266 (2004); K. Yang, A. L. C. Kwan, D. F. Miller, and J. M. Boone, “A geometric calibration method for cone beam CT systems,” Med. Phys. 33(6), 1695–1706 (2006)]. This allows a direct comparison of accuracy. Furthermore, the authors present real-world 3D reconstructions of a dry human spine segment and an electronic device. The reconstructions were computed from projections taken with a commercial dental CBCT device having two different focus-to-detector distances that were both calibrated with their method. The authors compare their reconstruction with a reconstruction computed by the manufacturer of the

  13. The use of cone beam computed tomography in the postoperative assessment of orbital wall fracture reconstruction.

    Science.gov (United States)

    Tsao, Kim; Cheng, Andrew; Goss, Alastair; Donovan, David

    2014-07-01

    Computed tomography (CT) is currently the standard in postoperative evaluation of orbital wall fracture reconstruction, but cone beam computed tomography (CBCT) offers potential advantages including reduced radiation dose and cost. The purpose of this study is to examine objectively the image quality of CBCT in the postoperative evaluation of orbital fracture reconstruction, its radiation dose, and cost compared with CT. Four consecutive patients with orbital wall fractures in whom surgery was indicated underwent orbital reconstruction with radio-opaque grafts (bone, titanium-reinforced polyethylene, and titanium plate) and were assessed postoperatively with orbital CBCT. CBCT was evaluated for its ability to provide objective information regarding the adequacy of orbital reconstruction, radiation dose, and cost. In all patients, CBCT was feasible and provided hard tissue image quality comparable to CT with significantly reduced radiation dose and cost. However, it has poorer soft tissue resolution, which limits its ability to identify the extraocular muscles, their relationship to the reconstructive graft, and potential muscle entrapment. CBCT is a viable alternative to CT in the routine postoperative evaluation of orbital fracture reconstruction. However, in the patient who develops gaze restriction postoperatively, conventional CT is preferred over CBCT for its superior soft tissue resolution to exclude extraocular muscle entrapment.

  14. Cone Beam CT vs. Fan Beam CT: A Comparison of Image Quality and Dose Delivered Between Two Differing CT Imaging Modalities.

    Science.gov (United States)

    Lechuga, Lawrence; Weidlich, Georg A

    2016-09-12

    A comparison of image quality and dose delivered between two differing computed tomography (CT) imaging modalities-fan beam and cone beam-was performed. A literature review of quantitative analyses for various image quality aspects such as uniformity, signal-to-noise ratio, artifact presence, spatial resolution, modulation transfer function (MTF), and low contrast resolution was generated. With these aspects quantified, cone beam computed tomography (CBCT) shows a superior spatial resolution to that of fan beam, while fan beam shows a greater ability to produce clear and anatomically correct images with better soft tissue differentiation. The results indicate that fan beam CT produces superior images to that of on-board imaging (OBI) cone beam CT systems, while providing a considerably less dose to the patient.

  15. SU-D-207-04: GPU-Based 4D Cone-Beam CT Reconstruction Using Adaptive Meshing Method

    International Nuclear Information System (INIS)

    Zhong, Z; Gu, X; Iyengar, P; Mao, W; Wang, J; Guo, X

    2015-01-01

    Purpose: Due to the limited number of projections at each phase, the image quality of a four-dimensional cone-beam CT (4D-CBCT) is often degraded, which decreases the accuracy of subsequent motion modeling. One of the promising methods is the simultaneous motion estimation and image reconstruction (SMEIR) approach. The objective of this work is to enhance the computational speed of the SMEIR algorithm using adaptive feature-based tetrahedral meshing and GPU-based parallelization. Methods: The first step is to generate the tetrahedral mesh based on the features of a reference phase 4D-CBCT, so that the deformation can be well captured and accurately diffused from the mesh vertices to voxels of the image volume. After the mesh generation, the updated motion model and other phases of 4D-CBCT can be obtained by matching the 4D-CBCT projection images at each phase with the corresponding forward projections of the deformed reference phase of 4D-CBCT. The entire process of this 4D-CBCT reconstruction method is implemented on GPU, resulting in significantly increasing the computational efficiency due to its tremendous parallel computing ability. Results: A 4D XCAT digital phantom was used to test the proposed mesh-based image reconstruction algorithm. The image Result shows both bone structures and inside of the lung are well-preserved and the tumor position can be well captured. Compared to the previous voxel-based CPU implementation of SMEIR, the proposed method is about 157 times faster for reconstructing a 10 -phase 4D-CBCT with dimension 256×256×150. Conclusion: The GPU-based parallel 4D CBCT reconstruction method uses the feature-based mesh for estimating motion model and demonstrates equivalent image Result with previous voxel-based SMEIR approach, with significantly improved computational speed

  16. Evaluation of robustness of maximum likelihood cone-beam CT reconstruction with total variation regularization

    International Nuclear Information System (INIS)

    Stsepankou, D; Arns, A; Hesser, J; Ng, S K; Zygmanski, P

    2012-01-01

    The objective of this paper is to evaluate an iterative maximum likelihood (ML) cone–beam computed tomography (CBCT) reconstruction with total variation (TV) regularization with respect to the robustness of the algorithm due to data inconsistencies. Three different and (for clinical application) typical classes of errors are considered for simulated phantom and measured projection data: quantum noise, defect detector pixels and projection matrix errors. To quantify those errors we apply error measures like mean square error, signal-to-noise ratio, contrast-to-noise ratio and streak indicator. These measures are derived from linear signal theory and generalized and applied for nonlinear signal reconstruction. For quality check, we focus on resolution and CT-number linearity based on a Catphan phantom. All comparisons are made versus the clinical standard, the filtered backprojection algorithm (FBP). In our results, we confirm and substantially extend previous results on iterative reconstruction such as massive undersampling of the number of projections. Errors of projection matrix parameters of up to 1° projection angle deviations are still in the tolerance level. Single defect pixels exhibit ring artifacts for each method. However using defect pixel compensation, allows up to 40% of defect pixels for passing the standard clinical quality check. Further, the iterative algorithm is extraordinarily robust in the low photon regime (down to 0.05 mAs) when compared to FPB, allowing for extremely low-dose image acquisitions, a substantial issue when considering daily CBCT imaging for position correction in radiotherapy. We conclude that the ML method studied herein is robust under clinical quality assurance conditions. Consequently, low-dose regime imaging, especially for daily patient localization in radiation therapy is possible without change of the current hardware of the imaging system. (paper)

  17. Superiority of CT imaging reconstruction on Linux OS

    International Nuclear Information System (INIS)

    Lin Shaochun; Yan Xufeng; Wu Tengfang; Luo Xiaomei; Cai Huasong

    2010-01-01

    Objective: To compare the speed of CT reconstruction using the Linux and Windows OS. Methods: Shepp-Logan head phantom in different pixel size was projected to obtain the sinogram by using the inverse Fourier transformation, filtered back projection and Radon transformation on both Linux and Windows OS. Results: CT image reconstruction using the Linux operating system was significantly better and more efficient than Windows. Conclusion: CT image reconstruction using the Linux operating system is more efficient. (authors)

  18. Research of ART method in CT image reconstruction

    International Nuclear Information System (INIS)

    Li Zhipeng; Cong Peng; Wu Haifeng

    2005-01-01

    This paper studied Algebraic Reconstruction Technique (ART) in CT image reconstruction. Discussed the ray number influence on image quality. And the adopting of smooth method got high quality CT image. (authors)

  19. Ultrafast cone-beam CT scatter correction with GPU-based Monte Carlo simulation

    Directory of Open Access Journals (Sweden)

    Yuan Xu

    2014-03-01

    Full Text Available Purpose: Scatter artifacts severely degrade image quality of cone-beam CT (CBCT. We present an ultrafast scatter correction framework by using GPU-based Monte Carlo (MC simulation and prior patient CT image, aiming at automatically finish the whole process including both scatter correction and reconstruction within 30 seconds.Methods: The method consists of six steps: 1 FDK reconstruction using raw projection data; 2 Rigid Registration of planning CT to the FDK results; 3 MC scatter calculation at sparse view angles using the planning CT; 4 Interpolation of the calculated scatter signals to other angles; 5 Removal of scatter from the raw projections; 6 FDK reconstruction using the scatter-corrected projections. In addition to using GPU to accelerate MC photon simulations, we also use a small number of photons and a down-sampled CT image in simulation to further reduce computation time. A novel denoising algorithm is used to eliminate MC noise from the simulated scatter images caused by low photon numbers. The method is validated on one simulated head-and-neck case with 364 projection angles.Results: We have examined variation of the scatter signal among projection angles using Fourier analysis. It is found that scatter images at 31 angles are sufficient to restore those at all angles with < 0.1% error. For the simulated patient case with a resolution of 512 × 512 × 100, we simulated 5 × 106 photons per angle. The total computation time is 20.52 seconds on a Nvidia GTX Titan GPU, and the time at each step is 2.53, 0.64, 14.78, 0.13, 0.19, and 2.25 seconds, respectively. The scatter-induced shading/cupping artifacts are substantially reduced, and the average HU error of a region-of-interest is reduced from 75.9 to 19.0 HU.Conclusion: A practical ultrafast MC-based CBCT scatter correction scheme is developed. It accomplished the whole procedure of scatter correction and reconstruction within 30 seconds.----------------------------Cite this

  20. Cone-beam CT angiography of the thorax. An experimental study

    International Nuclear Information System (INIS)

    Yoshida, Katsuya; Shimada, Kazuhiro; Tadokoro, Hiroyuki

    1999-01-01

    The authors recently developed a cone-beam computed tomography (CT) scanner and this report presents their evaluation of its potential for thoracic vascular imaging. An X-ray tube and a video-fluoroscopic system were rotated around the objects and 360 projected images were collected in a 12-s scan. Each image was digitized and a 3 dimensional (D) image (256 x 256 x 256 voxel volume with a voxel dimension of 0.9 x 0.9 x 0.9 mm) was reconstructed. Two different 3D-CT angiographies were investigated in 2 pigs: right atriography and thoracic aortography. Each pig was anesthetized, mechanically ventilated and positioned within the scanner. Contrast agent was infused through the right atrium or the aortic root at a rate of 3 ml/s during the scan. The right atriography scan clearly delineated the anatomy of the pulmonary artery, heart chambers and thoracic aorta. The thoracic aortography scan also clearly delineated the aortic anatomy including the internal thoracic and intercostal arteries. In conclusion, cone-beam CT angiography is potentially useful for thoracic vascular imaging. (author)

  1. Reconstruction of FXR Beam Conditions

    International Nuclear Information System (INIS)

    Nexen, W E; Scarpetti, R D; Zentler, J

    2001-01-01

    Beam-envelope radius, envelope angle, and beam emittance can be derived from measurements of beam radius for at least three different transport conditions. We have used this technique to reconstruct exit parameters from the FXR injector and accelerator. We use a diamagnetic loop (DML) to measure the magnetic moment of the high current beam. With no assumptions about radial profile, we can derive the beam mean squire radius from the moment under certain easily met conditions. Since it is this parameter which is required for the reconstruction, it is evident that the DML is the ideal diagnostic for this technique. The simplest application of this technique requires at least three shots for a reconstruction but in reality requires averaging over many more shots because of shot to shot variation. Since DML measurements do not interfere with the beam, single shot time resolved measurements of the beam parameters appear feasible if one uses an array of at least three DMLs separated by known transport conditions

  2. SU-E-J-150: Four-Dimensional Cone-Beam CT Algorithm by Extraction of Physical and Motion Parameter of Mobile Targets Retrospective to Image Reconstruction with Motion Modeling

    International Nuclear Information System (INIS)

    Ali, I; Ahmad, S; Alsbou, N

    2015-01-01

    Purpose: To develop 4D-cone-beam CT (CBCT) algorithm by motion modeling that extracts actual length, CT numbers level and motion amplitude of a mobile target retrospective to image reconstruction by motion modeling. Methods: The algorithm used three measurable parameters: apparent length and blurred CT number distribution of a mobile target obtained from CBCT images to determine actual length, CT-number value of the stationary target, and motion amplitude. The predictions of this algorithm were tested with mobile targets that with different well-known sizes made from tissue-equivalent gel which was inserted into a thorax phantom. The phantom moved sinusoidally in one-direction to simulate respiratory motion using eight amplitudes ranging 0–20mm. Results: Using this 4D-CBCT algorithm, three unknown parameters were extracted that include: length of the target, CT number level, speed or motion amplitude for the mobile targets retrospective to image reconstruction. The motion algorithms solved for the three unknown parameters using measurable apparent length, CT number level and gradient for a well-defined mobile target obtained from CBCT images. The motion model agreed with measured apparent lengths which were dependent on the actual target length and motion amplitude. The gradient of the CT number distribution of the mobile target is dependent on the stationary CT number level, actual target length and motion amplitude. Motion frequency and phase did not affect the elongation and CT number distribution of the mobile target and could not be determined. Conclusion: A 4D-CBCT motion algorithm was developed to extract three parameters that include actual length, CT number level and motion amplitude or speed of mobile targets directly from reconstructed CBCT images without prior knowledge of the stationary target parameters. This algorithm provides alternative to 4D-CBCT without requirement to motion tracking and sorting of the images into different breathing phases

  3. SU-E-J-150: Four-Dimensional Cone-Beam CT Algorithm by Extraction of Physical and Motion Parameter of Mobile Targets Retrospective to Image Reconstruction with Motion Modeling

    Energy Technology Data Exchange (ETDEWEB)

    Ali, I; Ahmad, S [University of Oklahoma Health Sciences, Oklahoma City, OK (United States); Alsbou, N [Ohio Northern University, Ada, OH (United States)

    2015-06-15

    Purpose: To develop 4D-cone-beam CT (CBCT) algorithm by motion modeling that extracts actual length, CT numbers level and motion amplitude of a mobile target retrospective to image reconstruction by motion modeling. Methods: The algorithm used three measurable parameters: apparent length and blurred CT number distribution of a mobile target obtained from CBCT images to determine actual length, CT-number value of the stationary target, and motion amplitude. The predictions of this algorithm were tested with mobile targets that with different well-known sizes made from tissue-equivalent gel which was inserted into a thorax phantom. The phantom moved sinusoidally in one-direction to simulate respiratory motion using eight amplitudes ranging 0–20mm. Results: Using this 4D-CBCT algorithm, three unknown parameters were extracted that include: length of the target, CT number level, speed or motion amplitude for the mobile targets retrospective to image reconstruction. The motion algorithms solved for the three unknown parameters using measurable apparent length, CT number level and gradient for a well-defined mobile target obtained from CBCT images. The motion model agreed with measured apparent lengths which were dependent on the actual target length and motion amplitude. The gradient of the CT number distribution of the mobile target is dependent on the stationary CT number level, actual target length and motion amplitude. Motion frequency and phase did not affect the elongation and CT number distribution of the mobile target and could not be determined. Conclusion: A 4D-CBCT motion algorithm was developed to extract three parameters that include actual length, CT number level and motion amplitude or speed of mobile targets directly from reconstructed CBCT images without prior knowledge of the stationary target parameters. This algorithm provides alternative to 4D-CBCT without requirement to motion tracking and sorting of the images into different breathing phases

  4. Exact fan-beam image reconstruction algorithm for truncated projection data acquired from an asymmetric half-size detector

    International Nuclear Information System (INIS)

    Leng Shuai; Zhuang Tingliang; Nett, Brian E; Chen Guanghong

    2005-01-01

    In this paper, we present a new algorithm designed for a specific data truncation problem in fan-beam CT. We consider a scanning configuration in which the fan-beam projection data are acquired from an asymmetrically positioned half-sized detector. Namely, the asymmetric detector only covers one half of the scanning field of view. Thus, the acquired fan-beam projection data are truncated at every view angle. If an explicit data rebinning process is not invoked, this data acquisition configuration will reek havoc on many known fan-beam image reconstruction schemes including the standard filtered backprojection (FBP) algorithm and the super-short-scan FBP reconstruction algorithms. However, we demonstrate that a recently developed fan-beam image reconstruction algorithm which reconstructs an image via filtering a backprojection image of differentiated projection data (FBPD) survives the above fan-beam data truncation problem. Namely, we may exactly reconstruct the whole image object using the truncated data acquired in a full scan mode (2π angular range). We may also exactly reconstruct a small region of interest (ROI) using the truncated projection data acquired in a short-scan mode (less than 2π angular range). The most important characteristic of the proposed reconstruction scheme is that an explicit data rebinning process is not introduced. Numerical simulations were conducted to validate the new reconstruction algorithm

  5. Motion estimation and compensation in dynamic spiral CT reconstruction

    International Nuclear Information System (INIS)

    Kimdon, J.; Grangeat, P.; Koenig, A.; Bonnet, St.

    2004-01-01

    Respiratory and cardiac motion causes blurring in dynamic X-ray Computed Tomography (CT). Fast scans reduce this problem, but they require a higher radiation dose per time period to maintain the signal to noise ratio of the resulting images, thereby magnifying the health risk to the patient. As an alternative to increased radiation, our team has already developed a cone-beam reconstruction algorithm based on a dynamic particle model that estimates, predicts, and compensates for respiratory motion in circular X-ray CT. The current paper presents an extension of this method to spiral CT, applicable to modern multi-slice scanners that take advantage of the speed and dose benefits of helical trajectories. We adapted all three main areas of the algorithm: backprojection, prediction, and compensation/accumulation. In backprojection, we changed the longitudinal re-binning technique, filter direction, and the method of enforcing the data sufficiency requirements. For prediction, we had to be careful of objects appearing and disappearing as the scanner bed advanced. For compensation/accumulation, we controlled the reconstruction time and combined images to cover a greater longitudinal extent for each phase in the respiratory or cardiac cycle. Tests with moving numerical phantoms demonstrate that the algorithm successfully improves the temporal resolution of the images without increasing the dose or reducing the signal-to-noise ratio. (authors)

  6. Reconstructed coronal views of CT and isotopic images of the pancreas

    International Nuclear Information System (INIS)

    Kasuga, Toshio; Kobayashi, Toshio; Nakanishi, Fumiko

    1980-01-01

    To compare functional images of the pancreas by scintigraphy with morphological views of the pancreas by CT, CT coronal views of the pancreas were reconstructed. As CT coronal views were reconstructed from the routine scanning, there was a problem in longitudinal spatial resolution. However, almost satisfactory total images of the pancreas were obtained by improving images adequately. In 27 patients whose diseases had been confirmed, it was easy to compare pancreatic scintigrams with pancreatic CT images by using reconstructed CT coronal views, and information which had not been obtained by original CT images could be obtained by using reconstructed CT coronal views. Especially, defects on pancreatic images and the shape of pancreas which had not been visualized clearly by scintigraphy alone could be visualized by using reconstructed CT coronal views of the pancreas. (Tsunoda, M.)

  7. SU-F-J-114: On-Treatment Imagereconstruction Using Transit Images of Treatment Beams Through Patient and Thosethrough Planning CT Images

    International Nuclear Information System (INIS)

    Lee, H; Cho, S; Cheong, K; Jung, J; Jung, S; Kim, J; Yeo, I

    2016-01-01

    Purpose: To reconstruct patient images at the time of radiation delivery using measured transit images of treatment beams through patient and calculated transit images through planning CT images. Methods: We hypothesize that the ratio of the measured transit images to the calculated images may provide changed amounts of the patient image between times of planning CT and treatment. To test, we have devised lung phantoms with a tumor object (3-cm diameter) placed at iso-center (simulating planning CT) and off-center by 1 cm (simulating treatment). CT images of the two phantoms were acquired; the image of the off-centered phantom, unavailable clinically, represents the reference on-treatment image in the image quality of planning CT. Cine-transit images through the two phantoms were also acquired in EPID from a non-modulated 6 MV beam when the gantry was rotated 360 degrees; the image through the centered phantom simulates calculated image. While the current study is a feasibility study, in reality our computational EPID model can be applicable in providing accurate transit image from MC simulation. Changed MV HU values were reconstructed from the ratio between two EPID projection data, converted to KV HU values, and added to the planning CT, thereby reconstructing the on-treatment image of the patient limited to the irradiated region of the phantom. Results: The reconstructed image was compared with the reference image. Except for local HU differences>200 as a maximum, excellent agreement was found. The average difference across the entire image was 16.2 HU. Conclusion: We have demonstrated the feasibility of a method of reconstructing on-treatment images of a patient using EPID image and planning CT images. Further studies will include resolving the local HU differences and investigation on the dosimetry impact of the reconstructed image.

  8. SU-F-J-114: On-Treatment Imagereconstruction Using Transit Images of Treatment Beams Through Patient and Thosethrough Planning CT Images

    Energy Technology Data Exchange (ETDEWEB)

    Lee, H; Cho, S [KAIST, Yuseong-gu, Daejeon (Korea, Republic of); Cheong, K [Hallym University Sacred Heart Hospital, Anyang (Korea, Republic of); Jung, J [East Carolina University Greenville, NC (United States); Jung, S [Samsung Medical Cener, Gangnam-gu, Seoul (Korea, Republic of); Kim, J [Yonsei Cancer Center, Seoul (Korea, Republic of); Yeo, I [Loma Linda University Medical Center, Loma Linda, CA (United States)

    2016-06-15

    Purpose: To reconstruct patient images at the time of radiation delivery using measured transit images of treatment beams through patient and calculated transit images through planning CT images. Methods: We hypothesize that the ratio of the measured transit images to the calculated images may provide changed amounts of the patient image between times of planning CT and treatment. To test, we have devised lung phantoms with a tumor object (3-cm diameter) placed at iso-center (simulating planning CT) and off-center by 1 cm (simulating treatment). CT images of the two phantoms were acquired; the image of the off-centered phantom, unavailable clinically, represents the reference on-treatment image in the image quality of planning CT. Cine-transit images through the two phantoms were also acquired in EPID from a non-modulated 6 MV beam when the gantry was rotated 360 degrees; the image through the centered phantom simulates calculated image. While the current study is a feasibility study, in reality our computational EPID model can be applicable in providing accurate transit image from MC simulation. Changed MV HU values were reconstructed from the ratio between two EPID projection data, converted to KV HU values, and added to the planning CT, thereby reconstructing the on-treatment image of the patient limited to the irradiated region of the phantom. Results: The reconstructed image was compared with the reference image. Except for local HU differences>200 as a maximum, excellent agreement was found. The average difference across the entire image was 16.2 HU. Conclusion: We have demonstrated the feasibility of a method of reconstructing on-treatment images of a patient using EPID image and planning CT images. Further studies will include resolving the local HU differences and investigation on the dosimetry impact of the reconstructed image.

  9. Low-dose megavoltage cone-beam CT for radiation therapy

    International Nuclear Information System (INIS)

    Pouliot, Jean; Bani-Hashemi, Ali; Chen, Josephine; Svatos, Michelle; Ghelmansarai, Farhad; Mitschke, Matthias; Aubin, Michele; Xia Ping; Morin, Olivier; Bucci, Kara; Roach, Mack; Hernandez, Paco; Zheng Zirao; Hristov, Dimitre; Verhey, Lynn

    2005-01-01

    Purpose: The objective of this work was to demonstrate the feasibility of acquiring low-exposure megavoltage cone-beam CT (MV CBCT) three-dimensional (3D) image data of sufficient quality to register the CBCT images to kilovoltage planning CT images for patient alignment and dose verification purposes. Methods and materials: A standard clinical 6-MV Primus linear accelerator, operating in arc therapy mode, and an amorphous-silicon (a-Si) flat-panel electronic portal-imaging device (EPID) were employed. The dose-pulse rate of a 6-MV Primus accelerator beam was windowed to expose an a-Si flat panel by using only 0.02 to 0.08 monitor units (MUs) per image. A triggered image-acquisition mode was designed to produce a high signal-to-noise ratio without pulsing artifacts. Several data sets were acquired for an anthropomorphic head phantom and frozen sheep and pig cadaver heads, as well as for a head-and-neck cancer patient on intensity-modulated radiotherapy (IMRT). For each CBCT image, a set of 90 to 180 projection images incremented by 1 deg to 2 deg was acquired. The two-dimensional (2D) projection images were then synthesized into a 3D image by use of cone-beam CT reconstruction. The resulting MV CBCT image set was used to visualize the 3D bony anatomy and some soft-tissue details. The 3D image registration with the kV planning CT was performed either automatically by application of a maximization of mutual information (MMI) algorithm or manually by aligning multiple 2D slices. Results: Low-noise 3D MV CBCT images without pulsing artifacts were acquired with a total delivered dose that ranged from 5 to 15 cGy. Acquisition times, including image readout, were on the order of 90 seconds for 180 projection images taken through a continuous gantry rotation of 180 deg . The processing time of the data required an additional 90 seconds for the reconstruction of a 256 3 cube with 1.0-mm voxel size. Implanted gold markers (1 mm x 3 mm) were easily visible for all exposure

  10. Dose reduction in pediatric abdominal CT: use of iterative reconstruction techniques across different CT platforms

    International Nuclear Information System (INIS)

    Khawaja, Ranish Deedar Ali; Singh, Sarabjeet; Otrakji, Alexi; Padole, Atul; Lim, Ruth; Nimkin, Katherine; Westra, Sjirk; Kalra, Mannudeep K.; Gee, Michael S.

    2015-01-01

    Dose reduction in children undergoing CT scanning is an important priority for the radiology community and public at large. Drawbacks of radiation reduction are increased image noise and artifacts, which can affect image interpretation. Iterative reconstruction techniques have been developed to reduce noise and artifacts from reduced-dose CT examinations, although reconstruction algorithm, magnitude of dose reduction and effects on image quality vary. We review the reconstruction principles, radiation dose potential and effects on image quality of several iterative reconstruction techniques commonly used in clinical settings, including 3-D adaptive iterative dose reduction (AIDR-3D), adaptive statistical iterative reconstruction (ASIR), iDose, sinogram-affirmed iterative reconstruction (SAFIRE) and model-based iterative reconstruction (MBIR). We also discuss clinical applications of iterative reconstruction techniques in pediatric abdominal CT. (orig.)

  11. Dose reduction in pediatric abdominal CT: use of iterative reconstruction techniques across different CT platforms

    Energy Technology Data Exchange (ETDEWEB)

    Khawaja, Ranish Deedar Ali; Singh, Sarabjeet; Otrakji, Alexi; Padole, Atul; Lim, Ruth; Nimkin, Katherine; Westra, Sjirk; Kalra, Mannudeep K.; Gee, Michael S. [MGH Imaging, Massachusetts General Hospital, Harvard Medical School, Boston, MA (United States)

    2015-07-15

    Dose reduction in children undergoing CT scanning is an important priority for the radiology community and public at large. Drawbacks of radiation reduction are increased image noise and artifacts, which can affect image interpretation. Iterative reconstruction techniques have been developed to reduce noise and artifacts from reduced-dose CT examinations, although reconstruction algorithm, magnitude of dose reduction and effects on image quality vary. We review the reconstruction principles, radiation dose potential and effects on image quality of several iterative reconstruction techniques commonly used in clinical settings, including 3-D adaptive iterative dose reduction (AIDR-3D), adaptive statistical iterative reconstruction (ASIR), iDose, sinogram-affirmed iterative reconstruction (SAFIRE) and model-based iterative reconstruction (MBIR). We also discuss clinical applications of iterative reconstruction techniques in pediatric abdominal CT. (orig.)

  12. Reconstructing cone-beam CT with spatially varying qualities for adaptive radiotherapy: a proof-of-principle study.

    Science.gov (United States)

    Lu, Wenting; Yan, Hao; Gu, Xuejun; Tian, Zhen; Luo, Ouyang; Yang, Liu; Zhou, Linghong; Cervino, Laura; Wang, Jing; Jiang, Steve; Jia, Xun

    2014-10-21

    With the aim of maximally reducing imaging dose while meeting requirements for adaptive radiation therapy (ART), we propose in this paper a new cone beam CT (CBCT) acquisition and reconstruction method that delivers images with a low noise level inside a region of interest (ROI) and a relatively high noise level outside the ROI. The acquired projection images include two groups: densely sampled projections at a low exposure with a large field of view (FOV) and sparsely sampled projections at a high exposure with a small FOV corresponding to the ROI. A new algorithm combining the conventional filtered back-projection algorithm and the tight-frame iterative reconstruction algorithm is also designed to reconstruct the CBCT based on these projection data. We have validated our method on a simulated head-and-neck (HN) patient case, a semi-real experiment conducted on a HN cancer patient under a full-fan scan mode, as well as a Catphan phantom under a half-fan scan mode. Relative root-mean-square errors (RRMSEs) of less than 3% for the entire image and ~1% within the ROI compared to the ground truth have been observed. These numbers demonstrate the ability of our proposed method to reconstruct high-quality images inside the ROI. As for the part outside ROI, although the images are relatively noisy, it can still provide sufficient information for radiation dose calculations in ART. Dose distributions calculated on our CBCT image and on a standard CBCT image are in agreement, with a mean relative difference of 0.082% inside the ROI and 0.038% outside the ROI. Compared with the standard clinical CBCT scheme, an imaging dose reduction of approximately 3-6 times inside the ROI was achieved, as well as an 8 times outside the ROI. Regarding computational efficiency, it takes 1-3 min to reconstruct a CBCT image depending on the number of projections used. These results indicate that the proposed method has the potential for application in ART.

  13. Technical aspects of X-ray micro-computed tomography. Initial experience of 27-μm resolution using feldkamp cone-beam reconstruction

    International Nuclear Information System (INIS)

    Yamamoto, Shuji; Suzuki, Masahiro; Kohara, Kazushi; Iinuma, Gen; Moriyama, Noriyuki

    2007-01-01

    The objective of this study was to introduce the technical utility of micro-computed tomography (CT) with 27-μm resolution by cone-beam CT algorithm. Whole-body micro-CT scans were performed to honeybee. Two- and three-dimensional image analyses were performed by originally developed and available open-source software for acquired images. The original contribution of this work is to describe the technical characteristics of the X-ray micro-CT system, keeping a small experimental insect in a unique condition. Micro-CT may be used as a rapid prototyping tool to research and understand the high-resolution system with Feldkamp cone-beam reconstruction. (author)

  14. Self-calibration of a cone-beam micro-CT system

    International Nuclear Information System (INIS)

    Patel, V.; Chityala, R. N.; Hoffmann, K. R.; Ionita, C. N.; Bednarek, D. R.; Rudin, S.

    2009-01-01

    Use of cone-beam computed tomography (CBCT) is becoming more frequent. For proper reconstruction, the geometry of the CBCT systems must be known. While the system can be designed to reduce errors in the geometry, calibration measurements must still be performed and corrections applied. Investigators have proposed techniques using calibration objects for system calibration. In this study, the authors present methods to calibrate a rotary-stage CB micro-CT (CBμCT) system using only the images acquired of the object to be reconstructed, i.e., without the use of calibration objects. Projection images are acquired using a CBμCT system constructed in the authors' laboratories. Dark- and flat-field corrections are performed. Exposure variations are detected and quantified using analysis of image regions with an unobstructed view of the x-ray source. Translations that occur during the acquisition in the horizontal direction are detected, quantified, and corrected based on sinogram analysis. The axis of rotation is determined using registration of antiposed projection images. These techniques were evaluated using data obtained with calibration objects and phantoms. The physical geometric axis of rotation is determined and aligned with the rotational axis (assumed to be the center of the detector plane) used in the reconstruction process. The parameters describing this axis agree to within 0.1 mm and 0.3 deg with those determined using other techniques. Blurring due to residual calibration errors has a point-spread function in the reconstructed planes with a full-width-at-half-maximum of less than 125 μm in a tangential direction and essentially zero in the radial direction for the rotating object. The authors have used this approach on over 100 acquisitions over the past 2 years and have regularly obtained high-quality reconstructions, i.e., without artifacts and no detectable blurring of the reconstructed objects. This self-calibrating approach not only obviates

  15. Time-resolved C-arm cone beam CT angiography (TR-CBCTA) imaging from a single short-scan C-arm cone beam CT acquisition with intra-arterial contrast injection

    Science.gov (United States)

    Li, Yinsheng; Garrett, John W.; Li, Ke; Wu, Yijing; Johnson, Kevin; Schafer, Sebastian; Strother, Charles; Chen, Guang-Hong

    2018-04-01

    Time-resolved C-arm cone-beam CT (CBCT) angiography (TR-CBCTA) images can be generated from a series of CBCT acquisitions that satisfy data sufficiency condition in analytical image reconstruction theory. In this work, a new technique was developed to generate TR-CBCTA images from a single short-scan CBCT data acquisition with contrast media injection. The reconstruction technique enabling this application is a previously developed image reconstruction technique, synchronized multi-artifact reduction with tomographic reconstruction (SMART-RECON). In this new application, the acquired short-scan CBCT projection data were sorted into a union of several sub-sectors of view angles and each sub-sector of view angles corresponds to an individual image volume to be reconstructed. The SMART-RECON method was then used to jointly reconstruct all of these individual image volumes under two constraints: (1) each individual image volume is maximally consistent with the measured cone-beam projection data within the corresponding view angle sector and (2) the nuclear norm of the image matrix is minimized. The difference between these reconstructed individual image volumes is used to generated the desired subtracted angiograms. To validate the technique, numerical simulation data generated from a fractal tree angiogram phantom were used to quantitatively study the accuracy of the proposed method and retrospective in vivo human subject studies were used to demonstrate the feasibility of generating TR-CBCTA in clinical practice.

  16. Low-dose CT image reconstruction using gain intervention-based dictionary learning

    Science.gov (United States)

    Pathak, Yadunath; Arya, K. V.; Tiwari, Shailendra

    2018-05-01

    Computed tomography (CT) approach is extensively utilized in clinical diagnoses. However, X-ray residue in human body may introduce somatic damage such as cancer. Owing to radiation risk, research has focused on the radiation exposure distributed to patients through CT investigations. Therefore, low-dose CT has become a significant research area. Many researchers have proposed different low-dose CT reconstruction techniques. But, these techniques suffer from various issues such as over smoothing, artifacts, noise, etc. Therefore, in this paper, we have proposed a novel integrated low-dose CT reconstruction technique. The proposed technique utilizes global dictionary-based statistical iterative reconstruction (GDSIR) and adaptive dictionary-based statistical iterative reconstruction (ADSIR)-based reconstruction techniques. In case the dictionary (D) is predetermined, then GDSIR can be used and if D is adaptively defined then ADSIR is appropriate choice. The gain intervention-based filter is also used as a post-processing technique for removing the artifacts from low-dose CT reconstructed images. Experiments have been done by considering the proposed and other low-dose CT reconstruction techniques on well-known benchmark CT images. Extensive experiments have shown that the proposed technique outperforms the available approaches.

  17. Cone-beam CT image contrast and attenuation-map linearity improvement (CALI) for brain stereotactic radiosurgery procedures

    Science.gov (United States)

    Hashemi, Sayed Masoud; Lee, Young; Eriksson, Markus; Nordström, Hâkan; Mainprize, James; Grouza, Vladimir; Huynh, Christopher; Sahgal, Arjun; Song, William Y.; Ruschin, Mark

    2017-03-01

    A Contrast and Attenuation-map (CT-number) Linearity Improvement (CALI) framework is proposed for cone-beam CT (CBCT) images used for brain stereotactic radiosurgery (SRS). The proposed framework is used together with our high spatial resolution iterative reconstruction algorithm and is tailored for the Leksell Gamma Knife ICON (Elekta, Stockholm, Sweden). The incorporated CBCT system in ICON facilitates frameless SRS planning and treatment delivery. The ICON employs a half-cone geometry to accommodate the existing treatment couch. This geometry increases the amount of artifacts and together with other physical imperfections causes image inhomogeneity and contrast reduction. Our proposed framework includes a preprocessing step, involving a shading and beam-hardening artifact correction, and a post-processing step to correct the dome/capping artifact caused by the spatial variations in x-ray energy generated by bowtie-filter. Our shading correction algorithm relies solely on the acquired projection images (i.e. no prior information required) and utilizes filtered-back-projection (FBP) reconstructed images to generate a segmented bone and soft-tissue map. Ideal projections are estimated from the segmented images and a smoothed version of the difference between the ideal and measured projections is used in correction. The proposed beam-hardening and dome artifact corrections are segmentation free. The CALI was tested on CatPhan, as well as patient images acquired on the ICON system. The resulting clinical brain images show substantial improvements in soft contrast visibility, revealing structures such as ventricles and lesions which were otherwise un-detectable in FBP-reconstructed images. The linearity of the reconstructed attenuation-map was also improved, resulting in more accurate CT#.

  18. Alpha image reconstruction (AIR): A new iterative CT image reconstruction approach using voxel-wise alpha blending

    International Nuclear Information System (INIS)

    Hofmann, Christian; Sawall, Stefan; Knaup, Michael; Kachelrieß, Marc

    2014-01-01

    Purpose: Iterative image reconstruction gains more and more interest in clinical routine, as it promises to reduce image noise (and thereby patient dose), to reduce artifacts, or to improve spatial resolution. Among vendors and researchers, however, there is no consensus of how to best achieve these aims. The general approach is to incorporatea priori knowledge into iterative image reconstruction, for example, by adding additional constraints to the cost function, which penalize variations between neighboring voxels. However, this approach to regularization in general poses a resolution noise trade-off because the stronger the regularization, and thus the noise reduction, the stronger the loss of spatial resolution and thus loss of anatomical detail. The authors propose a method which tries to improve this trade-off. The proposed reconstruction algorithm is called alpha image reconstruction (AIR). One starts with generating basis images, which emphasize certain desired image properties, like high resolution or low noise. The AIR algorithm reconstructs voxel-specific weighting coefficients that are applied to combine the basis images. By combining the desired properties of each basis image, one can generate an image with lower noise and maintained high contrast resolution thus improving the resolution noise trade-off. Methods: All simulations and reconstructions are performed in native fan-beam geometry. A water phantom with resolution bar patterns and low contrast disks is simulated. A filtered backprojection (FBP) reconstruction with a Ram-Lak kernel is used as a reference reconstruction. The results of AIR are compared against the FBP results and against a penalized weighted least squares reconstruction which uses total variation as regularization. The simulations are based on the geometry of the Siemens Somatom Definition Flash scanner. To quantitatively assess image quality, the authors analyze line profiles through resolution patterns to define a contrast

  19. Hybrid spectral CT reconstruction.

    Directory of Open Access Journals (Sweden)

    Darin P Clark

    Full Text Available Current photon counting x-ray detector (PCD technology faces limitations associated with spectral fidelity and photon starvation. One strategy for addressing these limitations is to supplement PCD data with high-resolution, low-noise data acquired with an energy-integrating detector (EID. In this work, we propose an iterative, hybrid reconstruction technique which combines the spectral properties of PCD data with the resolution and signal-to-noise characteristics of EID data. Our hybrid reconstruction technique is based on an algebraic model of data fidelity which substitutes the EID data into the data fidelity term associated with the PCD reconstruction, resulting in a joint reconstruction problem. Within the split Bregman framework, these data fidelity constraints are minimized subject to additional constraints on spectral rank and on joint intensity-gradient sparsity measured between the reconstructions of the EID and PCD data. Following a derivation of the proposed technique, we apply it to the reconstruction of a digital phantom which contains realistic concentrations of iodine, barium, and calcium encountered in small-animal micro-CT. The results of this experiment suggest reliable separation and detection of iodine at concentrations ≥ 5 mg/ml and barium at concentrations ≥ 10 mg/ml in 2-mm features for EID and PCD data reconstructed with inherent spatial resolutions of 176 μm and 254 μm, respectively (point spread function, FWHM. Furthermore, hybrid reconstruction is demonstrated to enhance spatial resolution within material decomposition results and to improve low-contrast detectability by as much as 2.6 times relative to reconstruction with PCD data only. The parameters of the simulation experiment are based on an in vivo micro-CT experiment conducted in a mouse model of soft-tissue sarcoma. Material decomposition results produced from this in vivo data demonstrate the feasibility of distinguishing two K-edge contrast agents with

  20. Hybrid spectral CT reconstruction

    Science.gov (United States)

    Clark, Darin P.

    2017-01-01

    Current photon counting x-ray detector (PCD) technology faces limitations associated with spectral fidelity and photon starvation. One strategy for addressing these limitations is to supplement PCD data with high-resolution, low-noise data acquired with an energy-integrating detector (EID). In this work, we propose an iterative, hybrid reconstruction technique which combines the spectral properties of PCD data with the resolution and signal-to-noise characteristics of EID data. Our hybrid reconstruction technique is based on an algebraic model of data fidelity which substitutes the EID data into the data fidelity term associated with the PCD reconstruction, resulting in a joint reconstruction problem. Within the split Bregman framework, these data fidelity constraints are minimized subject to additional constraints on spectral rank and on joint intensity-gradient sparsity measured between the reconstructions of the EID and PCD data. Following a derivation of the proposed technique, we apply it to the reconstruction of a digital phantom which contains realistic concentrations of iodine, barium, and calcium encountered in small-animal micro-CT. The results of this experiment suggest reliable separation and detection of iodine at concentrations ≥ 5 mg/ml and barium at concentrations ≥ 10 mg/ml in 2-mm features for EID and PCD data reconstructed with inherent spatial resolutions of 176 μm and 254 μm, respectively (point spread function, FWHM). Furthermore, hybrid reconstruction is demonstrated to enhance spatial resolution within material decomposition results and to improve low-contrast detectability by as much as 2.6 times relative to reconstruction with PCD data only. The parameters of the simulation experiment are based on an in vivo micro-CT experiment conducted in a mouse model of soft-tissue sarcoma. Material decomposition results produced from this in vivo data demonstrate the feasibility of distinguishing two K-edge contrast agents with a spectral

  1. Effects of data sampling rate on image quality in fan-beam-CT system

    International Nuclear Information System (INIS)

    Iwata, Akira; Yamagishi, Nobutoshi; Suzumura, Nobuo; Horiba, Isao.

    1984-01-01

    Investigation was made into the relationship between spatial resolution or artifacts and data sampling rate in order to pursue the causes of the degradation of CT image quality by computer simulation. First the generation of projection data and reconstruction calculating process are described, and then the results are shown about the relation between angular sampling interval and spatical resolution or artifacts, and about the relation between projection data sampling interval and spatial resolution or artifacts. It was clarified that the formulation of the relationship between spatial resolution and data sampling rate performed so far for parallel X-ray beam was able to be applied to fan beam. As a conclusion, when other reconstruction parameters are the same in fan beam CT systems, spatial resolution can be determined by projection data sampling rate rather than angular sampling rate. The mechanism of artifact generation due to the insufficient number of angular samples was made clear. It was also made clear that there was a definite relationship among measuring region, angular sampling rate and projection data sampling rate, and the amount of artifacts depending upon projection data sampling rate was proportional to the amount of spatial frequency components (Aliasing components) of a test object above the Nyquist frequency of projection data. (Wakatsuki, Y.)

  2. Iterative CT reconstruction with correction for known rigid motion

    Energy Technology Data Exchange (ETDEWEB)

    Nuyts, Johan [Katholieke Univ. Leuven (Belgium). Dept. of Nuclear Medicine; Kim, Jung-Ha; Fulton, Roger [Sydney Univ., NSW (Australia). School of Physics; Westmead Hospital, Sydney (Australia). Medical Physics

    2011-07-01

    In PET/CT brain imaging, correction for motion may be needed, in particular for children and psychiatric patients. Motion is more likely to occur in the lengthy PET measurement, but also during the short CT acquisition patient motion is possible. Rigid motion of the head can be measured independently from the PET/CT system with optical devices. In this paper, we propose a method and some preliminary simulation results for iterative CT reconstruction with correction for known rigid motion. We implemented an iterative algorithm for fully 3D reconstruction from helical CT scans. The motion of the head is incorporated in the system matrix as a view-dependent motion of the CT-system. The first simulation results indicate that some motion patterns may produce loss of essential data. This loss precludes exact reconstruction and results in artifacts in the reconstruction, even when motion is taken into account. However, by reducing the pitch during acquisition, the same motion pattern no longer caused artifacts in the motion corrected image. (orig.)

  3. Application of three-dimensional CT reconstruction cranioplasty

    International Nuclear Information System (INIS)

    Yan Shuli; Yun Yongxing; Wan Kunming; Qiu Jian

    2011-01-01

    Objective: To study the application of three-dimensional CT reconstruction in cranioplasty. Methods: 46 patients with skull defect were divided into two group. One group underwent CT examination and three-dimensional reconstruction, and then the Titanium nets production company manufactured corresponding titanium meshes were shaped those data before the operation. The other group received traditional operation in which titanium meshes were shaped during operation. The average time of operation were compared. Results: The average time of operation of the first group is 86.6±13.6 mins, and that of the second group is 115±15.0 mins. The difference of average operation time between the two groups was statistically significant. Conclusion: Three-dimensional CT reconstruction techniques contribute to shorten the average operation time, reduce the intensity of neurosurgeon's work and the patien's risk. (authors)

  4. Reconstruction CT imaging of the hypopharynx and the larynx

    International Nuclear Information System (INIS)

    Okuno, Tetsuji; Fujimura, Akiko; Murakami, Yasushi; Shiga, Hayao

    1986-01-01

    The multiplanar reconstruction CT imaging of the hypopharynx and the larynx was performed on a total of 20 cases: 8 with laryngeal carcinomas, 6 with hypopharyngeal carcinomas, 4 with vocal cord paralyses due to various causes, 1 with laryngeal amyloidosis, 1 with inflammatory granuloma of the hypopharynx. Coronal, segittal, and parasagittal reconstruction images were obtained from either 1 or 2 mm overlapping axial scans with 4 or 5 mm slice thickness (3 cases) using 5 sec scan times during queit breathing. In 15 cases with coronal reconstruction imaging, the anatomical derangements of the laryngopharyngeal structures especially along the undersurface of the true vocal cord to the false cord level, the lateral wall of the pyriform sinus, and the paraglottic space were demonstrated more clearly than the axial CT imaging. In 5 cases with sagittal reconstruction imaging, the vertical extension of the lesions through the anterior commisure was more clearly depicted than the axial CT imaging. In 8 cases with parasagittal reconstruction imaging, which is along the vocal fold or across the aryepiglottic fold, pathological changes along the aryepiglottic fold, the arytenoid-corniculate cartilage complex, and the tip of the pyriform sinus were more clearly demonstrated than the axial CT imaging. In determining the feasibility of conservation surgery of the larynx and the hypopharynx, reconstruction CT imaging is recommended as the diagnostic procedure of a choice, which would supplement the findings of the routine axial CT imaging. (author)

  5. Estimating local noise power spectrum from a few FBP-reconstructed CT scans

    Energy Technology Data Exchange (ETDEWEB)

    Zeng, Rongping, E-mail: rongping.zeng@fda.hhs.gov; Gavrielides, Marios A.; Petrick, Nicholas; Sahiner, Berkman; Li, Qin; Myers, Kyle J. [Division of Imaging, Diagnostics, and Software Reliability, Office of Science and Engineering Laboratories, CDRH, FDA, Silver Spring, Maryland 20993 (United States)

    2016-01-15

    Purpose: Traditional ways to estimate 2D CT noise power spectrum (NPS) involve an ensemble average of the power spectrums of many noisy scans. When only a few scans are available, regions of interest are often extracted from different locations to obtain sufficient samples to estimate the NPS. Using image samples from different locations ignores the nonstationarity of CT noise and thus cannot accurately characterize its local properties. The purpose of this work is to develop a method to estimate local NPS using only a few fan-beam CT scans. Methods: As a result of FBP reconstruction, the CT NPS has the same radial profile shape for all projection angles, with the magnitude varying with the noise level in the raw data measurement. This allows a 2D CT NPS to be factored into products of a 1D angular and a 1D radial function in polar coordinates. The polar separability of CT NPS greatly reduces the data requirement for estimating the NPS. The authors use this property and derive a radial NPS estimation method: in brief, the radial profile shape is estimated from a traditional NPS based on image samples extracted at multiple locations. The amplitudes are estimated by fitting the traditional local NPS to the estimated radial profile shape. The estimated radial profile shape and amplitudes are then combined to form a final estimate of the local NPS. We evaluate the accuracy of the radial NPS method and compared it to traditional NPS methods in terms of normalized mean squared error (NMSE) and signal detectability index. Results: For both simulated and real CT data sets, the local NPS estimated with no more than six scans using the radial NPS method was very close to the reference NPS, according to the metrics of NMSE and detectability index. Even with only two scans, the radial NPS method was able to achieve a fairly good accuracy. Compared to those estimated using traditional NPS methods, the accuracy improvement was substantial when a few scans were available

  6. Brachytherapy reconstruction using orthogonal scout views from the CT

    International Nuclear Information System (INIS)

    Perez, J.; Lliso, F.; Carmona, V.; Bea, J.; Tormo, A.; Petschen, I.

    1996-01-01

    Introduction: CT assisted brachytherapy planning is demonstrating to have great advantages as external RT planning does. One of the problems we have found in this approach with the conventional gynecological Fletcher applicators is the high amount of artefacts (ovoids with rectal and vessical protections) in the CT slice. We have introduced a reconstruction method based on scout views in order to avoid this problem, allowing us to perform brachytherapy reconstruction completely CT assisted. We use a virtual simulation chain by General Electric Medical Systems. Method and discussion: Two orthogonal scout views (0 and 90 tube positions) are performed. The reconstruction method takes into account the virtual position of the focus and the fact that there is only divergence in the transverse plane. Algorithms developed for sources as well as for reference points localisation (A, B, lymphatic Fletcher trapezoid, pelvic wall, etc.) are presented. This method has the following practical advantages: the porte-cassette is not necessary, the image quality can be improved (it is very helpful in pelvic lateral views that are critical in conventional radiographs), the total time to get the data is smaller than for conventional radiographs (reduction of patient motion effects) and problems that appear in CT-slice based reconstruction in the case of strongly curved intrauterine applicators are avoided. Even though the resolution is smaller than in conventional radiographs it is good enough for brachytherapy. Regarding the CT planning this method presents the interesting feature that the co-ordinate system is the same for the reconstruction process that for the CT-slices set. As the application can be reconstructed from scout views and the doses can be evaluated on CT slices it is easier to correlate the dose values obtained for the traditional points with those provided by the CT information

  7. CT and MRI post-processing reconstructions in maxillo-facial trauma

    International Nuclear Information System (INIS)

    Olszycki, M.; Grzelak, P.; Stanczyk, L.; Kozakiewicz, M.; Arkuszewski, P.

    2004-01-01

    The aim of the study is to evaluate the reliability of CT and MR imaging and their post-processing reconstructions in the cases of facial trauma. CT studies were performed in 34 patients: 13 suspected of sinus fractures, 20 with orbital fractures and 1 with broken supraorbital bone fragment. MR imaging was also performed in 16 of these patients. The CT data were reconstructed in the 2D and 3D mode. The CT and MR images were digitally fused using an own program. The CT and MR images, their reconstructions and their fusion were evaluated according to the quality of visualization of a pathological lesions. Surgery was the method of reference. The reconstructed CT images allowed to recognize properly maxillary-oral fenestration in 5 cases. In 20 patients with orbital fracture, CT 3D reformations visualized well the morphology of the fissure. In 13 of these patients,the small bone fragments and orbital soft tissues prolapsed towards the maxillary sinus were depicted. Among the 16 patients who underwent MR examination, in 6 cases we revealed dislocation of the inferior rectus muscle towards the sinus, whereas in 9 cases MR images clearly excluded this pathology. In 1 patient, the digitally fused CT/MR images allowed to determine the actual position of small bone fragment within the muscle. In 1 patient with broken supraorbital bone fragment, evaluation of the 3D model allowed to exclude communication with intracranial space. In the next 8 patients with maxillo-zygomatic injures, the CT reconstructions did not support the diagnosis. The surgery correlated well with the post-processing CT and CT/MR fused images, contrary to the original CT ones which often were diagnostically insufficient. Spiral CT 2D and 3D-reconstructed images of the face allow to depict clearly the anatomical spatial relationships and the position, course and displacement of fractured fragments; thus, they support the surgery. The MR images of these patients reveal soft tissues clearly. The digital

  8. Parametric boundary reconstruction algorithm for industrial CT metrology application.

    Science.gov (United States)

    Yin, Zhye; Khare, Kedar; De Man, Bruno

    2009-01-01

    High-energy X-ray computed tomography (CT) systems have been recently used to produce high-resolution images in various nondestructive testing and evaluation (NDT/NDE) applications. The accuracy of the dimensional information extracted from CT images is rapidly approaching the accuracy achieved with a coordinate measuring machine (CMM), the conventional approach to acquire the metrology information directly. On the other hand, CT systems generate the sinogram which is transformed mathematically to the pixel-based images. The dimensional information of the scanned object is extracted later by performing edge detection on reconstructed CT images. The dimensional accuracy of this approach is limited by the grid size of the pixel-based representation of CT images since the edge detection is performed on the pixel grid. Moreover, reconstructed CT images usually display various artifacts due to the underlying physical process and resulting object boundaries from the edge detection fail to represent the true boundaries of the scanned object. In this paper, a novel algorithm to reconstruct the boundaries of an object with uniform material composition and uniform density is presented. There are three major benefits in the proposed approach. First, since the boundary parameters are reconstructed instead of image pixels, the complexity of the reconstruction algorithm is significantly reduced. The iterative approach, which can be computationally intensive, will be practical with the parametric boundary reconstruction. Second, the object of interest in metrology can be represented more directly and accurately by the boundary parameters instead of the image pixels. By eliminating the extra edge detection step, the overall dimensional accuracy and process time can be improved. Third, since the parametric reconstruction approach shares the boundary representation with other conventional metrology modalities such as CMM, boundary information from other modalities can be directly

  9. Clinical application of 3D reconstruction of tracheobronchial tree with electron beam CT

    International Nuclear Information System (INIS)

    Yao Zhenwei; Shen Tianzhen

    2002-01-01

    Objective: To explore the clinical promise of CT 3D reconstruction of tracheobronchial tree (TBT) by analyzing 73 cases retrospectively. Methods: All the 73 cases were collected from October 1997 to February 2000, who were scanned by EBCT with 130 kV and 630 mA. The scanning method was continuous volume scan, the slice thickness were 3 mm or 1.5 mm. All cross-sectional images were transmitted to the INSIGHT workstation and reconstructed with SSD (shaded surface display), and the threshold setting were -500 to -300 HU. Results: 3D reconstruction of TBT with EBCT could reveal the abnormal changes of TBT by many kinds of diseases including central cancer, inflammation, bronchiectasis, saber-sheath trachea, trachea cancer, congenital disorders, post-surgical changes of lung cancer, and stenoses by adjacent benign or malignant diseases. It could be used to locate the stenoses and measure stenotic extent. Of the 35 central cancer cases with 3D reconstruction, 6 cases were pestle obstructed, 15 cases cone obstructed, 5 cases interrupted irregularly, 8 cases with eccentric stenoses, and 1 case with right stem destroyed and right upper lobe bronchus obstructed. Conclusion: 3D reconstruction of TBT has characteristic sign in the diagnosis or differential diagnosis of central airway's benign or malignant stenoses, and it is of instructional value in clinical use

  10. SU-D-206-01: Employing a Novel Consensus Optimization Strategy to Achieve Iterative Cone Beam CT Reconstruction On a Multi-GPU Platform

    International Nuclear Information System (INIS)

    Li, B; Tian, Z; Jiang, S; Jia, X; Zhou, L

    2016-01-01

    Purpose: While compressed sensing-based cone-beam CT (CBCT) iterative reconstruction techniques have demonstrated tremendous capability of reconstructing high-quality images from undersampled noisy data, its long computation time still hinders wide application in routine clinic. The purpose of this study is to develop a reconstruction framework that employs modern consensus optimization techniques to achieve CBCT reconstruction on a multi-GPU platform for improved computational efficiency. Methods: Total projection data were evenly distributed to multiple GPUs. Each GPU performed reconstruction using its own projection data with a conventional total variation regularization approach to ensure image quality. In addition, the solutions from GPUs were subject to a consistency constraint that they should be identical. We solved the optimization problem with all the constraints considered rigorously using an alternating direction method of multipliers (ADMM) algorithm. The reconstruction framework was implemented using OpenCL on a platform with two Nvidia GTX590 GPU cards, each with two GPUs. We studied the performance of our method and demonstrated its advantages through a simulation case with a NCAT phantom and an experimental case with a Catphan phantom. Result: Compared with the CBCT images reconstructed using conventional FDK method with full projection datasets, our proposed method achieved comparable image quality with about one third projection numbers. The computation time on the multi-GPU platform was ∼55 s and ∼ 35 s in the two cases respectively, achieving a speedup factor of ∼ 3.0 compared with single GPU reconstruction. Conclusion: We have developed a consensus ADMM-based CBCT reconstruction method which enabled performing reconstruction on a multi-GPU platform. The achieved efficiency made this method clinically attractive.

  11. SU-D-206-01: Employing a Novel Consensus Optimization Strategy to Achieve Iterative Cone Beam CT Reconstruction On a Multi-GPU Platform

    Energy Technology Data Exchange (ETDEWEB)

    Li, B [University of Texas Southwestern Medical Center, Dallas, TX (United States); Southern Medical University, Guangzhou, Guangdong (China); Tian, Z; Jiang, S; Jia, X [University of Texas Southwestern Medical Center, Dallas, TX (United States); Zhou, L [Southern Medical University, Guangzhou, Guangdong (China)

    2016-06-15

    Purpose: While compressed sensing-based cone-beam CT (CBCT) iterative reconstruction techniques have demonstrated tremendous capability of reconstructing high-quality images from undersampled noisy data, its long computation time still hinders wide application in routine clinic. The purpose of this study is to develop a reconstruction framework that employs modern consensus optimization techniques to achieve CBCT reconstruction on a multi-GPU platform for improved computational efficiency. Methods: Total projection data were evenly distributed to multiple GPUs. Each GPU performed reconstruction using its own projection data with a conventional total variation regularization approach to ensure image quality. In addition, the solutions from GPUs were subject to a consistency constraint that they should be identical. We solved the optimization problem with all the constraints considered rigorously using an alternating direction method of multipliers (ADMM) algorithm. The reconstruction framework was implemented using OpenCL on a platform with two Nvidia GTX590 GPU cards, each with two GPUs. We studied the performance of our method and demonstrated its advantages through a simulation case with a NCAT phantom and an experimental case with a Catphan phantom. Result: Compared with the CBCT images reconstructed using conventional FDK method with full projection datasets, our proposed method achieved comparable image quality with about one third projection numbers. The computation time on the multi-GPU platform was ∼55 s and ∼ 35 s in the two cases respectively, achieving a speedup factor of ∼ 3.0 compared with single GPU reconstruction. Conclusion: We have developed a consensus ADMM-based CBCT reconstruction method which enabled performing reconstruction on a multi-GPU platform. The achieved efficiency made this method clinically attractive.

  12. Impact of iterative reconstruction on CT coronary calcium quantification

    DEFF Research Database (Denmark)

    Kurata, Akira; Dharampal, Anoeshka; Dedic, Admir

    2013-01-01

    We evaluated the influence of sinogram-affirmed iterative reconstruction (SAFIRE) on the coronary artery calcium (CAC) score by computed tomography (CT).......We evaluated the influence of sinogram-affirmed iterative reconstruction (SAFIRE) on the coronary artery calcium (CAC) score by computed tomography (CT)....

  13. Iterative CT reconstruction via minimizing adaptively reweighted total variation.

    Science.gov (United States)

    Zhu, Lei; Niu, Tianye; Petrongolo, Michael

    2014-01-01

    Iterative reconstruction via total variation (TV) minimization has demonstrated great successes in accurate CT imaging from under-sampled projections. When projections are further reduced, over-smoothing artifacts appear in the current reconstruction especially around the structure boundaries. We propose a practical algorithm to improve TV-minimization based CT reconstruction on very few projection data. Based on the theory of compressed sensing, the L-0 norm approach is more desirable to further reduce the projection views. To overcome the computational difficulty of the non-convex optimization of the L-0 norm, we implement an adaptive weighting scheme to approximate the solution via a series of TV minimizations for practical use in CT reconstruction. The weight on TV is initialized as uniform ones, and is automatically changed based on the gradient of the reconstructed image from the previous iteration. The iteration stops when a small difference between the weighted TV values is observed on two consecutive reconstructed images. We evaluate the proposed algorithm on both a digital phantom and a physical phantom. Using 20 equiangular projections, our method reduces reconstruction errors in the conventional TV minimization by a factor of more than 5, with improved spatial resolution. By adaptively reweighting TV in iterative CT reconstruction, we successfully further reduce the projection number for the same or better image quality.

  14. Simulation and track reconstruction for beam telescopes

    CERN Document Server

    Maqbool, Salman

    2017-01-01

    Beam telescopes are used for testing new detectors under development. Sensors are placed and a particle beam is passed through them. To test these novel detectors and determine their properties, the particle tracks need to be reconstructed from the known detectors in the telescope. Based on the reconstructed track, it’s predicted hits on the Device under Test (DUT) are compared with the actual hits on the DUT. Several methods exist for track reconstruction, but most of them don’t account for the effects of multiple scattering. General Broken Lines is one such algorithm which incorporates these effects during reconstruction. The aim of this project was to simulate the beam telescope and extend the track reconstruction framework for the FE-I4 telescope, which takes these effects into account. Section 1 introduces the problem, while section 2 focuses on beam telescopes. This is followed by the Allpix2 simulation framework in Section 3. And finally, Section 4 introduces the Proteus track reconstruction framew...

  15. Simulation and Track Reconstruction for Beam Telescopes

    CERN Document Server

    Maqbool, Salman

    2017-01-01

    Beam telescopes are an important tool to test new detectors under development in a particle beam. To test these novel detectors and determine their properties, the particle tracks need to be reconstructed from the known detectors in the telescope. Based on the reconstructed track, its predicted position on the Device under Test (DUT) are compared with the actual hits on the DUT. Several methods exist for track reconstruction, but most of them do not account for the effects of multiple scattering. General Broken Lines is one such algorithm which incorporates these effects during reconstruction. The aim of this project was to simulate the beam telescope and extend the track reconstruction framework for the FE-I4 telescope, which takes these effects into account. Section 1 introduces the problem, while section 2 focuses on beam telescopes. This is followed by the Allpix2 simulation framework in Section 3. And finally, Section 4 introduces the Proteus track reconstruction framework along with the General Broken ...

  16. Cone-beam volume CT mammographic imaging: feasibility study

    Science.gov (United States)

    Chen, Biao; Ning, Ruola

    2001-06-01

    X-ray projection mammography, using a film/screen combination or digital techniques, has proven to be the most effective imaging modality for early detection of breast cancer currently available. However, the inherent superimposition of structures makes small carcinoma (a few millimeters in size) difficult to detect in the occultation case or in dense breasts, resulting in a high false positive biopsy rate. The cone-beam x-ray projection based volume imaging using flat panel detectors (FPDs) makes it possible to obtain three-dimensional breast images. This may benefit diagnosis of the structure and pattern of the lesion while eliminating hard compression of the breast. This paper presents a novel cone-beam volume CT mammographic imaging protocol based on the above techniques. Through computer simulation, the key issues of the system and imaging techniques, including the x-ray imaging geometry and corresponding reconstruction algorithms, x-ray characteristics of breast tissues, x-ray setting techniques, the absorbed dose estimation and the quantitative effect of x-ray scattering on image quality, are addressed. The preliminary simulation results support the proposed cone-beam volume CT mammographic imaging modality in respect to feasibility and practicability for mammography. The absorbed dose level is comparable to that of current two-view mammography and would not be a prominent problem for this imaging protocol. Compared to traditional mammography, the proposed imaging protocol with isotropic spatial resolution will potentially provide significantly better low contrast detectability of breast tumors and more accurate location of breast lesions.

  17. Reduction of Cone-Beam CT scan time without compromising the accuracy of the image registration in IGRT

    International Nuclear Information System (INIS)

    Westberg, Jonas; Jensen, Henrik R.; Bertelsen, Anders; Brink, Carsten

    2010-01-01

    Background. In modern radiotherapy accelerators are equipped with 3D cone-beam CT (CBCT) which is used to verify patient position before treatment. The verification is based on an image registration between the CBCT acquired just before treatment and the CT scan made for the treatment planning. The purpose of this study is to minimise the scan time of the CBCT without compromising the accuracy of the image registration in IGRT. Material and methods. Fast scans were simulated by reducing the number of acquired projection images, i.e. new reconstructions based on a subset of the original projections were made. The deviation between the registrations of these new reconstructions and the original registration was measured as function of the amount of reduction. Results and Discussion. Twenty nine head and neck (HandN) and 11 stereotactic lung patients were included in the study. The mean of the registration deviation did not differ significantly from zero independently of the number of projections included in the reconstruction. Except for the smallest subset of reconstructions (10% and 25% of the original projection for the lung and HandN patients, respectively) the standard deviation of the registration differences was constant. The standard deviations were approximately 0.1 mm and 0.2 mm for the HandN and lung group, respectively. Based on these results an in-house developed solution, able to reduce the Cone-Beam CT scan time, has been implemented clinically

  18. Cone-beam and fan-beam image reconstruction algorithms based on spherical and circular harmonics

    International Nuclear Information System (INIS)

    Zeng, Gengsheng L; Gullberg, Grant T

    2004-01-01

    A cone-beam image reconstruction algorithm using spherical harmonic expansions is proposed. The reconstruction algorithm is in the form of a summation of inner products of two discrete arrays of spherical harmonic expansion coefficients at each cone-beam point of acquisition. This form is different from the common filtered backprojection algorithm and the direct Fourier reconstruction algorithm. There is no re-sampling of the data, and spherical harmonic expansions are used instead of Fourier expansions. As a special case, a new fan-beam image reconstruction algorithm is also derived in terms of a circular harmonic expansion. Computer simulation results for both cone-beam and fan-beam algorithms are presented for circular planar orbit acquisitions. The algorithms give accurate reconstructions; however, the implementation of the cone-beam reconstruction algorithm is computationally intensive. A relatively efficient algorithm is proposed for reconstructing the central slice of the image when a circular scanning orbit is used

  19. Split-Bregman-based sparse-view CT reconstruction

    Energy Technology Data Exchange (ETDEWEB)

    Vandeghinste, Bert; Vandenberghe, Stefaan [Ghent Univ. (Belgium). Medical Image and Signal Processing (MEDISIP); Goossens, Bart; Pizurica, Aleksandra; Philips, Wilfried [Ghent Univ. (Belgium). Image Processing and Interpretation Research Group (IPI); Beenhouwer, Jan de [Ghent Univ. (Belgium). Medical Image and Signal Processing (MEDISIP); Antwerp Univ., Wilrijk (Belgium). The Vision Lab; Staelens, Steven [Ghent Univ. (Belgium). Medical Image and Signal Processing (MEDISIP); Antwerp Univ., Edegem (Belgium). Molecular Imaging Centre Antwerp

    2011-07-01

    Total variation minimization has been extensively researched for image denoising and sparse view reconstruction. These methods show superior denoising performance for simple images with little texture, but result in texture information loss when applied to more complex images. It could thus be beneficial to use other regularizers within medical imaging. We propose a general regularization method, based on a split-Bregman approach. We show results for this framework combined with a total variation denoising operator, in comparison to ASD-POCS. We show that sparse-view reconstruction and noise regularization is possible. This general method will allow us to investigate other regularizers in the context of regularized CT reconstruction, and decrease the acquisition times in {mu}CT. (orig.)

  20. 3-D image reconstruction in radiology

    International Nuclear Information System (INIS)

    Grangeat, P.

    1999-01-01

    In this course, we present highlights on fully 3-D image reconstruction algorithms used in 3-D X-ray Computed Tomography (3-D-CT) and 3-D Rotational Radiography (3-D-RR). We first consider the case of spiral CT with a one-row detector. Starting from the 2-D fan-beam inversion formula for a circular trajectory, we introduce spiral CT 3-D image reconstruction algorithm using axial interpolation for each transverse slice. In order to improve the X-ray detection efficiency and to speed the acquisition process, the future is to use multi-row detectors associated with small angle cone-beam geometry. The generalization of the 2-D fan-beam image reconstruction algorithm to cone beam defined direct inversion formula referred as Feldkamp's algorithm for a circular trajectory and Wang's algorithm for a spiral trajectory. However, large area detectors does exist such as Radiological Image Intensifiers or in a near future solid state detectors. To get a larger zoom effect, it defines a cone-beam geometry associated with a large aperture angle. For this case, we introduce indirect image reconstruction algorithm by plane re-binning in the Radon domain. We will present some results from a prototype MORPHOMETER device using the RADON reconstruction software. Lastly, we consider the special case of 3-D Rotational Digital Subtraction Angiography with a restricted number of views. We introduce constraint optimization algorithm using quadratic, entropic or half-quadratic constraints. Generalized ART (Algebraic Reconstruction Technique) iterative reconstruction algorithm can be derived from the Bregman algorithm. We present reconstructed vascular trees from a prototype MORPHOMETER device. (author)

  1. Color-coded volume rendering for three-dimensional reconstructions of CT data

    International Nuclear Information System (INIS)

    Rieker, O.; Mildenberger, P.; Thelen, M.

    1999-01-01

    Purpose: To evaluate a technique of colored three-dimensional reconstructions without segmentation. Material and methods: Color-coded volume rendered images were reconstructed from the volume data of 25 thoracic, abdominal, musculoskeletal, and vascular helical CT scans using commercial software. The CT volume rendered voxels were encoded with color in the following manner. Opacity, hue, lightness, and chroma were assigned to each of four classes defined by CT number. Color-coded reconstructions were compared to the corresponding grey-scale coded reconstructions. Results: Color-coded volume rendering enabled realistic visualization of pathologic findings when there was sufficient difference in CT density. Segmentation was necessary in some cases to demonstrate small details in a complex volume. Conclusion: Color-coded volume rendering allowed lifelike visualisation of CT volumes without the need of segmentation in most cases. (orig.) [de

  2. Optimizing the reconstruction filter in cone-beam CT to improve periodontal ligament space visualization: An in vitro study

    International Nuclear Information System (INIS)

    Houno, Yuuki; Kodera, Yoshie; Hishikawa, Toshimitsu; Naitoh, Munetaka; Mitani, Akio; Noguchi, Toshihide; Ariji, Eiichiro; Gotoh, Kenichi

    2017-01-01

    Evaluation of alveolar bone is important in the diagnosis of dental diseases. The periodontal ligament space is difficult to clearly depict in cone-beam computed tomography images because the reconstruction filter conditions during image processing cause image blurring, resulting in decreased spatial resolution. We examined different reconstruction filters to assess their ability to improve spatial resolution and allow for a clearer visualization of the periodontal ligament space. Cone-beam computed tomography projections of 2 skull phantoms were reconstructed using 6 reconstruction conditions and then compared using the Thurstone paired comparison method. Physical evaluations, including the modulation transfer function and the Wiener spectrum, as well as an assessment of space visibility, were undertaken using experimental phantoms. Image reconstruction using a modified Shepp-Logan filter resulted in better sensory, physical, and quantitative evaluations. The reconstruction conditions substantially improved the spatial resolution and visualization of the periodontal ligament space. The difference in sensitivity was obtained by altering the reconstruction filter. Modifying the characteristics of a reconstruction filter can generate significant improvement in assessments of the periodontal ligament space. A high-frequency enhancement filter improves the visualization of thin structures and will be useful when accurate assessment of the periodontal ligament space is necessary

  3. Optimizing the reconstruction filter in cone-beam CT to improve periodontal ligament space visualization: An in vitro study

    Energy Technology Data Exchange (ETDEWEB)

    Houno, Yuuki; Kodera, Yoshie [Graduate School of Medicine, Nagoya University, Nagoya (Japan); Hishikawa, Toshimitsu; Naitoh, Munetaka; Mitani, Akio; Noguchi, Toshihide; Ariji, Eiichiro [Aichi Gakuin University, Nisshin (Japan); Gotoh, Kenichi [Div. of Radiology, Dental Hospital, Aichi Gakuin University, Nisshin (Japan)

    2017-09-15

    Evaluation of alveolar bone is important in the diagnosis of dental diseases. The periodontal ligament space is difficult to clearly depict in cone-beam computed tomography images because the reconstruction filter conditions during image processing cause image blurring, resulting in decreased spatial resolution. We examined different reconstruction filters to assess their ability to improve spatial resolution and allow for a clearer visualization of the periodontal ligament space. Cone-beam computed tomography projections of 2 skull phantoms were reconstructed using 6 reconstruction conditions and then compared using the Thurstone paired comparison method. Physical evaluations, including the modulation transfer function and the Wiener spectrum, as well as an assessment of space visibility, were undertaken using experimental phantoms. Image reconstruction using a modified Shepp-Logan filter resulted in better sensory, physical, and quantitative evaluations. The reconstruction conditions substantially improved the spatial resolution and visualization of the periodontal ligament space. The difference in sensitivity was obtained by altering the reconstruction filter. Modifying the characteristics of a reconstruction filter can generate significant improvement in assessments of the periodontal ligament space. A high-frequency enhancement filter improves the visualization of thin structures and will be useful when accurate assessment of the periodontal ligament space is necessary.

  4. Accelerating statistical image reconstruction algorithms for fan-beam x-ray CT using cloud computing

    Science.gov (United States)

    Srivastava, Somesh; Rao, A. Ravishankar; Sheinin, Vadim

    2011-03-01

    Statistical image reconstruction algorithms potentially offer many advantages to x-ray computed tomography (CT), e.g. lower radiation dose. But, their adoption in practical CT scanners requires extra computation power, which is traditionally provided by incorporating additional computing hardware (e.g. CPU-clusters, GPUs, FPGAs etc.) into a scanner. An alternative solution is to access the required computation power over the internet from a cloud computing service, which is orders-of-magnitude more cost-effective. This is because users only pay a small pay-as-you-go fee for the computation resources used (i.e. CPU time, storage etc.), and completely avoid purchase, maintenance and upgrade costs. In this paper, we investigate the benefits and shortcomings of using cloud computing for statistical image reconstruction. We parallelized the most time-consuming parts of our application, the forward and back projectors, using MapReduce, the standard parallelization library on clouds. From preliminary investigations, we found that a large speedup is possible at a very low cost. But, communication overheads inside MapReduce can limit the maximum speedup, and a better MapReduce implementation might become necessary in the future. All the experiments for this paper, including development and testing, were completed on the Amazon Elastic Compute Cloud (EC2) for less than $20.

  5. A user-friendly nano-CT image alignment and 3D reconstruction platform based on LabVIEW

    International Nuclear Information System (INIS)

    Wang Shenghao; Wang Zhili; Gao Kun; Wu Zhao; Zhang Kai; Zhu Peiping; Wu Ziyu

    2015-01-01

    X-ray computed tomography at the nanometer scale (nano-CT) offers a wide range of applications in scientific and industrial areas. Here we describe a reliable, user-friendly, and fast software package based on LabVIEW that may allow us to perform all procedures after the acquisition of raw projection images in order to obtain the inner structure of the investigated sample. A suitable image alignment process to address misalignment problems among image series due to mechanical manufacturing errors, thermal expansion, and other external factors has been considered, together with a novel fast parallel beam 3D reconstruction procedure that was developed ad hoc to perform the tomographic reconstruction. We have obtained remarkably improved reconstruction results at the Beijing Synchrotron Radiation Facility after the image calibration, the fundamental role of this image alignment procedure was confirmed, which minimizes the unwanted blurs and additional streaking artifacts that are always present in reconstructed slices. Moreover, this nano-CT image alignment and its associated 3D reconstruction procedure are fully based on LabVIEW routines, significantly reducing the data post-processing cycle, thus making the activity of the users faster and easier during experimental runs. (authors)

  6. Model-based iterative reconstruction for reduction of radiation dose in abdominopelvic CT: comparison to adaptive statistical iterative reconstruction.

    Science.gov (United States)

    Yasaka, Koichiro; Katsura, Masaki; Akahane, Masaaki; Sato, Jiro; Matsuda, Izuru; Ohtomo, Kuni

    2013-12-01

    To evaluate dose reduction and image quality of abdominopelvic computed tomography (CT) reconstructed with model-based iterative reconstruction (MBIR) compared to adaptive statistical iterative reconstruction (ASIR). In this prospective study, 85 patients underwent referential-, low-, and ultralow-dose unenhanced abdominopelvic CT. Images were reconstructed with ASIR for low-dose (L-ASIR) and ultralow-dose CT (UL-ASIR), and with MBIR for ultralow-dose CT (UL-MBIR). Image noise was measured in the abdominal aorta and iliopsoas muscle. Subjective image analyses and a lesion detection study (adrenal nodules) were conducted by two blinded radiologists. A reference standard was established by a consensus panel of two different radiologists using referential-dose CT reconstructed with filtered back projection. Compared to low-dose CT, there was a 63% decrease in dose-length product with ultralow-dose CT. UL-MBIR had significantly lower image noise than L-ASIR and UL-ASIR (all pASIR and UL-ASIR (all pASIR in diagnostic acceptability (p>0.65), or diagnostic performance for adrenal nodules (p>0.87). MBIR significantly improves image noise and streak artifacts compared to ASIR, and can achieve radiation dose reduction without severely compromising image quality.

  7. Physical performance and image optimization of megavoltage cone-beam CT

    Energy Technology Data Exchange (ETDEWEB)

    Morin, Olivier; Aubry, Jean-Francois; Aubin, Michele; Chen, Josephine; Descovich, Martina; Hashemi, Ali-Bani; Pouliot, Jean [Department of Radiation Oncology, Helen Diller Comprehensive Cancer Center, University of California San Francisco, San Francisco, California 94143 and UCSF/UC Berkeley Joint Graduate Group in Bioengineering, San Francisco, California 94158 (United States); Department of Radiation Oncology, Helen Diller Comprehensive Cancer Center, University of California San Francisco, San Francisco, California 94143 (United States); Siemens Oncology Care Systems, Concord, California 94520 (United States); Department of Radiation Oncology, Helen Diller Comprehensive Cancer Center, University of California San Francisco, San Francisco, California 94143 and UCSF/UC Berkeley Joint Graduate Group in Bioengineering, San Francisco, California 94158 (United States)

    2009-04-15

    Megavoltage cone-beam CT (MVCBCT) is the most recent addition to the in-room CT systems developed for image-guided radiation therapy. The first generation MVCBCT system consists of a 6 MV treatment x-ray beam produced by a conventional linear accelerator equipped with a flat panel amorphous silicon detector. The objective of this study was to evaluate the physical performance of MVCBCT in order to optimize the system acquisition and reconstruction parameters for image quality. MVCBCT acquisitions were performed with the clinical system but images were reconstructed and analyzed with a separate research workstation. The geometrical stability and the positioning accuracy of the system were evaluated by comparing geometrical calibrations routinely performed over a period of 12 months. The beam output and detector intensity stability during MVCBCT acquisition were also evaluated by analyzing in-air acquisitions acquired at different exposure levels. Several system parameters were varied to quantify their impact on image quality including the exposure (2.7, 4.5, 9.0, 18.0, and 54.0 MU), the craniocaudal imaging length (2, 5, 15, and 27.4 cm), the voxel size (0.5, 1, and 2 mm), the slice thickness (1, 3, and 5 mm), and the phantom size. For the reconstruction algorithm, the study investigated the effect of binning, averaging and diffusion filtering of raw projections as well as three different projection filters. A head-sized water cylinder was used to measure and improve the uniformity of MVCBCT images. Inserts of different electron densities were placed in a water cylinder to measure the contrast-to-noise ratio (CNR). The spatial resolution was obtained by measuring the point-spread function of the system using an iterative edge blurring technique. Our results showed that the geometric stability and accuracy of MVCBCT were better than 1 mm over a period of 12 months. Beam intensity variations per projection of up to 35.4% were observed for a 2.7 MU MVCBCT acquisition

  8. CT reconstruction techniques for improved accuracy of lung CT airway measurement

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez, A. [Department of Medical Physics, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin 53705 (United States); Ranallo, F. N. [Department of Medical Physics, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin 53705 and Department of Radiology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin 53792 (United States); Judy, P. F. [Brigham and Women’s Hospital, Boston, Massachusetts 02115 (United States); Gierada, D. S. [Department of Radiology, Washington University, St. Louis, Missouri 63110 (United States); Fain, S. B., E-mail: sfain@wisc.edu [Department of Medical Physics, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin 53705 (United States); Department of Radiology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin 53792 (United States); Department of Biomedical Engineering,University of Wisconsin School of Engineering, Madison, Wisconsin 53706 (United States)

    2014-11-01

    Purpose: To determine the impact of constrained reconstruction techniques on quantitative CT (qCT) of the lung parenchyma and airways for low x-ray radiation dose. Methods: Measurement of small airways with qCT remains a challenge, especially for low x-ray dose protocols. Images of the COPDGene quality assurance phantom (CTP698, The Phantom Laboratory, Salem, NY) were obtained using a GE discovery CT750 HD scanner for helical scans at x-ray radiation dose-equivalents ranging from 1 to 4.12 mSv (12–100 mA s current–time product). Other parameters were 40 mm collimation, 0.984 pitch, 0.5 s rotation, and 0.625 mm thickness. The phantom was sandwiched between 7.5 cm thick water attenuating phantoms for a total length of 20 cm to better simulate the scatter conditions of patient scans. Image data sets were reconstructed using STANDARD (STD), DETAIL, BONE, and EDGE algorithms for filtered back projection (FBP), 100% adaptive statistical iterative reconstruction (ASIR), and Veo reconstructions. Reduced (half) display field of view (DFOV) was used to increase sampling across airway phantom structures. Inner diameter (ID), wall area percent (WA%), and wall thickness (WT) measurements of eight airway mimicking tubes in the phantom, including a 2.5 mm ID (42.6 WA%, 0.4 mm WT), 3 mm ID (49.0 WA%, 0.6 mm WT), and 6 mm ID (49.0 WA%, 1.2 mm WT) were performed with Airway Inspector (Surgical Planning Laboratory, Brigham and Women’s Hospital, Boston, MA) using the phase congruency edge detection method. The average of individual measures at five central slices of the phantom was taken to reduce measurement error. Results: WA% measures were greatly overestimated while IDs were underestimated for the smaller airways, especially for reconstructions at full DFOV (36 cm) using the STD kernel, due to poor sampling and spatial resolution (0.7 mm pixel size). Despite low radiation dose, the ID of the 6 mm ID airway was consistently measured accurately for all methods other than STD

  9. CT reconstruction techniques for improved accuracy of lung CT airway measurement

    International Nuclear Information System (INIS)

    Rodriguez, A.; Ranallo, F. N.; Judy, P. F.; Gierada, D. S.; Fain, S. B.

    2014-01-01

    Purpose: To determine the impact of constrained reconstruction techniques on quantitative CT (qCT) of the lung parenchyma and airways for low x-ray radiation dose. Methods: Measurement of small airways with qCT remains a challenge, especially for low x-ray dose protocols. Images of the COPDGene quality assurance phantom (CTP698, The Phantom Laboratory, Salem, NY) were obtained using a GE discovery CT750 HD scanner for helical scans at x-ray radiation dose-equivalents ranging from 1 to 4.12 mSv (12–100 mA s current–time product). Other parameters were 40 mm collimation, 0.984 pitch, 0.5 s rotation, and 0.625 mm thickness. The phantom was sandwiched between 7.5 cm thick water attenuating phantoms for a total length of 20 cm to better simulate the scatter conditions of patient scans. Image data sets were reconstructed using STANDARD (STD), DETAIL, BONE, and EDGE algorithms for filtered back projection (FBP), 100% adaptive statistical iterative reconstruction (ASIR), and Veo reconstructions. Reduced (half) display field of view (DFOV) was used to increase sampling across airway phantom structures. Inner diameter (ID), wall area percent (WA%), and wall thickness (WT) measurements of eight airway mimicking tubes in the phantom, including a 2.5 mm ID (42.6 WA%, 0.4 mm WT), 3 mm ID (49.0 WA%, 0.6 mm WT), and 6 mm ID (49.0 WA%, 1.2 mm WT) were performed with Airway Inspector (Surgical Planning Laboratory, Brigham and Women’s Hospital, Boston, MA) using the phase congruency edge detection method. The average of individual measures at five central slices of the phantom was taken to reduce measurement error. Results: WA% measures were greatly overestimated while IDs were underestimated for the smaller airways, especially for reconstructions at full DFOV (36 cm) using the STD kernel, due to poor sampling and spatial resolution (0.7 mm pixel size). Despite low radiation dose, the ID of the 6 mm ID airway was consistently measured accurately for all methods other than STD

  10. CT of the chest with model-based, fully iterative reconstruction: comparison with adaptive statistical iterative reconstruction.

    Science.gov (United States)

    Ichikawa, Yasutaka; Kitagawa, Kakuya; Nagasawa, Naoki; Murashima, Shuichi; Sakuma, Hajime

    2013-08-09

    The recently developed model-based iterative reconstruction (MBIR) enables significant reduction of image noise and artifacts, compared with adaptive statistical iterative reconstruction (ASIR) and filtered back projection (FBP). The purpose of this study was to evaluate lesion detectability of low-dose chest computed tomography (CT) with MBIR in comparison with ASIR and FBP. Chest CT was acquired with 64-slice CT (Discovery CT750HD) with standard-dose (5.7 ± 2.3 mSv) and low-dose (1.6 ± 0.8 mSv) conditions in 55 patients (aged 72 ± 7 years) who were suspected of lung disease on chest radiograms. Low-dose CT images were reconstructed with MBIR, ASIR 50% and FBP, and standard-dose CT images were reconstructed with FBP, using a reconstructed slice thickness of 0.625 mm. Two observers evaluated the image quality of abnormal lung and mediastinal structures on a 5-point scale (Score 5 = excellent and score 1 = non-diagnostic). The objective image noise was also measured as the standard deviation of CT intensity in the descending aorta. The image quality score of enlarged mediastinal lymph nodes on low-dose MBIR CT (4.7 ± 0.5) was significantly improved in comparison with low-dose FBP and ASIR CT (3.0 ± 0.5, p = 0.004; 4.0 ± 0.5, p = 0.02, respectively), and was nearly identical to the score of standard-dose FBP image (4.8 ± 0.4, p = 0.66). Concerning decreased lung attenuation (bulla, emphysema, or cyst), the image quality score on low-dose MBIR CT (4.9 ± 0.2) was slightly better compared to low-dose FBP and ASIR CT (4.5 ± 0.6, p = 0.01; 4.6 ± 0.5, p = 0.01, respectively). There were no significant differences in image quality scores of visualization of consolidation or mass, ground-glass attenuation, or reticular opacity among low- and standard-dose CT series. Image noise with low-dose MBIR CT (11.6 ± 1.0 Hounsfield units (HU)) were significantly lower than with low-dose ASIR (21.1 ± 2.6 HU, p standard-dose FBP CT (16.6 ± 2.3 HU, p 70%, MBIR can provide

  11. A fast 4D cone beam CT reconstruction method based on the OSC-TV algorithm.

    Science.gov (United States)

    Mascolo-Fortin, Julia; Matenine, Dmitri; Archambault, Louis; Després, Philippe

    2018-01-01

    Four-dimensional cone beam computed tomography allows for temporally resolved imaging with useful applications in radiotherapy, but raises particular challenges in terms of image quality and computation time. The purpose of this work is to develop a fast and accurate 4D algorithm by adapting a GPU-accelerated ordered subsets convex algorithm (OSC), combined with the total variation minimization regularization technique (TV). Different initialization schemes were studied to adapt the OSC-TV algorithm to 4D reconstruction: each respiratory phase was initialized either with a 3D reconstruction or a blank image. Reconstruction algorithms were tested on a dynamic numerical phantom and on a clinical dataset. 4D iterations were implemented for a cluster of 8 GPUs. All developed methods allowed for an adequate visualization of the respiratory movement and compared favorably to the McKinnon-Bates and adaptive steepest descent projection onto convex sets algorithms, while the 4D reconstructions initialized from a prior 3D reconstruction led to better overall image quality. The most suitable adaptation of OSC-TV to 4D CBCT was found to be a combination of a prior FDK reconstruction and a 4D OSC-TV reconstruction with a reconstruction time of 4.5 minutes. This relatively short reconstruction time could facilitate a clinical use.

  12. Iterative model reconstruction: Improved image quality of low-tube-voltage prospective ECG-gated coronary CT angiography images at 256-slice CT

    Energy Technology Data Exchange (ETDEWEB)

    Oda, Seitaro, E-mail: seisei0430@nifty.com [Department of Cardiology, MedStar Washington Hospital Center, 110 Irving Street, NW, Washington, DC 20010 (United States); Department of Diagnostic Radiology, Faculty of Life Sciences, Kumamoto University, 1-1-1 Honjyo, Chuo-ku, Kumamoto, 860-8556 (Japan); Weissman, Gaby, E-mail: Gaby.Weissman@medstar.net [Department of Cardiology, MedStar Washington Hospital Center, 110 Irving Street, NW, Washington, DC 20010 (United States); Vembar, Mani, E-mail: mani.vembar@philips.com [CT Clinical Science, Philips Healthcare, c595 Miner Road, Cleveland, OH 44143 (United States); Weigold, Wm. Guy, E-mail: Guy.Weigold@MedStar.net [Department of Cardiology, MedStar Washington Hospital Center, 110 Irving Street, NW, Washington, DC 20010 (United States)

    2014-08-15

    Objectives: To investigate the effects of a new model-based type of iterative reconstruction (M-IR) technique, the iterative model reconstruction, on image quality of prospectively gated coronary CT angiography (CTA) acquired at low-tube-voltage. Methods: Thirty patients (16 men, 14 women; mean age 52.2 ± 13.2 years) underwent coronary CTA at 100-kVp on a 256-slice CT. Paired image sets were created using 3 types of reconstruction, i.e. filtered back projection (FBP), a hybrid type of iterative reconstruction (H-IR), and M-IR. Quantitative parameters including CT-attenuation, image noise, and contrast-to-noise ratio (CNR) were measured. The visual image quality, i.e. graininess, beam-hardening, vessel sharpness, and overall image quality, was scored on a 5-point scale. Lastly, coronary artery segments were evaluated using a 4-point scale to investigate the assessability of each segment. Results: There was no significant difference in coronary arterial CT attenuation among the 3 reconstruction methods. The mean image noise of FBP, H-IR, and M-IR images was 29.3 ± 9.6, 19.3 ± 6.9, and 12.9 ± 3.3 HU, respectively, there were significant differences for all comparison combinations among the 3 methods (p < 0.01). The CNR of M-IR was significantly better than of FBP and H-IR images (13.5 ± 5.0 [FBP], 20.9 ± 8.9 [H-IR] and 39.3 ± 13.9 [M-IR]; p < 0.01). The visual scores were significantly higher for M-IR than the other images (p < 0.01), and 95.3% of the coronary segments imaged with M-IR were of assessable quality compared with 76.7% of FBP- and 86.9% of H-IR images. Conclusions: M-IR can provide significantly improved qualitative and quantitative image quality in prospectively gated coronary CTA using a low-tube-voltage.

  13. Dual-energy cone-beam CT with a flat-panel detector: Effect of reconstruction algorithm on material classification

    International Nuclear Information System (INIS)

    Zbijewski, W.; Gang, G. J.; Xu, J.; Wang, A. S.; Stayman, J. W.; Taguchi, K.; Carrino, J. A.; Siewerdsen, J. H.

    2014-01-01

    Purpose: Cone-beam CT (CBCT) with a flat-panel detector (FPD) is finding application in areas such as breast and musculoskeletal imaging, where dual-energy (DE) capabilities offer potential benefit. The authors investigate the accuracy of material classification in DE CBCT using filtered backprojection (FBP) and penalized likelihood (PL) reconstruction and optimize contrast-enhanced DE CBCT of the joints as a function of dose, material concentration, and detail size. Methods: Phantoms consisting of a 15 cm diameter water cylinder with solid calcium inserts (50–200 mg/ml, 3–28.4 mm diameter) and solid iodine inserts (2–10 mg/ml, 3–28.4 mm diameter), as well as a cadaveric knee with intra-articular injection of iodine were imaged on a CBCT bench with a Varian 4343 FPD. The low energy (LE) beam was 70 kVp (+0.2 mm Cu), and the high energy (HE) beam was 120 kVp (+0.2 mm Cu, +0.5 mm Ag). Total dose (LE+HE) was varied from 3.1 to 15.6 mGy with equal dose allocation. Image-based DE classification involved a nearest distance classifier in the space of LE versus HE attenuation values. Recognizing the differences in noise between LE and HE beams, the LE and HE data were differentially filtered (in FBP) or regularized (in PL). Both a quadratic (PLQ) and a total-variation penalty (PLTV) were investigated for PL. The performance of DE CBCT material discrimination was quantified in terms of voxelwise specificity, sensitivity, and accuracy. Results: Noise in the HE image was primarily responsible for classification errors within the contrast inserts, whereas noise in the LE image mainly influenced classification in the surrounding water. For inserts of diameter 28.4 mm, DE CBCT reconstructions were optimized to maximize the total combined accuracy across the range of calcium and iodine concentrations, yielding values of ∼88% for FBP and PLQ, and ∼95% for PLTV at 3.1 mGy total dose, increasing to ∼95% for FBP and PLQ, and ∼98% for PLTV at 15.6 mGy total dose. For a

  14. WE-G-18A-04: 3D Dictionary Learning Based Statistical Iterative Reconstruction for Low-Dose Cone Beam CT Imaging

    International Nuclear Information System (INIS)

    Bai, T; Yan, H; Shi, F; Jia, X; Jiang, Steve B.; Lou, Y; Xu, Q; Mou, X

    2014-01-01

    Purpose: To develop a 3D dictionary learning based statistical reconstruction algorithm on graphic processing units (GPU), to improve the quality of low-dose cone beam CT (CBCT) imaging with high efficiency. Methods: A 3D dictionary containing 256 small volumes (atoms) of 3x3x3 voxels was trained from a high quality volume image. During reconstruction, we utilized a Cholesky decomposition based orthogonal matching pursuit algorithm to find a sparse representation on this dictionary basis of each patch in the reconstructed image, in order to regularize the image quality. To accelerate the time-consuming sparse coding in the 3D case, we implemented our algorithm in a parallel fashion by taking advantage of the tremendous computational power of GPU. Evaluations are performed based on a head-neck patient case. FDK reconstruction with full dataset of 364 projections is used as the reference. We compared the proposed 3D dictionary learning based method with a tight frame (TF) based one using a subset data of 121 projections. The image qualities under different resolutions in z-direction, with or without statistical weighting are also studied. Results: Compared to the TF-based CBCT reconstruction, our experiments indicated that 3D dictionary learning based CBCT reconstruction is able to recover finer structures, to remove more streaking artifacts, and is less susceptible to blocky artifacts. It is also observed that statistical reconstruction approach is sensitive to inconsistency between the forward and backward projection operations in parallel computing. Using high a spatial resolution along z direction helps improving the algorithm robustness. Conclusion: 3D dictionary learning based CBCT reconstruction algorithm is able to sense the structural information while suppressing noise, and hence to achieve high quality reconstruction. The GPU realization of the whole algorithm offers a significant efficiency enhancement, making this algorithm more feasible for potential

  15. WE-G-18A-04: 3D Dictionary Learning Based Statistical Iterative Reconstruction for Low-Dose Cone Beam CT Imaging

    Energy Technology Data Exchange (ETDEWEB)

    Bai, T [Xi' an Jiaotong University, Xi' an (China); UT Southwestern Medical Center, Dallas, TX (United States); Yan, H; Shi, F; Jia, X; Jiang, Steve B. [UT Southwestern Medical Center, Dallas, TX (United States); Lou, Y [University of California Irvine, Irvine, CA (United States); Xu, Q; Mou, X [Xi' an Jiaotong University, Xi' an (China)

    2014-06-15

    Purpose: To develop a 3D dictionary learning based statistical reconstruction algorithm on graphic processing units (GPU), to improve the quality of low-dose cone beam CT (CBCT) imaging with high efficiency. Methods: A 3D dictionary containing 256 small volumes (atoms) of 3x3x3 voxels was trained from a high quality volume image. During reconstruction, we utilized a Cholesky decomposition based orthogonal matching pursuit algorithm to find a sparse representation on this dictionary basis of each patch in the reconstructed image, in order to regularize the image quality. To accelerate the time-consuming sparse coding in the 3D case, we implemented our algorithm in a parallel fashion by taking advantage of the tremendous computational power of GPU. Evaluations are performed based on a head-neck patient case. FDK reconstruction with full dataset of 364 projections is used as the reference. We compared the proposed 3D dictionary learning based method with a tight frame (TF) based one using a subset data of 121 projections. The image qualities under different resolutions in z-direction, with or without statistical weighting are also studied. Results: Compared to the TF-based CBCT reconstruction, our experiments indicated that 3D dictionary learning based CBCT reconstruction is able to recover finer structures, to remove more streaking artifacts, and is less susceptible to blocky artifacts. It is also observed that statistical reconstruction approach is sensitive to inconsistency between the forward and backward projection operations in parallel computing. Using high a spatial resolution along z direction helps improving the algorithm robustness. Conclusion: 3D dictionary learning based CBCT reconstruction algorithm is able to sense the structural information while suppressing noise, and hence to achieve high quality reconstruction. The GPU realization of the whole algorithm offers a significant efficiency enhancement, making this algorithm more feasible for potential

  16. Volume-of-change cone-beam CT for image-guided surgery

    International Nuclear Information System (INIS)

    Lee, Junghoon; Stayman, J Webster; Otake, Yoshito; Schafer, Sebastian; Zbijewski, Wojciech; Khanna, A Jay; Siewerdsen, Jeffrey H; Prince, Jerry L

    2012-01-01

    C-arm cone-beam CT (CBCT) can provide intraoperative 3D imaging capability for surgical guidance, but workflow and radiation dose are the significant barriers to broad utilization. One main reason is that each 3D image acquisition requires a complete scan with a full radiation dose to present a completely new 3D image every time. In this paper, we propose to utilize patient-specific CT or CBCT as prior knowledge to accurately reconstruct the aspects of the region that have changed by the surgical procedure from only a sparse set of x-rays. The proposed methods consist of a 3D–2D registration between the prior volume and a sparse set of intraoperative x-rays, creating digitally reconstructed radiographs (DRRs) from the registered prior volume, computing difference images by subtracting DRRs from the intraoperative x-rays, a penalized likelihood reconstruction of the volume of change (VOC) from the difference images, and finally a fusion of VOC reconstruction with the prior volume to visualize the entire surgical field. When the surgical changes are local and relatively small, the VOC reconstruction involves only a small volume size and a small number of projections, allowing less computation and lower radiation dose than is needed to reconstruct the entire surgical field. We applied this approach to sacroplasty phantom data obtained from a CBCT test bench and vertebroplasty data with a fresh cadaver acquired from a C-arm CBCT system with a flat-panel detector. The VOCs were reconstructed from a varying number of images (10–66 images) and compared to the CBCT ground truth using four different metrics (mean squared error, correlation coefficient, structural similarity index and perceptual difference model). The results show promising reconstruction quality with structural similarity to the ground truth close to 1 even when only 15–20 images were used, allowing dose reduction by the factor of 10–20. (paper)

  17. WE-FG-207B-12: Quantitative Evaluation of a Spectral CT Scanner in a Phantom Study: Results of Spectral Reconstructions

    International Nuclear Information System (INIS)

    Duan, X; Arbique, G; Guild, J; Anderson, J; Yagil, Y

    2016-01-01

    Purpose: To evaluate the quantitative image quality of spectral reconstructions of phantom data from a spectral CT scanner. Methods: The spectral CT scanner (IQon Spectral CT, Philips Healthcare) is equipped with a dual-layer detector and generates conventional 80-140 kVp images and variety of spectral reconstructions, e.g., virtual monochromatic (VM) images, virtual non-contrast (VNC) images, iodine maps, and effective atomic number (Z) images. A cylindrical solid water phantom (Gammex 472, 33 cm diameter and 5 cm thick) with iodine (2.0-20.0 mg I/ml) and calcium (50-600 mg/ml) rod inserts was scanned at 120 kVp and 27 mGy CTDIvol. Spectral reconstructions were evaluated by comparing image measurements with theoretical values calculated from nominal rod compositions provided by the phantom manufacturer. The theoretical VNC was calculated using water and iodine basis material decomposition, and the theoretical Z was calculated using two common methods, the chemical formula method (Z1) and the dual-energy ratio method (Z2). Results: Beam-hardening-like artifacts between high-attenuation calcium rods (≥300 mg/ml, >800 HU) influenced quantitative measurements, so the quantitative analysis was only performed on iodine rods using the images from the scan with all the calcium rods removed. The CT numbers of the iodine rods in the VM images (50∼150 keV) were close to theoretical values with average difference of 2.4±6.9 HU. Compared with theoretical values, the average difference for iodine concentration, VNC CT number and effective Z of iodine rods were −0.10±0.38 mg/ml, −0.1±8.2 HU, 0.25±0.06 (Z1) and −0.23±0.07 (Z2). Conclusion: The results indicate that the spectral CT scanner generates quantitatively accurate spectral reconstructions at clinically relevant iodine concentrations. Beam-hardening-like artifacts still exist when high-attenuation objects are present and their impact on patient images needs further investigation. YY is an employee of Philips

  18. WE-FG-207B-12: Quantitative Evaluation of a Spectral CT Scanner in a Phantom Study: Results of Spectral Reconstructions

    Energy Technology Data Exchange (ETDEWEB)

    Duan, X; Arbique, G; Guild, J; Anderson, J [UT Southwestern Medical Center, Dallas, TX (United States); Yagil, Y [Philips Healthcare, Haifa (Israel)

    2016-06-15

    Purpose: To evaluate the quantitative image quality of spectral reconstructions of phantom data from a spectral CT scanner. Methods: The spectral CT scanner (IQon Spectral CT, Philips Healthcare) is equipped with a dual-layer detector and generates conventional 80-140 kVp images and variety of spectral reconstructions, e.g., virtual monochromatic (VM) images, virtual non-contrast (VNC) images, iodine maps, and effective atomic number (Z) images. A cylindrical solid water phantom (Gammex 472, 33 cm diameter and 5 cm thick) with iodine (2.0-20.0 mg I/ml) and calcium (50-600 mg/ml) rod inserts was scanned at 120 kVp and 27 mGy CTDIvol. Spectral reconstructions were evaluated by comparing image measurements with theoretical values calculated from nominal rod compositions provided by the phantom manufacturer. The theoretical VNC was calculated using water and iodine basis material decomposition, and the theoretical Z was calculated using two common methods, the chemical formula method (Z1) and the dual-energy ratio method (Z2). Results: Beam-hardening-like artifacts between high-attenuation calcium rods (≥300 mg/ml, >800 HU) influenced quantitative measurements, so the quantitative analysis was only performed on iodine rods using the images from the scan with all the calcium rods removed. The CT numbers of the iodine rods in the VM images (50∼150 keV) were close to theoretical values with average difference of 2.4±6.9 HU. Compared with theoretical values, the average difference for iodine concentration, VNC CT number and effective Z of iodine rods were −0.10±0.38 mg/ml, −0.1±8.2 HU, 0.25±0.06 (Z1) and −0.23±0.07 (Z2). Conclusion: The results indicate that the spectral CT scanner generates quantitatively accurate spectral reconstructions at clinically relevant iodine concentrations. Beam-hardening-like artifacts still exist when high-attenuation objects are present and their impact on patient images needs further investigation. YY is an employee of Philips

  19. Optimization of SPECT-CT Hybrid Imaging Using Iterative Image Reconstruction for Low-Dose CT: A Phantom Study.

    Directory of Open Access Journals (Sweden)

    Oliver S Grosser

    Full Text Available Hybrid imaging combines nuclear medicine imaging such as single photon emission computed tomography (SPECT or positron emission tomography (PET with computed tomography (CT. Through this hybrid design, scanned patients accumulate radiation exposure from both applications. Imaging modalities have been the subject of long-term optimization efforts, focusing on diagnostic applications. It was the aim of this study to investigate the influence of an iterative CT image reconstruction algorithm (ASIR on the image quality of the low-dose CT images.Examinations were performed with a SPECT-CT scanner with standardized CT and SPECT-phantom geometries and CT protocols with systematically reduced X-ray tube currents. Analyses included image quality with respect to photon flux. Results were compared to the standard FBP reconstructed images. The general impact of the CT-based attenuation maps used during SPECT reconstruction was examined for two SPECT phantoms. Using ASIR for image reconstructions, image noise was reduced compared to FBP reconstructions for the same X-ray tube current. The Hounsfield unit (HU values reconstructed by ASIR were correlated to the FBP HU values(R2 ≥ 0.88 and the contrast-to-noise ratio (CNR was improved by ASIR. However, for a phantom with increased attenuation, the HU values shifted for low X-ray tube currents I ≤ 60 mA (p ≤ 0.04. In addition, the shift of the HU values was observed within the attenuation corrected SPECT images for very low X-ray tube currents (I ≤ 20 mA, p ≤ 0.001.In general, the decrease in X-ray tube current up to 30 mA in combination with ASIR led to a reduction of CT-related radiation exposure without a significant decrease in image quality.

  20. Diagnostic value of 3 D CT surface reconstruction in spinal fractures

    Energy Technology Data Exchange (ETDEWEB)

    Koesling, S. [Department of Radiology, Univ. of Leipzig (Germany); Dietrich, K. [Department of Radiology, Univ. of Leipzig (Germany); Steinecke, R. [Department of Radiology, Univ. of Leipzig (Germany); Kloeppel, R. [Department of Radiology, Univ. of Leipzig (Germany); Schulz, H.G. [Department of Radiology, Univ. of Leipzig (Germany)

    1997-02-01

    Our purpose was to evaluate the diagnostic value of three-dimensional (3 D) CT surface reconstruction in spinal fractures in comparison with axial and reformatted images. A total of 50 patients with different CT-proven spinal fractures were analysed retrospectively. Based on axial scans and reformatted images, the spinal fractures were classified according to several classifications as Magerl for the thoraco-lumbar and lower cervical spine by one radiologist. Another radiologist performed 3 D CT surface reconstructions with the aim of characterizing the different types of spinal fractures. A third radiologist classified the 3 D CT surface reconstruction according to the Magerl classification. The results of the blinded reading process were compared. It was checked to see in which type and subgroup 3 D surface reconstructions were helpful. Readers one and two obtained the same results in the classification. The 3 D surface reconstruction did not yield any additional diagnostic information concerning type A and B injuries. Indeed, the full extent of the fracture could be easier recognized with axial and reformatted images in all cases. In 10 cases of C injuries, the dislocation of parts of vertebrae could be better recognized with the help of 3 D reconstructions. A 3 D CT surface reconstruction is only useful in rotational and shear vertebral injuries (Magerl type C injury). (orig.). With 4 figs., 1 tab.

  1. Iterative Reconstruction Techniques in Abdominopelvic CT: Technical Concepts and Clinical Implementation.

    Science.gov (United States)

    Patino, Manuel; Fuentes, Jorge M; Singh, Sarabjeet; Hahn, Peter F; Sahani, Dushyant V

    2015-07-01

    This article discusses the clinical challenge of low-radiation-dose examinations, the commonly used approaches for dose optimization, and their effect on image quality. We emphasize practical aspects of the different iterative reconstruction techniques, along with their benefits, pitfalls, and clinical implementation. The widespread use of CT has raised concerns about potential radiation risks, motivating diverse strategies to reduce the radiation dose associated with CT. CT manufacturers have developed alternative reconstruction algorithms intended to improve image quality on dose-optimized CT studies, mainly through noise and artifact reduction. Iterative reconstruction techniques take unique approaches to noise reduction and provide distinct strength levels or settings.

  2. A deep convolutional neural network using directional wavelets for low-dose X-ray CT reconstruction.

    Science.gov (United States)

    Kang, Eunhee; Min, Junhong; Ye, Jong Chul

    2017-10-01

    Due to the potential risk of inducing cancer, radiation exposure by X-ray CT devices should be reduced for routine patient scanning. However, in low-dose X-ray CT, severe artifacts typically occur due to photon starvation, beam hardening, and other causes, all of which decrease the reliability of the diagnosis. Thus, a high-quality reconstruction method from low-dose X-ray CT data has become a major research topic in the CT community. Conventional model-based de-noising approaches are, however, computationally very expensive, and image-domain de-noising approaches cannot readily remove CT-specific noise patterns. To tackle these problems, we want to develop a new low-dose X-ray CT algorithm based on a deep-learning approach. We propose an algorithm which uses a deep convolutional neural network (CNN) which is applied to the wavelet transform coefficients of low-dose CT images. More specifically, using a directional wavelet transform to extract the directional component of artifacts and exploit the intra- and inter- band correlations, our deep network can effectively suppress CT-specific noise. In addition, our CNN is designed with a residual learning architecture for faster network training and better performance. Experimental results confirm that the proposed algorithm effectively removes complex noise patterns from CT images derived from a reduced X-ray dose. In addition, we show that the wavelet-domain CNN is efficient when used to remove noise from low-dose CT compared to existing approaches. Our results were rigorously evaluated by several radiologists at the Mayo Clinic and won second place at the 2016 "Low-Dose CT Grand Challenge." To the best of our knowledge, this work is the first deep-learning architecture for low-dose CT reconstruction which has been rigorously evaluated and proven to be effective. In addition, the proposed algorithm, in contrast to existing model-based iterative reconstruction (MBIR) methods, has considerable potential to benefit from

  3. SU-E-I-73: Clinical Evaluation of CT Image Reconstructed Using Interior Tomography

    International Nuclear Information System (INIS)

    Zhang, J; Ge, G; Winkler, M; Cong, W; Wang, G

    2014-01-01

    Purpose: Radiation dose reduction has been a long standing challenge in CT imaging of obese patients. Recent advances in interior tomography (reconstruction of an interior region of interest (ROI) from line integrals associated with only paths through the ROI) promise to achieve significant radiation dose reduction without compromising image quality. This study is to investigate the application of this technique in CT imaging through evaluating imaging quality reconstructed from patient data. Methods: Projection data were directly obtained from patients who had CT examinations in a Dual Source CT scanner (DSCT). Two detectors in a DSCT acquired projection data simultaneously. One detector provided projection data for full field of view (FOV, 50 cm) while another detectors provided truncated projection data for a FOV of 26 cm. Full FOV CT images were reconstructed using both filtered back projection and iterative algorithm; while interior tomography algorithm was implemented to reconstruct ROI images. For comparison reason, FBP was also used to reconstruct ROI images. Reconstructed CT images were evaluated by radiologists and compared with images from CT scanner. Results: The results show that the reconstructed ROI image was in excellent agreement with the truth inside the ROI, obtained from images from CT scanner, and the detailed features in the ROI were quantitatively accurate. Radiologists evaluation shows that CT images reconstructed with interior tomography met diagnosis requirements. Radiation dose may be reduced up to 50% using interior tomography, depending on patient size. Conclusion: This study shows that interior tomography can be readily employed in CT imaging for radiation dose reduction. It may be especially useful in imaging obese patients, whose subcutaneous tissue is less clinically relevant but may significantly increase radiation dose

  4. Polyquant CT: direct electron and mass density reconstruction from a single polyenergetic source

    Science.gov (United States)

    Mason, Jonathan H.; Perelli, Alessandro; Nailon, William H.; Davies, Mike E.

    2017-11-01

    Quantifying material mass and electron density from computed tomography (CT) reconstructions can be highly valuable in certain medical practices, such as radiation therapy planning. However, uniquely parameterising the x-ray attenuation in terms of mass or electron density is an ill-posed problem when a single polyenergetic source is used with a spectrally indiscriminate detector. Existing approaches to single source polyenergetic modelling often impose consistency with a physical model, such as water-bone or photoelectric-Compton decompositions, which will either require detailed prior segmentation or restrictive energy dependencies, and may require further calibration to the quantity of interest. In this work, we introduce a data centric approach to fitting the attenuation with piecewise-linear functions directly to mass or electron density, and present a segmentation-free statistical reconstruction algorithm for exploiting it, with the same order of complexity as other iterative methods. We show how this allows both higher accuracy in attenuation modelling, and demonstrate its superior quantitative imaging, with numerical chest and metal implant data, and validate it with real cone-beam CT measurements.

  5. Computer simulation of electron beams. II. Low-cost beam-current reconstruction

    International Nuclear Information System (INIS)

    de Wolf, D.A.

    1985-01-01

    Reconstruction of current density in electron beams is complicated by distortion of phase space which can require very fine discretization of the beam into trajectories. An efficient discretization of phase space is exploited, using conservation of charge and current in hypertriangle patches, to reconstruct the current density by fitting Gaussians through the distorted hypertriangles. Advantages and limitations are discussed

  6. Three-dimensional reconstruction of CT images

    Energy Technology Data Exchange (ETDEWEB)

    Watanabe, Toshiaki; Kattoh, Keiichi; Kawakami, Genichiroh; Igami, Isao; Mariya, Yasushi; Nakamura, Yasuhiko; Saitoh, Yohko; Tamura, Koreroku; Shinozaki, Tatsuyo

    1986-09-01

    Computed tomography (CT) has the ability to provide sensitive visualization of organs and lesions. Owing to the nature of CT to be transaxial images, a structure which is greater than a certain size appears as several serial CT images. Consequently each observer must reconstruct those images into a three-dimensional (3-D) form mentally. It has been supposed to be of great use if such a 3-D form can be described as a definite figure. A new computer program has been developed which can produce 3-D figures from the profiles of organs and lesions on CT images using spline curves. The figures obtained through this method are regarded to have practical applications.

  7. Spectrotemporal CT data acquisition and reconstruction at low dose

    International Nuclear Information System (INIS)

    Clark, Darin P.; Badea, Cristian T.; Lee, Chang-Lung; Kirsch, David G.

    2015-01-01

    Purpose: X-ray computed tomography (CT) is widely used, both clinically and preclinically, for fast, high-resolution anatomic imaging; however, compelling opportunities exist to expand its use in functional imaging applications. For instance, spectral information combined with nanoparticle contrast agents enables quantification of tissue perfusion levels, while temporal information details cardiac and respiratory dynamics. The authors propose and demonstrate a projection acquisition and reconstruction strategy for 5D CT (3D + dual energy + time) which recovers spectral and temporal information without substantially increasing radiation dose or sampling time relative to anatomic imaging protocols. Methods: The authors approach the 5D reconstruction problem within the framework of low-rank and sparse matrix decomposition. Unlike previous work on rank-sparsity constrained CT reconstruction, the authors establish an explicit rank-sparse signal model to describe the spectral and temporal dimensions. The spectral dimension is represented as a well-sampled time and energy averaged image plus regularly undersampled principal components describing the spectral contrast. The temporal dimension is represented as the same time and energy averaged reconstruction plus contiguous, spatially sparse, and irregularly sampled temporal contrast images. Using a nonlinear, image domain filtration approach, the authors refer to as rank-sparse kernel regression, the authors transfer image structure from the well-sampled time and energy averaged reconstruction to the spectral and temporal contrast images. This regularization strategy strictly constrains the reconstruction problem while approximately separating the temporal and spectral dimensions. Separability results in a highly compressed representation for the 5D data in which projections are shared between the temporal and spectral reconstruction subproblems, enabling substantial undersampling. The authors solved the 5D reconstruction

  8. Direct cone beam SPECT reconstruction with camera tilt

    International Nuclear Information System (INIS)

    Jianying Li; Jaszczak, R.J.; Greer, K.L.; Coleman, R.E.; Zongjian Cao; Tsui, B.M.W.

    1993-01-01

    A filtered backprojection (FBP) algorithm is derived to perform cone beam (CB) single-photon emission computed tomography (SPECT) reconstruction with camera tilt using circular orbits. This algorithm reconstructs the tilted angle CB projection data directly by incorporating the tilt angle into it. When the tilt angle becomes zero, this algorithm reduces to that of Feldkamp. Experimentally acquired phantom studies using both a two-point source and the three-dimensional Hoffman brain phantom have been performed. The transaxial tilted cone beam brain images and profiles obtained using the new algorithm are compared with those without camera tilt. For those slices which have approximately the same distance from the detector in both tilt and non-tilt set-ups, the two transaxial reconstructions have similar profiles. The two-point source images reconstructed from this new algorithm and the tilted cone beam brain images are also compared with those reconstructed from the existing tilted cone beam algorithm. (author)

  9. Fan-beam and cone-beam image reconstruction via filtering the backprojection image of differentiated projection data

    International Nuclear Information System (INIS)

    Zhuang Tingliang; Leng Shuai; Nett, Brian E; Chen Guanghong

    2004-01-01

    In this paper, a new image reconstruction scheme is presented based on Tuy's cone-beam inversion scheme and its fan-beam counterpart. It is demonstrated that Tuy's inversion scheme may be used to derive a new framework for fan-beam and cone-beam image reconstruction. In this new framework, images are reconstructed via filtering the backprojection image of differentiated projection data. The new framework is mathematically exact and is applicable to a general source trajectory provided the Tuy data sufficiency condition is satisfied. By choosing a piece-wise constant function for one of the components in the factorized weighting function, the filtering kernel is one dimensional, viz. the filtering process is along a straight line. Thus, the derived image reconstruction algorithm is mathematically exact and efficient. In the cone-beam case, the derived reconstruction algorithm is applicable to a large class of source trajectories where the pi-lines or the generalized pi-lines exist. In addition, the new reconstruction scheme survives the super-short scan mode in both the fan-beam and cone-beam cases provided the data are not transversely truncated. Numerical simulations were conducted to validate the new reconstruction scheme for the fan-beam case

  10. Improved proton computed tomography by dual modality image reconstruction

    Energy Technology Data Exchange (ETDEWEB)

    Hansen, David C., E-mail: dch@ki.au.dk; Bassler, Niels [Experimental Clinical Oncology, Aarhus University, 8000 Aarhus C (Denmark); Petersen, Jørgen Breede Baltzer [Medical Physics, Aarhus University Hospital, 8000 Aarhus C (Denmark); Sørensen, Thomas Sangild [Computer Science, Aarhus University, 8000 Aarhus C, Denmark and Clinical Medicine, Aarhus University, 8200 Aarhus N (Denmark)

    2014-03-15

    Purpose: Proton computed tomography (CT) is a promising image modality for improving the stopping power estimates and dose calculations for particle therapy. However, the finite range of about 33 cm of water of most commercial proton therapy systems limits the sites that can be scanned from a full 360° rotation. In this paper the authors propose a method to overcome the problem using a dual modality reconstruction (DMR) combining the proton data with a cone-beam x-ray prior. Methods: A Catphan 600 phantom was scanned using a cone beam x-ray CT scanner. A digital replica of the phantom was created in the Monte Carlo code Geant4 and a 360° proton CT scan was simulated, storing the entrance and exit position and momentum vector of every proton. Proton CT images were reconstructed using a varying number of angles from the scan. The proton CT images were reconstructed using a constrained nonlinear conjugate gradient algorithm, minimizing total variation and the x-ray CT prior while remaining consistent with the proton projection data. The proton histories were reconstructed along curved cubic-spline paths. Results: The spatial resolution of the cone beam CT prior was retained for the fully sampled case and the 90° interval case, with the MTF = 0.5 (modulation transfer function) ranging from 5.22 to 5.65 linepairs/cm. In the 45° interval case, the MTF = 0.5 dropped to 3.91 linepairs/cm For the fully sampled DMR, the maximal root mean square (RMS) error was 0.006 in units of relative stopping power. For the limited angle cases the maximal RMS error was 0.18, an almost five-fold improvement over the cone beam CT estimate. Conclusions: Dual modality reconstruction yields the high spatial resolution of cone beam x-ray CT while maintaining the improved stopping power estimation of proton CT. In the case of limited angles, the use of prior image proton CT greatly improves the resolution and stopping power estimate, but does not fully achieve the quality of a 360

  11. Improved proton computed tomography by dual modality image reconstruction

    International Nuclear Information System (INIS)

    Hansen, David C.; Bassler, Niels; Petersen, Jørgen Breede Baltzer; Sørensen, Thomas Sangild

    2014-01-01

    Purpose: Proton computed tomography (CT) is a promising image modality for improving the stopping power estimates and dose calculations for particle therapy. However, the finite range of about 33 cm of water of most commercial proton therapy systems limits the sites that can be scanned from a full 360° rotation. In this paper the authors propose a method to overcome the problem using a dual modality reconstruction (DMR) combining the proton data with a cone-beam x-ray prior. Methods: A Catphan 600 phantom was scanned using a cone beam x-ray CT scanner. A digital replica of the phantom was created in the Monte Carlo code Geant4 and a 360° proton CT scan was simulated, storing the entrance and exit position and momentum vector of every proton. Proton CT images were reconstructed using a varying number of angles from the scan. The proton CT images were reconstructed using a constrained nonlinear conjugate gradient algorithm, minimizing total variation and the x-ray CT prior while remaining consistent with the proton projection data. The proton histories were reconstructed along curved cubic-spline paths. Results: The spatial resolution of the cone beam CT prior was retained for the fully sampled case and the 90° interval case, with the MTF = 0.5 (modulation transfer function) ranging from 5.22 to 5.65 linepairs/cm. In the 45° interval case, the MTF = 0.5 dropped to 3.91 linepairs/cm For the fully sampled DMR, the maximal root mean square (RMS) error was 0.006 in units of relative stopping power. For the limited angle cases the maximal RMS error was 0.18, an almost five-fold improvement over the cone beam CT estimate. Conclusions: Dual modality reconstruction yields the high spatial resolution of cone beam x-ray CT while maintaining the improved stopping power estimation of proton CT. In the case of limited angles, the use of prior image proton CT greatly improves the resolution and stopping power estimate, but does not fully achieve the quality of a 360

  12. Optimization of CT image reconstruction algorithms for the lung tissue research consortium (LTRC)

    Science.gov (United States)

    McCollough, Cynthia; Zhang, Jie; Bruesewitz, Michael; Bartholmai, Brian

    2006-03-01

    To create a repository of clinical data, CT images and tissue samples and to more clearly understand the pathogenetic features of pulmonary fibrosis and emphysema, the National Heart, Lung, and Blood Institute (NHLBI) launched a cooperative effort known as the Lung Tissue Resource Consortium (LTRC). The CT images for the LTRC effort must contain accurate CT numbers in order to characterize tissues, and must have high-spatial resolution to show fine anatomic structures. This study was performed to optimize the CT image reconstruction algorithms to achieve these criteria. Quantitative analyses of phantom and clinical images were conducted. The ACR CT accreditation phantom containing five regions of distinct CT attenuations (CT numbers of approximately -1000 HU, -80 HU, 0 HU, 130 HU and 900 HU), and a high-contrast spatial resolution test pattern, was scanned using CT systems from two manufacturers (General Electric (GE) Healthcare and Siemens Medical Solutions). Phantom images were reconstructed using all relevant reconstruction algorithms. Mean CT numbers and image noise (standard deviation) were measured and compared for the five materials. Clinical high-resolution chest CT images acquired on a GE CT system for a patient with diffuse lung disease were reconstructed using BONE and STANDARD algorithms and evaluated by a thoracic radiologist in terms of image quality and disease extent. The clinical BONE images were processed with a 3 x 3 x 3 median filter to simulate a thicker slice reconstructed in smoother algorithms, which have traditionally been proven to provide an accurate estimation of emphysema extent in the lungs. Using a threshold technique, the volume of emphysema (defined as the percentage of lung voxels having a CT number lower than -950 HU) was computed for the STANDARD, BONE, and BONE filtered. The CT numbers measured in the ACR CT Phantom images were accurate for all reconstruction kernels for both manufacturers. As expected, visual evaluation of the

  13. Improvement of the temporal resolution of cardiac CT reconstruction algorithms using an optimized filtering step

    International Nuclear Information System (INIS)

    Roux, S.; Desbat, L.; Koenig, A.; Grangeat, P.

    2005-01-01

    In this paper we study a property of the filtering step of multi-cycle reconstruction algorithm used in the field of cardiac CT. We show that the common filtering step procedure is not optimal in the case of divergent geometry and decrease slightly the temporal resolution. We propose to use the filtering procedure related to the work of Noo at al ( F.Noo, M. Defrise, R. Clakdoyle, and H. Kudo. Image reconstruction from fan-beam projections on less than a short-scan. Phys. Med.Biol., 47:2525-2546, July 2002)and show that this alternative allows to reach the optimal temporal resolution with the same computational effort. (N.C.)

  14. Application of CT three-dimensional reconstruction in elbow injury

    International Nuclear Information System (INIS)

    Liang Wenhua; Qian Li

    2009-01-01

    Objective: To investigate the application of multi-slice spiral CT in fracture of elbow, and to study the value of different methods of the reconstruction. Methods: Thin line cross-section spiral CT scan was carried out in 13 cases with elbow injury, three-dimensional reconstruction was completed later. Several reconstructed image quality to display f the elbow fracture and dislocation were analyzed and compared. Results: 13 cases (17) elbow trauma included humeral media epicondyle fracture, humeral external epicondyle fracture, intercondylar fracture, olecranal fracture and radial head fracture. Among them, X-ray film showed negative in three sites, showed suspect fractures in 2 cases, and only showed single fracture in 2 cases. MPR reconstruction image could not only identify the diagnosis of fracture, but also provide further multi-angle display on fracture line and the extent of articular surface involvement. Surface reconstruction technology could exclude the impact of passive elbow flexion and display elbow injury more intuitively. Conclusion The elbow fracture dislocation could be showed clearly in multi-slice spiral CT, especially for complex fractures, with unmatched advantages compared to X-ray for clinical diagnosis and treatment determination. (authors)

  15. A faster ordered-subset convex algorithm for iterative reconstruction in a rotation-free micro-CT system

    International Nuclear Information System (INIS)

    Quan, E; Lalush, D S

    2009-01-01

    We present a faster iterative reconstruction algorithm based on the ordered-subset convex (OSC) algorithm for transmission CT. The OSC algorithm was modified such that it calculates the normalization term before the iterative process in order to save computational cost. The modified version requires only one backprojection per iteration as compared to two required for the original OSC. We applied the modified OSC (MOSC) algorithm to a rotation-free micro-CT system that we proposed previously, observed its performance, and compared with the OSC algorithm for 3D cone-beam reconstruction. Measurements on the reconstructed images as well as the point spread functions show that MOSC is quite similar to OSC; in noise-resolution trade-off, MOSC is comparable with OSC in a regular-noise situation and it is slightly worse than OSC in an extremely high-noise situation. The timing record shows that MOSC saves 25-30% CPU time, depending on the number of iterations used. We conclude that the MOSC algorithm is more efficient than OSC and provides comparable images.

  16. Low-dose X-ray CT reconstruction via dictionary learning.

    Science.gov (United States)

    Xu, Qiong; Yu, Hengyong; Mou, Xuanqin; Zhang, Lei; Hsieh, Jiang; Wang, Ge

    2012-09-01

    Although diagnostic medical imaging provides enormous benefits in the early detection and accuracy diagnosis of various diseases, there are growing concerns on the potential side effect of radiation induced genetic, cancerous and other diseases. How to reduce radiation dose while maintaining the diagnostic performance is a major challenge in the computed tomography (CT) field. Inspired by the compressive sensing theory, the sparse constraint in terms of total variation (TV) minimization has already led to promising results for low-dose CT reconstruction. Compared to the discrete gradient transform used in the TV method, dictionary learning is proven to be an effective way for sparse representation. On the other hand, it is important to consider the statistical property of projection data in the low-dose CT case. Recently, we have developed a dictionary learning based approach for low-dose X-ray CT. In this paper, we present this method in detail and evaluate it in experiments. In our method, the sparse constraint in terms of a redundant dictionary is incorporated into an objective function in a statistical iterative reconstruction framework. The dictionary can be either predetermined before an image reconstruction task or adaptively defined during the reconstruction process. An alternating minimization scheme is developed to minimize the objective function. Our approach is evaluated with low-dose X-ray projections collected in animal and human CT studies, and the improvement associated with dictionary learning is quantified relative to filtered backprojection and TV-based reconstructions. The results show that the proposed approach might produce better images with lower noise and more detailed structural features in our selected cases. However, there is no proof that this is true for all kinds of structures.

  17. WE-G-207-02: Full Sequential Projection Onto Convex Sets (FS-POCS) for X-Ray CT Reconstruction

    International Nuclear Information System (INIS)

    Liu, L; Han, Y; Jin, M

    2015-01-01

    Purpose: To develop an iterative reconstruction method for X-ray CT, in which the reconstruction can quickly converge to the desired solution with much reduced projection views. Methods: The reconstruction is formulated as a convex feasibility problem, i.e. the solution is an intersection of three convex sets: 1) data fidelity (DF) set – the L2 norm of the difference of observed projections and those from the reconstructed image is no greater than an error bound; 2) non-negativity of image voxels (NN) set; and 3) piecewise constant (PC) set - the total variation (TV) of the reconstructed image is no greater than an upper bound. The solution can be found by applying projection onto convex sets (POCS) sequentially for these three convex sets. Specifically, the algebraic reconstruction technique and setting negative voxels as zero are used for projection onto the DF and NN sets, respectively, while the projection onto the PC set is achieved by solving a standard Rudin, Osher, and Fatemi (ROF) model. The proposed method is named as full sequential POCS (FS-POCS), which is tested using the Shepp-Logan phantom and the Catphan600 phantom and compared with two similar algorithms, TV-POCS and CP-TV. Results: Using the Shepp-Logan phantom, the root mean square error (RMSE) of reconstructed images changing along with the number of iterations is used as the convergence measurement. In general, FS- POCS converges faster than TV-POCS and CP-TV, especially with fewer projection views. FS-POCS can also achieve accurate reconstruction of cone-beam CT of the Catphan600 phantom using only 54 views, comparable to that of FDK using 364 views. Conclusion: We developed an efficient iterative reconstruction for sparse-view CT using full sequential POCS. The simulation and physical phantom data demonstrated the computational efficiency and effectiveness of FS-POCS

  18. Calibration of megavoltage cone-beam CT for radiotherapy dose calculations: Correction of cupping artifacts and conversion of CT numbers to electron density

    International Nuclear Information System (INIS)

    Petit, Steven F.; Elmpt, Wouter J. C. van; Nijsten, Sebastiaan M. J. J. G.; Lambin, Philippe; Dekker, Andre L. A. J.

    2008-01-01

    Megavoltage cone-beam CT (MV CBCT) is used for three-dimensional imaging of the patient anatomy on the treatment table prior to or just after radiotherapy treatment. To use MV CBCT images for radiotherapy dose calculation purposes, reliable electron density (ED) distributions are needed. Patient scatter, beam hardening and softening effects result in cupping artifacts in MV CBCT images and distort the CT number to ED conversion. A method based on transmission images is presented to correct for these effects without using prior knowledge of the object's geometry. The scatter distribution originating from the patient is calculated with pencil beam scatter kernels that are fitted based on transmission measurements. The radiological thickness is extracted from the scatter subtracted transmission images and is then converted to the primary transmission used in the cone-beam reconstruction. These corrections are performed in an iterative manner, without using prior knowledge regarding the geometry and composition of the object. The method was tested using various homogeneous and inhomogeneous phantoms with varying shapes and compositions, including a phantom with different electron density inserts, phantoms with large density variations, and an anthropomorphic head phantom. For all phantoms, the cupping artifact was substantially removed from the images and a linear relation between the CT number and electron density was found. After correction the deviations in reconstructed ED from the true values were reduced from up to 0.30 ED units to 0.03 for the majority of the phantoms; the residual difference is equal to the amount of noise in the images. The ED distributions were evaluated in terms of absolute dose calculation accuracy for homogeneous cylinders of different size; errors decreased from 7% to below 1% in the center of the objects for the uncorrected and corrected images, respectively, and maximum differences were reduced from 17% to 2%, respectively. The

  19. TH-E-17A-06: Anatomical-Adaptive Compressed Sensing (AACS) Reconstruction for Thoracic 4-Dimensional Cone-Beam CT

    International Nuclear Information System (INIS)

    Shieh, C; Kipritidis, J; OBrien, R; Cooper, B; Kuncic, Z; Keall, P

    2014-01-01

    Purpose: The Feldkamp-Davis-Kress (FDK) algorithm currently used for clinical thoracic 4-dimensional (4D) cone-beam CT (CBCT) reconstruction suffers from noise and streaking artifacts due to projection under-sampling. Compressed sensing theory enables reconstruction of under-sampled datasets via total-variation (TV) minimization, but TV-minimization algorithms such as adaptive-steepest-descent-projection-onto-convex-sets (ASD-POCS) often converge slowly and are prone to over-smoothing anatomical details. These disadvantages can be overcome by incorporating general anatomical knowledge via anatomy segmentation. Based on this concept, we have developed an anatomical-adaptive compressed sensing (AACS) algorithm for thoracic 4D-CBCT reconstruction. Methods: AACS is based on the ASD-POCS framework, where each iteration consists of a TV-minimization step and a data fidelity constraint step. Prior to every AACS iteration, four major thoracic anatomical structures - soft tissue, lungs, bony anatomy, and pulmonary details - were segmented from the updated solution image. Based on the segmentation, an anatomical-adaptive weighting was applied to the TV-minimization step, so that TV-minimization was enhanced at noisy/streaky regions and suppressed at anatomical structures of interest. The image quality and convergence speed of AACS was compared to conventional ASD-POCS using an XCAT digital phantom and a patient scan. Results: For the XCAT phantom, the AACS image represented the ground truth better than the ASD-POCS image, giving a higher structural similarity index (0.93 vs. 0.84) and lower absolute difference (1.1*10 4 vs. 1.4*10 4 ). For the patient case, while both algorithms resulted in much less noise and streaking than FDK, the AACS image showed considerably better contrast and sharpness of the vessels, tumor, and fiducial marker than the ASD-POCS image. In addition, AACS converged over 50% faster than ASD-POCS in both cases. Conclusions: The proposed AACS algorithm

  20. TH-E-17A-06: Anatomical-Adaptive Compressed Sensing (AACS) Reconstruction for Thoracic 4-Dimensional Cone-Beam CT

    Energy Technology Data Exchange (ETDEWEB)

    Shieh, C; Kipritidis, J; OBrien, R; Cooper, B; Kuncic, Z; Keall, P [The University of Sydney, Sydney, New South Wales (Australia)

    2014-06-15

    Purpose: The Feldkamp-Davis-Kress (FDK) algorithm currently used for clinical thoracic 4-dimensional (4D) cone-beam CT (CBCT) reconstruction suffers from noise and streaking artifacts due to projection under-sampling. Compressed sensing theory enables reconstruction of under-sampled datasets via total-variation (TV) minimization, but TV-minimization algorithms such as adaptive-steepest-descent-projection-onto-convex-sets (ASD-POCS) often converge slowly and are prone to over-smoothing anatomical details. These disadvantages can be overcome by incorporating general anatomical knowledge via anatomy segmentation. Based on this concept, we have developed an anatomical-adaptive compressed sensing (AACS) algorithm for thoracic 4D-CBCT reconstruction. Methods: AACS is based on the ASD-POCS framework, where each iteration consists of a TV-minimization step and a data fidelity constraint step. Prior to every AACS iteration, four major thoracic anatomical structures - soft tissue, lungs, bony anatomy, and pulmonary details - were segmented from the updated solution image. Based on the segmentation, an anatomical-adaptive weighting was applied to the TV-minimization step, so that TV-minimization was enhanced at noisy/streaky regions and suppressed at anatomical structures of interest. The image quality and convergence speed of AACS was compared to conventional ASD-POCS using an XCAT digital phantom and a patient scan. Results: For the XCAT phantom, the AACS image represented the ground truth better than the ASD-POCS image, giving a higher structural similarity index (0.93 vs. 0.84) and lower absolute difference (1.1*10{sup 4} vs. 1.4*10{sup 4}). For the patient case, while both algorithms resulted in much less noise and streaking than FDK, the AACS image showed considerably better contrast and sharpness of the vessels, tumor, and fiducial marker than the ASD-POCS image. In addition, AACS converged over 50% faster than ASD-POCS in both cases. Conclusions: The proposed AACS

  1. Medical image reconstruction. A conceptual tutorial

    International Nuclear Information System (INIS)

    Zeng, Gengsheng Lawrence

    2010-01-01

    ''Medical Image Reconstruction: A Conceptual Tutorial'' introduces the classical and modern image reconstruction technologies, such as two-dimensional (2D) parallel-beam and fan-beam imaging, three-dimensional (3D) parallel ray, parallel plane, and cone-beam imaging. This book presents both analytical and iterative methods of these technologies and their applications in X-ray CT (computed tomography), SPECT (single photon emission computed tomography), PET (positron emission tomography), and MRI (magnetic resonance imaging). Contemporary research results in exact region-of-interest (ROI) reconstruction with truncated projections, Katsevich's cone-beam filtered backprojection algorithm, and reconstruction with highly undersampled data with l 0 -minimization are also included. (orig.)

  2. Motion estimation and compensation in dynamic spiral CT reconstruction; Estimation et compensation de mouvement en reconstruction dynamique de tomodensitometrie helicoidale

    Energy Technology Data Exchange (ETDEWEB)

    Kimdon, J.; Grangeat, P.; Koenig, A.; Bonnet, St

    2004-07-01

    Respiratory and cardiac motion causes blurring in dynamic X-ray Computed Tomography (CT). Fast scans reduce this problem, but they require a higher radiation dose per time period to maintain the signal to noise ratio of the resulting images, thereby magnifying the health risk to the patient. As an alternative to increased radiation, our team has already developed a cone-beam reconstruction algorithm based on a dynamic particle model that estimates, predicts, and compensates for respiratory motion in circular X-ray CT. The current paper presents an extension of this method to spiral CT, applicable to modern multi-slice scanners that take advantage of the speed and dose benefits of helical trajectories. We adapted all three main areas of the algorithm: backprojection, prediction, and compensation/accumulation. In backprojection, we changed the longitudinal re-binning technique, filter direction, and the method of enforcing the data sufficiency requirements. For prediction, we had to be careful of objects appearing and disappearing as the scanner bed advanced. For compensation/accumulation, we controlled the reconstruction time and combined images to cover a greater longitudinal extent for each phase in the respiratory or cardiac cycle. Tests with moving numerical phantoms demonstrate that the algorithm successfully improves the temporal resolution of the images without increasing the dose or reducing the signal-to-noise ratio. (authors)

  3. Task-based detectability in CT image reconstruction by filtered backprojection and penalized likelihood estimation

    Energy Technology Data Exchange (ETDEWEB)

    Gang, Grace J. [Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario M5G 2M9, Canada and Department of Biomedical Engineering, Johns Hopkins University, Baltimore Maryland 21205 (Canada); Stayman, J. Webster; Zbijewski, Wojciech [Department of Biomedical Engineering, Johns Hopkins University, Baltimore Maryland 21205 (United States); Siewerdsen, Jeffrey H., E-mail: jeff.siewerdsen@jhu.edu [Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario M5G 2M9, Canada and Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland 21205 (United States)

    2014-08-15

    Purpose: Nonstationarity is an important aspect of imaging performance in CT and cone-beam CT (CBCT), especially for systems employing iterative reconstruction. This work presents a theoretical framework for both filtered-backprojection (FBP) and penalized-likelihood (PL) reconstruction that includes explicit descriptions of nonstationary noise, spatial resolution, and task-based detectability index. Potential utility of the model was demonstrated in the optimal selection of regularization parameters in PL reconstruction. Methods: Analytical models for local modulation transfer function (MTF) and noise-power spectrum (NPS) were investigated for both FBP and PL reconstruction, including explicit dependence on the object and spatial location. For FBP, a cascaded systems analysis framework was adapted to account for nonstationarity by separately calculating fluence and system gains for each ray passing through any given voxel. For PL, the point-spread function and covariance were derived using the implicit function theorem and first-order Taylor expansion according toFessler [“Mean and variance of implicitly defined biased estimators (such as penalized maximum likelihood): Applications to tomography,” IEEE Trans. Image Process. 5(3), 493–506 (1996)]. Detectability index was calculated for a variety of simple tasks. The model for PL was used in selecting the regularization strength parameter to optimize task-based performance, with both a constant and a spatially varying regularization map. Results: Theoretical models of FBP and PL were validated in 2D simulated fan-beam data and found to yield accurate predictions of local MTF and NPS as a function of the object and the spatial location. The NPS for both FBP and PL exhibit similar anisotropic nature depending on the pathlength (and therefore, the object and spatial location within the object) traversed by each ray, with the PL NPS experiencing greater smoothing along directions with higher noise. The MTF of FBP

  4. Tensor-based Dictionary Learning for Spectral CT Reconstruction

    Science.gov (United States)

    Zhang, Yanbo; Wang, Ge

    2016-01-01

    Spectral computed tomography (CT) produces an energy-discriminative attenuation map of an object, extending a conventional image volume with a spectral dimension. In spectral CT, an image can be sparsely represented in each of multiple energy channels, and are highly correlated among energy channels. According to this characteristics, we propose a tensor-based dictionary learning method for spectral CT reconstruction. In our method, tensor patches are extracted from an image tensor, which is reconstructed using the filtered backprojection (FBP), to form a training dataset. With the Candecomp/Parafac decomposition, a tensor-based dictionary is trained, in which each atom is a rank-one tensor. Then, the trained dictionary is used to sparsely represent image tensor patches during an iterative reconstruction process, and the alternating minimization scheme is adapted for optimization. The effectiveness of our proposed method is validated with both numerically simulated and real preclinical mouse datasets. The results demonstrate that the proposed tensor-based method generally produces superior image quality, and leads to more accurate material decomposition than the currently popular popular methods. PMID:27541628

  5. Tensor-Based Dictionary Learning for Spectral CT Reconstruction.

    Science.gov (United States)

    Zhang, Yanbo; Mou, Xuanqin; Wang, Ge; Yu, Hengyong

    2017-01-01

    Spectral computed tomography (CT) produces an energy-discriminative attenuation map of an object, extending a conventional image volume with a spectral dimension. In spectral CT, an image can be sparsely represented in each of multiple energy channels, and are highly correlated among energy channels. According to this characteristics, we propose a tensor-based dictionary learning method for spectral CT reconstruction. In our method, tensor patches are extracted from an image tensor, which is reconstructed using the filtered backprojection (FBP), to form a training dataset. With the Candecomp/Parafac decomposition, a tensor-based dictionary is trained, in which each atom is a rank-one tensor. Then, the trained dictionary is used to sparsely represent image tensor patches during an iterative reconstruction process, and the alternating minimization scheme is adapted for optimization. The effectiveness of our proposed method is validated with both numerically simulated and real preclinical mouse datasets. The results demonstrate that the proposed tensor-based method generally produces superior image quality, and leads to more accurate material decomposition than the currently popular popular methods.

  6. Direct cone-beam cardiac reconstruction algorithm with cardiac banding artifact correction

    International Nuclear Information System (INIS)

    Taguchi, Katsuyuki; Chiang, Beshan S.; Hein, Ilmar A.

    2006-01-01

    Multislice helical computed tomography (CT) is a promising noninvasive technique for coronary artery imaging. Various factors can cause inconsistencies in cardiac CT data, which can result in degraded image quality. These inconsistencies may be the result of the patient physiology (e.g., heart rate variations), the nature of the data (e.g., cone-angle), or the reconstruction algorithm itself. An algorithm which provides the best temporal resolution for each slice, for example, often provides suboptimal image quality for the entire volume since the cardiac temporal resolution (TRc) changes from slice to slice. Such variations in TRc can generate strong banding artifacts in multi-planar reconstruction images or three-dimensional images. Discontinuous heart walls and coronary arteries may compromise the accuracy of the diagnosis. A β-blocker is often used to reduce and stabilize patients' heart rate but cannot eliminate the variation. In order to obtain robust and optimal image quality, a software solution that increases the temporal resolution and decreases the effect of heart rate is highly desirable. This paper proposes an ECG-correlated direct cone-beam reconstruction algorithm (TCOT-EGR) with cardiac banding artifact correction (CBC) and disconnected projections redundancy compensation technique (DIRECT). First the theory and analytical model of the cardiac temporal resolution is outlined. Next, the performance of the proposed algorithms is evaluated by using computer simulations as well as patient data. It will be shown that the proposed algorithms enhance the robustness of the image quality against inconsistencies by guaranteeing smooth transition of heart cycles used in reconstruction

  7. Cone beam CT imaging with limited angle of projections and prior knowledge for volumetric verification of non-coplanar beam radiation therapy: a proof of concept study

    Science.gov (United States)

    Meng, Bowen; Xing, Lei; Han, Bin; Koong, Albert; Chang, Daniel; Cheng, Jason; Li, Ruijiang

    2013-11-01

    Non-coplanar beams are important for treatment of both cranial and noncranial tumors. Treatment verification of such beams with couch rotation/kicks, however, is challenging, particularly for the application of cone beam CT (CBCT). In this situation, only limited and unconventional imaging angles are feasible to avoid collision between the gantry, couch, patient, and on-board imaging system. The purpose of this work is to develop a CBCT verification strategy for patients undergoing non-coplanar radiation therapy. We propose an image reconstruction scheme that integrates a prior image constrained compressed sensing (PICCS) technique with image registration. Planning CT or CBCT acquired at the neutral position is rotated and translated according to the nominal couch rotation/translation to serve as the initial prior image. Here, the nominal couch movement is chosen to have a rotational error of 5° and translational error of 8 mm from the ground truth in one or more axes or directions. The proposed reconstruction scheme alternates between two major steps. First, an image is reconstructed using the PICCS technique implemented with total-variation minimization and simultaneous algebraic reconstruction. Second, the rotational/translational setup errors are corrected and the prior image is updated by applying rigid image registration between the reconstructed image and the previous prior image. The PICCS algorithm and rigid image registration are alternated iteratively until the registration results fall below a predetermined threshold. The proposed reconstruction algorithm is evaluated with an anthropomorphic digital phantom and physical head phantom. The proposed algorithm provides useful volumetric images for patient setup using projections with an angular range as small as 60°. It reduced the translational setup errors from 8 mm to generally <1 mm and the rotational setup errors from 5° to <1°. Compared with the PICCS algorithm alone, the integration of rigid

  8. Impact of polychromatic x-ray sources on helical, cone-beam computed tomography and dual-energy methods

    International Nuclear Information System (INIS)

    Sidky, Emil Y; Zou Yu; Pan Xiaochuan

    2004-01-01

    Recently, there has been much work devoted to developing accurate and efficient algorithms for image reconstruction in helical, cone-beam computed tomography (CT). Little attention, however, has been directed to the effect of physical factors on helical, cone-beam CT image reconstruction. This work investigates the effect of polychromatic x-rays on image reconstruction in helical, cone-beam computed tomography. A pre-reconstruction dual-energy technique is developed to reduce beam-hardening artefacts and enhance contrast in soft tissue

  9. Pulmonary sequestration: diagnosis with three dimensional reconstruction using spiral CT

    International Nuclear Information System (INIS)

    Nie Yongkang; Zhao Shaohong; Cai Zulong; Yang Li; Zhao Hong; Zhang Ailian; Huang Hui

    2003-01-01

    Objective: To evaluate the role of three dimensional (3D) reconstruction using spiral CT in the diagnosis of pulmonary sequestration. Methods: Ten patients with pulmonary sequestration were analyzed. The diagnoses were confirmed by angiography in 2 patients, by operation in 2 patients, and by CT angiography in 6 patients. All patients were examined with Philips SR 7000 or GE Lightspeed Plus scanner. CT images were transferred to a workstation and 3D reconstruction was performed. All images were reviewed and analyzed by two radiologists. Results: Among 10 patients, the pulmonary sequestration was in the right lower lobe in 1 patient and in the left lower lobe in 9 patients. Anomalous systemic arteries originated from thoracic aorta in 8 patients and from celiac artery in 2 patients. On plain CT scan, there were 4 patients with patchy opacities, 3 patients with hilar mass accompanying vascular engorgement and profusion in adjacent parenchyma, 2 patients with finger-like appendage surrounded by hyper-inflated lung, and 1 patient with lung mass-like lesion. Enhanced CT revealed anomalous systemic arteries in 9 patients and drainage vein in 7 patients. Maximum intensity projection (MIP) and curvilinear reconstruction could depict the abnormal systemic artery and drainage vein in sequestration. Surface shadow display (SSD) and volume rendering (VR) could delineate the anomalous systemic artery. Conclusion: 3D reconstruction with enhanced spiral CT can depict anomalous systemic artery and drainage vein and it is the first method of choice in diagnosing pulmonary sequestration

  10. Low-Dose X-ray CT Reconstruction via Dictionary Learning

    Science.gov (United States)

    Xu, Qiong; Zhang, Lei; Hsieh, Jiang; Wang, Ge

    2013-01-01

    Although diagnostic medical imaging provides enormous benefits in the early detection and accuracy diagnosis of various diseases, there are growing concerns on the potential side effect of radiation induced genetic, cancerous and other diseases. How to reduce radiation dose while maintaining the diagnostic performance is a major challenge in the computed tomography (CT) field. Inspired by the compressive sensing theory, the sparse constraint in terms of total variation (TV) minimization has already led to promising results for low-dose CT reconstruction. Compared to the discrete gradient transform used in the TV method, dictionary learning is proven to be an effective way for sparse representation. On the other hand, it is important to consider the statistical property of projection data in the low-dose CT case. Recently, we have developed a dictionary learning based approach for low-dose X-ray CT. In this paper, we present this method in detail and evaluate it in experiments. In our method, the sparse constraint in terms of a redundant dictionary is incorporated into an objective function in a statistical iterative reconstruction framework. The dictionary can be either predetermined before an image reconstruction task or adaptively defined during the reconstruction process. An alternating minimization scheme is developed to minimize the objective function. Our approach is evaluated with low-dose X-ray projections collected in animal and human CT studies, and the improvement associated with dictionary learning is quantified relative to filtered backprojection and TV-based reconstructions. The results show that the proposed approach might produce better images with lower noise and more detailed structural features in our selected cases. However, there is no proof that this is true for all kinds of structures. PMID:22542666

  11. SU-D-12A-06: A Comprehensive Parameter Analysis for Low Dose Cone-Beam CT Reconstruction

    International Nuclear Information System (INIS)

    Lu, W; Yan, H; Gu, X; Jiang, S; Jia, X; Bai, T; Zhou, L

    2014-01-01

    Purpose: There is always a parameter in compressive sensing based iterative reconstruction (IR) methods low dose cone-beam CT (CBCT), which controls the weight of regularization relative to data fidelity. A clear understanding of the relationship between image quality and parameter values is important. The purpose of this study is to investigate this subject based on experimental data and a representative advanced IR algorithm using Tight-frame (TF) regularization. Methods: Three data sets of a Catphan phantom acquired at low, regular and high dose levels are used. For each tests, 90 projections covering a 200-degree scan range are used for reconstruction. Three different regions-of-interest (ROIs) of different contrasts are used to calculate contrast-to-noise ratios (CNR) for contrast evaluation. A single point structure is used to measure modulation transfer function (MTF) for spatial-resolution evaluation. Finally, we analyze CNRs and MTFs to study the relationship between image quality and parameter selections. Results: It was found that: 1) there is no universal optimal parameter. The optimal parameter value depends on specific task and dose level. 2) There is a clear trade-off between CNR and resolution. The parameter for the best CNR is always smaller than that for the best resolution. 3) Optimal parameters are also dose-specific. Data acquired under a high dose protocol require less regularization, yielding smaller optimal parameter values. 4) Comparing with conventional FDK images, TF-based CBCT images are better under a certain optimally selected parameters. The advantages are more obvious for low dose data. Conclusion: We have investigated the relationship between image quality and parameter values in the TF-based IR algorithm. Preliminary results indicate optimal parameters are specific to both the task types and dose levels, providing guidance for selecting parameters in advanced IR algorithms. This work is supported in part by NIH (1R01CA154747-01)

  12. Three-dimensional monochromatic x-ray CT

    Science.gov (United States)

    Saito, Tsuneo; Kudo, Hiroyuki; Takeda, Tohoru; Itai, Yuji; Tokumori, Kenji; Toyofuku, Fukai; Hyodo, Kazuyuki; Ando, Masami; Nishimura, Ktsuyuki; Uyama, Chikao

    1995-08-01

    In this paper, we describe a 3D computed tomography (3D CT) using monochromatic x-rays generated by synchrotron radiation, which performs a direct reconstruction of 3D volume image of an object from its cone-beam projections. For the develpment of 3D CT, scanning orbit of x-ray source to obtain complete 3D information about an object and corresponding 3D image reconstruction algorithm are considered. Computer simulation studies demonstrate the validities of proposed scanning method and reconstruction algorithm. A prototype experimental system of 3D CT was constructed. Basic phantom examinations and specific material CT image by energy subtraction obtained in this experimental system are shown.

  13. Spectral CT metal artifact reduction with an optimization-based reconstruction algorithm

    Science.gov (United States)

    Gilat Schmidt, Taly; Barber, Rina F.; Sidky, Emil Y.

    2017-03-01

    Metal objects cause artifacts in computed tomography (CT) images. This work investigated the feasibility of a spectral CT method to reduce metal artifacts. Spectral CT acquisition combined with optimization-based reconstruction is proposed to reduce artifacts by modeling the physical effects that cause metal artifacts and by providing the flexibility to selectively remove corrupted spectral measurements in the spectral-sinogram space. The proposed Constrained `One-Step' Spectral CT Image Reconstruction (cOSSCIR) algorithm directly estimates the basis material maps while enforcing convex constraints. The incorporation of constraints on the reconstructed basis material maps is expected to mitigate undersampling effects that occur when corrupted data is excluded from reconstruction. The feasibility of the cOSSCIR algorithm to reduce metal artifacts was investigated through simulations of a pelvis phantom. The cOSSCIR algorithm was investigated with and without the use of a third basis material representing metal. The effects of excluding data corrupted by metal were also investigated. The results demonstrated that the proposed cOSSCIR algorithm reduced metal artifacts and improved CT number accuracy. For example, CT number error in a bright shading artifact region was reduced from 403 HU in the reference filtered backprojection reconstruction to 33 HU using the proposed algorithm in simulation. In the dark shading regions, the error was reduced from 1141 HU to 25 HU. Of the investigated approaches, decomposing the data into three basis material maps and excluding the corrupted data demonstrated the greatest reduction in metal artifacts.

  14. Two-and three-dimensional CT reconstruction

    International Nuclear Information System (INIS)

    Fishman, E.K.; Ney, D.R.; Magid, D.

    1990-01-01

    This paper determines the optimal imaging sequence for creating two- and three-dimensional (2D/3D) skeletal reconstructions from CT data. A cadaver femur, a bone phantom, and a surgically created fracture were scanned with varying protocols to determine the optimal protocol for creating 2D/3D images. The scanning protocols used varying section thickness (2, 4, and 8 mm) as well as scan spacing (2, 3, 4 and 8 mm). All images were reconstructed into 2D data sets with a bicubic interpolation and 3D datasets with volumetric rendering. The results were reviewed by two reviewers to determine the quality of images reconstruction

  15. Accuracy improvement of CT reconstruction using tree-structured filter bank

    International Nuclear Information System (INIS)

    Ueda, Kazuhiro; Morimoto, Hiroaki; Morikawa, Yoshitaka; Murakami, Junichi

    2009-01-01

    Accuracy improvement of 'CT reconstruction algorithm using TSFB (Tree-Structured Filter Bank)' that is high-speed CT reconstruction algorithm, was proposed. TSFB method could largely reduce the amount of computation in comparison with the CB (Convolution Backprojection) method, but it was the problem that an artifact occurred in a reconstruction image since reconstruction was performed with disregard to a signal out of the reconstruction domain in stage processing. Also the whole band filter being the component of a two-dimensional synthesis filter was IIR filter and then an artifact occurred at the end of the reconstruction image. In order to suppress these artifacts the proposed method enlarged the processing range by the TSFB method in the domain outside by the width control of the specimen line and line addition to the reconstruction domain outside. And, furthermore, to avoid increase of the amount of computation, the algorithm was proposed such as to decide the needed processing range depending on the number of steps processing with the TSFB and the degree of incline of filter, and then update the position and width of the specimen line to process the needed range. According to the simulation to realize a high-speed and highly accurate CT reconstruction in this way, the quality of the reconstruction image of the proposed method was improved in comparison with the TSFB method and got the same result with the CB method. (T. Tanaka)

  16. Reconstruction of CT images by the Bayes- back projection method

    CERN Document Server

    Haruyama, M; Takase, M; Tobita, H

    2002-01-01

    In the course of research on quantitative assay of non-destructive measurement of radioactive waste, the have developed a unique program based on the Bayesian theory for reconstruction of transmission computed tomography (TCT) image. The reconstruction of cross-section images in the CT technology usually employs the Filtered Back Projection method. The new imaging reconstruction program reported here is based on the Bayesian Back Projection method, and it has a function of iterative improvement images by every step of measurement. Namely, this method has the capability of prompt display of a cross-section image corresponding to each angled projection data from every measurement. Hence, it is possible to observe an improved cross-section view by reflecting each projection data in almost real time. From the basic theory of Baysian Back Projection method, it can be not only applied to CT types of 1st, 2nd, and 3rd generation. This reported deals with a reconstruction program of cross-section images in the CT of ...

  17. Blockwise conjugate gradient methods for image reconstruction in volumetric CT.

    Science.gov (United States)

    Qiu, W; Titley-Peloquin, D; Soleimani, M

    2012-11-01

    Cone beam computed tomography (CBCT) enables volumetric image reconstruction from 2D projection data and plays an important role in image guided radiation therapy (IGRT). Filtered back projection is still the most frequently used algorithm in applications. The algorithm discretizes the scanning process (forward projection) into a system of linear equations, which must then be solved to recover images from measured projection data. The conjugate gradients (CG) algorithm and its variants can be used to solve (possibly regularized) linear systems of equations Ax=b and linear least squares problems minx∥b-Ax∥2, especially when the matrix A is very large and sparse. Their applications can be found in a general CT context, but in tomography problems (e.g. CBCT reconstruction) they have not widely been used. Hence, CBCT reconstruction using the CG-type algorithm LSQR was implemented and studied in this paper. In CBCT reconstruction, the main computational challenge is that the matrix A usually is very large, and storing it in full requires an amount of memory well beyond the reach of commodity computers. Because of these memory capacity constraints, only a small fraction of the weighting matrix A is typically used, leading to a poor reconstruction. In this paper, to overcome this difficulty, the matrix A is partitioned and stored blockwise, and blockwise matrix-vector multiplications are implemented within LSQR. This implementation allows us to use the full weighting matrix A for CBCT reconstruction without further enhancing computer standards. Tikhonov regularization can also be implemented in this fashion, and can produce significant improvement in the reconstructed images. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

  18. Filtered backprojection proton CT reconstruction along most likely paths

    Energy Technology Data Exchange (ETDEWEB)

    Rit, Simon; Dedes, George; Freud, Nicolas; Sarrut, David; Letang, Jean Michel [Universite de Lyon, CREATIS, CNRS UMR5220, Inserm U1044, INSA-Lyon, Universite Lyon 1, Centre Leon Berard, 69008 Lyon (France)

    2013-03-15

    Purpose: Proton CT (pCT) has the potential to accurately measure the electron density map of tissues at low doses but the spatial resolution is prohibitive if the curved paths of protons in matter is not accounted for. The authors propose to account for an estimate of the most likely path of protons in a filtered backprojection (FBP) reconstruction algorithm. Methods: The energy loss of protons is first binned in several proton radiographs at different distances to the proton source to exploit the depth-dependency of the estimate of the most likely path. This process is named the distance-driven binning. A voxel-specific backprojection is then used to select the adequate radiograph in the distance-driven binning in order to propagate in the pCT image the best achievable spatial resolution in proton radiographs. The improvement in spatial resolution is demonstrated using Monte Carlo simulations of resolution phantoms. Results: The spatial resolution in the distance-driven binning depended on the distance of the objects from the source and was optimal in the binned radiograph corresponding to that distance. The spatial resolution in the reconstructed pCT images decreased with the depth in the scanned object but it was always better than previous FBP algorithms assuming straight line paths. In a water cylinder with 20 cm diameter, the observed range of spatial resolutions was 0.7 - 1.6 mm compared to 1.0 - 2.4 mm at best with a straight line path assumption. The improvement was strongly enhanced in shorter 200 Degree-Sign scans. Conclusions: Improved spatial resolution was obtained in pCT images with filtered backprojection reconstruction using most likely path estimates of protons. The improvement in spatial resolution combined with the practicality of FBP algorithms compared to iterative reconstruction algorithms makes this new algorithm a candidate of choice for clinical pCT.

  19. Generalized Fourier slice theorem for cone-beam image reconstruction.

    Science.gov (United States)

    Zhao, Shuang-Ren; Jiang, Dazong; Yang, Kevin; Yang, Kang

    2015-01-01

    The cone-beam reconstruction theory has been proposed by Kirillov in 1961, Tuy in 1983, Feldkamp in 1984, Smith in 1985, Pierre Grangeat in 1990. The Fourier slice theorem is proposed by Bracewell 1956, which leads to the Fourier image reconstruction method for parallel-beam geometry. The Fourier slice theorem is extended to fan-beam geometry by Zhao in 1993 and 1995. By combining the above mentioned cone-beam image reconstruction theory and the above mentioned Fourier slice theory of fan-beam geometry, the Fourier slice theorem in cone-beam geometry is proposed by Zhao 1995 in short conference publication. This article offers the details of the derivation and implementation of this Fourier slice theorem for cone-beam geometry. Especially the problem of the reconstruction from Fourier domain has been overcome, which is that the value of in the origin of Fourier space is 0/0. The 0/0 type of limit is proper handled. As examples, the implementation results for the single circle and two perpendicular circle source orbits are shown. In the cone-beam reconstruction if a interpolation process is considered, the number of the calculations for the generalized Fourier slice theorem algorithm is O(N^4), which is close to the filtered back-projection method, here N is the image size of 1-dimension. However the interpolation process can be avoid, in that case the number of the calculations is O(N5).

  20. MO-DE-207A-08: Four-Dimensional Cone-Beam CT Iterative Reconstruction with Time-Ordered Chain Graph Model for Non-Periodic Organ Motion and Deformation

    Energy Technology Data Exchange (ETDEWEB)

    Nakano, M; Haga, A; Hanaoka, S; Nakagawa, K [The University of Tokyo Hospital, Bunkyo-ku, Tokyo (Japan); Kotoku, J [Teikyo University, Itabashi-ku, Tokyo (Japan); Magome, T [Komazawa University, Setagaya-ku, Tokyo (Japan); Masutani, Y [Hiroshima-City University, Hiroshima, Hiroshima (Japan)

    2016-06-15

    Purpose: The purpose of this study is to propose a new concept of four-dimensional (4D) cone-beam CT (CBCT) reconstruction for non-periodic organ motion using the Time-ordered Chain Graph Model (TCGM), and to compare the reconstructed results with the previously proposed methods, the total variation-based compressed sensing (TVCS) and prior-image constrained compressed sensing (PICCS). Methods: CBCT reconstruction method introduced in this study consisted of maximum a posteriori (MAP) iterative reconstruction combined with a regularization term derived from a concept of TCGM, which includes a constraint coming from the images of neighbouring time-phases. The time-ordered image series were concurrently reconstructed in the MAP iterative reconstruction framework. Angular range of projections for each time-phase was 90 degrees for TCGM and PICCS, and 200 degrees for TVCS. Two kinds of projection data, an elliptic-cylindrical digital phantom data and two clinical patients’ data, were used for reconstruction. The digital phantom contained an air sphere moving 3 cm along longitudinal axis, and temporal resolution of each method was evaluated by measuring the penumbral width of reconstructed moving air sphere. The clinical feasibility of non-periodic time-ordered 4D CBCT reconstruction was also examined using projection data of prostate cancer patients. Results: The results of reconstructed digital phantom shows that the penumbral widths of TCGM yielded the narrowest result; PICCS and TCGM were 10.6% and 17.4% narrower than that of TVCS, respectively. This suggests that the TCGM has the better temporal resolution than the others. Patients’ CBCT projection data were also reconstructed and all three reconstructed results showed motion of rectal gas and stool. The result of TCGM provided visually clearer and less blurring images. Conclusion: The present study demonstrates that the new concept for 4D CBCT reconstruction, TCGM, combined with MAP iterative reconstruction

  1. Application status of three-dimensional CT reconstruction in hepatobiliary surgery

    Directory of Open Access Journals (Sweden)

    JIANG Chao

    2017-02-01

    Full Text Available With the development of imaging technology, three-dimensional CT reconstruction has been widely used in hepatobiliary surgery. Three-dimensional CT reconstruction can divide and reconstruct two-dimensional images into three-dimensional images and clearly show the location of lesion and its relationship with the intrahepatic bile duct system. It has an important value in the preoperative assessment of liver volume, diagnosis and treatment decision-making process, intraoperative precise operation, and postoperative individualized management, and promotes the constant development of hepatobiliary surgery and minimally invasive technology, and therefore, it holds promise for clinical application.

  2. Edge-oriented dual-dictionary guided enrichment (EDGE) for MRI-CT image reconstruction.

    Science.gov (United States)

    Li, Liang; Wang, Bigong; Wang, Ge

    2016-01-01

    In this paper, we formulate the joint/simultaneous X-ray CT and MRI image reconstruction. In particular, a novel algorithm is proposed for MRI image reconstruction from highly under-sampled MRI data and CT images. It consists of two steps. First, a training dataset is generated from a series of well-registered MRI and CT images on the same patients. Then, an initial MRI image of a patient can be reconstructed via edge-oriented dual-dictionary guided enrichment (EDGE) based on the training dataset and a CT image of the patient. Second, an MRI image is reconstructed using the dictionary learning (DL) algorithm from highly under-sampled k-space data and the initial MRI image. Our algorithm can establish a one-to-one correspondence between the two imaging modalities, and obtain a good initial MRI estimation. Both noise-free and noisy simulation studies were performed to evaluate and validate the proposed algorithm. The results with different under-sampling factors show that the proposed algorithm performed significantly better than those reconstructed using the DL algorithm from MRI data alone.

  3. A reconstruction algorithms for helical cone-beam SPECT

    International Nuclear Information System (INIS)

    Weng, Y.; Zeng, G.L.; Gullberg, G.T.

    1993-01-01

    Cone-beam SPECT provides improved sensitivity for imaging small organs like the brain and heart. However, current cone-beam tomography with the focal point traversing a planar orbit does not acquire sufficient data to give an accurate reconstruction. In this paper, the authors employ a data-acquisition method which obtains complete data for cone-beam SPECT by simultaneously rotating the gamma camera and translating the patient bed, so that cone-beam projections can be obtained with the focal point traversing a helix surrounding the patient. An implementation of Grangeat's algorithm for helical cone-beam projections is developed. The algorithm requires a rebinning step to convert cone-beam data to parallel-beam data which are then reconstructed using the 3D Radon inversion. A fast new rebinning scheme is developed which uses all of the detected data to reconstruct the image and properly normalizes any multiply scanned data. This algorithm is shown to produce less artifacts than the commonly used Feldkamp algorithm when applied to either a circular planar orbit or a helical orbit acquisition. The algorithm can easily be extended to any arbitrary orbit

  4. Dose reduction with adaptive statistical iterative reconstruction for paediatric CT: phantom study and clinical experience on chest and abdomen CT.

    Science.gov (United States)

    Gay, F; Pavia, Y; Pierrat, N; Lasalle, S; Neuenschwander, S; Brisse, H J

    2014-01-01

    To assess the benefit and limits of iterative reconstruction of paediatric chest and abdominal computed tomography (CT). The study compared adaptive statistical iterative reconstruction (ASIR) with filtered back projection (FBP) on 64-channel MDCT. A phantom study was first performed using variable tube potential, tube current and ASIR settings. The assessed image quality indices were the signal-to-noise ratio (SNR), the noise power spectrum, low contrast detectability (LCD) and spatial resolution. A clinical retrospective study of 26 children (M:F = 14/12, mean age: 4 years, range: 1-9 years) was secondarily performed allowing comparison of 18 chest and 14 abdominal CT pairs, one with a routine CT dose and FBP reconstruction, and the other with 30 % lower dose and 40 % ASIR reconstruction. Two radiologists independently compared the images for overall image quality, noise, sharpness and artefacts, and measured image noise. The phantom study demonstrated a significant increase in SNR without impairment of the LCD or spatial resolution, except for tube current values below 30-50 mA. On clinical images, no significant difference was observed between FBP and reduced dose ASIR images. Iterative reconstruction allows at least 30 % dose reduction in paediatric chest and abdominal CT, without impairment of image quality. • Iterative reconstruction helps lower radiation exposure levels in children undergoing CT. • Adaptive statistical iterative reconstruction (ASIR) significantly increases SNR without impairing spatial resolution. • For abdomen and chest CT, ASIR allows at least a 30 % dose reduction.

  5. Model-based iterative reconstruction technique for radiation dose reduction in chest CT: comparison with the adaptive statistical iterative reconstruction technique

    Energy Technology Data Exchange (ETDEWEB)

    Katsura, Masaki; Matsuda, Izuru; Akahane, Masaaki; Sato, Jiro; Akai, Hiroyuki; Yasaka, Koichiro; Kunimatsu, Akira; Ohtomo, Kuni [University of Tokyo, Department of Radiology, Graduate School of Medicine, Bunkyo-ku, Tokyo (Japan)

    2012-08-15

    To prospectively evaluate dose reduction and image quality characteristics of chest CT reconstructed with model-based iterative reconstruction (MBIR) compared with adaptive statistical iterative reconstruction (ASIR). One hundred patients underwent reference-dose and low-dose unenhanced chest CT with 64-row multidetector CT. Images were reconstructed with 50 % ASIR-filtered back projection blending (ASIR50) for reference-dose CT, and with ASIR50 and MBIR for low-dose CT. Two radiologists assessed the images in a blinded manner for subjective image noise, artefacts and diagnostic acceptability. Objective image noise was measured in the lung parenchyma. Data were analysed using the sign test and pair-wise Student's t-test. Compared with reference-dose CT, there was a 79.0 % decrease in dose-length product with low-dose CT. Low-dose MBIR images had significantly lower objective image noise (16.93 {+-} 3.00) than low-dose ASIR (49.24 {+-} 9.11, P < 0.01) and reference-dose ASIR images (24.93 {+-} 4.65, P < 0.01). Low-dose MBIR images were all diagnostically acceptable. Unique features of low-dose MBIR images included motion artefacts and pixellated blotchy appearances, which did not adversely affect diagnostic acceptability. Diagnostically acceptable chest CT images acquired with nearly 80 % less radiation can be obtained using MBIR. MBIR shows greater potential than ASIR for providing diagnostically acceptable low-dose CT images without severely compromising image quality. (orig.)

  6. Noise simulation in cone beam CT imaging with parallel computing

    International Nuclear Information System (INIS)

    Tu, S.-J.; Shaw, Chris C; Chen, Lingyun

    2006-01-01

    We developed a computer noise simulation model for cone beam computed tomography imaging using a general purpose PC cluster. This model uses a mono-energetic x-ray approximation and allows us to investigate three primary performance components, specifically quantum noise, detector blurring and additive system noise. A parallel random number generator based on the Weyl sequence was implemented in the noise simulation and a visualization technique was accordingly developed to validate the quality of the parallel random number generator. In our computer simulation model, three-dimensional (3D) phantoms were mathematically modelled and used to create 450 analytical projections, which were then sampled into digital image data. Quantum noise was simulated and added to the analytical projection image data, which were then filtered to incorporate flat panel detector blurring. Additive system noise was generated and added to form the final projection images. The Feldkamp algorithm was implemented and used to reconstruct the 3D images of the phantoms. A 24 dual-Xeon PC cluster was used to compute the projections and reconstructed images in parallel with each CPU processing 10 projection views for a total of 450 views. Based on this computer simulation system, simulated cone beam CT images were generated for various phantoms and technique settings. Noise power spectra for the flat panel x-ray detector and reconstructed images were then computed to characterize the noise properties. As an example among the potential applications of our noise simulation model, we showed that images of low contrast objects can be produced and used for image quality evaluation

  7. Influence of rebinning on the reconstructed resolution of fan-beam SPECT

    International Nuclear Information System (INIS)

    Koole, M.; D'Asseler, Y.; Staelens, S.; Vandenberghe, S.; Eede, I. van den; Walle, R. van de; Lemahieu, I.

    2002-01-01

    Aim: Fan-beam projection data can be rebinned to a parallel-beam geometry. This rebinning operation allows these data to be reconstructed with algorithms for parallel-beam projection data. The advantage of such an operation is that a dedicated projection/backprojection step for fan-beam geometry doesn't need to be developed. In clinical practice bilinear interpolation is often used for this rebinning operation. The aim of this study is to investigate the influence of the rebinning operation on the resolution properties of the reconstructed SPECT-image. Materials and methods: We have simulated the resolution properties of a fan-beam collimator, used in clinical routine, by means of a dedicated projector operation which models the distance dependent sensitivity and resolution of the collimator. With this projector, we generated noise-free sinograms for a point source located at various distances from the center of rotation. The number of angles of these sinograms varied from 60 to 180, corresponding to a step angle of 6 to 2 degrees. These generated fan-beam projection data were reconstructed directly with a filtered backprojection algorithm for fan-beam projection data, which consists of weighting and filtering the projection data with a ramp filter and of a weighted backprojection. Next, the generated fan-beam projection data were rebinned by means of bilinear interpolation and reconstructed with standard filtered backprojection for parallel-beam data. A two-dimensional Gaussian was fitted to the two point sources, one reconstructed with FBP for fan-beam and one reconstructed with FBP for parallel-beam after rebinning, yielding an estimate for the reconstructed Full Width at Half Maximum (FWHM) in the radial and tangential direction, for different locations in the field of view. Results: Results show little difference in resolution degradation in the radial direction between direct reconstruction and reconstruction after rebinning. However, significant loss in

  8. Image reconstruction with shift-variant filtration and its implication for noise and resolution properties in fan-beam computed tomography

    International Nuclear Information System (INIS)

    Pan Xiaochuan; Yu Lifeng

    2003-01-01

    In computed tomography (CT), the fan-beam filtered backprojection (FFBP) algorithm is used widely for image reconstruction. It is known that the FFBP algorithm can significantly amplify data noise and aliasing artifacts in situations where the focal lengths are comparable to or smaller than the size of the field of measurement (FOM). In this work, we propose an algorithm that is less susceptible to data noise, aliasing, and other data inconsistencies than is the FFBP algorithm while retaining the favorable resolution properties of the FFBP algorithm. In an attempt to evaluate the noise properties in reconstructed images, we derive analytic expressions for image variances obtained by use of the FFBP algorithm and the proposed algorithm. Computer simulation studies are conducted for quantitative evaluation of the spatial resolution and noise properties of images reconstructed by use of the algorithms. Numerical results of these studies confirm the favorable spatial resolution and noise properties of the proposed algorithm and verify the validity of the theoretically predicted image variances. The proposed algorithm and the derived analytic expressions for image variances can have practical implications for both estimation and detection/classification tasks making use of CT images, and they can readily be generalized to other fan-beam geometries

  9. Fan-beam filtered-backprojection reconstruction without backprojection weight

    International Nuclear Information System (INIS)

    Dennerlein, Frank; Noo, Frederic; Hornegger, Joachim; Lauritsch, Guenter

    2007-01-01

    In this paper, we address the problem of two-dimensional image reconstruction from fan-beam data acquired along a full 2π scan. Conventional approaches that follow the filtered-backprojection (FBP) structure require a weighted backprojection with the weight depending on the point to be reconstructed and also on the source position; this weight appears only in the case of divergent beam geometries. Compared to reconstruction from parallel-beam data, the backprojection weight implies an increase in computational effort and is also thought to have some negative impacts on noise properties of the reconstructed images. We demonstrate here that direct FBP reconstruction from full-scan fan-beam data is possible with no backprojection weight. Using computer-simulated, realistic fan-beam data, we compared our novel FBP formula with no backprojection weight to the use of an FBP formula based on equal weighting of all data. Comparisons in terms of signal-to-noise ratio, spatial resolution and computational efficiency are presented. These studies show that the formula we suggest yields images with a reduced noise level, at almost identical spatial resolution. This effect increases quickly with the distance from the center of the field of view, from 0% at the center to 20% less noise at 20 cm, and to 40% less noise at 25 cm. Furthermore, the suggested method is computationally less demanding and reduces computation time with a gain that was found to vary between 12% and 43% on the computers used for evaluation

  10. In-line phase contrast micro-CT reconstruction for biomedical specimens.

    Science.gov (United States)

    Fu, Jian; Tan, Renbo

    2014-01-01

    X-ray phase contrast micro computed tomography (micro-CT) can non-destructively provide the internal structure information of soft tissues and low atomic number materials. It has become an invaluable analysis tool for biomedical specimens. Here an in-line phase contrast micro-CT reconstruction technique is reported, which consists of a projection extraction method and the conventional filter back-projection (FBP) reconstruction algorithm. The projection extraction is implemented by applying the Fourier transform to the forward projections of in-line phase contrast micro-CT. This work comprises a numerical study of the method and its experimental verification using a biomedical specimen dataset measured at an X-ray tube source micro-CT setup. The numerical and experimental results demonstrate that the presented technique can improve the imaging contrast of biomedical specimens. It will be of interest for a wide range of in-line phase contrast micro-CT applications in medicine and biology.

  11. TH-EF-207A-05: Feasibility of Applying SMEIR Method On Small Animal 4D Cone Beam CT Imaging

    International Nuclear Information System (INIS)

    Zhong, Y; Zhang, Y; Shao, Y; Wang, J

    2016-01-01

    Purpose: Small animal cone beam CT imaging has been widely used in preclinical research. Due to the higher respiratory rate and heat beats of small animals, motion blurring is inevitable and needs to be corrected in the reconstruction. Simultaneous motion estimation and image reconstruction (SMEIR) method, which uses projection images of all phases, proved to be effective in motion model estimation and able to reconstruct motion-compensated images. We demonstrate the application of SMEIR for small animal 4D cone beam CT imaging by computer simulations on a digital rat model. Methods: The small animal CBCT imaging system was simulated with the source-to-detector distance of 300 mm and the source-to-object distance of 200 mm. A sequence of rat phantom were generated with 0.4 mm 3 voxel size. The respiratory cycle was taken as 1.0 second and the motions were simulated with a diaphragm motion of 2.4mm and an anterior-posterior expansion of 1.6 mm. The projection images were calculated using a ray-tracing method, and 4D-CBCT were reconstructed using SMEIR and FDK methods. The SMEIR method iterates over two alternating steps: 1) motion-compensated iterative image reconstruction by using projections from all respiration phases and 2) motion model estimation from projections directly through a 2D-3D deformable registration of the image obtained in the first step to projection images of other phases. Results: The images reconstructed using SMEIR method reproduced the features in the original phantom. Projections from the same phase were also reconstructed using FDK method. Compared with the FDK results, the images from SMEIR method substantially improve the image quality with minimum artifacts. Conclusion: We demonstrate that it is viable to apply SMEIR method to reconstruct small animal 4D-CBCT images.

  12. Development of a new prior knowledge based image reconstruction algorithm for the cone-beam-CT in radiation therapy

    International Nuclear Information System (INIS)

    Vaegler, Sven

    2016-01-01

    The treatment of cancer in radiation therapy is achievable today by techniques that enable highly conformal dose distributions and steep dose gradients. In order to avoid mistreatment, these irradiation techniques have necessitated enhanced patient localization techniques. With an integrated x-ray tube at modern linear accelerators kV-projections can be acquired over a sufficiently large angular space and can be reconstructed to a volumetric image data set from the current situation of the patient prior to irradiation. The so-called Cone-Beam-CT (CBCT) allows a precise verification of patient positioning as well as adaptive radiotherapy. The benefits of an improved patient positioning due to a daily performed CBCT's is contrary to an increased and not negligible radiation exposure of the patient. In order to decrease the radiation exposure, substantial research effort is focused on various dose reduction strategies. Prominent strategies are the decrease of the charge per projection, the reduction of the number of projections as well as the reduction of the acquisition space. Unfortunately, these acquisition schemes lead to images with degraded quality with the widely used Feldkamp-Davis-Kress image reconstruction algorithm. More sophisticated image reconstruction techniques can deal with these dose-reduction strategies without degrading the image quality. A frequently investigated method is the image reconstruction by minimizing the total variation (TV), which is also known as Compressed Sensing (CS). A Compressed Sensing-based reconstruction framework that includes prior images into the reconstruction algorithm is the Prior-Image-Constrained- Compressed-Sensing algorithm (PICCS). The images reconstructed by PICCS outperform the reconstruction results of the conventional Feldkamp-Davis-Kress algorithm (FDK) based method if only a small number of projections are available. However, a drawback of PICCS is that major deviations between prior image data sets and the

  13. Accelerated gradient methods for total-variation-based CT image reconstruction

    Energy Technology Data Exchange (ETDEWEB)

    Joergensen, Jakob H.; Hansen, Per Christian [Technical Univ. of Denmark, Lyngby (Denmark). Dept. of Informatics and Mathematical Modeling; Jensen, Tobias L.; Jensen, Soeren H. [Aalborg Univ. (Denmark). Dept. of Electronic Systems; Sidky, Emil Y.; Pan, Xiaochuan [Chicago Univ., Chicago, IL (United States). Dept. of Radiology

    2011-07-01

    Total-variation (TV)-based CT image reconstruction has shown experimentally to be capable of producing accurate reconstructions from sparse-view data. In particular TV-based reconstruction is well suited for images with piecewise nearly constant regions. Computationally, however, TV-based reconstruction is demanding, especially for 3D imaging, and the reconstruction from clinical data sets is far from being close to real-time. This is undesirable from a clinical perspective, and thus there is an incentive to accelerate the solution of the underlying optimization problem. The TV reconstruction can in principle be found by any optimization method, but in practice the large scale of the systems arising in CT image reconstruction preclude the use of memory-intensive methods such as Newton's method. The simple gradient method has much lower memory requirements, but exhibits prohibitively slow convergence. In the present work we address the question of how to reduce the number of gradient method iterations needed to achieve a high-accuracy TV reconstruction. We consider the use of two accelerated gradient-based methods, GPBB and UPN, to solve the 3D-TV minimization problem in CT image reconstruction. The former incorporates several heuristics from the optimization literature such as Barzilai-Borwein (BB) step size selection and nonmonotone line search. The latter uses a cleverly chosen sequence of auxiliary points to achieve a better convergence rate. The methods are memory efficient and equipped with a stopping criterion to ensure that the TV reconstruction has indeed been found. An implementation of the methods (in C with interface to Matlab) is available for download from http://www2.imm.dtu.dk/~pch/TVReg/. We compare the proposed methods with the standard gradient method, applied to a 3D test problem with synthetic few-view data. We find experimentally that for realistic parameters the proposed methods significantly outperform the standard gradient method. (orig.)

  14. Feasibility of megavoltage portal CT using an electronic portal imaging device (EPID) and a multi-level scheme algebraic reconstruction technique (MLS-ART)

    International Nuclear Information System (INIS)

    Guan, Huaiqun; Zhu, Yunping

    1998-01-01

    Although electronic portal imaging devices (EPIDs) are efficient tools for radiation therapy verification, they only provide images of overlapped anatomic structures. We investigated using a fluorescent screen/CCD-based EPID, coupled with a novel multi-level scheme algebraic reconstruction technique (MLS-ART), for a feasibility study of portal computed tomography (CT) reconstructions. The CT images might be useful for radiation treatment planning and verification. We used an EPID, set it to work at the linear dynamic range and collimated 6 MV photons from a linear accelerator to a slit beam of 1 cm wide and 25 cm long. We performed scans under a total of ∼200 monitor units (MUs) for several phantoms in which we varied the number of projections and MUs per projection. The reconstructed images demonstrated that using the new MLS-ART technique megavoltage portal CT with a total of 200 MUs can achieve a contrast detectibility of ∼2.5% (object size 5mmx5mm) and a spatial resolution of 2.5 mm. (author)

  15. Model-based iterative reconstruction technique for radiation dose reduction in chest CT: comparison with the adaptive statistical iterative reconstruction technique

    International Nuclear Information System (INIS)

    Katsura, Masaki; Matsuda, Izuru; Akahane, Masaaki; Sato, Jiro; Akai, Hiroyuki; Yasaka, Koichiro; Kunimatsu, Akira; Ohtomo, Kuni

    2012-01-01

    To prospectively evaluate dose reduction and image quality characteristics of chest CT reconstructed with model-based iterative reconstruction (MBIR) compared with adaptive statistical iterative reconstruction (ASIR). One hundred patients underwent reference-dose and low-dose unenhanced chest CT with 64-row multidetector CT. Images were reconstructed with 50 % ASIR-filtered back projection blending (ASIR50) for reference-dose CT, and with ASIR50 and MBIR for low-dose CT. Two radiologists assessed the images in a blinded manner for subjective image noise, artefacts and diagnostic acceptability. Objective image noise was measured in the lung parenchyma. Data were analysed using the sign test and pair-wise Student's t-test. Compared with reference-dose CT, there was a 79.0 % decrease in dose-length product with low-dose CT. Low-dose MBIR images had significantly lower objective image noise (16.93 ± 3.00) than low-dose ASIR (49.24 ± 9.11, P < 0.01) and reference-dose ASIR images (24.93 ± 4.65, P < 0.01). Low-dose MBIR images were all diagnostically acceptable. Unique features of low-dose MBIR images included motion artefacts and pixellated blotchy appearances, which did not adversely affect diagnostic acceptability. Diagnostically acceptable chest CT images acquired with nearly 80 % less radiation can be obtained using MBIR. MBIR shows greater potential than ASIR for providing diagnostically acceptable low-dose CT images without severely compromising image quality. (orig.)

  16. Model-based iterative reconstruction and adaptive statistical iterative reconstruction: dose-reduced CT for detecting pancreatic calcification

    International Nuclear Information System (INIS)

    Yasaka, Koichiro; Katsura, Masaki; Akahane, Masaaki; Sato, Jiro; Matsuda, Izuru; Ohtomo, Kuni

    2016-01-01

    Iterative reconstruction methods have attracted attention for reducing radiation doses in computed tomography (CT). To investigate the detectability of pancreatic calcification using dose-reduced CT reconstructed with model-based iterative construction (MBIR) and adaptive statistical iterative reconstruction (ASIR). This prospective study approved by Institutional Review Board included 85 patients (57 men, 28 women; mean age, 69.9 years; mean body weight, 61.2 kg). Unenhanced CT was performed three times with different radiation doses (reference-dose CT [RDCT], low-dose CT [LDCT], ultralow-dose CT [ULDCT]). From RDCT, LDCT, and ULDCT, images were reconstructed with filtered-back projection (R-FBP, used for establishing reference standard), ASIR (L-ASIR), and MBIR and ASIR (UL-MBIR and UL-ASIR), respectively. A lesion (pancreatic calcification) detection test was performed by two blinded radiologists with a five-point certainty level scale. Dose-length products of RDCT, LDCT, and ULDCT were 410, 97, and 36 mGy-cm, respectively. Nine patients had pancreatic calcification. The sensitivity for detecting pancreatic calcification with UL-MBIR was high (0.67–0.89) compared to L-ASIR or UL-ASIR (0.11–0.44), and a significant difference was seen between UL-MBIR and UL-ASIR for one reader (P = 0.014). The area under the receiver-operating characteristic curve for UL-MBIR (0.818–0.860) was comparable to that for L-ASIR (0.696–0.844). The specificity was lower with UL-MBIR (0.79–0.92) than with L-ASIR or UL-ASIR (0.96–0.99), and a significant difference was seen for one reader (P < 0.01). In UL-MBIR, pancreatic calcification can be detected with high sensitivity, however, we should pay attention to the slightly lower specificity

  17. Model-based iterative reconstruction and adaptive statistical iterative reconstruction: dose-reduced CT for detecting pancreatic calcification.

    Science.gov (United States)

    Yasaka, Koichiro; Katsura, Masaki; Akahane, Masaaki; Sato, Jiro; Matsuda, Izuru; Ohtomo, Kuni

    2016-01-01

    Iterative reconstruction methods have attracted attention for reducing radiation doses in computed tomography (CT). To investigate the detectability of pancreatic calcification using dose-reduced CT reconstructed with model-based iterative construction (MBIR) and adaptive statistical iterative reconstruction (ASIR). This prospective study approved by Institutional Review Board included 85 patients (57 men, 28 women; mean age, 69.9 years; mean body weight, 61.2 kg). Unenhanced CT was performed three times with different radiation doses (reference-dose CT [RDCT], low-dose CT [LDCT], ultralow-dose CT [ULDCT]). From RDCT, LDCT, and ULDCT, images were reconstructed with filtered-back projection (R-FBP, used for establishing reference standard), ASIR (L-ASIR), and MBIR and ASIR (UL-MBIR and UL-ASIR), respectively. A lesion (pancreatic calcification) detection test was performed by two blinded radiologists with a five-point certainty level scale. Dose-length products of RDCT, LDCT, and ULDCT were 410, 97, and 36 mGy-cm, respectively. Nine patients had pancreatic calcification. The sensitivity for detecting pancreatic calcification with UL-MBIR was high (0.67-0.89) compared to L-ASIR or UL-ASIR (0.11-0.44), and a significant difference was seen between UL-MBIR and UL-ASIR for one reader (P = 0.014). The area under the receiver-operating characteristic curve for UL-MBIR (0.818-0.860) was comparable to that for L-ASIR (0.696-0.844). The specificity was lower with UL-MBIR (0.79-0.92) than with L-ASIR or UL-ASIR (0.96-0.99), and a significant difference was seen for one reader (P < 0.01). In UL-MBIR, pancreatic calcification can be detected with high sensitivity, however, we should pay attention to the slightly lower specificity.

  18. Real-time out-of-plane artifact subtraction tomosynthesis imaging using prior CT for scanning beam digital x-ray system

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Meng, E-mail: mengwu@stanford.edu [Department of Electrical Engineering, Stanford University, Stanford, California 94305 (United States); Fahrig, Rebecca [Department of Radiology, Stanford University, Stanford, California 94305 (United States)

    2014-11-01

    Purpose: The scanning beam digital x-ray system (SBDX) is an inverse geometry fluoroscopic system with high dose efficiency and the ability to perform continuous real-time tomosynthesis in multiple planes. This system could be used for image guidance during lung nodule biopsy. However, the reconstructed images suffer from strong out-of-plane artifact due to the small tomographic angle of the system. Methods: The authors propose an out-of-plane artifact subtraction tomosynthesis (OPAST) algorithm that utilizes a prior CT volume to augment the run-time image processing. A blur-and-add (BAA) analytical model, derived from the project-to-backproject physical model, permits the generation of tomosynthesis images that are a good approximation to the shift-and-add (SAA) reconstructed image. A computationally practical algorithm is proposed to simulate images and out-of-plane artifacts from patient-specific prior CT volumes using the BAA model. A 3D image registration algorithm to align the simulated and reconstructed images is described. The accuracy of the BAA analytical model and the OPAST algorithm was evaluated using three lung cancer patients’ CT data. The OPAST and image registration algorithms were also tested with added nonrigid respiratory motions. Results: Image similarity measurements, including the correlation coefficient, mean squared error, and structural similarity index, indicated that the BAA model is very accurate in simulating the SAA images from the prior CT for the SBDX system. The shift-variant effect of the BAA model can be ignored when the shifts between SBDX images and CT volumes are within ±10 mm in the x and y directions. The nodule visibility and depth resolution are improved by subtracting simulated artifacts from the reconstructions. The image registration and OPAST are robust in the presence of added respiratory motions. The dominant artifacts in the subtraction images are caused by the mismatches between the real object and the prior CT

  19. Applicability of 3D-CT facial reconstruction for forensic individual identification

    Energy Technology Data Exchange (ETDEWEB)

    Rocha, Sara dos Santos [Sao Paulo Univ., SP (Brazil). Odontologia Forense; Ramos, Dalton Luiz de Paula [Sao Paulo Univ., SP (Brazil). Dept. of Odontologia Social; Cavalcanti, Marcelo de Gusmao Paraiso [Sao Paulo Univ., SP (Brazil). Dept. de Radiologia

    2003-03-01

    Computed tomography (CT) is used in several clinical dentistry applications even by axial slices and two and three-dimensional reconstructed images (2D-CT and 3D-CT). The purpose of the current study is to assess the precision of linear measurements made in 3D-CT using cranio metric patterns for individual identification in Forensic Dentistry. Five cadaver heads were submitted to a spiral computed tomography using axial slices, and 3D-CT reconstructions were obtained by volume rendering technique with computer graphics tools. Ten (10) cranio metric measurements were determined in 3D-CT images by two examiners independently, twice each, and the standard error of intra- and inter-examiner measurements was assessed. The results demonstrated a low standard error of those measurements, from 0.85% to 3.09%. In conclusion, the linear measurements obtained in osseous and soft tissue structures were considered to be precise in 3D-CT with high imaging quality and resolution. (author)

  20. Applicability of 3D-CT facial reconstruction for forensic individual identification

    International Nuclear Information System (INIS)

    Rocha, Sara dos Santos; Ramos, Dalton Luiz de Paula; Cavalcanti, Marcelo de Gusmao Paraiso

    2003-01-01

    Computed tomography (CT) is used in several clinical dentistry applications even by axial slices and two and three-dimensional reconstructed images (2D-CT and 3D-CT). The purpose of the current study is to assess the precision of linear measurements made in 3D-CT using cranio metric patterns for individual identification in Forensic Dentistry. Five cadaver heads were submitted to a spiral computed tomography using axial slices, and 3D-CT reconstructions were obtained by volume rendering technique with computer graphics tools. Ten (10) cranio metric measurements were determined in 3D-CT images by two examiners independently, twice each, and the standard error of intra- and inter-examiner measurements was assessed. The results demonstrated a low standard error of those measurements, from 0.85% to 3.09%. In conclusion, the linear measurements obtained in osseous and soft tissue structures were considered to be precise in 3D-CT with high imaging quality and resolution. (author)

  1. SU-F-T-441: Dose Calculation Accuracy in CT Images Reconstructed with Artifact Reduction Algorithm

    Energy Technology Data Exchange (ETDEWEB)

    Ng, C; Chan, S; Lee, F; Ngan, R [Queen Elizabeth Hospital (Hong Kong); Lee, V [University of Hong Kong, Hong Kong, HK (Hong Kong)

    2016-06-15

    Purpose: Accuracy of radiotherapy dose calculation in patients with surgical implants is complicated by two factors. First is the accuracy of CT number, second is the dose calculation accuracy. We compared measured dose with dose calculated on CT images reconstructed with FBP and an artifact reduction algorithm (OMAR, Philips) for a phantom with high density inserts. Dose calculation were done with Varian AAA and AcurosXB. Methods: A phantom was constructed with solid water in which 2 titanium or stainless steel rods could be inserted. The phantom was scanned with the Philips Brillance Big Bore CT. Image reconstruction was done with FBP and OMAR. Two 6 MV single field photon plans were constructed for each phantom. Radiochromic films were placed at different locations to measure the dose deposited. One plan has normal incidence on the titanium/steel rods. In the second plan, the beam is at almost glancing incidence on the metal rods. Measurements were then compared with dose calculated with AAA and AcurosXB. Results: The use of OMAR images slightly improved the dose calculation accuracy. The agreement between measured and calculated dose was best with AXB and image reconstructed with OMAR. Dose calculated on titanium phantom has better agreement with measurement. Large discrepancies were seen at points directly above and below the high density inserts. Both AAA and AXB underestimated the dose directly above the metal surface, while overestimated the dose below the metal surface. Doses measured downstream of metal were all within 3% of calculated values. Conclusion: When doing treatment planning for patients with metal implants, care must be taken to acquire correct CT images to improve dose calculation accuracy. Moreover, great discrepancies in measured and calculated dose were observed at metal/tissue interface. Care must be taken in estimating the dose in critical structures that come into contact with metals.

  2. SU-F-I-06: Evaluation of Imaging Dose for Modulation Layer Based Dual Energy Cone-Beam CT

    Energy Technology Data Exchange (ETDEWEB)

    Ju, Eunbin [Department of Medical Science, Ewha Womans University, Seoul (Korea, Republic of); Ahn, SoHyun; Cho, Samju; Keum, Ki Chang [Department of Radiation Oncology, School of Medicine, Yonsei Univeristy, Seoul (Korea, Republic of); Lee, Rena [Department of Radiation Oncology, School of Medicine, Ewha Womans University, Seoul (Korea, Republic of)

    2016-06-15

    Purpose: Dual energy cone beam CT system is finding a variety of promising applications in diagnostic CT, both in imaging of endogenous materials and exogenous materials across a range of body sites. Dual energy cone beam CT system to suggest in this study acquire image by rotating 360 degree with half of the X-ray window covered using copper modulation layer. In the region that covered by modulation layer absorb the low energy X-ray by modulation layer. Relative high energy X-ray passes through the layer and contributes to image reconstruction. Dose evaluation should be carried out in order to utilize such an imaging acquirement technology for clinical use. Methods: For evaluating imaging dose of modulation layer based dual energy cone beam CT system, Prototype cone beam CT that configured X-ray tube (D054SB, Toshiba, Japan) and detector (PaxScan 2520V, Varian Medical Systems, Palo Alto, CA) is used. A range of 0.5–2.0 mm thickness of modulation layer is implemented in Monte Carlo simulation (MCNPX, ver. 2.6.0, Los Alamos National Laboratory, USA) with half of X-ray window covered. In-house phantom using in this study that has 3 cylindrical phantoms configured water, Teflon air with PMMA covered for verifying the comparability the various material in human body and is implemented in Monte Carlo simulation. The actual dose with 2.0 mm copper covered half of X-ray window is measured using Gafchromic EBT3 film with 5.0 mm bolus for compared with simulative dose. Results: Dose in phantom reduced 33% by copper modulation layer of 2.0 mm. Scattering dose occurred in modulation layer by Compton scattering effect is 0.04% of overall dose. Conclusion: Modulation layer of that based dual energy cone beam CT has not influence on unnecessary scatter dose. This study was supported by the Radiation Safety Research Programs (1305033) through the Nuclear Safety and Security Commission.

  3. Angular self-reconstruction of petal-like beams

    CSIR Research Space (South Africa)

    Litvin, IA

    2013-09-01

    Full Text Available equation for predicting the self-reconstruction distance of superpositions of LG beams, which we confirm by numerical propagation as well as by experiment. We explain that the self-reconstruction process is not guaranteed and predict its dependence...

  4. Synchronized multiartifact reduction with tomographic reconstruction (SMART-RECON): A statistical model based iterative image reconstruction method to eliminate limited-view artifacts and to mitigate the temporal-average artifacts in time-resolved CT.

    Science.gov (United States)

    Chen, Guang-Hong; Li, Yinsheng

    2015-08-01

    In x-ray computed tomography (CT), a violation of the Tuy data sufficiency condition leads to limited-view artifacts. In some applications, it is desirable to use data corresponding to a narrow temporal window to reconstruct images with reduced temporal-average artifacts. However, the need to reduce temporal-average artifacts in practice may result in a violation of the Tuy condition and thus undesirable limited-view artifacts. In this paper, the authors present a new iterative reconstruction method, synchronized multiartifact reduction with tomographic reconstruction (SMART-RECON), to eliminate limited-view artifacts using data acquired within an ultranarrow temporal window that severely violates the Tuy condition. In time-resolved contrast enhanced CT acquisitions, image contrast dynamically changes during data acquisition. Each image reconstructed from data acquired in a given temporal window represents one time frame and can be denoted as an image vector. Conventionally, each individual time frame is reconstructed independently. In this paper, all image frames are grouped into a spatial-temporal image matrix and are reconstructed together. Rather than the spatial and/or temporal smoothing regularizers commonly used in iterative image reconstruction, the nuclear norm of the spatial-temporal image matrix is used in SMART-RECON to regularize the reconstruction of all image time frames. This regularizer exploits the low-dimensional structure of the spatial-temporal image matrix to mitigate limited-view artifacts when an ultranarrow temporal window is desired in some applications to reduce temporal-average artifacts. Both numerical simulations in two dimensional image slices with known ground truth and in vivo human subject data acquired in a contrast enhanced cone beam CT exam have been used to validate the proposed SMART-RECON algorithm and to demonstrate the initial performance of the algorithm. Reconstruction errors and temporal fidelity of the reconstructed

  5. The measurement of proton stopping power using proton-cone-beam computed tomography

    International Nuclear Information System (INIS)

    Zygmanski, P.; Rabin, M.S.Z.; Gall, K.P.; Rosenthal, S.J.

    2000-01-01

    A cone-beam computed tomography (CT) system utilizing a proton beam has been developed and tested. The cone beam is produced by scattering a 160 MeV proton beam with a modifier that results in a signal in the detector system, which decreases monotonically with depth in the medium. The detector system consists of a Gd 2 O 2 S:Tb intensifying screen viewed by a cooled CCD camera. The Feldkamp-Davis-Kress cone-beam reconstruction algorithm is applied to the projection data to obtain the CT voxel data representing proton stopping power. The system described is capable of reconstructing data over a 16x16x16cm 3 volume into 512x512x512 voxels. A spatial and contrast resolution phantom was scanned to determine the performance of the system. Spatial resolution is significantly degraded by multiple Coulomb scattering effects. Comparison of the reconstructed proton CT values with x-ray CT derived proton stopping powers shows that there may be some advantage to obtaining stopping powers directly with proton CT. The system described suggests a possible practical method of obtaining this measurement in vivo. (author)

  6. Iterative reconstruction reduces abdominal CT dose

    International Nuclear Information System (INIS)

    Martinsen, Anne Catrine Trægde; Sæther, Hilde Kjernlie; Hol, Per Kristian; Olsen, Dag Rune; Skaane, Per

    2012-01-01

    Objective: In medical imaging, lowering radiation dose from computed tomography scanning, without reducing diagnostic performance is a desired achievement. Iterative image reconstruction may be one tool to achieve dose reduction. This study reports the diagnostic performance using a blending of 50% statistical iterative reconstruction (ASIR) and filtered back projection reconstruction (FBP) compared to standard FBP image reconstruction at different dose levels for liver phantom examinations. Methods: An anthropomorphic liver phantom was scanned at 250, 185, 155, 140, 120 and 100 mA s, on a 64-slice GE Lightspeed VCT scanner. All scans were reconstructed with ASIR and FBP. Four readers evaluated independently on a 5-point scale 21 images, each containing 32 test sectors. In total 672 areas were assessed. ROC analysis was used to evaluate the differences. Results: There was a difference in AUC between the 250 mA s FBP images and the 120 and 100 mA s FBP images. ASIR reconstruction gave a significantly higher diagnostic performance compared to standard reconstruction at 100 mA s. Conclusion: A blending of 50–90% ASIR and FBP may improve image quality of low dose CT examinations of the liver, and thus give a potential for reducing radiation dose.

  7. MO-DE-207A-07: Filtered Iterative Reconstruction (FIR) Via Proximal Forward-Backward Splitting: A Synergy of Analytical and Iterative Reconstruction Method for CT

    International Nuclear Information System (INIS)

    Gao, H

    2016-01-01

    Purpose: This work is to develop a general framework, namely filtered iterative reconstruction (FIR) method, to incorporate analytical reconstruction (AR) method into iterative reconstruction (IR) method, for enhanced CT image quality. Methods: FIR is formulated as a combination of filtered data fidelity and sparsity regularization, and then solved by proximal forward-backward splitting (PFBS) algorithm. As a result, the image reconstruction decouples data fidelity and image regularization with a two-step iterative scheme, during which an AR-projection step updates the filtered data fidelity term, while a denoising solver updates the sparsity regularization term. During the AR-projection step, the image is projected to the data domain to form the data residual, and then reconstructed by certain AR to a residual image which is in turn weighted together with previous image iterate to form next image iterate. Since the eigenvalues of AR-projection operator are close to the unity, PFBS based FIR has a fast convergence. Results: The proposed FIR method is validated in the setting of circular cone-beam CT with AR being FDK and total-variation sparsity regularization, and has improved image quality from both AR and IR. For example, AIR has improved visual assessment and quantitative measurement in terms of both contrast and resolution, and reduced axial and half-fan artifacts. Conclusion: FIR is proposed to incorporate AR into IR, with an efficient image reconstruction algorithm based on PFBS. The CBCT results suggest that FIR synergizes AR and IR with improved image quality and reduced axial and half-fan artifacts. The authors was partially supported by the NSFC (#11405105), the 973 Program (#2015CB856000), and the Shanghai Pujiang Talent Program (#14PJ1404500).

  8. Task-based optimization of image reconstruction in breast CT

    Science.gov (United States)

    Sanchez, Adrian A.; Sidky, Emil Y.; Pan, Xiaochuan

    2014-03-01

    We demonstrate a task-based assessment of image quality in dedicated breast CT in order to optimize the number of projection views acquired. The methodology we employ is based on the Hotelling Observer (HO) and its associated metrics. We consider two tasks: the Rayleigh task of discerning between two resolvable objects and a single larger object, and the signal detection task of classifying an image as belonging to either a signalpresent or signal-absent hypothesis. HO SNR values are computed for 50, 100, 200, 500, and 1000 projection view images, with the total imaging radiation dose held constant. We use the conventional fan-beam FBP algorithm and investigate the effect of varying the width of a Hanning window used in the reconstruction, since this affects both the noise properties of the image and the under-sampling artifacts which can arise in the case of sparse-view acquisitions. Our results demonstrate that fewer projection views should be used in order to increase HO performance, which in this case constitutes an upper-bound on human observer performance. However, the impact on HO SNR of using fewer projection views, each with a higher dose, is not as significant as the impact of employing regularization in the FBP reconstruction through a Hanning filter.

  9. Electron-beam CT diagnosis of congenital cardiovascular diverticula

    International Nuclear Information System (INIS)

    Yang Youyou; Zheng Lili; Li Xiangmin; Zhou Xuhui; Peng Qian; Meng Quanfei; Dai Ruping

    2008-01-01

    Objective: To investigate the clinical application of electron-beam CT (EBCT) in the diagnosis of congenital cardiovascular diverticula. Methods: Retrospective analysis of 9 patients with congenital cardiovascular diverticula confirmed by operation and pathology was done. Of them, enhanced continuous volume scan was performed on 8 patients and enhanced single slice scan was performed on one patient with an Imatron C-150 scanner. Results: The group of 9 patients included one patient with diverticulum of the left ventricle, 3 patients with diverticulum of the atria and 5 patients with diverticulum of the aorta. EBCT scan and three dimensional reconstruction could demonstrate not only the origin, size, shape, location and adjacent structure of diverticula, but also other important complicated abnormalities such as ventriculoarterial connection disorder, cardiac septal defect, aortic coarctation and even dissection. Conclusion: EBCT is an ideal noninvasive technique in the diagnosis of congenital cardiovascular diverticula. (authors)

  10. TH-CD-202-02: A Preliminary Study Evaluating Beam-Hardening Artifact Reduction On CT Direct Electron-Density Images

    Energy Technology Data Exchange (ETDEWEB)

    Li, H; Dolly, S; Zhao, T; Anastasio, M; Mutic, S [Washington University School of Medicine, Saint Louis, MO (United States); Ritter, A; Colombo, V; Raupach, R; Huenemohr, N [Siemens Healthcare GmbH, Deutschland (Germany); Mistry, N [Siemens Medical Solutions USA, Malvern, PA (United States); Yu, L [Mayo Clinic, Rochester, MN (United States)

    2016-06-15

    Purpose: A prototype reconstruction algorithm that can provide direct electron density (ED) images from single energy CT scans is being currently developed by Siemens Healthcare GmbH. This feature can eliminate the need for kV specific calibration curve for radiation treatemnt planning. An added benefit is that beam-hardening artifacts are also reduced on direct-ED images due to the underlying material decomposition. This study is to quantitatively analyze the reduction of beam-hardening artifacts on direct-ED images and suggest additional clinical usages. Methods: HU and direct-ED images were reconstructed on a head phantom scanned on a Siemens Definition AS CT scanner at five tube potentials of 70kV, 80kV, 100kV, 120kV and 140kV respectively. From these images, mean, standard deviation (SD), and local NPS were calculated for regions of interest (ROI) of same locations and sizes. A complete analysis of beam-hardening artifact reduction and image quality improvement was conducted. Results: Along with the increase of tube potentials, ROI means and SDs decrease on both HU and direct-ED images. The mean value differences between HU and direct-ED images are up to 8% with absolute value of 2.9. Compared to that on HU images, the SDs are lower on direct-ED images, and the differences are up to 26%. Interestingly, the local NPS calculated from direct-ED images shows consistent values in the low spatial frequency domain for images acquired from all tube potential settings, while varied dramatically on HU images. This also confirms the beam -hardening artifact reduction on ED images. Conclusions: The low SDs on direct-ED images and relative consistent NPS values in the low spatial frequency domain indicate a reduction of beam-hardening artifacts. The direct-ED image has the potential to assist in more accurate organ contouring, and is a better fit for the desired purpose of CT simulations for radiotherapy.

  11. Parallel CT image reconstruction based on GPUs

    International Nuclear Information System (INIS)

    Flores, Liubov A.; Vidal, Vicent; Mayo, Patricia; Rodenas, Francisco; Verdú, Gumersindo

    2014-01-01

    In X-ray computed tomography (CT) iterative methods are more suitable for the reconstruction of images with high contrast and precision in noisy conditions from a small number of projections. However, in practice, these methods are not widely used due to the high computational cost of their implementation. Nowadays technology provides the possibility to reduce effectively this drawback. It is the goal of this work to develop a fast GPU-based algorithm to reconstruct high quality images from under sampled and noisy projection data. - Highlights: • We developed GPU-based iterative algorithm to reconstruct images. • Iterative algorithms are capable to reconstruct images from under sampled set of projections. • The computer cost of the implementation of the developed algorithm is low. • The efficiency of the algorithm increases for the large scale problems

  12. Clinical investigation of flat panel CT following middle ear reconstruction: a study of 107 patients

    Energy Technology Data Exchange (ETDEWEB)

    Zaoui, K. [University Hospital Heidelberg, Ruprecht Karls University, Department of Otorhinolaryngology, Head and Neck Surgery, Heidelberg (Germany); Kromeier, J. [St. Josefs Hospital, RkK, Department of Radiology, Freiburg (Germany); Neudert, M.; Beleites, T.; Zahnert, T. [University Hospital Dresden, Technical University, Department of Otorhinolaryngology, Head and Neck Surgery, Dresden (Germany); Laszig, R.; Offergeld, C. [University Hospital Freiburg, Albert Ludwigs University, Department of Otorhinolaryngology, Head and Neck Surgery, Freiburg (Germany)

    2014-03-15

    After middle ear reconstruction using partial or total ossicular replacement prostheses (PORP/TORP), an air-bone gap (ABG) may persist because of prosthesis displacement or malposition. So far, CT of the temporal bone has played the main role in the diagnosis of reasons for postoperative insufficient ABG improvement. Recent experimental and clinical studies have evaluated flat panel CT (fpCT) as an alternative imaging technique that provides images with high isovolumetric resolution, fewer metal-induced artefacts and lower irradiation doses. One hundred and seven consecutive patients with chronic otitis media with or without cholesteatoma underwent reconstruction by PORP (n = 52) or TORP (n = 55). All subjects underwent preoperative and postoperative audiometric testing and postoperative fpCT. Statistical evaluation of all 107 patients as well as the sole sub-assembly groups (PORP or TORP) showed a highly significant correlation between hearing improvement and fpCT-determined prosthesis position. FpCT enables detailed postoperative information on patients with middle ear reconstruction. FpCT is a new imaging technique that provides immediate feedback on surgical results after reconstructive middle ear surgery. Specific parameters evaluated by fpCT may serve as a predictive tool for estimated postoperative hearing improvement. Therefore this imaging technique is suitable for postoperative quality control in reconstructive middle ear surgery. (orig.)

  13. Analytical fan-beam and cone-beam reconstruction algorithms with uniform attenuation correction for SPECT

    International Nuclear Information System (INIS)

    Tang Qiulin; Zeng, Gengsheng L; Gullberg, Grant T

    2005-01-01

    In this paper, we developed an analytical fan-beam reconstruction algorithm that compensates for uniform attenuation in SPECT. The new fan-beam algorithm is in the form of backprojection first, then filtering, and is mathematically exact. The algorithm is based on three components. The first one is the established generalized central-slice theorem, which relates the 1D Fourier transform of a set of arbitrary data and the 2D Fourier transform of the backprojected image. The second one is the fact that the backprojection of the fan-beam measurements is identical to the backprojection of the parallel measurements of the same object with the same attenuator. The third one is the stable analytical reconstruction algorithm for uniformly attenuated Radon data, developed by Metz and Pan. The fan-beam algorithm is then extended into a cone-beam reconstruction algorithm, where the orbit of the focal point of the cone-beam imaging geometry is a circle. This orbit geometry does not satisfy Tuy's condition and the obtained cone-beam algorithm is an approximation. In the cone-beam algorithm, the cone-beam data are first backprojected into the 3D image volume; then a slice-by-slice filtering is performed. This slice-by-slice filtering procedure is identical to that of the fan-beam algorithm. Both the fan-beam and cone-beam algorithms are efficient, and computer simulations are presented. The new cone-beam algorithm is compared with Bronnikov's cone-beam algorithm, and it is shown to have better performance with noisy projections

  14. CT Image Reconstruction in a Low Dimensional Manifold

    OpenAIRE

    Cong, Wenxiang; Wang, Ge; Yang, Qingsong; Hsieh, Jiang; Li, Jia; Lai, Rongjie

    2017-01-01

    Regularization methods are commonly used in X-ray CT image reconstruction. Different regularization methods reflect the characterization of different prior knowledge of images. In a recent work, a new regularization method called a low-dimensional manifold model (LDMM) is investigated to characterize the low-dimensional patch manifold structure of natural images, where the manifold dimensionality characterizes structural information of an image. In this paper, we propose a CT image reconstruc...

  15. Intraoperative imaging for patient safety and QA: detection of intracranial hemorrhage using C-arm cone-beam CT

    Science.gov (United States)

    Schafer, Sebastian; Wang, Adam; Otake, Yoshito; Stayman, J. W.; Zbijewski, Wojciech; Kleinszig, Gerhard; Xia, Xuewei; Gallia, Gary L.; Siewerdsen, Jeffrey H.

    2013-03-01

    Intraoperative imaging could improve patient safety and quality assurance (QA) via the detection of subtle complications that might otherwise only be found hours after surgery. Such capability could therefore reduce morbidity and the need for additional intervention. Among the severe adverse events that could be more quickly detected by high-quality intraoperative imaging is acute intracranial hemorrhage (ICH), conventionally assessed using post-operative CT. A mobile C-arm capable of high-quality cone-beam CT (CBCT) in combination with advanced image reconstruction techniques is reported as a means of detecting ICH in the operating room. The system employs an isocentric C-arm with a flat-panel detector in dual gain mode, correction of x-ray scatter and beam-hardening, and a penalized likelihood (PL) iterative reconstruction method. Performance in ICH detection was investigated using a quantitative phantom focusing on (non-contrast-enhanced) blood-brain contrast, an anthropomorphic head phantom, and a porcine model with injection of fresh blood bolus. The visibility of ICH was characterized in terms of contrast-to-noise ratio (CNR) and qualitative evaluation of images by a neurosurgeon. Across a range of size and contrast of the ICH as well as radiation dose from the CBCT scan, the CNR was found to increase from ~2.2-3.7 for conventional filtered backprojection (FBP) to ~3.9-5.4 for PL at equivalent spatial resolution. The porcine model demonstrated superior ICH detectability for PL. The results support the role of high-quality mobile C-arm CBCT employing advanced reconstruction algorithms for detecting subtle complications in the operating room at lower radiation dose and lower cost than intraoperative CT scanners and/or fixedroom C-arms. Such capability could present a potentially valuable aid to patient safety and QA.

  16. Reconstruction of a ring applicator using CT imaging: impact of the reconstruction method and applicator orientation

    International Nuclear Information System (INIS)

    Hellebust, Taran Paulsen; Tanderup, Kari; Bergstrand, Eva Stabell; Knutsen, Bjoern Helge; Roeislien, Jo; Olsen, Dag Rune

    2007-01-01

    The purpose of this study is to investigate whether the method of applicator reconstruction and/or the applicator orientation influence the dose calculation to points around the applicator for brachytherapy of cervical cancer with CT-based treatment planning. A phantom, containing a fixed ring applicator set and six lead pellets representing dose points, was used. The phantom was CT scanned with the ring applicator at four different angles related to the image plane. In each scan the applicator was reconstructed by three methods: (1) direct reconstruction in each image (DR) (2) reconstruction in multiplanar reconstructed images (MPR) and (3) library plans, using pre-defined applicator geometry (LIB). The doses to the lead pellets were calculated. The relative standard deviation (SD) for all reconstruction methods was less than 3.7% in the dose points. The relative SD for the LIB method was significantly lower (p < 0.05) than for the DR and MPR methods for all but two points. All applicator orientations had similar dose calculation reproducibility. Using library plans for applicator reconstruction gives the most reproducible dose calculation. However, with restrictive guidelines for applicator reconstruction the uncertainties for all methods are low compared to other factors influencing the accuracy of brachytherapy

  17. The value of spiral CT thin imaging reconstruction in the diagnosis of obstructive jaundice

    International Nuclear Information System (INIS)

    Huang Zhi; Liu Zhang; Yang Chaoxiang; Lin Chengye; Zhang Li; Li Yuxiang; Ma Yunyan; Xiao Haisong; Lu Zhifeng; Wang Bo; Zhou Yunhong

    2009-01-01

    Objective: To approach the value of spiral CT thin imaging reconstruction in the diagnosis of obstructive jaundice in order to improve the correctness of the diagnosis. Methods: Analysis the cases' clinical manifestation and the CT images, who were diagnosed as obstructive jaundice by operation. All of cases had high-resolution computed tomograyhy scan. The thickness and the interval is 5mm, reconstructed the thickness and the interval to 1 mm and 1.5 mm, then send the images to the workstation and MRR were processed. Analysis the date with the pathology. Results: Spiral CT thin imaging reconstruction have 98% and 93% in the accuracy of location and characterization in the obstruction. Conclusion: The spiral CT thin imaging reconstruction is a good method to improve the accuracy of location and characterization in the obstructive jaundice. (authors)

  18. Prior image constrained image reconstruction in emerging computed tomography applications

    Science.gov (United States)

    Brunner, Stephen T.

    Advances have been made in computed tomography (CT), especially in the past five years, by incorporating prior images into the image reconstruction process. In this dissertation, we investigate prior image constrained image reconstruction in three emerging CT applications: dual-energy CT, multi-energy photon-counting CT, and cone-beam CT in image-guided radiation therapy. First, we investigate the application of Prior Image Constrained Compressed Sensing (PICCS) in dual-energy CT, which has been called "one of the hottest research areas in CT." Phantom and animal studies are conducted using a state-of-the-art 64-slice GE Discovery 750 HD CT scanner to investigate the extent to which PICCS can enable radiation dose reduction in material density and virtual monochromatic imaging. Second, we extend the application of PICCS from dual-energy CT to multi-energy photon-counting CT, which has been called "one of the 12 topics in CT to be critical in the next decade." Numerical simulations are conducted to generate multiple energy bin images for a photon-counting CT acquisition and to investigate the extent to which PICCS can enable radiation dose efficiency improvement. Third, we investigate the performance of a newly proposed prior image constrained scatter correction technique to correct scatter-induced shading artifacts in cone-beam CT, which, when used in image-guided radiation therapy procedures, can assist in patient localization, and potentially, dose verification and adaptive radiation therapy. Phantom studies are conducted using a Varian 2100 EX system with an on-board imager to investigate the extent to which the prior image constrained scatter correction technique can mitigate scatter-induced shading artifacts in cone-beam CT. Results show that these prior image constrained image reconstruction techniques can reduce radiation dose in dual-energy CT by 50% in phantom and animal studies in material density and virtual monochromatic imaging, can lead to radiation

  19. On proton CT reconstruction using MVCT-converted virtual proton projections

    Energy Technology Data Exchange (ETDEWEB)

    Wang Dongxu; Mackie, T. Rockwell; Tome, Wolfgang A. [Department of Medical Physics, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin 53705 and Department of Radiation Oncology, University of Iowa Hospitals and Clinics, Iowa City, Iowa 52242 (United States); Department of Medical Physics, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin 53705 and Morgridge Institute of Research, University of Wisconsin, Madison, Wisconsin 53715 (United States); Department of Medical Physics, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin 53705 and Oncophysics Institute, Albert Einstein College of Medicine, Yeshiva University, Bronx, New York 10461 (United States)

    2012-06-15

    Purpose: To describe a novel methodology of converting megavoltage x-ray projections into virtual proton projections that are otherwise missing due to the proton range limit. These converted virtual proton projections can be used in the reconstruction of proton computed tomography (pCT). Methods: Relations exist between proton projections and multispectral megavoltage x-ray projections for human tissue. Based on these relations, these tissues can be categorized into: (a) adipose tissue; (b) nonadipose soft tissues; and (c) bone. These three tissue categories can be visibly identified on a regular megavoltage x-ray computed tomography (MVCT) image. With an MVCT image and its projection data available, the x-ray projections through heterogeneous anatomy can be converted to the corresponding proton projections using predetermined calibration curves for individual materials, aided by a coarse segmentation on the x-ray CT image. To show the feasibility of this approach, mathematical simulations were carried out. The converted proton projections, plotted on a proton sinogram, were compared to the simulated ground truth. Proton stopping power images were reconstructed using either the virtual proton projections only or a blend of physically available proton projections and virtual proton projections that make up for those missing due to the range limit. These images were compared to a reference image reconstructed from theoretically calculated proton projections. Results: The converted virtual projections had an uncertainty of {+-}0.8% compared to the calculated ground truth. Proton stopping power images reconstructed using a blend of converted virtual projections (48%) and physically available projections (52%) had an uncertainty of {+-}0.86% compared with that reconstructed from theoretically calculated projections. Reconstruction solely from converted virtual proton projections had an uncertainty of {+-}1.1% compared with that reconstructed from theoretical projections

  20. On proton CT reconstruction using MVCT-converted virtual proton projections

    International Nuclear Information System (INIS)

    Wang Dongxu; Mackie, T. Rockwell; Tomé, Wolfgang A.

    2012-01-01

    Purpose: To describe a novel methodology of converting megavoltage x-ray projections into virtual proton projections that are otherwise missing due to the proton range limit. These converted virtual proton projections can be used in the reconstruction of proton computed tomography (pCT). Methods: Relations exist between proton projections and multispectral megavoltage x-ray projections for human tissue. Based on these relations, these tissues can be categorized into: (a) adipose tissue; (b) nonadipose soft tissues; and (c) bone. These three tissue categories can be visibly identified on a regular megavoltage x-ray computed tomography (MVCT) image. With an MVCT image and its projection data available, the x-ray projections through heterogeneous anatomy can be converted to the corresponding proton projections using predetermined calibration curves for individual materials, aided by a coarse segmentation on the x-ray CT image. To show the feasibility of this approach, mathematical simulations were carried out. The converted proton projections, plotted on a proton sinogram, were compared to the simulated ground truth. Proton stopping power images were reconstructed using either the virtual proton projections only or a blend of physically available proton projections and virtual proton projections that make up for those missing due to the range limit. These images were compared to a reference image reconstructed from theoretically calculated proton projections. Results: The converted virtual projections had an uncertainty of ±0.8% compared to the calculated ground truth. Proton stopping power images reconstructed using a blend of converted virtual projections (48%) and physically available projections (52%) had an uncertainty of ±0.86% compared with that reconstructed from theoretically calculated projections. Reconstruction solely from converted virtual proton projections had an uncertainty of ±1.1% compared with that reconstructed from theoretical projections. If

  1. Point spread function modeling and image restoration for cone-beam CT

    International Nuclear Information System (INIS)

    Zhang Hua; Shi Yikai; Huang Kuidong; Xu Zhe

    2015-01-01

    X-ray cone-beam computed tomography (CT) has such notable features as high efficiency and precision, and is widely used in the fields of medical imaging and industrial non-destructive testing, but the inherent imaging degradation reduces the quality of CT images. Aimed at the problems of projection image degradation and restoration in cone-beam CT, a point spread function (PSF) modeling method is proposed first. The general PSF model of cone-beam CT is established, and based on it, the PSF under arbitrary scanning conditions can be calculated directly for projection image restoration without the additional measurement, which greatly improved the application convenience of cone-beam CT. Secondly, a projection image restoration algorithm based on pre-filtering and pre-segmentation is proposed, which can make the edge contours in projection images and slice images clearer after restoration, and control the noise in the equivalent level to the original images. Finally, the experiments verified the feasibility and effectiveness of the proposed methods. (authors)

  2. Accelerated fast iterative shrinkage thresholding algorithms for sparsity-regularized cone-beam CT image reconstruction

    International Nuclear Information System (INIS)

    Xu, Qiaofeng; Sawatzky, Alex; Anastasio, Mark A.; Yang, Deshan; Tan, Jun

    2016-01-01

    Purpose: The development of iterative image reconstruction algorithms for cone-beam computed tomography (CBCT) remains an active and important research area. Even with hardware acceleration, the overwhelming majority of the available 3D iterative algorithms that implement nonsmooth regularizers remain computationally burdensome and have not been translated for routine use in time-sensitive applications such as image-guided radiation therapy (IGRT). In this work, two variants of the fast iterative shrinkage thresholding algorithm (FISTA) are proposed and investigated for accelerated iterative image reconstruction in CBCT. Methods: Algorithm acceleration was achieved by replacing the original gradient-descent step in the FISTAs by a subproblem that is solved by use of the ordered subset simultaneous algebraic reconstruction technique (OS-SART). Due to the preconditioning matrix adopted in the OS-SART method, two new weighted proximal problems were introduced and corresponding fast gradient projection-type algorithms were developed for solving them. We also provided efficient numerical implementations of the proposed algorithms that exploit the massive data parallelism of multiple graphics processing units. Results: The improved rates of convergence of the proposed algorithms were quantified in computer-simulation studies and by use of clinical projection data corresponding to an IGRT study. The accelerated FISTAs were shown to possess dramatically improved convergence properties as compared to the standard FISTAs. For example, the number of iterations to achieve a specified reconstruction error could be reduced by an order of magnitude. Volumetric images reconstructed from clinical data were produced in under 4 min. Conclusions: The FISTA achieves a quadratic convergence rate and can therefore potentially reduce the number of iterations required to produce an image of a specified image quality as compared to first-order methods. We have proposed and investigated

  3. Accelerated fast iterative shrinkage thresholding algorithms for sparsity-regularized cone-beam CT image reconstruction

    Science.gov (United States)

    Xu, Qiaofeng; Yang, Deshan; Tan, Jun; Sawatzky, Alex; Anastasio, Mark A.

    2016-01-01

    Purpose: The development of iterative image reconstruction algorithms for cone-beam computed tomography (CBCT) remains an active and important research area. Even with hardware acceleration, the overwhelming majority of the available 3D iterative algorithms that implement nonsmooth regularizers remain computationally burdensome and have not been translated for routine use in time-sensitive applications such as image-guided radiation therapy (IGRT). In this work, two variants of the fast iterative shrinkage thresholding algorithm (FISTA) are proposed and investigated for accelerated iterative image reconstruction in CBCT. Methods: Algorithm acceleration was achieved by replacing the original gradient-descent step in the FISTAs by a subproblem that is solved by use of the ordered subset simultaneous algebraic reconstruction technique (OS-SART). Due to the preconditioning matrix adopted in the OS-SART method, two new weighted proximal problems were introduced and corresponding fast gradient projection-type algorithms were developed for solving them. We also provided efficient numerical implementations of the proposed algorithms that exploit the massive data parallelism of multiple graphics processing units. Results: The improved rates of convergence of the proposed algorithms were quantified in computer-simulation studies and by use of clinical projection data corresponding to an IGRT study. The accelerated FISTAs were shown to possess dramatically improved convergence properties as compared to the standard FISTAs. For example, the number of iterations to achieve a specified reconstruction error could be reduced by an order of magnitude. Volumetric images reconstructed from clinical data were produced in under 4 min. Conclusions: The FISTA achieves a quadratic convergence rate and can therefore potentially reduce the number of iterations required to produce an image of a specified image quality as compared to first-order methods. We have proposed and investigated

  4. MicroCT Bone Densitometry: Context Sensitivity, Beam Hardening Correction and the Effect of Surrounding Media

    Directory of Open Access Journals (Sweden)

    Philip L. Salmon

    2014-12-01

    Full Text Available The context-sensitivity of microCT bone densitometry due to beam hardening artefacts was assessed. Bones and teeth are scanned with varying thickness of surrounding media (water, alcohol, biological tissue and it is important to understand how this affects reconstructed attenuation (“density” of the mineralized tissue. Aluminium tubes and rods with thickness 0.127mm–5mm were scanned both in air or surrounded by up to 2cm of water. Scans were performed with different energy filters and degrees of software beam hardening correction (BHC. Also tested were the effects of signal-to-noise ratio, magnification and truncation. The thickness of an aluminium tube significantly affected its mean reconstructed attenuation. This effect of thickness could be reduced substantially by BHC for scans in air, but not for scans in water. Varying thickness of surrounding water also changed the mean attenuation of an aluminium tube. This artefact could be almost eliminated by an optimal BHC value. The “cupping” artefact of heterogeneous attenuation (elevated at outer surfaces could be corrected if aluminium was scanned in air, but in water BHC was much less effective. Scan truncation, changes to magnification and signal-to-noise ratio also caused artificial changes to measured attenuation. Measurement of bone mineral density by microCT is highly context sensitive. A surrounding layer of liquid or biological tissue reduces the ability of software BHC to remove bone density artefacts. Sample thickness, truncation, magnification and signal to noise ratio also affect reconstructed attenuation. Thus it is important for densitometry that sample and calibration phantom dimensions and mounting materials are standardised.

  5. Dual resolution cone beam breast CT: A feasibility study

    International Nuclear Information System (INIS)

    Chen Lingyun; Shen Youtao; Lai, Chao-Jen; Han Tao; Zhong Yuncheng; Ge Shuaiping; Liu Xinming; Wang Tianpeng; Yang, Wei T.; Whitman, Gary J.; Shaw, Chris C.

    2009-01-01

    Purpose: In this study, the authors investigated the feasibility of a dual resolution volume-of-interest (VOI) cone beam breast CT technique and compared two implementation approaches in terms of dose saving and scatter reduction. Methods: With this technique, a lead VOI mask with an opening is inserted between the x-ray source and the breast to deliver x-ray exposure to the VOI while blocking x rays outside the VOI. A CCD detector is used to collect the high resolution projection data of the VOI. Low resolution cone beam CT (CBCT) images of the entire breast, acquired with a flat panel (FP) detector, were used to calculate the projection data outside the VOI with the ray-tracing reprojection method. The Feldkamp-Davis-Kress filtered backprojection algorithm was used to reconstruct the dual resolution 3D images. Breast phantoms with 180 μm and smaller microcalcifications (MCs) were imaged with both FP and FP-CCD dual resolution CBCT systems, respectively. Two approaches of implementing the dual resolution technique, breast-centered approach and VOI-centered approach, were investigated and evaluated for dose saving and scatter reduction with Monte Carlo simulation using a GEANT4 package. Results: The results showed that the breast-centered approach saved more breast absorbed dose than did VOI-centered approach with similar scatter reduction. The MCs in fatty breast phantom, which were invisible with FP CBCT scan, became visible with the FP-CCD dual resolution CBCT scan. Conclusions: These results indicate potential improvement of the image quality inside the VOI with reduced breast dose both inside and outside the VOI.

  6. The adaptive statistical iterative reconstruction-V technique for radiation dose reduction in abdominal CT: comparison with the adaptive statistical iterative reconstruction technique.

    Science.gov (United States)

    Kwon, Heejin; Cho, Jinhan; Oh, Jongyeong; Kim, Dongwon; Cho, Junghyun; Kim, Sanghyun; Lee, Sangyun; Lee, Jihyun

    2015-10-01

    To investigate whether reduced radiation dose abdominal CT images reconstructed with adaptive statistical iterative reconstruction V (ASIR-V) compromise the depiction of clinically competent features when compared with the currently used routine radiation dose CT images reconstructed with ASIR. 27 consecutive patients (mean body mass index: 23.55 kg m(-2) underwent CT of the abdomen at two time points. At the first time point, abdominal CT was scanned at 21.45 noise index levels of automatic current modulation at 120 kV. Images were reconstructed with 40% ASIR, the routine protocol of Dong-A University Hospital. At the second time point, follow-up scans were performed at 30 noise index levels. Images were reconstructed with filtered back projection (FBP), 40% ASIR, 30% ASIR-V, 50% ASIR-V and 70% ASIR-V for the reduced radiation dose. Both quantitative and qualitative analyses of image quality were conducted. The CT dose index was also recorded. At the follow-up study, the mean dose reduction relative to the currently used common radiation dose was 35.37% (range: 19-49%). The overall subjective image quality and diagnostic acceptability of the 50% ASIR-V scores at the reduced radiation dose were nearly identical to those recorded when using the initial routine-dose CT with 40% ASIR. Subjective ratings of the qualitative analysis revealed that of all reduced radiation dose CT series reconstructed, 30% ASIR-V and 50% ASIR-V were associated with higher image quality with lower noise and artefacts as well as good sharpness when compared with 40% ASIR and FBP. However, the sharpness score at 70% ASIR-V was considered to be worse than that at 40% ASIR. Objective image noise for 50% ASIR-V was 34.24% and 46.34% which was lower than 40% ASIR and FBP. Abdominal CT images reconstructed with ASIR-V facilitate radiation dose reductions of to 35% when compared with the ASIR. This study represents the first clinical research experiment to use ASIR-V, the newest version of

  7. Prototype heel effect compensation filter for cone-beam CT

    International Nuclear Information System (INIS)

    Mori, Shinichiro; Endo, Masahiro; Nishizawa, Kanae; Ohno, Mari; Miyazaki, Hiroaki; Tsujita, Kazuhiko; Saito, Yasuo

    2005-01-01

    The prototype cone-beam CT (CBCT) has a larger beam width than the conventional multi-detector row CT (MDCT). This causes a non-uniform angular distribution of the x-ray beam intensity known as the heel effect. Scan conditions for CBCT tube current are adjusted on the anode side to obtain an acceptable clinical image quality. However, as the dose is greater on the cathode side than on the anode side, the signal-to-noise ratio on the cathode side is excessively high, resulting in an unnecessary dose amount. To compensate for the heel effect, we developed a heel effect compensation (HEC) filter. The HEC filter rendered the dose distribution uniform and reduced the dose by an average of 25% for free air and by 20% for CTDI phantoms compared to doses with the conventional filter. In addition, its effect in rendering the effective energy uniform resulted in an improvement in image quality. This new HEC filter may be useful in cone-beam CT studies. (note)

  8. Implications of CT noise and artifacts for quantitative 99mTc SPECT/CT imaging

    International Nuclear Information System (INIS)

    Hulme, K. W.; Kappadath, S. C.

    2014-01-01

    Purpose: This paper evaluates the effects of computed tomography (CT) image noise and artifacts on quantitative single-photon emission computed-tomography (SPECT) imaging, with the aim of establishing an appropriate range of CT acquisition parameters for low-dose protocols with respect to accurate SPECT attenuation correction (AC). Methods: SPECT images of two geometric and one anthropomorphic phantom were reconstructed iteratively using CT scans acquired at a range of dose levels (CTDI vol = 0.4 to 46 mGy). Resultant SPECT image quality was evaluated by comparing mean signal, background noise, and artifacts to SPECT images reconstructed using the highest dose CT for AC. Noise injection was performed on linear-attenuation (μ) maps to determine the CT noise threshold for accurate AC. Results: High levels of CT noise (σ ∼ 200–400 HU) resulted in low μ-maps noise (σ ∼ 1%–3%). Noise levels greater than ∼10% in 140 keV μ-maps were required to produce visibly perceptible increases of ∼15% in 99m Tc SPECT images. These noise levels would be achieved at low CT dose levels (CTDI vol = 4 μGy) that are over 2 orders of magnitude lower than the minimum dose for diagnostic CT scanners. CT noise could also lower (bias) the expected μ values. The relative error in reconstructed SPECT signal trended linearly with the relative shift in μ. SPECT signal was, on average, underestimated in regions corresponding with beam-hardening artifacts in CT images. Any process that has the potential to change the CT number of a region by ∼100 HU (e.g., misregistration between CT images and SPECT images due to motion, the presence of contrast in CT images) could introduce errors in μ 140 keV on the order of 10%, that in turn, could introduce errors on the order of ∼10% into the reconstructed 99m Tc SPECT image. Conclusions: The impact of CT noise on SPECT noise was demonstrated to be negligible for clinically achievable CT parameters. Because CT dose levels that affect

  9. Fast reconstruction of industry CT image based on Wintel and P4 structure

    CERN Document Server

    Su Jian Ping; Zhang Li; Zhao Zi Ran; Gao Wen Huan; Kang Ke Jun

    2002-01-01

    Largescale I-CT is used to inspect large workpiece with high spiral resolution and its reconstructed image is very large. So it often relies on special workstation. Now with the development of P4 CPU and Windows2000, it is possible to reconstruct, deal and display I-CT image on Wintel structure. The authors discuss the possibility and future of this scheme. This is important for the improvement of economical value of I-CT

  10. Increasing Cone-beam projection usage by temporal fitting

    DEFF Research Database (Denmark)

    Lyksborg, Mark; Hansen, Mads Fogtmann; Larsen, Rasmus

    2010-01-01

    A Cone-beam CT system can be used to image the lung region. The system records 2D projections which will allow 3D reconstruction however a reconstruction based on all projections will lead to a blurred reconstruction in regions were respiratory motion occur. To avoid this the projections are typi......A Cone-beam CT system can be used to image the lung region. The system records 2D projections which will allow 3D reconstruction however a reconstruction based on all projections will lead to a blurred reconstruction in regions were respiratory motion occur. To avoid this the projections...... in [6] prior knowledge of the lung deformation estimated from the planning CT could be used to include all projections into the reconstruction. It has also been attempted to estimate both the motion and 3D volume simultaneously in [4]. Problems with motion estimation are ill-posed leading to suboptimal...... motion which in return affects the reconstruction. By directly including time into the image representation the effect of suboptimal motion fields are avoided and we are still capable of using phase neighbour projections. The 4D image model is fitted by solving a statistical cost function based...

  11. Clinical application of the three-dimensional reconstruction of spiral CT pneumocolon

    International Nuclear Information System (INIS)

    Yu Shenping; Li Ziping; Xu Dasheng; Lin Erjian; Lin Peizhang; Xu Qiaolan

    2000-01-01

    Objective: To evaluate the clinical role of the 3 types of reconstruction of the spiral CT pneumocolon in the diagnosis of colon lesions. Methods: Three types of reconstruction with spiral CT pneumocolon including air cast imaging (ACI), CT virtual endoscopy (CTVE), and multiple planner reconstruction (MPR) in 34 patients with colorectal cancer or polyps were correlated with surgical pathology respectively. Results: Among the 34 patients, 30 was colorectal cancer and 6 was polyps (2 of which in the proximal lumen of 2 colon cancer). (1) Comparison between the 3 types of the spiral CT pneumocolon reconstruction and pathology in colorectal cancer. 1) ACI: tumor patterns: coincide (n =22), anti-coincide (n = 8); tumor extension: coincide (n = 24), anti-coincide (n = 6); tumor size: coincide (n = 28), anti-coincide (n = 2). 2) CTVE: tumor patterns: coincide (n = 26), anti-coincide (n = 4); tumor extension: coincide (n = 25), anti-coincide ( n 5); tumor size: coincide (n = 23), anti-coincide (n = 7). 3) MPR: tumor patterns: coincide (n = 24), anti-coincide (n = 6); tumor extension: coincide (n = 30), anti-coincide (n = 0); tumor size: coincide (n = 26), anti-coincide (n = 4). (2) Comparison between the 3 types of the spiral CT pneumocolon reconstruction and pathology in colorectal polyps: the lesions were displayed in 4 (ACI) and in 6 (CTVE and MPR). Conclusion: (1) For the diagnosis of colorectal cancers: CTVE was the best means to display the tumor patterns, MPR most correct to judge the tumor extension, and ACI most suitable to measure the tumor size. (2) For the diagnosis of colorectal polyps, ACI can be used for oriented diagnosis, CTVE can well display the intra-luminal three-dimensional structure and can be used for characteristic diagnosis, MPR can be used for differential diagnosis

  12. Comparison of the accuracy of 3-dimensional cone-beam computed tomography and micro-computed tomography reconstructions by using different voxel sizes.

    Science.gov (United States)

    Maret, Delphine; Peters, Ove A; Galibourg, Antoine; Dumoncel, Jean; Esclassan, Rémi; Kahn, Jean-Luc; Sixou, Michel; Telmon, Norbert

    2014-09-01

    Cone-beam computed tomography (CBCT) data are, in principle, metrically exact. However, clinicians need to consider the precision of measurements of dental morphology as well as other hard tissue structures. CBCT spatial resolution, and thus image reconstruction quality, is restricted by the acquisition voxel size. The aim of this study was to assess geometric discrepancies among 3-dimensional CBCT reconstructions relative to the micro-CT reference. A total of 37 permanent teeth from 9 mandibles were scanned with CBCT 9500 and 9000 3D and micro-CT. After semiautomatic segmentation, reconstructions were obtained from CBCT acquisitions (voxel sizes 76, 200, and 300 μm) and from micro-CT (voxel size 41 μm). All reconstructions were positioned in the same plane by image registration. The topography of the geometric discrepancies was displayed by using a color map allowing the maximum differences to be located. The maximum differences were mainly found at the cervical margins and on the cusp tips or incisal edges. Geometric reconstruction discrepancies were significant at 300-μm resolution (P = .01, Wilcoxon test). To study hard tissue morphology, CBCT acquisitions require voxel sizes smaller than 300 μm. This experimental study will have to be complemented by studies in vivo that consider the conditions of clinical practice. Copyright © 2014 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  13. Adaptive statistical iterative reconstruction technology in the application of PET/CT whole body scans

    International Nuclear Information System (INIS)

    Xin Jun; Zhao Zhoushe; Li Hong; Lu Zhe; Wu Wenkai; Guo Qiyong

    2013-01-01

    Objective: To improve image quality of low dose CT in whole body PET/CT using adaptive statistical iterative reconstruction (ASiR) technology. Methods: Twice CT scans were performed with GE water model,scan parameters were: 120 kV, 120 and 300 mA respectively. In addition, 30 subjects treated with PET/CT were selected randomly, whole body PET/CT were performed after 18 F-FDG injection of 3.70 MBq/kg, Sharp IR+time of flight + VUE Point HD technology were used for 1.5 min/bed in PET; CT of spiral scan was performed under 120 kV using automatic exposure control technology (30-210 mA, noise index 25). Model and patients whole body CT images were reconstructed with conventional and 40% ASiR methods respectively, and the CT attenuation value and noise index were measured. Results: Research of model and clinical showed that standard deviation of ASiR method in model CT was 33.0% lower than the conventional CT reconstruction method (t =27.76, P<0.01), standard deviation of CT in normal tissues (brain, lung, mediastinum, liver and vertebral body) and lesions (brain, lung, mediastinum, liver and vertebral body) reduced by 21.08% (t =23.35, P<0.01) and 24.43% (t =16.15, P<0.01) respectively, especially for normal liver tissue and liver lesions, standard deviations of CT were reduced by 51.33% (t=34.21, P<0.0) and 49.54% (t=15.21, P<0.01) respectively. Conclusion: ASiR reconstruction method was significantly reduced the noise of low dose CT image and improved the quality of CT image in whole body PET/CT, which seems more suitable for quantitative analysis and clinical applications. (authors)

  14. Methods of X-ray CT image reconstruction from few projections

    International Nuclear Information System (INIS)

    Wang, H.

    2011-01-01

    To improve the safety (low dose) and the productivity (fast acquisition) of a X-ray CT system, we want to reconstruct a high quality image from a small number of projections. The classical reconstruction algorithms generally fail since the reconstruction procedure is unstable and suffers from artifacts. A new approach based on the recently developed 'Compressed Sensing' (CS) theory assumes that the unknown image is in some sense 'sparse' or 'compressible', and the reconstruction is formulated through a non linear optimization problem (TV/l1 minimization) by enhancing the sparsity. Using the pixel (or voxel in 3D) as basis, to apply the CS framework in CT one usually needs a 'sparsifying' transform, and combines it with the 'X-ray projector' which applies on the pixel image. In this thesis, we have adapted a 'CT-friendly' radial basis of Gaussian family called 'blob' to the CS-CT framework. The blob has better space-frequency localization properties than the pixel, and many operations, such as the X-ray transform, can be evaluated analytically and are highly parallelizable (on GPU platform). Compared to the classical Kaisser-Bessel blob, the new basis has a multi-scale structure: an image is the sum of dilated and translated radial Mexican hat functions. The typical medical objects are compressible under this basis, so the sparse representation system used in the ordinary CS algorithms is no more needed. 2D simulations show that the existing TV and l1 algorithms are more efficient and the reconstructions have better visual quality than the equivalent approach based on the pixel or wavelet basis. The new approach has also been validated on 2D experimental data, where we have observed that in general the number of projections can be reduced to about 50%, without compromising the image quality. (author) [fr

  15. Value of multi-slice spiral CT MPVR reconstruction in the diagnosis of acute appendicitis

    International Nuclear Information System (INIS)

    Wang Kang; Zhao Zehua; Wang Zhi; Wang Weizhong; Xu Songsen; Zhang Miao; Liu Wenjin; Zhang Guozhen; Feng Dianxu

    2005-01-01

    Objective: To investigate the value of multi-slice spiral CT MPVR reconstruction in the diagnosis of acute appendicitis. Methods: A total of 39 patients with clinically suspected acute appendicitis underwent surgery from February, 2002 to September, 2003. They were prospectively examined before surgery with routine CT scanning and MPVR reconstruction spiral CT. 31 cases of appendicitis were confirmed after appendectomy. CT scans and surgery-pathology reports were evaluated on a five-grade scale from hyperemic-edematous appendix to abscess (normal appendix: 0 grade). Results: The results of spiral CT MPVR reconstruction were compared with the surgical and pathologic findings at appendectomy, yielding an accuracy of 87.2%, sensitivity of 90.3%, specificity of 75%, positive predictive value of 93.3%, and negative predictive value of 66.7%, respectively. Results of routine CT yielded an accuracy of 38.5%, sensitivity of 38.7%, specificity of 37.5%, positive predictive value of 70.6%, and negative predictive value of 13.6%, respectively. MPVR reconstruction signs of 28 patients with acute appendicitis included enlarged appendix ( > 6 mm) (96.4%), appendicoliths (26.7%), caecal apical thickening (36.7%), periappendiceal inflammation (71.4%), and abscess (10.7%). Conclusion: The use of spiral CT MPVR reconstruction in patients with equivocal clinical presentation suspected of having acute appendicitis can lead to a significant improvement in the preoperative diagnosis and maybe a decrease in surgical-pathologic severity of appendiceal disease. (authors)

  16. Iterative reconstruction technique with reduced volume CT dose index: diagnostic accuracy in pediatric acute appendicitis

    International Nuclear Information System (INIS)

    Didier, Ryne A.; Vajtai, Petra L.; Hopkins, Katharine L.

    2015-01-01

    Iterative reconstruction technique has been proposed as a means of reducing patient radiation dose in pediatric CT. Yet, the effect of such reductions on diagnostic accuracy has not been thoroughly evaluated. This study compares accuracy of diagnosing pediatric acute appendicitis using contrast-enhanced abdominopelvic CT scans performed with traditional pediatric weight-based protocols and filtered back projection reconstruction vs. a filtered back projection/iterative reconstruction technique blend with reduced volume CT dose index (CTDI vol ). Results of pediatric contrast-enhanced abdominopelvic CT scans done for pain and/or suspected appendicitis were reviewed in two groups: A, 192 scans performed with the hospital's established weight-based CT protocols and filtered back projection reconstruction; B, 194 scans performed with iterative reconstruction technique and reduced CTDI vol . Reduced CTDI vol was achieved primarily by reductions in effective tube current-time product (mAs eff ) and tube peak kilovoltage (kVp). CT interpretation was correlated with clinical follow-up and/or surgical pathology. CTDI vol , size-specific dose estimates (SSDE) and performance characteristics of the two CT techniques were then compared. Between groups A and B, mean CTDI vol was reduced by 45%, and mean SSDE was reduced by 46%. Sensitivity, specificity and diagnostic accuracy were 96%, 97% and 96% in group A vs. 100%, 99% and 99% in group B. Accuracy in diagnosing pediatric acute appendicitis was maintained in contrast-enhanced abdominopelvic CT scans that incorporated iterative reconstruction technique, despite reductions in mean CTDI vol and SSDE by nearly half as compared to the hospital's traditional weight-based protocols. (orig.)

  17. Fixed, object-specific intensity compensation for cone beam optical CT radiation dosimetry

    Science.gov (United States)

    Dekker, Kurtis H.; Hazarika, Rubin; Silveira, Matheus A.; Jordan, Kevin J.

    2018-03-01

    Optical cone beam computed tomography (CT) scanning of radiochromic gel dosimeters, using a CCD camera and a low stray light convergent source, provides fast, truly 3D radiation dosimetry with high accuracy. However, a key limiting factor in radiochromic gel dosimetry at large (⩾10 cm diameter) volumes is the initial attenuation of the dosimeters. It is not unusual to observe a 5–10×  difference in signal intensity through the dosimeter center versus through the surrounding medium in pre-irradiation images. Thus, all dosimetric information in a typical experiment is measured within the lower 10%–20% of the camera sensor’s range, and re-use of gels is often not possible due to a lack of transmission. To counteract this, in this note we describe a simple method to create source compensators by printing on transparent films. This technique, which is easily implemented and inexpensive, is an optical analogue to the bowtie filter in x-ray CT. We present transmission images and solution phantom reconstructions to demonstrate that (1) placing compensators beyond the focal zone of the imaging lens prevents high spatial frequency features of the printed films from generating reconstruction artifacts, and (2) object-specific compensation considerably reduces the range of intensities measured in projection images. This will improve the measurable dose range in optical CT dosimetry, and will enable imaging of larger gel volumes (∼15 cm diameter). Additionally, it should enable re-use of dosimeters by printing a new compensator for a second experiment.

  18. Technical Note: FreeCT_ICD: An Open Source Implementation of a Model-Based Iterative Reconstruction Method using Coordinate Descent Optimization for CT Imaging Investigations.

    Science.gov (United States)

    Hoffman, John M; Noo, Frédéric; Young, Stefano; Hsieh, Scott S; McNitt-Gray, Michael

    2018-06-01

    To facilitate investigations into the impacts of acquisition and reconstruction parameters on quantitative imaging, radiomics and CAD using CT imaging, we previously released an open source implementation of a conventional weighted filtered backprojection reconstruction called FreeCT_wFBP. Our purpose was to extend that work by providing an open-source implementation of a model-based iterative reconstruction method using coordinate descent optimization, called FreeCT_ICD. Model-based iterative reconstruction offers the potential for substantial radiation dose reduction, but can impose substantial computational processing and storage requirements. FreeCT_ICD is an open source implementation of a model-based iterative reconstruction method that provides a reasonable tradeoff between these requirements. This was accomplished by adapting a previously proposed method that allows the system matrix to be stored with a reasonable memory requirement. The method amounts to describing the attenuation coefficient using rotating slices that follow the helical geometry. In the initially-proposed version, the rotating slices are themselves described using blobs. We have replaced this description by a unique model that relies on tri-linear interpolation together with the principles of Joseph's method. This model offers an improvement in memory requirement while still allowing highly accurate reconstruction for conventional CT geometries. The system matrix is stored column-wise and combined with an iterative coordinate descent (ICD) optimization. The result is FreeCT_ICD, which is a reconstruction program developed on the Linux platform using C++ libraries and the open source GNU GPL v2.0 license. The software is capable of reconstructing raw projection data of helical CT scans. In this work, the software has been described and evaluated by reconstructing datasets exported from a clinical scanner which consisted of an ACR accreditation phantom dataset and a clinical pediatric

  19. Cone-beam CT in paediatric dentistry. DIMITRA project position statement

    International Nuclear Information System (INIS)

    Oenning, Anne Caroline; Jacobs, Reinhilde; Pauwels, Ruben; Stratis, Andreas; Hedesiu, Mihaela; Salmon, Benjamin

    2018-01-01

    DIMITRA (dentomaxillofacial paediatric imaging: an investigation towards low-dose radiation induced risks) is a European multicenter and multidisciplinary project focused on optimizing cone-beam CT exposures for children and adolescents. With increasing use of cone-beam CT for dentomaxillofacial diagnostics, concern arises regarding radiation risks associated with this imaging modality, especially for children. Research evidence concerning cone-beam CT indications in children remains limited, while reports mention inconsistent recommendations for dose reduction. Furthermore, there is no paper using the combined and integrated information on the required indication-oriented image quality and the related patient dose levels. In this paper, therefore, the authors initiate an integrated approach based on current evidence regarding image quality and dose, together with the expertise of DIMITRA's members searching for a state of the art. The aim of this DIMITRA position statement is to provide indication-oriented and patient-specific recommendations regarding the main cone-beam CT applications in the pediatric field. The authors will review this position statement document when results regarding multidisciplinary approaches evolve, in a period of 5 years or earlier. (orig.)

  20. Computed tomographic reconstruction of beam profiles with a multi-wire chamber

    International Nuclear Information System (INIS)

    Alonso, J.R.; Tobias, C.A.; Chu, W.T.

    1979-03-01

    MEDUSA (MEdical Dose Uniformity SAmpler), a 16 plane multi-wire proportional chamber, has been built to accurately measure beam profiles. The large number of planes allows for reconstruction of highly detailed beam intensity structures by means of Fourier convolution reconstruction techniques. This instrument is being used for verification and tuning of the Bevalac radiotherapy beams, but has potential applications in many beam profile monitoring situations

  1. Determination of quantitative tissue composition by iterative reconstruction on 3D DECT volumes

    Energy Technology Data Exchange (ETDEWEB)

    Magnusson, Maria [Linkoeping Univ. (Sweden). Dept. of Electrical Engineering; Linkoeping Univ. (Sweden). Dept. of Medical and Health Sciences, Radiation Physics; Linkoeping Univ. (Sweden). Center for Medical Image Science and Visualization (CMIV); Malusek, Alexandr [Linkoeping Univ. (Sweden). Dept. of Medical and Health Sciences, Radiation Physics; Linkoeping Univ. (Sweden). Center for Medical Image Science and Visualization (CMIV); Nuclear Physics Institute AS CR, Prague (Czech Republic). Dept. of Radiation Dosimetry; Muhammad, Arif [Linkoeping Univ. (Sweden). Dept. of Medical and Health Sciences, Radiation Physics; Carlsson, Gudrun Alm [Linkoeping Univ. (Sweden). Dept. of Medical and Health Sciences, Radiation Physics; Linkoeping Univ. (Sweden). Center for Medical Image Science and Visualization (CMIV)

    2011-07-01

    Quantitative tissue classification using dual-energy CT has the potential to improve accuracy in radiation therapy dose planning as it provides more information about material composition of scanned objects than the currently used methods based on single-energy CT. One problem that hinders successful application of both single- and dual-energy CT is the presence of beam hardening and scatter artifacts in reconstructed data. Current pre- and post-correction methods used for image reconstruction often bias CT attenuation values and thus limit their applicability for quantitative tissue classification. Here we demonstrate simulation studies with a novel iterative algorithm that decomposes every soft tissue voxel into three base materials: water, protein, and adipose. The results demonstrate that beam hardening artifacts can effectively be removed and accurate estimation of mass fractions of each base material can be achieved. Our iterative algorithm starts with calculating parallel projections on two previously reconstructed DECT volumes reconstructed from fan-beam or helical projections with small conebeam angle. The parallel projections are then used in an iterative loop. Future developments include segmentation of soft and bone tissue and subsequent determination of bone composition. (orig.)

  2. Dose reduction with adaptive statistical iterative reconstruction for paediatric CT: phantom study and clinical experience on chest and abdomen CT

    Energy Technology Data Exchange (ETDEWEB)

    Gay, F.; Lasalle, S.; Neuenschwander, S.; Brisse, H.J. [Institut Curie, Imaging Department, Paris (France); Pavia, Y.; Pierrat, N. [Institut Curie, Medical Physics Department, Paris (France)

    2014-01-15

    To assess the benefit and limits of iterative reconstruction of paediatric chest and abdominal computed tomography (CT). The study compared adaptive statistical iterative reconstruction (ASIR) with filtered back projection (FBP) on 64-channel MDCT. A phantom study was first performed using variable tube potential, tube current and ASIR settings. The assessed image quality indices were the signal-to-noise ratio (SNR), the noise power spectrum, low contrast detectability (LCD) and spatial resolution. A clinical retrospective study of 26 children (M:F = 14/12, mean age: 4 years, range: 1-9 years) was secondarily performed allowing comparison of 18 chest and 14 abdominal CT pairs, one with a routine CT dose and FBP reconstruction, and the other with 30 % lower dose and 40 % ASIR reconstruction. Two radiologists independently compared the images for overall image quality, noise, sharpness and artefacts, and measured image noise. The phantom study demonstrated a significant increase in SNR without impairment of the LCD or spatial resolution, except for tube current values below 30-50 mA. On clinical images, no significant difference was observed between FBP and reduced dose ASIR images. Iterative reconstruction allows at least 30 % dose reduction in paediatric chest and abdominal CT, without impairment of image quality. (orig.)

  3. Dose reduction with adaptive statistical iterative reconstruction for paediatric CT: phantom study and clinical experience on chest and abdomen CT

    International Nuclear Information System (INIS)

    Gay, F.; Lasalle, S.; Neuenschwander, S.; Brisse, H.J.; Pavia, Y.; Pierrat, N.

    2014-01-01

    To assess the benefit and limits of iterative reconstruction of paediatric chest and abdominal computed tomography (CT). The study compared adaptive statistical iterative reconstruction (ASIR) with filtered back projection (FBP) on 64-channel MDCT. A phantom study was first performed using variable tube potential, tube current and ASIR settings. The assessed image quality indices were the signal-to-noise ratio (SNR), the noise power spectrum, low contrast detectability (LCD) and spatial resolution. A clinical retrospective study of 26 children (M:F = 14/12, mean age: 4 years, range: 1-9 years) was secondarily performed allowing comparison of 18 chest and 14 abdominal CT pairs, one with a routine CT dose and FBP reconstruction, and the other with 30 % lower dose and 40 % ASIR reconstruction. Two radiologists independently compared the images for overall image quality, noise, sharpness and artefacts, and measured image noise. The phantom study demonstrated a significant increase in SNR without impairment of the LCD or spatial resolution, except for tube current values below 30-50 mA. On clinical images, no significant difference was observed between FBP and reduced dose ASIR images. Iterative reconstruction allows at least 30 % dose reduction in paediatric chest and abdominal CT, without impairment of image quality. (orig.)

  4. Metal artefact reduction for a dental cone beam CT image using image segmentation and backprojection filters

    International Nuclear Information System (INIS)

    Mohammadi, Mahdi; Khotanlou, Hassan; Mohammadi, Mohammad

    2011-01-01

    Full text: Due to low dose delivery and fast scanning, the dental Cone Beam CT (CBCT) is the latest technology being implanted for a range of dental imaging. The presence of metallic objects including amalgam or gold fillings in the mouth produces an intuitive image for human jaws. The feasibility of a fast and accurate approach for metal artefact reduction for dental CBCT is investigated. The current study investigates the metal artefact reduction using image segmentation and modification of several sinigrams. In order to reduce metal effects such as beam hardening, streak artefact and intense noises, the application of several algorithms is evaluated. The proposed method includes three stages: preprocessing, reconstruction and post-processing. In the pre-processing stage, in order to reduce the noise level, several phase and frequency filters were applied. At the second stage, based on the specific sinogram achieved for each segment, spline interpolation and weighting backprojection filters were applied to reconstruct the original image. A three-dimensional filter was then applied on reconstructed images, to improve the image quality. Results showed that compared to other available filters, standard frequency filters have a significant influence in the preprocessing stage (ΔHU = 48 ± 6). In addition, with the streak artefact, the probability of beam hardening artefact increases. t e post-processing stage, the application of three-dimensional filters improves the quality of reconstructed images (See Fig. I). Conclusion The proposed method reduces metal artefacts especially where there are more than one metal implanted in the region of interest.

  5. Ultralow dose computed tomography attenuation correction for pediatric PET CT using adaptive statistical iterative reconstruction

    International Nuclear Information System (INIS)

    Brady, Samuel L.; Shulkin, Barry L.

    2015-01-01

    Purpose: To develop ultralow dose computed tomography (CT) attenuation correction (CTAC) acquisition protocols for pediatric positron emission tomography CT (PET CT). Methods: A GE Discovery 690 PET CT hybrid scanner was used to investigate the change to quantitative PET and CT measurements when operated at ultralow doses (10–35 mA s). CT quantitation: noise, low-contrast resolution, and CT numbers for 11 tissue substitutes were analyzed in-phantom. CT quantitation was analyzed to a reduction of 90% volume computed tomography dose index (0.39/3.64; mGy) from baseline. To minimize noise infiltration, 100% adaptive statistical iterative reconstruction (ASiR) was used for CT reconstruction. PET images were reconstructed with the lower-dose CTAC iterations and analyzed for: maximum body weight standardized uptake value (SUV bw ) of various diameter targets (range 8–37 mm), background uniformity, and spatial resolution. Radiation dose and CTAC noise magnitude were compared for 140 patient examinations (76 post-ASiR implementation) to determine relative dose reduction and noise control. Results: CT numbers were constant to within 10% from the nondose reduced CTAC image for 90% dose reduction. No change in SUV bw , background percent uniformity, or spatial resolution for PET images reconstructed with CTAC protocols was found down to 90% dose reduction. Patient population effective dose analysis demonstrated relative CTAC dose reductions between 62% and 86% (3.2/8.3–0.9/6.2). Noise magnitude in dose-reduced patient images increased but was not statistically different from predose-reduced patient images. Conclusions: Using ASiR allowed for aggressive reduction in CT dose with no change in PET reconstructed images while maintaining sufficient image quality for colocalization of hybrid CT anatomy and PET radioisotope uptake

  6. Ultralow dose computed tomography attenuation correction for pediatric PET CT using adaptive statistical iterative reconstruction

    Energy Technology Data Exchange (ETDEWEB)

    Brady, Samuel L., E-mail: samuel.brady@stjude.org [Division of Diagnostic Imaging, St. Jude Children’s Research Hospital, Memphis, Tennessee 38105 (United States); Shulkin, Barry L. [Nuclear Medicine and Department of Radiological Sciences, St. Jude Children’s Research Hospital, Memphis, Tennessee 38105 (United States)

    2015-02-15

    Purpose: To develop ultralow dose computed tomography (CT) attenuation correction (CTAC) acquisition protocols for pediatric positron emission tomography CT (PET CT). Methods: A GE Discovery 690 PET CT hybrid scanner was used to investigate the change to quantitative PET and CT measurements when operated at ultralow doses (10–35 mA s). CT quantitation: noise, low-contrast resolution, and CT numbers for 11 tissue substitutes were analyzed in-phantom. CT quantitation was analyzed to a reduction of 90% volume computed tomography dose index (0.39/3.64; mGy) from baseline. To minimize noise infiltration, 100% adaptive statistical iterative reconstruction (ASiR) was used for CT reconstruction. PET images were reconstructed with the lower-dose CTAC iterations and analyzed for: maximum body weight standardized uptake value (SUV{sub bw}) of various diameter targets (range 8–37 mm), background uniformity, and spatial resolution. Radiation dose and CTAC noise magnitude were compared for 140 patient examinations (76 post-ASiR implementation) to determine relative dose reduction and noise control. Results: CT numbers were constant to within 10% from the nondose reduced CTAC image for 90% dose reduction. No change in SUV{sub bw}, background percent uniformity, or spatial resolution for PET images reconstructed with CTAC protocols was found down to 90% dose reduction. Patient population effective dose analysis demonstrated relative CTAC dose reductions between 62% and 86% (3.2/8.3–0.9/6.2). Noise magnitude in dose-reduced patient images increased but was not statistically different from predose-reduced patient images. Conclusions: Using ASiR allowed for aggressive reduction in CT dose with no change in PET reconstructed images while maintaining sufficient image quality for colocalization of hybrid CT anatomy and PET radioisotope uptake.

  7. High-quality 3D correction of ring and radiant artifacts in flat panel detector-based cone beam volume CT imaging

    Science.gov (United States)

    Abu Anas, Emran Mohammad; Kim, Jae Gon; Lee, Soo Yeol; Kamrul Hasan, Md

    2011-10-01

    The use of an x-ray flat panel detector is increasingly becoming popular in 3D cone beam volume CT machines. Due to the deficient semiconductor array manufacturing process, the cone beam projection data are often corrupted by different types of abnormalities, which cause severe ring and radiant artifacts in a cone beam reconstruction image, and as a result, the diagnostic image quality is degraded. In this paper, a novel technique is presented for the correction of error in the 2D cone beam projections due to abnormalities often observed in 2D x-ray flat panel detectors. Template images are derived from the responses of the detector pixels using their statistical properties and then an effective non-causal derivative-based detection algorithm in 2D space is presented for the detection of defective and mis-calibrated detector elements separately. An image inpainting-based 3D correction scheme is proposed for the estimation of responses of defective detector elements, and the responses of the mis-calibrated detector elements are corrected using the normalization technique. For real-time implementation, a simplification of the proposed off-line method is also suggested. Finally, the proposed algorithms are tested using different real cone beam volume CT images and the experimental results demonstrate that the proposed methods can effectively remove ring and radiant artifacts from cone beam volume CT images compared to other reported techniques in the literature.

  8. High-quality 3D correction of ring and radiant artifacts in flat panel detector-based cone beam volume CT imaging

    International Nuclear Information System (INIS)

    Anas, Emran Mohammad Abu; Hasan, Md Kamrul; Kim, Jae Gon; Lee, Soo Yeol

    2011-01-01

    The use of an x-ray flat panel detector is increasingly becoming popular in 3D cone beam volume CT machines. Due to the deficient semiconductor array manufacturing process, the cone beam projection data are often corrupted by different types of abnormalities, which cause severe ring and radiant artifacts in a cone beam reconstruction image, and as a result, the diagnostic image quality is degraded. In this paper, a novel technique is presented for the correction of error in the 2D cone beam projections due to abnormalities often observed in 2D x-ray flat panel detectors. Template images are derived from the responses of the detector pixels using their statistical properties and then an effective non-causal derivative-based detection algorithm in 2D space is presented for the detection of defective and mis-calibrated detector elements separately. An image inpainting-based 3D correction scheme is proposed for the estimation of responses of defective detector elements, and the responses of the mis-calibrated detector elements are corrected using the normalization technique. For real-time implementation, a simplification of the proposed off-line method is also suggested. Finally, the proposed algorithms are tested using different real cone beam volume CT images and the experimental results demonstrate that the proposed methods can effectively remove ring and radiant artifacts from cone beam volume CT images compared to other reported techniques in the literature.

  9. Comparison of CT numbers between cone-beam CT and multi-detector CT

    International Nuclear Information System (INIS)

    Kim, Dong Soo; Han, Won Jeong; Kim, Eun Kyung

    2010-01-01

    To compare the CT numbers on 3 cone-beam CT (CBCT) images with those on multi-detector CT (MDCT) image using CT phantom and to develop linear regressive equations using CT numbers to material density for all the CT scanner each. Mini CT phantom comprised of five 1 inch thick cylindrical models with 1.125 inches diameter of materials with different densities (polyethylene, polystyrene, plastic water, nylon and acrylic) was used. It was scanned in 3 CBCTs (i-CAT, Alphard VEGA, Implagraphy SC) and 1 MDCT (Somatom Emotion). The images were saved as DICOM format and CT numbers were measured using OnDemand 3D. CT numbers obtained from CBCTs and MDCT images were compared and linear regression analysis was performed for the density, ρ(g/cm 3 ), as the dependent variable in terms of the CT numbers obtained from CBCTs and MDCT images. CT numbers on i-CAT and Implagraphy CBCT images were smaller than those on Somatom Emotion MDCT image (p<0.05). Linear relationship on a range of materials used for this study were ρ=0.001 H+1.07 with R2 value of 0.999 for Somatom Emotion, ρ=0.002 H+1.09 with R2 value of 0.991 for Alphard VEGA, ρ=0.001 H+1.43 with R2 value of 0.980 for i-CAT and ρ=0.001 H+1.30 with R2 value of 0.975 for Implagraphy. CT numbers on i-CAT and Implagraphy CBCT images were not same as those on Somatom Emotion MDCT image. The linear regressive equations to determine the density from the CT numbers with very high correlation coefficient were obtained on three CBCT and MDCT scan.

  10. Comparison of CT numbers between cone-beam CT and multi-detector CT

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Dong Soo; Han, Won Jeong; Kim, Eun Kyung [Department of Oral and Maxillofacial Radiology, School of Dentistry, Dankook University, Cheonan (Korea, Republic of)

    2010-06-15

    To compare the CT numbers on 3 cone-beam CT (CBCT) images with those on multi-detector CT (MDCT) image using CT phantom and to develop linear regressive equations using CT numbers to material density for all the CT scanner each. Mini CT phantom comprised of five 1 inch thick cylindrical models with 1.125 inches diameter of materials with different densities (polyethylene, polystyrene, plastic water, nylon and acrylic) was used. It was scanned in 3 CBCTs (i-CAT, Alphard VEGA, Implagraphy SC) and 1 MDCT (Somatom Emotion). The images were saved as DICOM format and CT numbers were measured using OnDemand 3D. CT numbers obtained from CBCTs and MDCT images were compared and linear regression analysis was performed for the density, {rho}(g/cm{sup 3}), as the dependent variable in terms of the CT numbers obtained from CBCTs and MDCT images. CT numbers on i-CAT and Implagraphy CBCT images were smaller than those on Somatom Emotion MDCT image (p<0.05). Linear relationship on a range of materials used for this study were {rho}=0.001 H+1.07 with R2 value of 0.999 for Somatom Emotion, {rho}=0.002 H+1.09 with R2 value of 0.991 for Alphard VEGA, {rho}=0.001 H+1.43 with R2 value of 0.980 for i-CAT and {rho}=0.001 H+1.30 with R2 value of 0.975 for Implagraphy. CT numbers on i-CAT and Implagraphy CBCT images were not same as those on Somatom Emotion MDCT image. The linear regressive equations to determine the density from the CT numbers with very high correlation coefficient were obtained on three CBCT and MDCT scan.

  11. Iterative reconstruction technique with reduced volume CT dose index: diagnostic accuracy in pediatric acute appendicitis

    Energy Technology Data Exchange (ETDEWEB)

    Didier, Ryne A. [Oregon Health and Science University, Department of Diagnostic Radiology, DC7R, Portland, OR (United States); Vajtai, Petra L. [Oregon Health and Science University, Department of Pediatrics, Portland, OR (United States); Oregon Health and Science University, Department of Diagnostic Radiology, DC7R, Portland, OR (United States); Hopkins, Katharine L. [Oregon Health and Science University, Department of Diagnostic Radiology, DC7R, Portland, OR (United States); Oregon Health and Science University, Department of Pediatrics, Portland, OR (United States)

    2014-07-05

    Iterative reconstruction technique has been proposed as a means of reducing patient radiation dose in pediatric CT. Yet, the effect of such reductions on diagnostic accuracy has not been thoroughly evaluated. This study compares accuracy of diagnosing pediatric acute appendicitis using contrast-enhanced abdominopelvic CT scans performed with traditional pediatric weight-based protocols and filtered back projection reconstruction vs. a filtered back projection/iterative reconstruction technique blend with reduced volume CT dose index (CTDI{sub vol}). Results of pediatric contrast-enhanced abdominopelvic CT scans done for pain and/or suspected appendicitis were reviewed in two groups: A, 192 scans performed with the hospital's established weight-based CT protocols and filtered back projection reconstruction; B, 194 scans performed with iterative reconstruction technique and reduced CTDI{sub vol}. Reduced CTDI{sub vol} was achieved primarily by reductions in effective tube current-time product (mAs{sub eff}) and tube peak kilovoltage (kVp). CT interpretation was correlated with clinical follow-up and/or surgical pathology. CTDI{sub vol}, size-specific dose estimates (SSDE) and performance characteristics of the two CT techniques were then compared. Between groups A and B, mean CTDI{sub vol} was reduced by 45%, and mean SSDE was reduced by 46%. Sensitivity, specificity and diagnostic accuracy were 96%, 97% and 96% in group A vs. 100%, 99% and 99% in group B. Accuracy in diagnosing pediatric acute appendicitis was maintained in contrast-enhanced abdominopelvic CT scans that incorporated iterative reconstruction technique, despite reductions in mean CTDI{sub vol} and SSDE by nearly half as compared to the hospital's traditional weight-based protocols. (orig.)

  12. Towards an inline reconstruction architecture for micro-CT systems

    International Nuclear Information System (INIS)

    Brasse, David; Humbert, Bernard; Mathelin, Carole; Rio, Marie-Christine; Guyonnet, Jean-Louis

    2005-01-01

    Recent developments in micro-CT have revolutionized the ability to examine in vivo living experimental animal models such as mouse with a spatial resolution less than 50 μm. The main requirements of in vivo imaging for biological researchers are a good spatial resolution, a low dose induced to the animal during the full examination and a reduced acquisition and reconstruction time for screening purposes. We introduce inline acquisition and reconstruction architecture to obtain in real time the 3D attenuation map of the animal fulfilling the three previous requirements. The micro-CT system is based on commercially available x-ray detector and micro-focus x-ray source. The reconstruction architecture is based on a cluster of PCs where a dedicated communication scheme combining serial and parallel treatments is implemented. In order to obtain high performance transmission rate between the detector and the reconstruction architecture, a dedicated data acquisition system is also developed. With the proposed solution, the time required to filter and backproject a projection of 2048 x 2048 pixels inside a volume of 140 mega voxels using the Feldkamp algorithm is similar to 500 ms, the time needed to acquire the same projection

  13. TH-A-18C-04: Ultrafast Cone-Beam CT Scatter Correction with GPU-Based Monte Carlo Simulation

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Y [UT Southwestern Medical Center, Dallas, TX (United States); Southern Medical University, Guangzhou (China); Bai, T [UT Southwestern Medical Center, Dallas, TX (United States); Xi' an Jiaotong University, Xi' an (China); Yan, H; Ouyang, L; Wang, J; Pompos, A; Jiang, S; Jia, X [UT Southwestern Medical Center, Dallas, TX (United States); Zhou, L [Southern Medical University, Guangzhou (China)

    2014-06-15

    Purpose: Scatter artifacts severely degrade image quality of cone-beam CT (CBCT). We present an ultrafast scatter correction framework by using GPU-based Monte Carlo (MC) simulation and prior patient CT image, aiming at automatically finish the whole process including both scatter correction and reconstructions within 30 seconds. Methods: The method consists of six steps: 1) FDK reconstruction using raw projection data; 2) Rigid Registration of planning CT to the FDK results; 3) MC scatter calculation at sparse view angles using the planning CT; 4) Interpolation of the calculated scatter signals to other angles; 5) Removal of scatter from the raw projections; 6) FDK reconstruction using the scatter-corrected projections. In addition to using GPU to accelerate MC photon simulations, we also use a small number of photons and a down-sampled CT image in simulation to further reduce computation time. A novel denoising algorithm is used to eliminate MC scatter noise caused by low photon numbers. The method is validated on head-and-neck cases with simulated and clinical data. Results: We have studied impacts of photo histories, volume down sampling factors on the accuracy of scatter estimation. The Fourier analysis was conducted to show that scatter images calculated at 31 angles are sufficient to restore those at all angles with <0.1% error. For the simulated case with a resolution of 512×512×100, we simulated 10M photons per angle. The total computation time is 23.77 seconds on a Nvidia GTX Titan GPU. The scatter-induced shading/cupping artifacts are substantially reduced, and the average HU error of a region-of-interest is reduced from 75.9 to 19.0 HU. Similar results were found for a real patient case. Conclusion: A practical ultrafast MC-based CBCT scatter correction scheme is developed. The whole process of scatter correction and reconstruction is accomplished within 30 seconds. This study is supported in part by NIH (1R01CA154747-01), The Core Technology Research

  14. Implementation of a cone-beam reconstruction algorithm for the single-circle source orbit with embedded misalignment correction using homogeneous coordinates

    International Nuclear Information System (INIS)

    Karolczak, Marek; Schaller, Stefan; Engelke, Klaus; Lutz, Andreas; Taubenreuther, Ulrike; Wiesent, Karl; Kalender, Willi

    2001-01-01

    We present an efficient implementation of an approximate cone-beam image reconstruction algorithm for application in tomography, which accounts for scanner mechanical misalignment. The implementation is based on the algorithm proposed by Feldkamp et al. [J. Opt. Soc. Am. A 6, 612-619 (1984)] and is directed at circular scan paths. The algorithm has been developed for the purpose of reconstructing volume data from projections acquired in an experimental x-ray microtomography (μCT) scanner [Engelke et al., Der Radiologe 39, 203-212 (1999)]. To mathematically model misalignment we use matrix notation with homogeneous coordinates to describe the scanner geometry, its misalignment, and the acquisition process. For convenience analysis is carried out for x-ray CT scanners, but it is applicable to any tomographic modality, where two-dimensional projection acquisition in cone beam geometry takes place, e.g., single photon emission computerized tomography. We derive an algorithm assuming misalignment errors to be small enough to weight and filter original projections and to embed compensation for misalignment in the backprojection. We verify the algorithm on simulations of virtual phantoms and scans of a physical multidisk (Defrise) phantom

  15. Ultra-low dose CT attenuation correction for PET/CT: analysis of sparse view data acquisition and reconstruction algorithms

    Science.gov (United States)

    Rui, Xue; Cheng, Lishui; Long, Yong; Fu, Lin; Alessio, Adam M.; Asma, Evren; Kinahan, Paul E.; De Man, Bruno

    2015-01-01

    For PET/CT systems, PET image reconstruction requires corresponding CT images for anatomical localization and attenuation correction. In the case of PET respiratory gating, multiple gated CT scans can offer phase-matched attenuation and motion correction, at the expense of increased radiation dose. We aim to minimize the dose of the CT scan, while preserving adequate image quality for the purpose of PET attenuation correction by introducing sparse view CT data acquisition. Methods We investigated sparse view CT acquisition protocols resulting in ultra-low dose CT scans designed for PET attenuation correction. We analyzed the tradeoffs between the number of views and the integrated tube current per view for a given dose using CT and PET simulations of a 3D NCAT phantom with lesions inserted into liver and lung. We simulated seven CT acquisition protocols with {984, 328, 123, 41, 24, 12, 8} views per rotation at a gantry speed of 0.35 seconds. One standard dose and four ultra-low dose levels, namely, 0.35 mAs, 0.175 mAs, 0.0875 mAs, and 0.04375 mAs, were investigated. Both the analytical FDK algorithm and the Model Based Iterative Reconstruction (MBIR) algorithm were used for CT image reconstruction. We also evaluated the impact of sinogram interpolation to estimate the missing projection measurements due to sparse view data acquisition. For MBIR, we used a penalized weighted least squares (PWLS) cost function with an approximate total-variation (TV) regularizing penalty function. We compared a tube pulsing mode and a continuous exposure mode for sparse view data acquisition. Global PET ensemble root-mean-squares-error (RMSE) and local ensemble lesion activity error were used as quantitative evaluation metrics for PET image quality. Results With sparse view sampling, it is possible to greatly reduce the CT scan dose when it is primarily used for PET attenuation correction with little or no measureable effect on the PET image. For the four ultra-low dose levels

  16. Improving thoracic four-dimensional cone-beam CT reconstruction with anatomical-adaptive image regularization (AAIR)

    International Nuclear Information System (INIS)

    Shieh, Chun-Chien; Kipritidis, John; O'Brien, Ricky T; Cooper, Benjamin J; Keall, Paul J; Kuncic, Zdenka

    2015-01-01

    Total-variation (TV) minimization reconstructions can significantly reduce noise and streaks in thoracic four-dimensional cone-beam computed tomography (4D CBCT) images compared to the Feldkamp–Davis–Kress (FDK) algorithm currently used in practice. TV minimization reconstructions are, however, prone to over-smoothing anatomical details and are also computationally inefficient. The aim of this study is to demonstrate a proof of concept that these disadvantages can be overcome by incorporating the general knowledge of the thoracic anatomy via anatomy segmentation into the reconstruction. The proposed method, referred as the anatomical-adaptive image regularization (AAIR) method, utilizes the adaptive-steepest-descent projection-onto-convex-sets (ASD-POCS) framework, but introduces an additional anatomy segmentation step in every iteration. The anatomy segmentation information is implemented in the reconstruction using a heuristic approach to adaptively suppress over-smoothing at anatomical structures of interest. The performance of AAIR depends on parameters describing the weighting of the anatomy segmentation prior and segmentation threshold values. A sensitivity study revealed that the reconstruction outcome is not sensitive to these parameters as long as they are chosen within a suitable range. AAIR was validated using a digital phantom and a patient scan and was compared to FDK, ASD-POCS and the prior image constrained compressed sensing (PICCS) method. For the phantom case, AAIR reconstruction was quantitatively shown to be the most accurate as indicated by the mean absolute difference and the structural similarity index. For the patient case, AAIR resulted in the highest signal-to-noise ratio (i.e. the lowest level of noise and streaking) and the highest contrast-to-noise ratios for the tumor and the bony anatomy (i.e. the best visibility of anatomical details). Overall, AAIR was much less prone to over-smoothing anatomical details compared to ASD-POCS and

  17. Optimization of Proton CT Detector System and Image Reconstruction Algorithm for On-Line Proton Therapy.

    Directory of Open Access Journals (Sweden)

    Chae Young Lee

    Full Text Available The purposes of this study were to optimize a proton computed tomography system (pCT for proton range verification and to confirm the pCT image reconstruction algorithm based on projection images generated with optimized parameters. For this purpose, we developed a new pCT scanner using the Geometry and Tracking (GEANT 4.9.6 simulation toolkit. GEANT4 simulations were performed to optimize the geometric parameters representing the detector thickness and the distance between the detectors for pCT. The system consisted of four silicon strip detectors for particle tracking and a calorimeter to measure the residual energies of the individual protons. The optimized pCT system design was then adjusted to ensure that the solution to a CS-based convex optimization problem would converge to yield the desired pCT images after a reasonable number of iterative corrections. In particular, we used a total variation-based formulation that has been useful in exploiting prior knowledge about the minimal variations of proton attenuation characteristics in the human body. Examinations performed using our CS algorithm showed that high-quality pCT images could be reconstructed using sets of 72 projections within 20 iterations and without any streaks or noise, which can be caused by under-sampling and proton starvation. Moreover, the images yielded by this CS algorithm were found to be of higher quality than those obtained using other reconstruction algorithms. The optimized pCT scanner system demonstrated the potential to perform high-quality pCT during on-line image-guided proton therapy, without increasing the imaging dose, by applying our CS based proton CT reconstruction algorithm. Further, we make our optimized detector system and CS-based proton CT reconstruction algorithm potentially useful in on-line proton therapy.

  18. A motion-compensated cone-beam CT using electrical impedance tomography imaging

    International Nuclear Information System (INIS)

    Pengpan, T; Smith, N D; Qiu, W; Yao, A; Mitchell, C N; Soleimani, M

    2011-01-01

    Cone-beam CT (CBCT) is an imaging technique used in conjunction with radiation therapy. For example CBCT is used to verify the position of lung cancer tumours just prior to radiation treatment. The accuracy of the radiation treatment of thoracic and upper abdominal structures is heavily affected by respiratory movement. Such movement typically blurs the CBCT reconstruction and ideally should be removed. Hence motion-compensated CBCT has recently been researched for correcting image artefacts due to breathing motion. This paper presents a new dual-modality approach where CBCT is aided by using electrical impedance tomography (EIT) for motion compensation. EIT can generate images of contrasts in electrical properties. The main advantage of using EIT is its high temporal resolution. In this paper motion information is extracted from EIT images and incorporated directly in the CBCT reconstruction. In this study synthetic moving data are generated using simulated and experimental phantoms. The paper demonstrates that image blur, created as a result of motion, can be reduced through motion compensation with EIT

  19. Influence of iterative image reconstruction on CT-based calcium score measurements

    NARCIS (Netherlands)

    van Osch, Jochen A. C.; Mouden, Mohamed; van Dalen, Jorn A.; Timmer, Jorik R.; Reiffers, Stoffer; Knollema, Siert; Greuter, Marcel J. W.; Ottervanger, Jan Paul; Jager, Piet L.

    Iterative reconstruction techniques for coronary CT angiography have been introduced as an alternative for traditional filter back projection (FBP) to reduce image noise, allowing improved image quality and a potential for dose reduction. However, the impact of iterative reconstruction on the

  20. Investigation of cone-beam CT image quality trade-off for image-guided radiation therapy

    Science.gov (United States)

    Bian, Junguo; Sharp, Gregory C.; Park, Yang-Kyun; Ouyang, Jinsong; Bortfeld, Thomas; El Fakhri, Georges

    2016-05-01

    It is well-known that projections acquired over an angular range slightly over 180° (so-called short scan) are sufficient for fan-beam reconstruction. However, due to practical imaging conditions (projection data and reconstruction image discretization, physical factors, and data noise), the short-scan reconstructions may have different appearances and properties from the full-scan (scans over 360°) reconstructions. Nevertheless, short-scan configurations have been used in applications such as cone-beam CT (CBCT) for head-neck-cancer image-guided radiation therapy (IGRT) that only requires a small field of view due to the potential reduced imaging time and dose. In this work, we studied the image quality trade-off for full, short, and full/short scan configurations with both conventional filtered-backprojection (FBP) reconstruction and iterative reconstruction algorithms based on total-variation (TV) minimization for head-neck-cancer IGRT. Anthropomorphic and Catphan phantoms were scanned at different exposure levels with a clinical scanner used in IGRT. Both visualization- and numerical-metric-based evaluation studies were performed. The results indicate that the optimal exposure level and number of views are in the middle range for both FBP and TV-based iterative algorithms and the optimization is object-dependent and task-dependent. The optimal view numbers decrease with the total exposure levels for both FBP and TV-based algorithms. The results also indicate there are slight differences between FBP and TV-based iterative algorithms for the image quality trade-off: FBP seems to be more in favor of larger number of views while the TV-based algorithm is more robust to different data conditions (number of views and exposure levels) than the FBP algorithm. The studies can provide a general guideline for image-quality optimization for CBCT used in IGRT and other applications.

  1. High spatial resolution CT image reconstruction using parallel computing

    International Nuclear Information System (INIS)

    Yin Yin; Liu Li; Sun Gongxing

    2003-01-01

    Using the PC cluster system with 16 dual CPU nodes, we accelerate the FBP and OR-OSEM reconstruction of high spatial resolution image (2048 x 2048). Based on the number of projections, we rewrite the reconstruction algorithms into parallel format and dispatch the tasks to each CPU. By parallel computing, the speedup factor is roughly equal to the number of CPUs, which can be up to about 25 times when 25 CPUs used. This technique is very suitable for real-time high spatial resolution CT image reconstruction. (authors)

  2. 4D cone beam CT via spatiotemporal tensor framelet

    International Nuclear Information System (INIS)

    Gao, Hao; Li, Ruijiang; Xing, Lei; Lin, Yuting

    2012-01-01

    Purpose: On-board 4D cone beam CT (4DCBCT) offers respiratory phase-resolved volumetric imaging, and improves the accuracy of target localization in image guided radiation therapy. However, the clinical utility of this technique has been greatly impeded by its degraded image quality, prolonged imaging time, and increased imaging dose. The purpose of this letter is to develop a novel iterative 4DCBCT reconstruction method for improved image quality, increased imaging speed, and reduced imaging dose. Methods: The essence of this work is to introduce the spatiotemporal tensor framelet (STF), a high-dimensional tensor generalization of the 1D framelet for 4DCBCT, to effectively take into account of highly correlated and redundant features of the patient anatomy during respiration, in a multilevel fashion with multibasis sparsifying transform. The STF-based algorithm is implemented on a GPU platform for improved computational efficiency. To evaluate the method, 4DCBCT full-fan scans were acquired within 30 s, with a gantry rotation of 200°; STF is also compared with a state-of-art reconstruction method via spatiotemporal total variation regularization. Results: Both the simulation and experimental results demonstrate that STF-based reconstruction achieved superior image quality. The reconstruction of 20 respiratory phases took less than 10 min on an NVIDIA Tesla C2070 GPU card. The STF codes are available at https://sites.google.com/site/spatiotemporaltensorframelet . Conclusions: By effectively utilizing the spatiotemporal coherence of the patient anatomy among different respiratory phases in a multilevel fashion with multibasis sparsifying transform, the proposed STF method potentially enables fast and low-dose 4DCBCT with improved image quality.

  3. 4D cone beam CT via spatiotemporal tensor framelet

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Hao, E-mail: hao.gao@emory.edu [Departments of Mathematics and Computer Science, and Radiology and Imaging Sciences, Emory University, Atlanta, Georgia 30322 (United States); Li, Ruijiang; Xing, Lei [Department of Radiation Oncology, Stanford University, Stanford, California 94305 (United States); Lin, Yuting [Department of Radiological Sciences, University of California, Irvine, California 92697 (United States)

    2012-11-15

    Purpose: On-board 4D cone beam CT (4DCBCT) offers respiratory phase-resolved volumetric imaging, and improves the accuracy of target localization in image guided radiation therapy. However, the clinical utility of this technique has been greatly impeded by its degraded image quality, prolonged imaging time, and increased imaging dose. The purpose of this letter is to develop a novel iterative 4DCBCT reconstruction method for improved image quality, increased imaging speed, and reduced imaging dose. Methods: The essence of this work is to introduce the spatiotemporal tensor framelet (STF), a high-dimensional tensor generalization of the 1D framelet for 4DCBCT, to effectively take into account of highly correlated and redundant features of the patient anatomy during respiration, in a multilevel fashion with multibasis sparsifying transform. The STF-based algorithm is implemented on a GPU platform for improved computational efficiency. To evaluate the method, 4DCBCT full-fan scans were acquired within 30 s, with a gantry rotation of 200°; STF is also compared with a state-of-art reconstruction method via spatiotemporal total variation regularization. Results: Both the simulation and experimental results demonstrate that STF-based reconstruction achieved superior image quality. The reconstruction of 20 respiratory phases took less than 10 min on an NVIDIA Tesla C2070 GPU card. The STF codes are available at https://sites.google.com/site/spatiotemporaltensorframelet . Conclusions: By effectively utilizing the spatiotemporal coherence of the patient anatomy among different respiratory phases in a multilevel fashion with multibasis sparsifying transform, the proposed STF method potentially enables fast and low-dose 4DCBCT with improved image quality.

  4. Analysis of bite marks in foodstuffs by computer tomography (cone beam CT)--3D reconstruction.

    Science.gov (United States)

    Marques, Jeidson; Musse, Jamilly; Caetano, Catarina; Corte-Real, Francisco; Corte-Real, Ana Teresa

    2013-12-01

    The use of three-dimensional (3D) analysis of forensic evidence is highlighted in comparison with traditional methods. This three-dimensional analysis is based on the registration of the surface from a bitten object. The authors propose to use Cone Beam Computed Tomography (CBCT), which is used in dental practice, in order to study the surface and interior of bitten objects and dental casts of suspects. In this study, CBCT is applied to the analysis of bite marks in foodstuffs, which may be found in a forensic case scenario. 6 different types of foodstuffs were used: chocolate, cheese, apple, chewing gum, pizza and tart (flaky pastry and custard). The food was bitten into and dental casts of the possible suspects were made. The dental casts and bitten objects were registered using an x-ray source and the CBCT equipment iCAT® (Pennsylvania, EUA). The software InVivo5® (Anatomage Inc, EUA) was used to visualize and analyze the tomographic slices and 3D reconstructions of the objects. For each material an estimate of its density was assessed by two methods: HU values and specific gravity. All the used materials were successfully reconstructed as good quality 3D images. The relative densities of the materials in study were compared. Amongst the foodstuffs, the chocolate had the highest density (median value 100.5 HU and 1,36 g/cm(3)), while the pizza showed to have the lowest (median value -775 HU and 0,39 g/cm(3)), on both scales. Through tomographic slices and three-dimensional reconstructions it was possible to perform the metric analysis of the bite marks in all the foodstuffs, except for the pizza. These measurements could also be obtained from the dental casts. The depth of the bite mark was also successfully determined in all the foodstuffs except for the pizza. Cone Beam Computed Tomography has the potential to become an important tool for forensic sciences, namely for the registration and analysis of bite marks in foodstuffs that may be found in a crime

  5. Evaluation of aortocoronary bypass graft patency by reconstructed CT image

    International Nuclear Information System (INIS)

    Kawakita, Seizaburo; Koide, Takashi; Saito, Yoshio; Yamamoto, Tadao; Iwasaki, Tadaaki

    1982-01-01

    Ten patients were examined in the period of three months from January to March 1981. The patients were operated from 1 month to 7 years before CT. A bypass to the left anterior descending artery (LAD) was grafted in 10 cases, 2 to the right coronary artery (RCA), 4 to an obtuse marginal artery (OM), and 1 to a diagonal artery. Image reconstruction was performed in 10 cases by using an image analytical computer Evaluskop. Appropriate planes for reconstruction were selected by trial and error methods upon observation of CT images. When gained picture of a graft course coincided with surgical records or angiography, the work of building images was concluded. On cross section, grafts to LAD were visualized in all 10 cases: 9 in the entire course and 1 in a proximal part of the graft. Two to RCA, 4 to OM and 1 to a diagonal were also successfully visualized. Reconstruction of graft images succeeded in 9 grafts of 6 cases. The course of a graft could be pursued from the proximal to the distal end adjacent to the cardiac chamber. The picture of a bypass to LAD was visualized in 6 of 10 grafts. Two bypass to RCA could be depicted, and 1 to OM was also found. However 3 to OM and 1 to a diagonal failed to be visualized throughout their courses in reconstructed images. I think that the causes of faillure mainly depended upon the course of the graft. When a graft was running arc-like surrounding the heart chamber, it was very difficult to depict its entire length in reconstructed images, though the graft could be detected in cross sections. These preliminary studies indicated that reconstruction of CT images had some benefits for the pursuit of graft courses. (J.P.N.)

  6. Effect of hybrid iterative reconstruction technique on quantitative and qualitative image analysis at 256-slice prospective gating cardiac CT

    International Nuclear Information System (INIS)

    Utsunomiya, Daisuke; Weigold, W. Guy; Weissman, Gaby; Taylor, Allen J.

    2012-01-01

    To evaluate the effect of hybrid iterative reconstruction on qualitative and quantitative parameters at 256-slice cardiac CT. Prospective cardiac CT images from 20 patients were analysed. Paired image sets were created using 3 reconstructions, i.e. filtered back projection (FBP) and moderate- and high-level iterative reconstructions. Quantitative parameters including CT-attenuation, noise, and contrast-to-noise ratio (CNR) were determined in both proximal- and distal coronary segments. Image quality was graded on a 4-point scale. Coronary CT attenuation values were similar for FBP, moderate- and high-level iterative reconstruction at 293 ± 74-, 290 ± 75-, and 283 ± 78 Hounsfield units (HU), respectively. CNR was significantly higher with moderate- and high-level iterative reconstructions (10.9 ± 3.5 and 18.4 ± 6.2, respectively) than FBP (8.2 ± 2.5) as was the visual grading of proximal vessels. Visualisation of distal vessels was better with high-level iterative reconstruction than FBP. The mean number of assessable segments among 289 segments was 245, 260, and 267 for FBP, moderate- and high-level iterative reconstruction, respectively; the difference between FBP and high-level iterative reconstruction was significant. Interobserver agreement was significantly higher for moderate- and high-level iterative reconstruction than FBP. Cardiac CT using hybrid iterative reconstruction yields higher CNR and better image quality than FBP. circle Cardiac CT helps clinicians to assess patients with coronary artery disease circle Hybrid iterative reconstruction provides improved cardiac CT image quality circle Hybrid iterative reconstruction improves the number of assessable coronary segments circle Hybrid iterative reconstruction improves interobserver agreement on cardiac CT. (orig.)

  7. Study on broad beam heavy ion CT

    International Nuclear Information System (INIS)

    Ohno, Yumiko; Kohno, Toshiyuki; Sasaki, Hitomi; Nanbu, S.; Kanai, Tatsuaki

    2003-01-01

    To achieve the heavy ion radiotherapy more precisely, it is important to know the distribution of the electron density in a human body, which is highly related to the range of charged particles. From a heavy ion CT image, we can directly obtain the 2-D distribution of the electron density in a sample. For this purpose, we have developed a broad beam heavy ion CT system. The electron density was obtained using some kinds of solutions targets. Also the dependence of the spatial resolution on the target size and the kinds of beams was estimated in this work using cylinders targets of 40, 60 and 80 mm in diameter, each of them has a hole of 10 mm in diameter at the center of it. (author)

  8. SYRMEP Tomo Project: a graphical user interface for customizing CT reconstruction workflows.

    Science.gov (United States)

    Brun, Francesco; Massimi, Lorenzo; Fratini, Michela; Dreossi, Diego; Billé, Fulvio; Accardo, Agostino; Pugliese, Roberto; Cedola, Alessia

    2017-01-01

    When considering the acquisition of experimental synchrotron radiation (SR) X-ray CT data, the reconstruction workflow cannot be limited to the essential computational steps of flat fielding and filtered back projection (FBP). More refined image processing is often required, usually to compensate artifacts and enhance the quality of the reconstructed images. In principle, it would be desirable to optimize the reconstruction workflow at the facility during the experiment (beamtime). However, several practical factors affect the image reconstruction part of the experiment and users are likely to conclude the beamtime with sub-optimal reconstructed images. Through an example of application, this article presents SYRMEP Tomo Project (STP), an open-source software tool conceived to let users design custom CT reconstruction workflows. STP has been designed for post-beamtime (off-line use) and for a new reconstruction of past archived data at user's home institution where simple computing resources are available. Releases of the software can be downloaded at the Elettra Scientific Computing group GitHub repository https://github.com/ElettraSciComp/STP-Gui.

  9. CT stereotactic reconstruction of oral cavity interstitial plastic tube implants

    International Nuclear Information System (INIS)

    Crispin, V.; Carrasco, P.; Guardino, C.; Lopez, J.; Chust, M.; Arribas, L.; Mengual, J.; Miragall, E.G.; Hernandez, A.; Carrascosa, M.; Cardenal, R.; Guinot, J.; Casana, M.; Prats, C.

    1996-01-01

    The continuous using of CT images in external RT have made us think of its applications for plastic tube interstitial implants in the oral cavity in order to calculate the dose delivered by an interstitial implant at any point of the image and its relationship with local control and complications. Moreover, the outcoming result of the whole treatment depends on whether the irradiated volume up to a prescribed dose includes the CTV or not. None of these objectives may be achieved through the classical film reconstruction. Although film reconstruction appeared as the only accurate method for these purposes in the early eighties, it does not allow us to calculate doses at critical points or volumes. Therefore possible complications over critical tissues surrounding the radioactive implant cannot be taken into account in a precise way. The use of a stereotactic coordinate system could make CT reconstruction as precise as film reconstruction. As our stereotactic frame can be placed over the patient in 'direct' or 'inverse' positions it is really interesting in the applications we are talking about. We also have used a non invasive standard plexiglass helmet commonly used in stereotactic fractionated irradiations in teletherapy. It fits perfectly the patient's head and avoids any movement of the patient during the CT exam. We do parallel slices, approximately perpendicular to the iridium wires (following the Paris System), covering the whole implant helping ourselves with both bone and implant references. The dose-volume histograms and DNR (dose nonuniformity ratio) index defined by Saw et Al are used for intercomparison between the ortogonal and the stereotactic reconstructions. The existence of a minimum in the DNR curve indicates that there is a reference dose rate for this implant which provides an optimal dose distribution. If we calculate which is the minimum of each method, we find they are very close. So, as both methods give very similar results, we can conclude

  10. MO-DE-207A-09: Low-Dose CT Image Reconstruction Via Learning From Different Patient Normal-Dose Images

    Energy Technology Data Exchange (ETDEWEB)

    Han, H; Xing, L [Stanford University, Palo Alto, CA (United States); Liang, Z [Stony Brook University, Stony Brook, NY (United States)

    2016-06-15

    Purpose: To investigate a novel low-dose CT (LdCT) image reconstruction strategy for lung CT imaging in radiation therapy. Methods: The proposed approach consists of four steps: (1) use the traditional filtered back-projection (FBP) method to reconstruct the LdCT image; (2) calculate structure similarity (SSIM) index between the FBP-reconstructed LdCT image and a set of normal-dose CT (NdCT) images, and select the NdCT image with the highest SSIM as the learning source; (3) segment the NdCT source image into lung and outside tissue regions via simple thresholding, and adopt multiple linear regression to learn high-order Markov random field (MRF) pattern for each tissue region in the NdCT source image; (4) segment the FBP-reconstructed LdCT image into lung and outside regions as well, and apply the learnt MRF prior in each tissue region for statistical iterative reconstruction of the LdCT image following the penalized weighted least squares (PWLS) framework. Quantitative evaluation of the reconstructed images was based on the signal-to-noise ratio (SNR), local binary pattern (LBP) and histogram of oriented gradients (HOG) metrics. Results: It was observed that lung and outside tissue regions have different MRF patterns predicted from the NdCT. Visual inspection showed that our method obviously outperformed the traditional FBP method. Comparing with the region-smoothing PWLS method, our method has, in average, 13% increase in SNR, 15% decrease in LBP difference, and 12% decrease in HOG difference from reference standard for all regions of interest, which indicated the superior performance of the proposed method in terms of image resolution and texture preservation. Conclusion: We proposed a novel LdCT image reconstruction method by learning similar image characteristics from a set of NdCT images, and the to-be-learnt NdCT image does not need to be scans from the same subject. This approach is particularly important for enhancing image quality in radiation therapy.

  11. MO-DE-207A-09: Low-Dose CT Image Reconstruction Via Learning From Different Patient Normal-Dose Images

    International Nuclear Information System (INIS)

    Han, H; Xing, L; Liang, Z

    2016-01-01

    Purpose: To investigate a novel low-dose CT (LdCT) image reconstruction strategy for lung CT imaging in radiation therapy. Methods: The proposed approach consists of four steps: (1) use the traditional filtered back-projection (FBP) method to reconstruct the LdCT image; (2) calculate structure similarity (SSIM) index between the FBP-reconstructed LdCT image and a set of normal-dose CT (NdCT) images, and select the NdCT image with the highest SSIM as the learning source; (3) segment the NdCT source image into lung and outside tissue regions via simple thresholding, and adopt multiple linear regression to learn high-order Markov random field (MRF) pattern for each tissue region in the NdCT source image; (4) segment the FBP-reconstructed LdCT image into lung and outside regions as well, and apply the learnt MRF prior in each tissue region for statistical iterative reconstruction of the LdCT image following the penalized weighted least squares (PWLS) framework. Quantitative evaluation of the reconstructed images was based on the signal-to-noise ratio (SNR), local binary pattern (LBP) and histogram of oriented gradients (HOG) metrics. Results: It was observed that lung and outside tissue regions have different MRF patterns predicted from the NdCT. Visual inspection showed that our method obviously outperformed the traditional FBP method. Comparing with the region-smoothing PWLS method, our method has, in average, 13% increase in SNR, 15% decrease in LBP difference, and 12% decrease in HOG difference from reference standard for all regions of interest, which indicated the superior performance of the proposed method in terms of image resolution and texture preservation. Conclusion: We proposed a novel LdCT image reconstruction method by learning similar image characteristics from a set of NdCT images, and the to-be-learnt NdCT image does not need to be scans from the same subject. This approach is particularly important for enhancing image quality in radiation therapy.

  12. Reduction of ring artefacts in high resolution micro-CT reconstructions

    International Nuclear Information System (INIS)

    Sijbers, Jan; Postnov, Andrei

    2004-01-01

    High resolution micro-CT images are often corrupted by ring artefacts, prohibiting quantitative analysis and hampering post processing. Removing or at least significantly reducing such artefacts is indispensable. However, since micro-CT systems are pushed to the extremes in the quest for the ultimate spatial resolution, ring artefacts can hardly be avoided. Moreover, as opposed to clinical CT systems, conventional correction schemes such as flat-field correction do not lead to satisfactory results. Therefore, in this note a simple but efficient and fast post processing method is proposed that effectively reduces ring artefacts in reconstructed μ-CT images. (note)

  13. Impact of PET/CT image reconstruction methods and liver uptake normalization strategies on quantitative image analysis

    Energy Technology Data Exchange (ETDEWEB)

    Kuhnert, Georg; Sterzer, Sergej; Kahraman, Deniz; Dietlein, Markus; Drzezga, Alexander; Kobe, Carsten [University Hospital of Cologne, Department of Nuclear Medicine, Cologne (Germany); Boellaard, Ronald [VU University Medical Centre, Department of Radiology and Nuclear Medicine, Amsterdam (Netherlands); Scheffler, Matthias; Wolf, Juergen [University Hospital of Cologne, Lung Cancer Group Cologne, Department I of Internal Medicine, Center for Integrated Oncology Cologne Bonn, Cologne (Germany)

    2016-02-15

    In oncological imaging using PET/CT, the standardized uptake value has become the most common parameter used to measure tracer accumulation. The aim of this analysis was to evaluate ultra high definition (UHD) and ordered subset expectation maximization (OSEM) PET/CT reconstructions for their potential impact on quantification. We analyzed 40 PET/CT scans of lung cancer patients who had undergone PET/CT. Standardized uptake values corrected for body weight (SUV) and lean body mass (SUL) were determined in the single hottest lesion in the lung and normalized to the liver for UHD and OSEM reconstruction. Quantitative uptake values and their normalized ratios for the two reconstruction settings were compared using the Wilcoxon test. The distribution of quantitative uptake values and their ratios in relation to the reconstruction method used were demonstrated in the form of frequency distribution curves, box-plots and scatter plots. The agreement between OSEM and UHD reconstructions was assessed through Bland-Altman analysis. A significant difference was observed after OSEM and UHD reconstruction for SUV and SUL data tested (p < 0.0005 in all cases). The mean values of the ratios after OSEM and UHD reconstruction showed equally significant differences (p < 0.0005 in all cases). Bland-Altman analysis showed that the SUV and SUL and their normalized values were, on average, up to 60 % higher after UHD reconstruction as compared to OSEM reconstruction. OSEM and HD reconstruction brought a significant difference for SUV and SUL, which remained constantly high after normalization to the liver, indicating that standardization of reconstruction and the use of comparable SUV measurements are crucial when using PET/CT. (orig.)

  14. Upper airway alterations/abnormalities in a case series of obstructive sleep apnea patients identified with cone-beam CT

    International Nuclear Information System (INIS)

    Shigeta, Y.; Shintaku, W.H.; Clark, G.T.; Enciso, R.; Ogawa, T.

    2007-01-01

    There are many factors that influence the configuration of the upper airway and may contribute to the development of obstructive sleep apnea (OSA). This paper presents a series of 12 consecutive OSA cases where various upper airway alteration/abnormalities were identified using 3D anatomic reconstructions generated from cone-beam CT (CBCT) images. Some cases exhibited more than one type of abnormality and below we describe each of the six types identified with CBCT in this case series. (orig.)

  15. Upper airway alterations/abnormalities in a case series of obstructive sleep apnea patients identified with cone-beam CT

    Energy Technology Data Exchange (ETDEWEB)

    Shigeta, Y; Shintaku, W H; Clark, G T [Orofacial Pain/Oral Medicine Center, Div. of Diagnostic Sciences, School of Dentistry, Univ. of Southern California, Los Angeles, CA (United States); Enciso, R [Div. of Craniofacial Sciences and Therapeutics, School of Dentistry, Univ. of Southern California, Los Angeles, CA (United States); Ogawa, T [Dept. of Fixed Prosthodontic Dentistry, Tsurumi Univ., School of Dental Medicine, Tsurumi (Japan)

    2007-06-15

    There are many factors that influence the configuration of the upper airway and may contribute to the development of obstructive sleep apnea (OSA). This paper presents a series of 12 consecutive OSA cases where various upper airway alteration/abnormalities were identified using 3D anatomic reconstructions generated from cone-beam CT (CBCT) images. Some cases exhibited more than one type of abnormality and below we describe each of the six types identified with CBCT in this case series. (orig.)

  16. Fast parallel algorithm for CT image reconstruction.

    Science.gov (United States)

    Flores, Liubov A; Vidal, Vicent; Mayo, Patricia; Rodenas, Francisco; Verdú, Gumersindo

    2012-01-01

    In X-ray computed tomography (CT) the X rays are used to obtain the projection data needed to generate an image of the inside of an object. The image can be generated with different techniques. Iterative methods are more suitable for the reconstruction of images with high contrast and precision in noisy conditions and from a small number of projections. Their use may be important in portable scanners for their functionality in emergency situations. However, in practice, these methods are not widely used due to the high computational cost of their implementation. In this work we analyze iterative parallel image reconstruction with the Portable Extensive Toolkit for Scientific computation (PETSc).

  17. Postoperative assessment of surgical results using three dimensional surface reconstruction CT (3D-CT) in a craniofacial anomaly

    International Nuclear Information System (INIS)

    Nishimura, Jiro; Sato, Kaoru; Nishimoto, Hiroshi; Tsukiyama, Takashi; Fujioka, Mutsuhisa; Akagawa, Tetsuya.

    1988-01-01

    In 1983, Michael W. Vannier and Jeffrey L. Marsh developed a computer method that reconstructs three dimensional (3D) born and soft tissue surfaces, given a high resolution CT scan-series of the facial skeleton. This method has been applied to craniofacial anomalies, basal encephaloceles, and musculoskeletal anomalies. In this study, a postoperative assessment of the craniofacial surgical results has been accomplished using this 3D-CT in 2 children with craniofacial dysmorphism. The authors discuss the advantages of this 3D-CT imaging method in the postoperative assessments of craniofacial anomalies. Results are detailed in the following listing : 1) a postoperative 3D-CT reveals the anatomical details corrected by the craniofacial surgery more precisely and stereographically than conventional radiological methods ; 2) secondary changes of the cranium after the surgery, such as bony formation in the area of the osteotomy and postoperative asymmetric deformities, are detected early by the 3D-CT imaging technique, and, 3) 3D-CT mid-sagittal and top axial views of the intracranial skull base are most useful in postoperative assessments of the surgical results. Basesd on our experience, we expect that three dimensional surface reconstructions from CT scans will become to be used widely in the postoperative assessments of the surgical results of craniofacial anomalies. (author)

  18. Effects of Different Reconstruction Parameters on CT Volumetric Measurement 
of Pulmonary Nodules

    Directory of Open Access Journals (Sweden)

    Rongrong YANG

    2012-02-01

    Full Text Available Background and objective It has been proven that volumetric measurements could detect subtle changes in small pulmonary nodules in serial CT scans, and thus may play an important role in the follow-up of indeterminate pulmonary nodules and in differentiating malignant nodules from benign nodules. The current study aims to evaluate the effects of different reconstruction parameters on the volumetric measurements of pulmonary nodules in chest CT scans. Methods Thirty subjects who underwent chest CT scan because of indeterminate pulmonary nodules in General Hospital of Tianjin Medical University from December 2009 to August 2011 were retrospectively analyzed. A total of 52 pulmonary nodules were included, and all CT data were reconstructed using three reconstruction algorithms and three slice thicknesses. The volumetric measurements of the nodules were performed using the advanced lung analysis (ALA software. The effects of the reconstruction algorithms, slice thicknesses, and nodule diameters on the volumetric measurements were assessed using the multivariate analysis of variance for repeated measures, the correlation analysis, and the Bland-Altman method. Results The reconstruction algorithms (F=13.6, P<0.001 and slice thicknesses (F=4.4, P=0.02 had significant effects on the measured volume of pulmonary nodules. In addition, the coefficients of variation of nine measurements were inversely related with nodule diameter (r=-0.814, P<0.001. The volume measured at the 2.5 mm slice thickness had poor agreement with the volumes measured at 1.25 mm and 0.625 mm, respectively. Moreover, the best agreement was achieved between the slice thicknesses of 1.25 mm and 0.625 mm using the bone algorithm. Conclusion Reconstruction algorithms and slice thicknesses have significant impacts on the volumetric measurements of lung nodules, especially for the small nodules. Therefore, the reconstruction setting in serial CT scans should be consistent in the follow

  19. Adaptive statistical iterative reconstruction reduces patient radiation dose in neuroradiology CT studies

    Energy Technology Data Exchange (ETDEWEB)

    Komlosi, Peter; Zhang, Yanrong; Leiva-Salinas, Carlos; Ornan, David; Grady, Deborah [University of Virginia, Department of Radiology and Medical Imaging, Division of Neuroradiology, PO Box 800170, Charlottesville, VA (United States); Patrie, James T.; Xin, Wenjun [University of Virginia, Department of Public Health Sciences, Charlottesville, VA (United States); Wintermark, Max [University of Virginia, Department of Radiology and Medical Imaging, Division of Neuroradiology, PO Box 800170, Charlottesville, VA (United States); Centre Hospitalier Universitaire Vaudois, Department of Radiology, Lausanne (Switzerland)

    2014-03-15

    Adaptive statistical iterative reconstruction (ASIR) can decrease image noise, thereby generating CT images of comparable diagnostic quality with less radiation. The purpose of this study is to quantify the effect of systematic use of ASIR versus filtered back projection (FBP) for neuroradiology CT protocols on patients' radiation dose and image quality. We evaluated the effect of ASIR on six types of neuroradiologic CT studies: adult and pediatric unenhanced head CT, adult cervical spine CT, adult cervical and intracranial CT angiography, adult soft tissue neck CT with contrast, and adult lumbar spine CT. For each type of CT study, two groups of 100 consecutive studies were retrospectively reviewed: 100 studies performed with FBP and 100 studies performed with ASIR/FBP blending factor of 40 %/60 % with appropriate noise indices. The weighted volume CT dose index (CTDI{sub vol}), dose-length product (DLP) and noise were recorded. Each study was also reviewed for image quality by two reviewers. Continuous and categorical variables were compared by t test and free permutation test, respectively. For adult unenhanced brain CT, CT cervical myelography, cervical and intracranial CT angiography and lumbar spine CT both CTDI{sub vol} and DLP were lowered by up to 10.9 % (p < 0.001), 17.9 % (p = 0.005), 20.9 % (p < 0.001), and 21.7 % (p = 0.001), respectively, by using ASIR compared with FBP alone. Image quality and noise were similar for both FBP and ASIR. We recommend routine use of iterative reconstruction for neuroradiology CT examinations because this approach affords a significant dose reduction while preserving image quality. (orig.)

  20. Adaptive statistical iterative reconstruction reduces patient radiation dose in neuroradiology CT studies

    International Nuclear Information System (INIS)

    Komlosi, Peter; Zhang, Yanrong; Leiva-Salinas, Carlos; Ornan, David; Grady, Deborah; Patrie, James T.; Xin, Wenjun; Wintermark, Max

    2014-01-01

    Adaptive statistical iterative reconstruction (ASIR) can decrease image noise, thereby generating CT images of comparable diagnostic quality with less radiation. The purpose of this study is to quantify the effect of systematic use of ASIR versus filtered back projection (FBP) for neuroradiology CT protocols on patients' radiation dose and image quality. We evaluated the effect of ASIR on six types of neuroradiologic CT studies: adult and pediatric unenhanced head CT, adult cervical spine CT, adult cervical and intracranial CT angiography, adult soft tissue neck CT with contrast, and adult lumbar spine CT. For each type of CT study, two groups of 100 consecutive studies were retrospectively reviewed: 100 studies performed with FBP and 100 studies performed with ASIR/FBP blending factor of 40 %/60 % with appropriate noise indices. The weighted volume CT dose index (CTDI vol ), dose-length product (DLP) and noise were recorded. Each study was also reviewed for image quality by two reviewers. Continuous and categorical variables were compared by t test and free permutation test, respectively. For adult unenhanced brain CT, CT cervical myelography, cervical and intracranial CT angiography and lumbar spine CT both CTDI vol and DLP were lowered by up to 10.9 % (p < 0.001), 17.9 % (p = 0.005), 20.9 % (p < 0.001), and 21.7 % (p = 0.001), respectively, by using ASIR compared with FBP alone. Image quality and noise were similar for both FBP and ASIR. We recommend routine use of iterative reconstruction for neuroradiology CT examinations because this approach affords a significant dose reduction while preserving image quality. (orig.)

  1. Flat panel detector-based cone beam computed tomography with a circle-plus-two-arcs data acquisition orbit: Preliminary phantom study

    International Nuclear Information System (INIS)

    Ning Ruola; Tang Xiangyang; Conover, David; Yu Rongfeng

    2003-01-01

    Cone beam computed tomography (CBCT) has been investigated in the past two decades due to its potential advantages over a fan beam CT. These advantages include (a) great improvement in data acquisition efficiency, spatial resolution, and spatial resolution uniformity, (b) substantially better utilization of x-ray photons generated by the x-ray tube compared to a fan beam CT, and (c) significant advancement in clinical three-dimensional (3D) CT applications. However, most studies of CBCT in the past are focused on cone beam data acquisition theories and reconstruction algorithms. The recent development of x-ray flat panel detectors (FPD) has made CBCT imaging feasible and practical. This paper reports a newly built flat panel detector-based CBCT prototype scanner and presents the results of the preliminary evaluation of the prototype through a phantom study. The prototype consisted of an x-ray tube, a flat panel detector, a GE 8800 CT gantry, a patient table and a computer system. The prototype was constructed by modifying a GE 8800 CT gantry such that both a single-circle cone beam acquisition orbit and a circle-plus-two-arcs orbit can be achieved. With a circle-plus-two-arcs orbit, a complete set of cone beam projection data can be obtained, consisting of a set of circle projections and a set of arc projections. Using the prototype scanner, the set of circle projections were acquired by rotating the x-ray tube and the FPD together on the gantry, and the set of arc projections were obtained by tilting the gantry while the x-ray tube and detector were at the 12 and 6 o'clock positions, respectively. A filtered backprojection exact cone beam reconstruction algorithm based on a circle-plus-two-arcs orbit was used for cone beam reconstruction from both the circle and arc projections. The system was first characterized in terms of the linearity and dynamic range of the detector. Then the uniformity, spatial resolution and low contrast resolution were assessed using

  2. Cone-Beam CT with Flat-Panel-Detector Digital Angiography System: Early Experience in Abdominal Interventional Procedures

    International Nuclear Information System (INIS)

    Hirota, Shozo; Nakao, Norio; Yamamoto, Satoshi; Kobayashi, Kaoru; Maeda, Hiroaki; Ishikura, Reiichi; Miura, Koui; Sakamoto, Kiyoshi; Ueda, Ken; Baba, Rika

    2006-01-01

    We developed a cone-beam computed tomography (CBCT) system equipped with a large flat-panel detector. Data obtained by 200 o rotation imaging are reconstructed by means of CBCT to generate three-dimensional images. We report the use of CBCT angiography using CBCT in 10 patients with 8 liver malignancies and 2 hypersplenisms during abdominal interventional procedures. CBCT was very useful for interventional radiologists to confirm a perfusion area of the artery catheter wedged on CT by injection of contrast media through the catheter tip, although the image quality was slightly degraded, scoring as 2.60 on average by streak artifacts. CBCT is space-saving because it does not require a CT system with a gantry, and it is also time-saving because it does not require the transfer of patients

  3. A comprehensive study on decreasing the kilovoltage cone-beam CT dose by reducing the projection number.

    Science.gov (United States)

    Lu, Bo; Lu, Haibin; Palta, Jatinder

    2010-05-12

    The objective of this study was to evaluate the effect of kilovoltage cone-beam computed tomography (CBCT) on registration accuracy and image qualities with a reduced number of planar projections used in volumetric imaging reconstruction. The ultimate goal is to evaluate the possibility of reducing the patient dose while maintaining registration accuracy under different projection-number schemes for various clinical sites. An Elekta Synergy Linear accelerator with an onboard CBCT system was used in this study. The quality of the Elekta XVI cone-beam three-dimensional volumetric images reconstructed with a decreasing number of projections was quantitatively evaluated by a Catphan phantom. Subsequently, we tested the registration accuracy of imaging data sets on three rigid anthropomorphic phantoms and three real patient sites under the reduced projection-number (as low as 1/6th) reconstruction of CBCT data with different rectilinear shifts and rota-tions. CBCT scan results of the Catphan phantom indicated the CBCT images got noisier when the number of projections was reduced, but their spatial resolution and uniformity were hardly affected. The maximum registration errors under the small amount transformation of the reference CT images were found to be within 0.7 mm translation and 0.3 masculine rotation. However, when the projection number was lower than one-fourth of the full set with a large amount of transformation of reference CT images, the registration could easily be trapped into local minima solutions for a nonrigid anatomy. We concluded, by using projection-number reduction strategy under conscientious care, imaging-guided localization procedure could achieve a lower patient dose without losing the registration accuracy for various clinical sites and situations. A faster scanning time is the main advantage compared to the mA decrease-based, dose-reduction method.

  4. Temporal resolution and motion artifacts in single-source and dual-source cardiac CT.

    Science.gov (United States)

    Schöndube, Harald; Allmendinger, Thomas; Stierstorfer, Karl; Bruder, Herbert; Flohr, Thomas

    2013-03-01

    The temporal resolution of a given image in cardiac computed tomography (CT) has so far mostly been determined from the amount of CT data employed for the reconstruction of that image. The purpose of this paper is to examine the applicability of such measures to the newly introduced modality of dual-source CT as well as to methods aiming to provide improved temporal resolution by means of an advanced image reconstruction algorithm. To provide a solid base for the examinations described in this paper, an extensive review of temporal resolution in conventional single-source CT is given first. Two different measures for assessing temporal resolution with respect to the amount of data involved are introduced, namely, either taking the full width at half maximum of the respective data weighting function (FWHM-TR) or the total width of the weighting function (total TR) as a base of the assessment. Image reconstruction using both a direct fan-beam filtered backprojection with Parker weighting as well as using a parallel-beam rebinning step are considered. The theory of assessing temporal resolution by means of the data involved is then extended to dual-source CT. Finally, three different advanced iterative reconstruction methods that all use the same input data are compared with respect to the resulting motion artifact level. For brevity and simplicity, the examinations are limited to two-dimensional data acquisition and reconstruction. However, all results and conclusions presented in this paper are also directly applicable to both circular and helical cone-beam CT. While the concept of total TR can directly be applied to dual-source CT, the definition of the FWHM of a weighting function needs to be slightly extended to be applicable to this modality. The three different advanced iterative reconstruction methods examined in this paper result in significantly different images with respect to their motion artifact level, despite exactly the same amount of data being used

  5. Temporal resolution and motion artifacts in single-source and dual-source cardiac CT

    International Nuclear Information System (INIS)

    Schöndube, Harald; Allmendinger, Thomas; Stierstorfer, Karl; Bruder, Herbert; Flohr, Thomas

    2013-01-01

    Purpose: The temporal resolution of a given image in cardiac computed tomography (CT) has so far mostly been determined from the amount of CT data employed for the reconstruction of that image. The purpose of this paper is to examine the applicability of such measures to the newly introduced modality of dual-source CT as well as to methods aiming to provide improved temporal resolution by means of an advanced image reconstruction algorithm. Methods: To provide a solid base for the examinations described in this paper, an extensive review of temporal resolution in conventional single-source CT is given first. Two different measures for assessing temporal resolution with respect to the amount of data involved are introduced, namely, either taking the full width at half maximum of the respective data weighting function (FWHM-TR) or the total width of the weighting function (total TR) as a base of the assessment. Image reconstruction using both a direct fan-beam filtered backprojection with Parker weighting as well as using a parallel-beam rebinning step are considered. The theory of assessing temporal resolution by means of the data involved is then extended to dual-source CT. Finally, three different advanced iterative reconstruction methods that all use the same input data are compared with respect to the resulting motion artifact level. For brevity and simplicity, the examinations are limited to two-dimensional data acquisition and reconstruction. However, all results and conclusions presented in this paper are also directly applicable to both circular and helical cone-beam CT. Results: While the concept of total TR can directly be applied to dual-source CT, the definition of the FWHM of a weighting function needs to be slightly extended to be applicable to this modality. The three different advanced iterative reconstruction methods examined in this paper result in significantly different images with respect to their motion artifact level, despite exactly the same

  6. Radiation dose reduction in soft tissue neck CT using adaptive statistical iterative reconstruction (ASIR)

    Energy Technology Data Exchange (ETDEWEB)

    Vachha, Behroze, E-mail: bvachha@partners.org [Neuroradiology Division, Massachusetts General Hospital, Harvard Medical School, 55 Fruit Street, Boston, MA 02114 (United States); Brodoefel, Harald; Wilcox, Carol; Hackney, David B.; Moonis, Gul [Department of Radiology, Beth Israel Deaconess Medical Center, Harvard Medical School, 330 Brookline Avenue, Boston, MA 02215 (United States)

    2013-12-01

    Purpose: To compare objective and subjective image quality in neck CT images acquired at different tube current–time products (275 mA s and 340 mA s) and reconstructed with filtered-back-projection (FBP) and adaptive statistical iterative reconstruction (ASIR). Materials and methods: HIPAA-compliant study with IRB approval and waiver of informed consent. 66 consecutive patients were randomly assigned to undergo contrast-enhanced neck CT at a standard tube-current–time-product (340 mA s; n = 33) or reduced tube-current–time-product (275 mA s, n = 33). Data sets were reconstructed with FBP and 2 levels (30%, 40%) of ASIR-FBP blending at 340 mA s and 275 mA s. Two neuroradiologists assessed subjective image quality in a blinded and randomized manner. Volume CT dose index (CTDIvol), dose-length-product (DLP), effective dose, and objective image noise were recorded. Signal-to-noise ratio (SNR) was computed as mean attenuation in a region of interest in the sternocleidomastoid muscle divided by image noise. Results: Compared with FBP, ASIR resulted in a reduction of image noise at both 340 mA s and 275 mA s. Reduction of tube current from 340 mA s to 275 mA s resulted in an increase in mean objective image noise (p = 0.02) and a decrease in SNR (p = 0.03) when images were reconstructed with FBP. However, when the 275 mA s images were reconstructed using ASIR, the mean objective image noise and SNR were similar to those of the standard 340 mA s CT images reconstructed with FBP (p > 0.05). Subjective image noise was ranked by both raters as either average or less-than-average irrespective of the tube current and iterative reconstruction technique. Conclusion: Adapting ASIR into neck CT protocols reduced effective dose by 17% without compromising image quality.

  7. Radiation dose reduction in soft tissue neck CT using adaptive statistical iterative reconstruction (ASIR)

    International Nuclear Information System (INIS)

    Vachha, Behroze; Brodoefel, Harald; Wilcox, Carol; Hackney, David B.; Moonis, Gul

    2013-01-01

    Purpose: To compare objective and subjective image quality in neck CT images acquired at different tube current–time products (275 mA s and 340 mA s) and reconstructed with filtered-back-projection (FBP) and adaptive statistical iterative reconstruction (ASIR). Materials and methods: HIPAA-compliant study with IRB approval and waiver of informed consent. 66 consecutive patients were randomly assigned to undergo contrast-enhanced neck CT at a standard tube-current–time-product (340 mA s; n = 33) or reduced tube-current–time-product (275 mA s, n = 33). Data sets were reconstructed with FBP and 2 levels (30%, 40%) of ASIR-FBP blending at 340 mA s and 275 mA s. Two neuroradiologists assessed subjective image quality in a blinded and randomized manner. Volume CT dose index (CTDIvol), dose-length-product (DLP), effective dose, and objective image noise were recorded. Signal-to-noise ratio (SNR) was computed as mean attenuation in a region of interest in the sternocleidomastoid muscle divided by image noise. Results: Compared with FBP, ASIR resulted in a reduction of image noise at both 340 mA s and 275 mA s. Reduction of tube current from 340 mA s to 275 mA s resulted in an increase in mean objective image noise (p = 0.02) and a decrease in SNR (p = 0.03) when images were reconstructed with FBP. However, when the 275 mA s images were reconstructed using ASIR, the mean objective image noise and SNR were similar to those of the standard 340 mA s CT images reconstructed with FBP (p > 0.05). Subjective image noise was ranked by both raters as either average or less-than-average irrespective of the tube current and iterative reconstruction technique. Conclusion: Adapting ASIR into neck CT protocols reduced effective dose by 17% without compromising image quality

  8. Radiation dose reduction in soft tissue neck CT using adaptive statistical iterative reconstruction (ASIR).

    Science.gov (United States)

    Vachha, Behroze; Brodoefel, Harald; Wilcox, Carol; Hackney, David B; Moonis, Gul

    2013-12-01

    To compare objective and subjective image quality in neck CT images acquired at different tube current-time products (275 mAs and 340 mAs) and reconstructed with filtered-back-projection (FBP) and adaptive statistical iterative reconstruction (ASIR). HIPAA-compliant study with IRB approval and waiver of informed consent. 66 consecutive patients were randomly assigned to undergo contrast-enhanced neck CT at a standard tube-current-time-product (340 mAs; n = 33) or reduced tube-current-time-product (275 mAs, n = 33). Data sets were reconstructed with FBP and 2 levels (30%, 40%) of ASIR-FBP blending at 340 mAs and 275 mAs. Two neuroradiologists assessed subjective image quality in a blinded and randomized manner. Volume CT dose index (CTDIvol), dose-length-product (DLP), effective dose, and objective image noise were recorded. Signal-to-noise ratio (SNR) was computed as mean attenuation in a region of interest in the sternocleidomastoid muscle divided by image noise. Compared with FBP, ASIR resulted in a reduction of image noise at both 340 mAs and 275 mAs. Reduction of tube current from 340 mAs to 275 mAs resulted in an increase in mean objective image noise (p=0.02) and a decrease in SNR (p = 0.03) when images were reconstructed with FBP. However, when the 275 mAs images were reconstructed using ASIR, the mean objective image noise and SNR were similar to those of the standard 340 mAs CT images reconstructed with FBP (p>0.05). Subjective image noise was ranked by both raters as either average or less-than-average irrespective of the tube current and iterative reconstruction technique. Adapting ASIR into neck CT protocols reduced effective dose by 17% without compromising image quality. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

  9. Iterative reconstruction with attenuation compensation from cone-beam projections acquired via nonplanar orbits

    International Nuclear Information System (INIS)

    Zeng, G.L.; Weng, Y.; Gullberg, G.T.

    1997-01-01

    Single photon emission computed tomography (SPECT) imaging with cone-beam collimators provides improved sensitivity and spatial resolution for imaging small objects with large field-of-view detectors. It is known that Tuy's cone-beam data sufficiency condition must be met to obtain artifact-free reconstructions. Even though Tuy's condition was derived for an attenuation-free situation, the authors hypothesize that an artifact-free reconstruction can be obtained even if the cone-beam data are attenuated, provided the imaging orbit satisfies Tuy's condition and the exact attenuation map is known. In the authors' studies, emission data are acquired using nonplanar circle-and-line orbits to acquire cone-beam data for tomographic reconstructions. An extended iterative ML-EM (maximum likelihood-expectation maximization) reconstruction algorithm is derived and used to reconstruct projection data with either a pre-acquired or assumed attenuation map. Quantitative accuracy of the attenuation corrected emission reconstruction is significantly improved

  10. Performances of new reconstruction algorithms for CT-TDLAS (computer tomography-tunable diode laser absorption spectroscopy)

    International Nuclear Information System (INIS)

    Jeon, Min-Gyu; Deguchi, Yoshihiro; Kamimoto, Takahiro; Doh, Deog-Hee; Cho, Gyeong-Rae

    2017-01-01

    Highlights: • The measured data were successfully used for generating absorption spectra. • Four different reconstruction algorithms, ART, MART, SART and SMART were evaluated. • The calculation speed of convergence by the SMART algorithm was the fastest. • SMART was the most reliable algorithm for reconstructing the multiple signals. - Abstract: Recent advent of the tunable lasers made to measure simultaneous temperature and concentration fields of the gases. CT-TDLAS (computed tomography-tunable diode laser absorption spectroscopy) is one the leading techniques for the measurements of temperature and concentration fields of the gases. In CT-TDLAS, the accuracies of the measurement results are strongly dependent upon the reconstruction algorithms. In this study, four different reconstruction algorithms have been tested numerically using experimental data sets measured by thermocouples for combustion fields. Three reconstruction algorithms, MART (multiplicative algebraic reconstruction technique) algorithm, SART (simultaneous algebraic reconstruction technique) algorithm and SMART (simultaneous multiplicative algebraic reconstruction technique) algorithm, are newly proposed for CT-TDLAS in this study. The calculation results obtained by the three algorithms have been compared with previous algorithm, ART (algebraic reconstruction technique) algorithm. Phantom data sets have been generated by the use of thermocouples data obtained in an actual experiment. The data of the Harvard HITRAN table in which the thermo-dynamical properties and the light spectrum of the H_2O are listed were used for the numerical test. The reconstructed temperature and concentration fields were compared with the original HITRAN data, through which the constructed methods are validated. The performances of the four reconstruction algorithms were demonstrated. This method is expected to enhance the practicality of CT-TDLAS.

  11. The generalized back projection theorem for cone beam reconstruction

    International Nuclear Information System (INIS)

    Peyrin, F.C.

    1985-01-01

    The use of cone beam scanners raises the problem of three dimensional reconstruction from divergent projections. After a survey on bidimensional analytical reconstruction methods we examine their application to the 3D problem. Finally, it is shown that the back projection theorem can be generalized to cone beam projections. This allows to state a new inversion formula suitable for both the 4 π parallel and divergent geometries. It leads to the generalization of the ''rho-filtered back projection'' algorithm which is outlined

  12. Half-Fan-Based Intensity-Weighted Region-of-Interest Imaging for Low-Dose Cone-Beam CT in Image-Guided Radiation Therapy.

    Science.gov (United States)

    Yoo, Boyeol; Son, Kihong; Pua, Rizza; Kim, Jinsung; Solodov, Alexander; Cho, Seungryong

    2016-10-01

    With the increased use of computed tomography (CT) in clinics, dose reduction is the most important feature people seek when considering new CT techniques or applications. We developed an intensity-weighted region-of-interest (IWROI) imaging method in an exact half-fan geometry to reduce the imaging radiation dose to patients in cone-beam CT (CBCT) for image-guided radiation therapy (IGRT). While dose reduction is highly desirable, preserving the high-quality images of the ROI is also important for target localization in IGRT. An intensity-weighting (IW) filter made of copper was mounted in place of a bowtie filter on the X-ray tube unit of an on-board imager (OBI) system such that the filter can substantially reduce radiation exposure to the outer ROI. In addition to mounting the IW filter, the lead-blade collimation of the OBI was adjusted to produce an exact half-fan scanning geometry for a further reduction of the radiation dose. The chord-based rebinned backprojection-filtration (BPF) algorithm in circular CBCT was implemented for image reconstruction, and a humanoid pelvis phantom was used for the IWROI imaging experiment. The IWROI image of the phantom was successfully reconstructed after beam-quality correction, and it was registered to the reference image within an acceptable level of tolerance. Dosimetric measurements revealed that the dose is reduced by approximately 61% in the inner ROI and by 73% in the outer ROI compared to the conventional bowtie filter-based half-fan scan. The IWROI method substantially reduces the imaging radiation dose and provides reconstructed images with an acceptable level of quality for patient setup and target localization. The proposed half-fan-based IWROI imaging technique can add a valuable option to CBCT in IGRT applications.

  13. An optimization-based method for geometrical calibration in cone-beam CT without dedicated phantoms

    International Nuclear Information System (INIS)

    Panetta, D; Belcari, N; Guerra, A Del; Moehrs, S

    2008-01-01

    In this paper we present a new method for the determination of geometrical misalignments in cone-beam CT scanners, from the analysis of the projection data of a generic object. No a priori knowledge of the object shape and positioning is required. We show that a cost function, which depends on the misalignment parameters, can be defined using the projection data and that such a cost function has a local minimum in correspondence to the actual parameters of the system. Hence, the calibration of the scanner can be carried out by minimizing the cost function using standard optimization techniques. The method is developed for a particular class of 3D object functions, for which the redundancy of the fan beam sinogram in the transaxial midplane can be extended to cone-beam projection data, even at wide cone angles. The method has an approximated validity for objects which do not belong to that class; in that case, a suitable subset of the projection data can be selected in order to compute the cost function. We show by numerical simulations that our method is capable to determine with high accuracy the most critical misalignment parameters of the scanner, i.e., the transversal shift and the skew of the detector. Additionally, the detector slant can be determined. Other parameters such as the detector tilt, the longitudinal shift and the error in the source-detector distance cannot be determined with our method, as the proposed cost function has a very weak dependence on them. However, due to the negligible influence of these latter parameters in the reconstructed image quality, they can be kept fixed at estimated values in both calibration and reconstruction processes without compromising the final result. A trade-off between computational cost and calibration accuracy must be considered when choosing the data subset used for the computation of the cost function. Results on real data of a mouse femur as obtained with a small animal micro-CT are shown as well, proving

  14. CT Imaging of facial trauma. Role of different types of reconstruction. Part I - bones

    International Nuclear Information System (INIS)

    Myga-Porosilo, J.; Sraga, W.; Borowiak, H.; Jackowska, Z.; Kluczewska, E.; Skrzelewski, S.

    2011-01-01

    Background: Injury to the facial skeleton and the adjoining soft tissues is a frequently occurring condition. The main aim of this work was to assess the value of multiplanar and three-dimensional (3D) reconstruction computed tomography (CT) images obtained by using multi-detector row technology in spiral data acquisition in patients with facial skeleton injury. The authors attempted to answer the following questions: Are there particular mechanisms and types of injuries or locations of fractures which can be diagnosed significantly more effectively by conducting additional multiplanar image reconstructions? Do 3D image reconstructions contribute to the diagnostic process, to what extent? Compared to other imaging techniques, is the spiral CT data acquisition a more convenient for the patient and a faster investigation method of diagnosing post-injury lesions involving the facial skeleton? Material/Methods: Sixty-seven patients diagnosed with injury to the facial skeleton were referred for emergent CT scanning. Each patient underwent a CT scan with the use of a GE HiSpeed Qx/i scanner. The scans were conducted with the use of spiral data acquisition technique in the transverse plane. The following secondary image reconstructions were conducted for each patient: a two dimensional (2D) multiplanar reconstruction (MPR), maximum intensity projection (MIP), and 3D volume rendering (VR). Post-injury lesions of the facial skeleton were assessed and the presence of any loose displaced bone fragments was taken into consideration. Results: As far as fracture imaging is concerned, the 2D image reconstruction and volume rendering proved to be the most effective in the majority of locations. 3D image reconstructions proved the most sensitive in most cases of loose displaced bone fragments, except for fine structures such as the ethmoid bone and the inferior orbital wall. Conclusions: 1. Multiplanar computer reconstructions increase the effectiveness of visualisation of

  15. CT imaging of congenital lung lesions: effect of iterative reconstruction on diagnostic performance and radiation dose

    International Nuclear Information System (INIS)

    Haggerty, Jay E.; Smith, Ethan A.; Dillman, Jonathan R.; Kunisaki, Shaun M.

    2015-01-01

    Different iterative reconstruction techniques are available for use in pediatric computed tomography (CT), but these techniques have not been systematically evaluated in infants. To determine the effect of iterative reconstruction on diagnostic performance, image quality and radiation dose in infants undergoing CT evaluation for congenital lung lesions. A retrospective review of contrast-enhanced chest CT in infants (<1 year) with congenital lung lesions was performed. CT examinations were reviewed to document the type of lung lesion, vascular anatomy, image noise measurements and image reconstruction method. CTDI vol was used to calculate size-specific dose estimates (SSDE). CT findings were correlated with intraoperative and histopathological findings. Analysis of variance and the Student's t-test were used to compare image noise measurements and radiation dose estimates between groups. Fifteen CT examinations used filtered back projection (FBP; mean age: 84 days), 15 used adaptive statistical iterative reconstruction (ASiR; mean age: 93 days), and 11 used model-based iterative reconstruction (MBIR; mean age: 98 days). Compared to operative findings, 13/15 (87%), 14/15 (93%) and 11/11 (100%) lesions were correctly characterized using FBP, ASiR and MBIR, respectively. Arterial anatomy was correctly identified in 12/15 (80%) using FBP, 13/15 (87%) using ASiR and 11/11 (100%) using MBIR. Image noise was less for MBIR vs. ASiR (P < 0.0001). Mean SSDE was different among groups (P = 0.003; FBP = 7.35 mGy, ASiR = 1.89 mGy, MBIR = 1.49 mGy). Congenital lung lesions can be adequately characterized in infants using iterative CT reconstruction techniques while maintaining image quality and lowering radiation dose. (orig.)

  16. CT imaging of congenital lung lesions: effect of iterative reconstruction on diagnostic performance and radiation dose

    Energy Technology Data Exchange (ETDEWEB)

    Haggerty, Jay E.; Smith, Ethan A.; Dillman, Jonathan R. [University of Michigan Health System, Section of Pediatric Radiology, Department of Radiology, C.S. Mott Children' s Hospital, Ann Arbor, MI (United States); Kunisaki, Shaun M. [University of Michigan Health System, Section of Pediatric Surgery, Department of Surgery, C.S. Mott Children' s Hospital, Ann Arbor, MI (United States)

    2015-07-15

    Different iterative reconstruction techniques are available for use in pediatric computed tomography (CT), but these techniques have not been systematically evaluated in infants. To determine the effect of iterative reconstruction on diagnostic performance, image quality and radiation dose in infants undergoing CT evaluation for congenital lung lesions. A retrospective review of contrast-enhanced chest CT in infants (<1 year) with congenital lung lesions was performed. CT examinations were reviewed to document the type of lung lesion, vascular anatomy, image noise measurements and image reconstruction method. CTDI{sub vol} was used to calculate size-specific dose estimates (SSDE). CT findings were correlated with intraoperative and histopathological findings. Analysis of variance and the Student's t-test were used to compare image noise measurements and radiation dose estimates between groups. Fifteen CT examinations used filtered back projection (FBP; mean age: 84 days), 15 used adaptive statistical iterative reconstruction (ASiR; mean age: 93 days), and 11 used model-based iterative reconstruction (MBIR; mean age: 98 days). Compared to operative findings, 13/15 (87%), 14/15 (93%) and 11/11 (100%) lesions were correctly characterized using FBP, ASiR and MBIR, respectively. Arterial anatomy was correctly identified in 12/15 (80%) using FBP, 13/15 (87%) using ASiR and 11/11 (100%) using MBIR. Image noise was less for MBIR vs. ASiR (P < 0.0001). Mean SSDE was different among groups (P = 0.003; FBP = 7.35 mGy, ASiR = 1.89 mGy, MBIR = 1.49 mGy). Congenital lung lesions can be adequately characterized in infants using iterative CT reconstruction techniques while maintaining image quality and lowering radiation dose. (orig.)

  17. SART-Type Half-Threshold Filtering Approach for CT Reconstruction.

    Science.gov (United States)

    Yu, Hengyong; Wang, Ge

    2014-01-01

    The [Formula: see text] regularization problem has been widely used to solve the sparsity constrained problems. To enhance the sparsity constraint for better imaging performance, a promising direction is to use the [Formula: see text] norm (0 < p < 1) and solve the [Formula: see text] minimization problem. Very recently, Xu et al. developed an analytic solution for the [Formula: see text] regularization via an iterative thresholding operation, which is also referred to as half-threshold filtering. In this paper, we design a simultaneous algebraic reconstruction technique (SART)-type half-threshold filtering framework to solve the computed tomography (CT) reconstruction problem. In the medical imaging filed, the discrete gradient transform (DGT) is widely used to define the sparsity. However, the DGT is noninvertible and it cannot be applied to half-threshold filtering for CT reconstruction. To demonstrate the utility of the proposed SART-type half-threshold filtering framework, an emphasis of this paper is to construct a pseudoinverse transforms for DGT. The proposed algorithms are evaluated with numerical and physical phantom data sets. Our results show that the SART-type half-threshold filtering algorithms have great potential to improve the reconstructed image quality from few and noisy projections. They are complementary to the counterparts of the state-of-the-art soft-threshold filtering and hard-threshold filtering.

  18. Four-dimensional cone beam CT reconstruction and enhancement using a temporal nonlocal means method

    Energy Technology Data Exchange (ETDEWEB)

    Jia Xun; Tian Zhen; Lou Yifei; Sonke, Jan-Jakob; Jiang, Steve B. [Center for Advanced Radiotherapy Technologies and Department of Radiation Medicine and Applied Sciences, University of California San Diego, La Jolla, California 92037 (United States); School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, Georgia 30318 (United States); Department of Radiation Oncology, Netherlands Cancer Institute-Antoni van Leeuwenhoek Hospital, Plesmanlaan 121, 1066 CX Amsterdam (Netherlands); Center for Advanced Radiotherapy Technologies and Department of Radiation Medicine and Applied Sciences, University of California San Diego, La Jolla, California 92037 (United States)

    2012-09-15

    Purpose: Four-dimensional cone beam computed tomography (4D-CBCT) has been developed to provide respiratory phase-resolved volumetric imaging in image guided radiation therapy. Conventionally, it is reconstructed by first sorting the x-ray projections into multiple respiratory phase bins according to a breathing signal extracted either from the projection images or some external surrogates, and then reconstructing a 3D CBCT image in each phase bin independently using FDK algorithm. This method requires adequate number of projections for each phase, which can be achieved using a low gantry rotation or multiple gantry rotations. Inadequate number of projections in each phase bin results in low quality 4D-CBCT images with obvious streaking artifacts. 4D-CBCT images at different breathing phases share a lot of redundant information, because they represent the same anatomy captured at slightly different temporal points. Taking this redundancy along the temporal dimension into account can in principle facilitate the reconstruction in the situation of inadequate number of projection images. In this work, the authors propose two novel 4D-CBCT algorithms: an iterative reconstruction algorithm and an enhancement algorithm, utilizing a temporal nonlocal means (TNLM) method. Methods: The authors define a TNLM energy term for a given set of 4D-CBCT images. Minimization of this term favors those 4D-CBCT images such that any anatomical features at one spatial point at one phase can be found in a nearby spatial point at neighboring phases. 4D-CBCT reconstruction is achieved by minimizing a total energy containing a data fidelity term and the TNLM energy term. As for the image enhancement, 4D-CBCT images generated by the FDK algorithm are enhanced by minimizing the TNLM function while keeping the enhanced images close to the FDK results. A forward-backward splitting algorithm and a Gauss-Jacobi iteration method are employed to solve the problems. The algorithms implementation on

  19. GPU-accelerated few-view CT reconstruction using the OSC and TV techniques

    Energy Technology Data Exchange (ETDEWEB)

    Matenine, Dmitri [Montreal Univ., QC (Canada). Dept. de Physique; Hissoiny, Sami [Ecole Polytechnique de Montreal, QC (Canada). Dept. de Genie Informatique et Genie Logiciel; Despres, Philippe [Centre Hospitalier Univ. de Quebec, QC (Canada). Dept. de Radio-Oncologie

    2011-07-01

    The present work proposes a promising iterative reconstruction technique designed specifically for X-ray transmission computed tomography (CT). The main objective is to reduce diagnostic radiation dose through the reduction of the number of CT projections, while preserving image quality. The second objective is to provide a fast implementation compatible with clinical activities. The proposed tomographic reconstruction technique is a combination of the Ordered Subsets Convex (OSC) algorithm and the Total Variation minimization (TV) regularization technique. The results in terms of image quality and computational speed are discussed. Using this technique, it was possible to obtain reconstructed slices of relatively good quality with as few as 100 projections, leading to potential dose reduction factors of up to an order of magnitude depending on the application. The algorithm was implemented on a Graphical Processing Unit (GPU) and yielded reconstruction times of approximately 185 ms per slice. (orig.)

  20. Exact cone beam CT with a spiral scan

    International Nuclear Information System (INIS)

    Tam, K.C.; Samarasekera, S.; Sauer, F.

    1998-01-01

    A method is developed which makes it possible to scan and reconstruct an object with cone beam x-rays in a spiral scan path with area detectors much shorter than the length of the object. The method is mathematically exact. If only a region of interest of the object is to be imaged, a top circle scan at the top level of the region of interest and a bottom circle scan at the bottom level of the region of interest are added. The height of the detector is required to cover only the distance between adjacent turns in the spiral projected at the detector. To reconstruct the object, the Radon transform for each plane intersecting the object is computed from the totality of the cone beam data. This is achieved by suitably combining the cone beam data taken at different source positions on the scan path; the angular range of the cone beam data required at each source position can be determined easily with a mask which is the spiral scan path projected on the detector from the current source position. The spiral scan algorithm has been successfully validated with simulated cone beam data. (author)

  1. Brain perfusion imaging using a Reconstruction-of-Difference (RoD) approach for cone-beam computed tomography

    Science.gov (United States)

    Mow, M.; Zbijewski, W.; Sisniega, A.; Xu, J.; Dang, H.; Stayman, J. W.; Wang, X.; Foos, D. H.; Koliatsos, V.; Aygun, N.; Siewerdsen, J. H.

    2017-03-01

    Purpose: To improve the timely detection and treatment of intracranial hemorrhage or ischemic stroke, recent efforts include the development of cone-beam CT (CBCT) systems for perfusion imaging and new approaches to estimate perfusion parameters despite slow rotation speeds compared to multi-detector CT (MDCT) systems. This work describes development of a brain perfusion CBCT method using a reconstruction of difference (RoD) approach to enable perfusion imaging on a newly developed CBCT head scanner prototype. Methods: A new reconstruction approach using RoD with a penalized-likelihood framework was developed to image the temporal dynamics of vascular enhancement. A digital perfusion simulation was developed to give a realistic representation of brain anatomy, artifacts, noise, scanner characteristics, and hemo-dynamic properties. This simulation includes a digital brain phantom, time-attenuation curves and noise parameters, a novel forward projection method for improved computational efficiency, and perfusion parameter calculation. Results: Our results show the feasibility of estimating perfusion parameters from a set of images reconstructed from slow scans, sparse data sets, and arc length scans as short as 60 degrees. The RoD framework significantly reduces noise and time-varying artifacts from inconsistent projections. Proper regularization and the use of overlapping reconstructed arcs can potentially further decrease bias and increase temporal resolution, respectively. Conclusions: A digital brain perfusion simulation with RoD imaging approach has been developed and supports the feasibility of using a CBCT head scanner for perfusion imaging. Future work will include testing with data acquired using a 3D-printed perfusion phantom currently and translation to preclinical and clinical studies.

  2. Image quality in children with low-radiation chest CT using adaptive statistical iterative reconstruction and model-based iterative reconstruction.

    Directory of Open Access Journals (Sweden)

    Jihang Sun

    Full Text Available OBJECTIVE: To evaluate noise reduction and image quality improvement in low-radiation dose chest CT images in children using adaptive statistical iterative reconstruction (ASIR and a full model-based iterative reconstruction (MBIR algorithm. METHODS: Forty-five children (age ranging from 28 days to 6 years, median of 1.8 years who received low-dose chest CT scans were included. Age-dependent noise index (NI was used for acquisition. Images were retrospectively reconstructed using three methods: MBIR, 60% of ASIR and 40% of conventional filtered back-projection (FBP, and FBP. The subjective quality of the images was independently evaluated by two radiologists. Objective noises in the left ventricle (LV, muscle, fat, descending aorta and lung field at the layer with the largest cross-section area of LV were measured, with the region of interest about one fourth to half of the area of descending aorta. Optimized signal-to-noise ratio (SNR was calculated. RESULT: In terms of subjective quality, MBIR images were significantly better than ASIR and FBP in image noise and visibility of tiny structures, but blurred edges were observed. In terms of objective noise, MBIR and ASIR reconstruction decreased the image noise by 55.2% and 31.8%, respectively, for LV compared with FBP. Similarly, MBIR and ASIR reconstruction increased the SNR by 124.0% and 46.2%, respectively, compared with FBP. CONCLUSION: Compared with FBP and ASIR, overall image quality and noise reduction were significantly improved by MBIR. MBIR image could reconstruct eligible chest CT images in children with lower radiation dose.

  3. Empirical average-case relation between undersampling and sparsity in X-ray CT

    DEFF Research Database (Denmark)

    Jørgensen, Jakob Sauer; Sidky, Emil Y.; Hansen, Per Christian

    2015-01-01

    In X-ray computed tomography (CT) it is generally acknowledged that reconstruction methods exploiting image sparsity allow reconstruction from a significantly reduced number of projections. The use of such reconstruction methods is inspired by recent progress in compressed sensing (CS). However......, the CS framework provides neither guarantees of accurate CT reconstruction, nor any relation between sparsity and a sufficient number of measurements for recovery, i.e., perfect reconstruction from noise-free data. We consider reconstruction through 1-norm minimization, as proposed in CS, from data...... obtained using a standard CT fan-beam sampling pattern. In empirical simulation studies we establish quantitatively a relation between the image sparsity and the sufficient number of measurements for recovery within image classes motivated by tomographic applications. We show empirically that the specific...

  4. Pediatric 320-row cardiac computed tomography using electrocardiogram-gated model-based full iterative reconstruction

    Energy Technology Data Exchange (ETDEWEB)

    Shirota, Go; Maeda, Eriko; Namiki, Yoko; Bari, Razibul; Abe, Osamu [The University of Tokyo, Department of Radiology, Graduate School of Medicine, Tokyo (Japan); Ino, Kenji [The University of Tokyo Hospital, Imaging Center, Tokyo (Japan); Torigoe, Rumiko [Toshiba Medical Systems, Tokyo (Japan)

    2017-10-15

    Full iterative reconstruction algorithm is available, but its diagnostic quality in pediatric cardiac CT is unknown. To compare the imaging quality of two algorithms, full and hybrid iterative reconstruction, in pediatric cardiac CT. We included 49 children with congenital cardiac anomalies who underwent cardiac CT. We compared quality of images reconstructed using the two algorithms (full and hybrid iterative reconstruction) based on a 3-point scale for the delineation of the following anatomical structures: atrial septum, ventricular septum, right atrium, right ventricle, left atrium, left ventricle, main pulmonary artery, ascending aorta, aortic arch including the patent ductus arteriosus, descending aorta, right coronary artery and left main trunk. We evaluated beam-hardening artifacts from contrast-enhancement material using a 3-point scale, and we evaluated the overall image quality using a 5-point scale. We also compared image noise, signal-to-noise ratio and contrast-to-noise ratio between the algorithms. The overall image quality was significantly higher with full iterative reconstruction than with hybrid iterative reconstruction (3.67±0.79 vs. 3.31±0.89, P=0.0072). The evaluation scores for most of the gross structures were higher with full iterative reconstruction than with hybrid iterative reconstruction. There was no significant difference between full and hybrid iterative reconstruction for the presence of beam-hardening artifacts. Image noise was significantly lower in full iterative reconstruction, while signal-to-noise ratio and contrast-to-noise ratio were significantly higher in full iterative reconstruction. The diagnostic quality was superior in images with cardiac CT reconstructed with electrocardiogram-gated full iterative reconstruction. (orig.)

  5. Pediatric 320-row cardiac computed tomography using electrocardiogram-gated model-based full iterative reconstruction

    International Nuclear Information System (INIS)

    Shirota, Go; Maeda, Eriko; Namiki, Yoko; Bari, Razibul; Abe, Osamu; Ino, Kenji; Torigoe, Rumiko

    2017-01-01

    Full iterative reconstruction algorithm is available, but its diagnostic quality in pediatric cardiac CT is unknown. To compare the imaging quality of two algorithms, full and hybrid iterative reconstruction, in pediatric cardiac CT. We included 49 children with congenital cardiac anomalies who underwent cardiac CT. We compared quality of images reconstructed using the two algorithms (full and hybrid iterative reconstruction) based on a 3-point scale for the delineation of the following anatomical structures: atrial septum, ventricular septum, right atrium, right ventricle, left atrium, left ventricle, main pulmonary artery, ascending aorta, aortic arch including the patent ductus arteriosus, descending aorta, right coronary artery and left main trunk. We evaluated beam-hardening artifacts from contrast-enhancement material using a 3-point scale, and we evaluated the overall image quality using a 5-point scale. We also compared image noise, signal-to-noise ratio and contrast-to-noise ratio between the algorithms. The overall image quality was significantly higher with full iterative reconstruction than with hybrid iterative reconstruction (3.67±0.79 vs. 3.31±0.89, P=0.0072). The evaluation scores for most of the gross structures were higher with full iterative reconstruction than with hybrid iterative reconstruction. There was no significant difference between full and hybrid iterative reconstruction for the presence of beam-hardening artifacts. Image noise was significantly lower in full iterative reconstruction, while signal-to-noise ratio and contrast-to-noise ratio were significantly higher in full iterative reconstruction. The diagnostic quality was superior in images with cardiac CT reconstructed with electrocardiogram-gated full iterative reconstruction. (orig.)

  6. Novel iterative reconstruction method with optimal dose usage for partially redundant CT-acquisition

    International Nuclear Information System (INIS)

    Bruder, H; Raupach, R; Sunnegardh, J; Allmendinger, T; Klotz, E; Stierstorfer, K; Flohr, T

    2015-01-01

    In CT imaging, a variety of applications exist which are strongly SNR limited. However, in some cases redundant data of the same body region provide additional quanta.Examples: in dual energy CT, the spatial resolution has to be compromised to provide good SNR for material decomposition. However, the respective spectral dataset of the same body region provides additional quanta which might be utilized to improve SNR of each spectral component. Perfusion CT is a high dose application, and dose reduction is highly desirable. However, a meaningful evaluation of perfusion parameters might be impaired by noisy time frames. On the other hand, the SNR of the average of all time frames is extremely high.In redundant CT acquisitions, multiple image datasets can be reconstructed and averaged to composite image data. These composite image data, however, might be compromised with respect to contrast resolution and/or spatial resolution and/or temporal resolution. These observations bring us to the idea of transferring high SNR of composite image data to low SNR ‘source’ image data, while maintaining their resolution.It has been shown that the noise characteristics of CT image data can be improved by iterative reconstruction (Popescu et al 2012 Book of Abstracts, 2nd CT Meeting (Salt Lake City, UT) p 148). In case of data dependent Gaussian noise it can be modelled with image-based iterative reconstruction at least in an approximate manner (Bruder et al 2011 Proc. SPIE 7961 79610J).We present a generalized update equation in image space, consisting of a linear combination of the previous update, a correction term which is constrained by the source image data, and a regularization prior, which is initialized by the composite image data. This iterative reconstruction approach we call bimodal reconstruction (BMR).Based on simulation data it is shown that BMR can improve low contrast detectability, substantially reduces the noise power and has the potential to recover spatial

  7. Novel iterative reconstruction method with optimal dose usage for partially redundant CT-acquisition

    Science.gov (United States)

    Bruder, H.; Raupach, R.; Sunnegardh, J.; Allmendinger, T.; Klotz, E.; Stierstorfer, K.; Flohr, T.

    2015-11-01

    In CT imaging, a variety of applications exist which are strongly SNR limited. However, in some cases redundant data of the same body region provide additional quanta. Examples: in dual energy CT, the spatial resolution has to be compromised to provide good SNR for material decomposition. However, the respective spectral dataset of the same body region provides additional quanta which might be utilized to improve SNR of each spectral component. Perfusion CT is a high dose application, and dose reduction is highly desirable. However, a meaningful evaluation of perfusion parameters might be impaired by noisy time frames. On the other hand, the SNR of the average of all time frames is extremely high. In redundant CT acquisitions, multiple image datasets can be reconstructed and averaged to composite image data. These composite image data, however, might be compromised with respect to contrast resolution and/or spatial resolution and/or temporal resolution. These observations bring us to the idea of transferring high SNR of composite image data to low SNR ‘source’ image data, while maintaining their resolution. It has been shown that the noise characteristics of CT image data can be improved by iterative reconstruction (Popescu et al 2012 Book of Abstracts, 2nd CT Meeting (Salt Lake City, UT) p 148). In case of data dependent Gaussian noise it can be modelled with image-based iterative reconstruction at least in an approximate manner (Bruder et al 2011 Proc. SPIE 7961 79610J). We present a generalized update equation in image space, consisting of a linear combination of the previous update, a correction term which is constrained by the source image data, and a regularization prior, which is initialized by the composite image data. This iterative reconstruction approach we call bimodal reconstruction (BMR). Based on simulation data it is shown that BMR can improve low contrast detectability, substantially reduces the noise power and has the potential to recover

  8. SU-E-I-10: Investigation On Detectability of a Small Target for Different Slice Direction of a Volumetric Cone Beam CT Image

    Energy Technology Data Exchange (ETDEWEB)

    Lee, C; Han, M; Baek, J [Yonsei University, Incheon (Korea, Republic of)

    2015-06-15

    Purpose: To investigate the detectability of a small target for different slice direction of a volumetric cone beam CT image and its impact on dose reduction. Methods: Analytic projection data of a sphere object (1 mm diameter, 0.2/cm attenuation coefficient) were generated and reconstructed by FDK algorithm. In this work, we compared the detectability of the small target from four different backprojection Methods: hanning weighted ramp filter with linear interpolation (RECON 1), hanning weighted ramp filter with Fourier interpolation (RECON2), ramp filter with linear interpolation (RECON 3), and ramp filter with Fourier interpolation (RECON4), respectively. For noise simulation, 200 photons per measurement were used, and the noise only data were reconstructed using FDK algorithm. For each reconstructed volume, axial and coronal slice were extracted and detection-SNR was calculated using channelized Hotelling observer (CHO) with dense difference-of-Gaussian (D-DOG) channels. Results: Detection-SNR of coronal images varies for different backprojection methods, while axial images have a similar detection-SNR. Detection-SNR{sup 2} ratios of coronal and axial images in RECON1 and RECON2 are 1.33 and 1.15, implying that the coronal image has a better detectability than axial image. In other words, using coronal slices for the small target detection can reduce the patient dose about 33% and 15% compared to using axial slices in RECON 1 and RECON 2. Conclusion: In this work, we investigated slice direction dependent detectability of a volumetric cone beam CT image. RECON 1 and RECON 2 produced the highest detection-SNR, with better detectability in coronal slices. These results indicate that it is more beneficial to use coronal slice to improve detectability of a small target in a volumetric cone beam CT image. This research was supported by the MSIP (Ministry of Science, ICT and Future Planning), Korea, under the IT Consilience Creative Program (NIPA-2014-H0201

  9. SU-E-I-10: Investigation On Detectability of a Small Target for Different Slice Direction of a Volumetric Cone Beam CT Image

    International Nuclear Information System (INIS)

    Lee, C; Han, M; Baek, J

    2015-01-01

    Purpose: To investigate the detectability of a small target for different slice direction of a volumetric cone beam CT image and its impact on dose reduction. Methods: Analytic projection data of a sphere object (1 mm diameter, 0.2/cm attenuation coefficient) were generated and reconstructed by FDK algorithm. In this work, we compared the detectability of the small target from four different backprojection Methods: hanning weighted ramp filter with linear interpolation (RECON 1), hanning weighted ramp filter with Fourier interpolation (RECON2), ramp filter with linear interpolation (RECON 3), and ramp filter with Fourier interpolation (RECON4), respectively. For noise simulation, 200 photons per measurement were used, and the noise only data were reconstructed using FDK algorithm. For each reconstructed volume, axial and coronal slice were extracted and detection-SNR was calculated using channelized Hotelling observer (CHO) with dense difference-of-Gaussian (D-DOG) channels. Results: Detection-SNR of coronal images varies for different backprojection methods, while axial images have a similar detection-SNR. Detection-SNR 2 ratios of coronal and axial images in RECON1 and RECON2 are 1.33 and 1.15, implying that the coronal image has a better detectability than axial image. In other words, using coronal slices for the small target detection can reduce the patient dose about 33% and 15% compared to using axial slices in RECON 1 and RECON 2. Conclusion: In this work, we investigated slice direction dependent detectability of a volumetric cone beam CT image. RECON 1 and RECON 2 produced the highest detection-SNR, with better detectability in coronal slices. These results indicate that it is more beneficial to use coronal slice to improve detectability of a small target in a volumetric cone beam CT image. This research was supported by the MSIP (Ministry of Science, ICT and Future Planning), Korea, under the IT Consilience Creative Program (NIPA-2014-H0201

  10. Pre-reconstruction dual-energy, X-ray computerized tomography (CT): theory, implementation, results, and clinical use

    International Nuclear Information System (INIS)

    Oravez, W.T.

    1986-01-01

    For the task of bone mineral measurement, single-energy quantitative CT has demonstrated its worth in terms of precision for most longitudinal clinical studies. However, for cross-sectional clinical studies, known inaccuracy exists due to less than robust beam-hardening corrections, and negatively biased bone mineral measurement, due to the effect of unknown variable concentration of bone marrow fat within the metabolically active trabecular bone space. A dual-energy measurement technique provides a solution to these deficiencies of single-energy measurements. The fundamental theory of dual-energy measurement techniques is based on a Compton-photoelectric approximation and the mixture rule for the total attenuation coefficient. Resolution of atomic composition and electron density components of attenuation should then be possible. To take full advantage of these principles, the raw dual-energy projection values are operated on before reconstruction. This method beam-hardening and composition-selective imaging. Rapid kilovoltage switching between projection measurements, rather than serial measurements, assures the best measurement quality

  11. Direct Reconstruction of CT-based Attenuation Correction Images for PET with Cluster-Based Penalties

    Science.gov (United States)

    Kim, Soo Mee; Alessio, Adam M.; De Man, Bruno; Asma, Evren; Kinahan, Paul E.

    2015-01-01

    Extremely low-dose CT acquisitions for the purpose of PET attenuation correction will have a high level of noise and biasing artifacts due to factors such as photon starvation. This work explores a priori knowledge appropriate for CT iterative image reconstruction for PET attenuation correction. We investigate the maximum a posteriori (MAP) framework with cluster-based, multinomial priors for the direct reconstruction of the PET attenuation map. The objective function for direct iterative attenuation map reconstruction was modeled as a Poisson log-likelihood with prior terms consisting of quadratic (Q) and mixture (M) distributions. The attenuation map is assumed to have values in 4 clusters: air+background, lung, soft tissue, and bone. Under this assumption, the MP was a mixture probability density function consisting of one exponential and three Gaussian distributions. The relative proportion of each cluster was jointly estimated during each voxel update of direct iterative coordinate decent (dICD) method. Noise-free data were generated from NCAT phantom and Poisson noise was added. Reconstruction with FBP (ramp filter) was performed on the noise-free (ground truth) and noisy data. For the noisy data, dICD reconstruction was performed with the combination of different prior strength parameters (β and γ) of Q- and M-penalties. The combined quadratic and mixture penalties reduces the RMSE by 18.7% compared to post-smoothed iterative reconstruction and only 0.7% compared to quadratic alone. For direct PET attenuation map reconstruction from ultra-low dose CT acquisitions, the combination of quadratic and mixture priors offers regularization of both variance and bias and is a potential method to derive attenuation maps with negligible patient dose. However, the small improvement in quantitative accuracy relative to the substantial increase in algorithm complexity does not currently justify the use of mixture-based PET attenuation priors for reconstruction of CT

  12. Gamma regularization based reconstruction for low dose CT

    International Nuclear Information System (INIS)

    Zhang, Junfeng; Chen, Yang; Hu, Yining; Luo, Limin; Shu, Huazhong; Li, Bicao; Liu, Jin; Coatrieux, Jean-Louis

    2015-01-01

    Reducing the radiation in computerized tomography is today a major concern in radiology. Low dose computerized tomography (LDCT) offers a sound way to deal with this problem. However, more severe noise in the reconstructed CT images is observed under low dose scan protocols (e.g. lowered tube current or voltage values). In this paper we propose a Gamma regularization based algorithm for LDCT image reconstruction. This solution is flexible and provides a good balance between the regularizations based on l 0 -norm and l 1 -norm. We evaluate the proposed approach using the projection data from simulated phantoms and scanned Catphan phantoms. Qualitative and quantitative results show that the Gamma regularization based reconstruction can perform better in both edge-preserving and noise suppression when compared with other norms. (paper)

  13. The use of a neuronavigator in combination with three-dimensional CT reconstruction and angiography

    Energy Technology Data Exchange (ETDEWEB)

    Watanabe, Eiju; Mayanagi, Yoshiaki (Tokyo Metropolitan Police Hospital (Japan)); Ishii, Shigeo; Yoshimoto, Satonobu; Takakura, Kintomo

    1989-08-01

    A new CT-stereotactic device (navigator) has been developed which translates the operating site into preoperative CT coordination. We applied this system in combination with three-dimensional CT reconstruction and with angiogram. Method: The system consists of a 6-joint robotic arm and a personal computer. It projects the location of the arm tip onto a correlating CT slice with a cursor, which guides a surgeon toward his intracranial target during open surgery. The system translates the tip location into a 3D-CT reconstructed image and an angiogram. The system worked as the core of a multimodality navigation system during surgery. The detection error was less than 5 mm, which proved sufficient for open microsurgery. The system was combined with a 3D-CT reconstruction system. It produces 3D images and cuts off the surface image at the point of the cursor, simulating surgical excision. The navigator controlled the location of the cutting cursor, thus establishing a real-time surgical simulation. When the angiogram was referred to, it became easy to identify bridging veins within a small operating field. Conclusion: The neuronavigator combines various diagnostic images into one data base and effectively guides the surgeon during surgery. (author).

  14. The use of a neuronavigator in combination with three-dimensional CT reconstruction and angiography

    International Nuclear Information System (INIS)

    Watanabe, Eiju; Mayanagi, Yoshiaki; Ishii, Shigeo; Yoshimoto, Satonobu; Takakura, Kintomo.

    1989-01-01

    A new CT-stereotactic device (navigator) has been developed which translates the operating site into preoperative CT coordination. We applied this system in combination with three-dimensional CT reconstruction and with angiogram. Method: The system consists of a 6-joint robotic arm and a personal computer. It projects the location of the arm tip onto a correlating CT slice with a cursor, which guides a surgeon toward his intracranial target during open surgery. The system translates the tip location into a 3D-CT reconstructed image and an angiogram. The system worked as the core of a multimodality navigation system during surgery. The detection error was less than 5 mm, which proved sufficient for open microsurgery. The system was combined with a 3D-CT reconstruction system. It produces 3D images and cuts off the surface image at the point of the cursor, simulating surgical excision. The navigator controlled the location of the cutting cursor, thus establishing a real-time surgical simulation. When the angiogram was referred to, it became easy to identify bridging veins within a small operating field. Conclusion: The neuronavigator combines various diagnostic images into one data base and effectively guides the surgeon during surgery. (author)

  15. Postoperative evaluation after anterior cruciate ligament reconstruction: Measurements and abnormalities on radiographic and CT imaging

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Min Cheol; Choi, Yun Sun; KIm, Hyoung Seop; Choi, Nam Hong [Nowon Eulji Medical Center, Eulji University, Seoul (Korea, Republic of)

    2016-11-15

    Reconstruction of a ruptured anterior cruciate ligament (ACL) is a well-established procedure for repair of ACL injury. Despite improvement of surgical and rehabilitation techniques over the past decades, up to 25% of patients still fail to regain satisfactory function after an ACL reconstruction. With development of CT imaging techniques for reducing metal artifacts, multi-planar reconstruction, and three-dimensional reconstruction, early post-operative imaging is increasingly being used to provide immediate feedback to surgeons regarding tunnel positioning, fixation, and device placement. Early post-operative radiography and CT imaging are easy to perform and serve as the baseline examinations for future reference.

  16. SU-C-207A-03: Development of Proton CT Imaging System Using Thick Scintillator and CCD Camera

    Energy Technology Data Exchange (ETDEWEB)

    Tanaka, S; Uesaka, M [The University of Tokyo, Tokyo (Japan); Nishio, T; Tsuneda, M [Hiroshima University, Hiroshima (Japan); Matsushita, K [Rikkyo University, Tokyo (Japan); Kabuki, S [Tokai University, Isehara (Japan)

    2016-06-15

    Purpose: In the treatment planning of proton therapy, Water Equivalent Length (WEL), which is the parameter for the calculation of dose and the range of proton, is derived by X-ray CT (xCT) image and xCT-WEL conversion. However, about a few percent error in the accuracy of proton range calculation through this conversion has been reported. The purpose of this study is to construct a proton CT (pCT) imaging system for an evaluation of the error. Methods: The pCT imaging system was constructed with a thick scintillator and a cooled CCD camera, which acquires the two-dimensional image of integrated value of the scintillation light toward the beam direction. The pCT image is reconstructed by FBP method using a correction between the light intensity and residual range of proton beam. An experiment for the demonstration of this system was performed with 70-MeV proton beam provided by NIRS cyclotron. The pCT image of several objects reconstructed from the experimental data was evaluated quantitatively. Results: Three-dimensional pCT images of several objects were reconstructed experimentally. A finestructure of approximately 1 mm was clearly observed. The position resolution of pCT image was almost the same as that of xCT image. And the error of proton CT pixel value was up to 4%. The deterioration of image quality was caused mainly by the effect of multiple Coulomb scattering. Conclusion: We designed and constructed the pCT imaging system using a thick scintillator and a CCD camera. And the system was evaluated with the experiment by use of 70-MeV proton beam. Three-dimensional pCT images of several objects were acquired by the system. This work was supported by JST SENTAN Grant Number 13A1101 and JSPS KAKENHI Grant Number 15H04912.

  17. Spiral scan long object reconstruction through PI line reconstruction

    International Nuclear Information System (INIS)

    Tam, K C; Hu, J; Sourbelle, K

    2004-01-01

    The response of a point object in a cone beam (CB) spiral scan is analysed. Based on the result, a reconstruction algorithm for long object imaging in spiral scan cone beam CT is developed. A region-of-interest (ROI) of the long object is scanned with a detector smaller than the ROI, and a portion of it can be reconstructed without contamination from overlaying materials. The top and bottom surfaces of the ROI are defined by two sets of PI lines near the two ends of the spiral path. With this novel definition of the top and bottom ROI surfaces and through the use of projective geometry, it is straightforward to partition the cone beam image into regions corresponding to projections of the ROI, the overlaying objects or both. This also simplifies computation at source positions near the spiral ends, and makes it possible to reduce radiation exposure near the spiral ends substantially through simple hardware collimation. Simulation results to validate the algorithm are presented

  18. A temporal interpolation approach for dynamic reconstruction in perfusion CT

    International Nuclear Information System (INIS)

    Montes, Pau; Lauritsch, Guenter

    2007-01-01

    This article presents a dynamic CT reconstruction algorithm for objects with time dependent attenuation coefficient. Projection data acquired over several rotations are interpreted as samples of a continuous signal. Based on this idea, a temporal interpolation approach is proposed which provides the maximum temporal resolution for a given rotational speed of the CT scanner. Interpolation is performed using polynomial splines. The algorithm can be adapted to slow signals, reducing the amount of data acquired and the computational cost. A theoretical analysis of the approximations made by the algorithm is provided. In simulation studies, the temporal interpolation approach is compared with three other dynamic reconstruction algorithms based on linear regression, linear interpolation, and generalized Parker weighting. The presented algorithm exhibits the highest temporal resolution for a given sampling interval. Hence, our approach needs less input data to achieve a certain quality in the reconstruction than the other algorithms discussed or, equivalently, less x-ray exposure and computational complexity. The proposed algorithm additionally allows the possibility of using slow rotating scanners for perfusion imaging purposes

  19. Exact reconstruction in 2D dynamic CT: compensation of time-dependent affine deformations

    International Nuclear Information System (INIS)

    Roux, Sebastien; Desbat, Laurent; Koenig, Anne; Grangeat, Pierre

    2004-01-01

    This work is dedicated to the reduction of reconstruction artefacts due to motion occurring during the acquisition of computerized tomographic projections. This problem has to be solved when imaging moving organs such as the lungs or the heart. The proposed method belongs to the class of motion compensation algorithms, where the model of motion is included in the reconstruction formula. We address two fundamental questions. First what conditions on the deformation are required for the reconstruction of the object from projections acquired sequentially during the deformation, and second how do we reconstruct the object from those projections. Here we answer these questions in the particular case of 2D general time-dependent affine deformations, assuming the motion parameters are known. We treat the problem of admissibility conditions on the deformation in the parallel-beam and fan-beam cases. Then we propose exact reconstruction methods based on rebinning or sequential FBP formulae for each of these geometries and present reconstructed images obtained with the fan-beam algorithm on simulated data

  20. Angular integration and inter-projection correlation effects in CT reconstruction

    International Nuclear Information System (INIS)

    Crawford, C.R.; Pele, N.J.

    1987-01-01

    CT reconstruction algorithms require snap-shot projections of an object. In order to minimize scan times, CT scanners rotate continuously which, in turn, prevents the acquisition of snap-shot projections. Acquired projections are integrals over angular position and may be correlated inter-projection. This paper shows that angular integration and inter-projection correlation introduce a radially dependent degradation of the spatial resolution and cause the image noise to vary non-linearly with radial position

  1. Reducing the effects of metal artefact using high keV monoenergetic reconstruction of dual energy CT (DECT) in hip replacements

    Energy Technology Data Exchange (ETDEWEB)

    Lewis, Mark [Norfolk and Norwich University Hospital, Norwich (United Kingdom); Norwich Radiology Academy, Norwich (United Kingdom); Reid, Karen [Norfolk and Norwich University Hospital, Norwich (United Kingdom); Toms, Andoni P. [Norfolk and Norwich University Hospital and University of East Anglia, Norwich (United Kingdom)

    2013-02-15

    The aim of this study was to determine whether high keV monoenergetic reconstruction of dual energy computed tomography (DECT) could be used to overcome the effects of beam hardening artefact that arise from preferential deflection of low energy photons. Two phantoms were used: a Charnley total hip replacement set in gelatine and a Catphan 500. DECT datasets were acquired at 100, 200 and 400 mA (Siemens Definition Flash, 100 and 140 kVp) and reconstructed using a standard combined algorithm (1:1) and then as monoenergetic reconstructions at 10 keV intervals from 40 to 190 keV. Semi-automated segmentation with threshold inpainting was used to obtain the attenuation values and standard deviation (SD) of the streak artefact. High contrast line pair resolution and background noise were assessed using the Catphan 500. Streak artefact is progressively reduced with increasing keV monoenergetic reconstructions. Reconstruction of a 400 mA acquisition at 150 keV results in reduction in the volume of streak artefact from 65 cm{sup 3} to 17 cm{sup 3} (74 %). There was a decrease in the contrast to noise ratio (CNR) at higher tube voltages, with the peak CNR seen at 70-80 keV. High contrast spatial resolution was maintained at high keV values. Monoenergetic reconstruction of dual energy CT at increasing theoretical kilovoltages reduces the streak artefact produced by beam hardening from orthopaedic prostheses, accompanied by a modest increase in heterogeneity of background image attenuation, and decrease in contrast to noise ratio, but no deterioration in high contrast line pair resolution. (orig.)

  2. CT reconstruction technique in lumbar intraneuroforaminal disc herniation

    International Nuclear Information System (INIS)

    Volle, E.; Claussen, C.; Kern, A.; Stoltenburg, G.

    1988-01-01

    The CT appearance of the lumbar neural foramina and contents is described in detail and compared to histopathological specimens. Direct axial scans with secondary sagittal, coronal and paraxial reconstruction series of slices of the neuralforamen were derived from lumbar spine examination of fifty normal adults. These normal parameters were then used to evaluate and subdivide 20 patients with disc herniation involving the neuralforamen. The new paraxial reformation was able to show an intraneuroforaminal disc involvement. CT-reformation technique and operative results in intraneuroforaminal disc herniation correspond in 80%. This improvement in preoperative diagnosis demonstrates to the neurosurgeon the full extent of disc herniation and results in an optimized operative approach. (orig.)

  3. CT reconstruction technique in lumbar intraneuroforaminal disc herniation

    Energy Technology Data Exchange (ETDEWEB)

    Volle, E.; Claussen, C.; Kern, A.; Stoltenburg, G.

    1988-04-01

    The CT appearance of the lumbar neural foramina and contents is described in detail and compared to histopathological specimens. Direct axial scans with secondary sagittal, coronal and paraxial reconstruction series of slices of the neuralforamen were derived from lumbar spine examination of fifty normal adults. These normal parameters were then used to evaluate and subdivide 20 patients with disc herniation involving the neuralforamen. The new paraxial reformation was able to show an intraneuroforaminal disc involvement. CT-reformation technique and operative results in intraneuroforaminal disc herniation correspond in 80%. This improvement in preoperative diagnosis demonstrates to the neurosurgeon the full extent of disc herniation and results in an optimized operative approach.

  4. Automated volume of interest delineation and rendering of cone beam CT images in interventional cardiology

    Science.gov (United States)

    Lorenz, Cristian; Schäfer, Dirk; Eshuis, Peter; Carroll, John; Grass, Michael

    2012-02-01

    Interventional C-arm systems allow the efficient acquisition of 3D cone beam CT images. They can be used for intervention planning, navigation, and outcome assessment. We present a fast and completely automated volume of interest (VOI) delineation for cardiac interventions, covering the whole visceral cavity including mediastinum and lungs but leaving out rib-cage and spine. The problem is addressed in a model based approach. The procedure has been evaluated on 22 patient cases and achieves an average surface error below 2mm. The method is able to cope with varying image intensities, varying truncations due to the limited reconstruction volume, and partially with heavy metal and motion artifacts.

  5. Benign Prostatic Hyperplasia: Cone-Beam CT in Conjunction with DSA for Identifying Prostatic Arterial Anatomy.

    Science.gov (United States)

    Wang, Mao Qiang; Duan, Feng; Yuan, Kai; Zhang, Guo Dong; Yan, Jieyu; Wang, Yan

    2017-01-01

    Purpose To describe findings in prostatic arteries (PAs) at digital subtraction angiography (DSA) and cone-beam computed tomography (CT) that allow identification of benign prostatic hyperplasia and to determine the value added with the use of cone-beam CT. Materials and Methods This retrospective single-institution study was approved by the institutional review board, and the requirement for written informed consent was waived. From February 2009 to December 2014, a total of 148 patients (mean age ± standard deviation, 70.5 years ± 14.5) underwent DSA of the internal iliac arteries and cone-beam CT with a flat-detector angiographic system before they underwent prostate artery embolization. Both the DSA and cone-beam CT images were evaluated by two interventional radiologists to determine the number of independent PAs and their origins and anastomoses with adjacent arteries. The exact McNemar test was used to compare the detection rate of the PAs and the anastomoses with DSA and with cone-beam CT. Results The PA anatomy was evaluated successfully by means of cone-beam CT in conjunction with DSA in all patients. Of the 296 pelvic sides, 274 (92.6%) had only one PA. The most frequent PA origin was the common gluteal-pudendal trunk with the superior vesicular artery in 118 (37.1%), followed by the anterior division of the internal iliac artery in 99 (31.1%), and the internal pudendal artery in 77 (24.2%) pelvic sides. In 67 (22.6%) pelvic sides, anastomoses to adjacent arteries were documented. The numbers of PA origins and anastomoses, respectively, that could be identified were significantly higher with cone-beam CT (301 of 318 [94.7%] and 65 of 67 [97.0%]) than with DSA (237 [74.5%] and 39 [58.2%], P < .05). Cone-beam CT provided essential information that was not available with DSA in 90 of 148 (60.8%) patients. Conclusion Cone-beam CT is a useful adjunctive technique to DSA for identification of the PA anatomy and provides information to help treatment planning

  6. Investigation of bulk electron densities for dose calculations on cone-beam CT images

    International Nuclear Information System (INIS)

    Lambert, J.; Parker, J.; Gupta, S.; Hatton, J.; Tang, C.; Capp, A.; Denham, J.W.; Wright, P.

    2010-01-01

    Full text: If cone-beam CT images are to be used for dose calculations, then the images must be able to provide accurate electron density information. Twelve patients underwent twice weekly cone-beam CT scans in addition to the planning CT scan. A standardised 5-field treatment plan was applied to 169 of the CBCT images. Doses were calculated using the original electron density values in the CBCT and with bulk electron densities applied. Bone was assigned a density of 288 HU, and all other tissue was assigned to be water equivalent (0 HU). The doses were compared to the dose calculated on the original planning CT image. Using the original HU values in the cone-beam images, the average dose del i vered by the plans from all 12 patients was I. I % lower than the intended 200 cOy delivered on the original CT plans (standard devia tion 0.7%, maximum difference -2.93%). When bulk electron densities were applied to the cone-beam images, the average dose was 0.3% lower than the original CT plans (standard deviation 0.8%, maximum difference -2.22%). Compared to using the original HU values, applying bulk electron densities to the CBCT images improved the dose calculations by almost I %. Some variation due to natural changes in anatomy should be expected. The application of bulk elec tron densities to cone beam CT images has the potential to improve the accuracy of dose calculations due to inaccurate H U values. Acknowledgements This work was partially funded by Cancer Council NSW Grant Number RG 07-06.

  7. Recent advances in iterative reconstruction for clinical SPECT/PET and CT.

    Science.gov (United States)

    Hutton, Brian F

    2011-08-01

    Statistical iterative reconstruction is now widely used in clinical practice and has contributed to significant improvement in image quality in recent years. Although primarily used for reconstruction in emission tomography (both single photon emission computed tomography (SPECT) and positron emission tomography (PET)) there is increasing interest in also applying similar algorithms to x-ray computed tomography (CT). There is increasing complexity in the factors that are included in the reconstruction, a demonstration of the versatility of the approach. Research continues with exploration of methods for further improving reconstruction quality with effective correction for various sources of artefact.

  8. Evaluation of a method for correction of scatter radiation in thorax cone beam CT

    International Nuclear Information System (INIS)

    Rinkel, J.; Dinten, J.M.; Esteve, F.

    2004-01-01

    Purpose: Cone beam CT (CBCT) enables three-dimensional imaging with isotropic resolution. X-ray scatter estimation is a big challenge for quantitative CBCT imaging of thorax: scatter level is significantly higher on cone beam systems compared to collimated fan beam systems. The effects of this scattered radiation are cupping artefacts, streaks, and quantification inaccuracies. The beam stops conventional scatter estimation approach can be used for CBCT but leads to a significant increase in terms of dose and acquisition time. At CEA-LETI has been developed an original scatter management process without supplementary acquisition. Methods and Materials: This Analytical Plus Indexing-based method (API) of scatter correction in CBCT is based on scatter calibration through offline acquisitions with beam stops on lucite plates, combined to an analytical transformation issued from physical equations. This approach has been applied with success in bone densitometry and mammography. To evaluate this method in CBCT, acquisitions from a thorax phantom with and without beam stops have been performed. To compare different scatter correction approaches, Feldkamp algorithm has been applied on rough data corrected from scatter by API and by beam stops approaches. Results: The API method provides results in good agreement with the beam stops array approach, suppressing cupping artefact. Otherwise influence of the scatter correction method on the noise in the reconstructed images has been evaluated. Conclusion: The results indicate that the API method is effective for quantitative CBCT imaging of thorax. Compared to a beam stops array method it needs a lower x-ray dose and shortens acquisition time. (authors)

  9. Reconstruction of brachytherapy seed positions and orientations from cone-beam CT x-ray projections via a novel iterative forward projection matching method.

    Science.gov (United States)

    Pokhrel, Damodar; Murphy, Martin J; Todor, Dorin A; Weiss, Elisabeth; Williamson, Jeffrey F

    2011-01-01

    To generalize and experimentally validate a novel algorithm for reconstructing the 3D pose (position and orientation) of implanted brachytherapy seeds from a set of a few measured 2D cone-beam CT (CBCT) x-ray projections. The iterative forward projection matching (IFPM) algorithm was generalized to reconstruct the 3D pose, as well as the centroid, of brachytherapy seeds from three to ten measured 2D projections. The gIFPM algorithm finds the set of seed poses that minimizes the sum-of-squared-difference of the pixel-by-pixel intensities between computed and measured autosegmented radiographic projections of the implant. Numerical simulations of clinically realistic brachytherapy seed configurations were performed to demonstrate the proof of principle. An in-house machined brachytherapy phantom, which supports precise specification of seed position and orientation at known values for simulated implant geometries, was used to experimentally validate this algorithm. The phantom was scanned on an ACUITY CBCT digital simulator over a full 660 sinogram projections. Three to ten x-ray images were selected from the full set of CBCT sinogram projections and postprocessed to create binary seed-only images. In the numerical simulations, seed reconstruction position and orientation errors were approximately 0.6 mm and 5 degrees, respectively. The physical phantom measurements demonstrated an absolute positional accuracy of (0.78 +/- 0.57) mm or less. The theta and phi angle errors were found to be (5.7 +/- 4.9) degrees and (6.0 +/- 4.1) degrees, respectively, or less when using three projections; with six projections, results were slightly better. The mean registration error was better than 1 mm/6 degrees compared to the measured seed projections. Each test trial converged in 10-20 iterations with computation time of 12-18 min/iteration on a 1 GHz processor. This work describes a novel, accurate, and completely automatic method for reconstructing seed orientations, as well as

  10. Reconstruction of brachytherapy seed positions and orientations from cone-beam CT x-ray projections via a novel iterative forward projection matching method

    Energy Technology Data Exchange (ETDEWEB)

    Pokhrel, Damodar; Murphy, Martin J.; Todor, Dorin A.; Weiss, Elisabeth; Williamson, Jeffrey F. [Department of Radiation Oncology, School of Medicine, Virginia Commonwealth University, Richmond, Virginia 23298 (United States)

    2011-01-15

    Purpose: To generalize and experimentally validate a novel algorithm for reconstructing the 3D pose (position and orientation) of implanted brachytherapy seeds from a set of a few measured 2D cone-beam CT (CBCT) x-ray projections. Methods: The iterative forward projection matching (IFPM) algorithm was generalized to reconstruct the 3D pose, as well as the centroid, of brachytherapy seeds from three to ten measured 2D projections. The gIFPM algorithm finds the set of seed poses that minimizes the sum-of-squared-difference of the pixel-by-pixel intensities between computed and measured autosegmented radiographic projections of the implant. Numerical simulations of clinically realistic brachytherapy seed configurations were performed to demonstrate the proof of principle. An in-house machined brachytherapy phantom, which supports precise specification of seed position and orientation at known values for simulated implant geometries, was used to experimentally validate this algorithm. The phantom was scanned on an ACUITY CBCT digital simulator over a full 660 sinogram projections. Three to ten x-ray images were selected from the full set of CBCT sinogram projections and postprocessed to create binary seed-only images. Results: In the numerical simulations, seed reconstruction position and orientation errors were approximately 0.6 mm and 5 deg., respectively. The physical phantom measurements demonstrated an absolute positional accuracy of (0.78{+-}0.57) mm or less. The {theta} and {phi} angle errors were found to be (5.7{+-}4.9) deg. and (6.0{+-}4.1) deg., respectively, or less when using three projections; with six projections, results were slightly better. The mean registration error was better than 1 mm/6 deg. compared to the measured seed projections. Each test trial converged in 10-20 iterations with computation time of 12-18 min/iteration on a 1 GHz processor. Conclusions: This work describes a novel, accurate, and completely automatic method for reconstructing

  11. A 3D microtomographic system with stacked fan-beam geometry

    International Nuclear Information System (INIS)

    Kohlbrenner, Adrian; Haemmerle, Stefan; Laib, Andres; Rueegsegger, Peter

    2000-01-01

    The move from 2D to 3D analysis, and the increase in spatial resolution characterize recent improvements in CT-based structure assessment. A new desktop micro-CT system with high scanning speed has been developed. The instrument makes use of a novel multiple fan-beam technique: radiation from a line-focus X-ray tube is divided into a stack of fan-beams by a foil collimator with a 30 μm pitch. The stacked fan-beam geometry allows to design compact CT scanners with a source-to-detector distance of only 18 cm. The complete system fits into a standard 19 in. rack. Image reconstruction is based on standard fan-beam algorithms, which eliminates the difficulties and limitations associated with cone-beam reconstruction. The detector comprises a low-noise area CCD sensor, a fiber-optic light guide and a scintillator screen. A complete examination requires 2 min only. The new micro-CT system has a voxel size of 20x20x26 μm 3 . Each 3D image contains a quarter of a billion voxels or a multiple of it. Samples up to 20 mm in diameter and up to 40 mm in length can be imaged. The instrument can be operated in a normal lab environment

  12. Modelling the Siemens SOMATOM Sensation 64 Multi-Slice CT (MSCT) Scanner

    International Nuclear Information System (INIS)

    Amin, A T Mohd; Rahni, A A Abd

    2017-01-01

    Reconstructing large volumetric 3D images with minimal radiation dosage exposure with reduced scanning time has been one of the main objectives in the advancement of CT development. One of its advancement is the introduction of multi-slice arc detector geometry from a cone-beam source in third generation scanners. In solving this complex geometry, apart from the known vast computations in CT image reconstruction due to large CT images, iterative reconstruction methods are preferred compared to analytic methods due to its flexibility in image reconstruction. A scanner of interest that has this type of geometry is the Siemens SOMATOM Sensation 64 Multi-Slice CT (MSCT) Scanner , which has a total of 32 slices with 672 detector elements on each slice. In this paper, the scanner projection is modelled via the intersecting lengths between each ray (exhibited from the source to the detector elements) with the scanned image voxels, which are evaluated using the classical Siddon’s algorithm to generate the system matrix, H . This is a prerequisite to perform various iterative reconstruction methods, which involves solving the inverse problem arising from the linear equation: S = H· I; where S is the projections produced from the image, I. Due to the ‘cone-beam geometry’ along the z -axis, the effective field-of-view (FOV) with voxel dimensions (0.4×0.4×0.4) mm 3 is 512×512×32 voxels. The scanner model is demonstrated by reconstructing an image from simulated projections using the analytic Feldkamp-Davis-Kress (FDK) method against basic iterative image reconstruction methods. (paper)

  13. Clinical Investigations of a CT-based reconstruction and 3D-Treatment planning system in interstitial brachytherapy

    Energy Technology Data Exchange (ETDEWEB)

    Kolotas, C; Zamboglou, N [Strahlenklinik, Stadtische Kliniken Offenbach, Offenbach (Germany)

    1999-12-31

    Purpose: Development, application and evaluation of a CT-guided implantation technique and a fully CT based treatment planning procedure for brachytherapy. Methods and Materials : A brachytherapy procedure based on CT-guided implantation technique and CT based treatment planning has been developed and clinically evaluated. For this purpose a software system (PROMETHEUS) for the 3D reconstruction of brachytherapy catheters and patient anatomy using only CT scans has been developed. An interface for the Nucletron Plato BPS treatment planning system for the optimisation and calculation of dose distribution has been devised. The planning target volume(s) are defined as sets of points using contouring tools and are for optimisation of the 3D dose distribution. Dose-volume histogram-based analysis of the dose distribution enables a clinically realistic evaluation of the brachytherapy application to be made. The CT-guided implantation of catheters and the CT-based treatment planning procedure has been performed for interstitial brachytherapy and for different tumour and anatomical localizations in 197 patients between 1996 and 1997. Results : The accuracy of the CT reconstruction was tested using a quality assurance phantom an an interstitial implant of 12 needles and compared with the results of reconstruction using radiographs[hs. Both methods give comparable results with regard to accuracy. The CT based reconstruction was faster. Clinical feasibility has been proven in pre-irradiated recurrences of brain tumour, in pre-treated recurrences or metastatic disease, and in breast carcinomas. The tumour volume treated ranged from 5.1 - 2741 cm3. Analysis of the implant quality showed a slight significant lower COIN value for the bone implants, but no differences in respect to the planning target volume. Conclusions : With the integration of CT imaging in the treatment planning and documentation of brachytherapy, we have a new CT based quality assurance method to evaluate

  14. Clinical Investigations of a CT-based reconstruction and 3D-Treatment planning system in interstitial brachytherapy

    International Nuclear Information System (INIS)

    Kolotas, C.; Zamboglou, N.

    1998-01-01

    Purpose: Development, application and evaluation of a CT-guided implantation technique and a fully CT based treatment planning procedure for brachytherapy. Methods and Materials : A brachytherapy procedure based on CT-guided implantation technique and CT based treatment planning has been developed and clinically evaluated. For this purpose a software system (PROMETHEUS) for the 3D reconstruction of brachytherapy catheters and patient anatomy using only CT scans has been developed. An interface for the Nucletron Plato BPS treatment planning system for the optimisation and calculation of dose distribution has been devised. The planning target volume(s) are defined as sets of points using contouring tools and are for optimisation of the 3D dose distribution. Dose-volume histogram-based analysis of the dose distribution enables a clinically realistic evaluation of the brachytherapy application to be made. The CT-guided implantation of catheters and the CT-based treatment planning procedure has been performed for interstitial brachytherapy and for different tumour and anatomical localizations in 197 patients between 1996 and 1997. Results : The accuracy of the CT reconstruction was tested using a quality assurance phantom an an interstitial implant of 12 needles and compared with the results of reconstruction using radiographs[hs. Both methods give comparable results with regard to accuracy. The CT based reconstruction was faster. Clinical feasibility has been proven in pre-irradiated recurrences of brain tumour, in pre-treated recurrences or metastatic disease, and in breast carcinomas. The tumour volume treated ranged from 5.1 - 2741 cm3. Analysis of the implant quality showed a slight significant lower COIN value for the bone implants, but no differences in respect to the planning target volume. Conclusions : With the integration of CT imaging in the treatment planning and documentation of brachytherapy, we have a new CT based quality assurance method to evaluate

  15. Image quality of iterative reconstruction in cranial CT imaging: comparison of model-based iterative reconstruction (MBIR) and adaptive statistical iterative reconstruction (ASiR).

    Science.gov (United States)

    Notohamiprodjo, S; Deak, Z; Meurer, F; Maertz, F; Mueck, F G; Geyer, L L; Wirth, S

    2015-01-01

    The purpose of this study was to compare cranial CT (CCT) image quality (IQ) of the MBIR algorithm with standard iterative reconstruction (ASiR). In this institutional review board (IRB)-approved study, raw data sets of 100 unenhanced CCT examinations (120 kV, 50-260 mAs, 20 mm collimation, 0.984 pitch) were reconstructed with both ASiR and MBIR. Signal-to-noise (SNR) and contrast-to-noise (CNR) were calculated from attenuation values measured in caudate nucleus, frontal white matter, anterior ventricle horn, fourth ventricle, and pons. Two radiologists, who were blinded to the reconstruction algorithms, evaluated anonymized multiplanar reformations of 2.5 mm with respect to depiction of different parenchymal structures and impact of artefacts on IQ with a five-point scale (0: unacceptable, 1: less than average, 2: average, 3: above average, 4: excellent). MBIR decreased artefacts more effectively than ASiR (p ASiR was 2 (p ASiR (p ASiR. As CCT is an examination that is frequently required, the use of MBIR may allow for substantial reduction of radiation exposure caused by medical diagnostics. • Model-Based iterative reconstruction (MBIR) effectively decreased artefacts in cranial CT. • MBIR reconstructed images were rated with significantly higher scores for image quality. • Model-Based iterative reconstruction may allow reduced-dose diagnostic examination protocols.

  16. A One-Step Cone-Beam CT-Enabled Planning-to-Treatment Model for Palliative Radiotherapy-From Development to Implementation

    Energy Technology Data Exchange (ETDEWEB)

    Wong, Rebecca K.S., E-mail: rebecca.wong@rmp.uhn.on.ca [Radiation Medicine Program, Princess Margaret Hospital, Toronto, Ontario (Canada); Department of Radiation Oncology, University of Toronto, Toronto, Ontario (Canada); Letourneau, Daniel; Varma, Anita [Radiation Medicine Program, Princess Margaret Hospital, Toronto, Ontario (Canada); Department of Radiation Oncology, University of Toronto, Toronto, Ontario (Canada); Bissonnette, Jean Pierre; Fitzpatrick, David; Grabarz, Daniel; Elder, Christine [Radiation Medicine Program, Princess Margaret Hospital, Toronto, Ontario (Canada); Martin, Melanie; Bezjak, Andrea [Radiation Medicine Program, Princess Margaret Hospital, Toronto, Ontario (Canada); Department of Radiation Oncology, University of Toronto, Toronto, Ontario (Canada); Panzarella, Tony [Department of Biostatistics, Princess Margaret Hospital, Toronto, Ontario (Canada); Gospodarowicz, Mary [Radiation Medicine Program, Princess Margaret Hospital, Toronto, Ontario (Canada); Department of Radiation Oncology, University of Toronto, Toronto, Ontario (Canada); Jaffray, David A. [Radiation Medicine Program, Princess Margaret Hospital, Toronto, Ontario (Canada); Department of Radiation Oncology, University of Toronto, Toronto, Ontario (Canada); Department of Medical Biophysics, University of Toronto, Toronto, Ontario (Canada)

    2012-11-01

    Purpose: To develop a cone-beam computed tomography (CT)-enabled one-step simulation-to-treatment process for the treatment of bone metastases. Methods and Materials: A three-phase prospective study was conducted. Patients requiring palliative radiotherapy to the spine, mediastinum, or abdomen/pelvis suitable for treatment with simple beam geometry ({<=}2 beams) were accrued. Phase A established the accuracy of cone-beam CT images for the purpose of gross tumor target volume (GTV) definition. Phase B evaluated the feasibility of implementing the cone-beam CT-enabled planning process at the treatment unit. Phase C evaluated the online cone-beam CT-enabled process for the planning and treatment of patients requiring radiotherapy for bone metastases. Results: Eighty-four patients participated in this study. Phase A (n = 9) established the adequacy of cone-beam CT images for target definition. Phase B (n = 45) established the quality of treatment plans to be adequate for clinical implementation for bone metastases. When the process was applied clinically in bone metastases (Phase C), the degree of overlap between planning computed tomography (PCT) and cone-beam CT for GTV and between PCT and cone-beam CT for treatment field was 82% {+-} 11% and 97% {+-} 4%, respectively. The oncologist's decision to accept the plan under a time-pressured environment remained of high quality, with the cone-beam CT-generated treatment plan delivering at least 90% of the prescribed dose to 100% {+-} 0% of the cone-beam CT planning target volume (PTV). With the assumption that the PCT PTV is the gold-standard target, the cone-beam CT-generated treatment plan delivered at least 90% and at least 95% of dose to 98% {+-} 2% and 97% {+-} 5% of the PCT PTV, respectively. The mean time for the online planning and treatment process was 32.7 {+-} 4.0 minutes. Patient satisfaction was high, with a trend for superior satisfaction with the cone-beam CT-enabled process. Conclusions: The cone-beam

  17. Proton computed tomography images with algebraic reconstruction

    Energy Technology Data Exchange (ETDEWEB)

    Bruzzi, M. [Physics and Astronomy Department, University of Florence, Florence (Italy); Civinini, C.; Scaringella, M. [INFN - Florence Division, Florence (Italy); Bonanno, D. [INFN - Catania Division, Catania (Italy); Brianzi, M. [INFN - Florence Division, Florence (Italy); Carpinelli, M. [INFN - Laboratori Nazionali del Sud, Catania (Italy); Chemistry and Pharmacy Department, University of Sassari, Sassari (Italy); Cirrone, G.A.P.; Cuttone, G. [INFN - Laboratori Nazionali del Sud, Catania (Italy); Presti, D. Lo [INFN - Catania Division, Catania (Italy); Physics and Astronomy Department, University of Catania, Catania (Italy); Maccioni, G. [INFN – Cagliari Division, Cagliari (Italy); Pallotta, S. [INFN - Florence Division, Florence (Italy); Department of Biomedical, Experimental and Clinical Sciences, University of Florence, Florence (Italy); SOD Fisica Medica, Azienda Ospedaliero-Universitaria Careggi, Firenze (Italy); Randazzo, N. [INFN - Catania Division, Catania (Italy); Romano, F. [INFN - Laboratori Nazionali del Sud, Catania (Italy); Sipala, V. [INFN - Laboratori Nazionali del Sud, Catania (Italy); Chemistry and Pharmacy Department, University of Sassari, Sassari (Italy); Talamonti, C. [INFN - Florence Division, Florence (Italy); Department of Biomedical, Experimental and Clinical Sciences, University of Florence, Florence (Italy); SOD Fisica Medica, Azienda Ospedaliero-Universitaria Careggi, Firenze (Italy); Vanzi, E. [Fisica Sanitaria, Azienda Ospedaliero-Universitaria Senese, Siena (Italy)

    2017-02-11

    A prototype of proton Computed Tomography (pCT) system for hadron-therapy has been manufactured and tested in a 175 MeV proton beam with a non-homogeneous phantom designed to simulate high-contrast material. BI-SART reconstruction algorithms have been implemented with GPU parallelism, taking into account of most likely paths of protons in matter. Reconstructed tomography images with density resolutions r.m.s. down to ~1% and spatial resolutions <1 mm, achieved within processing times of ~15′ for a 512×512 pixels image prove that this technique will be beneficial if used instead of X-CT in hadron-therapy.

  18. Clinical application of helical CT 3D reconstruction for the dental orthopaedics

    International Nuclear Information System (INIS)

    Han Benyi; Jiang Xiaolu; Li Hongru

    2005-01-01

    Objective: To evaluate the clinical application of helical CT 3D reconstruction technique in the dental orthopaedics. Methods: The helical CT was performed with 3.0 mm slice thickness and 1.0 pitch in 41 patients with dental orthopaedics. The 3D reconstructions, including maximum intensity projection (MIP), surface shaded display (SSD), and multiplanar reconstructions (MPR), were made for all the cases. Results: Thirty-seven of the 41 patients showed malalignment, tilt, rotation, overlap of the teeth and the different space between the longitudinal axes of the teeth. Twenty-five cases of them have shown 36 buried teeth in all. The axial images covered all the information. SSD demonstrated the external contours and entire morphologies of the teeth and the mandible with the relationship of the teeth alignment and the mandible. MIP clearly manifested the full view and the longitudinal alignment of the teeth. Among the 36 buried teeth, there were 29 palatally and 7 labially presented teeth, and they were morphologically delineated on MIP through various angles. Conclusion: The helical CT 3D reconstruction is a new technique to display the stereoscopic configuration of teeth. The combination of axial images and MIP, SSD, and MPR provides valuable anatomic and diagnostic information helpful for the surgeons to structure and determine the treatment protocol for the dental orthopaedics. (authors)

  19. Variability in CT lung-nodule volumetry: Effects of dose reduction and reconstruction methods.

    Science.gov (United States)

    Young, Stefano; Kim, Hyun J Grace; Ko, Moe Moe; Ko, War War; Flores, Carlos; McNitt-Gray, Michael F

    2015-05-01

    Measuring the size of nodules on chest CT is important for lung cancer staging and measuring therapy response. 3D volumetry has been proposed as a more robust alternative to 1D and 2D sizing methods. There have also been substantial advances in methods to reduce radiation dose in CT. The purpose of this work was to investigate the effect of dose reduction and reconstruction methods on variability in 3D lung-nodule volumetry. Reduced-dose CT scans were simulated by applying a noise-addition tool to the raw (sinogram) data from clinically indicated patient scans acquired on a multidetector-row CT scanner (Definition Flash, Siemens Healthcare). Scans were simulated at 25%, 10%, and 3% of the dose of their clinical protocol (CTDIvol of 20.9 mGy), corresponding to CTDIvol values of 5.2, 2.1, and 0.6 mGy. Simulated reduced-dose data were reconstructed with both conventional filtered backprojection (B45 kernel) and iterative reconstruction methods (SAFIRE: I44 strength 3 and I50 strength 3). Three lab technologist readers contoured "measurable" nodules in 33 patients under each of the different acquisition/reconstruction conditions in a blinded study design. Of the 33 measurable nodules, 17 were used to estimate repeatability with their clinical reference protocol, as well as interdose and inter-reconstruction-method reproducibilities. The authors compared the resulting distributions of proportional differences across dose and reconstruction methods by analyzing their means, standard deviations (SDs), and t-test and F-test results. The clinical-dose repeatability experiment yielded a mean proportional difference of 1.1% and SD of 5.5%. The interdose reproducibility experiments gave mean differences ranging from -5.6% to -1.7% and SDs ranging from 6.3% to 9.9%. The inter-reconstruction-method reproducibility experiments gave mean differences of 2.0% (I44 strength 3) and -0.3% (I50 strength 3), and SDs were identical at 7.3%. For the subset of repeatability cases, inter-reconstruction

  20. Image quality in thoracic 4D cone-beam CT: A sensitivity analysis of respiratory signal, binning method, reconstruction algorithm, and projection angular spacing

    International Nuclear Information System (INIS)

    Shieh, Chun-Chien; Kipritidis, John; O’Brien, Ricky T.; Keall, Paul J.; Kuncic, Zdenka

    2014-01-01

    Purpose: Respiratory signal, binning method, and reconstruction algorithm are three major controllable factors affecting image quality in thoracic 4D cone-beam CT (4D-CBCT), which is widely used in image guided radiotherapy (IGRT). Previous studies have investigated each of these factors individually, but no integrated sensitivity analysis has been performed. In addition, projection angular spacing is also a key factor in reconstruction, but how it affects image quality is not obvious. An investigation of the impacts of these four factors on image quality can help determine the most effective strategy in improving 4D-CBCT for IGRT. Methods: Fourteen 4D-CBCT patient projection datasets with various respiratory motion features were reconstructed with the following controllable factors: (i) respiratory signal (real-time position management, projection image intensity analysis, or fiducial marker tracking), (ii) binning method (phase, displacement, or equal-projection-density displacement binning), and (iii) reconstruction algorithm [Feldkamp–Davis–Kress (FDK), McKinnon–Bates (MKB), or adaptive-steepest-descent projection-onto-convex-sets (ASD-POCS)]. The image quality was quantified using signal-to-noise ratio (SNR), contrast-to-noise ratio, and edge-response width in order to assess noise/streaking and blur. The SNR values were also analyzed with respect to the maximum, mean, and root-mean-squared-error (RMSE) projection angular spacing to investigate how projection angular spacing affects image quality. Results: The choice of respiratory signals was found to have no significant impact on image quality. Displacement-based binning was found to be less prone to motion artifacts compared to phase binning in more than half of the cases, but was shown to suffer from large interbin image quality variation and large projection angular gaps. Both MKB and ASD-POCS resulted in noticeably improved image quality almost 100% of the time relative to FDK. In addition, SNR

  1. Image quality in thoracic 4D cone-beam CT: A sensitivity analysis of respiratory signal, binning method, reconstruction algorithm, and projection angular spacing

    Energy Technology Data Exchange (ETDEWEB)

    Shieh, Chun-Chien [Radiation Physics Laboratory, Sydney Medical School, University of Sydney, NSW 2006, Australia and Institute of Medical Physics, School of Physics, University of Sydney, NSW 2006 (Australia); Kipritidis, John; O’Brien, Ricky T.; Keall, Paul J., E-mail: paul.keall@sydney.edu.au [Radiation Physics Laboratory, Sydney Medical School, University of Sydney, NSW 2006 (Australia); Kuncic, Zdenka [Institute of Medical Physics, School of Physics, University of Sydney, NSW 2006 (Australia)

    2014-04-15

    Purpose: Respiratory signal, binning method, and reconstruction algorithm are three major controllable factors affecting image quality in thoracic 4D cone-beam CT (4D-CBCT), which is widely used in image guided radiotherapy (IGRT). Previous studies have investigated each of these factors individually, but no integrated sensitivity analysis has been performed. In addition, projection angular spacing is also a key factor in reconstruction, but how it affects image quality is not obvious. An investigation of the impacts of these four factors on image quality can help determine the most effective strategy in improving 4D-CBCT for IGRT. Methods: Fourteen 4D-CBCT patient projection datasets with various respiratory motion features were reconstructed with the following controllable factors: (i) respiratory signal (real-time position management, projection image intensity analysis, or fiducial marker tracking), (ii) binning method (phase, displacement, or equal-projection-density displacement binning), and (iii) reconstruction algorithm [Feldkamp–Davis–Kress (FDK), McKinnon–Bates (MKB), or adaptive-steepest-descent projection-onto-convex-sets (ASD-POCS)]. The image quality was quantified using signal-to-noise ratio (SNR), contrast-to-noise ratio, and edge-response width in order to assess noise/streaking and blur. The SNR values were also analyzed with respect to the maximum, mean, and root-mean-squared-error (RMSE) projection angular spacing to investigate how projection angular spacing affects image quality. Results: The choice of respiratory signals was found to have no significant impact on image quality. Displacement-based binning was found to be less prone to motion artifacts compared to phase binning in more than half of the cases, but was shown to suffer from large interbin image quality variation and large projection angular gaps. Both MKB and ASD-POCS resulted in noticeably improved image quality almost 100% of the time relative to FDK. In addition, SNR

  2. Clinical application of 16-slice spiral CT in reconstruction imaging of coronary artery for diagnosing coronary disense

    International Nuclear Information System (INIS)

    Mao Xinbo; Zhu Xinjin; Zeng Huiliang; Chen Xueguang

    2005-01-01

    Objective: An evaluation of the reconstructed imaging of coronary arteries with 16-slice spiral CT in diagnosis of coronary disease. Methods: The reconstructed images of coronary arteries obtained on a 16-slice spiral CT scanner were reviewed in 60 cases, on which the following techniques were applied: retrospective ECG-gating, Segment method with 75% R-R interval, volume rendering technique (VRT), maximum intensity projection (MIP), mulfiplanar reconstruction (MPR), curved planar reconstruction (CPR) and CT virtual endoscopy (CTVE). Results: In all 60 cases, different stages of CHD were revealed in 21 cases; none abnormality was found in 33; and images were in poor quality in 2 cases, which was available for diagnosis. There were 4 stents planted in 4 cases: soft plaque suspected in lcase, patent in 2 and occlude in 1. Conclusion: The reconstructed imaging of coronary arteries with 16-slice spiral CT is superior modality in evaluation of severe coronary stenosis, plaques, and the pantency of the intra-luminal stents, which is an efficient and non-invasive imaging in diagnosis of early-stage CHD and screening in high risk population. (authors)

  3. Limiting CT radiation dose in children with craniosynostosis: phantom study using model-based iterative reconstruction

    Energy Technology Data Exchange (ETDEWEB)

    Kaasalainen, Touko; Lampinen, Anniina [University of Helsinki and Helsinki University Hospital, HUS Medical Imaging Center, Radiology, POB 340, Helsinki (Finland); University of Helsinki, Department of Physics, Helsinki (Finland); Palmu, Kirsi [University of Helsinki and Helsinki University Hospital, HUS Medical Imaging Center, Radiology, POB 340, Helsinki (Finland); School of Science, Aalto University, Department of Biomedical Engineering and Computational Science, Helsinki (Finland); Reijonen, Vappu; Kortesniemi, Mika [University of Helsinki and Helsinki University Hospital, HUS Medical Imaging Center, Radiology, POB 340, Helsinki (Finland); Leikola, Junnu [University of Helsinki and Helsinki University Hospital, Department of Plastic Surgery, Helsinki (Finland); Kivisaari, Riku [University of Helsinki and Helsinki University Hospital, Department of Neurosurgery, Helsinki (Finland)

    2015-09-15

    Medical professionals need to exercise particular caution when developing CT scanning protocols for children who require multiple CT studies, such as those with craniosynostosis. To evaluate the utility of ultra-low-dose CT protocols with model-based iterative reconstruction techniques for craniosynostosis imaging. We scanned two pediatric anthropomorphic phantoms with a 64-slice CT scanner using different low-dose protocols for craniosynostosis. We measured organ doses in the head region with metal-oxide-semiconductor field-effect transistor (MOSFET) dosimeters. Numerical simulations served to estimate organ and effective doses. We objectively and subjectively evaluated the quality of images produced by adaptive statistical iterative reconstruction (ASiR) 30%, ASiR 50% and Veo (all by GE Healthcare, Waukesha, WI). Image noise and contrast were determined for different tissues. Mean organ dose with the newborn phantom was decreased up to 83% compared to the routine protocol when using ultra-low-dose scanning settings. Similarly, for the 5-year phantom the greatest radiation dose reduction was 88%. The numerical simulations supported the findings with MOSFET measurements. The image quality remained adequate with Veo reconstruction, even at the lowest dose level. Craniosynostosis CT with model-based iterative reconstruction could be performed with a 20-μSv effective dose, corresponding to the radiation exposure of plain skull radiography, without compromising required image quality. (orig.)

  4. A general exact method for synthesizing parallel-beam projections from cone-beam projections via filtered backprojection

    International Nuclear Information System (INIS)

    Li Liang; Chen Zhiqiang; Xing Yuxiang; Zhang Li; Kang Kejun; Wang Ge

    2006-01-01

    In recent years, image reconstruction methods for cone-beam computed tomography (CT) have been extensively studied. However, few of these studies discussed computing parallel-beam projections from cone-beam projections. In this paper, we focus on the exact synthesis of complete or incomplete parallel-beam projections from cone-beam projections. First, an extended central slice theorem is described to establish a relationship between the Radon space and the Fourier space. Then, data sufficiency conditions are proposed for computing parallel-beam projection data from cone-beam data. Using these results, a general filtered backprojection algorithm is formulated that can exactly synthesize parallel-beam projection data from cone-beam projection data. As an example, we prove that parallel-beam projections can be exactly synthesized in an angular range in the case of circular cone-beam scanning. Interestingly, this angular range is larger than that derived in the Feldkamp reconstruction framework. Numerical experiments are performed in the circular scanning case to verify our method

  5. Coronary CT angiography: Comparison of a novel iterative reconstruction with filtered back projection for reconstruction of low-dose CT—Initial experience

    International Nuclear Information System (INIS)

    Takx, Richard A.P.; Schoepf, U. Joseph; Moscariello, Antonio; Das, Marco; Rowe, Garrett; Schoenberg, Stefan O.; Fink, Christian; Henzler, Thomas

    2013-01-01

    Objective: To prospectively compare subjective and objective image quality in 20% tube current coronary CT angiography (cCTA) datasets between an iterative reconstruction algorithm (SAFIRE) and traditional filtered back projection (FBP). Materials and methods: Twenty patients underwent a prospectively ECG-triggered dual-step cCTA protocol using 2nd generation dual-source CT (DSCT). CT raw data was reconstructed using standard FBP at full-dose (Group 1 a) and 80% tube current reduced low-dose (Group 1 b). The low-dose raw data was additionally reconstructed using iterative raw data reconstruction (Group 2 ). Attenuation and image noise were measured in three regions of interest and signal-to-noise-ratio (SNR) as well as contrast-to-noise-ratio (CNR) was calculated. Subjective diagnostic image quality was evaluated using a 4-point Likert scale. Results: Mean image noise of group 2 was lowered by 22% on average when compared to group 1 b (p 2 compared to group 1 b (p 2 (1.88 ± 0.63) was also rated significantly higher when compared to group 1 b (1.58 ± 0.63, p = 0.004). Conclusions: Image quality of 80% tube current reduced iteratively reconstructed cCTA raw data is significantly improved when compared to standard FBP and consequently may improve the diagnostic accuracy of cCTA

  6. Development of digital reconstructed radiography software at new treatment facility for carbon-ion beam scanning of National Institute of Radiological Sciences.

    Science.gov (United States)

    Mori, Shinichiro; Inaniwa, Taku; Kumagai, Motoki; Kuwae, Tsunekazu; Matsuzaki, Yuka; Furukawa, Takuji; Shirai, Toshiyuki; Noda, Koji

    2012-06-01

    To increase the accuracy of carbon ion beam scanning therapy, we have developed a graphical user interface-based digitally-reconstructed radiograph (DRR) software system for use in routine clinical practice at our center. The DRR software is used in particular scenarios in the new treatment facility to achieve the same level of geometrical accuracy at the treatment as at the imaging session. DRR calculation is implemented simply as the summation of CT image voxel values along the X-ray projection ray. Since we implemented graphics processing unit-based computation, the DRR images are calculated with a speed sufficient for the particular clinical practice requirements. Since high spatial resolution flat panel detector (FPD) images should be registered to the reference DRR images in patient setup process in any scenarios, the DRR images also needs higher spatial resolution close to that of FPD images. To overcome the limitation of the CT spatial resolution imposed by the CT voxel size, we applied image processing to improve the calculated DRR spatial resolution. The DRR software introduced here enabled patient positioning with sufficient accuracy for the implementation of carbon-ion beam scanning therapy at our center.

  7. Technological features and clinical feasibility of megavoltage CT scanning

    International Nuclear Information System (INIS)

    Nakagawa, Keiichi; Aoki, Yukimasa; Akanuma, Atsuo; Sakata, Kouichi; Karasawa, Katsuyuki; Terahara, Atsurou; Onogi, Yuzou; Hasezawa, Kenji; Sasaki, Yasuhito

    1992-01-01

    Megavoltage CT scanning using 4-MV and 6-MV radiotherapy beams has been developed and applied to verify errors in patient positioning. A detector system composed of 120 pairs of cadmium tungstate scintillators with photodiodes is mounted to the treatment unit at a distance of 160 cm from the beam source. Image reconstruction is performed with a standard filtered back-projection algorithm. Scanning time and reconstruction time for a slice is approximately 35 s and 60 s respectively. Although spatial resolution is as large as 4 mm, it has sufficient image quality to be applied for treatment planning and verification. The delivered dose with 4 MV and 6 MV is about 1.4 cGy and 2.8 cGy respectively. When a megavoltage CT image is taken in treatment position, the positioning errors are easily detected by comparing it with diagnostic CT sections for treatment planning. Several clinical examples are presented. (orig.)

  8. Low dose dynamic CT myocardial perfusion imaging using a statistical iterative reconstruction method

    Energy Technology Data Exchange (ETDEWEB)

    Tao, Yinghua [Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin 53705 (United States); Chen, Guang-Hong [Department of Medical Physics and Department of Radiology, University of Wisconsin-Madison, Madison, Wisconsin 53705 (United States); Hacker, Timothy A.; Raval, Amish N. [Department of Medicine, University of Wisconsin-Madison, Madison, Wisconsin 53792 (United States); Van Lysel, Michael S.; Speidel, Michael A., E-mail: speidel@wisc.edu [Department of Medical Physics and Department of Medicine, University of Wisconsin-Madison, Madison, Wisconsin 53705 (United States)

    2014-07-15

    Purpose: Dynamic CT myocardial perfusion imaging has the potential to provide both functional and anatomical information regarding coronary artery stenosis. However, radiation dose can be potentially high due to repeated scanning of the same region. The purpose of this study is to investigate the use of statistical iterative reconstruction to improve parametric maps of myocardial perfusion derived from a low tube current dynamic CT acquisition. Methods: Four pigs underwent high (500 mA) and low (25 mA) dose dynamic CT myocardial perfusion scans with and without coronary occlusion. To delineate the affected myocardial territory, an N-13 ammonia PET perfusion scan was performed for each animal in each occlusion state. Filtered backprojection (FBP) reconstruction was first applied to all CT data sets. Then, a statistical iterative reconstruction (SIR) method was applied to data sets acquired at low dose. Image voxel noise was matched between the low dose SIR and high dose FBP reconstructions. CT perfusion maps were compared among the low dose FBP, low dose SIR and high dose FBP reconstructions. Numerical simulations of a dynamic CT scan at high and low dose (20:1 ratio) were performed to quantitatively evaluate SIR and FBP performance in terms of flow map accuracy, precision, dose efficiency, and spatial resolution. Results: Forin vivo studies, the 500 mA FBP maps gave −88.4%, −96.0%, −76.7%, and −65.8% flow change in the occluded anterior region compared to the open-coronary scans (four animals). The percent changes in the 25 mA SIR maps were in good agreement, measuring −94.7%, −81.6%, −84.0%, and −72.2%. The 25 mA FBP maps gave unreliable flow measurements due to streaks caused by photon starvation (percent changes of +137.4%, +71.0%, −11.8%, and −3.5%). Agreement between 25 mA SIR and 500 mA FBP global flow was −9.7%, 8.8%, −3.1%, and 26.4%. The average variability of flow measurements in a nonoccluded region was 16.3%, 24.1%, and 937

  9. Low dose dynamic CT myocardial perfusion imaging using a statistical iterative reconstruction method

    International Nuclear Information System (INIS)

    Tao, Yinghua; Chen, Guang-Hong; Hacker, Timothy A.; Raval, Amish N.; Van Lysel, Michael S.; Speidel, Michael A.

    2014-01-01

    Purpose: Dynamic CT myocardial perfusion imaging has the potential to provide both functional and anatomical information regarding coronary artery stenosis. However, radiation dose can be potentially high due to repeated scanning of the same region. The purpose of this study is to investigate the use of statistical iterative reconstruction to improve parametric maps of myocardial perfusion derived from a low tube current dynamic CT acquisition. Methods: Four pigs underwent high (500 mA) and low (25 mA) dose dynamic CT myocardial perfusion scans with and without coronary occlusion. To delineate the affected myocardial territory, an N-13 ammonia PET perfusion scan was performed for each animal in each occlusion state. Filtered backprojection (FBP) reconstruction was first applied to all CT data sets. Then, a statistical iterative reconstruction (SIR) method was applied to data sets acquired at low dose. Image voxel noise was matched between the low dose SIR and high dose FBP reconstructions. CT perfusion maps were compared among the low dose FBP, low dose SIR and high dose FBP reconstructions. Numerical simulations of a dynamic CT scan at high and low dose (20:1 ratio) were performed to quantitatively evaluate SIR and FBP performance in terms of flow map accuracy, precision, dose efficiency, and spatial resolution. Results: Forin vivo studies, the 500 mA FBP maps gave −88.4%, −96.0%, −76.7%, and −65.8% flow change in the occluded anterior region compared to the open-coronary scans (four animals). The percent changes in the 25 mA SIR maps were in good agreement, measuring −94.7%, −81.6%, −84.0%, and −72.2%. The 25 mA FBP maps gave unreliable flow measurements due to streaks caused by photon starvation (percent changes of +137.4%, +71.0%, −11.8%, and −3.5%). Agreement between 25 mA SIR and 500 mA FBP global flow was −9.7%, 8.8%, −3.1%, and 26.4%. The average variability of flow measurements in a nonoccluded region was 16.3%, 24.1%, and 937

  10. Low dose CT reconstruction via L1 norm dictionary learning using alternating minimization algorithm and balancing principle.

    Science.gov (United States)

    Wu, Junfeng; Dai, Fang; Hu, Gang; Mou, Xuanqin

    2018-04-18

    Excessive radiation exposure in computed tomography (CT) scans increases the chance of developing cancer and has become a major clinical concern. Recently, statistical iterative reconstruction (SIR) with l0-norm dictionary learning regularization has been developed to reconstruct CT images from the low dose and few-view dataset in order to reduce radiation dose. Nonetheless, the sparse regularization term adopted in this approach is l0-norm, which cannot guarantee the global convergence of the proposed algorithm. To address this problem, in this study we introduced the l1-norm dictionary learning penalty into SIR framework for low dose CT image reconstruction, and developed an alternating minimization algorithm to minimize the associated objective function, which transforms CT image reconstruction problem into a sparse coding subproblem and an image updating subproblem. During the image updating process, an efficient model function approach based on balancing principle is applied to choose the regularization parameters. The proposed alternating minimization algorithm was evaluated first using real projection data of a sheep lung CT perfusion and then using numerical simulation based on sheep lung CT image and chest image. Both visual assessment and quantitative comparison using terms of root mean square error (RMSE) and structural similarity (SSIM) index demonstrated that the new image reconstruction algorithm yielded similar performance with l0-norm dictionary learning penalty and outperformed the conventional filtered backprojection (FBP) and total variation (TV) minimization algorithms.

  11. A unified analysis of FBP-based algorithms in helical cone-beam and circular cone- and fan-beam scans

    International Nuclear Information System (INIS)

    Pan Xiaochuan; Xia Dan; Zou Yu; Yu Lifeng

    2004-01-01

    A circular scanning trajectory is and will likely remain a popular choice of trajectory in computed tomography (CT) imaging because it is easy to implement and control. Filtered-backprojection (FBP)-based algorithms have been developed previously for approximate and exact reconstruction of the entire image or a region of interest within the image in circular cone-beam and fan-beam cases. Recently, we have developed a 3D FBP-based algorithm for image reconstruction on PI-line segments in a helical cone-beam scan. In this work, we demonstrated that the 3D FBP-based algorithm indeed provided a rather general formulation for image reconstruction from divergent projections (such as cone-beam and fan-beam projections). On the basis of this formulation we derived new approximate or exact algorithms for image reconstruction in circular cone-beam or fan-beam scans, which can be interpreted as special cases of the helical scan. Existing algorithms corresponding to the derived algorithms were identified. We also performed a preliminary numerical study to verify our theoretical results in each of the cases. The results in the work can readily be generalized to other non-circular trajectories

  12. Fast GPU-based Monte Carlo code for SPECT/CT reconstructions generates improved 177Lu images.

    Science.gov (United States)

    Rydén, T; Heydorn Lagerlöf, J; Hemmingsson, J; Marin, I; Svensson, J; Båth, M; Gjertsson, P; Bernhardt, P

    2018-01-04

    Full Monte Carlo (MC)-based SPECT reconstructions have a strong potential for correcting for image degrading factors, but the reconstruction times are long. The objective of this study was to develop a highly parallel Monte Carlo code for fast, ordered subset expectation maximum (OSEM) reconstructions of SPECT/CT images. The MC code was written in the Compute Unified Device Architecture language for a computer with four graphics processing units (GPUs) (GeForce GTX Titan X, Nvidia, USA). This enabled simulations of parallel photon emissions from the voxels matrix (128 3 or 256 3 ). Each computed tomography (CT) number was converted to attenuation coefficients for photo absorption, coherent scattering, and incoherent scattering. For photon scattering, the deflection angle was determined by the differential scattering cross sections. An angular response function was developed and used to model the accepted angles for photon interaction with the crystal, and a detector scattering kernel was used for modeling the photon scattering in the detector. Predefined energy and spatial resolution kernels for the crystal were used. The MC code was implemented in the OSEM reconstruction of clinical and phantom 177 Lu SPECT/CT images. The Jaszczak image quality phantom was used to evaluate the performance of the MC reconstruction in comparison with attenuated corrected (AC) OSEM reconstructions and attenuated corrected OSEM reconstructions with resolution recovery corrections (RRC). The performance of the MC code was 3200 million photons/s. The required number of photons emitted per voxel to obtain a sufficiently low noise level in the simulated image was 200 for a 128 3 voxel matrix. With this number of emitted photons/voxel, the MC-based OSEM reconstruction with ten subsets was performed within 20 s/iteration. The images converged after around six iterations. Therefore, the reconstruction time was around 3 min. The activity recovery for the spheres in the Jaszczak phantom was

  13. Correlation of conventional simulation x-ray films and CT images for HDR-brachytherapy catheters reconstruction

    International Nuclear Information System (INIS)

    Rajendran, M.; Reddy, K.D.; Reddy, R.M.; Reddy, J.M.; Reddy, B.V.N.; Kiran Kumar; Gopi, S.; Dharaniraj; Janardhanan

    2002-01-01

    In order to plan a brachytherapy implant, it is imperative that implant reconstruction is done accurately. The purpose of this paper is to evaluate whether implant reconstruction done with transverse CT images is comparable to reconstruction done with conventional x-ray films

  14. Cone beam CT findings of retromolar canals: Report of cases and literature review

    Energy Technology Data Exchange (ETDEWEB)

    Han, Sang Sun [Dept. of Dental Hygiene, Eulji University, Seongnam (Korea, Republic of); Park, Chang Seo [Dept. of Oral and Maxillofacial Radiology, College of Dentistry, Yonsei University, Seoul (Korea, Republic of)

    2013-12-15

    A retromolar canal is an anatomical variation in the mandible. As it includes the neurovascular bundle, local anesthetic insufficiency can occur, and an injury of the retromolar canal during dental surgery in the mandible may result in excessive bleeding, paresthesia, and traumatic neuroma. Using imaging analysis software, we evaluated the cone-beam computed tomography (CT) images of two Korean patients who presented with retromolar canals. Retromolar canals were detectable on the sagittal and cross-sectional images of cone-beam CT, but not on the panoramic radiographs of the patients. Therefore, the clinician should pay particular attention to the identification of retromolar canals by preoperative radiographic examination, and additional cone beam CT scanning would be recommended.

  15. Cone beam CT findings of retromolar canals: Report of cases and literature review

    International Nuclear Information System (INIS)

    Han, Sang Sun; Park, Chang Seo

    2013-01-01

    A retromolar canal is an anatomical variation in the mandible. As it includes the neurovascular bundle, local anesthetic insufficiency can occur, and an injury of the retromolar canal during dental surgery in the mandible may result in excessive bleeding, paresthesia, and traumatic neuroma. Using imaging analysis software, we evaluated the cone-beam computed tomography (CT) images of two Korean patients who presented with retromolar canals. Retromolar canals were detectable on the sagittal and cross-sectional images of cone-beam CT, but not on the panoramic radiographs of the patients. Therefore, the clinician should pay particular attention to the identification of retromolar canals by preoperative radiographic examination, and additional cone beam CT scanning would be recommended.

  16. Improving the accuracy of CT dimensional metrology by a novel beam hardening correction method

    International Nuclear Information System (INIS)

    Zhang, Xiang; Li, Lei; Zhang, Feng; Xi, Xiaoqi; Deng, Lin; Yan, Bin

    2015-01-01

    Its powerful nondestructive characteristics are attracting more and more research into the study of computed tomography (CT) for dimensional metrology, which offers a practical alternative to the common measurement methods. However, the inaccuracy and uncertainty severely limit the further utilization of CT for dimensional metrology due to many factors, among which the beam hardening (BH) effect plays a vital role. This paper mainly focuses on eliminating the influence of the BH effect in the accuracy of CT dimensional metrology. To correct the BH effect, a novel exponential correction model is proposed. The parameters of the model are determined by minimizing the gray entropy of the reconstructed volume. In order to maintain the consistency and contrast of the corrected volume, a punishment term is added to the cost function, enabling more accurate measurement results to be obtained by the simple global threshold method. The proposed method is efficient, and especially suited to the case where there is a large difference in gray value between material and background. Different spheres with known diameters are used to verify the accuracy of dimensional measurement. Both simulation and real experimental results demonstrate the improvement in measurement precision. Moreover, a more complex workpiece is also tested to show that the proposed method is of general feasibility. (paper)

  17. CT-based virtual tracheobronchoscopy in children - comparison with axial CT and multiplanar reconstruction: preliminary results

    International Nuclear Information System (INIS)

    Sorantin, Erich; Lindbichler, Franz; Eber, Ernst; Schimpl, Guenther

    2002-01-01

    Background: 3D post-processing of spiral-CT (S-CT) data using perspective projection allows the generation of virtual views similar to endoscopy. Objective: To evaluate whether simultaneous reading of axial S-CT, multiplanar reconstruction (MPR) and virtual tracheobronchoscopy (VTB) is more precise and accurate than reading of axial S-CT and MPR alone in paediatric patients. Materials and methods: S-CT studies of 15 symptomatic and 4 normal patients were investigated. Two radiologists independently read two sets of images for airway abnormalities: first axial CT and MPR, followed by axial CT, MPR and VTB. A final decision was later made by consensus. All results were compared to fibre-optic bronchoscopy (FTB). Interobserver agreement was used as an indicator of precision for the display technique used. Results: At reading of axial S-CT and MPR an interobserver agreement of 89.5% (κ=0.776, P<0.00103) was found. Based on the consensus decision, a diagnostic accuracy of 89.5% at a sensitivity 86.6% and specificity of 100% (κ=0.776, 95% CI 0.491-1.062, P<0.00103) was achieved. At reporting on axial S-CT, MPR and VTB, all cases were classified correctly by both readers, indicating 100% accuracy, interobserver agreement, sensitivity and specificity (κ=1.00, 95% CI 1.0-1.0, P<0.000258). Conclusions: The simultaneous display of axial S-CT, MPR and VTB raises the precision, accuracy and sensitivity of radiological reports. (orig.)

  18. Scattering calculation and image reconstruction using elevation-focused beams.

    Science.gov (United States)

    Duncan, David P; Astheimer, Jeffrey P; Waag, Robert C

    2009-05-01

    Pressure scattered by cylindrical and spherical objects with elevation-focused illumination and reception has been analytically calculated, and corresponding cross sections have been reconstructed with a two-dimensional algorithm. Elevation focusing was used to elucidate constraints on quantitative imaging of three-dimensional objects with two-dimensional algorithms. Focused illumination and reception are represented by angular spectra of plane waves that were efficiently computed using a Fourier interpolation method to maintain the same angles for all temporal frequencies. Reconstructions were formed using an eigenfunction method with multiple frequencies, phase compensation, and iteration. The results show that the scattered pressure reduces to a two-dimensional expression, and two-dimensional algorithms are applicable when the region of a three-dimensional object within an elevation-focused beam is approximately constant in elevation. The results also show that energy scattered out of the reception aperture by objects contained within the focused beam can result in the reconstructed values of attenuation slope being greater than true values at the boundary of the object. Reconstructed sound speed images, however, appear to be relatively unaffected by the loss in scattered energy. The broad conclusion that can be drawn from these results is that two-dimensional reconstructions require compensation to account for uncaptured three-dimensional scattering.

  19. CT Imaging of facial trauma. The role of different types of reconstruction. Part II - soft tissues

    International Nuclear Information System (INIS)

    Myga-Porosilo, J.; Sraga, W.; Borowiak, H.; Jackowska, Z.; Kluczewska, E.; Skrzelewski, S.

    2011-01-01

    Background: Injury to facial soft tissues as a complication of skeleton fractures is an important problem among patients with facial trauma. The aim of this work was to assess the value of multiplanar and three-dimensional (3D) reconstruction computed tomography (CT) images obtained by using multi-detector row technology in spiral data acquisition in patients with facial injuries of soft tissue. Material/Methods: Sixty-seven patients diagnosed with injury to the facial skeleton underwent a CT scan with the use of GE Hispeed Qx/i scanner. For each patient: a two-dimensional (2D) multiplanar reconstruction (MPR), maximum intensity projection (MIP), and 3D volume rendering (VR) were conducted. Post-injury lesions of soft tissues were assessed. During the assessment of the post-injury lesions of soft tissues, the following features were evaluated: Extra ocular muscle and fat tissue herniation through fractures in the medial and inferior orbital walls. Fluid in the sinuses and in the nasal cavity. Subcutaneous tissue emphysema. Results: For subcutaneous emphysema and sinus fluid imaging, both the axial and the 2D image reconstruction proved comparably effective. However, 2D reconstructions were superior to transverse plane images with regard to herniations into fractures of the inferior orbital wall. 3D reconstruction has no importance in diagnosing soft tissue injuries. Conclusions: Multiplanar CT reconstructions increase the effectiveness of imaging of orbital tissue herniations, especially in case of fractures in the inferior orbital wall. In suspected soft tissue herniations, as well as prior to surgical treatment, spiral CT with 2D multiplanar reconstructions should be the method of choice. (authors)

  20. Influence of model based iterative reconstruction algorithm on image quality of multiplanar reformations in reduced dose chest CT

    International Nuclear Information System (INIS)

    Barras, Heloise; Dunet, Vincent; Hachulla, Anne-Lise; Grimm, Jochen; Beigelman-Aubry, Catherine

    2016-01-01

    Model-based iterative reconstruction (MBIR) reduces image noise and improves image quality (IQ) but its influence on post-processing tools including maximal intensity projection (MIP) and minimal intensity projection (mIP) remains unknown. To evaluate the influence on IQ of MBIR on native, mIP, MIP axial and coronal reformats of reduced dose computed tomography (RD-CT) chest acquisition. Raw data of 50 patients, who underwent a standard dose CT (SD-CT) and a follow-up RD-CT with a CT dose index (CTDI) of 2–3 mGy, were reconstructed by MBIR and FBP. Native slices, 4-mm-thick MIP, and 3-mm-thick mIP axial and coronal reformats were generated. The relative IQ, subjective IQ, image noise, and number of artifacts were determined in order to compare different reconstructions of RD-CT with reference SD-CT. The lowest noise was observed with MBIR. RD-CT reconstructed by MBIR exhibited the best relative and subjective IQ on coronal view regardless of the post-processing tool. MBIR generated the lowest rate of artefacts on coronal mIP/MIP reformats and the highest one on axial reformats, mainly represented by distortions and stairsteps artifacts. The MBIR algorithm reduces image noise but generates more artifacts than FBP on axial mIP and MIP reformats of RD-CT. Conversely, it significantly improves IQ on coronal views, without increasing artifacts, regardless of the post-processing technique

  1. An FDK-like cone-beam SPECT reconstruction algorithm for non-uniform attenuated projections acquired using a circular trajectory

    International Nuclear Information System (INIS)

    Huang, Q; Zeng, G L; You, J; Gullberg, G T

    2005-01-01

    In this paper, Novikov's inversion formula of the attenuated two-dimensional (2D) Radon transform is applied to the reconstruction of attenuated fan-beam projections acquired with equal detector spacing and of attenuated cone-beam projections acquired with a flat planar detector and circular trajectory. The derivation of the fan-beam algorithm is obtained by transformation from parallel-beam coordinates to fan-beam coordinates. The cone-beam reconstruction algorithm is an extension of the fan-beam reconstruction algorithm using Feldkamp-Davis-Kress's (FDK) method. Computer simulations indicate that the algorithm is efficient and is accurate in reconstructing slices close to the central slice of the cone-beam orbit plane. When the attenuation map is set to zero the implementation is equivalent to the FDK method. Reconstructed images are also shown for noise corrupted projections

  2. Super-resolution reconstruction of 4D-CT lung data via patch-based low-rank matrix reconstruction

    Science.gov (United States)

    Fang, Shiting; Wang, Huafeng; Liu, Yueliang; Zhang, Minghui; Yang, Wei; Feng, Qianjin; Chen, Wufan; Zhang, Yu

    2017-10-01

    Lung 4D computed tomography (4D-CT), which is a time-resolved CT data acquisition, performs an important role in explicitly including respiratory motion in treatment planning and delivery. However, the radiation dose is usually reduced at the expense of inter-slice spatial resolution to minimize radiation-related health risk. Therefore, resolution enhancement along the superior-inferior direction is necessary. In this paper, a super-resolution (SR) reconstruction method based on a patch low-rank matrix reconstruction is proposed to improve the resolution of lung 4D-CT images. Specifically, a low-rank matrix related to every patch is constructed by using a patch searching strategy. Thereafter, the singular value shrinkage is employed to recover the high-resolution patch under the constraints of the image degradation model. The output high-resolution patches are finally assembled to output the entire image. This method is extensively evaluated using two public data sets. Quantitative analysis shows that the proposed algorithm decreases the root mean square error by 9.7%-33.4% and the edge width by 11.4%-24.3%, relative to linear interpolation, back projection (BP) and Zhang et al’s algorithm. A new algorithm has been developed to improve the resolution of 4D-CT. In all experiments, the proposed method outperforms various interpolation methods, as well as BP and Zhang et al’s method, thus indicating the effectivity and competitiveness of the proposed algorithm.

  3. Minimal residual cone-beam reconstruction with attenuation correction in SPECT

    International Nuclear Information System (INIS)

    La, Valerie; Grangeat, Pierre

    1998-01-01

    This paper presents an iterative method based on the minimal residual algorithm for tomographic attenuation compensated reconstruction from attenuated cone-beam projections given the attenuation distribution. Unlike conjugate-gradient based reconstruction techniques, the proposed minimal residual based algorithm solves directly a quasisymmetric linear system, which is a preconditioned system. Thus it avoids the use of normal equations, which improves the convergence rate. Two main contributions are introduced. First, a regularization method is derived for quasisymmetric problems, based on a Tikhonov-Phillips regularization applied to the factorization of the symmetric part of the system matrix. This regularization is made spatially adaptive to avoid smoothing the region of interest. Second, our existing reconstruction algorithm for attenuation correction in parallel-beam geometry is extended to cone-beam geometry. A circular orbit is considered. Two preconditioning operators are proposed: the first one is Grangeat's inversion formula and the second one is Feldkamp's inversion formula. Experimental results obtained on simulated data are presented and the shadow zone effect on attenuated data is illustrated. (author)

  4. Image quality of multiplanar reconstruction of pulmonary CT scans using adaptive statistical iterative reconstruction.

    Science.gov (United States)

    Honda, O; Yanagawa, M; Inoue, A; Kikuyama, A; Yoshida, S; Sumikawa, H; Tobino, K; Koyama, M; Tomiyama, N

    2011-04-01

    We investigated the image quality of multiplanar reconstruction (MPR) using adaptive statistical iterative reconstruction (ASIR). Inflated and fixed lungs were scanned with a garnet detector CT in high-resolution mode (HR mode) or non-high-resolution (HR) mode, and MPR images were then reconstructed. Observers compared 15 MPR images of ASIR (40%) and ASIR (80%) with those of ASIR (0%), and assessed image quality using a visual five-point scale (1, definitely inferior; 5, definitely superior), with particular emphasis on normal pulmonary structures, artefacts, noise and overall image quality. The mean overall image quality scores in HR mode were 3.67 with ASIR (40%) and 4.97 with ASIR (80%). Those in non-HR mode were 3.27 with ASIR (40%) and 3.90 with ASIR (80%). The mean artefact scores in HR mode were 3.13 with ASIR (40%) and 3.63 with ASIR (80%), but those in non-HR mode were 2.87 with ASIR (40%) and 2.53 with ASIR (80%). The mean scores of the other parameters were greater than 3, whereas those in HR mode were higher than those in non-HR mode. There were significant differences between ASIR (40%) and ASIR (80%) in overall image quality (pASIR did not suppress the severe artefacts of contrast medium. In general, MPR image quality with ASIR (80%) was superior to that with ASIR (40%). However, there was an increased incidence of artefacts by ASIR when CT images were obtained in non-HR mode.

  5. SU-E-J-218: Evaluation of CT Images Created Using a New Metal Artifact Reduction Reconstruction Algorithm for Radiation Therapy Treatment Planning

    Energy Technology Data Exchange (ETDEWEB)

    Niemkiewicz, J; Palmiotti, A; Miner, M; Stunja, L; Bergene, J [Lehigh Valley Health Network, Allentown, PA (United States)

    2014-06-01

    Purpose: Metal in patients creates streak artifacts in CT images. When used for radiation treatment planning, these artifacts make it difficult to identify internal structures and affects radiation dose calculations, which depend on HU numbers for inhomogeneity correction. This work quantitatively evaluates a new metal artifact reduction (MAR) CT image reconstruction algorithm (GE Healthcare CT-0521-04.13-EN-US DOC1381483) when metal is present. Methods: A Gammex Model 467 Tissue Characterization phantom was used. CT images were taken of this phantom on a GE Optima580RT CT scanner with and without steel and titanium plugs using both the standard and MAR reconstruction algorithms. HU values were compared pixel by pixel to determine if the MAR algorithm altered the HUs of normal tissues when no metal is present, and to evaluate the effect of using the MAR algorithm when metal is present. Also, CT images of patients with internal metal objects using standard and MAR reconstruction algorithms were compared. Results: Comparing the standard and MAR reconstructed images of the phantom without metal, 95.0% of pixels were within ±35 HU and 98.0% of pixels were within ±85 HU. Also, the MAR reconstruction algorithm showed significant improvement in maintaining HUs of non-metallic regions in the images taken of the phantom with metal. HU Gamma analysis (2%, 2mm) of metal vs. non-metal phantom imaging using standard reconstruction resulted in an 84.8% pass rate compared to 96.6% for the MAR reconstructed images. CT images of patients with metal show significant artifact reduction when reconstructed with the MAR algorithm. Conclusion: CT imaging using the MAR reconstruction algorithm provides improved visualization of internal anatomy and more accurate HUs when metal is present compared to the standard reconstruction algorithm. MAR reconstructed CT images provide qualitative and quantitative improvements over current reconstruction algorithms, thus improving radiation

  6. SU-E-J-218: Evaluation of CT Images Created Using a New Metal Artifact Reduction Reconstruction Algorithm for Radiation Therapy Treatment Planning

    International Nuclear Information System (INIS)

    Niemkiewicz, J; Palmiotti, A; Miner, M; Stunja, L; Bergene, J

    2014-01-01

    Purpose: Metal in patients creates streak artifacts in CT images. When used for radiation treatment planning, these artifacts make it difficult to identify internal structures and affects radiation dose calculations, which depend on HU numbers for inhomogeneity correction. This work quantitatively evaluates a new metal artifact reduction (MAR) CT image reconstruction algorithm (GE Healthcare CT-0521-04.13-EN-US DOC1381483) when metal is present. Methods: A Gammex Model 467 Tissue Characterization phantom was used. CT images were taken of this phantom on a GE Optima580RT CT scanner with and without steel and titanium plugs using both the standard and MAR reconstruction algorithms. HU values were compared pixel by pixel to determine if the MAR algorithm altered the HUs of normal tissues when no metal is present, and to evaluate the effect of using the MAR algorithm when metal is present. Also, CT images of patients with internal metal objects using standard and MAR reconstruction algorithms were compared. Results: Comparing the standard and MAR reconstructed images of the phantom without metal, 95.0% of pixels were within ±35 HU and 98.0% of pixels were within ±85 HU. Also, the MAR reconstruction algorithm showed significant improvement in maintaining HUs of non-metallic regions in the images taken of the phantom with metal. HU Gamma analysis (2%, 2mm) of metal vs. non-metal phantom imaging using standard reconstruction resulted in an 84.8% pass rate compared to 96.6% for the MAR reconstructed images. CT images of patients with metal show significant artifact reduction when reconstructed with the MAR algorithm. Conclusion: CT imaging using the MAR reconstruction algorithm provides improved visualization of internal anatomy and more accurate HUs when metal is present compared to the standard reconstruction algorithm. MAR reconstructed CT images provide qualitative and quantitative improvements over current reconstruction algorithms, thus improving radiation

  7. Autocalibration method for non-stationary CT bias correction.

    Science.gov (United States)

    Vegas-Sánchez-Ferrero, Gonzalo; Ledesma-Carbayo, Maria J; Washko, George R; Estépar, Raúl San José

    2018-02-01

    Computed tomography (CT) is a widely used imaging modality for screening and diagnosis. However, the deleterious effects of radiation exposure inherent in CT imaging require the development of image reconstruction methods which can reduce exposure levels. The development of iterative reconstruction techniques is now enabling the acquisition of low-dose CT images whose quality is comparable to that of CT images acquired with much higher radiation dosages. However, the characterization and calibration of the CT signal due to changes in dosage and reconstruction approaches is crucial to provide clinically relevant data. Although CT scanners are calibrated as part of the imaging workflow, the calibration is limited to select global reference values and does not consider other inherent factors of the acquisition that depend on the subject scanned (e.g. photon starvation, partial volume effect, beam hardening) and result in a non-stationary noise response. In this work, we analyze the effect of reconstruction biases caused by non-stationary noise and propose an autocalibration methodology to compensate it. Our contributions are: 1) the derivation of a functional relationship between observed bias and non-stationary noise, 2) a robust and accurate method to estimate the local variance, 3) an autocalibration methodology that does not necessarily rely on a calibration phantom, attenuates the bias caused by noise and removes the systematic bias observed in devices from different vendors. The validation of the proposed methodology was performed with a physical phantom and clinical CT scans acquired with different configurations (kernels, doses, algorithms including iterative reconstruction). The results confirmed the suitability of the proposed methods for removing the intra-device and inter-device reconstruction biases. Copyright © 2017 Elsevier B.V. All rights reserved.

  8. The role of 3D Helical CT in the reconstructive treatment of maxillofacial cancers

    International Nuclear Information System (INIS)

    De Rosa, V.; Ziviello, M.; Ionna, F.; Mozzillo, N.; Parascandolo, S.

    2000-01-01

    Purpose of this work is to investigate the role of Helical CT and the usefulness of three-dimensional (3D) imaging for pre-operative planning and follow-up of reconstructive maxillofacial surgery with alloplastic material in neoplastic disease involving this region. From 1996 to 1999 eleven patients were examined with Helical CT and 3D images for planning of maxillofacial plastic and reconstructive surgery for advanced cancer of this anatomically complex region. A 3D-modulated titanium mesh (100%) or micro nets was used to rebuild the anterior surface of maxillary bone and the orbital floor. The mesh was cut to the appropriate size and shape and curved where necessary. Within the residual sinusal cavity a siliconed filling was used surmounting an acrylic prosthesis with dental arch to rebuild the palate. A rehydrated bovine pericardium was affixed and moduled on the borders in two cases only. Three-dimensionally reconstructed CT images were obtained preoperatively and at least 6 months postoperatively in all patients. The images were generated on a computer workstation using the shaded surface display (SSD) software with threshold values ranging 425 to 630 HU, and a more closed window for the imaging of titanium mesh/bone interface in the post surgical follow-up. It was obtained an excellent complete spatial depiction of maxillo facial region both before and after surgery, with no artefacts so important as to affect the 3D reconstruction process and the image quality. Together with the head-neck surgical team it could be worked for preoperative planning through CT scans by different 3D points of view. The 3D reconstructed follow-up scans showed good filling of the defect in the area where the titanium mesh had been used. Then efficacious bone modelling and good biocompatibility of the alloplastic material were seen in all patients, with no inflammatory reactions. Titanium is a well-known material, which is widely used for cranioplasty. It is a radiolucent, non

  9. Cranial CT with adaptive statistical iterative reconstruction: improved image quality with concomitant radiation dose reduction.

    Science.gov (United States)

    Rapalino, O; Kamalian, Shervin; Kamalian, Shahmir; Payabvash, S; Souza, L C S; Zhang, D; Mukta, J; Sahani, D V; Lev, M H; Pomerantz, S R

    2012-04-01

    To safeguard patient health, there is great interest in CT radiation-dose reduction. The purpose of this study was to evaluate the impact of an iterative-reconstruction algorithm, ASIR, on image-quality measures in reduced-dose head CT scans for adult patients. Using a 64-section scanner, we analyzed 100 reduced-dose adult head CT scans at 6 predefined levels of ASIR blended with FBP reconstruction. These scans were compared with 50 CT scans previously obtained at a higher routine dose without ASIR reconstruction. SNR and CNR were computed from Hounsfield unit measurements of normal GM and WM of brain parenchyma. A blinded qualitative analysis was performed in 10 lower-dose CT datasets compared with higher-dose ones without ASIR. Phantom data analysis was also performed. Lower-dose scans without ASIR had significantly lower mean GM and WM SNR (P = .003) and similar GM-WM CNR values compared with higher routine-dose scans. However, at ASIR levels of 20%-40%, there was no statistically significant difference in SNR, and at ASIR levels of ≥60%, the SNR values of the reduced-dose scans were significantly higher (P ASIR levels of ≥40% (P ASIR levels ≥60% (P ASIR in adult head CT scans reduces image noise and increases low-contrast resolution, while allowing lower radiation doses without affecting spatial resolution.

  10. Registration-based Reconstruction of Four-dimensional Cone Beam Computed Tomography

    DEFF Research Database (Denmark)

    Christoffersen, Christian; Hansen, David Christoffer; Poulsen, Per Rugaard

    2013-01-01

    We present a new method for reconstruction of four-dimensional (4D) cone beam computed tomography from an undersampled set of X-ray projections. The novelty of the proposed method lies in utilizing optical flow based registration to facilitate that each temporal phase is reconstructed from the full...

  11. Comparison of adaptive statistical iterative and filtered back projection reconstruction techniques in brain CT

    International Nuclear Information System (INIS)

    Ren, Qingguo; Dewan, Sheilesh Kumar; Li, Ming; Li, Jianying; Mao, Dingbiao; Wang, Zhenglei; Hua, Yanqing

    2012-01-01

    Purpose: To compare image quality and visualization of normal structures and lesions in brain computed tomography (CT) with adaptive statistical iterative reconstruction (ASIR) and filtered back projection (FBP) reconstruction techniques in different X-ray tube current–time products. Materials and methods: In this IRB-approved prospective study, forty patients (nineteen men, twenty-one women; mean age 69.5 ± 11.2 years) received brain scan at different tube current–time products (300 and 200 mAs) in 64-section multi-detector CT (GE, Discovery CT750 HD). Images were reconstructed with FBP and four levels of ASIR-FBP blending. Two radiologists (please note that our hospital is renowned for its geriatric medicine department, and these two radiologists are more experienced in chronic cerebral vascular disease than in neoplastic disease, so this research did not contain cerebral tumors but as a discussion) assessed all the reconstructed images for visibility of normal structures, lesion conspicuity, image contrast and diagnostic confidence in a blinded and randomized manner. Volume CT dose index (CTDI vol ) and dose-length product (DLP) were recorded. All the data were analyzed by using SPSS 13.0 statistical analysis software. Results: There was no statistically significant difference between the image qualities at 200 mAs with 50% ASIR blending technique and 300 mAs with FBP technique (p > .05). While between the image qualities at 200 mAs with FBP and 300 mAs with FBP technique a statistically significant difference (p < .05) was found. Conclusion: ASIR provided same image quality and diagnostic ability in brain imaging with greater than 30% dose reduction compared with FBP reconstruction technique

  12. Comparison of adaptive statistical iterative and filtered back projection reconstruction techniques in brain CT

    Energy Technology Data Exchange (ETDEWEB)

    Ren, Qingguo, E-mail: renqg83@163.com [Department of Radiology, Hua Dong Hospital of Fudan University, Shanghai 200040 (China); Dewan, Sheilesh Kumar, E-mail: sheilesh_d1@hotmail.com [Department of Geriatrics, Hua Dong Hospital of Fudan University, Shanghai 200040 (China); Li, Ming, E-mail: minli77@163.com [Department of Radiology, Hua Dong Hospital of Fudan University, Shanghai 200040 (China); Li, Jianying, E-mail: Jianying.Li@med.ge.com [CT Imaging Research Center, GE Healthcare China, Beijing (China); Mao, Dingbiao, E-mail: maodingbiao74@163.com [Department of Radiology, Hua Dong Hospital of Fudan University, Shanghai 200040 (China); Wang, Zhenglei, E-mail: Williswang_doc@yahoo.com.cn [Department of Radiology, Shanghai Electricity Hospital, Shanghai 200050 (China); Hua, Yanqing, E-mail: cjr.huayanqing@vip.163.com [Department of Radiology, Hua Dong Hospital of Fudan University, Shanghai 200040 (China)

    2012-10-15

    Purpose: To compare image quality and visualization of normal structures and lesions in brain computed tomography (CT) with adaptive statistical iterative reconstruction (ASIR) and filtered back projection (FBP) reconstruction techniques in different X-ray tube current–time products. Materials and methods: In this IRB-approved prospective study, forty patients (nineteen men, twenty-one women; mean age 69.5 ± 11.2 years) received brain scan at different tube current–time products (300 and 200 mAs) in 64-section multi-detector CT (GE, Discovery CT750 HD). Images were reconstructed with FBP and four levels of ASIR-FBP blending. Two radiologists (please note that our hospital is renowned for its geriatric medicine department, and these two radiologists are more experienced in chronic cerebral vascular disease than in neoplastic disease, so this research did not contain cerebral tumors but as a discussion) assessed all the reconstructed images for visibility of normal structures, lesion conspicuity, image contrast and diagnostic confidence in a blinded and randomized manner. Volume CT dose index (CTDI{sub vol}) and dose-length product (DLP) were recorded. All the data were analyzed by using SPSS 13.0 statistical analysis software. Results: There was no statistically significant difference between the image qualities at 200 mAs with 50% ASIR blending technique and 300 mAs with FBP technique (p > .05). While between the image qualities at 200 mAs with FBP and 300 mAs with FBP technique a statistically significant difference (p < .05) was found. Conclusion: ASIR provided same image quality and diagnostic ability in brain imaging with greater than 30% dose reduction compared with FBP reconstruction technique.

  13. Edge plasma density reconstruction for fast monoenergetic lithium beam probing

    International Nuclear Information System (INIS)

    Sasaki, S.; Takamura, S.; Ueda, M.; Iguchi, H.; Fujita, J.; Kadota, K.

    1993-01-01

    Two different electron density reconstruction methods for 8-keV neutral lithium beam probing have been developed for the Compact Helical System (CHS). Density dependences on emission and ionization processes are included by using effective rate coefficients obtained from the collisional radiative model. Since the two methods differ in the way the local beam density in the plasma is determined, the methods have different applicable electron densities. The beam attenuation is calculated by iteration from the electron density profile in method I. In method II, the beam remainder at the observation point z is determined by integrating the Li I emission intensity from z toward the position of emission tail-off. At the emission tail-off, the fast lithium beam is completely attenuated. Selecting an appropriate method enables us to obtain edge electron density profile well inside the last closed flux surface for various ranges of plasma densities (10 12 --5x10 13 cm -3 ). The electron density profiles reconstructed by these two different methods are in good agreement with each other and are consistent with results from ruby laser Thomson scattering

  14. Preoperative CT angiography reduces surgery time in perforator flap reconstruction

    NARCIS (Netherlands)

    Smit, Jeroen M.; Dimopoulou, Angeliki; Liss, Anders G.; Zeebregts, Clark J.; Kildal, Morten; Whitaker, Iain S.; Magnusson, Anders; Acosta, Rafael

    The use of perforator flaps in breast reconstructions has increased considerably in the past decade. A disadvantage of the perforator flap is difficult dissection, which results in a longer procedure. During spring 2006, we introduced CT angiography (CTA) as part of the diagnostic work-up in

  15. Study of residual stresses in CT test specimens welded by electron beam

    Science.gov (United States)

    Papushkin, I. V.; Kaisheva, D.; Bokuchava, G. D.; Angelov, V.; Petrov, P.

    2018-03-01

    The paper reports result of residual stress distribution studies in CT specimens reconstituted by electron beam welding (EBW). The main aim of the study is evaluation of the applicability of the welding technique for CT specimens’ reconstitution. Thus, the temperature distribution during electron beam welding of a CT specimen was calculated using Green’s functions and the residual stress distribution was determined experimentally using neutron diffraction. Time-of-flight neutron diffraction experiments were performed on a Fourier stress diffractometer at the IBR-2 fast pulsed reactor in FLNP JINR (Dubna, Russia). The neutron diffraction data estimates yielded a maximal stress level of ±180 MPa in the welded joint.

  16. Application of three-dimensional CT reconstruction technology on inferior oblique muscle in congenital superior oblique palsy

    Directory of Open Access Journals (Sweden)

    Yang Zhang

    2014-05-01

    Full Text Available AIM: To investigate the viability of the morphology of inferior oblique muscle observed stereoscopically using 3-dimensional CT reconstruction technique. METHODS: This control study included of 29 cases which were clinically diagnosed with monocular congenital superior oblique palsy, examined by dimensional CT. The images of the inferior oblique muscle were reconstructed by Mimics software. 3D digital images on the basis of CT scanning data of the individuals were established. Observing the morphology of binocular inferior oblique muscle by self-controlled design, we compared the maximum transverse diameter of inferior oblique muscle of paralyzed eye with non-paralyzed one. We chose 5% as the significant level.RESULTS: The reconstructed results of 3-dimensional CT scan showed that not all of the inferior oblique abdominal muscle of paralyzed eyes were thinner than that of the non-paralyzed eye in maximum transverse diameter of cross-sectional area. The maximum transverse diameter of inferior oblique muscle was measured. The average maximum transverse diameter of the paralyzed eye was 6.797±1.083mm and the non-paralyzed eye was 6.507±0.848mm. The maximum transverse diameter of inferior oblique muscle of paralyzed eye did not, however, differ significantly from the normal(P>0.05. CONCLUSION: The three-dimensional CT reconstruction technology can be used for preoperative evaluation of the morphology of inferior oblique muscle.

  17. Diagnostic value of multiplanar reconstruction in CT recognition of lumbar spinal disorders

    International Nuclear Information System (INIS)

    Im, S. K.; Choi, J. H.; Kim, C. H.; Sohn, M. H.; Lim, K. Y.; Choi, K. C.

    1984-01-01

    The computer tomography is useful in evaluation of bony structures and adjacent soft tissues of the lumbar spine. Recently, the multiplanar reconstruction of lumbar spine of CT of significant value for the anatomical localization and for the myelographic and surgical correlation. We observed 177 cases of lumbar spine CT, who complains of spinal symptom, during the period from Dec. 1982 to Aug. 1984. The results were as follows: 1. The sex distribution of cases were 113 males and 44 females. The CT diagnosis showed 152 cases of herniated lumbar disc, 15 cases of degenerative disease, 5 cases of spine tbc., 3 cases of spine trauma and 2 cases of meningocele. 2. CT findings of herniated disc were as follows: focal protrusion of posterior disc margin and obliteration of anterior epidural fat in all cases, indentation on dural sac in 92 cases (60.5%) soft tissue mass in epidural fat in 85 cases (55.9%), compression or displacement of nerve root sheath in 22 cases(14.4%). 3. Sites of herniated lumbar disc were at L4-L5 level in 100 cases(59.1%) and at L5-S1 level in 65 cases (38.4%). Location of it were central type in 70 cases(41.1%), left-central type in 46 cases (27.2%), right-central type in 44 cases(26.0%) and lateral type in 9 cases (5.1%). 4. The sagittal reconstruction images were helpful in evaluating neural foramina, size of disc bluge into spinal canal, especially at L5-S1, and patients with spondylolisthesis. The coronal reconstruction images were the least informative, although they contributed to the evaluation of lumbar nerve roots of course, the axial CT scans were the most sensitive and specific.

  18. Accelerated gradient methods for total-variation-based CT image reconstruction

    DEFF Research Database (Denmark)

    Jørgensen, Jakob Heide; Jensen, Tobias Lindstrøm; Hansen, Per Christian

    2011-01-01

    incorporates several heuristics from the optimization literature such as Barzilai-Borwein (BB) step size selection and nonmonotone line search. The latter uses a cleverly chosen sequence of auxiliary points to achieve a better convergence rate. The methods are memory efficient and equipped with a stopping...... reconstruction can in principle be found by any optimization method, but in practice the large scale of the systems arising in CT image reconstruction preclude the use of memory-demanding methods such as Newton’s method. The simple gradient method has much lower memory requirements, but exhibits slow convergence...

  19. Potential benefit of the CT adaptive statistical iterative reconstruction method for pediatric cardiac diagnosis

    Science.gov (United States)

    Miéville, Frédéric A.; Ayestaran, Paul; Argaud, Christophe; Rizzo, Elena; Ou, Phalla; Brunelle, Francis; Gudinchet, François; Bochud, François; Verdun, Francis R.

    2010-04-01

    Adaptive Statistical Iterative Reconstruction (ASIR) is a new imaging reconstruction technique recently introduced by General Electric (GE). This technique, when combined with a conventional filtered back-projection (FBP) approach, is able to improve the image noise reduction. To quantify the benefits provided on the image quality and the dose reduction by the ASIR method with respect to the pure FBP one, the standard deviation (SD), the modulation transfer function (MTF), the noise power spectrum (NPS), the image uniformity and the noise homogeneity were examined. Measurements were performed on a control quality phantom when varying the CT dose index (CTDIvol) and the reconstruction kernels. A 64-MDCT was employed and raw data were reconstructed with different percentages of ASIR on a CT console dedicated for ASIR reconstruction. Three radiologists also assessed a cardiac pediatric exam reconstructed with different ASIR percentages using the visual grading analysis (VGA) method. For the standard, soft and bone reconstruction kernels, the SD is reduced when the ASIR percentage increases up to 100% with a higher benefit for low CTDIvol. MTF medium frequencies were slightly enhanced and modifications of the NPS shape curve were observed. However for the pediatric cardiac CT exam, VGA scores indicate an upper limit of the ASIR benefit. 40% of ASIR was observed as the best trade-off between noise reduction and clinical realism of organ images. Using phantom results, 40% of ASIR corresponded to an estimated dose reduction of 30% under pediatric cardiac protocol conditions. In spite of this discrepancy between phantom and clinical results, the ASIR method is as an important option when considering the reduction of radiation dose, especially for pediatric patients.

  20. Automated planning of breast radiotherapy using cone beam CT imaging

    International Nuclear Information System (INIS)

    Amit, Guy; Purdie, Thomas G.

    2015-01-01

    Purpose: Develop and clinically validate a methodology for using cone beam computed tomography (CBCT) imaging in an automated treatment planning framework for breast IMRT. Methods: A technique for intensity correction of CBCT images was developed and evaluated. The technique is based on histogram matching of CBCT image sets, using information from “similar” planning CT image sets from a database of paired CBCT and CT image sets (n = 38). Automated treatment plans were generated for a testing subset (n = 15) on the planning CT and the corrected CBCT. The plans generated on the corrected CBCT were compared to the CT-based plans in terms of beam parameters, dosimetric indices, and dose distributions. Results: The corrected CBCT images showed considerable similarity to their corresponding planning CTs (average mutual information 1.0±0.1, average sum of absolute differences 185 ± 38). The automated CBCT-based plans were clinically acceptable, as well as equivalent to the CT-based plans with average gantry angle difference of 0.99°±1.1°, target volume overlap index (Dice) of 0.89±0.04 although with slightly higher maximum target doses (4482±90 vs 4560±84, P < 0.05). Gamma index analysis (3%, 3 mm) showed that the CBCT-based plans had the same dose distribution as plans calculated with the same beams on the registered planning CTs (average gamma index 0.12±0.04, gamma <1 in 99.4%±0.3%). Conclusions: The proposed method demonstrates the potential for a clinically feasible and efficient online adaptive breast IMRT planning method based on CBCT imaging, integrating automation

  1. Development of a 3-dimensional CT using an image intensifier

    International Nuclear Information System (INIS)

    Toyofuku, Fukai

    1992-01-01

    A prototype of three-dimensional CT (Fluoroscopic CT) has been developed using an image intensifier as a two-dimensional X-ray detector. A patient on a rotating table is projected onto an image intensifier by a cone beam of X-ray from the X-ray tube. A total of 390 projection images covering 180 degrees are acquired in a single scan (13 sec) and stored on a digital frame recorder (512 x 256 x 8-bit x 480). The transverse axial images are reconstructed by using the usual CT reconstruction algorithm, while longitudinal section images such as sagittal, coronal, oblique, and panoramic images are obtained by directly back-projecting the filtered projection image onto the sections. The radiation exposure was measured with an ionization chamber, and the exposure of the present fluoroscopic CT is about 10 to 20 times less than that of conventional X-ray CT. A similar monochromatic X-ray CT system has also been developed using synchrotron radiation. Large area parallel X-rays are obtained from a wiggler beam using a silicon crystal with [311] asymmetric reflection. By taking two images above and below iodine K-absorption edge (33.17 keV), iodine image is obtained. (author)

  2. Self-reconstruction of diffraction-free and accelerating laser beams in scattering media

    International Nuclear Information System (INIS)

    Ersoy, T.; Yalizay, B.; Akturk, S.

    2012-01-01

    We experimentally investigate propagation of laser beams with different intensity profiles in highly scattering media. We generate transverse laser amplitude profiles with Gaussian, Bessel and Airy function envelopes. We then propagate these beams through optical phantoms formed with variable density intralipid solutions. At the sample exit, we compare change in maximum intensities, as well as beam profile reconstruction. We show that self-reconstruction properties of Bessel and Airy beams bring about slower decrease in maximum intensity with increasing scatterer density. On the other hand, the beam profiles deteriorate faster, as compared to reference Gaussian beams. Slower decrease in the intensity can be attributed to the wavevector spectra providing a continuous flow of energy to the beam center, while beam deterioration is linked to total beam volume in the scattering medium. These results show that beam shaping methods can significantly enhance delivery of intense light deeper into turbid media, but this enhancement is compromised by stronger speckling of beam profiles. -- Highlights: ► We experimentally investigate propagation of shaped laser beams in turbid media. ► Peak intensity of Bessel and Airy beams decrease slower with increasing scatterer. ► Shaped beam profiles deteriorate faster, as compared to reference Gaussian beams. ► Shaped beam profiles can enhance applications of lasers inscattering media.

  3. Electro-optical system for the high speed reconstruction of computed tomography images

    International Nuclear Information System (INIS)

    Tresp, V.

    1989-01-01

    An electro-optical system for the high-speed reconstruction of computed tomography (CT) images has been built and studied. The system is capable of reconstructing high-contrast and high-resolution images at video rate (30 images per second), which is more than two orders of magnitude faster than the reconstruction rate achieved by special purpose digital computers used in commercial CT systems. The filtered back-projection algorithm which was implemented in the reconstruction system requires the filtering of all projections with a prescribed filter function. A space-integrating acousto-optical convolver, a surface acoustic wave filter and a digital finite-impulse response filter were used for this purpose and their performances were compared. The second part of the reconstruction, the back projection of the filtered projections, is computationally very expensive. An optical back projector has been built which maps the filtered projections onto the two-dimensional image space using an anamorphic lens system and a prism image rotator. The reconstructed image is viewed by a video camera, routed through a real-time image-enhancement system, and displayed on a TV monitor. The system reconstructs parallel-beam projection data, and in a modified version, is also capable of reconstructing fan-beam projection data. This extension is important since the latter are the kind of projection data actually acquired in high-speed X-ray CT scanners. The reconstruction system was tested by reconstructing precomputed projection data of phantom images. These were stored in a special purpose projection memory and transmitted to the reconstruction system as an electronic signal. In this way, a projection measurement system that acquires projections sequentially was simulated

  4. Intra-individual diagnostic image quality and organ-specific-radiation dose comparison between spiral cCT with iterative image reconstruction and z-axis automated tube current modulation and sequential cCT

    International Nuclear Information System (INIS)

    Wenz, Holger; Maros, Máté E.; Meyer, Mathias; Gawlitza, Joshua; Förster, Alex; Haubenreisser, Holger; Kurth, Stefan; Schoenberg, Stefan O.; Groden, Christoph; Henzler, Thomas

    2016-01-01

    •Superiority of spiral versus sequential cCT in image quality and organ-specific-radiation dose.•Spiral cCT: lower organ-specific-radiation-dose in eye lense compared to tilted sequential cCT.•State-of-the-art IR spiral cCT techniques has significant advantages over sequential cCT techniques. Superiority of spiral versus sequential cCT in image quality and organ-specific-radiation dose. Spiral cCT: lower organ-specific-radiation-dose in eye lense compared to tilted sequential cCT. State-of-the-art IR spiral cCT techniques has significant advantages over sequential cCT techniques. To prospectively evaluate image quality and organ-specific-radiation dose of spiral cranial CT (cCT) combined with automated tube current modulation (ATCM) and iterative image reconstruction (IR) in comparison to sequential tilted cCT reconstructed with filtered back projection (FBP) without ATCM. 31 patients with a previous performed tilted non-contrast enhanced sequential cCT aquisition on a 4-slice CT system with only FBP reconstruction and no ATCM were prospectively enrolled in this study for a clinical indicated cCT scan. All spiral cCT examinations were performed on a 3rd generation dual-source CT system using ATCM in z-axis direction. Images were reconstructed using both, FBP and IR (level 1–5). A Monte-Carlo-simulation-based analysis was used to compare organ-specific-radiation dose. Subjective image quality for various anatomic structures was evaluated using a 4-point Likert-scale and objective image quality was evaluated by comparing signal-to-noise ratios (SNR). Spiral cCT led to a significantly lower (p < 0.05) organ-specific-radiation dose in all targets including eye lense. Subjective image quality of spiral cCT datasets with an IR reconstruction level 5 was rated significantly higher compared to the sequential cCT acquisitions (p < 0.0001). Consecutive mean SNR was significantly higher in all spiral datasets (FBP, IR 1–5) when compared to sequential cCT with a mean

  5. Accurate technique for complete geometric calibration of cone-beam computed tomography systems

    International Nuclear Information System (INIS)

    Cho Youngbin; Moseley, Douglas J.; Siewerdsen, Jeffrey H.; Jaffray, David A.

    2005-01-01

    Cone-beam computed tomography systems have been developed to provide in situ imaging for the purpose of guiding radiation therapy. Clinical systems have been constructed using this approach, a clinical linear accelerator (Elekta Synergy RP) and an iso-centric C-arm. Geometric calibration involves the estimation of a set of parameters that describes the geometry of such systems, and is essential for accurate image reconstruction. We have developed a general analytic algorithm and corresponding calibration phantom for estimating these geometric parameters in cone-beam computed tomography (CT) systems. The performance of the calibration algorithm is evaluated and its application is discussed. The algorithm makes use of a calibration phantom to estimate the geometric parameters of the system. The phantom consists of 24 steel ball bearings (BBs) in a known geometry. Twelve BBs are spaced evenly at 30 deg in two plane-parallel circles separated by a given distance along the tube axis. The detector (e.g., a flat panel detector) is assumed to have no spatial distortion. The method estimates geometric parameters including the position of the x-ray source, position, and rotation of the detector, and gantry angle, and can describe complex source-detector trajectories. The accuracy and sensitivity of the calibration algorithm was analyzed. The calibration algorithm estimates geometric parameters in a high level of accuracy such that the quality of CT reconstruction is not degraded by the error of estimation. Sensitivity analysis shows uncertainty of 0.01 deg. (around beam direction) to 0.3 deg. (normal to the beam direction) in rotation, and 0.2 mm (orthogonal to the beam direction) to 4.9 mm (beam direction) in position for the medical linear accelerator geometry. Experimental measurements using a laboratory bench Cone-beam CT system of known geometry demonstrate the sensitivity of the method in detecting small changes in the imaging geometry with an uncertainty of 0.1 mm in

  6. Impact of Reconstruction Algorithms on CT Radiomic Features of Pulmonary Tumors: Analysis of Intra- and Inter-Reader Variability and Inter-Reconstruction Algorithm Variability.

    Science.gov (United States)

    Kim, Hyungjin; Park, Chang Min; Lee, Myunghee; Park, Sang Joon; Song, Yong Sub; Lee, Jong Hyuk; Hwang, Eui Jin; Goo, Jin Mo

    2016-01-01

    To identify the impact of reconstruction algorithms on CT radiomic features of pulmonary tumors and to reveal and compare the intra- and inter-reader and inter-reconstruction algorithm variability of each feature. Forty-two patients (M:F = 19:23; mean age, 60.43±10.56 years) with 42 pulmonary tumors (22.56±8.51mm) underwent contrast-enhanced CT scans, which were reconstructed with filtered back projection and commercial iterative reconstruction algorithm (level 3 and 5). Two readers independently segmented the whole tumor volume. Fifteen radiomic features were extracted and compared among reconstruction algorithms. Intra- and inter-reader variability and inter-reconstruction algorithm variability were calculated using coefficients of variation (CVs) and then compared. Among the 15 features, 5 first-order tumor intensity features and 4 gray level co-occurrence matrix (GLCM)-based features showed significant differences (palgorithms. As for the variability, effective diameter, sphericity, entropy, and GLCM entropy were the most robust features (CV≤5%). Inter-reader variability was larger than intra-reader or inter-reconstruction algorithm variability in 9 features. However, for entropy, homogeneity, and 4 GLCM-based features, inter-reconstruction algorithm variability was significantly greater than inter-reader variability (palgorithms. Inter-reconstruction algorithm variability was greater than inter-reader variability for entropy, homogeneity, and GLCM-based features.

  7. Postoperative follow-up study of craniosynostosis using three-dimensional surface reconstruction CT (3D-CT)

    Energy Technology Data Exchange (ETDEWEB)

    Nishimoto, Hiroshi; Tsukiyama, Takashi; Nishimura, Jiro; Fujioka, Mutsuhisa; Tsubokawa, Takashi.

    1988-12-01

    In 1983, Michael W. Vannier and Jeffrey L. Marsh developed a computer method that reconstructs three-dimensional images from high-resolution CT-scan series of the facial skeleton. This method has been applied to craniofacial anomalies, basal encephalocele, and other skeletal pathologies. In this study, the postoperative assessment of craniofacial surgical results has been accomplished using 3D-CT techniques in craniosynostosis. The results are as follows: (1) Postoperative 3D-CTs reveal the bony anatomical details corrected by the craniofacial surgery more precisely and more stereographically than do conventional radiological techniques. (2) Secondary changes in the cranium after the surgery, such as reossification at the area of osteotomies or postoperative asymmetric skull deformities, are more early detected by the 3D-CT imaging technique than by a craniogram. (3) In 3D-CT images, internal views of the skull, such mid-sagittal, rear internal, or top axial views of the intracranial skull base, are most useful in postoperative assessments of the surgical results and of postoperative secondary changes in the cranium. Based on our experience, we expect that 3D-CT imaging techniques will become more important in the management of craniosynostosis.

  8. Postoperative follow-up study of craniosynostosis using three-dimensional surface reconstruction CT (3D-CT)

    International Nuclear Information System (INIS)

    Nishimoto, Hiroshi; Tsukiyama, Takashi; Nishimura, Jiro; Fujioka, Mutsuhisa; Tsubokawa, Takashi.

    1988-01-01

    In 1983, Michael W. Vannier and Jeffrey L. Marsh developed a computer method that reconstructs three-dimensional images from high-resolution CT-scan series of the facial skeleton. This method has been applied to craniofacial anomalies, basal encephalocele, and other skeletal pathologies. In this study, the postoperative assessment of craniofacial surgical results has been accomplished using 3D-CT techniques in craniosynostosis. The results are as follows: 1) Postoperative 3D-CTs reveal the bony anatomical details corrected by the craniofacial surgery more precisely and more stereographically than do conventional radiological techniques. 2) Secondary changes in the cranium after the surgery, such as reossification at the area of osteotomies or postoperative asymmetric skull deformities, are more early detected by the 3D-CT imaging technique than by a craniogram. 3) In 3D-CT images, internal views of the skull, such mid-sagittal, rear internal, or top axial views of the intracranial skull base, are most useful in postoperative assessments of the surgical results and of postoperative secondary changes in the cranium. Based on our experience, we expect that 3D-CT imaging techniques will become more important in the management of craniosynostosis. (author)

  9. Technical evaluation of DIC helical CT and 3D image for laparoscopic cholecystectomy

    International Nuclear Information System (INIS)

    Shibuya, Kouki; Uchimura, Fumiaki; Haga, Tomo

    1995-01-01

    Recently Laparoscopic Cholecystectomy (L.C.) was widely accepted for its low invasive procedure. Before L.C., it is important to understand anatomical recognization of biliary tree. We examined DIC Helical CT before L.C., and reconstructed 3D Cholangiographic image. We evaluated physical potentiality of Helical CT using Section Sensitivity Profiles (SSP) with 5, 10 mm slice thickness on 360deg linear interpolation. And we analyzed most useful 3D image for biliary tree. Results showed the SSP depended on slice thickness (X-ray beam width) and table movement at same reconstruction spacing. The peak of SSP depended on slice thickness (X-ray beam width) and reconstruction spacing at same table movement. Clinically, it was necessary under 5 mm/rotation table movement and 5 mm thickness for acquiring volume image data. 3D Cholangiographic image reconstructed with 1 mm spacing image was useful in evaluation of relationship of anatomical biliary tree. (author)

  10. Reconstructions with identical filling (RIF) of the heart: a physiological approach to image reconstruction in coronary CT angiography

    International Nuclear Information System (INIS)

    Reinartz, S.D.; Diefenbach, B.S.; Kuhl, C.K.; Mahnken, A.H.; Allmendinger, T.

    2012-01-01

    To compare image quality in coronary artery computed tomography angiography (cCTA) using reconstructions with automated phase detection and Reconstructions computed with Identical Filling of the heart (RIF). Seventy-four patients underwent ECG-gated dual source CT (DSCT) between November 2009 and July 2010 for suspected coronary heart disease (n = 35), planning of transcatheter aortic valve replacement (n = 34) or evaluation of ventricular function (n = 5). Image data sets by the RIF formula and automated phase detection were computed and evaluated with the AHA 15-segment model and a 5-grade Likert scale (1: poor, 5: excellent quality). Subgroups regarding rhythm (sinus rhythm = SR; arrhythmia = ARR) and potential premedication were evaluated by a per-segment, per-vessel and per-patient analysis. RIF significantly improved image quality in 10 of 15 coronary segments (P < 0.05). More diagnostic segments were provided by RIF regarding the entire cohort (n = 693 vs. 590, P < 0.001) and all of the subgroups (e.g. ARR: n = 143 vs. 72, P < 0.001). In arrhythmic patients (n = 19), more diagnostic vessels (e.g. LAD: n = 10 vs. 3; P < 0.014) and complete data sets (n = 7 vs. 1; P < 0.001) were produced. RIF reconstruction is superior to automatic diastolic non-edited reconstructions, especially in arrhythmic patients. RIF theory provides a physiological approach for determining the optimal image reconstruction point in ECG-gated CT angiography. (orig.)

  11. Three-dimensional image analysis of a head of the giant panda by the cone-beam type CT

    International Nuclear Information System (INIS)

    Endo, H.; Komiya, T.; Narushima, E.; Suzuki, N.

    2002-01-01

    The cone-beam type CT (Computed Tomography) enabled us to collect the three-dimensional (3D) digitalized data directly from the animal carcass. In this study, we applied the techniques of the cone-beam type CT for a carcass head of the giant panda (Ailuropoda melanoleuca) to obtain the 3D images easily without reconstruction process, and could morphologically examine the sections from the 3D data by means of non-destructive observations. The important results of the study represent the two following points. 1) We could show the morphological relationships between the muscles of mastication and the mandible in non-destructive status from the 3D data. The exact position of the coronoid process could be recognized in the rostro-lateral space of the temporal fossa. 2) By the serial sections from the 3D data sets, the morphological characteristics in the nasal cavity were detailed with high resolution in this rare species. The nasal concha was well-developed in the nasal cavity. The ethmoidal labyrinth was encountered immediately caudal to the nasal cavity and close to the region of the olfactory bulb. The ethmoidal labyrinth consisted of the complicated osseous structure in this area. The data will be useful to discuss the olfactory function in the reproduction behavior of this species

  12. [The reliability of dento-maxillary models created by cone-beam CT and rapid prototyping:a comparative study].

    Science.gov (United States)

    Lv, Yan; Yan, Bin; Wang, Lin; Lou, Dong-hua

    2012-04-01

    To analyze the reliability of the dento-maxillary models created by cone-beam CT and rapid prototyping (RP). Plaster models were obtained from 20 orthodontic patients who had been scanned by cone-beam CT and 3-D models were formed after the calculation and reconstruction of software. Then, computerized composite models (RP models) were produced by rapid prototyping technique. The crown widths, dental arch widths and dental arch lengths on each plaster model, 3-D model and RP model were measured, followed by statistical analysis with SPSS17.0 software package. For crown widths, dental arch lengths and crowding, there were significant differences(Pmodels, but the dental arch widths were on the contrary. Measurements on 3-D models were significantly smaller than those on other two models(Pmodels, RP models had more numbers which were not significantly different from those on plaster models(P>0.05). The regression coefficient among three models were significantly different(Pmodels was bigger than that between 3-D and plaster models. There is high consistency within 3 models, while some differences were accepted in clinic. Therefore, it is possible to substitute 3-D and RP models for plaster models in order to save storage space and improve efficiency.

  13. Spiral CT of the pancreas. The value of small field-of-view targeted reconstruction

    International Nuclear Information System (INIS)

    Nishiharu, T.; Yamashita, Y.; Ogata, I.; Sumi, S.; Mitsuzaki, K.; Takahashi, M.

    1998-01-01

    Purpose: To compare the value of a retrospective targeted high-resolution spiral CT to the standard reconstruction technique in the assessment of pancreatic diseases. Material and methods: Spiral CT pancreatic images of a standard-size reconstruction protocol were compared prospectively with those of a retrospective targeted high-spatial-resolution reconstruction protocol in 30 patients. Prior to clinical evaluation, a phantom study was performed to evaluate the spatial resolution and signal-to-noise ratio of both protocols. Results: The high-resolution protocol achieved a good signal-to-noise ratio with acceptable spatial resolution. Phantom studies revealed increased image noise (+17%) with an increase in spatial resolution (+100%). In patients studied with the high-resolution protocol, the increase in noise was not significant but there was a marked improvement in the definition of small details. Conclusion: Images obtained with a targeted high-spatial-resolution reconstruction protocol showed superior lesion definition and vascular opacification compared with those obtained with a standard-size reconstruction protocol. This technique may have potential in the evaluation of small pancreatic abnormalities. (orig.)

  14. TV-constrained incremental algorithms for low-intensity CT image reconstruction

    DEFF Research Database (Denmark)

    Rose, Sean D.; Andersen, Martin S.; Sidky, Emil Y.

    2015-01-01

    constraint can be guided by an image reconstructed by filtered backprojection (FBP). We apply our algorithm to low-dose synchrotron X-ray CT data from the Advanced Photon Source (APS) at Argonne National Labs (ANL) to demonstrate its potential utility. We find that the algorithm provides a means of edge-preserving...

  15. Physics and basic technology of CT

    International Nuclear Information System (INIS)

    Mahesh, Mahadevappa

    2017-01-01

    Computed Tomography is one of the prime imaging modalities in any hospital around the globe. From its inception in 1973, CT technology have advanced leaps and bounds in medical diagnosis. Advances in X-ray tubes, detection technologies and image reconstruction methods led to the development of multiple-row detector CT (MDCT) technologies in early 2000, that has been the impetus for new fields such as Cardiovascular CT, Hybrid CT (PET-CT and SPECT-CT), CT Perfusion, Cone Beam CT, etc. It is now possible to image the entire organ (such as heart) in less than 0.3 seconds providing isotropic resolution images with high temporal resolution. With all X-ray imaging modalities, including CT, the concern is the radiation dose. Since CT procedures are one of the major imaging procedures performed in any hospital, it is important to optimize CT protocols in order to provide quality images at optimal radiation dose

  16. A prototype table-top inverse-geometry volumetric CT system

    International Nuclear Information System (INIS)

    Schmidt, Taly Gilat; Star-Lack, Josh; Bennett, N. Robert; Mazin, Samuel R.; Solomon, Edward G.; Fahrig, Rebecca; Pelc, Norbert J.

    2006-01-01

    A table-top volumetric CT system has been implemented that is able to image a 5-cm-thick volume in one circular scan with no cone-beam artifacts. The prototype inverse-geometry CT (IGCT) scanner consists of a large-area, scanned x-ray source and a detector array that is smaller in the transverse direction. The IGCT geometry provides sufficient volumetric sampling because the source and detector have the same axial, or slice direction, extent. This paper describes the implementation of the table-top IGCT scanner, which is based on the NexRay Scanning-Beam Digital X-ray system (NexRay, Inc., Los Gatos, CA) and an investigation of the system performance. The alignment and flat-field calibration procedures are described, along with a summary of the reconstruction algorithm. The resolution and noise performance of the prototype IGCT system are studied through experiments and further supported by analytical predictions and simulations. To study the presence of cone-beam artifacts, a ''Defrise'' phantom was scanned on both the prototype IGCT scanner and a micro CT system with a ±5 deg.cone angle for a 4.5-cm volume thickness. Images of inner ear specimens are presented and compared to those from clinical CT systems. Results showed that the prototype IGCT system has a 0.25-mm isotropic resolution and that noise comparable to that from a clinical scanner with equivalent spatial resolution is achievable. The measured MTF and noise values agreed reasonably well with theoretical predictions and computer simulations. The IGCT system was able to faithfully reconstruct the laminated pattern of the Defrise phantom while the micro CT system suffered severe cone-beam artifacts for the same object. The inner ear acquisition verified that the IGCT system can image a complex anatomical object, and the resulting images exhibited more high-resolution details than the clinical CT acquisition. Overall, the successful implementation of the prototype system supports the IGCT concept for

  17. A Fast CT Reconstruction Scheme for a General Multi-Core PC

    Directory of Open Access Journals (Sweden)

    Kai Zeng

    2007-01-01

    Full Text Available Expensive computational cost is a severe limitation in CT reconstruction for clinical applications that need real-time feedback. A primary example is bolus-chasing computed tomography (CT angiography (BCA that we have been developing for the past several years. To accelerate the reconstruction process using the filtered backprojection (FBP method, specialized hardware or graphics cards can be used. However, specialized hardware is expensive and not flexible. The graphics processing unit (GPU in a current graphic card can only reconstruct images in a reduced precision and is not easy to program. In this paper, an acceleration scheme is proposed based on a multi-core PC. In the proposed scheme, several techniques are integrated, including utilization of geometric symmetry, optimization of data structures, single-instruction multiple-data (SIMD processing, multithreaded computation, and an Intel C++ compilier. Our scheme maintains the original precision and involves no data exchange between the GPU and CPU. The merits of our scheme are demonstrated in numerical experiments against the traditional implementation. Our scheme achieves a speedup of about 40, which can be further improved by several folds using the latest quad-core processors.

  18. A fast CT reconstruction scheme for a general multi-core PC.

    Science.gov (United States)

    Zeng, Kai; Bai, Erwei; Wang, Ge

    2007-01-01

    Expensive computational cost is a severe limitation in CT reconstruction for clinical applications that need real-time feedback. A primary example is bolus-chasing computed tomography (CT) angiography (BCA) that we have been developing for the past several years. To accelerate the reconstruction process using the filtered backprojection (FBP) method, specialized hardware or graphics cards can be used. However, specialized hardware is expensive and not flexible. The graphics processing unit (GPU) in a current graphic card can only reconstruct images in a reduced precision and is not easy to program. In this paper, an acceleration scheme is proposed based on a multi-core PC. In the proposed scheme, several techniques are integrated, including utilization of geometric symmetry, optimization of data structures, single-instruction multiple-data (SIMD) processing, multithreaded computation, and an Intel C++ compilier. Our scheme maintains the original precision and involves no data exchange between the GPU and CPU. The merits of our scheme are demonstrated in numerical experiments against the traditional implementation. Our scheme achieves a speedup of about 40, which can be further improved by several folds using the latest quad-core processors.

  19. Use of quantitative SPECT/CT reconstruction in 99mTc-sestamibi imaging of patients with renal masses.

    Science.gov (United States)

    Jones, Krystyna M; Solnes, Lilja B; Rowe, Steven P; Gorin, Michael A; Sheikhbahaei, Sara; Fung, George; Frey, Eric C; Allaf, Mohamad E; Du, Yong; Javadi, Mehrbod S

    2018-02-01

    Technetium-99m ( 99m Tc)-sestamibi single-photon emission computed tomography/computed tomography (SPECT/CT) has previously been shown to allow for the accurate differentiation of benign renal oncocytomas and hybrid oncocytic/chromophobe tumors (HOCTs) apart from other malignant renal tumor histologies, with oncocytomas/HOCTs showing high uptake and renal cell carcinoma (RCC) showing low uptake based on uptake ratios from non-quantitative single-photon emission computed tomography (SPECT) reconstructions. However, in this study, several tumors fell close to the uptake ratio cutoff, likely due to limitations in conventional SPECT/CT reconstruction methods. We hypothesized that application of quantitative SPECT/CT (QSPECT) reconstruction methods developed by our group would provide more robust separation of hot and cold lesions, serving as an imaging framework on which quantitative biomarkers can be validated for evaluation of renal masses with 99m Tc-sestamibi. Single-photon emission computed tomography data were reconstructed using the clinical Flash 3D reconstruction and QSPECT methods. Two blinded readers then characterized each tumor as hot or cold. Semi-quantitative uptake ratios were calculated by dividing lesion activity by background renal activity for both Flash 3D and QSPECT reconstructions. The difference between median (mean) hot and cold tumor uptake ratios measured 0.655 (0.73) with the QSPECT method and 0.624 (0.67) with the conventional method, resulting in increased separation between hot and cold tumors. Sub-analysis of 7 lesions near the separation point showed a higher absolute difference (0.16) between QPSECT and Flash 3D mean uptake ratios compared to the remaining lesions. Our finding of improved separation between uptake ratios of hot and cold lesions using QSPECT reconstruction lays the foundation for additional quantitative SPECT techniques such as SPECT-UV in the setting of renal 99m Tc-sestamibi and other SPECT/CT exams. With robust

  20. Multi-sheet surface rebinning methods for reconstruction from asymmetrically truncated cone beam projections: I. Approximation and optimality

    International Nuclear Information System (INIS)

    Betcke, Marta M; Lionheart, William R B

    2013-01-01

    The mechanical motion of the gantry in conventional cone beam CT scanners restricts the speed of data acquisition in applications with near real time requirements. A possible resolution of this problem is to replace the moving source detector assembly with static parts that are electronically activated. An example of such a system is the Rapiscan Systems RTT80 real time tomography scanner, with a static ring of sources and axially offset static cylinder of detectors. A consequence of such a design is asymmetrical axial truncation of the cone beam projections resulting, in the sense of integral geometry, in severely incomplete data. In particular we collect data only in a fraction of the Tam–Danielsson window, hence the standard cone beam reconstruction techniques do not apply. In this work we propose a family of multi-sheet surface rebinning methods for reconstruction from such truncated projections. The proposed methods combine analytical and numerical ideas utilizing linearity of the ray transform to reconstruct data on multi-sheet surfaces, from which the volumetric image is obtained through deconvolution. In this first paper in the series, we discuss the rebinning to multi-sheet surfaces. In particular we concentrate on the underlying transforms on multi-sheet surfaces and their approximation with data collected by offset multi-source scanning geometries like the RTT. The optimal multi-sheet surface and the corresponding rebinning function are found as a solution of a variational problem. In the case of the quadratic objective, the variational problem for the optimal rebinning pair can be solved by a globally convergent iteration. Examples of optimal rebinning pairs are computed for different trajectories. We formulate the axial deconvolution problem for the recovery of the volumetric image from the reconstructions on multi-sheet surfaces. Efficient and stable solution of the deconvolution problem is the subject of the second paper in this series (Betcke and

  1. TU-H-207A-03: CT Hounsfield Unit Accuracy: Effect of Beam Hardening On Phantom and Clinical Whole-Body CT Images

    Energy Technology Data Exchange (ETDEWEB)

    Ai, H; Wendt, R [The University of Texas MD Anderson Cancer Center, Houston, TX (United States)

    2016-06-15

    Purpose: To assess the effect of beam hardening on measured CT HU values. Methods: An anthropomorphic knee phantom was scanned with the CT component of a GE Discovery 690 PET/CT scanner (120kVp, 300mAs, 40?0.625mm collimation, pitch=0.984, FOV=500mm, matrix=512?512) with four different scan setups, each of which induces different degrees of beam hardening by introducing additional attenuation media into the field of view. Homogeneous voxels representing “soft tissue” and “bone” were segmented by HU thresholding followed by a 3D morphological erosion operation which removes the non-homogenous voxels located on the interface of thresholded tissue mask. HU values of segmented “soft tissue” and “bone” were compared.Additionally, whole-body CT data with coverage from the skull apex to the end of toes were retrospectively retrieved from seven PET/CT exams to evaluate the effect of beam hardening in vivo. Homogeneous bone voxels were segmented with the same method previously described. Total In-Slice Attenuation (TISA) for each CT slice, defined as the summation of HU values over all voxels within a CT slice, was calculated for all slices of the seven whole-body CT datasets and evaluated against the mean HU values of homogeneous bone voxels within that slice. Results: HU values measured from the phantom showed that while “soft tissue” HU values were unaffected, added attenuation within the FOV caused noticeable decreases in the measured HU values of “bone” voxels. A linear relationship was observed between bone HU and TISA for slices of the torso and legs, but not of the skull. Conclusion: Beam hardening effect is not an issue of concern for voxels with HU in the soft tissue range, but should not be neglected for bone voxels. A linear relationship exists between bone HU and the associated TISA in non-skull CT slices, which can be exploited to develop a correction strategy.

  2. Relationships between cone beam CT value and physical density in image guided radiation therapy

    International Nuclear Information System (INIS)

    Jiang Xiaoqin; Bai Sen; Zhong Renming; Tang Zhiquan; Jiang Qinfeng; Li Tao

    2007-01-01

    Objective: To evaluate the main factors affecting the relationship between physical density and CT value in cone-beam computed tomography(CBCT) for imaging guided radiation therapy(IGRT) by comparing the CT value in the image from cone-beam scanner and from fan-beam (FBCT) scanner of a reference phantom. Methods: A taking-park reference phantom with a set of tissue equivalent inserts was scanned at different energies different fields of view (FOV) for IGRT-CBCT and FBCT. The CT value of every insert was measured and compared. Results: The position of inserts in phantom, the size of phantom, the FOV of scanner and different energies had more effect on the relationships between physical density and the CT value from IGRT-CBCT than those from the normal FBCT. The higher the energy was, the less effect of the position of inserts in phantom, the size of phantom and the FOV of scanner on CT value, and the poorer density contrast was observed. Conclusion: At present, the CT value of IGRT-CBCT is not in the true HU value since the manufacturer has not corrected its number. Therefore, we are not able to use the CT value of CBCT for dose calculation in TPS. (authors)

  3. Image-guided stereotactic surgery using ultrasonography and reconstructive three-dimensional CT-imaging system

    International Nuclear Information System (INIS)

    Kawamura, Hirotsune; Iseki, Hiroshi; Umezawa, Yoshihiro

    1991-01-01

    A new simulation and navigation system utilizing three-dimensional CT images has been developed for image-guided stereotactic surgery. Preoperative CT images are not always useful in predicting the intraoperative location of lesions, for cerebral lesions are easily displaced or distorted by gravity, brain retraction, and/or CSF aspiration during operative procedure. This new system, however, has the advantage that the intraoperative locations of intracranial lesions or the anatomical structures of the brain can be precisely confirmed during stereotactic surgery. Serial CT images were obtained from a patient whose head had been fixed to the ISEKI CT-guided stereotactic frame. The data of serial CT images were saved on a floppy disc and then transferred to the work station (IRIS) using the off line. In order to find the best approach angle for ultrasound-guided stereotactic surgery, three-dimenstional CT images were reconstructed using the work station. The site of the craniotomy or the angle of the trajectory of the ultrasound probe was measured preoperatively based on the three-dimensional CT images. Then, in the operating room, the patient's head was fixed to the ISEKI frame with the subframe at the same position as before according to the measurement of the CT images. In a case of cystic glioma, the predicable ultrasonograms from three-dimensional reconstructive CT images were ascertained to correspond well to the actual ultrasound images during ultrasound-guided stereotactic surgery. Therefore, the new simulation and navigation system can be judged to be a powerful operative supporting modality for correcting the locations of cerebral lesions; it allows one to perform stereotactic surgery more accurately and less invasively. (author)

  4. Reconstruction of MRI/CT compatible ring and tandem applicators in CT or MRI images used for treatment planning in brachytherapy

    International Nuclear Information System (INIS)

    Surendran, N.; Kim, Hayeon; Beriwal, Sushil; Saiful Huq, M.

    2008-01-01

    Brachytherapy (BT) plays a crucial role in the management of invasive cervix cancer from stage I to IV. Intracavitary techniques are based on afterloading devices, with different types of applicators. CT and/or MRI compatible applicators allow a sectional image based approach with a better assessment of gross tumour volume (GTV) and definition and delineation of target volume (CTV) compared to traditional approaches. To evaluate reconstruction of MRI/CT compatible ring and tandem applicators in 3D CT or MRI images used for treatment planning in Brachytherapy

  5. Model-based Iterative Reconstruction: Effect on Patient Radiation Dose and Image Quality in Pediatric Body CT

    Science.gov (United States)

    Dillman, Jonathan R.; Goodsitt, Mitchell M.; Christodoulou, Emmanuel G.; Keshavarzi, Nahid; Strouse, Peter J.

    2014-01-01

    Purpose To retrospectively compare image quality and radiation dose between a reduced-dose computed tomographic (CT) protocol that uses model-based iterative reconstruction (MBIR) and a standard-dose CT protocol that uses 30% adaptive statistical iterative reconstruction (ASIR) with filtered back projection. Materials and Methods Institutional review board approval was obtained. Clinical CT images of the chest, abdomen, and pelvis obtained with a reduced-dose protocol were identified. Images were reconstructed with two algorithms: MBIR and 100% ASIR. All subjects had undergone standard-dose CT within the prior year, and the images were reconstructed with 30% ASIR. Reduced- and standard-dose images were evaluated objectively and subjectively. Reduced-dose images were evaluated for lesion detectability. Spatial resolution was assessed in a phantom. Radiation dose was estimated by using volumetric CT dose index (CTDIvol) and calculated size-specific dose estimates (SSDE). A combination of descriptive statistics, analysis of variance, and t tests was used for statistical analysis. Results In the 25 patients who underwent the reduced-dose protocol, mean decrease in CTDIvol was 46% (range, 19%–65%) and mean decrease in SSDE was 44% (range, 19%–64%). Reduced-dose MBIR images had less noise (P > .004). Spatial resolution was superior for reduced-dose MBIR images. Reduced-dose MBIR images were equivalent to standard-dose images for lungs and soft tissues (P > .05) but were inferior for bones (P = .004). Reduced-dose 100% ASIR images were inferior for soft tissues (P ASIR. Conclusion CT performed with a reduced-dose protocol and MBIR is feasible in the pediatric population, and it maintains diagnostic quality. © RSNA, 2013 Online supplemental material is available for this article. PMID:24091359

  6. Fan beam image reconstruction with generalized Fourier slice theorem.

    Science.gov (United States)

    Zhao, Shuangren; Yang, Kang; Yang, Kevin

    2014-01-01

    For parallel beam geometry the Fourier reconstruction works via the Fourier slice theorem (or central slice theorem, projection slice theorem). For fan beam situation, Fourier slice can be extended to a generalized Fourier slice theorem (GFST) for fan-beam image reconstruction. We have briefly introduced this method in a conference. This paper reintroduces the GFST method for fan beam geometry in details. The GFST method can be described as following: the Fourier plane is filled by adding up the contributions from all fanbeam projections individually; thereby the values in the Fourier plane are directly calculated for Cartesian coordinates such avoiding the interpolation from polar to Cartesian coordinates in the Fourier domain; inverse fast Fourier transform is applied to the image in Fourier plane and leads to a reconstructed image in spacial domain. The reconstructed image is compared between the result of the GFST method and the result from the filtered backprojection (FBP) method. The major differences of the GFST and the FBP methods are: (1) The interpolation process are at different data sets. The interpolation of the GFST method is at projection data. The interpolation of the FBP method is at filtered projection data. (2) The filtering process are done in different places. The filtering process of the GFST is at Fourier domain. The filtering process of the FBP method is the ramp filter which is done at projections. The resolution of ramp filter is variable with different location but the filter in the Fourier domain lead to resolution invariable with location. One advantage of the GFST method over the FBP method is in short scan situation, an exact solution can be obtained with the GFST method, but it can not be obtained with the FBP method. The calculation of both the GFST and the FBP methods are at O(N^3), where N is the number of pixel in one dimension.

  7. Dose-reduced CT with model-based iterative reconstruction in evaluations of hepatic steatosis: How low can we go?

    Energy Technology Data Exchange (ETDEWEB)

    Yasaka, Koichiro, E-mail: koyasaka@gmail.com [Department of Radiology, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655 (Japan); Katsura, Masaki [Department of Radiology, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655 (Japan); Akahane, Masaaki [NTT Medical Center Tokyo, 5-9-22 Higashi-Gotanda, Shinagawa-ku, Tokyo 141-8625 (Japan); Sato, Jiro [Department of Radiology, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655 (Japan); Matsuda, Izuru [Kanto Rosai Hospital, 1-1 Kizukisumiyoshi-cho, Nakahara-ku, Kawasaki, Kanagawa 211-8510 (Japan); Ohtomo, Kuni [Department of Radiology, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655 (Japan)

    2014-07-15

    Purpose: To determine whether dose-reduced CT with model-based iterative image reconstruction (MBIR) is a useful tool with which to diagnose hepatic steatosis. Materials and methods: This prospective clinical study approved by our Institutional Review Board included 103 (67 men and 36 women; mean age, 64.3 years) patients who provided written informed consent to undergo unenhanced CT. Images of reference-dose CT (RDCT) with filtered back projection (R-FBP) and low- and ultralow-dose CT (dose-length product; 24 and 9% of that of RDCT) with MBIR (L-MBIR and UL-MBIR) were reconstructed. Mean CT numbers of liver (CT[L]) and spleen (CT[S]), and quotient (CT[L/S]) of CT[L] and CT[S] were calculated from selected regions of interest. Bias and limits of agreement (LOA) of CT[L] and CT[L/S] in L-MBIR and UL-MBIR (vs. R-FBP) were assessed using Bland–Altman analyses. Diagnostic methods for hepatic steatosis of CT[L] < 48 Hounsfield units (HU) and CT[L/S] < 1.1 were applied to L-MBIR and UL-MBIR using R-FBP as the reference standard. Results: Bias was larger for CT[L] in UL-MBIR than in L-MBIR (−3.18 HU vs. −1.73 HU). The LOA of CT[L/S] was larger for UL-MBIR than for L-MBIR (±0.425 vs. ±0.245) and outliers were identified in CT[L/S] of UL-MBIR. Accuracy (0.92–0.95) and the area under the receiver operating characteristics curve (0.976–0.992) were high for each method, but some were slightly lower in UL-MBIR than L-MBIR. Conclusion: Dose-reduced CT reconstructed with MBIR is applicable to diagnose hepatic steatosis, however, a low dose of radiation might be preferable.

  8. MO-DE-207A-01: Impact of Statistical Weights On Detection of Low-Contrast Details in Model-Based Iterative CT Reconstruction

    Energy Technology Data Exchange (ETDEWEB)

    Noo, F; Guo, Z [University of Utah, Salt Lake City, UT (United States)

    2016-06-15

    Purpose: Penalized-weighted least-square reconstruction has become an important research topic in CT, to reduce dose without affecting image quality. Two components impact image quality in this reconstruction: the statistical weights and the use of an edge-preserving penalty term. We are interested in assessing the influence of statistical weights on their own, without the edge-preserving feature. Methods: The influence of statistical weights on image quality was assessed in terms of low-contrast detail detection using LROC analysis. The task amounted to detect and localize a 6-mm lesion with random contrast inside the FORBILD head phantom. A two-alternative forced-choice experiment was used with two human observers performing the task. Reconstructions without and with statistical weights were compared, both using the same quadratic penalty term. The beam energy was set to 30keV to amplify spatial differences in attenuation and thereby the role of statistical weights. A fan-beam data acquisition geometry was used. Results: Visual inspection of images clearly showed a difference in noise between the two reconstructions methods. As expected, the reconstruction without statistical weights exhibited noise streaks. The other reconstruction appeared better in this aspect, but presented other disturbing noise patterns and artifacts induced by the weights. The LROC analysis yield the following 95-percent confidence interval for the difference in reader-averaged AUC (reconstruction without weights minus reconstruction with weights): [0.0026,0.0599]. The mean AUC value was 0.9094. Conclusion: We have investigated the impact of statistical weights without the use of edge-preserving penalty in penalized weighted least-square reconstruction. A decrease rather than increase in image quality was observed when using statistical weights. Thus, the observers were better able to cope with the noise streaks than the noise patterns and artifacts induced by the statistical weights. It

  9. MO-DE-207A-01: Impact of Statistical Weights On Detection of Low-Contrast Details in Model-Based Iterative CT Reconstruction

    International Nuclear Information System (INIS)

    Noo, F; Guo, Z

    2016-01-01

    Purpose: Penalized-weighted least-square reconstruction has become an important research topic in CT, to reduce dose without affecting image quality. Two components impact image quality in this reconstruction: the statistical weights and the use of an edge-preserving penalty term. We are interested in assessing the influence of statistical weights on their own, without the edge-preserving feature. Methods: The influence of statistical weights on image quality was assessed in terms of low-contrast detail detection using LROC analysis. The task amounted to detect and localize a 6-mm lesion with random contrast inside the FORBILD head phantom. A two-alternative forced-choice experiment was used with two human observers performing the task. Reconstructions without and with statistical weights were compared, both using the same quadratic penalty term. The beam energy was set to 30keV to amplify spatial differences in attenuation and thereby the role of statistical weights. A fan-beam data acquisition geometry was used. Results: Visual inspection of images clearly showed a difference in noise between the two reconstructions methods. As expected, the reconstruction without statistical weights exhibited noise streaks. The other reconstruction appeared better in this aspect, but presented other disturbing noise patterns and artifacts induced by the weights. The LROC analysis yield the following 95-percent confidence interval for the difference in reader-averaged AUC (reconstruction without weights minus reconstruction with weights): [0.0026,0.0599]. The mean AUC value was 0.9094. Conclusion: We have investigated the impact of statistical weights without the use of edge-preserving penalty in penalized weighted least-square reconstruction. A decrease rather than increase in image quality was observed when using statistical weights. Thus, the observers were better able to cope with the noise streaks than the noise patterns and artifacts induced by the statistical weights. It

  10. TH-EF-207A-04: A Dynamic Contrast Enhanced Cone Beam CT Technique for Evaluation of Renal Functions

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Z; Shi, J; Yang, Y [University of Miami School of Medicine, Miami, FL (United States)

    2016-06-15

    Purpose: To develop a simple but robust method for the early detection and evaluation of renal functions using dynamic contrast enhanced cone beam CT technique. Methods: Experiments were performed on an integrated imaging and radiation research platform developed by our lab. Animals (n=3) were anesthetized with 20uL Ketamine/Xylazine cocktail, and then received 200uL injection of iodinated contrast agent Iopamidol via tail vein. Cone beam CT was acquired following contrast injection once per minute and up to 25 minutes. The cone beam CT was reconstructed with a dimension of 300×300×800 voxels of 130×130×130um voxel resolution. The middle kidney slices in the transvers and coronal planes were selected for image analysis. A double exponential function was used to fit the contrast enhanced signal intensity versus the time after contrast injection. Both pixel-based and region of interest (ROI)-based curve fitting were performed. Four parameters obtained from the curve fitting, namely the amplitude and flow constant for both contrast wash in and wash out phases, were investigated for further analysis. Results: Robust curve fitting was demonstrated for both pixel based (with R{sup 2}>0.8 for >85% pixels within the kidney contour) and ROI based (R{sup 2}>0.9 for all regions) analysis. Three different functional regions: renal pelvis, medulla and cortex, were clearly differentiated in the functional parameter map in the pixel based analysis. ROI based analysis showed the half-life T1/2 for contrast wash in and wash out phases were 0.98±0.15 and 17.04±7.16, 0.63±0.07 and 17.88±4.51, and 1.48±0.40 and 10.79±3.88 minutes for the renal pelvis, medulla and cortex, respectively. Conclusion: A robust method based on dynamic contrast enhanced cone beam CT and double exponential curve fitting has been developed to analyze the renal functions for different functional regions. Future study will be performed to investigate the sensitivity of this technique in the detection

  11. Neutron CT with a multi-detector system leading to drastical reduction of the measuring time

    International Nuclear Information System (INIS)

    Hehn, G.; Pfister, G.; Schatz, A.; Goebel, J.; Kofler, R.

    1993-09-01

    By means of numerical simulation methods and their verification with measurements it could be shown that such a detector system can be realized for a line beam and 1-2 detectors per cm. With the maximum available beam width of the fast neutron field at the FRM approximately 20 detectors can be used leading to a reduction of the measuring time to 0,5 - 1 hour. A multi detector system for a line beam of thermal neutrons was constructed, tested and used for CT-measurements. This detector system for the measurement of thinner layers with better spatial resolution could be realized. The electronic discrimination between neutrons and gamma rays has been improved. This discrimination was used in all CT-measurements to get transmission values of both kinds of radiation and to reconstruct to complementary CT-images. The use of a polyenergetic radiation causes spectral shifts in the transmission spectrum leading to artifacts in the reconstructed CT-image. The transmission values must be spectral corrected before image reconstruction, because the image artifacts complicate the image evaluation or make it impossible. A new energy selective procedure for the online spectral correction was developed. This method is based on the concept to measure additionally to the integral transmission value his pulse height spectrum and to do the correction depending on the changes in this pulse height spectrum. (orig./HP) [de

  12. Light-sheet generation in inhomogeneous media using self-reconstructing beams and the STED-principle.

    Science.gov (United States)

    Gohn-Kreuz, Cristian; Rohrbach, Alexander

    2016-03-21

    Self-reconstruction of Bessel beams in inhomogeneous media is beneficial in light-sheet based microscopy. Although the beam's ring system enables propagation stability, the resulting image contrast is reduced. Here, we show that by a combination of two self-reconstructing beams with different orbital angular momenta it is possible to inhibit fluorescence from the ring system by using stimulated emission depletion (STED) even in strongly scattering media. Our theoretical study shows that the remaining fluorescence γ depends non-linearly on the beams' relative radial and orbital angular momenta. For various scattering media we demonstrate that γ remains remarkably stable over long beam propagation distances.

  13. Reducing Radiation Dose in Adult Head CT using Iterative Reconstruction - A Clinical Study in 177 Patients.

    Science.gov (United States)

    Kaul, D; Kahn, J; Huizing, L; Wiener, E; Grupp, U; Böning, G; Ghadjar, P; Renz, D M; Streitparth, F

    2016-02-01

    To assess how ASIR (adaptive statistical iterative reconstruction) contributes to dose reduction and affects image quality of non-contrast cranial computed tomography (cCT). Non-contrast emergency CT scans of the head acquired in 177 patients were evaluated. The scans were acquired and processed using four different protocols: Group A (control): 120 kV, FBP (filtered back projection) n = 71; group B1: 120 kV, scan and reconstruction performed with 20 % ASIR (blending of 20 % ASIR and 80 % FBP), n = 86; group B2: raw data from group B1 reconstructed using a blending of 40 % ASIR and 60 % FBP, n = 74; group C1: 120 kV, scan and reconstruction performed with 30 % ASIR, n = 20; group C2: raw data from group C1 reconstructed using a blending of 50 % ASIR and 50 % FBP, n = 20. The effective dose was calculated. Image quality was assessed quantitatively and qualitatively. Compared to group A, groups B1/2 and C1/2 showed a significantly reduced effective dose of 40.4 % and 73.3 % (p ASIR makes it possible to reduce radiation significantly while maintaining adequate image quality in non-contrast head CT, which may be particularly useful for younger patients in an emergency setting and in follow-up. ASIR may reduce radiation significantly while maintaining adequate image quality. cCT protocol with 20 % ASIR and 40 %ASIR/60 %FBP blending is adequate for everyday clinical use. cCT protocol with 30 % ASIR and 50 %ASIR/50 %FBP blending is adequate for follow-up imaging © Georg Thieme Verlag KG Stuttgart · New York.

  14. Respiratory correlated cone beam CT

    International Nuclear Information System (INIS)

    Sonke, Jan-Jakob; Zijp, Lambert; Remeijer, Peter; Herk, Marcel van

    2005-01-01

    A cone beam computed tomography (CBCT) scanner integrated with a linear accelerator is a powerful tool for image guided radiotherapy. Respiratory motion, however, induces artifacts in CBCT, while the respiratory correlated procedures, developed to reduce motion artifacts in axial and helical CT are not suitable for such CBCT scanners. We have developed an alternative respiratory correlated procedure for CBCT and evaluated its performance. This respiratory correlated CBCT procedure consists of retrospective sorting in projection space, yielding subsets of projections that each corresponds to a certain breathing phase. Subsequently, these subsets are reconstructed into a four-dimensional (4D) CBCT dataset. The breathing signal, required for respiratory correlation, was directly extracted from the 2D projection data, removing the need for an additional respiratory monitor system. Due to the reduced number of projections per phase, the contrast-to-noise ratio in a 4D scan reduced by a factor 2.6-3.7 compared to a 3D scan based on all projections. Projection data of a spherical phantom moving with a 3 and 5 s period with and without simulated breathing irregularities were acquired and reconstructed into 3D and 4D CBCT datasets. The positional deviations of the phantoms center of gravity between 4D CBCT and fluoroscopy were small: 0.13±0.09 mm for the regular motion and 0.39±0.24 mm for the irregular motion. Motion artifacts, clearly present in the 3D CBCT datasets, were substantially reduced in the 4D datasets, even in the presence of breathing irregularities, such that the shape of the moving structures could be identified more accurately. Moreover, the 4D CBCT dataset provided information on the 3D trajectory of the moving structures, absent in the 3D data. Considerable breathing irregularities, however, substantially reduces the image quality. Data presented for three different lung cancer patients were in line with the results obtained from the phantom study. In

  15. Propagation stability of self-reconstructing Bessel beams enables contrast-enhanced imaging in thick media.

    Science.gov (United States)

    Fahrbach, Florian O; Rohrbach, Alexander

    2012-01-17

    Laser beams that can self-reconstruct their initial beam profile even in the presence of massive phase perturbations are able to propagate deeper into inhomogeneous media. This ability has crucial advantages for light sheet-based microscopy in thick media, such as cell clusters, embryos, skin or brain tissue or plants, as well as scattering synthetic materials. A ring system around the central intensity maximum of a Bessel beam enables its self-reconstruction, but at the same time illuminates out-of-focus regions and deteriorates image contrast. Here we present a detection method that minimizes the negative effect of the ring system. The beam's propagation stability along one straight line enables the use of a confocal line principle, resulting in a significant increase in image contrast. The axial resolution could be improved by nearly 100% relative to the standard light-sheet techniques using scanned Gaussian beams, while demonstrating self-reconstruction also for high propagation depths.

  16. LBP-based penalized weighted least-squares approach to low-dose cone-beam computed tomography reconstruction

    Science.gov (United States)

    Ma, Ming; Wang, Huafeng; Liu, Yan; Zhang, Hao; Gu, Xianfeng; Liang, Zhengrong

    2014-03-01

    Cone-beam computed tomography (CBCT) has attracted growing interest of researchers in image reconstruction. The mAs level of the X-ray tube current, in practical application of CBCT, is mitigated in order to reduce the CBCT dose. The lowering of the X-ray tube current, however, results in the degradation of image quality. Thus, low-dose CBCT image reconstruction is in effect a noise problem. To acquire clinically acceptable quality of image, and keep the X-ray tube current as low as achievable in the meanwhile, some penalized weighted least-squares (PWLS)-based image reconstruction algorithms have been developed. One representative strategy in previous work is to model the prior information for solution regularization using an anisotropic penalty term. To enhance the edge preserving and noise suppressing in a finer scale, a novel algorithm combining the local binary pattern (LBP) with penalized weighted leastsquares (PWLS), called LBP-PWLS-based image reconstruction algorithm, is proposed in this work. The proposed LBP-PWLS-based algorithm adaptively encourages strong diffusion on the local spot/flat region around a voxel and less diffusion on edge/corner ones by adjusting the penalty for cost function, after the LBP is utilized to detect the region around the voxel as spot, flat and edge ones. The LBP-PWLS-based reconstruction algorithm was evaluated using the sinogram data acquired by a clinical CT scanner from the CatPhan® 600 phantom. Experimental results on the noiseresolution tradeoff measurement and other quantitative measurements demonstrated its feasibility and effectiveness in edge preserving and noise suppressing in comparison with a previous PWLS reconstruction algorithm.

  17. Five-dimensional motion compensation for respiratory and cardiac motion with cone-beam CT of the thorax region

    Science.gov (United States)

    Sauppe, Sebastian; Hahn, Andreas; Brehm, Marcus; Paysan, Pascal; Seghers, Dieter; Kachelrieß, Marc

    2016-03-01

    We propose an adapted method of our previously published five-dimensional (5D) motion compensation (MoCo) algorithm1, developed for micro-CT imaging of small animals, to provide for the first time motion artifact-free 5D cone-beam CT (CBCT) images from a conventional flat detector-based CBCT scan of clinical patients. Image quality of retrospectively respiratory- and cardiac-gated volumes from flat detector CBCT scans is deteriorated by severe sparse projection artifacts. These artifacts further complicate motion estimation, as it is required for MoCo image reconstruction. For high quality 5D CBCT images at the same x-ray dose and the same number of projections as todays 3D CBCT we developed a double MoCo approach based on motion vector fields (MVFs) for respiratory and cardiac motion. In a first step our already published four-dimensional (4D) artifact-specific cyclic motion-compensation (acMoCo) approach is applied to compensate for the respiratory patient motion. With this information a cyclic phase-gated deformable heart registration algorithm is applied to the respiratory motion-compensated 4D CBCT data, thus resulting in cardiac MVFs. We apply these MVFs on double-gated images and thereby respiratory and cardiac motion-compensated 5D CBCT images are obtained. Our 5D MoCo approach processing patient data acquired with the TrueBeam 4D CBCT system (Varian Medical Systems). Our double MoCo approach turned out to be very efficient and removed nearly all streak artifacts due to making use of 100% of the projection data for each reconstructed frame. The 5D MoCo patient data show fine details and no motion blurring, even in regions close to the heart where motion is fastest.

  18. An analytical reconstruction model of the spread-out Bragg peak using laser-accelerated proton beams.

    Science.gov (United States)

    Tao, Li; Zhu, Kun; Zhu, Jungao; Xu, Xiaohan; Lin, Chen; Ma, Wenjun; Lu, Haiyang; Zhao, Yanying; Lu, Yuanrong; Chen, Jia-Er; Yan, Xueqing

    2017-07-07

    With the development of laser technology, laser-driven proton acceleration provides a new method for proton tumor therapy. However, it has not been applied in practice because of the wide and decreasing energy spectrum of laser-accelerated proton beams. In this paper, we propose an analytical model to reconstruct the spread-out Bragg peak (SOBP) using laser-accelerated proton beams. Firstly, we present a modified weighting formula for protons of different energies. Secondly, a theoretical model for the reconstruction of SOBPs with laser-accelerated proton beams has been built. It can quickly calculate the number of laser shots needed for each energy interval of the laser-accelerated protons. Finally, we show the 2D reconstruction results of SOBPs for laser-accelerated proton beams and the ideal situation. The final results show that our analytical model can give an SOBP reconstruction scheme that can be used for actual tumor therapy.

  19. Coronary artery plaques: Cardiac CT with model-based and adaptive-statistical iterative reconstruction technique

    International Nuclear Information System (INIS)

    Scheffel, Hans; Stolzmann, Paul; Schlett, Christopher L.; Engel, Leif-Christopher; Major, Gyöngi Petra; Károlyi, Mihály; Do, Synho; Maurovich-Horvat, Pál; Hoffmann, Udo

    2012-01-01

    Objectives: To compare image quality of coronary artery plaque visualization at CT angiography with images reconstructed with filtered back projection (FBP), adaptive statistical iterative reconstruction (ASIR), and model based iterative reconstruction (MBIR) techniques. Methods: The coronary arteries of three ex vivo human hearts were imaged by CT and reconstructed with FBP, ASIR and MBIR. Coronary cross-sectional images were co-registered between the different reconstruction techniques and assessed for qualitative and quantitative image quality parameters. Readers were blinded to the reconstruction algorithm. Results: A total of 375 triplets of coronary cross-sectional images were co-registered. Using MBIR, 26% of the images were rated as having excellent overall image quality, which was significantly better as compared to ASIR and FBP (4% and 13%, respectively, all p < 0.001). Qualitative assessment of image noise demonstrated a noise reduction by using ASIR as compared to FBP (p < 0.01) and further noise reduction by using MBIR (p < 0.001). The contrast-to-noise-ratio (CNR) using MBIR was better as compared to ASIR and FBP (44 ± 19, 29 ± 15, 26 ± 9, respectively; all p < 0.001). Conclusions: Using MBIR improved image quality, reduced image noise and increased CNR as compared to the other available reconstruction techniques. This may further improve the visualization of coronary artery plaque and allow radiation reduction.

  20. A fully three-dimensional reconstruction algorithm with the nonstationary filter for improved single-orbit cone beam SPECT

    International Nuclear Information System (INIS)

    Cao, Z.J.; Tsui, B.M.

    1993-01-01

    Conventional single-orbit cone beam tomography presents special problems. They include incomplete sampling and inadequate three-dimensional (3D) reconstruction algorithm. The commonly used Feldkamp reconstruction algorithm simply extends the two-dimensional (2D) fan beam algorithm to 3D cone beam geometry. A truly 3D reconstruction formulation has been derived for the single-orbit cone beam SPECT based on the 3D Fourier slice theorem. In the formulation, a nonstationary filter which depends on the distance from the central plane of the cone beam was derived. The filter is applied to the 2D projection data in directions along and normal to the axis-of-rotation. The 3D reconstruction algorithm with the nonstationary filter was evaluated using both computer simulation and experimental measurements. Significant improvement in image quality was demonstrated in terms of decreased artifacts and distortions in cone beam reconstructed images. However, compared with the Feldkamp algorithm, a five-fold increase in processing time is required. Further improvement in image quality needs complete sampling in frequency space

  1. Technical Note: Insertion of digital lesions in the projection domain for dual-source, dual-energy CT.

    Science.gov (United States)

    Ferrero, Andrea; Chen, Baiyu; Li, Zhoubo; Yu, Lifeng; McCollough, Cynthia

    2017-05-01

    To compare algorithms performing material decomposition and classification in dual-energy CT, it is desirable to know the ground truth of the lesion to be analyzed in real patient data. In this work, we developed and validated a framework to insert digital lesions of arbitrary chemical composition into patient projection data acquired on a dual-source, dual-energy CT system. A model that takes into account beam-hardening effects was developed to predict the CT number of objects with known chemical composition. The model utilizes information about the x-ray energy spectra, the patient/phantom attenuation, and the x-ray detector energy response. The beam-hardening model was validated on samples of iodine (I) and calcium (Ca) for a second-generation dual-source, dual-energy CT scanner for all tube potentials available and a wide range of patient sizes. The seven most prevalent mineral components of renal stones were modeled and digital stones were created with CT numbers computed for each patient/phantom size and x-ray energy spectra using the developed beam-hardening model. Each digital stone was inserted in the dual-energy projection data of a water phantom scanned on a dual-source scanner and reconstructed with the routine algorithms in use in our practice. The geometry of the forward projection for dual-energy data was validated by comparing CT number accuracy and high-contrast resolution of simulated dual-energy CT data of the ACR phantom with experimentally acquired data. The beam-hardening model and forward projection method accurately predicted the CT number of I and Ca over a wide range of tube potentials and phantom sizes. The images reconstructed after the insertion of digital kidney stones were consistent with the images reconstructed from the scanner, and the CT number ratios for different kidney stone types were consistent with data in the literature. A sample application of the proposed tool was also demonstrated. A framework was developed and validated

  2. Validation of a computer modelled forensic facial reconstruction technique using CT data from live subjects: a pilot study.

    Science.gov (United States)

    Short, Laura J; Khambay, Balvinder; Ayoub, Ashraf; Erolin, Caroline; Rynn, Chris; Wilkinson, Caroline

    2014-04-01

    Human forensic facial soft tissue reconstructions are used when post-mortem deterioration makes identification difficult by usual means. The aim is to trigger recognition of the in vivo countenance of the individual by a friend or family member. A further use is in the field of archaeology. There are a number of different methods that can be applied to complete the facial reconstruction, ranging from two dimensional drawings, three dimensional clay models and now, with the advances of three dimensional technology, three dimensional computerised modelling. Studies carried out to assess the accuracy of facial reconstructions have produced variable results over the years. Advances in three dimensional imaging techniques in the field of oral and maxillofacial surgery, particularly cone beam computed tomography (CBCT), now provides an opportunity to utilise the data of live subjects and assess the accuracy of the three dimensional computerised facial reconstruction technique. The aim of this study was to assess the accuracy of a computer modelled facial reconstruction technique using CBCT data from live subjects. This retrospective pilot study was carried out at the Glasgow Dental Hospital Orthodontic Department and the Centre of Anatomy and Human Identification, Dundee University School of Life Sciences. Ten patients (5 male and 5 female; mean age 23 years) with mild skeletal discrepancies with pre-surgical cone beam CT data (CBCT) were included in this study. The actual and forensic reconstruction soft tissues were analysed using 3D software to look at differences between landmarks, linear and angular measurements and surface meshes. There were no statistical differences for 18 out of the 23 linear and 7 out of 8 angular measurements between the reconstruction and the target (p<0.05). The use of Procrustes superimposition has highlighted potential problems with soft tissue depth and anatomical landmarks' position. Surface mesh analysis showed that this virtual

  3. Practical reconstruction protocol for quantitative 90Y bremsstrahlung SPECT/CT

    International Nuclear Information System (INIS)

    Siman, W.; Mikell, J. K.; Kappadath, S. C.

    2016-01-01

    Purpose: To develop a practical background compensation (BC) technique to improve quantitative 90 Y-bremsstrahlung single-photon emission computed tomography (SPECT)/computed tomography (CT) using a commercially available imaging system. Methods: All images were acquired using medium-energy collimation in six energy windows (EWs), ranging from 70 to 410 keV. The EWs were determined based on the signal-to-background ratio in planar images of an acrylic phantom of different thicknesses (2–16 cm) positioned below a 90 Y source and set at different distances (15–35 cm) from a gamma camera. The authors adapted the widely used EW-based scatter-correction technique by modeling the BC as scaled images. The BC EW was determined empirically in SPECT/CT studies using an IEC phantom based on the sphere activity recovery and residual activity in the cold lung insert. The scaling factor was calculated from 20 clinical planar 90 Y images. Reconstruction parameters were optimized in the same SPECT images for improved image quantification and contrast. A count-to-activity calibration factor was calculated from 30 clinical 90 Y images. Results: The authors found that the most appropriate imaging EW range was 90–125 keV. BC was modeled as 0.53× images in the EW of 310–410 keV. The background-compensated clinical images had higher image contrast than uncompensated images. The maximum deviation of their SPECT calibration in clinical studies was lowest (<10%) for SPECT with attenuation correction (AC) and SPECT with AC + BC. Using the proposed SPECT-with-AC + BC reconstruction protocol, the authors found that the recovery coefficient of a 37-mm sphere (in a 10-mm volume of interest) increased from 39% to 90% and that the residual activity in the lung insert decreased from 44% to 14% over that of SPECT images with AC alone. Conclusions: The proposed EW-based BC model was developed for 90 Y bremsstrahlung imaging. SPECT with AC + BC gave improved lesion detectability and activity

  4. The effects of slice thickness and reconstructive parameters on VR image quality in multi-slice CT

    International Nuclear Information System (INIS)

    Gao Zhenlong; Wang Qiang; Liu Caixia

    2005-01-01

    Objective: To explore the effects of slice thickness, reconstructive thickness and reconstructive interval on VR image quality in multi-slice CT, in order to select the best slice thickness and reconstructive parameters for the imaging. Methods: Multi-slice CT scan was applied on a rubber dinosaur model with different slice thickness. VR images were reconstructed with different reconstructive thickness and reconstructive interval. Five radiologists were invited to evaluate the quality of the images without knowing anything about the parameters. Results: The slice thickness, reconstructive thickness and reconstructive interval did have effects on VR image quality and the effective degree was different. The effective coefficients were V 1 =1413.033, V 2 =563.733, V 3 =390.533, respectively. The parameters interacted with the others (P<0.05). The smaller of those parameters, the better of the image quality. With a small slice thickness and a reconstructive slice equal to slice thickness, the image quality had no obvious difference when the reconstructive interval was 1/2, 1/3, 1/4 of the slice thickness. Conclusion: A relative small scan slice thickness, a reconstructive slice equal to slice thickness and a reconstructive interval 1/2 of the slice thickness should be selected for the best VR image quality. The image quality depends mostly on the slice thickness. (authors)

  5. Use of model-based iterative reconstruction (MBIR) in reduced-dose CT for routine follow-up of patients with malignant lymphoma: dose savings, image quality and phantom study

    International Nuclear Information System (INIS)

    Herin, Edouard; Chiaradia, Melanie; Cavet, Madeleine; Deux, Jean-Francois; Rahmouni, Alain; Gardavaud, Francois; Beaussart, Pauline; Richard, Philippe; Haioun, Corinne; Itti, Emmanuel; Luciani, Alain

    2015-01-01

    To evaluate both in vivo and in phantom studies, dose reduction, and image quality of body CT reconstructed with model-based iterative reconstruction (MBIR), performed during patient follow-ups for lymphoma. This study included 40 patients (mean age 49 years) with lymphoma. All underwent reduced-dose CT during follow-up, reconstructed using MBIR or 50 % advanced statistical iterative reconstruction (ASIR). All had previously undergone a standard dose CT with filtered back projection (FBP) reconstruction. The volume CT dose index (CTDIvol), the density measures in liver, spleen, fat, air, and muscle, and the image quality (noise and signal to noise ratio, SNR) (ANOVA) observed using standard or reduced-dose CT were compared both in patients and a phantom study (Catphan 600) (Kruskal Wallis). The CTDIvol was decreased on reduced-dose body CT (4.06 mGy vs. 15.64 mGy p < 0.0001). SNR was higher in reduced-dose CT reconstructed with MBIR than in 50 % ASIR or than standard dose CT with FBP (patients, p ≤ 0.01; phantoms, p = 0.003). Low contrast detectability and spatial resolution in phantoms were not altered on MBIR-reconstructed CT (p ≥ 0.11). Reduced-dose CT with MBIR reconstruction can decrease radiation dose delivered to patients with lymphoma, while keeping an image quality similar to that obtained on standard-dose CT. (orig.)

  6. Use of model-based iterative reconstruction (MBIR) in reduced-dose CT for routine follow-up of patients with malignant lymphoma: dose savings, image quality and phantom study

    Energy Technology Data Exchange (ETDEWEB)

    Herin, Edouard; Chiaradia, Melanie; Cavet, Madeleine; Deux, Jean-Francois; Rahmouni, Alain [AP-HP, Hopitaux Universitaires Henri Mondor, Imagerie Medicale, Creteil (France); Universite Paris Est Creteil, Faculte de Medecine, Creteil (France); Gardavaud, Francois; Beaussart, Pauline [AP-HP, Hopitaux Universitaires Henri Mondor, Imagerie Medicale, Creteil (France); Richard, Philippe [GE Healthcare France, Buc (France); Haioun, Corinne [Universite Paris Est Creteil, Faculte de Medecine, Creteil (France); AP-HP, Hopitaux Universitaires Henri Mondor, Hemopathies Lymphoides, Creteil (France); Itti, Emmanuel [Universite Paris Est Creteil, Faculte de Medecine, Creteil (France); AP-HP, Hopitaux Universitaires Henri Mondor, Medecine Nucleaire, Creteil (France); Luciani, Alain [AP-HP, Hopitaux Universitaires Henri Mondor, Imagerie Medicale, Creteil (France); Universite Paris Est Creteil, Faculte de Medecine, Creteil (France); INSERM Unite U 955, Creteil (France); AP-HP, Groupe Henri Mondor Albert Chenevier, Imagerie Medicale, CHU Henri Mondor, Creteil Cedex (France)

    2015-08-15

    To evaluate both in vivo and in phantom studies, dose reduction, and image quality of body CT reconstructed with model-based iterative reconstruction (MBIR), performed during patient follow-ups for lymphoma. This study included 40 patients (mean age 49 years) with lymphoma. All underwent reduced-dose CT during follow-up, reconstructed using MBIR or 50 % advanced statistical iterative reconstruction (ASIR). All had previously undergone a standard dose CT with filtered back projection (FBP) reconstruction. The volume CT dose index (CTDIvol), the density measures in liver, spleen, fat, air, and muscle, and the image quality (noise and signal to noise ratio, SNR) (ANOVA) observed using standard or reduced-dose CT were compared both in patients and a phantom study (Catphan 600) (Kruskal Wallis). The CTDIvol was decreased on reduced-dose body CT (4.06 mGy vs. 15.64 mGy p < 0.0001). SNR was higher in reduced-dose CT reconstructed with MBIR than in 50 % ASIR or than standard dose CT with FBP (patients, p ≤ 0.01; phantoms, p = 0.003). Low contrast detectability and spatial resolution in phantoms were not altered on MBIR-reconstructed CT (p ≥ 0.11). Reduced-dose CT with MBIR reconstruction can decrease radiation dose delivered to patients with lymphoma, while keeping an image quality similar to that obtained on standard-dose CT. (orig.)

  7. Radiation Dose Reduction of Chest CT with Iterative Reconstruction in Image Space - Part I: Studies on Image Quality Using Dual Source CT

    International Nuclear Information System (INIS)

    Hwang, Hye Jeon; Seo, Joon Beom; Lee, Jin Seong; Song, Jae Woo; Lee, Hyun Joo; Lim, Chae Hun; Kim, Song Soo

    2012-01-01

    To determine whether the image quality (IQ) is improved with iterative reconstruction in image space (IRIS), and whether IRIS can be used for radiation reduction in chest CT. Standard dose chest CT (SDCT) in 50 patients and low dose chest CT (LDCT) in another 50 patients were performed, using a dual-source CT, with 120 kVp and same reference mAs (50 mAs for SDCT and 25 mAs for LDCT) employed to both tubes by modifying a dual-energy scan mode. Full-dose data were obtained by combining the data from both tubes and half-dose data were separated from a single tube. These were reconstructed by using a filtered back projection (FBP) and IRIS: full-dose FBP (F-FBP); full-dose IRIS (F-IRIS); half-dose FBP (H-FBP) and half-dose IRIS (H-IRIS). Objective noise was measured. The subjective IQ was evaluated by radiologists for the followings: noise, contrast and sharpness of mediastinum and lung. Objective noise was significantly lower in H-IRIS than in F-FBP (p < 0.01). In both SDCT and LDCT, the IQ scores were highest in F-IRIS, followed by F-FBP, H-IRIS and H-FBP, except those for sharpness of mediastinum, which tended to be higher in FBP. When comparing CT images between the same dose and different reconstruction (F-IRIS/F-FBP and H-IRIS/H-FBP) algorithms, scores tended to be higher in IRIS than in FBP, being more distinct in half-dose images. However, despite the use of IRIS, the scores were lower in H-IRIS than in F-FBP. IRIS generally helps improve the IQ, being more distinct at the reduced radiation. However, reduced radiation by half results in IQ decrease even when using IRIS in chest CT.

  8. Experimental validation of incomplete data CT image reconstruction techniques

    International Nuclear Information System (INIS)

    Eberhard, J.W.; Hsiao, M.L.; Tam, K.C.

    1989-01-01

    X-ray CT inspection of large metal parts is often limited by x-ray penetration problems along many of the ray paths required for a complete CT data set. In addition, because of the complex geometry of many industrial parts, manipulation difficulties often prevent scanning over some range of angles. CT images reconstructed from these incomplete data sets contain a variety of artifacts which limit their usefulness in part quality determination. Over the past several years, the authors' company has developed 2 new methods of incorporating a priori information about the parts under inspection to significantly improve incomplete data CT image quality. This work reviews the methods which were developed and presents experimental results which confirm the effectiveness of the techniques. The new methods for dealing with incomplete CT data sets rely on a priori information from part blueprints (in electronic form), outer boundary information from touch sensors, estimates of part outer boundaries from available x-ray data, and linear x-ray attenuation coefficients of the part. The two methods make use of this information in different fashions. The relative performance of the two methods in detecting various flaw types is compared. Methods for accurately registering a priori information with x-ray data are also described. These results are critical to a new industrial x-ray inspection cell built for inspection of large aircraft engine parts

  9. SU-F-J-74: High Z Geometric Integrity and Beam Hardening Artifact Assessment Using a Retrospective Metal Artifact Reduction (MAR) Reconstruction Algorithm

    Energy Technology Data Exchange (ETDEWEB)

    Woods, K; DiCostanzo, D; Gupta, N [Ohio State University Columbus, OH (United States)

    2016-06-15

    Purpose: To test the efficacy of a retrospective metal artifact reduction (MAR) reconstruction algorithm for a commercial computed tomography (CT) scanner for radiation therapy purposes. Methods: High Z geometric integrity and artifact reduction analysis was performed with three phantoms using General Electric’s (GE) Discovery CT. The three phantoms included: a Computerized Imaging Reference Systems (CIRS) electron density phantom (Model 062) with a 6.5 mm diameter titanium rod insert, a custom spine phantom using Synthes Spine hardware submerged in water, and a dental phantom with various high Z fillings submerged in water. Each phantom was reconstructed using MAR and compared against the original scan. Furthermore, each scenario was tested using standard and extended Hounsfield Unit (HU) ranges. High Z geometric integrity was performed using the CIRS phantom, while the artifact reduction was performed using all three phantoms. Results: Geometric integrity of the 6.5 mm diameter rod was slightly overestimated for non-MAR scans for both standard and extended HU. With MAR reconstruction, the rod was underestimated for both standard and extended HU. For artifact reduction, the mean and standard deviation was compared in a volume of interest (VOI) in the surrounding material (water and water equivalent material, ∼0HU). Overall, the mean value of the VOI was closer to 0 HU for the MAR reconstruction compared to the non-MAR scan for most phantoms. Additionally, the standard deviations for all phantoms were greatly reduced using MAR reconstruction. Conclusion: GE’s MAR reconstruction algorithm improves image quality with the presence of high Z material with minimal degradation of its geometric integrity. High Z delineation can be carried out with proper contouring techniques. The effects of beam hardening artifacts are greatly reduced with MAR reconstruction. Tissue corrections due to these artifacts can be eliminated for simple high Z geometries and greatly

  10. SU-F-J-74: High Z Geometric Integrity and Beam Hardening Artifact Assessment Using a Retrospective Metal Artifact Reduction (MAR) Reconstruction Algorithm

    International Nuclear Information System (INIS)

    Woods, K; DiCostanzo, D; Gupta, N

    2016-01-01

    Purpose: To test the efficacy of a retrospective metal artifact reduction (MAR) reconstruction algorithm for a commercial computed tomography (CT) scanner for radiation therapy purposes. Methods: High Z geometric integrity and artifact reduction analysis was performed with three phantoms using General Electric’s (GE) Discovery CT. The three phantoms included: a Computerized Imaging Reference Systems (CIRS) electron density phantom (Model 062) with a 6.5 mm diameter titanium rod insert, a custom spine phantom using Synthes Spine hardware submerged in water, and a dental phantom with various high Z fillings submerged in water. Each phantom was reconstructed using MAR and compared against the original scan. Furthermore, each scenario was tested using standard and extended Hounsfield Unit (HU) ranges. High Z geometric integrity was performed using the CIRS phantom, while the artifact reduction was performed using all three phantoms. Results: Geometric integrity of the 6.5 mm diameter rod was slightly overestimated for non-MAR scans for both standard and extended HU. With MAR reconstruction, the rod was underestimated for both standard and extended HU. For artifact reduction, the mean and standard deviation was compared in a volume of interest (VOI) in the surrounding material (water and water equivalent material, ∼0HU). Overall, the mean value of the VOI was closer to 0 HU for the MAR reconstruction compared to the non-MAR scan for most phantoms. Additionally, the standard deviations for all phantoms were greatly reduced using MAR reconstruction. Conclusion: GE’s MAR reconstruction algorithm improves image quality with the presence of high Z material with minimal degradation of its geometric integrity. High Z delineation can be carried out with proper contouring techniques. The effects of beam hardening artifacts are greatly reduced with MAR reconstruction. Tissue corrections due to these artifacts can be eliminated for simple high Z geometries and greatly

  11. A fast and efficient method for sequential cone-beam tomography

    International Nuclear Information System (INIS)

    Koehler, Th.; Proksa, R.; Grass, M.

    2001-01-01

    Sequential cone-beam tomography is a method that uses data of two or more parallel circular trajectories of a cone-beam scanner to reconstruct the object function. We propose a condition for the data acquisition that ensures that all object points between two successive circles are irradiated over an angular span of the x-ray source position of exactly 360 deg. in total as seen along the rotation axis. A fast and efficient approximative reconstruction method for the proposed acquisition is presented which uses data from exactly 360 deg. for every object point. It is based on the Tent-FDK method which was recently developed for single circular cone-beam CT. The measurement geometry does not provide sufficient data for exact reconstruction but it is shown that the proposed reconstruction method provides satisfying image quality for small cone angles

  12. Reconstruction of cosmic and beam-halo muons with the CMS detector

    CERN Document Server

    Liu, Chang; Amapane, Nicola; Fernandez Bedoya, Cristina; Bellan, Riccardo; Biallass, Philipp; Bolognesi, Sara; Cerminara, Gianluca; Fouz Iglesias, Mary-Cruz; Giunta, Marina; Guiducci, Luigi; Hoepfner, Kerstin; Lacaprara, Stefano; Masetti, Gianni; Meneguzzo, Anna; Paolucci, Pierluigi; Puerta Pelayo, Jesus; Travaglini, Riccardo; Zanetti, Marco; Villanueva, Carlos

    2008-01-01

    The powerful muon and tracker systems of the CMS detector together with dedicated reconstruction software allow precise and efficient measurement of muon tracks originating from proton-proton collisions. The standard muon reconstruction algorithms, however, are inadequate to deal with muons that do not originate from collisions. This note discusses the design, implementation, and performance results of a dedicated cosmic muon track reconstruction algorithm, which features pattern recognition optimized for muons that are not coming from the interaction point, i.e., cosmic muons and beam-halo muons. To evaluate the performance of the new algorithm, data taken during Cosmic Challenge phases I and II were studied and compared with simulated cosmic data. In addition, a variety of more general topologies of cosmic muons and beam-halo muons were studied using simulated data to demonstrate some key features of the new algorithm.

  13. Poster — Thur Eve — 06: Dose assessment of cone beam CT imaging protocols as part of SPECT/CT examinations

    Energy Technology Data Exchange (ETDEWEB)

    Tonkopi, E; Ross, AA [Department of Diagnostic Imaging, Queen Elizabeth II Health Sciences Centre, CDHA (Canada); Department of Radiology, Dalhousie University (Canada)

    2014-08-15

    Purpose: To assess radiation dose from the cone beam CT (CBCT) component of SPECT/CT studies and to compare with other CT examinations performed in our institution. Methods: We used an anthropomorphic chest phantom and the 6 cc ion chamber to measure entrance breast dose for several CBCT and diagnostic CT acquisition protocols. The CBCT effective dose was calculated with ImPACT software; the CT effective dose was evaluated from the DLP value and conversion factor, dependent on the anatomic region. The RADAR medical procedure radiation dose calculator was used to assess the nuclear medicine component of exam dose. Results: The entrance dose to the breast measured with the anthropomorphic phantom was 0.48 mGy and 9.41 mGy for cardiac and chest CBCT scans; and 4.59 mGy for diagnostic thoracic CT. The effective doses were 0.2 mSv, 3.2 mSv and 2.8 mSv respectively. For a small patient represented by the anthropomorphic phantom, the dose from the diagnostic CT was lower than from the CBCT scan, as a result of the exposure reduction options available on modern CT scanners. The CBCT protocols used the same fixed scanning techniques. The diagnostic CT dose based on the patient data was 35% higher than the phantom dose. For most SPECT/CT studies the dose from the CBCT component was comparable with the dose from the radiopharmaceutical. Conclusions: The patient radiation dose from the cone beam CT scan can be higher than that from a diagnostic CT and should be taken into consideration in evaluating total SPECT/CT patient dose.

  14. CT image reconstruction system based on hardware implementation

    International Nuclear Information System (INIS)

    Silva, Hamilton P. da; Evseev, Ivan; Schelin, Hugo R.; Paschuk, Sergei A.; Milhoretto, Edney; Setti, Joao A.P.; Zibetti, Marcelo; Hormaza, Joel M.; Lopes, Ricardo T.

    2009-01-01

    Full text: The timing factor is very important for medical imaging systems, which can nowadays be synchronized by vital human signals, like heartbeats or breath. The use of hardware implemented devices in such a system has advantages considering the high speed of information treatment combined with arbitrary low cost on the market. This article refers to a hardware system which is based on electronic programmable logic called FPGA, model Cyclone II from ALTERA Corporation. The hardware was implemented on the UP3 ALTERA Kit. A partially connected neural network with unitary weights was programmed. The system was tested with 60 topographic projections, 100 points in each, of the Shepp and Logan phantom created by MATLAB. The main restriction was found to be the memory size available on the device: the dynamic range of reconstructed image was limited to 0 65535. Also, the normalization factor must be observed in order to do not saturate the image during the reconstruction and filtering process. The test shows a principal possibility to build CT image reconstruction systems for any reasonable amount of input data by arranging the parallel work of the hardware units like we have tested. However, further studies are necessary for better understanding of the error propagation from topographic projections to reconstructed image within the implemented method. (author)

  15. Comparison of the image qualities of filtered back-projection, adaptive statistical iterative reconstruction, and model-based iterative reconstruction for CT venography at 80 kVp

    International Nuclear Information System (INIS)

    Kim, Jin Hyeok; Choo, Ki Seok; Moon, Tae Yong; Lee, Jun Woo; Jeon, Ung Bae; Kim, Tae Un; Hwang, Jae Yeon; Yun, Myeong-Ja; Jeong, Dong Wook; Lim, Soo Jin

    2016-01-01

    To evaluate the subjective and objective qualities of computed tomography (CT) venography images at 80 kVp using model-based iterative reconstruction (MBIR) and to compare these with those of filtered back projection (FBP) and adaptive statistical iterative reconstruction (ASIR) using the same CT data sets. Forty-four patients (mean age: 56.1 ± 18.1) who underwent 80 kVp CT venography (CTV) for the evaluation of deep vein thrombosis (DVT) during 4 months were enrolled in this retrospective study. The same raw data were reconstructed using FBP, ASIR, and MBIR. Objective and subjective image analysis were performed at the inferior vena cava (IVC), femoral vein, and popliteal vein. The mean CNR of MBIR was significantly greater than those of FBP and ASIR and images reconstructed using MBIR had significantly lower objective image noise (p <.001). Subjective image quality and confidence of detecting DVT by MBIR group were significantly greater than those of FBP and ASIR (p <.005), and MBIR had the lowest score for subjective image noise (p <.001). CTV at 80 kVp with MBIR was superior to FBP and ASIR regarding subjective and objective image qualities. (orig.)

  16. Surgical stent for dental implant using cone beam CT images

    International Nuclear Information System (INIS)

    Choi, Hyung Soo; Kim, Gyu Tae; Choi, Yong Suk; Hwang, Eui Hwan

    2010-01-01

    The purpose of this study is to develop a surgical stent for dental implant procedure that can be easily applied and affordable by using cone beam computerized tomography (CBCT). Aluminum, Teflon-PFA (perfluoroalkoxy), and acetal (polyoxymethylene plastic) were selected as materials for the surgical stent. Among these three materials, the appropriate material was chosen using the CBCT images. The surgical stent, which could be easily placed into an oral cavity, was designed with chosen material. CBCT images of the new surgical stent on mandible were obtained using Alphard-3030 dental CT system (Asahi Roentgen Co., Ltd., Kyoto, Japan). The point of insertion was prescribed on the surgical stent with the multiplanar reconstruction software of OnDemand3D (CyberMed Inc., Seoul, Korea). Guide holes were made at the point of insertion on the surgical stent using newly designed guide jig. CBCT scans was taken for the second time to verify the accuracy of the newly designed surgical stent. Teflon-PFA showed radiologically excellent image characteristics for the surgical stent. High accuracy and reproducibility of implantation were confirmed with the surgical stent. The newly designed surgical stent can lead to the accurate implantation and achieve the clinically predictable result.

  17. Bone quality evaluation at dental implant site using multislice CT, micro-CT, and cone beam CT.

    Science.gov (United States)

    Parsa, Azin; Ibrahim, Norliza; Hassan, Bassam; van der Stelt, Paul; Wismeijer, Daniel

    2015-01-01

    The first purpose of this study was to analyze the correlation between bone volume fraction (BV/TV) and calibrated radiographic bone density Hounsfield units (HU) in human jaws, derived from micro-CT and multislice computed tomography (MSCT), respectively. The second aim was to assess the accuracy of cone beam computed tomography (CBCT) in evaluating trabecular bone density and microstructure using MSCT and micro-CT, respectively, as reference gold standards. Twenty partially edentulous human mandibular cadavers were scanned by three types of CT modalities: MSCT (Philips, Best, the Netherlands), CBCT (3D Accuitomo 170, J Morita, Kyoto, Japan), and micro-CT (SkyScan 1173, Kontich, Belgium). Image analysis was performed using Amira (v4.1, Visage Imaging Inc., Carlsbad, CA, USA), 3Diagnosis (v5.3.1, 3diemme, Cantu, Italy), Geomagic (studio(®) 2012, Morrisville, NC, USA), and CTAn (v1.11, SkyScan). MSCT, CBCT, and micro-CT scans of each mandible were matched to select the exact region of interest (ROI). MSCT HU, micro-CT BV/TV, and CBCT gray value and bone volume fraction of each ROI were derived. Statistical analysis was performed to assess the correlations between corresponding measurement parameters. Strong correlations were observed between CBCT and MSCT density (r = 0.89) and between CBCT and micro-CT BV/TV measurements (r = 0.82). Excellent correlation was observed between MSCT HU and micro-CT BV/TV (r = 0.91). However, significant differences were found between all comparisons pairs (P micro-CT BV/TV (P = 0.147). An excellent correlation exists between bone volume fraction and bone density as assessed on micro-CT and MSCT, respectively. This suggests that bone density measurements could be used to estimate bone microstructural parameters. A strong correlation also was found between CBCT gray values and BV/TV and their gold standards, suggesting the potential of this modality in bone quality assessment at implant site. © 2013 John Wiley & Sons A/S. Published by

  18. The use of adaptive statistical iterative reconstruction in pediatric head CT: a feasibility study.

    Science.gov (United States)

    Vorona, G A; Zuccoli, G; Sutcavage, T; Clayton, B L; Ceschin, R C; Panigrahy, A

    2013-01-01

    Iterative reconstruction techniques facilitate CT dose reduction; though to our knowledge, no group has explored using iterative reconstruction with pediatric head CT. Our purpose was to perform a feasibility study to assess the use of ASIR in a small group of pediatric patients undergoing head CT. An Alderson-Rando head phantom was scanned at decreasing 10% mA intervals relative to our standard protocol, and each study was then reconstructed at 10% ASIR intervals. An intracranial region of interest was consistently placed to estimate noise. Our ventriculoperitoneal shunt CT protocol was subsequently modified, and patients were scanned at 20% ASIR with approximately 20% mA reductions. ASIR studies were anonymously compared with older non-ASIR studies from the same patients by 2 attending pediatric neuroradiologists for diagnostic utility, sharpness, noise, and artifacts. The phantom study demonstrated similar noise at 100% mA/0% ASIR (3.9) and 80% mA/20% ASIR (3.7). Twelve pediatric patients were scanned at reduced dose at 20% ASIR. The average CTDI(vol) and DLP values of the 20% ASIR studies were 22.4 mGy and 338.4 mGy-cm, and for the non-ASIR studies, they were 28.8 mGy and 444.5 mGy-cm, representing statistically significant decreases in the CTDI(vol) (22.1%, P = .00007) and DLP (23.9%, P = .0005) values. There were no significant differences between the ASIR studies and non-ASIR studies with respect to diagnostic acceptability, sharpness, noise, or artifacts. Our findings suggest that 20% ASIR can provide approximately 22% dose reduction in pediatric head CT without affecting image quality.

  19. Appearance of bony lesions on 3-D CT reconstructions: a case study in variable renderings

    Science.gov (United States)

    Mankovich, Nicholas J.; White, Stuart C.

    1992-05-01

    This paper discusses conventional 3-D reconstruction for bone visualization and presents a case study to demonstrate the dangers of performing 3-D reconstructions without careful selection of the bone threshold. The visualization of midface bone lesions directly from axial CT images is difficult because of the complex anatomic relationships. Three-dimensional reconstructions made from the CT to provide graphic images showing lesions in relation to adjacent facial bones. Most commercially available 3-D image reconstruction requires that the radiologist or technologist identify a threshold image intensity value that can be used to distinguish bone from other tissues. Much has been made of the many disadvantages of this technique, but it continues as the predominant method in producing 3-D pictures for clinical use. This paper is intended to provide a clear demonstration for the physician of the caveats that should accompany 3-D reconstructions. We present a case of recurrent odontogenic keratocyst in the anterior maxilla where the 3-D reconstructions, made with different bone thresholds (windows), are compared to the resected specimen. A DMI 3200 computer was used to convert the scan data from a GE 9800 CT into a 3-D shaded surface image. Threshold values were assigned to (1) generate the most clinically pleasing image, (2) produce maximum theoretical fidelity (using the midpoint image intensity between average cortical bone and average soft tissue), and (3) cover stepped threshold intensities between these two methods. We compared the computer lesions with the resected specimen and noted measurement errors of up to 44 percent introduced by inappropriate bone threshold levels. We suggest clinically applicable standardization techniques in the 3-D reconstruction as well as cautionary language that should accompany the 3-D images.

  20. Integration of PET-CT and cone-beam CT for image-guided radiotherapy with high image quality and registration accuracy

    Science.gov (United States)

    Wu, T.-H.; Liang, C.-H.; Wu, J.-K.; Lien, C.-Y.; Yang, B.-H.; Huang, Y.-H.; Lee, J. J. S.

    2009-07-01

    Hybrid positron emission tomography-computed tomography (PET-CT) system enhances better differentiation of tissue uptake of 18F-fluorodeoxyglucose (18F-FDG) and provides much more diagnostic value in the non-small-cell lung cancer and nasopharyngeal carcinoma (NPC). In PET-CT, high quality CT images not only offer diagnostic value on anatomic delineation of the tissues but also shorten the acquisition time for attenuation correction (AC) compared with PET-alone imaging. The linear accelerators equipped with the X-ray cone-beam computed tomography (CBCT) imaging system for image-guided radiotherapy (IGRT) provides excellent verification on position setup error. The purposes of our study were to optimize the CT acquisition protocols of PET-CT and to integrate the PET-CT and CBCT for IGRT. The CT imaging parameters were modified in PET-CT for increasing the image quality in order to enhance the diagnostic value on tumour delineation. Reproducibility and registration accuracy via bone co-registration algorithm between the PET-CT and CBCT were evaluated by using a head phantom to simulate a head and neck treatment condition. Dose measurement in computed tomography dose index (CTDI) was also estimated. Optimization of the CT acquisition protocols of PET-CT was feasible in this study. Co-registration accuracy between CBCT and PET-CT on axial and helical modes was in the range of 1.06 to 2.08 and 0.99 to 2.05 mm, respectively. In our result, it revealed that the accuracy of the co-registration with CBCT on helical mode was more accurate than that on axial mode. Radiation doses in CTDI were 4.76 to 18.5 mGy and 4.83 to 18.79 mGy on axial and helical modes, respectively. Registration between PET-CT and CBCT is a state-of-the-art registration technology which could provide much information on diagnosis and accurate tumour contouring on radiotherapy while implementing radiotherapy procedures. This novelty technology of PET-CT and cone-beam CT integration for IGRT may have a

  1. Integration of PET-CT and cone-beam CT for image-guided radiotherapy with high image quality and registration accuracy

    International Nuclear Information System (INIS)

    Wu, T-H; Liang, C-H; Wu, J-K; Lien, C-Y; Yang, B-H; Lee, J J S; Huang, Y-H

    2009-01-01

    Hybrid positron emission tomography-computed tomography (PET-CT) system enhances better differentiation of tissue uptake of 18 F-fluorodeoxyglucose ( 18 F-FDG) and provides much more diagnostic value in the non-small-cell lung cancer and nasopharyngeal carcinoma (NPC). In PET-CT, high quality CT images not only offer diagnostic value on anatomic delineation of the tissues but also shorten the acquisition time for attenuation correction (AC) compared with PET-alone imaging. The linear accelerators equipped with the X-ray cone-beam computed tomography (CBCT) imaging system for image-guided radiotherapy (IGRT) provides excellent verification on position setup error. The purposes of our study were to optimize the CT acquisition protocols of PET-CT and to integrate the PET-CT and CBCT for IGRT. The CT imaging parameters were modified in PET-CT for increasing the image quality in order to enhance the diagnostic value on tumour delineation. Reproducibility and registration accuracy via bone co-registration algorithm between the PET-CT and CBCT were evaluated by using a head phantom to simulate a head and neck treatment condition. Dose measurement in computed tomography dose index (CTDI) was also estimated. Optimization of the CT acquisition protocols of PET-CT was feasible in this study. Co-registration accuracy between CBCT and PET-CT on axial and helical modes was in the range of 1.06 to 2.08 and 0.99 to 2.05 mm, respectively. In our result, it revealed that the accuracy of the co-registration with CBCT on helical mode was more accurate than that on axial mode. Radiation doses in CTDI were 4.76 to 18.5 mGy and 4.83 to 18.79 mGy on axial and helical modes, respectively. Registration between PET-CT and CBCT is a state-of-the-art registration technology which could provide much information on diagnosis and accurate tumour contouring on radiotherapy while implementing radiotherapy procedures. This novelty technology of PET-CT and cone-beam CT integration for IGRT may have a

  2. Influence of Ultra-Low-Dose and Iterative Reconstructions on the Visualization of Orbital Soft Tissues on Maxillofacial CT.

    Science.gov (United States)

    Widmann, G; Juranek, D; Waldenberger, F; Schullian, P; Dennhardt, A; Hoermann, R; Steurer, M; Gassner, E-M; Puelacher, W

    2017-08-01

    Dose reduction on CT scans for surgical planning and postoperative evaluation of midface and orbital fractures is an important concern. The purpose of this study was to evaluate the variability of various low-dose and iterative reconstruction techniques on the visualization of orbital soft tissues. Contrast-to-noise ratios of the optic nerve and inferior rectus muscle and subjective scores of a human cadaver were calculated from CT with a reference dose protocol (CT dose index volume = 36.69 mGy) and a subsequent series of low-dose protocols (LDPs I-4: CT dose index volume = 4.18, 2.64, 0.99, and 0.53 mGy) with filtered back-projection (FBP) and adaptive statistical iterative reconstruction (ASIR)-50, ASIR-100, and model-based iterative reconstruction. The Dunn Multiple Comparison Test was used to compare each combination of protocols (α = .05). Compared with the reference dose protocol with FBP, the following statistically significant differences in contrast-to-noise ratios were shown (all, P ≤ .012) for the following: 1) optic nerve: LDP-I with FBP; LDP-II with FBP and ASIR-50; LDP-III with FBP, ASIR-50, and ASIR-100; and LDP-IV with FBP, ASIR-50, and ASIR-100; and 2) inferior rectus muscle: LDP-II with FBP, LDP-III with FBP and ASIR-50, and LDP-IV with FBP, ASIR-50, and ASIR-100. Model-based iterative reconstruction showed the best contrast-to-noise ratio in all images and provided similar subjective scores for LDP-II. ASIR-50 had no remarkable effect, and ASIR-100, a small effect on subjective scores. Compared with a reference dose protocol with FBP, model-based iterative reconstruction may show similar diagnostic visibility of orbital soft tissues at a CT dose index volume of 2.64 mGy. Low-dose technology and iterative reconstruction technology may redefine current reference dose levels in maxillofacial CT. © 2017 by American Journal of Neuroradiology.

  3. Predicting factors for conversion from fluoroscopy guided Percutaneous transthoracic needle biopsy to cone-beam CT guided Percutaneous transthoracic needle biopsy

    International Nuclear Information System (INIS)

    Lee, Kang Ji; Han, Young Min; Jin, Gong Yong; Song, Ji Soo

    2015-01-01

    To evaluate the predicting factors for conversion from fluoroscopy guided percutaneous transthoracic needle biopsy (PTNB) to cone-beam CT guided PTNB. From January 2011 to December 2012, we retrospectively identified 38 patients who underwent cone-beam CT guided PTNB with solid pulmonary lesions, and 76 patients who underwent fluoroscopy guided PTNB were matched to the patients who underwent cone-beam CT guided PTNB for age, sex, and lesion location. We evaluated predicting factors such as, long-axis diameter, short-axis diameter, anterior-posterior diameter, and CT attenuation value of the solid pulmonary lesion affecting conversion from fluoroscopy guided PTNB to cone-beam CT guided PTNB. Pearson χ 2 test, Fisher exact test, and independent t test were used in statistical analyses; in addition, we also used receiver operating characteristics curve to find the proper cut-off values affecting the conversion to cone-beam CT guided PTNB. Short-axis, long-axis, anterior-posterior diameter and CT attenuation value of the solid pulmonary lesion in patients who underwent fluoroscopy guided PTNB were 2.70 ± 1.57 cm, 3.40 ± 1.92 cm, 3.06 ± 1.81 cm, and 35.67 ± 15.70 Hounsfield unit (HU), respectively. Short-axis, long-axis, anterior-posterior diameter and CT attenuation value of the solid pulmonary lesion in patients who underwent cone-beam CT guided PTNB were 1.60 ± 1.30 cm, 2.20 ± 1.45 cm, 1.91 ± 1.99 cm, and 18.32 ± 23.11 HU, respectively. Short-axis, long-axis, anterior-posterior diameter, and CT attenuation value showed a significantly different mean value between the 2 groups (p = 0.001, p < 0.001, p = 0.003, p < 0.001, respectively). Odd ratios of CT attenuation value and short-axis diameter of the solid pulmonary lesion were 0.952 and 0.618, respectively. Proper cut-off values affecting the conversion to cone-beam CT guided PTNB were 1.65 cm (sensitivity 68.4%, specificity 71.1%) in short-axis diameter and 29.50 HU (sensitivity 65.8%, specificity 65.8%) in

  4. A study of reconstruction artifacts in cone beam tomography using filtered backprojection and iterative EM algorithms

    International Nuclear Information System (INIS)

    Zeng, G.L.; Gullberg, G.T.

    1990-01-01

    Reconstruction artifacts in cone beam tomography are studied for filtered backprojection (Feldkamp) and iterative EM algorithms. The filtered backprojection algorithm uses a voxel-driven, interpolated backprojection to reconstruct the cone beam data; whereas, the iterative EM algorithm performs ray-driven projection and backprojection operations for each iteration. Two weight in schemes for the projection and backprojection operations in the EM algorithm are studied. One weights each voxel by the length of the ray through the voxel and the other equates the value of a voxel to the functional value of the midpoint of the line intersecting the voxel, which is obtained by interpolating between eight neighboring voxels. Cone beam reconstruction artifacts such as rings, bright vertical extremities, and slice-to slice cross talk are not found with parallel beam and fan beam geometries

  5. Helical CT defecography

    International Nuclear Information System (INIS)

    Ferrando, R.; Fiorini, G.; Beghello, A.; Cicio, G.R.; Derchi, L.E.; Consigliere, M.; Resasco, M.; Tornago, S.

    1999-01-01

    The purpose of this work is to investigate the possible role of Helical CT defecography in pelvic floor disorders by comparing the results of the investigations with those of conventional defecography. The series analyzed consisted of 90 patients, namely 62 women and 28 men, ranging in age 24-82 years. They were all submitted to conventional defecography, and 18 questionable cases were also studied with Helical CT defecography. The conventional examination was performed during the 4 standard phases of resting, squeezing, Valsalva and straining; it is used a remote-control unit. The parameters for Helical CT defecography were: 5 mm beam collimation, pitch 2, 120 KV, 250 m As and 18-20 degrees gantry inclination to acquire coronal images of the pelvic floor. The rectal ampulla was distended with a bolus of 300 mL nonionic iodinated contrast agent (dilution: 3g/cc). The patient wore a napkin and was seated on the table, except for those who could not hold the position and were thus examined supine. Twenty-second helical scans were performed at rest and during evacuation; multiplanar reconstructions were obtained especially on the sagittal plane for comparison with conventional defecographic images. Coronal Helical CT defecography images permitted to map the perineal floor muscles, while sagittal reconstructions provided information on the ampulla and the levator ani. To conclude, Helical CT defecography performed well in study of pelvic floor disorders and can follow conventional defecography especially in questionable cases [it

  6. A new hybrid-FBP inversion algorithm with inverse distance backprojection weight for CT reconstruction

    Energy Technology Data Exchange (ETDEWEB)

    Narasimhadhan, A.V.; Rajgopal, Kasi

    2011-07-01

    This paper presents a new hybrid filtered backprojection (FBP) algorithm for fan-beam and cone-beam scan. The hybrid reconstruction kernel is the sum of the ramp and Hilbert filters. We modify the redundancy weighting function to reduce the inverse square distance weighting in the backprojection to inverse distance weight. The modified weight also eliminates the derivative associated with the Hilbert filter kernel. Thus, the proposed reconstruction algorithm has the advantages of the inverse distance weight in the backprojection. We evaluate the performance of the new algorithm in terms of the magnitude level and uniformity in noise for the fan-beam geometry. The computer simulations show that the spatial resolution is nearly identical to the standard fan-beam ramp filtered algorithm while the noise is spatially uniform and the noise variance is reduced. (orig.)

  7. Hardware system of parallel processing for fast CT image reconstruction based on circular shifting float memory architecture

    International Nuclear Information System (INIS)

    Wang Shi; Kang Kejun; Wang Jingjin

    1995-01-01

    Computerized Tomography (CT) is expected to become an inevitable diagnostic technique in the future. However, the long time required to reconstruct an image has been one of the major drawbacks associated with this technique. Parallel process is one of the best way to solve this problem. This paper gives the architecture and hardware design of PIRS-4 (4-processor Parallel Image Reconstruction System) which is a parallel processing system for fast 3D-CT image reconstruction by circular shifting float memory architecture. It includes structure and component of the system, the design of cross bar switch and details of control model. The test results are described

  8. Utilization of cone-beam CT for offline evaluation of target volume coverage during prostate image-guided radiotherapy based on bony anatomy alignment.

    Science.gov (United States)

    Paluska, Petr; Hanus, Josef; Sefrova, Jana; Rouskova, Lucie; Grepl, Jakub; Jansa, Jan; Kasaova, Linda; Hodek, Miroslav; Zouhar, Milan; Vosmik, Milan; Petera, Jiri

    2012-01-01

    To assess target volume coverage during prostate image-guided radiotherapy based on bony anatomy alignment and to assess possibility of safety margin reduction. Implementation of IGRT should influence safety margins. Utilization of cone-beam CT provides current 3D anatomic information directly in irradiation position. Such information enables reconstruction of the actual dose distribution. Seventeen prostate patients were treated with daily bony anatomy image-guidance. Cone-beam CT (CBCT) scans were acquired once a week immediately after bony anatomy alignment. After the prostate, seminal vesicles, rectum and bladder were contoured, the delivered dose distribution was reconstructed. Target dose coverage was evaluated by the proportion of the CTV encompassed by the 95% isodose. Original plans employed a 1 cm safety margin. Alternative plans assuming a smaller 7 mm margin between CTV and PTV were evaluated in the same way. Rectal and bladder volumes were compared with the initial ones. Rectal and bladder volumes irradiated with doses higher than 75 Gy, 70 Gy, 60 Gy, 50 Gy and 40 Gy were analyzed. In 12% of reconstructed plans the prostate coverage was not sufficient. The prostate underdosage was observed in 5 patients. Coverage of seminal vesicles was not satisfactory in 3% of plans. Most of the target underdosage corresponded to excessive rectal or bladder filling. Evaluation of alternative plans assuming a smaller 7 mm margin revealed 22% and 11% of plans where prostate and seminal vesicles coverage, respectively, was compromised. These were distributed over 8 and 7 patients, respectively. Sufficient dose coverage of target volumes was not achieved for all patients. Reducing of safety margin is not acceptable. Initial rectal and bladder volumes cannot be considered representative for subsequent treatment.

  9. SU-E-I-86: Ultra-Low Dose Computed Tomography Attenuation Correction for Pediatric PET CT Using Adaptive Statistical Iterative Reconstruction (ASiR™)

    Energy Technology Data Exchange (ETDEWEB)

    Brady, S; Shulkin, B [St. Jude Children’s Research Hospital, Memphis, TN (United States)

    2015-06-15

    Purpose: To develop ultra-low dose computed tomography (CT) attenuation correction (CTAC) acquisition protocols for pediatric positron emission tomography CT (PET CT). Methods: A GE Discovery 690 PET CT hybrid scanner was used to investigate the change to quantitative PET and CT measurements when operated at ultra-low doses (10–35 mAs). CT quantitation: noise, low-contrast resolution, and CT numbers for eleven tissue substitutes were analyzed in-phantom. CT quantitation was analyzed to a reduction of 90% CTDIvol (0.39/3.64; mGy) radiation dose from baseline. To minimize noise infiltration, 100% adaptive statistical iterative reconstruction (ASiR) was used for CT reconstruction. PET images were reconstructed with the lower-dose CTAC iterations and analyzed for: maximum body weight standardized uptake value (SUVbw) of various diameter targets (range 8–37 mm), background uniformity, and spatial resolution. Radiation organ dose, as derived from patient exam size specific dose estimate (SSDE), was converted to effective dose using the standard ICRP report 103 method. Effective dose and CTAC noise magnitude were compared for 140 patient examinations (76 post-ASiR implementation) to determine relative patient population dose reduction and noise control. Results: CT numbers were constant to within 10% from the non-dose reduced CTAC image down to 90% dose reduction. No change in SUVbw, background percent uniformity, or spatial resolution for PET images reconstructed with CTAC protocols reconstructed with ASiR and down to 90% dose reduction. Patient population effective dose analysis demonstrated relative CTAC dose reductions between 62%–86% (3.2/8.3−0.9/6.2; mSv). Noise magnitude in dose-reduced patient images increased but was not statistically different from pre dose-reduced patient images. Conclusion: Using ASiR allowed for aggressive reduction in CTAC dose with no change in PET reconstructed images while maintaining sufficient image quality for co

  10. WE-AB-207A-09: Optimization of the Design of a Moving Blocker for Cone-Beam CT Scatter Correction: Experimental Evaluation

    Energy Technology Data Exchange (ETDEWEB)

    Chen, X; Ouyang, L; Jia, X; Zhang, Y; Wang, J [UT Southwestern Medical Center, Dallas, TX (United States); Yan, H [Cyber Medical Corporation, Xi’an (China)

    2016-06-15

    Purpose: A moving blocker based strategy has shown promising results for scatter correction in cone-beam computed tomography (CBCT). Different geometry designs and moving speeds of the blocker affect its performance in image reconstruction accuracy. The goal of this work is to optimize the geometric design and moving speed of the moving blocker system through experimental evaluations. Methods: An Elekta Synergy XVI system and an anthropomorphic pelvis phantom CIRS 801-P were used for our experiment. A blocker consisting of lead strips was inserted between the x-ray source and the phantom moving back and forth along rotation axis to measure the scatter signal. Accoriding to our Monte Carlo simulation results, three blockers were used, which have the same lead strip width 3.2mm and different gap between neighboring lead strips, 3.2, 6.4 and 9.6mm. For each blocker, three moving speeds were evaluated, 10, 20 and 30 pixels per projection (on the detector plane). Scatter signal in the unblocked region was estimated by cubic B-spline based interpolation from the blocked region. CBCT image was reconstructed by a total variation (TV) based algebraic iterative reconstruction (ART) algorithm from the partially blocked projection data. Reconstruction accuracy in each condition is quantified as CT number error of region of interest (ROI) by comparing to a CBCT reconstructed image from analytically simulated unblocked and scatter free projection data. Results: Highest reconstruction accuracy is achieved when the blocker width is 3.2 mm, the gap between neighboring lead strips is 9.6 mm and the moving speed is 20 pixels per projection. RMSE of the CT number of ROIs can be reduced from 436 to 27. Conclusions: Image reconstruction accuracy is greatly affected by the geometry design of the blocker. The moving speed does not have a very strong effect on reconstruction result if it is over 20 pixels per projection.

  11. 2-D Low Energy Electron Beam Profile Measurement Based on Computer Tomography Algorithm with Multi-Wire Scanner

    CERN Document Server

    Yu, Nengjie; Li Qing Feng; Tang, Chuan-Xiang; Zheng, Shuxin

    2005-01-01

    A new method for low energy electron beam profile measurement is advanced, which presents a full 2-D beam profile distribution other than the traditional 2-D beam profile distribution given by 1-D vertical and horizontal beam profiles. The method is based on the CT (Computer Tomography) algorithm. Multi-sets of data about the 1-D beam profile projections are attained by rotating the multi-wire scanner. Then a 2-D beam profile is reconstructed from these projections with CT algorithm. The principle of this method is presented. The simulation and the experiment results are compared and analyzed in detail.

  12. Initial clinical evaluation of PET-based ion beam therapy monitoring under consideration of organ motion.

    Science.gov (United States)

    Kurz, Christopher; Bauer, Julia; Unholtz, Daniel; Richter, Daniel; Herfarth, Klaus; Debus, Jürgen; Parodi, Katia

    2016-02-01

    Intrafractional organ motion imposes considerable challenges to scanned ion beam therapy and demands for a thorough verification of the applied treatment. At the Heidelberg Ion-Beam Therapy Center (HIT), the scanned ion beam delivery is verified by means of postirradiation positron-emission-tomography (PET) imaging. This work presents a first clinical evaluation of PET-based treatment monitoring in ion beam therapy under consideration of target motion. Three patients with mobile liver lesions underwent scanned carbon ion irradiation at HIT and postirradiation PET/CT (x-ray-computed-tomography) imaging with a commercial scanner. Respiratory motion was recorded during irradiation and subsequent image acquisition. This enabled a time-resolved (4D) calculation of the expected irradiation-induced activity pattern and, for one patient where an additional 4D CT was acquired at the PET/CT scanner after treatment, a motion-compensated PET image reconstruction. For the other patients, PET data were reconstructed statically. To verify the treatment, calculated prediction and reconstructed measurement were compared with a focus on the ion beam range. Results in the current three patients suggest that for motion amplitudes in the order of 2 mm there is no benefit from incorporating respiratory motion information into PET-based treatment monitoring. For a target motion in the order of 10 mm, motion-related effects become more severe and a time-resolved modeling of the expected activity distribution can lead to an improved data interpretation if a sufficient number of true coincidences is detected. Benefits from motion-compensated PET image reconstruction could not be shown conclusively at the current stage. The feasibility of clinical PET-based treatment verification under consideration of organ motion has been shown for the first time. Improvements in noise-robust 4D PET image reconstruction are deemed necessary to enhance the clinical potential.

  13. Initial clinical evaluation of PET-based ion beam therapy monitoring under consideration of organ motion

    International Nuclear Information System (INIS)

    Kurz, Christopher; Bauer, Julia; Unholtz, Daniel; Herfarth, Klaus; Debus, Jürgen; Richter, Daniel; Parodi, Katia

    2016-01-01

    Purpose: Intrafractional organ motion imposes considerable challenges to scanned ion beam therapy and demands for a thorough verification of the applied treatment. At the Heidelberg Ion-Beam Therapy Center (HIT), the scanned ion beam delivery is verified by means of postirradiation positron-emission-tomography (PET) imaging. This work presents a first clinical evaluation of PET-based treatment monitoring in ion beam therapy under consideration of target motion. Methods: Three patients with mobile liver lesions underwent scanned carbon ion irradiation at HIT and postirradiation PET/CT (x-ray-computed-tomography) imaging with a commercial scanner. Respiratory motion was recorded during irradiation and subsequent image acquisition. This enabled a time-resolved (4D) calculation of the expected irradiation-induced activity pattern and, for one patient where an additional 4D CT was acquired at the PET/CT scanner after treatment, a motion-compensated PET image reconstruction. For the other patients, PET data were reconstructed statically. To verify the treatment, calculated prediction and reconstructed measurement were compared with a focus on the ion beam range. Results: Results in the current three patients suggest that for motion amplitudes in the order of 2 mm there is no benefit from incorporating respiratory motion information into PET-based treatment monitoring. For a target motion in the order of 10 mm, motion-related effects become more severe and a time-resolved modeling of the expected activity distribution can lead to an improved data interpretation if a sufficient number of true coincidences is detected. Benefits from motion-compensated PET image reconstruction could not be shown conclusively at the current stage. Conclusions: The feasibility of clinical PET-based treatment verification under consideration of organ motion has been shown for the first time. Improvements in noise-robust 4D PET image reconstruction are deemed necessary to enhance the

  14. Reconstruction of Cochlea Based on Micro-CT and Histological Images of the Human Inner Ear

    Directory of Open Access Journals (Sweden)

    Christos Bellos

    2014-01-01

    Full Text Available The study of the normal function and pathology of the inner ear has unique difficulties as it is inaccessible during life and, so, conventional techniques of pathologic studies such as biopsy and surgical excision are not feasible, without further impairing function. Mathematical modelling is therefore particularly attractive as a tool in researching the cochlea and its pathology. The first step towards efficient mathematical modelling is the reconstruction of an accurate three dimensional (3D model of the cochlea that will be presented in this paper. The high quality of the histological images is being exploited in order to extract several sections of the cochlea that are not visible on the micro-CT (mCT images (i.e., scala media, spiral ligament, and organ of Corti as well as other important sections (i.e., basilar membrane, Reissner membrane, scala vestibule, and scala tympani. The reconstructed model is being projected in the centerline of the coiled cochlea, extracted from mCT images, and represented in the 3D space. The reconstruction activities are part of the SIFEM project, which will result in the delivery of an infrastructure, semantically interlinking various tools and libraries (i.e., segmentation, reconstruction, and visualization tools with the clinical knowledge, which is represented by existing data, towards the delivery of a robust multiscale model of the inner ear.

  15. Cardiac CT for planning redo cardiac surgery: effect of knowledge-based iterative model reconstruction on image quality

    International Nuclear Information System (INIS)

    Oda, Seitaro; Weissman, Gaby; Weigold, W. Guy; Vembar, Mani

    2015-01-01

    The purpose of this study was to investigate the effects of knowledge-based iterative model reconstruction (IMR) on image quality in cardiac CT performed for the planning of redo cardiac surgery by comparing IMR images with images reconstructed with filtered back-projection (FBP) and hybrid iterative reconstruction (HIR). We studied 31 patients (23 men, 8 women; mean age 65.1 ± 16.5 years) referred for redo cardiac surgery who underwent cardiac CT. Paired image sets were created using three types of reconstruction: FBP, HIR, and IMR. Quantitative parameters including CT attenuation, image noise, and contrast-to-noise ratio (CNR) of each cardiovascular structure were calculated. The visual image quality - graininess, streak artefact, margin sharpness of each cardiovascular structure, and overall image quality - was scored on a five-point scale. The mean image noise of FBP, HIR, and IMR images was 58.3 ± 26.7, 36.0 ± 12.5, and 14.2 ± 5.5 HU, respectively; there were significant differences in all comparison combinations among the three methods. The CNR of IMR images was better than that of FBP and HIR images in all evaluated structures. The visual scores were significantly higher for IMR than for the other images in all evaluated parameters. IMR can provide significantly improved qualitative and quantitative image quality at in cardiac CT for planning of reoperative cardiac surgery. (orig.)

  16. A One-Step Cone-Beam CT-Enabled Planning-to-Treatment Model for Palliative Radiotherapy-From Development to Implementation

    International Nuclear Information System (INIS)

    Wong, Rebecca K.S.; Letourneau, Daniel; Varma, Anita; Bissonnette, Jean Pierre; Fitzpatrick, David; Grabarz, Daniel; Elder, Christine; Martin, Melanie; Bezjak, Andrea; Panzarella, Tony; Gospodarowicz, Mary; Jaffray, David A.

    2012-01-01

    Purpose: To develop a cone-beam computed tomography (CT)–enabled one-step simulation-to-treatment process for the treatment of bone metastases. Methods and Materials: A three-phase prospective study was conducted. Patients requiring palliative radiotherapy to the spine, mediastinum, or abdomen/pelvis suitable for treatment with simple beam geometry (≤2 beams) were accrued. Phase A established the accuracy of cone-beam CT images for the purpose of gross tumor target volume (GTV) definition. Phase B evaluated the feasibility of implementing the cone-beam CT–enabled planning process at the treatment unit. Phase C evaluated the online cone-beam CT–enabled process for the planning and treatment of patients requiring radiotherapy for bone metastases. Results: Eighty-four patients participated in this study. Phase A (n = 9) established the adequacy of cone-beam CT images for target definition. Phase B (n = 45) established the quality of treatment plans to be adequate for clinical implementation for bone metastases. When the process was applied clinically in bone metastases (Phase C), the degree of overlap between planning computed tomography (PCT) and cone-beam CT for GTV and between PCT and cone-beam CT for treatment field was 82% ± 11% and 97% ± 4%, respectively. The oncologist’s decision to accept the plan under a time-pressured environment remained of high quality, with the cone-beam CT–generated treatment plan delivering at least 90% of the prescribed dose to 100% ± 0% of the cone-beam CT planning target volume (PTV). With the assumption that the PCT PTV is the gold-standard target, the cone-beam CT–generated treatment plan delivered at least 90% and at least 95% of dose to 98% ± 2% and 97% ± 5% of the PCT PTV, respectively. The mean time for the online planning and treatment process was 32.7 ± 4.0 minutes. Patient satisfaction was high, with a trend for superior satisfaction with the cone-beam CT–enabled process. Conclusions: The cone-beam CT

  17. Interior tomography in microscopic CT with image reconstruction constrained by full field of view scan at low spatial resolution

    Science.gov (United States)

    Luo, Shouhua; Shen, Tao; Sun, Yi; Li, Jing; Li, Guang; Tang, Xiangyang

    2018-04-01

    In high resolution (microscopic) CT applications, the scan field of view should cover the entire specimen or sample to allow complete data acquisition and image reconstruction. However, truncation may occur in projection data and results in artifacts in reconstructed images. In this study, we propose a low resolution image constrained reconstruction algorithm (LRICR) for interior tomography in microscopic CT at high resolution. In general, the multi-resolution acquisition based methods can be employed to solve the data truncation problem if the project data acquired at low resolution are utilized to fill up the truncated projection data acquired at high resolution. However, most existing methods place quite strict restrictions on the data acquisition geometry, which greatly limits their utility in practice. In the proposed LRICR algorithm, full and partial data acquisition (scan) at low and high resolutions, respectively, are carried out. Using the image reconstructed from sparse projection data acquired at low resolution as the prior, a microscopic image at high resolution is reconstructed from the truncated projection data acquired at high resolution. Two synthesized digital phantoms, a raw bamboo culm and a specimen of mouse femur, were utilized to evaluate and verify performance of the proposed LRICR algorithm. Compared with the conventional TV minimization based algorithm and the multi-resolution scout-reconstruction algorithm, the proposed LRICR algorithm shows significant improvement in reduction of the artifacts caused by data truncation, providing a practical solution for high quality and reliable interior tomography in microscopic CT applications. The proposed LRICR algorithm outperforms the multi-resolution scout-reconstruction method and the TV minimization based reconstruction for interior tomography in microscopic CT.

  18. Super resolution reconstruction of μ-CT image of rock sample using neighbour embedding algorithm

    Science.gov (United States)

    Wang, Yuzhu; Rahman, Sheik S.; Arns, Christoph H.

    2018-03-01

    X-ray computed tomography (μ-CT) is considered to be the most effective way to obtain the inner structure of rock sample without destructions. However, its limited resolution hampers its ability to probe sub-micro structures which is critical for flow transportation of rock sample. In this study, we propose an innovative methodology to improve the resolution of μ-CT image using neighbour embedding algorithm where low frequency information is provided by μ-CT image itself while high frequency information is supplemented by high resolution scanning electron microscopy (SEM) image. In order to obtain prior for reconstruction, a large number of image patch pairs contain high- and low- image patches are extracted from the Gaussian image pyramid generated by SEM image. These image patch pairs contain abundant information about tomographic evolution of local porous structures under different resolution spaces. Relying on the assumption of self-similarity of porous structure, this prior information can be used to supervise the reconstruction of high resolution μ-CT image effectively. The experimental results show that the proposed method is able to achieve the state-of-the-art performance.

  19. Comparative diagnostic yield of cone beam CT reconstruction using various software programs on the detection of vertical root fractures.

    Science.gov (United States)

    Melo, S L S; Haiter-Neto, F; Correa, L R; Scarfe, W C; Farman, A G

    2013-01-01

    To evaluate the effect on diagnostic yield in the detection of experimentally induced vertical root fractures on cone beam CT images using four dental software program. 190 single-rooted extracted human teeth were divided into three groups according to the pulp canal status: unrestored (UR), filled with gutta-percha (GP) and restored with a metallic custom post (Post). One-half of the sample of each group was artificially fractured and the segments repositioned. All teeth were scanned on a cone beam CT device at 0.2 mm nominal voxel resolution (i-CAT Platinum; Imaging Sciences International, Hatfield, PA). The data were exported as digital imaging and communications in medicine files and imported into Dolphin Imaging & Management Solutions, v. 11.5 (Patterson Dental Supply Inc., St Paul, MN), InVivoDental, v. 5.0 (Anatomage Inc., San Jose, CA) and Kodak Dental Imaging Software 3D module, v. 2.1.11 (Carestream Health Inc., Rochester, NY) software. Cross-sectional images in the acquisition (using Xoran CAT™, v. 3.0.34 software; Xoran Technologies, Ann Arbor, MI) and additional software were presented to three calibrated oral radiologists who rated the presence or absence of root fracture on a five-point scale. Receiver operating characteristic analysis was performed, and treatment comparisons compared by analysis of variance and pairwise comparisons were performed using Tukey's test at an a priori value of α < 0.05%. All dental software performed equally at detecting fractures. Fractures were significantly more difficult to detect when posts were present. The diagnosis of root fracture is software-independent. The presence of an intracanal metallic post significantly decreases the detection of artificially created root fractures.

  20. Assessment of prostate motion during radiotherapy using fiducial markers and CT reconstruction

    International Nuclear Information System (INIS)

    Crook, J.; Salhani, D.; Yang, H.; Deshaies, Y.; Raymond, Y.; Malone, S.; Esche, B.

    1996-01-01

    Purpose: To assess changes in prostate position during a course of pelvic radiotherapy for prostate cancer using fiducial markers and sequential planning CT scans. Methods and Materials: Three gold seeds are implanted in the apex, base and posterior aspect of the prostate under trans-rectal ultrasound guidance prior to initial simulation. In addition, treatment planning CT scans with 5 mm slices through the prostate are obtained at 0 and 40 Gy. Patients are scanned, simulated and treated with full bladder and are positioned using a standard foam leg support from the knees to the ankles. Prostate movement is assessed by two independent methods: [1] Localization of the fiducial markers using orthogonal simulator films taken just prior to the initial and boost stages of treatment and [2] a three-dimensional reconstruction methodology using CT datasets again obtained prior to the initial and boost stages. In both cases, rigid-body transformations of selected bony landmarks were used to eliminate patient movement between simulations and CT scans. For CT reconstruction, high order polynomial extrapolation and Chebychev multi-domain interpolation methods are employed to determine the coordinates of the fiducial markers. Prostatic movement, between initial and boost imaging, is estimated from the variance of the position of the corresponding seeds. Results: At present, seed data is available for sixty (60) patients. An additional nineteen (19) patients were excluded because of suspected seed migration > 3.0 mm or a localization uncertainty > 1.5 mm. The range of movement seen in the lateral direction is -0.25 to 0.48 cm (mean: 0.11, SD: 0.15), in the cranio-caudal direction -1.57 to 0.64 cm (mean: 0.59 SD: 0.48), and in the antero-posterior direction -1.91 to .47 cm (mean: 0.53, SD: 0.39). Results disclosed 53% of the patients with a caudal shift of the prostate > 0.5 cm and 10% > 1.0 cm. Further, 60% of the patients showed a posterior shift > 0.5 cm and 27% > 1.0 cm. CT

  1. Intra-patient comparison of reduced-dose model-based iterative reconstruction with standard-dose adaptive statistical iterative reconstruction in the CT diagnosis and follow-up of urolithiasis

    Energy Technology Data Exchange (ETDEWEB)

    Tenant, Sean; Pang, Chun Lap; Dissanayake, Prageeth [Peninsula Radiology Academy, Plymouth (United Kingdom); Vardhanabhuti, Varut [Plymouth University Peninsula Schools of Medicine and Dentistry, Plymouth (United Kingdom); University of Hong Kong, Department of Diagnostic Radiology, Li Ka Shing Faculty of Medicine, Pokfulam (China); Stuckey, Colin; Gutteridge, Catherine [Plymouth Hospitals NHS Trust, Plymouth (United Kingdom); Hyde, Christopher [University of Exeter Medical School, St Luke' s Campus, Exeter (United Kingdom); Roobottom, Carl [Plymouth University Peninsula Schools of Medicine and Dentistry, Plymouth (United Kingdom); Plymouth Hospitals NHS Trust, Plymouth (United Kingdom)

    2017-10-15

    To evaluate the accuracy of reduced-dose CT scans reconstructed using a new generation of model-based iterative reconstruction (MBIR) in the imaging of urinary tract stone disease, compared with a standard-dose CT using 30% adaptive statistical iterative reconstruction. This single-institution prospective study recruited 125 patients presenting either with acute renal colic or for follow-up of known urinary tract stones. They underwent two immediately consecutive scans, one at standard dose settings and one at the lowest dose (highest noise index) the scanner would allow. The reduced-dose scans were reconstructed using both ASIR 30% and MBIR algorithms and reviewed independently by two radiologists. Objective and subjective image quality measures as well as diagnostic data were obtained. The reduced-dose MBIR scan was 100% concordant with the reference standard for the assessment of ureteric stones. It was extremely accurate at identifying calculi of 3 mm and above. The algorithm allowed a dose reduction of 58% without any loss of scan quality. A reduced-dose CT scan using MBIR is accurate in acute imaging for renal colic symptoms and for urolithiasis follow-up and allows a significant reduction in dose. (orig.)

  2. CT reconstruction from few-views with anisotropic edge-guided total variance

    International Nuclear Information System (INIS)

    Rong, Junyan; Liu, Wenlei; Gao, Peng; Liao, Qimei; Jiao, Chun; Ma, Jianhua; Lu, Hongbing

    2016-01-01

    To overcome the oversmoothing drawback in the edge areas when reconstructing few-view CT with total variation (TV) minimization, in this paper, we propose an anisotropic edge-guided TV minimization framework for few-view CT reconstruction. In the framework, anisotropic TV is summed with pre-weighted image gradient and then used as the object function for minimizing. It includes edge-guided TV minimization (EGTV) and edge-guided adaptive-weighted TV minimization (EGAwTV) algorithms. For EGTV algorithm, the weights of the TV discretization term are updated by anisotropic edge information detected from the image, whereas the weights for EGAwTV are determined based on edge information and local image-intensity gradients. To solve the minimization problem of the proposed algorithm, a similar TV-based minimization implementation is developed to address the raw data fidelity and other constraints. The evaluation results using both computer simulations with the Shepp-Logan phantom and experimental data from a physical phantom demonstrate that the proposed algorithms exhibit noticeable gains in the merits of spatial resolution compared with the conventional TV and other modified TV algorithms.

  3. Megavoltage cone-beam computed tomography using a high-efficiency image receptor

    International Nuclear Information System (INIS)

    Seppi, Ed J.; Munro, Peter; Johnsen, Stan W.; Shapiro, Ed G.; Tognina, Carlo; Jones, Dan; Pavkovich, John M.; Webb, Chris; Mollov, Ivan; Partain, Larry D.; Colbeth, Rick E.

    2003-01-01

    Purpose: To develop an image receptor capable of forming high-quality megavoltage CT images using modest radiation doses. Methods and Materials: A flat-panel imaging system consisting of a conventional flat-panel sensor attached to a thick CsI scintillator has been fabricated. The scintillator consists of individual CsI crystals 8 mm thick by 0.38 mm x 0.38-mm pitch. Five sides of each crystal are coated with a reflecting powder/epoxy mixture, and the sixth side is in contact with the flat-panel sensor. A timing interface coordinates acquisition by the imaging system and pulsing of the linear accelerator. With this interface, as little as one accelerator pulse (0.023 cGy at the isocenter) can be used to form projection images. Different CT phantoms irradiated by a 6-MV X-ray beam have been imaged to evaluate the performance of the imaging system. The phantoms have been mounted on a rotating stage and rotated while 360 projection images are acquired in 48 s. These projections have been reconstructed using the Feldkamp cone-beam CT reconstruction algorithm. Results and Discussion: Using an irradiation of 16 cGy (360 projections x 0.046 cGy/projection), the contrast resolution is ∼1% for large objects. High-contrast structures as small as 1.2 mm are clearly visible. The reconstructed CT values are linear (R 2 =0.98) for electron densities between 0.001 and 2.16 g/cm 3 , and the reconstruction time for a 512 x 512 x 512 data set is 6 min. Images of an anthropomorphic phantom show that soft-tissue structures such as the heart, lung, kidneys, and liver are visible in the reconstructed images (16 cGy, 5-mm-thick slices). Conclusions: The acquisition of megavoltage CT images with soft-tissue contrast is possible with irradiations as small as 16 cGy

  4. Computer-assisted lung nodule volumetry from multi-detector row CT: Influence of image reconstruction parameters

    International Nuclear Information System (INIS)

    Honda, Osamu; Sumikawa, Hiromitsu; Johkoh, Takeshi; Tomiyama, Noriyuki; Mihara, Naoki; Inoue, Atsuo; Tsubamoto, Mitsuko; Natsag, Javzandulam; Hamada, Seiki; Nakamura, Hironobu

    2007-01-01

    Purpose: To investigate differences in volumetric measurement of pulmonary nodules caused by changing the reconstruction parameters for multi-detector row CT. Materials and methods: Thirty-nine pulmonary nodules less than 2 cm in diameter were examined by multi-slice CT. All nodules were solid, and located in the peripheral part of the lungs. The resultant 48 parameters images were reconstructed by changing slice thickness (1.25, 2.5, 3.75, or 5 mm), field of view (FOV: 10, 20, or 30 cm), algorithm (high-spatial frequency algorithm or low-spatial frequency algorithm) and reconstruction interval (reconstruction with 50% overlapping of the reconstructed slices or non-overlapping reconstruction). Volumetric measurements were calculated using commercially available software. The differences between nodule volumes were analyzed by the Kruskal-Wallis test and the Wilcoxon Signed-Ranks test. Results: The diameter of the nodules was 8.7 ± 2.7 mm on average, ranging from 4.3 to 16.4 mm. Pulmonary nodule volume did not change significantly with changes in slice thickness or FOV (p > 0.05), but was significantly larger with the high-spatial frequency algorithm than the low-spatial frequency algorithm (p < 0.05), except for one reconstruction parameter. The volumes determined by non-overlapping reconstruction were significantly larger than those of overlapping reconstruction (p < 0.05), except for a 1.25 mm thickness with 10 cm FOV with the high-spatial frequency algorithm, and 5 mm thickness. The maximum difference in measured volume was 16% on average between the 1.25 mm slice thickness/10 cm FOV/high-spatial frequency algorithm parameters and overlapping reconstruction. Conclusion: Volumetric measurements of pulmonary nodules differ with changes in the reconstruction parameters, with a tendency toward larger volumes in high-spatial frequency algorithm and non-overlapping reconstruction compared to the low-spatial frequency algorithm and overlapping reconstruction

  5. Influence of iterative reconstruction on coronary calcium scores at multiple heart rates: a multivendor phantom study on state-of-the-art CT systems.

    Science.gov (United States)

    van der Werf, N R; Willemink, M J; Willems, T P; Greuter, M J W; Leiner, T

    2017-12-28

    The objective of this study was to evaluate the influence of iterative reconstruction on coronary calcium scores (CCS) at different heart rates for four state-of-the-art CT systems. Within an anthropomorphic chest phantom, artificial coronary arteries were translated in a water-filled compartment. The arteries contained three different calcifications with low (38 mg), medium (80 mg) and high (157 mg) mass. Linear velocities were applied, corresponding to heart rates of 0,  75 bpm. Data were acquired on four state-of-the-art CT systems (CT1-CT4) with routinely used CCS protocols. Filtered back projection (FBP) and three increasing levels of iterative reconstruction (L1-L3) were used for reconstruction. CCS were quantified as Agatston score and mass score. An iterative reconstruction susceptibility (IRS) index was used to assess susceptibility of Agatston score (IRS AS ) and mass score (IRS MS ) to iterative reconstruction. IRS values were compared between CT systems and between calcification masses. For each heart rate, differences in CCS of iterative reconstructed images were evaluated with CCS of FBP images as reference, and indicated as small ( 10%). Statistical analysis was performed with repeated measures ANOVA tests. While subtle differences were found for Agatston scores of low mass calcification, medium and high mass calcifications showed increased CCS up to 77% with increasing heart rates. IRS AS of CT1-T4 were 17, 41, 130 and 22% higher than IRS MS . Not only were IRS significantly different between all CT systems, but also between calcification masses. Up to a fourfold increase in IRS was found for the low mass calcification in comparison with the high mass calcification. With increasing iterative reconstruction strength, maximum decreases of 21 and 13% for Agatston and mass score were found. In total, 21 large differences between Agatston scores from FBP and iterative reconstruction were found, while only five large differences were found between

  6. MO-FG-204-04: How Iterative Reconstruction Algorithms Affect the NPS of CT Images

    International Nuclear Information System (INIS)

    Li, G; Liu, X; Dodge, C; Jensen, C; Rong, J

    2015-01-01

    Purpose: To evaluate how the third generation model based iterative reconstruction (MBIR) compares with filtered back-projection (FBP), adaptive statistical iterative reconstruction (ASiR), and the second generation MBIR based on noise power spectrum (NPS) analysis over a wide range of clinically applicable dose levels. Methods: The Catphan 600 CTP515 module, surrounded by an oval, fat-equivalent ring to mimic patient size/shape, was scanned on a GE HD750 CT scanner at 1, 2, 3, 6, 12 and 19mGy CTDIvol levels with typical patient scan parameters: 120kVp, 0.8s, 40mm beam width, large SFOV, 0.984 pitch and reconstructed thickness 2.5mm (VEO3.0: Abd/Pelvis with Texture and NR05). At each CTDIvol level, 10 repeated scans were acquired for achieving sufficient data sampling. The images were reconstructed using Standard kernel with FBP; 20%, 40% and 70% ASiR; and two versions of MBIR (VEO2.0 and 3.0). For evaluating the effect of the ROI spatial location to the Result of NPS, 4 ROI groups were categorized based on their distances from the center of the phantom. Results: VEO3.0 performed inferiorly comparing to VEO2.0 over all dose levels. On the other hand, at low dose levels (less than 3 mGy), it clearly outperformed ASiR and FBP, in NPS values. Therefore, the lower the dose level, the relative performance of MBIR improves. However, the shapes of the NPS show substantial differences in horizontal and vertical sampling dimensions. These differences may determine the characteristics of the noise/texture features in images, and hence, play an important role in image interpretation. Conclusion: The third generation MBIR did not improve over the second generation MBIR in term of NPS analysis. The overall performance of both versions of MBIR improved as compared to other reconstruction algorithms when dose was reduced. The shapes of the NPS curves provided additional value for future characterization of the image noise/texture features

  7. MO-FG-204-04: How Iterative Reconstruction Algorithms Affect the NPS of CT Images

    Energy Technology Data Exchange (ETDEWEB)

    Li, G; Liu, X; Dodge, C; Jensen, C; Rong, J [UT MD Anderson Cancer Center, Houston, TX (United States)

    2015-06-15

    Purpose: To evaluate how the third generation model based iterative reconstruction (MBIR) compares with filtered back-projection (FBP), adaptive statistical iterative reconstruction (ASiR), and the second generation MBIR based on noise power spectrum (NPS) analysis over a wide range of clinically applicable dose levels. Methods: The Catphan 600 CTP515 module, surrounded by an oval, fat-equivalent ring to mimic patient size/shape, was scanned on a GE HD750 CT scanner at 1, 2, 3, 6, 12 and 19mGy CTDIvol levels with typical patient scan parameters: 120kVp, 0.8s, 40mm beam width, large SFOV, 0.984 pitch and reconstructed thickness 2.5mm (VEO3.0: Abd/Pelvis with Texture and NR05). At each CTDIvol level, 10 repeated scans were acquired for achieving sufficient data sampling. The images were reconstructed using Standard kernel with FBP; 20%, 40% and 70% ASiR; and two versions of MBIR (VEO2.0 and 3.0). For evaluating the effect of the ROI spatial location to the Result of NPS, 4 ROI groups were categorized based on their distances from the center of the phantom. Results: VEO3.0 performed inferiorly comparing to VEO2.0 over all dose levels. On the other hand, at low dose levels (less than 3 mGy), it clearly outperformed ASiR and FBP, in NPS values. Therefore, the lower the dose level, the relative performance of MBIR improves. However, the shapes of the NPS show substantial differences in horizontal and vertical sampling dimensions. These differences may determine the characteristics of the noise/texture features in images, and hence, play an important role in image interpretation. Conclusion: The third generation MBIR did not improve over the second generation MBIR in term of NPS analysis. The overall performance of both versions of MBIR improved as compared to other reconstruction algorithms when dose was reduced. The shapes of the NPS curves provided additional value for future characterization of the image noise/texture features.

  8. Estimation of diastolic filling pressure with cardiac CT in comparison with echocardiography using tissue doppler imaging: Determination of optimal CT reconstruction parameters

    Energy Technology Data Exchange (ETDEWEB)

    Hwang, Ji Sun; Suh, Jon; Lee, Heon [Soonchunhyang University Hospital Bucheon, Bucheon (Korea, Republic of); Lee, Bora [Dept. of Biostatistics, Soonchunhyang University College of Medicine, Seoul (Korea, Republic of); Lee, Soo Jeong [Terarecon Korea, Seoul (Korea, Republic of); Jou, Sung Shick [Dept. of Radiology, Soonchunhyang University Hospital Cheonan, Cheonan (Korea, Republic of); Lim, Hyun Kyung [Dept. of Radiology, Soonchunhyang University Hospital Seoul, Seoul (Korea, Republic of)

    2017-08-01

    To determine the optimal CT image reconstruction parameters for the measurement of early transmitral peak velocity (E), early peak mitral septal tissue velocity (E′), and E / E′. Forty-six patients underwent simultaneous cardiac CT and echocardiography on the same day. Four CT datasets were reconstructed with a slice thickness/interval of 0.9/0.9 mm or 3/3 mm at 10 (10% RR-interval) or 20 (5% RR-interval) RR-intervals. The E was calculated by dividing the peak transmitral flow (mL/s) by the corresponding mitral valve area (cm{sup 2}). E′ was calculated from the changes in the left ventricular length per cardiac phase. E / E′ was then estimated and compared with that from echocardiography. For assessment of E / E′, CT and echocardiography were more strongly correlated (p < 0.05) with a slice thickness of 0.9 mm and 5% RR-interval (r = 0.77) than with 3 mm or 10% RR-interval. The diagnostic accuracy of predicting elevated filling pressure (E / E′ ≥ 13, n = 14) was better with a slice thickness of 0.9 mm and 5% RR-interval (87.0%) than with 0.9 mm and 10% RR-interval (71.7%) (p = 0.123) and significantly higher than that with a slice thickness of 3 mm with 5% (67.4%) and 10% RR-interval (63.0%), (p < 0.05), respectively. Data reconstruction with a slice thickness of 0.9 mm at 5% RR-interval is superior to that with a slice thickness of 3 mm or 10% RR-interval in terms of the correlation of E / E′ between CT and echocardiography. Thin slices and frequent sampling also allow for more accurate prediction of elevated filling pressure.

  9. Development of the three dimensional image display program for limited cone beam X-ray CT for dental use (Ortho-CT)

    International Nuclear Information System (INIS)

    Arai, Yoshinori; Hashimoto, Koji; Shinoda, Koji

    2000-01-01

    We have already developed and reported a limited cone beam X-ray CT system for dental use (Ortho-CT). This system has been used clinically since 1997. In this study, we report a 3D surface display program for Ortho-CT which has been newly-developed by the authors. The 3D surface display software has been developed using visual C ++ (Microsoft Co. WA. USA) and a personal computer (Pentium 450MHz Intel Co. CA USA, Windows NT 4.0 Microsoft WA. USA). In this software, the 3D surface images are recorded as AVI files and can be displayed on the personal computer. The 3D images can be rotated and a stepwise change of the threshold voxel value for binary image formation can be automatically used. We have applied these 3D surface images to clinical studies from January 1999 to May 1999 at the Radiology section in our Dental hospital. The images can be displayed very easily in personal computers using AVI files. Thirty-five cases have been reconstructed using 3D surface images in this way. The 3D surface image is useful in the diagnosis of fractures of the mandibular head and impacted teeth. Only teeth are observed when a relative threshold voxel value is set at a high level such as about 0.37. When the threshold is changed to a lower value (about 0.3), we can observe both teeth and the surface of the bone. We have developed a 3D surface display program for personal computers. The images are useful for the diagnosis of the pathosis in the maxillofacial region. (author)

  10. Reduction of metal artifacts from hip prostheses on CT images of the pelvis: value of iterative reconstructions.

    Science.gov (United States)

    Morsbach, Fabian; Bickelhaupt, Sebastian; Wanner, Guido A; Krauss, Andreas; Schmidt, Bernhard; Alkadhi, Hatem

    2013-07-01

    To assess the value of iterative frequency split-normalized (IFS) metal artifact reduction (MAR) for computed tomography (CT) of hip prostheses. This study had institutional review board and local ethics committee approval. First, a hip phantom with steel and titanium prostheses that had inlays of water, fat, and contrast media in the pelvis was used to optimize the IFS algorithm. Second, 41 consecutive patients with hip prostheses who were undergoing CT were included. Data sets were reconstructed with filtered back projection, the IFS algorithm, and a linear interpolation MAR algorithm. Two blinded, independent readers evaluated axial, coronal, and sagittal CT reformations for overall image quality, image quality of pelvic organs, and assessment of pelvic abnormalities. CT attenuation and image noise were measured. Statistical analysis included the Friedman test, Wilcoxon signed-rank test, and Levene test. Ex vivo experiments demonstrated an optimized IFS algorithm by using a threshold of 2200 HU with four iterations for both steel and titanium prostheses. Measurements of CT attenuation of the inlays were significantly (P algorithm for CT image reconstruction significantly reduces metal artifacts from hip prostheses, improves the reliability of CT number measurements, and improves the confidence for depicting pelvic abnormalities.

  11. THz computed tomography system with zero-order Bessel beam

    Science.gov (United States)

    Niu, Liting; Wu, Qiao; Wang, Kejia; Liu, Jinsong; Yang, Zhengang

    2018-01-01

    Terahertz (THz) waves can penetrate many optically opaque dielectric materials such as plastics, ceramics and colorants. It is effective to reveal the internal structures of these materials. We have built a THz Computed Tomography (CT) system with 0.3 THz zero-order Bessel beam to improve the depth of focus of this imaging system for the non-diffraction property of Bessel beam. The THz CT system has been used to detect a paper cup with a metal rod inside. Finally, the acquired projection data have been processed by the filtered back-projection algorithm and the reconstructed image of the sample has been obtained.

  12. Fast shading correction for cone beam CT in radiation therapy via sparse sampling on planning CT.

    Science.gov (United States)

    Shi, Linxi; Tsui, Tiffany; Wei, Jikun; Zhu, Lei

    2017-05-01

    The image quality of cone beam computed tomography (CBCT) is limited by severe shading artifacts, hindering its quantitative applications in radiation therapy. In this work, we propose an image-domain shading correction method using planning CT (pCT) as prior information which is highly adaptive to clinical environment. We propose to perform shading correction via sparse sampling on pCT. The method starts with a coarse mapping between the first-pass CBCT images obtained from the Varian TrueBeam system and the pCT. The scatter correction method embedded in the Varian commercial software removes some image errors but the CBCT images still contain severe shading artifacts. The difference images between the mapped pCT and the CBCT are considered as shading errors, but only sparse shading samples are selected for correction using empirical constraints to avoid carrying over false information from pCT. A Fourier-Transform-based technique, referred to as local filtration, is proposed to efficiently process the sparse data for effective shading correction. The performance of the proposed method is evaluated on one anthropomorphic pelvis phantom and 17 patients, who were scheduled for radiation therapy. (The codes of the proposed method and sample data can be downloaded from https://sites.google.com/view/linxicbct) RESULTS: The proposed shading correction substantially improves the CBCT image quality on both the phantom and the patients to a level close to that of the pCT images. On the phantom, the spatial nonuniformity (SNU) difference between CBCT and pCT is reduced from 74 to 1 HU. The root of mean square difference of SNU between CBCT and pCT is reduced from 83 to 10 HU on the pelvis patients, and from 101 to 12 HU on the thorax patients. The robustness of the proposed shading correction is fully investigated with simulated registration errors between CBCT and pCT on the phantom and mis-registration on patients. The sparse sampling scheme of our method successfully

  13. A simple, direct method for x-ray scatter estimation and correction in digital radiography and cone-beam CT

    International Nuclear Information System (INIS)

    Siewerdsen, J.H.; Daly, M.J.; Bakhtiar, B.

    2006-01-01

    X-ray scatter poses a significant limitation to image quality in cone-beam CT (CBCT), resulting in contrast reduction, image artifacts, and lack of CT number accuracy. We report the performance of a simple scatter correction method in which scatter fluence is estimated directly in each projection from pixel values near the edge of the detector behind the collimator leaves. The algorithm operates on the simple assumption that signal in the collimator shadow is attributable to x-ray scatter, and the 2D scatter fluence is estimated by interpolating between pixel values measured along the top and bottom edges of the detector behind the collimator leaves. The resulting scatter fluence estimate is subtracted from each projection to yield an estimate of the primary-only images for CBCT reconstruction. Performance was investigated in phantom experiments on an experimental CBCT benchtop, and the effect on image quality was demonstrated in patient images (head, abdomen, and pelvis sites) obtained on a preclinical system for CBCT-guided radiation therapy. The algorithm provides significant reduction in scatter artifacts without compromise in contrast-to-noise ratio (CNR). For example, in a head phantom, cupping artifact was essentially eliminated, CT number accuracy was restored to within 3%, and CNR (breast-to-water) was improved by up to 50%. Similarly in a body phantom, cupping artifact was reduced by at least a factor of 2 without loss in CNR. Patient images demonstrate significantly increased uniformity, accuracy, and contrast, with an overall improvement in image quality in all sites investigated. Qualitative evaluation illustrates that soft-tissue structures that are otherwise undetectable are clearly delineated in scatter-corrected reconstructions. Since scatter is estimated directly in each projection, the algorithm is robust with respect to system geometry, patient size and heterogeneity, patient motion, etc. Operating without prior information, analytical modeling

  14. Could new reconstruction CT techniques challenge MRI for the detection of brain metastases in the context of initial lung cancer staging?

    Energy Technology Data Exchange (ETDEWEB)

    Millon, Domitille; Byl, David; Coche, Emmanuel E. [Universite Catholique de Louvain, Department of Radiology and Medical Imaging, Cliniques Universitaires Saint Luc, Brussels (Belgium); Collard, Philippe [Universite Catholique de Louvain, Department of Pneumology, Cliniques Universitaires Saint Luc, Brussels (Belgium); Cambier, Samantha E.; Maanen, Aline G. van [Universite Catholique de Louvain, Statistic Unit, King Albert II Cancer Institute, Brussels (Belgium); Vlassenbroek, Alain [Philips Healthcare, Brussels (Belgium)

    2018-02-15

    To evaluate the diagnostic performance of brain CT images reconstructed with a model-based iterative algorithm performed at usual and reduced dose. 115 patients with histologically proven lung cancer were prospectively included over 15 months. Patients underwent two CT acquisitions at the initial staging, performed on a 256-slice MDCT, at standard (CTDIvol: 41.4 mGy) and half dose (CTDIvol: 20.7 mGy). Both image datasets were reconstructed with filtered back projection (FBP) and iterative model-based reconstruction (IMR) algorithms. Brain MRI was considered as the reference. Two blinded independent readers analysed the images. Ninety-three patients underwent all examinations. At the standard dose, eight patients presented 17 and 15 lesions on IMR and FBP CT images, respectively. At half-dose, seven patients presented 15 and 13 lesions on IMR and FBP CT images, respectively. The test could not highlight any significant difference between the standard dose IMR and the half-dose FBP techniques (p-value = 0.12). MRI showed 46 metastases on 11 patients. Specificity, negative and positive predictive values were calculated (98.9-100 %, 93.6-94.6 %, 75-100 %, respectively, for all CT techniques). No significant difference could be demonstrated between the two CT reconstruction techniques. (orig.)

  15. The parallel processing system for fast 3D-CT image reconstruction by circular shifting float memory architecture

    International Nuclear Information System (INIS)

    Wang Shi; Kang Kejun; Wang Jingjin

    1996-01-01

    Computerized Tomography (CT) is expected to become an inevitable diagnostic technique in the future. However, the long time required to reconstruct an image has been one of the major drawbacks associated with this technique. Parallel process is one of the best way to solve this problem. This paper gives the architecture, hardware and software design of PIRS-4 (4-processor Parallel Image Reconstruction System), which is a parallel processing system for fast 3D-CT image reconstruction by circular shifting float memory architecture. It includes the structure and components of the system, the design of crossbar switch and details of control model, the description of RPBP image reconstruction, the choice of OS (Operate System) and language, the principle of imitating EMS, direct memory R/W of float and programming in the protect model. Finally, the test results are given

  16. Impact of the adaptive statistical iterative reconstruction technique on image quality in ultra-low-dose CT

    International Nuclear Information System (INIS)

    Xu, Yan; He, Wen; Chen, Hui; Hu, Zhihai; Li, Juan; Zhang, Tingting

    2013-01-01

    Aim: To evaluate the relationship between different noise indices (NIs) and radiation dose and to compare the effect of different reconstruction algorithm applications for ultra-low-dose chest computed tomography (CT) on image quality improvement and the accuracy of volumetric measurement of ground-glass opacity (GGO) nodules using a phantom study. Materials and methods: A 11 cm thick transverse phantom section with a chest wall, mediastinum, and 14 artificial GGO nodules with known volumes (919.93 ± 64.05 mm 3 ) was constructed. The phantom was scanned on a Discovery CT 750HD scanner with five different NIs (NIs = 20, 30, 40, 50, and 60). All data were reconstructed with a 0.625 mm section thickness using the filtered back-projection (FBP), 50% adaptive statistical iterative reconstruction (ASiR), and Veo model-base iterative reconstruction algorithms. Image noise was measured in six regions of interest (ROIs). Nodule volumes were measured using a commercial volumetric software package. The image quality and the volume measurement errors were analysed. Results: Image noise increased dramatically from 30.7 HU at NI 20 to 122.4 HU at NI 60, with FBP reconstruction. Conversely, Veo reconstruction effectively controlled the noise increase, with an increase from 9.97 HU at NI 20 to only 15.1 HU at NI 60. Image noise at NI 60 with Veo was even lower (50.8%) than that at NI 20 with FBP. The contrast-to-noise ratio (CNR) of Veo at NI 40 was similar to that of FBP at NI 20. All artificial GGO nodules were successfully identified and measured with an average relative volume measurement error with Veo at NI 60 of 4.24%, comparable to a value of 10.41% with FBP at NI 20. At NI 60, the radiation dose was only one-tenth that at NI 20. Conclusion: The Veo reconstruction algorithms very effectively reduced image noise compared with the conventional FBP reconstructions. Using ultra-low-dose CT scanning and Veo reconstruction, GGOs can be detected and quantified with an acceptable

  17. CT colonography at low tube potential: using iterative reconstruction to decrease noise

    International Nuclear Information System (INIS)

    Chang, K.J.; Heisler, M.A.; Mahesh, M.; Baird, G.L.; Mayo-Smith, W.W.

    2015-01-01

    Aim: To determine the level of iterative reconstruction required to reduce increased image noise associated with low tube potential computed tomography (CT). Materials and methods: Fifty patients underwent CT colonography with a supine scan at 120 kVp and a prone scan at 100 kVp with other scan parameters unchanged. Both scans were reconstructed with filtered back projection (FBP) and increasing levels of adaptive statistical iterative reconstruction (ASiR) at 30%, 60%, and 90%. Mean noise, soft tissue and tagged fluid attenuation, contrast, and contrast-to-noise ratio (CNR) were collected from reconstructions at both 120 and 100 kVp and compared using a generalised linear mixed model. Results: Decreasing tube potential from 120 to 100 kVp significantly increased image noise by 30–34% and tagged fluid attenuation by 120 HU at all ASiR levels (p<0.0001, all measures). Increasing ASiR from 0% (FBP) to 30%, 60%, and 90% resulted in significant decreases in noise and increases in CNR at both tube potentials (p<0.001, all comparisons). Compared to 120 kVp FBP, ASiR greater than 30% at 100 kVp yielded similar or lower image noise. Conclusions: Iterative reconstruction adequately compensates for increased image noise associated with low tube potential imaging while improving CNR. An ASiR level of approximately 50% at 100 kVp yields similar noise to 120 kVp without ASiR. -- Highlights: •Peak kilovoltage (kVp) can be reduced to decrease radiation dose and increase contrast attenuation at a cost of increased image noise. •Utilizing iterative reconstruction can decrease image noise and increase contrast to noise ratio (CNR) independent of kVp. •Iterative reconstruction adequately compensates for increased image noise associated with low dose low kVp imaging while improving CNR. •An ASiR level of approximately 50% at 100 kVp yields similar noise to 120 kVp without ASiR

  18. Response analysis for an approximate 3-D image reconstruction in cone-beam SPECT

    International Nuclear Information System (INIS)

    Murayama, Hideo; Nohara, Norimasa

    1991-01-01

    Cone-beam single photon emission computed tomography (SPECT) offers the potential for a large increase in sensitivity as compared with parallel hole or fan-beam collimation. Three-dimensional image reconstruction was approximately accomplished by backprojecting filtered projections using a two-dimensional fan-beam algorithm. The cone-beam projection data were formed from mathematical phantoms as analytically derived line integrals of the density. In order to reduce the processing time, the filtered projections were backprojected into each plane parallel to the circle on which the focal point moved. Discrepancy of source position and degradation of resolution were investigated by computer simulation in three-dimensional image space. The results obtained suggest that, the nearer to the central plane or the axis of rotation, the less image degradation is performed. By introducing a parameter of angular difference between the focal point and a fixed point in the image space during rotation, degradation of the reconstructed image can be estimated for any cone-beam SPECT system. (author)

  19. Practical reconstruction protocol for quantitative {sup 90}Y bremsstrahlung SPECT/CT

    Energy Technology Data Exchange (ETDEWEB)

    Siman, W.; Mikell, J. K.; Kappadath, S. C., E-mail: skappadath@mdanderson.org [Department of Imaging Physics, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030 and The University of Texas Graduate School of Biomedical Sciences at Houston, Houston, Texas 77030 (United States)

    2016-09-15

    Purpose: To develop a practical background compensation (BC) technique to improve quantitative {sup 90}Y-bremsstrahlung single-photon emission computed tomography (SPECT)/computed tomography (CT) using a commercially available imaging system. Methods: All images were acquired using medium-energy collimation in six energy windows (EWs), ranging from 70 to 410 keV. The EWs were determined based on the signal-to-background ratio in planar images of an acrylic phantom of different thicknesses (2–16 cm) positioned below a {sup 90}Y source and set at different distances (15–35 cm) from a gamma camera. The authors adapted the widely used EW-based scatter-correction technique by modeling the BC as scaled images. The BC EW was determined empirically in SPECT/CT studies using an IEC phantom based on the sphere activity recovery and residual activity in the cold lung insert. The scaling factor was calculated from 20 clinical planar {sup 90}Y images. Reconstruction parameters were optimized in the same SPECT images for improved image quantification and contrast. A count-to-activity calibration factor was calculated from 30 clinical {sup 90}Y images. Results: The authors found that the most appropriate imaging EW range was 90–125 keV. BC was modeled as 0.53× images in the EW of 310–410 keV. The background-compensated clinical images had higher image contrast than uncompensated images. The maximum deviation of their SPECT calibration in clinical studies was lowest (<10%) for SPECT with attenuation correction (AC) and SPECT with AC + BC. Using the proposed SPECT-with-AC + BC reconstruction protocol, the authors found that the recovery coefficient of a 37-mm sphere (in a 10-mm volume of interest) increased from 39% to 90% and that the residual activity in the lung insert decreased from 44% to 14% over that of SPECT images with AC alone. Conclusions: The proposed EW-based BC model was developed for {sup 90}Y bremsstrahlung imaging. SPECT with AC + BC gave improved lesion

  20. Coronal reconstruction of unenhanced abdominal CT for correct ureteral stone size classification

    Energy Technology Data Exchange (ETDEWEB)

    Berkovitz, Nadav; Simanovsky, Natalia; Hiller, Nurith [Hadassah Mount Scopus - Hebrew University Medical Center, Department of Radiology, Jerusalem (Israel); Katz, Ran [Hadassah Mount Scopus - Hebrew University Medical Center, Department of Urology, Jerusalem (Israel); Salama, Shaden [Hadassah Mount Scopus - Hebrew University Medical Center, Department of Emergency Medicine, Jerusalem (Israel)

    2010-05-15

    To determine whether size measurement of a urinary calculus in coronal reconstruction of computed tomography (CT) differs from stone size measured in the axial plane, and whether the difference alters clinical decision making. We retrospectively reviewed unenhanced CT examinations of 150 patients admitted to the emergency room (ER) with acute renal colic. Maximal ureteral calculus size was measured on axial slices and coronal reconstructions. Clinical significance was defined as an upgrading or downgrading of stone size according to accepted thresholds of treatment: {<=}5 mm, 6-9 mm and {>=}10 mm. There were 151 stones in 150 patients (male:female 115:34, mean age 41 years). Transverse stone diameters ranged from 1 to 11 mm (mean 4 mm). On coronal images, 56 (37%) stones were upgraded in severity; 46 (30%) from below 5 mm to 6 mm or more, and ten (7%) from 6-9 mm to 10 mm or more. Transverse measurement on the axial slices enabled correct categorization of 95 stones (63%). Transverse calculus measurement on axial slices often underestimates stone size and provides incorrect clinical classification of the true maximal stone diameter. Coronal reconstruction provides additional information in patients with renal colic that may alter treatment strategy. (orig.)