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Sample records for metal artifact reduction

  1. MADR: metal artifact detection and reduction

    Science.gov (United States)

    Jaiswal, Sunil Prasad; Ha, Sungsoo; Mueller, Klaus

    2016-04-01

    Metal in CT-imaged objects drastically reduces the quality of these images due to the severe artifacts it can cause. Most metal artifacts reduction (MAR) algorithms consider the metal-affected sinogram portions as the corrupted data and replace them via sophisticated interpolation methods. While these schemes are successful in removing the metal artifacts, they fail to recover some of the edge information. To address these problems, the frequency shift metal artifact reduction algorithm (FSMAR) was recently proposed. It exploits the information hidden in the uncorrected image and combines the high frequency (edge) components of the uncorrected image with the low frequency components of the corrected image. Although this can effectively transfer the edge information of the uncorrected image, it also introduces some unwanted artifacts. The essential problem of these algorithms is that they lack the capability of detecting the artifacts and as a result cannot discriminate between desired and undesired edges. We propose a scheme that does better in these respects. Our Metal Artifact Detection and Reduction (MADR) scheme constructs a weight map which stores whether a pixel in the uncorrected image belongs to an artifact region or a non-artifact region. This weight matrix is optimal in the Linear Minimum Mean Square Sense (LMMSE). Our results demonstrate that MADR outperforms the existing algorithms and ensures that the anatomical structures close to metal implants are better preserved.

  2. Metal artifact reduction method using metal streaks image subtraction

    International Nuclear Information System (INIS)

    Pua, Rizza D.; Cho, Seung Ryong

    2014-01-01

    Many studies have been dedicated for metal artifact reduction (MAR); however, the methods are successful to varying degrees depending on situations. Sinogram in-painting, filtering, iterative method are some of the major categories of MAR. Each has its own merits and weaknesses. A combination of these methods or hybrid methods have also been developed to make use of the different benefits of two techniques and minimize the unfavorable results. Our method focuses on the in-paitning approach and a hybrid MAR described by Xia et al. Although in-painting scheme is an effective technique in reducing the primary metal artifacts, a major drawback is the reintroduction of new artifacts that can be caused by an inaccurate interpolation process. Furthermore, combining the segmented metal image to the corrected nonmetal image in the final step of a conventional inpainting approach causes an issue of incorrect metal pixel values. Our proposed method begins with a sinogram in-painting approach and ends with an image-based metal artifact reduction scheme. This work provides a simple, yet effective solution for reducing metal artifacts and acquiring the original metal pixel information. The proposed method demonstrated its effectiveness in a simulation setting. The proposed method showed image quality that is comparable to the standard MAR; however, quantitatively more accurate than the standard MAR

  3. Reduction of metal artifacts: beam hardening and photon starvation effects

    Science.gov (United States)

    Yadava, Girijesh K.; Pal, Debashish; Hsieh, Jiang

    2014-03-01

    The presence of metal-artifacts in CT imaging can obscure relevant anatomy and interfere with disease diagnosis. The cause and occurrence of metal-artifacts are primarily due to beam hardening, scatter, partial volume and photon starvation; however, the contribution to the artifacts from each of them depends on the type of hardware. A comparison of CT images obtained with different metallic hardware in various applications, along with acquisition and reconstruction parameters, helps understand methods for reducing or overcoming such artifacts. In this work, a metal beam hardening correction (BHC) and a projection-completion based metal artifact reduction (MAR) algorithms were developed, and applied on phantom and clinical CT scans with various metallic implants. Stainless-steel and Titanium were used to model and correct for metal beam hardening effect. In the MAR algorithm, the corrupted projection samples are replaced by the combination of original projections and in-painted data obtained by forward projecting a prior image. The data included spine fixation screws, hip-implants, dental-filling, and body extremity fixations, covering range of clinically used metal implants. Comparison of BHC and MAR on different metallic implants was used to characterize dominant source of the artifacts, and conceivable methods to overcome those. Results of the study indicate that beam hardening could be a dominant source of artifact in many spine and extremity fixations, whereas dental and hip implants could be dominant source of photon starvation. The BHC algorithm could significantly improve image quality in CT scans with metallic screws, whereas MAR algorithm could alleviate artifacts in hip-implants and dentalfillings.

  4. Assessment of metal artifact reduction methods in pelvic CT

    Energy Technology Data Exchange (ETDEWEB)

    Abdoli, Mehrsima [Department of Radiation Oncology, The Netherlands Cancer Institute, Plesmanlaan 121, Amsterdam 1066 CX (Netherlands); Mehranian, Abolfazl [Division of Nuclear Medicine and Molecular Imaging, Geneva University Hospital, Geneva CH-1211 (Switzerland); Ailianou, Angeliki; Becker, Minerva [Division of Radiology, Geneva University Hospital, Geneva CH-1211 (Switzerland); Zaidi, Habib, E-mail: habib.zaidi@hcuge.ch [Division of Nuclear Medicine and Molecular Imaging, Geneva University Hospital, Geneva CH-1211 (Switzerland); Geneva Neuroscience Center, Geneva University, Geneva CH-1205 (Switzerland); Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, Hanzeplein 1, Groningen 9700 RB (Netherlands)

    2016-04-15

    Purpose: Metal artifact reduction (MAR) produces images with improved quality potentially leading to confident and reliable clinical diagnosis and therapy planning. In this work, the authors evaluate the performance of five MAR techniques for the assessment of computed tomography images of patients with hip prostheses. Methods: Five MAR algorithms were evaluated using simulation and clinical studies. The algorithms included one-dimensional linear interpolation (LI) of the corrupted projection bins in the sinogram, two-dimensional interpolation (2D), a normalized metal artifact reduction (NMAR) technique, a metal deletion technique, and a maximum a posteriori completion (MAPC) approach. The algorithms were applied to ten simulated datasets as well as 30 clinical studies of patients with metallic hip implants. Qualitative evaluations were performed by two blinded experienced radiologists who ranked overall artifact severity and pelvic organ recognition for each algorithm by assigning scores from zero to five (zero indicating totally obscured organs with no structures identifiable and five indicating recognition with high confidence). Results: Simulation studies revealed that 2D, NMAR, and MAPC techniques performed almost equally well in all regions. LI falls behind the other approaches in terms of reducing dark streaking artifacts as well as preserving unaffected regions (p < 0.05). Visual assessment of clinical datasets revealed the superiority of NMAR and MAPC in the evaluated pelvic organs and in terms of overall image quality. Conclusions: Overall, all methods, except LI, performed equally well in artifact-free regions. Considering both clinical and simulation studies, 2D, NMAR, and MAPC seem to outperform the other techniques.

  5. Metal and calcification artifact reduction for digital breast tomosynthesis

    Science.gov (United States)

    Wicklein, Julia; Jerebko, Anna; Ritschl, Ludwig; Mertelmeier, Thomas

    2017-03-01

    Tomosynthesis images of the breast suffer from artifacts caused by the presence of highly absorbing materials. These can be either induced by metal objects like needles or clips inserted during biopsy devices, or larger calcifications inside the examined breast. Mainly two different kinds of artifacts appear after the filtered backprojection procedure. The first type is undershooting artifacts near edges of high-contrast objects caused by the filtering step. The second type is out-of-plane (ripple) artifacts that appear even in slices where the metal object or macrocalcifications does not exist. Due to the limited angular range of tomosynthesis systems, overlapping structures have high influence on neighboring regions. To overcome these problems, a segmentation of artifact introducing objects is performed on the projection images. Both projection versions, with and without high-contrast objects are filtered independently to avoid undershootings. During backprojection a decision is made for each reconstructed voxel, if it is artifact or high-contrast object. This is based on a mask image, gained from the segmentation of high-contrast objects. This procedure avoids undershooting artifacts and additionally reduces out-of-plane ripple. Results are demonstrated for different kinds of artifact inducing objects and calcifications.

  6. Ripple artifact reduction using slice overlap in slice encoding for metal artifact correction.

    Science.gov (United States)

    den Harder, J Chiel; van Yperen, Gert H; Blume, Ulrike A; Bos, Clemens

    2015-01-01

    Multispectral imaging (MSI) significantly reduces metal artifacts. Yet, especially in techniques that use gradient selection, such as slice encoding for metal artifact correction (SEMAC), a residual ripple artifact may be prominent. Here, an analysis is presented of the ripple artifact and of slice overlap as an approach to reduce the artifact. The ripple artifact was analyzed theoretically to clarify its cause. Slice overlap, conceptually similar to spectral bin overlap in multi-acquisition with variable resonances image combination (MAVRIC), was achieved by reducing the selection gradient and, thus, increasing the slice profile width. Time domain simulations and phantom experiments were performed to validate the analyses and proposed solution. Discontinuities between slices are aggravated by signal displacement in the frequency encoding direction in areas with deviating B0. Specifically, it was demonstrated that ripple artifacts appear only where B0 varies both in-plane and through-plane. Simulations and phantom studies of metal implants confirmed the efficacy of slice overlap to reduce the artifact. The ripple artifact is an important limitation of gradient selection based MSI techniques, and can be understood using the presented simulations. At a scan-time penalty, slice overlap effectively addressed the artifact, thereby improving image quality near metal implants. © 2014 Wiley Periodicals, Inc.

  7. An evaluation of three commercially available metal artifact reduction methods for CT imaging

    International Nuclear Information System (INIS)

    Huang, Jessie Y; Kerns, James R; Balter, Peter A; Followill, David S; Mirkovic, Dragan; Howell, Rebecca M; Kry, Stephen F; Nute, Jessica L; Liu, Xinming; Stingo, Francesco C

    2015-01-01

    Three commercial metal artifact reduction methods were evaluated for use in computed tomography (CT) imaging in the presence of clinically realistic metal implants: Philips O-MAR, GE’s monochromatic gemstone spectral imaging (GSI) using dual-energy CT, and GSI monochromatic imaging with metal artifact reduction software applied (MARs). Each method was evaluated according to CT number accuracy, metal size accuracy, and streak artifact severity reduction by using several phantoms, including three anthropomorphic phantoms containing metal implants (hip prosthesis, dental fillings and spinal fixation rods). All three methods showed varying degrees of success for the hip prosthesis and spinal fixation rod cases, while none were particularly beneficial for dental artifacts. Limitations of the methods were also observed. MARs underestimated the size of metal implants and introduced new artifacts in imaging planes beyond the metal implant when applied to dental artifacts, and both the O-MAR and MARs algorithms induced artifacts for spinal fixation rods in a thoracic phantom. Our findings suggest that all three artifact mitigation methods may benefit patients with metal implants, though they should be used with caution in certain scenarios. (paper)

  8. 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.

  9. Artifact reduction of different metallic implants in flat detector C-arm CT.

    Science.gov (United States)

    Hung, S-C; Wu, C-C; Lin, C-J; Guo, W-Y; Luo, C-B; Chang, F-C; Chang, C-Y

    2014-07-01

    Flat detector CT has been increasingly used as a follow-up examination after endovascular intervention. Metal artifact reduction has been successfully demonstrated in coil mass cases, but only in a small series. We attempted to objectively and subjectively evaluate the feasibility of metal artifact reduction with various metallic objects and coil lengths. We retrospectively reprocessed the flat detector CT data of 28 patients (15 men, 13 women; mean age, 55.6 years) after they underwent endovascular treatment (20 coiling ± stent placement, 6 liquid embolizers) or shunt drainage (n = 2) between January 2009 and November 2011 by using a metal artifact reduction correction algorithm. We measured CT value ranges and noise by using region-of-interest methods, and 2 experienced neuroradiologists rated the degrees of improved imaging quality and artifact reduction by comparing uncorrected and corrected images. After we applied the metal artifact reduction algorithm, the CT value ranges and the noise were substantially reduced (1815.3 ± 793.7 versus 231.7 ± 95.9 and 319.9 ± 136.6 versus 45.9 ± 14.0; both P metallic objects and various sizes of coil masses. The rater study achieved an overall improvement of imaging quality and artifact reduction (85.7% and 78.6% of cases by 2 raters, respectively), with the greatest improvement in the coiling group, moderate improvement in the liquid embolizers, and the smallest improvement in ventricular shunting (overall agreement, 0.857). The metal artifact reduction algorithm substantially reduced artifacts and improved the objective image quality in every studied case. It also allowed improved diagnostic confidence in most cases. © 2014 by American Journal of Neuroradiology.

  10. Magnetic resonance imaging of metal artifact reduction sequences in the assessment of metal-on-metal hip prostheses

    Directory of Open Access Journals (Sweden)

    Aboelmagd SM

    2014-05-01

    Full Text Available Sharief M Aboelmagd, Paul N Malcolm, Andoni P Toms Department of Radiology, Norfolk and Norwich University Hospital National Health Service Trust, Norwich, UK Abstract: Recent developments in metal artifact reduction techniques in magnetic resonance (MR have, in large part, been stimulated by the advent of soft tissue complications associated with modern metal-on-metal total hip replacements. Metallic orthopedic implants can result in severe degradation of MR images because ferromagnetic susceptibility causes signal loss, signal pile-up, geometric distortion, and failure of fat suppression. There are several approaches to controlling these susceptibility artifacts. Standard fast spin echo sequences can be adapted by modifying echo times, matrix, receiver bandwidth, slice thickness, and echo trains to minimize frequency encoding misregistration. Short tau inversion recovery and 2-point Dixon techniques are both more resistant to susceptibility artifacts than spectral fat suppression. A number of dedicated metal artifact reduction sequences are now available commercially. The common approach of these multispectral techniques is to generate three dimensional datasets from which the final images are reconstructed. Frequency encoding misregistration is controlled using a variety of techniques, including specific resonant frequency acquisition, view-angle tilting, and phase encoding. Metal artifact reduction MR imaging has been the key to understanding the prevalence, severity, and prognosis of adverse reactions to metal debris in metal-on-metal hip replacements. Conventional radiographs are typically normal or demonstrate minimal change and are unable to demonstrate the often extensive soft tissue abnormalities, which include necrosis, soft tissue masses and fluid collections, myositis, muscle atrophy, tendon avulsions, and osteonecrosis. These MR findings correlate poorly with clinical and serological measures of disease, and therefore MR imaging is

  11. Metal artifact reduction algorithm based on model images and spatial information

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Jay [Institute of Radiological Science, Central Taiwan University of Science and Technology, Taichung, Taiwan (China); Shih, Cheng-Ting [Department of Biomedical Engineering and Environmental Sciences, National Tsing-Hua University, Hsinchu, Taiwan (China); Chang, Shu-Jun [Health Physics Division, Institute of Nuclear Energy Research, Taoyuan, Taiwan (China); Huang, Tzung-Chi [Department of Biomedical Imaging and Radiological Science, China Medical University, Taichung, Taiwan (China); Sun, Jing-Yi [Institute of Radiological Science, Central Taiwan University of Science and Technology, Taichung, Taiwan (China); Wu, Tung-Hsin, E-mail: tung@ym.edu.tw [Department of Biomedical Imaging and Radiological Sciences, National Yang-Ming University, No.155, Sec. 2, Linong Street, Taipei 112, Taiwan (China)

    2011-10-01

    Computed tomography (CT) has become one of the most favorable choices for diagnosis of trauma. However, high-density metal implants can induce metal artifacts in CT images, compromising image quality. In this study, we proposed a model-based metal artifact reduction (MAR) algorithm. First, we built a model image using the k-means clustering technique with spatial information and calculated the difference between the original image and the model image. Then, the projection data of these two images were combined using an exponential weighting function. At last, the corrected image was reconstructed using the filter back-projection algorithm. Two metal-artifact contaminated images were studied. For the cylindrical water phantom image, the metal artifact was effectively removed. The mean CT number of water was improved from -28.95{+-}97.97 to -4.76{+-}4.28. For the clinical pelvic CT image, the dark band and the metal line were removed, and the continuity and uniformity of the soft tissue were recovered as well. These results indicate that the proposed MAR algorithm is useful for reducing metal artifact and could improve the diagnostic value of metal-artifact contaminated CT images.

  12. Metal artifact reduction in x-ray computed tomography (CT) by constrained optimization

    International Nuclear Information System (INIS)

    Zhang Xiaomeng; Wang Jing; Xing Lei

    2011-01-01

    Purpose: The streak artifacts caused by metal implants have long been recognized as a problem that limits various applications of CT imaging. In this work, the authors propose an iterative metal artifact reduction algorithm based on constrained optimization. Methods: After the shape and location of metal objects in the image domain is determined automatically by the binary metal identification algorithm and the segmentation of ''metal shadows'' in projection domain is done, constrained optimization is used for image reconstruction. It minimizes a predefined function that reflects a priori knowledge of the image, subject to the constraint that the estimated projection data are within a specified tolerance of the available metal-shadow-excluded projection data, with image non-negativity enforced. The minimization problem is solved through the alternation of projection-onto-convex-sets and the steepest gradient descent of the objective function. The constrained optimization algorithm is evaluated with a penalized smoothness objective. Results: The study shows that the proposed method is capable of significantly reducing metal artifacts, suppressing noise, and improving soft-tissue visibility. It outperforms the FBP-type methods and ART and EM methods and yields artifacts-free images. Conclusions: Constrained optimization is an effective way to deal with CT reconstruction with embedded metal objects. Although the method is presented in the context of metal artifacts, it is applicable to general ''missing data'' image reconstruction problems.

  13. Image-based metal artifact reduction in x-ray computed tomography utilizing local anatomical similarity

    Science.gov (United States)

    Dong, Xue; Yang, Xiaofeng; Rosenfield, Jonathan; Elder, Eric; Dhabaan, Anees

    2017-03-01

    X-ray computed tomography (CT) is widely used in radiation therapy treatment planning in recent years. However, metal implants such as dental fillings and hip prostheses can cause severe bright and dark streaking artifacts in reconstructed CT images. These artifacts decrease image contrast and degrade HU accuracy, leading to inaccuracies in target delineation and dose calculation. In this work, a metal artifact reduction method is proposed based on the intrinsic anatomical similarity between neighboring CT slices. Neighboring CT slices from the same patient exhibit similar anatomical features. Exploiting this anatomical similarity, a gamma map is calculated as a weighted summation of relative HU error and distance error for each pixel in an artifact-corrupted CT image relative to a neighboring, artifactfree image. The minimum value in the gamma map for each pixel is used to identify an appropriate pixel from the artifact-free CT slice to replace the corresponding artifact-corrupted pixel. With the proposed method, the mean CT HU error was reduced from 360 HU and 460 HU to 24 HU and 34 HU on head and pelvis CT images, respectively. Dose calculation accuracy also improved, as the dose difference was reduced from greater than 20% to less than 4%. Using 3%/3mm criteria, the gamma analysis failure rate was reduced from 23.25% to 0.02%. An image-based metal artifact reduction method is proposed that replaces corrupted image pixels with pixels from neighboring CT slices free of metal artifacts. This method is shown to be capable of suppressing streaking artifacts, thereby improving HU and dose calculation accuracy.

  14. Metal artifact reduction in CT using tissue-class modeling and adaptive prefiltering

    International Nuclear Information System (INIS)

    Bal, Matthieu; Spies, Lothar

    2006-01-01

    High-density objects such as metal prostheses, surgical clips, or dental fillings generate streak-like artifacts in computed tomography images. We present a novel method for metal artifact reduction by in-painting missing information into the corrupted sinogram. The information is provided by a tissue-class model extracted from the distorted image. To this end the image is first adaptively filtered to reduce the noise content and to smooth out streak artifacts. Consecutively, the image is segmented into different material classes using a clustering algorithm. The corrupted and missing information in the original sinogram is completed using the forward projected information from the tissue-class model. The performance of the correction method is assessed on phantom images. Clinical images featuring a broad spectrum of metal artifacts are studied. Phantom and clinical studies show that metal artifacts, such as streaks, are significantly reduced and shadows in the image are eliminated. Furthermore, the novel approach improves detectability of organ contours. This can be of great relevance, for instance, in radiation therapy planning, where images affected by metal artifacts may lead to suboptimal treatment plans

  15. Deep learning methods for CT image-domain metal artifact reduction

    Science.gov (United States)

    Gjesteby, Lars; Yang, Qingsong; Xi, Yan; Shan, Hongming; Claus, Bernhard; Jin, Yannan; De Man, Bruno; Wang, Ge

    2017-09-01

    Artifacts resulting from metal objects have been a persistent problem in CT images over the last four decades. A common approach to overcome their effects is to replace corrupt projection data with values synthesized from an interpolation scheme or by reprojection of a prior image. State-of-the-art correction methods, such as the interpolation- and normalization-based algorithm NMAR, often do not produce clinically satisfactory results. Residual image artifacts remain in challenging cases and even new artifacts can be introduced by the interpolation scheme. Metal artifacts continue to be a major impediment, particularly in radiation and proton therapy planning as well as orthopedic imaging. A new solution to the long-standing metal artifact reduction (MAR) problem is deep learning, which has been successfully applied to medical image processing and analysis tasks. In this study, we combine a convolutional neural network (CNN) with the state-of-the-art NMAR algorithm to reduce metal streaks in critical image regions. Training data was synthesized from CT simulation scans of a phantom derived from real patient images. The CNN is able to map metal-corrupted images to artifact-free monoenergetic images to achieve additional correction on top of NMAR for improved image quality. Our results indicate that deep learning is a novel tool to address CT reconstruction challenges, and may enable more accurate tumor volume estimation for radiation therapy planning.

  16. TU-F-CAMPUS-J-04: Evaluation of Metal Artifact Reduction Technique for the Radiation Therapy Planning

    International Nuclear Information System (INIS)

    Jeong, K; Kuo, H; Ritter, J; Shen, J; Basavatia, A; Yaparpalvi, R; Kalnicki, S; Tome, W

    2015-01-01

    Purpose: To evaluate the feasibility of using a metal artifact reduction technique in depleting metal artifact and its application in improving dose calculation in External Radiation Therapy Planning. Methods: CIRS electron density phantom was scanned with and without steel drill bits placed in some plug holes. Meta artifact reduction software with Metal Deletion Technique (MDT) was used to remove metal artifacts for scanned image with metal. Hounsfield units of electron density plugs from artifact free reference image and MDT processed images were compared. To test the dose calculation improvement after the MDT processed images, clinically approved head and neck plan with manual dental artifact correction was tested. Patient images were exported and processed with MDT and plan was recalculated with new MDT image without manual correction. Dose profiles near the metal artifacts were compared. Results: The MDT used in this study effectively reduced the metal artifact caused by beam hardening and scatter. The windmill around the metal drill was greatly improved with smooth rounded view. Difference of the mean HU in each density plug between reference and MDT images were less than 10 HU in most of the plugs. Dose difference between original plan and MDT images were minimal. Conclusion: Most metal artifact reduction methods were developed for diagnostic improvement purpose. Hence Hounsfield unit accuracy was not rigorously tested before. In our test, MDT effectively eliminated metal artifacts with good HU reproduciblity. However, it can introduce new mild artifacts so the MDT images should be checked with original images

  17. Metal artifact reduction of CT scans to improve PET/CT

    NARCIS (Netherlands)

    Van Der Vos, Charlotte S.; Arens, Anne I.J.; Hamill, James J.; Hofmann, Christian; Panin, Vladimir Y.; Meeuwis, Antoi P.W.; Visser, Eric P.; De Geus-Oei, Lioe Fee

    2017-01-01

    In recent years, different metal artifact reduction methods have been developed for CT. These methods have only recently been introduced for PET/CT even though they could be beneficial for interpretation, segmentation, and quantification of the PET/CT images. In this study, phantom and patient scans

  18. Metal Artifact Reduction of CT Scans to Improve PET/CT

    NARCIS (Netherlands)

    Vos, C.S. van der; Arens, A.I.J.; Hamill, J.J.; Hofmann, C.; Panin, V.Y.; Meeuwis, A.P.W.; Visser, E.P.; Geus-Oei, L.F. de

    2017-01-01

    In recent years, different metal artifact reduction methods have been developed for CT. These methods have only recently been introduced for PET/CT even though they could be beneficial for interpretation, segmentation, and quantification of the PET/CT images. In this study, phantom and patient scans

  19. Complementary contrast media for metal artifact reduction in dual-energy computed tomography.

    Science.gov (United States)

    Lambert, Jack W; Edic, Peter M; FitzGerald, Paul F; Torres, Andrew S; Yeh, Benjamin M

    2015-07-01

    Metal artifacts have been a problem associated with computed tomography (CT) since its introduction. Recent techniques to mitigate this problem have included utilization of high-energy (keV) virtual monochromatic spectral (VMS) images, produced via dual-energy CT (DECT). A problem with these high-keV images is that contrast enhancement provided by all commercially available contrast media is severely reduced. Contrast agents based on higher atomic number elements can maintain contrast at the higher energy levels where artifacts are reduced. This study evaluated three such candidate elements: bismuth, tantalum, and tungsten, as well as two conventional contrast elements: iodine and barium. A water-based phantom with vials containing these five elements in solution, as well as different artifact-producing metal structures, was scanned with a DECT scanner capable of rapid operating voltage switching. In the VMS datasets, substantial reductions in the contrast were observed for iodine and barium, which suffered from contrast reductions of 97% and 91%, respectively, at 140 versus 40 keV. In comparison under the same conditions, the candidate agents demonstrated contrast enhancement reductions of only 20%, 29%, and 32% for tungsten, tantalum, and bismuth, respectively. At 140 versus 40 keV, metal artifact severity was reduced by 57% to 85% depending on the phantom configuration.

  20. Iterative metal artifact reduction for x-ray computed tomography using unmatched projector/backprojector pairs

    International Nuclear Information System (INIS)

    Zhang, Hanming; Wang, Linyuan; Li, Lei; Cai, Ailong; Hu, Guoen; Yan, Bin

    2016-01-01

    Purpose: Metal artifact reduction (MAR) is a major problem and a challenging issue in x-ray computed tomography (CT) examinations. Iterative reconstruction from sinograms unaffected by metals shows promising potential in detail recovery. This reconstruction has been the subject of much research in recent years. However, conventional iterative reconstruction methods easily introduce new artifacts around metal implants because of incomplete data reconstruction and inconsistencies in practical data acquisition. Hence, this work aims at developing a method to suppress newly introduced artifacts and improve the image quality around metal implants for the iterative MAR scheme. Methods: The proposed method consists of two steps based on the general iterative MAR framework. An uncorrected image is initially reconstructed, and the corresponding metal trace is obtained. The iterative reconstruction method is then used to reconstruct images from the unaffected sinogram. In the reconstruction step of this work, an iterative strategy utilizing unmatched projector/backprojector pairs is used. A ramp filter is introduced into the back-projection procedure to restrain the inconsistency components in low frequencies and generate more reliable images of the regions around metals. Furthermore, a constrained total variation (TV) minimization model is also incorporated to enhance efficiency. The proposed strategy is implemented based on an iterative FBP and an alternating direction minimization (ADM) scheme, respectively. The developed algorithms are referred to as “iFBP-TV” and “TV-FADM,” respectively. Two projection-completion-based MAR methods and three iterative MAR methods are performed simultaneously for comparison. Results: The proposed method performs reasonably on both simulation and real CT-scanned datasets. This approach could reduce streak metal artifacts effectively and avoid the mentioned effects in the vicinity of the metals. The improvements are evaluated by

  1. Metal artifact reduction in x-ray computed tomography by using analytical DBP-type algorithm

    Science.gov (United States)

    Wang, Zhen; Kudo, Hiroyuki

    2012-03-01

    This paper investigates a common metal artifacts problem in X-ray computed tomography (CT). The artifacts in reconstructed image may render image non-diagnostic because of inaccuracy beam hardening correction from high attenuation objects, satisfactory image could not be reconstructed from projections with missing or distorted data. In traditionally analytical metal artifact reduction (MAR) method, firstly subtract the metallic object part of projection data from the original obtained projection, secondly complete the subtracted part in original projection by using various interpolating method, thirdly reconstruction from the interpolated projection by filtered back-projection (FBP) algorithm. The interpolation error occurred during the second step can make unrealistic assumptions about the missing data, leading to DC shift artifact in the reconstructed images. We proposed a differentiated back-projection (DBP) type MAR method by instead of FBP algorithm with DBP algorithm in third step. In FBP algorithm the interpolated projection will be filtered on each projection view angle before back-projection, as a result the interpolation error is propagated to whole projection. However, the property of DBP algorithm provide a chance to do filter after the back-projection in a Hilbert filter direction, as a result the interpolation error affection would be reduce and there is expectation on improving quality of reconstructed images. In other word, if we choose the DBP algorithm instead of the FBP algorithm, less contaminated projection data with interpolation error would be used in reconstruction. A simulation study was performed to evaluate the proposed method using a given phantom.

  2. Spectral CT with monochromatic imaging and metal artifacts reduction software for artifacts reduction of ¹²⁵I radioactive seeds in liver brachytherapy.

    Science.gov (United States)

    Yang, Qiuxia; Peng, Sheng; Wu, Jing; Ban, Xiaohua; He, Mingyan; Xie, Chuanmiao; Zhang, Rong

    2015-11-01

    To investigate the optimal monochromatic energy for artifacts reduction from (125)I seeds as well as image improvement in the vicinity of seeds on monochromatic images with and without metal artifacts reduction software (MARS) and to compare this with traditional 120-kVp images, so as to evaluate the application value of gemstone spectral imaging for reducing artifacts from (125)I seeds in liver brachytherapy. A total of 45 tumors from 25 patients treated with (125)I seed brachytherapy in the liver were enrolled in this study. Multiphasic spectral computed tomography (CT) scanning was performed for each patient. After a delay time of 15 s of portal vein phase, a traditional 120-kVp scan was performed, focusing on several planes of (125)I seeds only. The artifact index (AI) in the vicinity of seeds and the standard deviation (SD) of the CT density of region of interest in the outside liver parenchyma were calculated. Artifact appearance was evaluated and classified on reconstructed monochromatic S and 120-kVp images. Image quality in the vicinity of seeds of three data sets were evaluated using a 1-5 scale scoring method. The Friedman rank-sum test was used to estimate the scoring results of image quality. The greatest noise in monochromatic images was found at 40 keV (SD = 27.38, AI = 206.40). The optimal monochromatic energy was found at 75 keV, which provided almost the least image noise (SD = 10.01) and good performance in artifact reduction (AI = 102.73). Image noise and AI reduction at 75 keV was decreased by 63.44 and 50.23%, compared with at 40 keV. Near-field thick artifacts were obvious in all 45 lesions, in 120-kVp images, and 75-keV images, but basically reduced in 75 keV MARS images and artifacts completely invisible in 7 lesions. The number of diagnosable images (score ≥3) was significantly more in the 75-keV MARS group (28/45), and the 75-keV group (22/45) than in the 120-kVp group (11/45) (p improve image quality, even to a state of being

  3. Metal Artifacts Reduction of Pedicle Screws on Spine Computed Tomography Images Using Variable Thresholding Technique

    International Nuclear Information System (INIS)

    Kaewlek, T.; Koolpiruck, D.; Thongvigitmanee, S.; Mongkolsuk, M.; Chiewvit, P.; Thammakittiphan, S.

    2012-01-01

    Metal artifacts are one of significant problems in computed tomography (CT). The streak lines and air gaps arise from metal implants of orthopedic patients, such as prosthesis, dental bucket, and pedicle screws that cause incorrect diagnosis and local treatment planning. A common technique to suppressed artifacts is by adjusting windows, but those artifacts still remain on the images. To improve the detail of spine CT images, the variable thresholding technique is proposed in this paper. Three medical cases of spine CT images categorized by the severity of artifacts (screws head, one full screw, and two full screws) were investigated. Metal regions were segmented by k-mean clustering, then transformed into a sinogram domain. The metal sinogram was identified by the variable thresholding method, and then replaced the new estimated values by linear interpolation. The modified sinogram was reconstructed by the filtered back- projection algorithm, and added the metal region back to the modified reconstructed image in order to reproduce the final image. The image quality of the proposed technique, the automatic thresholding (Kalender) technique, and window adjustment technique was compared in term of noise and signal to noise ratio (SNR). The propose method can reduce metal artifacts between pedicle screws. After processing by our proposed technique, noise in the modified images is reduced (screws head 121.15 to73.83, one full screw 160.88 to 94.04, and two full screws 199.73 to 110.05 from the initial image) and SNR is increased (screws head 0.87 to 1.88, one full screw 1.54 to 2.82, and two full screws 0.32 to 0.41 from the initial image). The variable thresholding technique can identify the suitable boundary for restoring the missing data. The efficiency of the metal artifacts reduction is indicated on the case of partial and full pedicle screws. Our technique can improve the detail of spine CT images better than automatic thresholding (Kalender) technique, and

  4. A novel forward projection-based metal artifact reduction method for flat-detector computed tomography

    Energy Technology Data Exchange (ETDEWEB)

    Prell, Daniel; Kyriakou, Yiannis; Beister, Marcel; Kalender, Willi A [Institute of Medical Physics, University of Erlangen-Nuernberg, Henkestrasse 91, 91052 Erlangen (Germany)], E-mail: daniel.prell@imp.uni-erlangen.de

    2009-11-07

    Metallic implants generate streak-like artifacts in flat-detector computed tomography (FD-CT) reconstructed volumetric images. This study presents a novel method for reducing these disturbing artifacts by inserting discarded information into the original rawdata using a three-step correction procedure and working directly with each detector element. Computation times are minimized by completely implementing the correction process on graphics processing units (GPUs). First, the original volume is corrected using a three-dimensional interpolation scheme in the rawdata domain, followed by a second reconstruction. This metal artifact-reduced volume is then segmented into three materials, i.e. air, soft-tissue and bone, using a threshold-based algorithm. Subsequently, a forward projection of the obtained tissue-class model substitutes the missing or corrupted attenuation values directly for each flat detector element that contains attenuation values corresponding to metal parts, followed by a final reconstruction. Experiments using tissue-equivalent phantoms showed a significant reduction of metal artifacts (deviations of CT values after correction compared to measurements without metallic inserts reduced typically to below 20 HU, differences in image noise to below 5 HU) caused by the implants and no significant resolution losses even in areas close to the inserts. To cover a variety of different cases, cadaver measurements and clinical images in the knee, head and spine region were used to investigate the effectiveness and applicability of our method. A comparison to a three-dimensional interpolation correction showed that the new approach outperformed interpolation schemes. Correction times are minimized, and initial and corrected images are made available at almost the same time (12.7 s for the initial reconstruction, 46.2 s for the final corrected image compared to 114.1 s and 355.1 s on central processing units (CPUs))

  5. A novel forward projection-based metal artifact reduction method for flat-detector computed tomography

    International Nuclear Information System (INIS)

    Prell, Daniel; Kyriakou, Yiannis; Beister, Marcel; Kalender, Willi A

    2009-01-01

    Metallic implants generate streak-like artifacts in flat-detector computed tomography (FD-CT) reconstructed volumetric images. This study presents a novel method for reducing these disturbing artifacts by inserting discarded information into the original rawdata using a three-step correction procedure and working directly with each detector element. Computation times are minimized by completely implementing the correction process on graphics processing units (GPUs). First, the original volume is corrected using a three-dimensional interpolation scheme in the rawdata domain, followed by a second reconstruction. This metal artifact-reduced volume is then segmented into three materials, i.e. air, soft-tissue and bone, using a threshold-based algorithm. Subsequently, a forward projection of the obtained tissue-class model substitutes the missing or corrupted attenuation values directly for each flat detector element that contains attenuation values corresponding to metal parts, followed by a final reconstruction. Experiments using tissue-equivalent phantoms showed a significant reduction of metal artifacts (deviations of CT values after correction compared to measurements without metallic inserts reduced typically to below 20 HU, differences in image noise to below 5 HU) caused by the implants and no significant resolution losses even in areas close to the inserts. To cover a variety of different cases, cadaver measurements and clinical images in the knee, head and spine region were used to investigate the effectiveness and applicability of our method. A comparison to a three-dimensional interpolation correction showed that the new approach outperformed interpolation schemes. Correction times are minimized, and initial and corrected images are made available at almost the same time (12.7 s for the initial reconstruction, 46.2 s for the final corrected image compared to 114.1 s and 355.1 s on central processing units (CPUs)).

  6. Reduction of artifacts caused by orthopedic hardware in the spine in spectral detector CT examinations using virtual monoenergetic image reconstructions and metal-artifact-reduction algorithms

    Energy Technology Data Exchange (ETDEWEB)

    Grosse Hokamp, Nils; Neuhaus, V.; Abdullayev, N.; Laukamp, K.; Lennartz, S.; Mpotsaris, A.; Borggrefe, J. [University Hospital Cologne, Department of Diagnostic and Interventional Radiology, Cologne (Germany)

    2018-02-15

    Aim of this study was to assess the artifact reduction in patients with orthopedic hardware in the spine as provided by (1) metal-artifact-reduction algorithms (O-MAR) and (2) virtual monoenergetic images (MonoE) as provided by spectral detector CT (SDCT) compared to conventional iterative reconstruction (CI). In all, 28 consecutive patients with orthopedic hardware in the spine who underwent SDCT-examinations were included. CI, O-MAR and MonoE (40-200 keV) images were reconstructed. Attenuation (HU) and noise (SD) were measured in order to calculate signal-to-noise ratio (SNR) of paravertebral muscle and spinal canal. Subjective image quality was assessed by two radiologists in terms of image quality and extent of artifact reduction. O-MAR and high-keV MonoE showed significant decrease of hypodense artifacts in terms of higher attenuation as compared to CI (CI vs O-MAR, 200 keV MonoE: -396.5HU vs. -115.2HU, -48.1HU; both p ≤ 0.001). Further, artifacts as depicted by noise were reduced in O-MAR and high-keV MonoE as compared to CI in (1) paravertebral muscle and (2) spinal canal - CI vs. O-MAR/200 keV: (1) 34.7 ± 19.0 HU vs. 26.4 ± 14.4 HU, p ≤ 0.05/27.4 ± 16.1, n.s.; (2) 103.4 ± 61.3 HU vs. 72.6 ± 62.6 HU/60.9 ± 40.1 HU, both p ≤ 0.001. Subjectively both O-MAR and high-keV images yielded an artifact reduction in up to 24/28 patients. Both, O-MAR and high-keV MonoE reconstructions as provided by SDCT lead to objective and subjective artifact reduction, thus the combination of O-MAR and MonoE seems promising for further reduction. (orig.)

  7. Metal artifact reduction image reconstruction algorithm for CT of implanted metal orthopedic devices: a work in progress

    International Nuclear Information System (INIS)

    Liu, Patrick T.; Pavlicek, William P.; Peter, Mary B.; Roberts, Catherine C.; Paden, Robert G.; Spangehl, Mark J.

    2009-01-01

    Despite recent advances in CT technology, metal orthopedic implants continue to cause significant artifacts on many CT exams, often obscuring diagnostic information. We performed this prospective study to evaluate the effectiveness of an experimental metal artifact reduction (MAR) image reconstruction program for CT. We examined image quality on CT exams performed in patients with hip arthroplasties as well as other types of implanted metal orthopedic devices. The exam raw data were reconstructed using two different methods, the standard filtered backprojection (FBP) program and the MAR program. Images were evaluated for quality of the metal-cement-bone interfaces, trabeculae ≤1 cm from the metal, trabeculae 5 cm apart from the metal, streak artifact, and overall soft tissue detail. The Wilcoxon Rank Sum test was used to compare the image scores from the large and small prostheses. Interobserver agreement was calculated. When all patients were grouped together, the MAR images showed mild to moderate improvement over the FBP images. However, when the cases were divided by implant size, the MAR images consistently received higher image quality scores than the FBP images for large metal implants (total hip prostheses). For small metal implants (screws, plates, staples), conversely, the MAR images received lower image quality scores than the FBP images due to blurring artifact. The difference of image scores for the large and small implants was significant (p=0.002). Interobserver agreement was found to be high for all measures of image quality (k>0.9). The experimental MAR reconstruction algorithm significantly improved CT image quality for patients with large metal implants. However, the MAR algorithm introduced blurring artifact that reduced image quality with small metal implants. (orig.)

  8. Moving metal artifact reduction in cone-beam CT scans with implanted cylindrical gold markers

    International Nuclear Information System (INIS)

    Toftegaard, Jakob; Fledelius, Walther; Worm, Esben S.; Poulsen, Per R.; Seghers, Dieter; Huber, Michael; Brehm, Marcus; Elstrøm, Ulrik V.

    2014-01-01

    Purpose: Implanted gold markers for image-guided radiotherapy lead to streaking artifacts in cone-beam CT (CBCT) scans. Several methods for metal artifact reduction (MAR) have been published, but they all fail in scans with large motion. Here the authors propose and investigate a method for automatic moving metal artifact reduction (MMAR) in CBCT scans with cylindrical gold markers. Methods: The MMAR CBCT reconstruction method has six steps. (1) Automatic segmentation of the cylindrical markers in the CBCT projections. (2) Removal of each marker in the projections by replacing the pixels within a masked area with interpolated values. (3) Reconstruction of a marker-free CBCT volume from the manipulated CBCT projections. (4) Reconstruction of a standard CBCT volume with metal artifacts from the original CBCT projections. (5) Estimation of the three-dimensional (3D) trajectory during CBCT acquisition for each marker based on the segmentation in Step 1, and identification of the smallest ellipsoidal volume that encompasses 95% of the visited 3D positions. (6) Generation of the final MMAR CBCT reconstruction from the marker-free CBCT volume of Step 3 by replacing the voxels in the 95% ellipsoid with the corresponding voxels of the standard CBCT volume of Step 4. The MMAR reconstruction was performed retrospectively using a half-fan CBCT scan for 29 consecutive stereotactic body radiation therapy patients with 2–3 gold markers implanted in the liver. The metal artifacts of the MMAR reconstructions were scored and compared with a standard MAR reconstruction by counting the streaks and by calculating the standard deviation of the Hounsfield units in a region around each marker. Results: The markers were found with the same autosegmentation settings in 27 CBCT scans, while two scans needed slightly changed settings to find all markers automatically in Step 1 of the MMAR method. MMAR resulted in 15 scans with no streaking artifacts, 11 scans with 1–4 streaks, and 3 scans

  9. Evaluating applicability of metal artifact reduction algorithm for head and neck radiation treatment planning CT

    International Nuclear Information System (INIS)

    Son, Sang Jun; Park, Jang Pil; Kim, Min Jeong; Yoo, Suk Hyun

    2014-01-01

    The purpose of this study is evaluation for the applicability of O-MAR(Metal artifact Reduction for Orthopedic Implants)(ver. 3.6.0, Philips, Netherlands) in head and neck radiation treatment planning CT with metal artifact created by dental implant. All of the in this study's CT images were scanned by Brilliance Big Bore CT(Philips, Netherlands) at 120 kVp, 2 mm sliced and Metal artifact reduced by O-MAR. To compare the original and reconstructed CT images worked on RTPS(Eclipse ver 10.0.42, Varian, USA). In order to test the basic performance of the O-MAR, The phantom was made to create metal artifact by dental implant and other phantoms used for without artifact images. To measure a difference of HU in with artifact images and without artifact images, homogeneous phantom and inhomogeneous phantoms were used with cerrobend rods. Each of images were compared a difference of HU in ROIs. And also, 1 case of patient's original CT image applied O-MAR and density corrected CT were evaluated for dose distributions with SNC Patient(Sun Nuclear Co., USA). In cases of head and neck phantom, the difference of dose distribution is appeared 99.8% gamma passing rate(criteria 2 mm / 2%) between original and CT images applied O-MAR. And 98.5% appeared in patient case, among original CT, O-MAR and density corrected CT. The difference of total dose distribution is less than 2% that appeared both phantom and patient case study. Though the dose deviations are little, there are still matters to discuss that the dose deviations are concentrated so locally. In this study, The quality of all images applied O-MAR was improved. Unexpectedly, Increase of max. HU was founded in air cavity of the O-MAR images compare to cavity of the original images and wrong corrections were appeared, too. The result of study assuming restrained case of O-MAR adapted to near skin and low density area, it appeared image distortion and artifact correction simultaneously. In O-MAR CT, air cavity area

  10. Observer Evaluation of a Metal Artifact Reduction Algorithm Applied to Head and Neck Cone Beam Computed Tomographic Images

    Energy Technology Data Exchange (ETDEWEB)

    Korpics, Mark; Surucu, Murat; Mescioglu, Ibrahim; Alite, Fiori; Block, Alec M.; Choi, Mehee; Emami, Bahman; Harkenrider, Matthew M.; Solanki, Abhishek A.; Roeske, John C., E-mail: jroeske@lumc.edu

    2016-11-15

    Purpose and Objectives: To quantify, through an observer study, the reduction in metal artifacts on cone beam computed tomographic (CBCT) images using a projection-interpolation algorithm, on images containing metal artifacts from dental fillings and implants in patients treated for head and neck (H&N) cancer. Methods and Materials: An interpolation-substitution algorithm was applied to H&N CBCT images containing metal artifacts from dental fillings and implants. Image quality with respect to metal artifacts was evaluated subjectively and objectively. First, 6 independent radiation oncologists were asked to rank randomly sorted blinded images (before and after metal artifact reduction) using a 5-point rating scale (1 = severe artifacts; 5 = no artifacts). Second, the standard deviation of different regions of interest (ROI) within each image was calculated and compared with the mean rating scores. Results: The interpolation-substitution technique successfully reduced metal artifacts in 70% of the cases. From a total of 60 images from 15 H&N cancer patients undergoing image guided radiation therapy, the mean rating score on the uncorrected images was 2.3 ± 1.1, versus 3.3 ± 1.0 for the corrected images. The mean difference in ranking score between uncorrected and corrected images was 1.0 (95% confidence interval: 0.9-1.2, P<.05). The standard deviation of each ROI significantly decreased after artifact reduction (P<.01). Moreover, a negative correlation between the mean rating score for each image and the standard deviation of the oral cavity and bilateral cheeks was observed. Conclusion: The interpolation-substitution algorithm is efficient and effective for reducing metal artifacts caused by dental fillings and implants on CBCT images, as demonstrated by the statistically significant increase in observer image quality ranking and by the decrease in ROI standard deviation between uncorrected and corrected images.

  11. Iterative metal artifact reduction improves dose calculation accuracy. Phantom study with dental implants

    Energy Technology Data Exchange (ETDEWEB)

    Maerz, Manuel; Mittermair, Pia; Koelbl, Oliver; Dobler, Barbara [Regensburg University Medical Center, Department of Radiotherapy, Regensburg (Germany); Krauss, Andreas [Siemens Healthcare GmbH, Forchheim (Germany)

    2016-06-15

    Metallic dental implants cause severe streaking artifacts in computed tomography (CT) data, which affect the accuracy of dose calculations in radiation therapy. The aim of this study was to investigate the benefit of the metal artifact reduction algorithm iterative metal artifact reduction (iMAR) in terms of correct representation of Hounsfield units (HU) and dose calculation accuracy. Heterogeneous phantoms consisting of different types of tissue equivalent material surrounding metallic dental implants were designed. Artifact-containing CT data of the phantoms were corrected using iMAR. Corrected and uncorrected CT data were compared to synthetic CT data to evaluate accuracy of HU reproduction. Intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) plans were calculated in Oncentra v4.3 on corrected and uncorrected CT data and compared to Gafchromic trademark EBT3 films to assess accuracy of dose calculation. The use of iMAR increased the accuracy of HU reproduction. The average deviation of HU decreased from 1006 HU to 408 HU in areas including metal and from 283 HU to 33 HU in tissue areas excluding metal. Dose calculation accuracy could be significantly improved for all phantoms and plans: The mean passing rate for gamma evaluation with 3 % dose tolerance and 3 mm distance to agreement increased from 90.6 % to 96.2 % if artifacts were corrected by iMAR. The application of iMAR allows metal artifacts to be removed to a great extent which leads to a significant increase in dose calculation accuracy. (orig.) [German] Metallische Implantate verursachen streifenfoermige Artefakte in CT-Bildern, welche die Dosisberechnung beeinflussen. In dieser Studie soll der Nutzen des iterativen Metall-Artefakt-Reduktions-Algorithmus iMAR hinsichtlich der Wiedergabetreue von Hounsfield-Werten (HU) und der Genauigkeit von Dosisberechnungen untersucht werden. Es wurden heterogene Phantome aus verschiedenen Arten gewebeaequivalenten Materials mit

  12. Analysis of metal artifact reduction tools for dental hardware in CT scans of the oral cavity: kVp, iterative reconstruction, dual-energy CT, metal artifact reduction software: does it make a difference?

    Energy Technology Data Exchange (ETDEWEB)

    Crop, An de; Hoof, Tom van; Herde, Katharina d' ; Thierens, Hubert; Bacher, Klaus [Ghent University, Department of Basic Medical Sciences, Gent (Belgium); Casselman, Jan; Vereecke, Elke; Bossu, Nicolas [AZ Sint Jan Bruges Ostend AV, Department of Radiology, Bruges (Belgium); Dierens, Melissa [Ghent University, Dental School, Unit for Oral and Maxillofacial Imaging, Ghent (Belgium); Pamplona, Jaime [Hospital Lisboa Central, Department of Neuroradiology, Lisbon (Portugal)

    2015-08-15

    Metal artifacts may negatively affect radiologic assessment in the oral cavity. The aim of this study was to evaluate different metal artifact reduction techniques for metal artifacts induced by dental hardware in CT scans of the oral cavity. Clinical image quality was assessed using a Thiel-embalmed cadaver. A Catphan phantom and a polymethylmethacrylate (PMMA) phantom were used to evaluate physical-technical image quality parameters such as artifact area, artifact index (AI), and contrast detail (IQF{sub inv}). Metal cylinders were inserted in each phantom to create metal artifacts. CT images of both phantoms and the Thiel-embalmed cadaver were acquired on a multislice CT scanner using 80, 100, 120, and 140 kVp; model-based iterative reconstruction (Veo); and synthesized monochromatic keV images with and without metal artifact reduction software (MARs). Four radiologists assessed the clinical image quality, using an image criteria score (ICS). Significant influence of increasing kVp and the use of Veo was found on clinical image quality (p = 0.007 and p = 0.014, respectively). Application of MARs resulted in a smaller artifact area (p < 0.05). However, MARs reconstructed images resulted in lower ICS. Of all investigated techniques, Veo shows to be most promising, with a significant improvement of both the clinical and physical-technical image quality without adversely affecting contrast detail. MARs reconstruction in CT images of the oral cavity to reduce dental hardware metallic artifacts is not sufficient and may even adversely influence the image quality. (orig.)

  13. Value and clinical application of orthopedic metal artifact reduction algorithm in CT scans after orthopedic metal implantation

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Yi; Pan, Shinong; Zhao, Xudong; Guo, Wenli; He, Ming; Guo, Qiyong [Shengjing Hospital of China Medical University, Shenyang (China)

    2017-06-15

    To evaluate orthopedic metal artifact reduction algorithm (O-MAR) in CT orthopedic metal artifact reduction at different tube voltages, identify an appropriate low tube voltage for clinical practice, and investigate its clinical application. The institutional ethical committee approved all the animal procedures. A stainless-steel plate and four screws were implanted into the femurs of three Japanese white rabbits. Preoperative CT was performed at 120 kVp without O-MAR reconstruction, and postoperative CT was performed at 80–140 kVp with O-MAR. Muscular CT attenuation, artifact index (AI) and signal-to-noise ratio (SNR) were compared between preoperative and postoperative images (unpaired t test), between paired O-MAR and non-O-MAR images (paired Student t test) and among different kVp settings (repeated measures ANOVA). Artifacts' severity, muscular homogeneity, visibility of inter-muscular space and definition of bony structures were subjectively evaluated and compared (Wilcoxon rank-sum test). In the clinical study, 20 patients undertook CT scan at low kVp with O-MAR with informed consent. The diagnostic satisfaction of clinical images was subjectively assessed. Animal experiments showed that the use of O-MAR resulted in accurate CT attenuation, lower AI, better SNR, and higher subjective scores (p < 0.010) at all tube voltages. O-MAR images at 100 kVp had almost the same AI and SNR as non-O-MAR images at 140 kVp. All O-MAR images were scored ≥ 3. In addition, 95% of clinical CT images performed at 100 kVp were considered satisfactory. O-MAR can effectively reduce orthopedic metal artifacts at different tube voltages, and facilitates low-tube-voltage CT for patients with orthopedic metal implants.

  14. Value and clinical application of orthopedic metal artifact reduction algorithm in CT scans after orthopedic metal implantation

    International Nuclear Information System (INIS)

    Hu, Yi; Pan, Shinong; Zhao, Xudong; Guo, Wenli; He, Ming; Guo, Qiyong

    2017-01-01

    To evaluate orthopedic metal artifact reduction algorithm (O-MAR) in CT orthopedic metal artifact reduction at different tube voltages, identify an appropriate low tube voltage for clinical practice, and investigate its clinical application. The institutional ethical committee approved all the animal procedures. A stainless-steel plate and four screws were implanted into the femurs of three Japanese white rabbits. Preoperative CT was performed at 120 kVp without O-MAR reconstruction, and postoperative CT was performed at 80–140 kVp with O-MAR. Muscular CT attenuation, artifact index (AI) and signal-to-noise ratio (SNR) were compared between preoperative and postoperative images (unpaired t test), between paired O-MAR and non-O-MAR images (paired Student t test) and among different kVp settings (repeated measures ANOVA). Artifacts' severity, muscular homogeneity, visibility of inter-muscular space and definition of bony structures were subjectively evaluated and compared (Wilcoxon rank-sum test). In the clinical study, 20 patients undertook CT scan at low kVp with O-MAR with informed consent. The diagnostic satisfaction of clinical images was subjectively assessed. Animal experiments showed that the use of O-MAR resulted in accurate CT attenuation, lower AI, better SNR, and higher subjective scores (p < 0.010) at all tube voltages. O-MAR images at 100 kVp had almost the same AI and SNR as non-O-MAR images at 140 kVp. All O-MAR images were scored ≥ 3. In addition, 95% of clinical CT images performed at 100 kVp were considered satisfactory. O-MAR can effectively reduce orthopedic metal artifacts at different tube voltages, and facilitates low-tube-voltage CT for patients with orthopedic metal implants

  15. Exploring metal artifact reduction using dual-energy CT with pre-metal and post-metal implant cadaver comparison: are implant specific protocols needed?

    NARCIS (Netherlands)

    Wellenberg, Ruud H. H.; Donders, Johanna C. E.; Kloen, Peter; Beenen, Ludo F. M.; Kleipool, Roeland P.; Maas, Mario; Streekstra, Geert J.

    2017-01-01

    To quantify and optimize metal artifact reduction using virtual monochromatic dual-energy CT for different metal implants compared to non-metal reference scans. Dual-energy CT scans of a pair of human cadaver limbs were acquired before and after implanting a titanium tibia plate, a stainless-steel

  16. Quantitative comparison of commercial and non-commercial metal artifact reduction techniques in computed tomography.

    Directory of Open Access Journals (Sweden)

    Dirk Wagenaar

    Full Text Available Typical streak artifacts known as metal artifacts occur in the presence of strongly attenuating materials in computed tomography (CT. Recently, vendors have started offering metal artifact reduction (MAR techniques. In addition, a MAR technique called the metal deletion technique (MDT is freely available and able to reduce metal artifacts using reconstructed images. Although a comparison of the MDT to other MAR techniques exists, a comparison of commercially available MAR techniques is lacking. The aim of this study was therefore to quantify the difference in effectiveness of the currently available MAR techniques of different scanners and the MDT technique.Three vendors were asked to use their preferential CT scanner for applying their MAR techniques. The scans were performed on a Philips Brilliance ICT 256 (S1, a GE Discovery CT 750 HD (S2 and a Siemens Somatom Definition AS Open (S3. The scans were made using an anthropomorphic head and neck phantom (Kyoto Kagaku, Japan. Three amalgam dental implants were constructed and inserted between the phantom's teeth. The average absolute error (AAE was calculated for all reconstructions in the proximity of the amalgam implants.The commercial techniques reduced the AAE by 22.0±1.6%, 16.2±2.6% and 3.3±0.7% for S1 to S3 respectively. After applying the MDT to uncorrected scans of each scanner the AAE was reduced by 26.1±2.3%, 27.9±1.0% and 28.8±0.5% respectively. The difference in efficiency between the commercial techniques and the MDT was statistically significant for S2 (p=0.004 and S3 (p<0.001, but not for S1 (p=0.63.The effectiveness of MAR differs between vendors. S1 performed slightly better than S2 and both performed better than S3. Furthermore, for our phantom and outcome measure the MDT was more effective than the commercial MAR technique on all scanners.

  17. SU-C-206-03: Metal Artifact Reduction in X-Ray Computed Tomography Based On Local Anatomical Similarity

    International Nuclear Information System (INIS)

    Dong, X; Yang, X; Rosenfield, J; Elder, E; Dhabaan, A

    2016-01-01

    Purpose: Metal implants such as orthopedic hardware and dental fillings cause severe bright and dark streaking in reconstructed CT images. These artifacts decrease image contrast and degrade HU accuracy, leading to inaccuracies in target delineation and dose calculation. Additionally, such artifacts negatively impact patient set-up in image guided radiation therapy (IGRT). In this work, we propose a novel method for metal artifact reduction which utilizes the anatomical similarity between neighboring CT slices. Methods: Neighboring CT slices show similar anatomy. Based on this anatomical similarity, the proposed method replaces corrupted CT pixels with pixels from adjacent, artifact-free slices. A gamma map, which is the weighted summation of relative HU error and distance error, is calculated for each pixel in the artifact-corrupted CT image. The minimum value in each pixel’s gamma map is used to identify a pixel from the adjacent CT slice to replace the corresponding artifact-corrupted pixel. This replacement only occurs if the minimum value in a particular pixel’s gamma map is larger than a threshold. The proposed method was evaluated with clinical images. Results: Highly attenuating dental fillings and hip implants cause severe streaking artifacts on CT images. The proposed method eliminates the dark and bright streaking and improves the implant delineation and visibility. In particular, the image non-uniformity in the central region of interest was reduced from 1.88 and 1.01 to 0.28 and 0.35, respectively. Further, the mean CT HU error was reduced from 328 HU and 460 HU to 60 HU and 36 HU, respectively. Conclusions: The proposed metal artifact reduction method replaces corrupted image pixels with pixels from neighboring slices that are free of metal artifacts. This method proved capable of suppressing streaking artifacts, improving HU accuracy and image detectability.

  18. SU-C-206-03: Metal Artifact Reduction in X-Ray Computed Tomography Based On Local Anatomical Similarity

    Energy Technology Data Exchange (ETDEWEB)

    Dong, X; Yang, X; Rosenfield, J; Elder, E; Dhabaan, A [Emory University, Winship Cancer Institute, Atlanta, GA (United States)

    2016-06-15

    Purpose: Metal implants such as orthopedic hardware and dental fillings cause severe bright and dark streaking in reconstructed CT images. These artifacts decrease image contrast and degrade HU accuracy, leading to inaccuracies in target delineation and dose calculation. Additionally, such artifacts negatively impact patient set-up in image guided radiation therapy (IGRT). In this work, we propose a novel method for metal artifact reduction which utilizes the anatomical similarity between neighboring CT slices. Methods: Neighboring CT slices show similar anatomy. Based on this anatomical similarity, the proposed method replaces corrupted CT pixels with pixels from adjacent, artifact-free slices. A gamma map, which is the weighted summation of relative HU error and distance error, is calculated for each pixel in the artifact-corrupted CT image. The minimum value in each pixel’s gamma map is used to identify a pixel from the adjacent CT slice to replace the corresponding artifact-corrupted pixel. This replacement only occurs if the minimum value in a particular pixel’s gamma map is larger than a threshold. The proposed method was evaluated with clinical images. Results: Highly attenuating dental fillings and hip implants cause severe streaking artifacts on CT images. The proposed method eliminates the dark and bright streaking and improves the implant delineation and visibility. In particular, the image non-uniformity in the central region of interest was reduced from 1.88 and 1.01 to 0.28 and 0.35, respectively. Further, the mean CT HU error was reduced from 328 HU and 460 HU to 60 HU and 36 HU, respectively. Conclusions: The proposed metal artifact reduction method replaces corrupted image pixels with pixels from neighboring slices that are free of metal artifacts. This method proved capable of suppressing streaking artifacts, improving HU accuracy and image detectability.

  19. Clinical evaluation of a commercial orthopedic metal artifact reduction tool for CT simulations in radiation therapy

    Energy Technology Data Exchange (ETDEWEB)

    Li Hua; Noel, Camille; Chen, Haijian; Harold Li, H.; Low, Daniel; Moore, Kevin; Klahr, Paul; Michalski, Jeff; Gay, Hiram A.; Thorstad, Wade; Mutic, Sasa [Department of Radiation Oncology, Washington University, St. Louis, Missouri 63110 (United States); Department of Radiation Oncology, University of California Los Angeles, Los Angeles, California 90095 (United States); Department of Radiation Oncology, University of California San Diego, San Diego, California 92093 (United States); Philips Healthcare System, Cleveland, Ohio 44143 (United States); Department of Radiation Oncology, Washington University, St. Louis, Missouri 63110 (United States)

    2012-12-15

    Purpose: Severe artifacts in kilovoltage-CT simulation images caused by large metallic implants can significantly degrade the conspicuity and apparent CT Hounsfield number of targets and anatomic structures, jeopardize the confidence of anatomical segmentation, and introduce inaccuracies into the radiation therapy treatment planning process. This study evaluated the performance of the first commercial orthopedic metal artifact reduction function (O-MAR) for radiation therapy, and investigated its clinical applications in treatment planning. Methods: Both phantom and clinical data were used for the evaluation. The CIRS electron density phantom with known physical (and electron) density plugs and removable titanium implants was scanned on a Philips Brilliance Big Bore 16-slice CT simulator. The CT Hounsfield numbers of density plugs on both uncorrected and O-MAR corrected images were compared. Treatment planning accuracy was evaluated by comparing simulated dose distributions computed using the true density images, uncorrected images, and O-MAR corrected images. Ten CT image sets of patients with large hip implants were processed with the O-MAR function and evaluated by two radiation oncologists using a five-point score for overall image quality, anatomical conspicuity, and CT Hounsfield number accuracy. By utilizing the same structure contours delineated from the O-MAR corrected images, clinical IMRT treatment plans for five patients were computed on the uncorrected and O-MAR corrected images, respectively, and compared. Results: Results of the phantom study indicated that CT Hounsfield number accuracy and noise were improved on the O-MAR corrected images, especially for images with bilateral metal implants. The {gamma} pass rates of the simulated dose distributions computed on the uncorrected and O-MAR corrected images referenced to those of the true densities were higher than 99.9% (even when using 1% and 3 mm distance-to-agreement criterion), suggesting that dose

  20. Reduction of metal artifact in three-dimensional computed tomography (3D CT) with dental impression materials.

    Science.gov (United States)

    Park, W S; Kim, K D; Shin, H K; Lee, S H

    2007-01-01

    Metal Artifact still remains one of the main drawbacks in craniofacial Three-Dimensional Computed Tomography (3D CT). In this study, we tried to test the efficacy of additional silicone dental impression materials as a "tooth shield" for the reduction of metal artifact caused by metal restorations and orthodontic appliances. 6 phantoms with 4 teeth were prepared for this in vitro study. Orthodontic bracket, bands and amalgam restorations were placed in each tooth to reproduce various intraoral conditions. Standardized silicone shields were fabricated and placed around the teeth. CT image acquisition was performed with and without silicone shields. Maximum value, mean, and standard deviation of Hounsfield Units (HU) were compared with the presence of silicone shields. In every situation, metal artifacts were reduced in quality and quantity when silicone shields are used. Amalgam restoration made most serious metal artifact. Silicone shields made by dental impression material might be effective way to reduce the metal artifact caused by dental restoration and orthodontic appliances. This will help more excellent 3D image from 3D CT in craniofacial area.

  1. 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

  2. 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

  3. View-Angle Tilting and Slice-Encoding Metal Artifact Correction for Artifact Reduction in MRI: Experimental Sequence Optimization for Orthopaedic Tumor Endoprostheses and Clinical Application.

    Directory of Open Access Journals (Sweden)

    Pia M Jungmann

    Full Text Available MRI plays a major role in follow-up of patients with malignant bone tumors. However, after limb salvage surgery, orthopaedic tumor endoprostheses might cause significant metal-induced susceptibility artifacts.To evaluate the benefit of view-angle tilting (VAT and slice-encoding metal artifact correction (SEMAC for MRI of large-sized orthopaedic tumor endoprostheses in an experimental model and to demonstrate clinical benefits for assessment of periprosthetic soft tissue abnormalities.In an experimental setting, tumor endoprostheses (n=4 were scanned at 1.5T with three versions of optimized high-bandwidth turbo-spin-echo pulse sequences: (i standard, (ii VAT and (iii combined VAT and SEMAC (VAT&SEMAC. Pulse sequences included coronal short-tau-inversion-recovery (STIR, coronal T1-weighted (w, transverse T1-w and T2-w TSE sequences. For clinical evaluation, VAT&SEMAC was compared to conventional metal artifact-reducing MR sequences (conventional MR in n=25 patients with metal implants and clinical suspicion of tumor recurrence or infection. Diameters of artifacts were measured quantitatively. Qualitative parameters were assessed on a five-point scale (1=best, 5=worst: "image distortion", "artificial signal changes at the edges" and "diagnostic confidence". Imaging findings were correlated with pathology. T-tests and Wilcoxon-signed rank tests were used for statistical analyses.The true size of the prostheses was overestimated on MRI (P<0.05. A significant reduction of artifacts was achieved by VAT (P<0.001 and VAT&SEMAC (P=0.003 compared to the standard group. Quantitative scores improved in the VAT and VAT&SEMAC group (P<0.05. On clinical MR images, artifact diameters were significantly reduced in the VAT&SEMAC-group as compared with the conventional-group (P<0.001. Distortion and artificial signal changes were reduced and diagnostic confidence improved (P<0.05. In two cases, tumor-recurrence, in ten cases infection and in thirteen cases other

  4. Metal artifact reduction using a patch-based reconstruction for digital breast tomosynthesis

    Science.gov (United States)

    Borges, Lucas R.; Bakic, Predrag R.; Maidment, Andrew D. A.; Vieira, Marcelo A. C.

    2017-03-01

    Digital breast tomosynthesis (DBT) is rapidly emerging as the main clinical tool for breast cancer screening. Although several reconstruction methods for DBT are described by the literature, one common issue is the interplane artifacts caused by out-of-focus features. For breasts containing highly attenuating features, such as surgical clips and large calcifications, the artifacts are even more apparent and can limit the detection and characterization of lesions by the radiologist. In this work, we propose a novel method of combining backprojected data into tomographic slices using a patch-based approach, commonly used in denoising. Preliminary tests were performed on a geometry phantom and on an anthropomorphic phantom containing metal inserts. The reconstructed images were compared to a commercial reconstruction solution. Qualitative assessment of the reconstructed images provides evidence that the proposed method reduces artifacts while maintaining low noise levels. Objective assessment supports the visual findings. The artifact spread function shows that the proposed method is capable of suppressing artifacts generated by highly attenuating features. The signal difference to noise ratio shows that the noise levels of the proposed and commercial methods are comparable, even though the commercial method applies post-processing filtering steps, which were not implemented on the proposed method. Thus, the proposed method can produce tomosynthesis reconstructions with reduced artifacts and low noise levels.

  5. A fully 3D approach for metal artifact reduction in computed tomography

    International Nuclear Information System (INIS)

    Kratz, Bärbel; Weyers, Imke; Buzug, Thorsten M.

    2012-01-01

    Purpose: In computed tomography imaging metal objects in the region of interest introduce inconsistencies during data acquisition. Reconstructing these data leads to an image in spatial domain including star-shaped or stripe-like artifacts. In order to enhance the quality of the resulting image the influence of the metal objects can be reduced. Here, a metal artifact reduction (MAR) approach is proposed that is based on a recomputation of the inconsistent projection data using a fully three-dimensional Fourier-based interpolation. The success of the projection space restoration depends sensitively on a sensible continuation of neighboring structures into the recomputed area. Fortunately, structural information of the entire data is inherently included in the Fourier space of the data. This can be used for a reasonable recomputation of the inconsistent projection data. Methods: The key step of the proposed MAR strategy is the recomputation of the inconsistent projection data based on an interpolation using nonequispaced fast Fourier transforms (NFFT). The NFFT interpolation can be applied in arbitrary dimension. The approach overcomes the problem of adequate neighborhood definitions on irregular grids, since this is inherently given through the usage of higher dimensional Fourier transforms. Here, applications up to the third interpolation dimension are presented and validated. Furthermore, prior knowledge may be included by an appropriate damping of the transform during the interpolation step. This MAR method is applicable on each angular view of a detector row, on two-dimensional projection data as well as on three-dimensional projection data, e.g., a set of sequential acquisitions at different spatial positions, projection data of a spiral acquisition, or cone-beam projection data. Results: Results of the novel MAR scheme based on one-, two-, and three-dimensional NFFT interpolations are presented. All results are compared in projection data space and spatial

  6. Changes realized from extended bit-depth and metal artifact reduction in CT

    Energy Technology Data Exchange (ETDEWEB)

    Glide-Hurst, C.; Chen, D.; Zhong, H.; Chetty, I. J. [Department of Radiation Oncology, Henry Ford Health Systems, Detroit, Michigan 48202 (United States)

    2013-06-15

    Purpose: High-Z material in computed tomography (CT) yields metal artifacts that degrade image quality and may cause substantial errors in dose calculation. This study couples a metal artifact reduction (MAR) algorithm with enhanced 16-bit depth (vs standard 12-bit) to quantify potential gains in image quality and dosimetry. Methods: Extended CT to electron density (CT-ED) curves were derived from a tissue characterization phantom with titanium and stainless steel inserts scanned at 90-140 kVp for 12- and 16-bit reconstructions. MAR was applied to sinogram data (Brilliance BigBore CT scanner, Philips Healthcare, v.3.5). Monte Carlo simulation (MC-SIM) was performed on a simulated double hip prostheses case (Cerrobend rods embedded in a pelvic phantom) using BEAMnrc/Dosxyz (400 000 0000 histories, 6X, 10 Multiplication-Sign 10 cm{sup 2} beam traversing Cerrobend rod). A phantom study was also conducted using a stainless steel rod embedded in solid water, and dosimetric verification was performed with Gafchromic film analysis (absolute difference and gamma analysis, 2% dose and 2 mm distance to agreement) for plans calculated with Anisotropic Analytic Algorithm (AAA, Eclipse v11.0) to elucidate changes between 12- and 16-bit data. Three patients (bony metastases to the femur and humerus, and a prostate cancer case) with metal implants were reconstructed using both bit depths, with dose calculated using AAA and derived CT-ED curves. Planar dose distributions were assessed via matrix analyses and using gamma criteria of 2%/2 mm. Results: For 12-bit images, CT numbers for titanium and stainless steel saturated at 3071 Hounsfield units (HU), whereas for 16-bit depth, mean CT numbers were much larger (e.g., titanium and stainless steel yielded HU of 8066.5 {+-} 56.6 and 13 588.5 {+-} 198.8 for 16-bit uncorrected scans at 120 kVp, respectively). MC-SIM was well-matched between 12- and 16-bit images except downstream of the Cerrobend rod, where 16-bit dose was {approx}6

  7. Contouring and dose calculation in head and neck cancer radiotherapy after reduction of metal artifacts in CT images

    DEFF Research Database (Denmark)

    Hansen, Christian Rønn; Lübeck Christiansen, Rasmus; Lorenzen, Ebbe Laugaard

    2017-01-01

    of metal artifact reduction (MAR) in H&N patients in terms of delineation consistency and dose calculation precision in radiation treatment planning. Material and methods: Tumor and OAR delineations were evaluated in planning CT scans of eleven oropharynx patients with streaking artifacts in the tumor...... region preceding curative radiotherapy (RT). The GTV-tumor (GTV-T), GTV-node and parotid glands were contoured by four independent observers on standard CT images and MAR images. Dose calculation was evaluated on thirty H&N patients with dental implants near the treated volume. For each patient, the dose...

  8. SU-E-T-329: Dosimetric Impact of Implementing Metal Artifact Reduction Methods and Metal Energy Deposition Kernels for Photon Dose Calculations

    International Nuclear Information System (INIS)

    Huang, J; Followill, D; Howell, R; Liu, X; Mirkovic, D; Stingo, F; Kry, S

    2015-01-01

    Purpose: To investigate two strategies for reducing dose calculation errors near metal implants: use of CT metal artifact reduction methods and implementation of metal-based energy deposition kernels in the convolution/superposition (C/S) method. Methods: Radiochromic film was used to measure the dose upstream and downstream of titanium and Cerrobend implants. To assess the dosimetric impact of metal artifact reduction methods, dose calculations were performed using baseline, uncorrected images and metal artifact reduction Methods: Philips O-MAR, GE’s monochromatic gemstone spectral imaging (GSI) using dual-energy CT, and GSI imaging with metal artifact reduction software applied (MARs).To assess the impact of metal kernels, titanium and silver kernels were implemented into a commercial collapsed cone C/S algorithm. Results: The CT artifact reduction methods were more successful for titanium than Cerrobend. Interestingly, for beams traversing the metal implant, we found that errors in the dimensions of the metal in the CT images were more important for dose calculation accuracy than reduction of imaging artifacts. The MARs algorithm caused a distortion in the shape of the titanium implant that substantially worsened the calculation accuracy. In comparison to water kernel dose calculations, metal kernels resulted in better modeling of the increased backscatter dose at the upstream interface but decreased accuracy directly downstream of the metal. We also found that the success of metal kernels was dependent on dose grid size, with smaller calculation voxels giving better accuracy. Conclusion: Our study yielded mixed results, with neither the metal artifact reduction methods nor the metal kernels being globally effective at improving dose calculation accuracy. However, some successes were observed. The MARs algorithm decreased errors downstream of Cerrobend by a factor of two, and metal kernels resulted in more accurate backscatter dose upstream of metals. Thus

  9. High-Resolution C-Arm CT and Metal Artifact Reduction Software: A Novel Imaging Modality for Analyzing Aneurysms Treated with Stent-Assisted Coil Embolization.

    Science.gov (United States)

    Yuki, I; Kambayashi, Y; Ikemura, A; Abe, Y; Kan, I; Mohamed, A; Dahmani, C; Suzuki, T; Ishibashi, T; Takao, H; Urashima, M; Murayama, Y

    2016-02-01

    Combination of high-resolution C-arm CT and novel metal artifact reduction software may contribute to the assessment of aneurysms treated with stent-assisted coil embolization. This study aimed to evaluate the efficacy of a novel Metal Artifact Reduction prototype software combined with the currently available high spatial-resolution C-arm CT prototype implementation by using an experimental aneurysm model treated with stent-assisted coil embolization. Eight experimental aneurysms were created in 6 swine. Coil embolization of each aneurysm was performed by using a stent-assisted technique. High-resolution C-arm CT with intra-arterial contrast injection was performed immediately after the treatment. The obtained images were processed with Metal Artifact Reduction. Five neurointerventional specialists reviewed the image quality before and after Metal Artifact Reduction. Observational and quantitative analyses (via image analysis software) were performed. Every aneurysm was successfully created and treated with stent-assisted coil embolization. Before Metal Artifact Reduction, coil loops protruding through the stent lumen were not visualized due to the prominent metal artifacts produced by the coils. These became visible after Metal Artifact Reduction processing. Contrast filling in the residual aneurysm was also visualized after Metal Artifact Reduction in every aneurysm. Both the observational (P software. The combination of high-resolution C-arm CT and Metal Artifact Reduction enables differentiation of the coil mass, stent, and contrast material on the same image by significantly reducing the metal artifacts produced by the platinum coils. This novel image technique may improve the assessment of aneurysms treated with stent-assisted coil embolization. © 2016 by American Journal of Neuroradiology.

  10. Usefulness of metal artifact reduction with WARP technique at 1.5 and 3T MRI in imaging metal-on-metal hip resurfacings

    Energy Technology Data Exchange (ETDEWEB)

    Lazik, Andrea; Lauenstein, Thomas C.; Theysohn, Jens M. [University Hospital Essen, Department of Diagnostic and Interventional Radiology and Neuroradiology, Essen (Germany); Landgraeber, Stefan; Schulte, Patrick [University Hospital Essen, Department of Orthopedics, Essen (Germany); Kraff, Oliver [University of Duisburg-Essen, Erwin L. Hahn Institute for Magnetic Resonance Imaging, Essen (Germany)

    2015-03-25

    To evaluate the usefulness of the metal artifact reduction technique ''WARP'' in the assessment of metal-on-metal hip resurfacings at 1.5 and 3T in the context of image quality and imaging speed. Nineteen patients (25 hip resurfacings) were randomized for 1.5 and 3T MRI, both including T1 and T2 turbo spin-echo as well as turbo inversion recovery magnitude sequences with and without view angle tilting and high bandwidth. Additional 3T sequences were acquired with a reduced number of averages and using the parallel acquisition technique for accelerating imaging speed. Artifact size (diameter, area), image quality (5-point scale) and delineation of anatomical structures were compared among the techniques, sequences and field strengths using the Wilcoxon sign-rank and paired t-test with Bonferroni correction. At both field strengths, WARP showed significant superiority over standard sequences regarding image quality, artifact size and delineation of anatomical structures. At 3T, artifacts were larger compared to 1.5T without affecting diagnostic quality, and scanning time could be reduced by up to 64 % without quality degradation. WARP proved useful in imaging metal-on-metal hip resurfacings at 1.5T as well as 3T with better image quality surrounding the implants. At 3T imaging could be considerably accelerated without losing diagnostic quality. (orig.)

  11. Usefulness of metal artifact reduction with WARP technique at 1.5 and 3T MRI in imaging metal-on-metal hip resurfacings

    International Nuclear Information System (INIS)

    Lazik, Andrea; Lauenstein, Thomas C.; Theysohn, Jens M.; Landgraeber, Stefan; Schulte, Patrick; Kraff, Oliver

    2015-01-01

    To evaluate the usefulness of the metal artifact reduction technique ''WARP'' in the assessment of metal-on-metal hip resurfacings at 1.5 and 3T in the context of image quality and imaging speed. Nineteen patients (25 hip resurfacings) were randomized for 1.5 and 3T MRI, both including T1 and T2 turbo spin-echo as well as turbo inversion recovery magnitude sequences with and without view angle tilting and high bandwidth. Additional 3T sequences were acquired with a reduced number of averages and using the parallel acquisition technique for accelerating imaging speed. Artifact size (diameter, area), image quality (5-point scale) and delineation of anatomical structures were compared among the techniques, sequences and field strengths using the Wilcoxon sign-rank and paired t-test with Bonferroni correction. At both field strengths, WARP showed significant superiority over standard sequences regarding image quality, artifact size and delineation of anatomical structures. At 3T, artifacts were larger compared to 1.5T without affecting diagnostic quality, and scanning time could be reduced by up to 64 % without quality degradation. WARP proved useful in imaging metal-on-metal hip resurfacings at 1.5T as well as 3T with better image quality surrounding the implants. At 3T imaging could be considerably accelerated without losing diagnostic quality. (orig.)

  12. The application of metal artifact reduction (MAR) in CT scans for radiation oncology by monoenergetic extrapolation with a DECT scanner

    Energy Technology Data Exchange (ETDEWEB)

    Schwahofer, Andrea [German Cancer Research Center, Heidelberg (Germany). Dept. of Medical Physics in Radiation Oncology; Clinical Center Vivantes, Neukoelln (Germany). Dept. of Radiotherapy and Oncology; Baer, Esther [German Cancer Research Center, Heidelberg (Germany). Dept. of Medical Physics in Radiation Oncology; Kuchenbecker, Stefan; Kachelriess, Marc [German Cancer Research Center, Heidelberg (Germany). Dept. of Medical Physics in Radiology; Grossmann, J. Guenter [German Cancer Research Center, Heidelberg (Germany). Dept. of Medical Physics in Radiation Oncology; Ortenau Klinikum Offenburg-Gengenbach (Germany). Dept. of Radiooncology; Sterzing, Florian [Heidelberg Univ. (Germany). Dept. of Radiation Oncology; German Cancer Research Center, Heidelberg (Germany). Dept. of Radiotherapy

    2015-07-01

    Metal artifacts in computed tomography CT images are one of the main problems in radiation oncology as they introduce uncertainties to target and organ at risk delineation as well as dose calculation. This study is devoted to metal artifact reduction (MAR) based on the monoenergetic extrapolation of a dual energy CT (DECT) dataset. In a phantom study the CT artifacts caused by metals with different densities: aluminum (ρ{sub Al} = 2.7 g/cm{sup 3}), titanium (ρ{sub Ti} = 4.5 g/cm{sup 3}), steel (ρ{sub steel} = 7.9 g/cm{sup 3}) and tungsten (ρ{sub W} = 19.3 g/cm{sup 3}) have been investigated. Data were collected using a clinical dual source dual energy CT (DECT) scanner (Siemens Sector Healthcare, Forchheim, Germany) with tube voltages of 100 kV and 140 kV (Sn). For each tube voltage the data set in a given volume was reconstructed. Based on these two data sets a voxel by voxel linear combination was performed to obtain the monoenergetic data sets. The results were evaluated regarding the optical properties of the images as well as the CT values (HU) and the dosimetric consequences in computed treatment plans. A data set without metal substitute served as the reference. Also, a head and neck patient with dental fillings (amalgam ρ = 10 g/cm{sup 3}) was scanned with a single energy CT (SECT) protocol and a DECT protocol. The monoenergetic extrapolation was performed as described above and evaluated in the same way. Visual assessment of all data shows minor reductions of artifacts in the images with aluminum and titanium at a monoenergy of 105 keV. As expected, the higher the densities the more distinctive are the artifacts. For metals with higher densities such as steel or tungsten, no artifact reduction has been achieved. Likewise in the CT values, no improvement by use of the monoenergetic extrapolation can be detected. The dose was evaluated at a point 7 cm behind the isocenter of a static field. Small improvements (around 1%) can be seen with 105 ke

  13. The application of metal artifact reduction (MAR) in CT scans for radiation oncology by monoenergetic extrapolation with a DECT scanner

    International Nuclear Information System (INIS)

    Schwahofer, Andrea; Clinical Center Vivantes, Neukoelln; Baer, Esther; Kuchenbecker, Stefan; Kachelriess, Marc; Grossmann, J. Guenter; Ortenau Klinikum Offenburg-Gengenbach; Sterzing, Florian; German Cancer Research Center, Heidelberg

    2015-01-01

    Metal artifacts in computed tomography CT images are one of the main problems in radiation oncology as they introduce uncertainties to target and organ at risk delineation as well as dose calculation. This study is devoted to metal artifact reduction (MAR) based on the monoenergetic extrapolation of a dual energy CT (DECT) dataset. In a phantom study the CT artifacts caused by metals with different densities: aluminum (ρ Al = 2.7 g/cm 3 ), titanium (ρ Ti = 4.5 g/cm 3 ), steel (ρ steel = 7.9 g/cm 3 ) and tungsten (ρ W = 19.3 g/cm 3 ) have been investigated. Data were collected using a clinical dual source dual energy CT (DECT) scanner (Siemens Sector Healthcare, Forchheim, Germany) with tube voltages of 100 kV and 140 kV (Sn). For each tube voltage the data set in a given volume was reconstructed. Based on these two data sets a voxel by voxel linear combination was performed to obtain the monoenergetic data sets. The results were evaluated regarding the optical properties of the images as well as the CT values (HU) and the dosimetric consequences in computed treatment plans. A data set without metal substitute served as the reference. Also, a head and neck patient with dental fillings (amalgam ρ = 10 g/cm 3 ) was scanned with a single energy CT (SECT) protocol and a DECT protocol. The monoenergetic extrapolation was performed as described above and evaluated in the same way. Visual assessment of all data shows minor reductions of artifacts in the images with aluminum and titanium at a monoenergy of 105 keV. As expected, the higher the densities the more distinctive are the artifacts. For metals with higher densities such as steel or tungsten, no artifact reduction has been achieved. Likewise in the CT values, no improvement by use of the monoenergetic extrapolation can be detected. The dose was evaluated at a point 7 cm behind the isocenter of a static field. Small improvements (around 1%) can be seen with 105 keV. However, the dose uncertainty remains of the

  14. Advanced metal artifact reduction MRI of metal-on-metal hip resurfacing arthroplasty implants: compressed sensing acceleration enables the time-neutral use of SEMAC

    International Nuclear Information System (INIS)

    Fritz, Jan; Thawait, Gaurav K.; Fritz, Benjamin; Raithel, Esther; Nittka, Mathias; Gilson, Wesley D.; Mont, Michael A.

    2016-01-01

    Compressed sensing (CS) acceleration has been theorized for slice encoding for metal artifact correction (SEMAC), but has not been shown to be feasible. Therefore, we tested the hypothesis that CS-SEMAC is feasible for MRI of metal-on-metal hip resurfacing implants. Following prospective institutional review board approval, 22 subjects with metal-on-metal hip resurfacing implants underwent 1.5 T MRI. We compared CS-SEMAC prototype, high-bandwidth TSE, and SEMAC sequences with acquisition times of 4-5, 4-5 and 10-12 min, respectively. Outcome measures included bone-implant interfaces, image quality, periprosthetic structures, artifact size, and signal- and contrast-to-noise ratios (SNR and CNR). Using Friedman, repeated measures analysis of variances, and Cohen's weighted kappa tests, Bonferroni-corrected p-values of 0.005 and less were considered statistically significant. There was no statistical difference of outcomes measures of SEMAC and CS-SEMAC images. Visibility of implant-bone interfaces and pseudocapsule as well as fat suppression and metal reduction were ''adequate'' to ''good'' on CS-SEMAC and ''non-diagnostic'' to ''adequate'' on high-BW TSE (p < 0.001, respectively). SEMAC and CS-SEMAC showed mild blur and ripple artifacts. The metal artifact size was 63 % larger for high-BW TSE as compared to SEMAC and CS-SEMAC (p < 0.0001, respectively). CNRs were sufficiently high and statistically similar, with the exception of CNR of fluid and muscle and CNR of fluid and tendon, which were higher on intermediate-weighted high-BW TSE (p < 0.005, respectively). Compressed sensing acceleration enables the time-neutral use of SEMAC for MRI of metal-on-metal hip resurfacing implants when compared to high-BW TSE and image quality similar to conventional SEMAC. (orig.)

  15. Advanced metal artifact reduction MRI of metal-on-metal hip resurfacing arthroplasty implants: compressed sensing acceleration enables the time-neutral use of SEMAC

    Energy Technology Data Exchange (ETDEWEB)

    Fritz, Jan; Thawait, Gaurav K. [Johns Hopkins University School of Medicine, Russell H. Morgan Department of Radiology and Radiological Science, Section of Musculoskeletal Radiology, Baltimore, MD (United States); Fritz, Benjamin [University of Freiburg, Department of Radiology, Freiburg im Breisgau (Germany); Raithel, Esther; Nittka, Mathias [Siemens Healthcare GmbH, Erlangen (Germany); Gilson, Wesley D. [Siemens Healthcare USA, Inc., Baltimore, MD (United States); Mont, Michael A. [Cleveland Clinic Foundation, Department of Orthopedic Surgery, Cleveland, OH (United States)

    2016-10-15

    Compressed sensing (CS) acceleration has been theorized for slice encoding for metal artifact correction (SEMAC), but has not been shown to be feasible. Therefore, we tested the hypothesis that CS-SEMAC is feasible for MRI of metal-on-metal hip resurfacing implants. Following prospective institutional review board approval, 22 subjects with metal-on-metal hip resurfacing implants underwent 1.5 T MRI. We compared CS-SEMAC prototype, high-bandwidth TSE, and SEMAC sequences with acquisition times of 4-5, 4-5 and 10-12 min, respectively. Outcome measures included bone-implant interfaces, image quality, periprosthetic structures, artifact size, and signal- and contrast-to-noise ratios (SNR and CNR). Using Friedman, repeated measures analysis of variances, and Cohen's weighted kappa tests, Bonferroni-corrected p-values of 0.005 and less were considered statistically significant. There was no statistical difference of outcomes measures of SEMAC and CS-SEMAC images. Visibility of implant-bone interfaces and pseudocapsule as well as fat suppression and metal reduction were ''adequate'' to ''good'' on CS-SEMAC and ''non-diagnostic'' to ''adequate'' on high-BW TSE (p < 0.001, respectively). SEMAC and CS-SEMAC showed mild blur and ripple artifacts. The metal artifact size was 63 % larger for high-BW TSE as compared to SEMAC and CS-SEMAC (p < 0.0001, respectively). CNRs were sufficiently high and statistically similar, with the exception of CNR of fluid and muscle and CNR of fluid and tendon, which were higher on intermediate-weighted high-BW TSE (p < 0.005, respectively). Compressed sensing acceleration enables the time-neutral use of SEMAC for MRI of metal-on-metal hip resurfacing implants when compared to high-BW TSE and image quality similar to conventional SEMAC. (orig.)

  16. Spectral CT with metal artifacts reduction software for improvement of tumor visibility in the vicinity of gold fiducial markers.

    Science.gov (United States)

    Brook, Olga R; Gourtsoyianni, Sofia; Brook, Alexander; Mahadevan, Anand; Wilcox, Carol; Raptopoulos, Vassilios

    2012-06-01

    To evaluate spectral computed tomography (CT) with metal artifacts reduction software (MARS) for reduction of metal artifacts associated with gold fiducial seeds. Thirteen consecutive patients with 37 fiducial seeds implanted for radiation therapy of abdominal lesions were included in this HIPAA-compliant, institutional review board-approved prospective study. Six patients were women (46%) and seven were men (54%). The mean age was 61.1 years (median, 58 years; range, 29-78 years). Spectral imaging was used for arterial phase CT. Images were reconstructed with and without MARS in axial, coronal, and sagittal planes. Two radiologists independently reviewed reconstructions and selected the best image, graded the visibility of the tumor, and assessed the amount of artifacts in all planes. A linear-weighted κ statistic and Wilcoxon signed-rank test were used to assess interobserver variability. Histogram analysis with the Kolmogorov-Smirnov test was used for objective evaluation of artifacts reduction. Fiducial seeds were placed in pancreas (n = 5), liver (n = 7), periportal lymph nodes (n = 1), and gallbladder bed (n = 1). MARS-reconstructed images received a better grade than those with standard reconstruction in 60% and 65% of patients by the first and second radiologist, respectively. Tumor visibility was graded higher with standard versus MARS reconstruction (grade, 3.7 ± 1.0 vs 2.8 ± 1.1; P = .001). Reduction of blooming was noted on MARS-reconstructed images (P = .01). Amount of artifacts, for both any and near field, was significantly smaller on sagittal and coronal MARS-reconstructed images than on standard reconstructions (P MARS-reconstructed images than on standard reconstructions (P MARS than with standard reconstruction in 35 of 37 patients (P MARS improved tumor visibility in the vicinity of gold fiducial seeds.

  17. High-resolution metal artifact reduction MR imaging of the lumbosacral plexus in patients with metallic implants.

    Science.gov (United States)

    Ahlawat, Shivani; Stern, Steven E; Belzberg, Allan J; Fritz, Jan

    2017-07-01

    To assess the quality and accuracy of metal artifact reduction sequence (MARS) magnetic resonance imaging (MRI) for the diagnosis of lumbosacral neuropathies in patients with metallic implants in the pelvis. Twenty-two subjects with lumbosacral neuropathy following pelvic instrumentation underwent 1.5-T MARS MRI including optimized axial intermediate-weighted and STIR turbo spin echo sequences extending from L5 to the ischial tuberosity. Two readers graded the visibility of the lumbosacral trunk, sciatic, femoral, lateral femoral cutaneous, and obturator nerves and the nerve signal intensity of nerve, architecture, caliber, course, continuity, and skeletal muscle denervation. Clinical examination and electrodiagnostic studies were used as the standard of reference. Descriptive, agreement, and diagnostic performance statistics were applied. Lumbosacral plexus visibility on MARS MRI was good (4) or very good (3) in 92% of cases with 81% exact agreement and a Kendall's W coefficient of 0.811. The obturator nerve at the obturator foramen and the sciatic nerve posterior to the acetabulum had the lowest visibility, with good or very good ratings in only 61% and 77% of cases respectively. The reader agreement for nerve abnormalities on MARS MRI was excellent, ranging from 95.5 to 100%. MARS MRI achieved a sensitivity of 86%, specificity of 67%, positive predictive value of 95%, and negative predictive value of 40%, and accuracy of 83% for the detection of neuropathy. MARS MRI yields high image quality and diagnostic accuracy for the assessment of lumbosacral neuropathies in patients with metallic implants of the pelvis and hips.

  18. Follow-up CT and CT angiography after intracranial aneurysm clipping and coiling - improved image quality by iterative metal artifact reduction

    Energy Technology Data Exchange (ETDEWEB)

    Bier, Georg; Hempel, Johann-Martin; Oergel, Anja; Hauser, Till-Karsten; Ernemann, Ulrike; Hennersdorf, Florian [Eberhard Karls University Tuebingen, Department of Diagnostic and Interventional Neuroradiology, Tuebingen (Germany); Bongers, Malte Niklas [Eberhard Karls University Tuebingen, Department of Diagnostic and Interventional Radiology, Tuebingen (Germany)

    2017-07-15

    This paper aims to evaluate a new iterative metal artifact reduction algorithm for post-interventional evaluation of brain tissue and intracranial arteries. The data of 20 patients that underwent follow-up cranial CT and cranial CT angiography after clipping or coiling of an intracranial aneurysm was retrospectively analyzed. After the images were processed using a novel iterative metal artifact reduction algorithm, images with and without metal artifact reduction were qualitatively evaluated by two readers, using a five-point Likert scale. Moreover, artifact strength was quantitatively assessed in terms of CT attenuation and standard deviation alterations. The qualitative analysis yielded a significant increase in image quality (p = 0.0057) in iteratively processed images with substantial inter-observer agreement (k = 0.72), while the CTA image quality did not differ (p = 0.864) and even showed vessel contrast reduction in six cases (30%). The mean relative attenuation difference was 27% without metal artifact reduction vs. 11% for iterative metal artifact reduction images (p = 0.0003). The new iterative metal artifact reduction algorithm enhances non-enhanced CT image quality after clipping or coiling, but in CT-angiography images, the contrast of adjacent vessels can be compromised. (orig.)

  19. Follow-up CT and CT angiography after intracranial aneurysm clipping and coiling - improved image quality by iterative metal artifact reduction

    International Nuclear Information System (INIS)

    Bier, Georg; Hempel, Johann-Martin; Oergel, Anja; Hauser, Till-Karsten; Ernemann, Ulrike; Hennersdorf, Florian; Bongers, Malte Niklas

    2017-01-01

    This paper aims to evaluate a new iterative metal artifact reduction algorithm for post-interventional evaluation of brain tissue and intracranial arteries. The data of 20 patients that underwent follow-up cranial CT and cranial CT angiography after clipping or coiling of an intracranial aneurysm was retrospectively analyzed. After the images were processed using a novel iterative metal artifact reduction algorithm, images with and without metal artifact reduction were qualitatively evaluated by two readers, using a five-point Likert scale. Moreover, artifact strength was quantitatively assessed in terms of CT attenuation and standard deviation alterations. The qualitative analysis yielded a significant increase in image quality (p = 0.0057) in iteratively processed images with substantial inter-observer agreement (k = 0.72), while the CTA image quality did not differ (p = 0.864) and even showed vessel contrast reduction in six cases (30%). The mean relative attenuation difference was 27% without metal artifact reduction vs. 11% for iterative metal artifact reduction images (p = 0.0003). The new iterative metal artifact reduction algorithm enhances non-enhanced CT image quality after clipping or coiling, but in CT-angiography images, the contrast of adjacent vessels can be compromised. (orig.)

  20. Improving image quality for digital breast tomosynthesis: an automated detection and diffusion-based method for metal artifact reduction

    Science.gov (United States)

    Lu, Yao; Chan, Heang-Ping; Wei, Jun; Hadjiiski, Lubomir M.; Samala, Ravi K.

    2017-10-01

    In digital breast tomosynthesis (DBT), the high-attenuation metallic clips marking a previous biopsy site in the breast cause errors in the estimation of attenuation along the ray paths intersecting the markers during reconstruction, which result in interplane and inplane artifacts obscuring the visibility of subtle lesions. We proposed a new metal artifact reduction (MAR) method to improve image quality. Our method uses automatic detection and segmentation to generate a marker location map for each projection (PV). A voting technique based on the geometric correlation among different PVs is designed to reduce false positives (FPs) and to label the pixels on the PVs and the voxels in the imaged volume that represent the location and shape of the markers. An iterative diffusion method replaces the labeled pixels on the PVs with estimated tissue intensity from the neighboring regions while preserving the original pixel values in the neighboring regions. The inpainted PVs are then used for DBT reconstruction. The markers are repainted on the reconstructed DBT slices for radiologists’ information. The MAR method is independent of reconstruction techniques or acquisition geometry. For the training set, the method achieved 100% success rate with one FP in 19 views. For the test set, the success rate by view was 97.2% for core biopsy microclips and 66.7% for clusters of large post-lumpectomy markers with a total of 10 FPs in 58 views. All FPs were large dense benign calcifications that also generated artifacts if they were not corrected by MAR. For the views with successful detection, the metal artifacts were reduced to a level that was not visually apparent in the reconstructed slices. The visibility of breast lesions obscured by the reconstruction artifacts from the metallic markers was restored.

  1. Digital tomosynthesis with metal artifact reduction for assessing cementless hip arthroplasty: a diagnostic cohort study of 48 patients

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Hao; Yang, Dejin; Guo, Shengjie; Tang, Jing; Liu, Jian; Wang, Dacheng; Zhou, Yixin [Beijing Jishuitan Hospital, Fourth Clinical College of Peking University, Department of Orthopaedic Surgery, Beijing (China)

    2016-11-15

    For postoperative imaging assessment of cementless hip arthroplasty, radiography and computed tomography (CT) were restricted by overlapping structures and metal artifacts, respectively. A new tomosynthesis with metal artifact reduction (TMAR) is introduced by using metal extraction and ordered subset-expectation maximization (OS-EM) reconstruction. This study investigated the effectiveness of TMAR in assessing fixation stability of cementless hip arthroplasty components. We prospectively included 48 consecutive patients scheduled for revision hip arthroplasty in our hospital, with 41 femoral and 35 acetabular cementless components available for evaluation. All patients took the three examinations of radiography, CT, and TMAR preoperatively, with intraoperative mechanical tests, and absence or presence of osteointegration on retrieved prosthesis as reference standards. Three senior surgeons and four junior surgeons evaluated these images independently with uniform criteria. For TMAR, 82 % diagnoses on the femoral side and 84 % diagnoses on the acetabular side were accurate. The corresponding values were 44 and 67 % for radiography, and 39 % and 74 % for CT. Senior surgeons had significantly higher accuracy than junior surgeons by radiography (p < 0.05), but not by TMAR or CT. By minimizing metal artifacts in the bone-implant interface and clearly depicting peri-implant trabecular structures, the TMAR technique improved the diagnostic accuracy of assessing fixation stability of cementless hip arthroplasty, and shortened the learning curve of less experienced surgeons. Level II, diagnostic cohort study. (orig.)

  2. An adaptive approach to metal artifact reduction in helical computed tomography for radiation therapy treatment planning: Experimental and clinical studies

    International Nuclear Information System (INIS)

    Yazdia, Mehran; Gingras, Luc; Beaulieu, Luc

    2005-01-01

    Purpose: In this article, an approach to metal artifact reduction is proposed that is practical for clinical use in radiation therapy. It is based on a new interpolation scheme of the projections associated with metal implants in helical computed tomography (CT) scanners. Methods and Materials: A three-step approach was developed consisting of an automatic algorithm for metal implant detection, a correction algorithm for helical projections, and a new, efficient algorithm for projection interpolation. The modified raw projection data are transferred back to the CT scanner device where CT slices are regenerated using the built-in reconstruction operator. The algorithm was tested on a CT calibration phantom in which the density of inserted objects are known and on clinical prostate cases with two hip prostheses. The results are evaluated using the CT number and shape of the objects. Results: The validations on a CT calibration phantom with various inserts of known densities show that the algorithm improved the overall image quality by restoring the shape and the representative CT number of the objects in the image. For the clinical hip replacement cases, a large fraction of the bladder, rectum, and prostate that were not visible on the original CT slices were recovered using the algorithm. Precise contouring of the target volume was thus feasible. Without this enhancement, physicians would have drawn bigger margins to be sure to include the target and, at the same time, could have prescribed a lower dose to keep the same level of normal tissue toxicity. Conclusions: In both phantom experiment and patient studies, the algorithm resulted in significant artifact reduction with increases in the reliability of planning procedure for the case of metallic hip prostheses. This algorithm is now clinically used as a preprocessing before treatment planning for metal artifact reduction

  3. High-resolution metal artifact reduction MR imaging of the lumbosacral plexus in patients with metallic implants

    International Nuclear Information System (INIS)

    Ahlawat, Shivani; Fritz, Jan; Stern, Steven E.; Belzberg, Allan J.

    2017-01-01

    To assess the quality and accuracy of metal artifact reduction sequence (MARS) magnetic resonance imaging (MRI) for the diagnosis of lumbosacral neuropathies in patients with metallic implants in the pelvis. Twenty-two subjects with lumbosacral neuropathy following pelvic instrumentation underwent 1.5-T MARS MRI including optimized axial intermediate-weighted and STIR turbo spin echo sequences extending from L5 to the ischial tuberosity. Two readers graded the visibility of the lumbosacral trunk, sciatic, femoral, lateral femoral cutaneous, and obturator nerves and the nerve signal intensity of nerve, architecture, caliber, course, continuity, and skeletal muscle denervation. Clinical examination and electrodiagnostic studies were used as the standard of reference. Descriptive, agreement, and diagnostic performance statistics were applied. Lumbosacral plexus visibility on MARS MRI was good (4) or very good (3) in 92% of cases with 81% exact agreement and a Kendall's W coefficient of 0.811. The obturator nerve at the obturator foramen and the sciatic nerve posterior to the acetabulum had the lowest visibility, with good or very good ratings in only 61% and 77% of cases respectively. The reader agreement for nerve abnormalities on MARS MRI was excellent, ranging from 95.5 to 100%. MARS MRI achieved a sensitivity of 86%, specificity of 67%, positive predictive value of 95%, and negative predictive value of 40%, and accuracy of 83% for the detection of neuropathy. MARS MRI yields high image quality and diagnostic accuracy for the assessment of lumbosacral neuropathies in patients with metallic implants of the pelvis and hips. (orig.)

  4. High-resolution metal artifact reduction MR imaging of the lumbosacral plexus in patients with metallic implants

    Energy Technology Data Exchange (ETDEWEB)

    Ahlawat, Shivani; Fritz, Jan [The Johns Hopkins Medical Institutions, The Russell H. Morgan Department of Radiology and Radiological Science, Baltimore, MD (United States); Stern, Steven E. [Bond University, Bond Business School, Gold Coast, QLD (Australia); Belzberg, Allan J. [Johns Hopkins University School of Medicine, Department of Neurosurgery, Baltimore, MD (United States)

    2017-07-15

    To assess the quality and accuracy of metal artifact reduction sequence (MARS) magnetic resonance imaging (MRI) for the diagnosis of lumbosacral neuropathies in patients with metallic implants in the pelvis. Twenty-two subjects with lumbosacral neuropathy following pelvic instrumentation underwent 1.5-T MARS MRI including optimized axial intermediate-weighted and STIR turbo spin echo sequences extending from L5 to the ischial tuberosity. Two readers graded the visibility of the lumbosacral trunk, sciatic, femoral, lateral femoral cutaneous, and obturator nerves and the nerve signal intensity of nerve, architecture, caliber, course, continuity, and skeletal muscle denervation. Clinical examination and electrodiagnostic studies were used as the standard of reference. Descriptive, agreement, and diagnostic performance statistics were applied. Lumbosacral plexus visibility on MARS MRI was good (4) or very good (3) in 92% of cases with 81% exact agreement and a Kendall's W coefficient of 0.811. The obturator nerve at the obturator foramen and the sciatic nerve posterior to the acetabulum had the lowest visibility, with good or very good ratings in only 61% and 77% of cases respectively. The reader agreement for nerve abnormalities on MARS MRI was excellent, ranging from 95.5 to 100%. MARS MRI achieved a sensitivity of 86%, specificity of 67%, positive predictive value of 95%, and negative predictive value of 40%, and accuracy of 83% for the detection of neuropathy. MARS MRI yields high image quality and diagnostic accuracy for the assessment of lumbosacral neuropathies in patients with metallic implants of the pelvis and hips. (orig.)

  5. Exploring metal artifact reduction using dual-energy CT with pre-metal and post-metal implant cadaver comparison: are implant specific protocols needed?

    Science.gov (United States)

    Wellenberg, Ruud H H; Donders, Johanna C E; Kloen, Peter; Beenen, Ludo F M; Kleipool, Roeland P; Maas, Mario; Streekstra, Geert J

    2017-08-25

    To quantify and optimize metal artifact reduction using virtual monochromatic dual-energy CT for different metal implants compared to non-metal reference scans. Dual-energy CT scans of a pair of human cadaver limbs were acquired before and after implanting a titanium tibia plate, a stainless-steel tibia plate and a titanium intramedullary nail respectively. Virtual monochromatic images were analyzed from 70 to 190 keV. Region-of-interest (ROI), used to determine fluctuations and inaccuracies in CT numbers of soft tissues and bone, were placed in muscle, fat, cortical bone and intramedullary tibia canal. The stainless-steel implant resulted in more pronounced metal artifacts compared to both titanium implants. CT number inaccuracies in 70 keV reference images were minimized at 130, 180 and 190 keV for the titanium tibia plate, stainless-steel tibia plate and titanium intramedullary nail respectively. Noise, measured as the standard deviation of pixels within a ROI, was minimized at 130, 150 and 140 keV for the titanium tibia plate, stainless-steel tibia plate and titanium intramedullary nail respectively. Tailoring dual-energy CT protocols using implant specific virtual monochromatic images minimizes fluctuations and inaccuracies in CT numbers in bone and soft tissues compared to non-metal reference scans.

  6. Iterative Metallic Artifact Reduction for In-Plane Gonadal Shielding During Computed Tomographic Venography of Young Males.

    Science.gov (United States)

    Choi, Jin Woo; Lee, Sang Yub; Kim, Jong Hyo; Jin, Hyeongmin; Lee, Jaewon; Choi, Young Hun; Lee, Hyeon-Kyeong; Park, Jae Hyung

    The purpose of this study was to evaluate a gonadal shield (GS) and iterative metallic artifact reduction (IMAR) during computed tomography scans, regarding the image quality and radiation dose. A phantom was imaged with and without a GS. Prospectively enrolled, young male patients underwent lower extremity computed tomography venography (precontrast imaging without the GS and postcontrast imaging with the GS). Radiation dose was measured each time, and the GS-applied images were reconstructed by weighted filtered back projection and IMAR. In the phantom study, image artifacts were significantly reduced by using IMAR (P = 0.031), whereas the GS reduced the radiation dose by 61.3%. In the clinical study (n = 29), IMAR mitigated artifacts from the GS, thus 96.6% of the IMAR image sets were clinically usable. Gonadal shielding reduced the radiation dose to the testes by 69.0%. The GS in conjunction with IMAR significantly reduced the radiation dose to the testes while maintaining the image quality.

  7. Evaluation of normalized metal artifact reduction (NMAR) in kVCT using MVCT prior images for radiotherapy treatment planning

    International Nuclear Information System (INIS)

    Paudel, M. R.; Mackenzie, M.; Rathee, S.; Fallone, B. G.

    2013-01-01

    Purpose: To evaluate the metal artifacts in kilovoltage computed tomography (kVCT) images that are corrected using a normalized metal artifact reduction (NMAR) method with megavoltage CT (MVCT) prior images.Methods: Tissue characterization phantoms containing bilateral steel inserts are used in all experiments. Two MVCT images, one without any metal artifact corrections and the other corrected using a modified iterative maximum likelihood polychromatic algorithm for CT (IMPACT) are translated to pseudo-kVCT images. These are then used as prior images without tissue classification in an NMAR technique for correcting the experimental kVCT image. The IMPACT method in MVCT included an additional model for the pair/triplet production process and the energy dependent response of the MVCT detectors. An experimental kVCT image, without the metal inserts and reconstructed using the filtered back projection (FBP) method, is artificially patched with the known steel inserts to get a reference image. The regular NMAR image containing the steel inserts that uses tissue classified kVCT prior and the NMAR images reconstructed using MVCT priors are compared with the reference image for metal artifact reduction. The Eclipse treatment planning system is used to calculate radiotherapy dose distributions on the corrected images and on the reference image using the Anisotropic Analytical Algorithm with 6 MV parallel opposed 5 × 10 cm 2 fields passing through the bilateral steel inserts, and the results are compared. Gafchromic film is used to measure the actual dose delivered in a plane perpendicular to the beams at the isocenter.Results: The streaking and shading in the NMAR image using tissue classifications are significantly reduced. However, the structures, including metal, are deformed. Some uniform regions appear to have eroded from one side. There is a large variation of attenuation values inside the metal inserts. Similar results are seen in commercially corrected image. Use

  8. Metal Artifact Reduction in X-ray Computed Tomography Using Computer-Aided Design Data of Implants as Prior Information.

    Science.gov (United States)

    Ruth, Veikko; Kolditz, Daniel; Steiding, Christian; Kalender, Willi A

    2017-06-01

    The performance of metal artifact reduction (MAR) methods in x-ray computed tomography (CT) suffers from incorrect identification of metallic implants in the artifact-affected volumetric images. The aim of this study was to investigate potential improvements of state-of-the-art MAR methods by using prior information on geometry and material of the implant. The influence of a novel prior knowledge-based segmentation (PS) compared with threshold-based segmentation (TS) on 2 MAR methods (linear interpolation [LI] and normalized-MAR [NORMAR]) was investigated. The segmentation is the initial step of both MAR methods. Prior knowledge-based segmentation uses 3-dimensional registered computer-aided design (CAD) data as prior knowledge to estimate the correct position and orientation of the metallic objects. Threshold-based segmentation uses an adaptive threshold to identify metal. Subsequently, for LI and NORMAR, the selected voxels are projected into the raw data domain to mark metal areas. Attenuation values in these areas are replaced by different interpolation schemes followed by a second reconstruction. Finally, the previously selected metal voxels are replaced by the metal voxels determined by PS or TS in the initial reconstruction. First, we investigated in an elaborate phantom study if the knowledge of the exact implant shape extracted from the CAD data provided by the manufacturer of the implant can improve the MAR result. Second, the leg of a human cadaver was scanned using a clinical CT system before and after the implantation of an artificial knee joint. The results were compared regarding segmentation accuracy, CT number accuracy, and the restoration of distorted structures. The use of PS improved the efficacy of LI and NORMAR compared with TS. Artifacts caused by insufficient segmentation were reduced, and additional information was made available within the projection data. The estimation of the implant shape was more exact and not dependent on a threshold

  9. SU-E-T-396: Dosimetric Accuracy of Proton Therapy for Patients with Metal Implants in CT Scans Using Metal Deletion Technique (MDT) Artifacts Reduction

    International Nuclear Information System (INIS)

    Li, X; Kantor, M; Zhu, X; Frank, S; Sahoo, N; Li, H

    2014-01-01

    Purpose: To evaluate the dosimetric accuracy for proton therapy patients with metal implants in CT using metal deletion technique (MDT) artifacts reduction. Methods: Proton dose accuracies under CT metal artifacts were first evaluated using a water phantom with cylindrical inserts of different materials (titanium and steel). Ranges and dose profiles along different beam angles were calculated using treatment planning system (Eclipse version 8.9) on uncorrected CT, MDT CT, and manually-corrected CT, where true Hounsfield units (water) were assigned to the streak artifacts. In patient studies, the treatment plans were developed on manually-corrected CTs, then recalculated on MDT and uncorrected CTs. DVH indices were compared between the dose distributions on all the CTs. Results: For water phantom study with 1/2 inch titanium insert, the proton range differences estimated by MDT CT were with 1% for all beam angles, while the range error can be up to 2.6% for uncorrected CT. For the study with 1 inch stainless steel insert, the maximum range error calculated by MDT CT was 1.09% among all the beam angles compared with maximum range error with 4.7% for uncorrected CT. The dose profiles calculated on MDT CTs for both titanium and steel inserts showed very good agreements with the ones calculated on manually-corrected CTs, while large dose discrepancies calculated using uncorrected CTs were observed in the distal end region of the proton beam. The patient study showed similar dose distribution and DVHs for organs near the metal artifacts recalculated on MDT CT compared with the ones calculated on manually-corrected CT, while the differences between uncorrected and corrected CTs were much pronounced. Conclusion: In proton therapy, large dose error could occur due to metal artifact. The MDT CT can be used for proton dose calculation to achieve similar dose accuracy as the current clinical practice using manual correction

  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. Clinical Evaluation of Normalized Metal Artifact Reduction in kVCT Using MVCT Prior Images (MVCT-NMAR) for Radiation Therapy Treatment Planning

    Energy Technology Data Exchange (ETDEWEB)

    Paudel, Moti Raj, E-mail: mpaudel@ualberta.ca [Department of Oncology, University of Alberta, Edmonton, AB (Canada); Mackenzie, Marc [Department of Oncology, University of Alberta, Edmonton, AB (Canada); Fallone, B. Gino [Department of Oncology, University of Alberta, Edmonton, AB (Canada); Department of Physics, University of Alberta, Edmonton, AB (Canada); Department of Medical Physics, Cross Cancer Institute, Edmonton, AB (Canada); Rathee, Satyapal [Department of Oncology, University of Alberta, Edmonton, AB (Canada); Department of Medical Physics, Cross Cancer Institute, Edmonton, AB (Canada)

    2014-07-01

    Purpose: To evaluate the metal artifacts in diagnostic kilovoltage computed tomography (kVCT) images of patients that are corrected by use of a normalized metal artifact reduction (NMAR) method with megavoltage CT (MVCT) prior images: MVCT-NMAR. Methods and Materials: MVCT-NMAR was applied to images from 5 patients: 3 with dual hip prostheses, 1 with a single hip prosthesis, and 1 with dental fillings. The corrected images were evaluated for visualization of tissue structures and their interfaces and for radiation therapy dose calculations. They were compared against the corresponding images corrected by the commercial orthopedic metal artifact reduction algorithm in a Phillips CT scanner. Results: The use of MVCT images for correcting kVCT images in the MVCT-NMAR technique greatly reduces metal artifacts, avoids secondary artifacts, and makes patient images more useful for correct dose calculation in radiation therapy. These improvements are significant, provided the MVCT and kVCT images are correctly registered. The remaining and the secondary artifacts (soft tissue blurring, eroded bones, false bones or air pockets, CT number cupping within the metal) present in orthopedic metal artifact reduction corrected images are removed in the MVCT-NMAR corrected images. A large dose reduction was possible outside the planning target volume (eg, 59.2 Gy to 52.5 Gy in pubic bone) when these MVCT-NMAR corrected images were used in TomoTherapy treatment plans without directional blocks for a prostate cancer patient. Conclusions: The use of MVCT-NMAR corrected images in radiation therapy treatment planning could improve the treatment plan quality for patients with metallic implants.

  12. SU-E-I-63: Quantitative Evaluation of the Effects of Orthopedic Metal Artifact Reduction (OMAR) Software On CT Images for Radiotherapy Simulation

    Energy Technology Data Exchange (ETDEWEB)

    Jani, S [Sharp Memorial Hospital, San Diego, CA (United States)

    2014-06-01

    Purpose: CT simulation for patients with metal implants can often be challenging due to artifacts that obscure tumor/target delineation and normal organ definition. Our objective was to evaluate the effectiveness of Orthopedic Metal Artifact Reduction (OMAR), a commercially available software, in reducing metal-induced artifacts and its effect on computed dose during treatment planning. Methods: CT images of water surrounding metallic cylindrical rods made of aluminum, copper and iron were studied in terms of Hounsfield Units (HU) spread. Metal-induced artifacts were characterized in terms of HU/Volume Histogram (HVH) using the Pinnacle treatment planning system. Effects of OMAR on enhancing our ability to delineate organs on CT and subsequent dose computation were examined in nine (9) patients with hip implants and two (2) patients with breast tissue expanders. Results: Our study characterized water at 1000 HU with a standard deviation (SD) of about 20 HU. The HVHs allowed us to evaluate how the presence of metal changed the HU spread. For example, introducing a 2.54 cm diameter copper rod in water increased the SD in HU of the surrounding water from 20 to 209, representing an increase in artifacts. Subsequent use of OMAR brought the SD down to 78. Aluminum produced least artifacts whereas Iron showed largest amount of artifacts. In general, an increase in kVp and mA during CT scanning showed better effectiveness of OMAR in reducing artifacts. Our dose analysis showed that some isodose contours shifted by several mm with OMAR but infrequently and were nonsignificant in planning process. Computed volumes of various dose levels showed <2% change. Conclusions: In our experience, OMAR software greatly reduced the metal-induced CT artifacts for the majority of patients with implants, thereby improving our ability to delineate tumor and surrounding organs. OMAR had a clinically negligible effect on computed dose within tissues. Partially funded by unrestricted

  13. Metal artifact reduction software used with abdominopelvic dual-energy CT of patients with metal hip prostheses: assessment of image quality and clinical feasibility.

    Science.gov (United States)

    Han, Seung Chol; Chung, Yong Eun; Lee, Young Han; Park, Kwan Kyu; Kim, Myeong Jin; Kim, Ki Whang

    2014-10-01

    The objective of our study was to determine the feasibility of using Metal Artifact Reduction (MAR) software for abdominopelvic dual-energy CT in patients with metal hip prostheses. This retrospective study included 33 patients (male-female ratio, 19:14; mean age, 63.7 years) who received total hip replacements and 20 patients who did not have metal prostheses as the control group. All of the patients underwent dual-energy CT. The quality of the images reconstructed using the MAR algorithm and of those reconstructed using the standard reconstruction was evaluated in terms of the visibility of the bladder wall, pelvic sidewall, rectal shelf, and bone-prosthesis interface and the overall diagnostic image quality with a 4-point scale. The mean and SD attenuation values in Hounsfield units were measured in the bladder, pelvic sidewall, and rectal shelf. For validation of the MAR interpolation algorithm, pelvis phantoms with small bladder "lesions" and metal hip prostheses were made, and images of the phantoms both with and without MAR reconstruction were evaluated. Image quality was significantly better with MAR reconstruction than without at all sites except the rectal shelf, where the image quality either had not changed or had worsened after MAR reconstruction. The mean attenuation value was changed after MAR reconstruction to its original expected value at the pelvic sidewall (p software with dual-energy CT decreases metal artifacts and increases diagnostic confidence in the assessment of the pelvic cavity but also introduces new artifacts that can obscure pelvic structures.

  14. SU-E-I-13: Evaluation of Metal Artifact Reduction (MAR) Software On Computed Tomography (CT) Images

    International Nuclear Information System (INIS)

    Huang, V; Kohli, K

    2015-01-01

    Purpose: A new commercially available metal artifact reduction (MAR) software in computed tomography (CT) imaging was evaluated with phantoms in the presence of metals. The goal was to assess the ability of the software to restore the CT number in the vicinity of the metals without impacting the image quality. Methods: A Catphan 504 was scanned with a GE Optima RT 580 CT scanner (GE Healthcare, Milwaukee, WI) and the images were reconstructed with and without the MAR software. Both datasets were analyzed with Image Owl QA software (Image Owl Inc, Greenwich, NY). CT number sensitometry, MTF, low contrast, uniformity, noise and spatial accuracy were compared for scans with and without MAR software. In addition, an in-house made phantom was scanned with and without a stainless steel insert at three different locations. The accuracy of the CT number and metal insert dimension were investigated as well. Results: Comparisons between scans with and without MAR algorithm on the Catphan phantom demonstrate similar results for image quality. However, noise was slightly higher for the MAR algorithm. Evaluation of the CT number at various locations of the in-house made phantom was also performed. The baseline HU, obtained from the scan without metal insert, was compared to scans with the stainless steel insert at 3 different locations. The HU difference between the baseline scan versus metal scan was improved when the MAR algorithm was applied. In addition, the physical diameter of the stainless steel rod was over-estimated by the MAR algorithm by 0.9 mm. Conclusion: This work indicates with the presence of metal in CT scans, the MAR algorithm is capable of providing a more accurate CT number without compromising the overall image quality. Future work will include the dosimetric impact on the MAR algorithm

  15. Planning and clinical studies of a commercial orthopedic metal artifact reduction tool for CT simulations for head-and-neck radiotherapy

    International Nuclear Information System (INIS)

    Kon, Hyuck Jun; Ye, Sung Joon; Kim, Jung In; Park, Jong Min; Lee, Jae Gi; Heo, Tae Min; Kim Kyung Su; Chun, Young Mi; Callahan, Zachariah

    2013-01-01

    In computed tomography (CT) images, the presence of high Z materials induces typical streak artifacts, called metal artifacts which can pervert CT Hounsfield numbers in the reconstructed images. These artifact-induced distortion of CT images can impact on the dose calculation based on the CT images. In the radiation therapy of Head-and-Neck cancer because of the concave-shaped target volumes, the complex anatomy, a lot of sensitive normal tissues and air cavity structures, it is important to get accurate CT images for dose calculation. But dental implant is common for H and N patients so that it is hard to get undistorted CT images. Moreover because dental implants are generally with the air cavity like oral cavity and nasal cavity in the same CT slice, they can make lots of distortion. In this study, we focused on evaluating the distortion on air cavity by the metal artifact and the effectiveness of the commercial orthopedic metal artifact reduction function (O-MAR) about the metal artifacts induced by the dental implant. The O-MAR algorithm increases the accuracy of CT Hounsfield numbers and reducing noises. Thus, it can contribute to the entire radiation treatment planning process, especially for contouring/segmentation. Although there was no significant difference in dose distributions for most cases, the O-MAR correction was shown to have an impact on high dose regions in air cavity

  16. Planning and clinical studies of a commercial orthopedic metal artifact reduction tool for CT simulations for head-and-neck radiotherapy

    Energy Technology Data Exchange (ETDEWEB)

    Kon, Hyuck Jun; Ye, Sung Joon [Interdisplinary Program in Radiation Applied Life Science, Seoul National University Graduate School, Seoul (Korea, Republic of); Kim, Jung In; Park, Jong Min; Lee, Jae Gi; Heo, Tae Min [Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul (Korea, Republic of); Kim Kyung Su [Dept. of Radiation Oncology, Seoul National University College of Medicine, Seoul (Korea, Republic of); Chun, Young Mi [Philips Healthcare Korea, Seoul (Korea, Republic of); Callahan, Zachariah [Program in Biomedical Radiation Sciences, Dept. of Transdisciplinary Studies, Graduate School of Convergence Science and Technology, Seoul National University, Seoul (Korea, Republic of)

    2013-11-15

    In computed tomography (CT) images, the presence of high Z materials induces typical streak artifacts, called metal artifacts which can pervert CT Hounsfield numbers in the reconstructed images. These artifact-induced distortion of CT images can impact on the dose calculation based on the CT images. In the radiation therapy of Head-and-Neck cancer because of the concave-shaped target volumes, the complex anatomy, a lot of sensitive normal tissues and air cavity structures, it is important to get accurate CT images for dose calculation. But dental implant is common for H and N patients so that it is hard to get undistorted CT images. Moreover because dental implants are generally with the air cavity like oral cavity and nasal cavity in the same CT slice, they can make lots of distortion. In this study, we focused on evaluating the distortion on air cavity by the metal artifact and the effectiveness of the commercial orthopedic metal artifact reduction function (O-MAR) about the metal artifacts induced by the dental implant. The O-MAR algorithm increases the accuracy of CT Hounsfield numbers and reducing noises. Thus, it can contribute to the entire radiation treatment planning process, especially for contouring/segmentation. Although there was no significant difference in dose distributions for most cases, the O-MAR correction was shown to have an impact on high dose regions in air cavity.

  17. Dynamic re-weighted total variation technique and statistic Iterative reconstruction method for x-ray CT metal artifact reduction

    Science.gov (United States)

    Peng, Chengtao; Qiu, Bensheng; Zhang, Cheng; Ma, Changyu; Yuan, Gang; Li, Ming

    2017-07-01

    Over the years, the X-ray computed tomography (CT) has been successfully used in clinical diagnosis. However, when the body of the patient to be examined contains metal objects, the image reconstructed would be polluted by severe metal artifacts, which affect the doctor's diagnosis of disease. In this work, we proposed a dynamic re-weighted total variation (DRWTV) technique combined with the statistic iterative reconstruction (SIR) method to reduce the artifacts. The DRWTV method is based on the total variation (TV) and re-weighted total variation (RWTV) techniques, but it provides a sparser representation than TV and protects the tissue details better than RWTV. Besides, the DRWTV can suppress the artifacts and noise, and the SIR convergence speed is also accelerated. The performance of the algorithm is tested on both simulated phantom dataset and clinical dataset, which are the teeth phantom with two metal implants and the skull with three metal implants, respectively. The proposed algorithm (SIR-DRWTV) is compared with two traditional iterative algorithms, which are SIR and SIR constrained by RWTV regulation (SIR-RWTV). The results show that the proposed algorithm has the best performance in reducing metal artifacts and protecting tissue details.

  18. 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

  19. 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

  20. Evaluation of Orthopedic Metal Artifact Reduction Application in Three-Dimensional Computed Tomography Reconstruction of Spinal Instrumentation: A Single Saudi Center Experience.

    Science.gov (United States)

    Ali, Amir Monir

    2018-01-01

    The aim of the study was to evaluate the commercially available orthopedic metal artifact reduction (OMAR) technique in postoperative three-dimensional computed tomography (3DCT) reconstruction studies after spinal instrumentation and to investigate its clinical application. One hundred and twenty (120) patients with spinal metallic implants were included in the study. All had 3DCT reconstruction examinations using the OMAR software after obtaining the informed consents and approval of the Institution Ethical Committee. The degree of the artifacts, the related muscular density, the clearness of intermuscular fat planes, and definition of the adjacent vertebrae were qualitatively evaluated. The diagnostic satisfaction and quality of the 3D reconstruction images were thoroughly assessed. The majority (96.7%) of 3DCT reconstruction images performed were considered satisfactory to excellent for diagnosis. Only 3.3% of the reconstructed images had rendered unacceptable diagnostic quality. OMAR can effectively reduce metallic artifacts in patients with spinal instrumentation with highly diagnostic 3DCT reconstruction images.

  1. Improved image quality in abdominal CT in patients who underwent treatment for hepatocellular carcinoma with small metal implants using a raw data-based metal artifact reduction algorithm.

    Science.gov (United States)

    Sofue, Keitaro; Yoshikawa, Takeshi; Ohno, Yoshiharu; Negi, Noriyuki; Inokawa, Hiroyasu; Sugihara, Naoki; Sugimura, Kazuro

    2017-07-01

    To determine the value of a raw data-based metal artifact reduction (SEMAR) algorithm for image quality improvement in abdominal CT for patients with small metal implants. Fifty-eight patients with small metal implants (3-15 mm in size) who underwent treatment for hepatocellular carcinoma were imaged with CT. CT data were reconstructed by filtered back projection with and without SEMAR algorithm in axial and coronal planes. To evaluate metal artefact reduction, mean CT number (HU and SD) and artefact index (AI) values within the liver were calculated. Two readers independently evaluated image quality of the liver and pancreas and visualization of vasculature using a 5-point visual score. HU and AI values and image quality on images with and without SEMAR were compared using the paired Student's t-test and Wilcoxon signed rank test. Interobserver agreement was evaluated using linear-weighted κ test. Mean HU and AI on images with SEMAR was significantly lower than those without SEMAR (P small metal implants by reducing metallic artefacts. • SEMAR algorithm significantly reduces metallic artefacts from small implants in abdominal CT. • SEMAR can improve image quality of the liver in dynamic CECT. • Confidence visualization of hepatic vascular anatomies can also be improved by SEMAR.

  2. Metal artifact reduction for flat panel detector intravenous CT angiography in patients with intracranial metallic implants after endovascular and surgical treatment.

    Science.gov (United States)

    Pjontek, Rastislav; Önenköprülü, Belgin; Scholz, Bernhard; Kyriakou, Yiannis; Schubert, Gerrit A; Nikoubashman, Omid; Othman, Ahmed; Wiesmann, Martin; Brockmann, Marc A

    2016-08-01

    Flat panel detector CT angiography with intravenous contrast agent injection (IV CTA) allows high-resolution imaging of cerebrovascular structures. Artifacts caused by metallic implants like platinum coils or clips lead to degradation of image quality and are a significant problem. To evaluate the influence of a prototype metal artifact reduction (MAR) algorithm on image quality in patients with intracranial metallic implants. Flat panel detector CT after intravenous application of 80 mL contrast agent was performed with an angiography system (Artis zee; Siemens, Forchheim, Germany) using a 20 s rotation protocol (200° rotation angle, 20 s acquisition time, 496 projections). The data before and after MAR of 26 patients with a total of 34 implants (coils, clips, stents) were independently evaluated by two blinded neuroradiologists. MAR improved the assessability of the brain parenchyma and small vessels (diameter metallic implants and at a distance of 6 cm (p<0.001 each, Wilcoxon test). Furthermore, MAR significantly improved the assessability of parent vessel patency and potential aneurysm remnants (p<0.005 each, McNemar test). MAR, however, did not improve assessability of stented vessels. When an intravenous contrast protocol is used, MAR significantly ameliorates the assessability of brain parenchyma, vessels, and treated aneurysms in patients with intracranial coils or clips. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

  3. MSVAT-SPACE-STIR and SEMAC-STIR for Reduction of Metallic Artifacts in 3T Head and Neck MRI.

    Science.gov (United States)

    Hilgenfeld, T; Prager, M; Schwindling, F S; Nittka, M; Rammelsberg, P; Bendszus, M; Heiland, S; Juerchott, A

    2018-05-24

    The incidence of metallic dental restorations and implants is increasing, and head and neck MR imaging is becoming challenging regarding artifacts. Our aim was to evaluate whether multiple-slab acquisition with view angle tilting gradient based on a sampling perfection with application-optimized contrasts by using different flip angle evolution (MSVAT-SPACE)-STIR and slice-encoding for metal artifact correction (SEMAC)-STIR are beneficial regarding artifact suppression compared with the SPACE-STIR and TSE-STIR in vitro and in vivo. At 3T, 3D artifacts of 2 dental implants, supporting different single crowns, were evaluated. Image quality was evaluated quantitatively (normalized signal-to-noise ratio) and qualitatively (2 reads by 2 blinded radiologists). Feasibility was tested in vivo in 5 volunteers and 5 patients, respectively. Maximum achievable resolution and the normalized signal-to-noise ratio of MSVAT-SPACE-STIR were higher compared with SEMAC-STIR. Performance in terms of artifact correction was dependent on the material composition. For highly paramagnetic materials, SEMAC-STIR was superior to MSVAT-SPACE-STIR (27.8% smaller artifact volume) and TSE-STIR (93.2% less slice distortion). However, MSVAT-SPACE-STIR reduced the artifact size compared with SPACE-STIR by 71.5%. For low-paramagnetic materials, MSVAT-SPACE-STIR performed as well as SEMAC-STIR. Furthermore, MSVAT-SPACE-STIR decreased artifact volume by 69.5% compared with SPACE-STIR. The image quality of all sequences did not differ systematically. In vivo results were comparable with in vitro results. Regarding susceptibility artifacts and acquisition time, MSVAT-SPACE-STIR might be advantageous over SPACE-STIR for high-resolution and isotropic head and neck imaging. Only for materials with high-susceptibility differences to soft tissue, the use of SEMAC-STIR might be beneficial. Within limited acquisition times, SEMAC-STIR cannot exploit its full advantage over TSE-STIR regarding artifact

  4. Improved image quality in abdominal CT in patients who underwent treatment for hepatocellular carcinoma with small metal implants using a raw data-based metal artifact reduction algorithm

    Energy Technology Data Exchange (ETDEWEB)

    Sofue, Keitaro; Sugimura, Kazuro [Kobe University Graduate School of Medicine, Department of Radiology, Kobe, Hyogo (Japan); Yoshikawa, Takeshi; Ohno, Yoshiharu [Kobe University Graduate School of Medicine, Advanced Biomedical Imaging Research Center, Kobe, Hyogo (Japan); Kobe University Graduate School of Medicine, Division of Functional and Diagnostic Imaging Research, Department of Radiology, Kobe, Hyogo (Japan); Negi, Noriyuki [Kobe University Hospital, Division of Radiology, Kobe, Hyogo (Japan); Inokawa, Hiroyasu; Sugihara, Naoki [Toshiba Medical Systems Corporation, Otawara, Tochigi (Japan)

    2017-07-15

    To determine the value of a raw data-based metal artifact reduction (SEMAR) algorithm for image quality improvement in abdominal CT for patients with small metal implants. Fifty-eight patients with small metal implants (3-15 mm in size) who underwent treatment for hepatocellular carcinoma were imaged with CT. CT data were reconstructed by filtered back projection with and without SEMAR algorithm in axial and coronal planes. To evaluate metal artefact reduction, mean CT number (HU and SD) and artefact index (AI) values within the liver were calculated. Two readers independently evaluated image quality of the liver and pancreas and visualization of vasculature using a 5-point visual score. HU and AI values and image quality on images with and without SEMAR were compared using the paired Student's t-test and Wilcoxon signed rank test. Interobserver agreement was evaluated using linear-weighted κ test. Mean HU and AI on images with SEMAR was significantly lower than those without SEMAR (P < 0.0001). Liver and pancreas image qualities and visualizations of vasculature were significantly improved on CT with SEMAR (P < 0.0001) with substantial or almost perfect agreement (0.62 ≤ κ ≤ 0.83). SEMAR can improve image quality in abdominal CT in patients with small metal implants by reducing metallic artefacts. (orig.)

  5. Improved image quality in abdominal CT in patients who underwent treatment for hepatocellular carcinoma with small metal implants using a raw data-based metal artifact reduction algorithm

    International Nuclear Information System (INIS)

    Sofue, Keitaro; Sugimura, Kazuro; Yoshikawa, Takeshi; Ohno, Yoshiharu; Negi, Noriyuki; Inokawa, Hiroyasu; Sugihara, Naoki

    2017-01-01

    To determine the value of a raw data-based metal artifact reduction (SEMAR) algorithm for image quality improvement in abdominal CT for patients with small metal implants. Fifty-eight patients with small metal implants (3-15 mm in size) who underwent treatment for hepatocellular carcinoma were imaged with CT. CT data were reconstructed by filtered back projection with and without SEMAR algorithm in axial and coronal planes. To evaluate metal artefact reduction, mean CT number (HU and SD) and artefact index (AI) values within the liver were calculated. Two readers independently evaluated image quality of the liver and pancreas and visualization of vasculature using a 5-point visual score. HU and AI values and image quality on images with and without SEMAR were compared using the paired Student's t-test and Wilcoxon signed rank test. Interobserver agreement was evaluated using linear-weighted κ test. Mean HU and AI on images with SEMAR was significantly lower than those without SEMAR (P < 0.0001). Liver and pancreas image qualities and visualizations of vasculature were significantly improved on CT with SEMAR (P < 0.0001) with substantial or almost perfect agreement (0.62 ≤ κ ≤ 0.83). SEMAR can improve image quality in abdominal CT in patients with small metal implants by reducing metallic artefacts. (orig.)

  6. MO-DE-207A-10: One-Step CT Reconstruction for Metal Artifact Reduction by a Modification of Penalized Weighted Least-Squares (PWLS)

    Energy Technology Data Exchange (ETDEWEB)

    Kim, H; Chen, J [University of California San Francisco, San Francisco, CA (United States)

    2016-06-15

    Purpose: Metal objects create severe artifacts in kilo-voltage (kV) CT image reconstructions due to the high attenuation coefficients of high atomic number objects. Most of the techniques devised to reduce this artifact utilize a two-step approach, which do not reliably yield the qualified reconstructed images. Thus, for accuracy and simplicity, this work presents a one-step reconstruction method based on a modified penalized weighted least-squares (PWLS) technique. Methods: Existing techniques for metal artifact reduction mostly adopt a two-step approach, which conduct additional reconstruction with the modified projection data from the initial reconstruction. This procedure does not consistently perform well due to the uncertainties in manipulating the metal-contaminated projection data by thresholding and linear interpolation. This study proposes a one-step reconstruction process using a new PWLS operation with total-variation (TV) minimization, while not manipulating the projection. The PWLS for CT reconstruction has been investigated using a pre-defined weight, based on the variance of the projection datum at each detector bin. It works well when reconstructing CT images from metal-free projection data, which does not appropriately penalize metal-contaminated projection data. The proposed work defines the weight at each projection element under the assumption of a Poisson random variable. This small modification using element-wise penalization has a large impact in reducing metal artifacts. For evaluation, the proposed technique was assessed with two noisy, metal-contaminated digital phantoms, against the existing PWLS with TV minimization and the two-step approach. Result: The proposed PWLS with TV minimization greatly improved the metal artifact reduction, relative to the other techniques, by watching the results. Numerically, the new approach lowered the normalized root-mean-square error about 30 and 60% for the two cases, respectively, compared to the two

  7. Impact of metal artifact reduction software on image quality of gemstone spectral imaging dual-energy cerebral CT angiography after intracranial aneurysm clipping

    Energy Technology Data Exchange (ETDEWEB)

    Dunet, Vincent; Bernasconi, Martine; Hajdu, Steven David; Meuli, Reto Antoine; Zerlauth, Jean-Baptiste [Lausanne University Hospital, Department of Diagnostic and Interventional Radiology, Lausanne (Switzerland); Daniel, Roy Thomas [Lausanne University Hospital, Department of Neurosurgery, Lausanne (Switzerland)

    2017-09-15

    We aimed to assess the impact of metal artifact reduction software (MARs) on image quality of gemstone spectral imaging (GSI) dual-energy (DE) cerebral CT angiography (CTA) after intracranial aneurysm clipping. This retrospective study was approved by the institutional review board, which waived patient written consent. From January 2013 to September 2016, single source DE cerebral CTA were performed in 45 patients (mean age: 60 ± 9 years, male 9) after intracranial aneurysm clipping and reconstructed with and without MARs. Signal-to-noise (SNR), contrast-to-noise (CNR), and relative CNR (rCNR) ratios were calculated from attenuation values measured in the internal carotid artery (ICA) and middle cerebral artery (MCA). Volume of clip and artifacts and relative clip blurring reduction (rCBR) ratios were also measured at each energy level with/without MARs. Variables were compared between GSI and GSI-MARs using the paired Wilcoxon signed-rank test. MARs significantly reduced metal artifacts at all energy levels but 130 and 140 keV, regardless of clips' location and number. The optimal rCBR was obtained at 110 and 80 keV, respectively, on GSI and GSI-MARs images, with up to 96% rCNR increase on GSI-MARs images. The best compromise between metal artifact reduction and rCNR was obtained at 70-75 and 65-70 keV for GSI and GSI-MARs images, respectively, with up to 15% rCBR and rCNR increase on GSI-MARs images. MARs significantly reduces metal artifacts on DE cerebral CTA after intracranial aneurysm clipping regardless of clips' location and number. It may be used to reduce radiation dose while increasing CNR. (orig.)

  8. SU-E-I-92: Is Photon Starvation Preventing Metal Artifact Reduction Algorithm From Working in KVCT?

    Energy Technology Data Exchange (ETDEWEB)

    Paudel, M [University of Alberta, Cross Cancer Institute, Edmonton, AB (Canada); currently at University of Toronto, Sunnybrook Health Sciences Center, Toronto, ON (Canada); MacKenzie, M; Fallone, B; Rathee, S [University of Alberta, Cross Cancer Institute, Edmonton, AB (Canada)

    2014-06-01

    Purpose: High density/high atomic number metallic objects create shading and streaking metal artifacts in the CT image that can cause inaccurate delineation of anatomical structures or inaccurate radiation dose calculation. A modified iterative maximum-likelihood polychromatic algorithm for CT (mIMPACT) that models the energy response of detectors, photon interaction processes and beam polychromaticity has successfully reduced metal artifacts in MVCT. Our extension of mIMPACT in kVCT did not significantly reduce metal artifacts for high density metal like steel. We hypothesize that photon starvation may result in the measured data in a commercial kVCT imaging beam. Methods: We measured attenuation of a range of steel plate thicknesses, sandwiched between two 12cm thick solid water blocks, using a Phillips Big Bore CTTM scanner in scout acquisition mode with 120kVp and 200mAs. The transmitted signal (y) was normalized to the air scan signal (y{sub 0}) to get attenuation [i.e., ln(y/y{sub 0})] data for a detector. Results: Below steel plate thickness of 13.4mm, the variations in measured attenuation as a function of view number are characterized by a quantum noise and show increased attenuation with metal thickness. On or above this thickness the attenuation shows discrete levels in addition to the quantum noise. Some views have saturated attenuation value. The histograms of the measured attenuation for up to 36.7mm of steel show this trend. The detector signal is so small that the quantization levels in the analog to digital (A-to-D) converter are visible, a clear indication of photon starvation. Conclusion: Photons reaching the kVCT detector after passing through a thick metal plate are either so low in number that the signal measured has large quantum noise, or are completely absorbed inside the plate creating photon starvation. This is un-interpretable by the mIMPACT algorithm and cannot reduce metal artifacts in kVCT for certain realistic thicknesses of steel

  9. Voting strategy for artifact reduction in digital breast tomosynthesis

    International Nuclear Information System (INIS)

    Wu Tao; Moore, Richard H.; Kopans, Daniel B.

    2006-01-01

    Artifacts are observed in digital breast tomosynthesis (DBT) reconstructions due to the small number of projections and the narrow angular range that are typically employed in tomosynthesis imaging. In this work, we investigate the reconstruction artifacts that are caused by high-attenuation features in breast and develop several artifact reduction methods based on a 'voting strategy'. The voting strategy identifies the projection(s) that would introduce artifacts to a voxel and rejects the projection(s) when reconstructing the voxel. Four approaches to the voting strategy were compared, including projection segmentation, maximum contribution deduction, one-step classification, and iterative classification. The projection segmentation method, based on segmentation of high-attenuation features from the projections, effectively reduces artifacts caused by metal and large calcifications that can be reliably detected and segmented from projections. The other three methods are based on the observation that contributions from artifact-inducing projections have higher value than those from normal projections. These methods attempt to identify the projection(s) that would cause artifacts by comparing contributions from different projections. Among the three methods, the iterative classification method provides the best artifact reduction; however, it can generate many false positive classifications that degrade the image quality. The maximum contribution deduction method and one-step classification method both reduce artifacts well from small calcifications, although the performance of artifact reduction is slightly better with the one-step classification. The combination of one-step classification and projection segmentation removes artifacts from both large and small calcifications

  10. Reduction of metal artifacts due to dental hardware in computed tomography angiography: assessment of the utility of model-based iterative reconstruction

    Energy Technology Data Exchange (ETDEWEB)

    Kuya, Keita; Shinohara, Yuki; Ogawa, Toshihide [Tottori University, Division of Radiology, Department of Pathophysiological and Therapeutic Science, Faculty of Medicine, Yonago (Japan); Kato, Ayumi [Tottori Municipal Hospital, Department of Radiology, Yonago (Japan); Sakamoto, Makoto; Kurosaki, Masamichi [Tottori University, Division of Neurosurgery, Department of Neurological Sciences, Faculty of Medicine, Yonago (Japan)

    2017-03-15

    The aim of this study is to assess the value of adaptive statistical iterative reconstruction (ASIR) and model-based iterative reconstruction (MBIR) for reduction of metal artifacts due to dental hardware in carotid CT angiography (CTA). Thirty-seven patients with dental hardware who underwent carotid CTA were included. CTA was performed with a GE Discovery CT750 HD scanner and reconstructed with filtered back projection (FBP), ASIR, and MBIR. We measured the standard deviation at the cervical segment of the internal carotid artery that was affected most by dental metal artifacts (SD{sub 1}) and the standard deviation at the common carotid artery that was not affected by the artifact (SD{sub 2}). We calculated the artifact index (AI) as follows: AI = [(SD{sub 1})2 - (SD{sub 2})2]1/2 and compared each AI for FBP, ASIR, and MBIR. Visual assessment of the internal carotid artery was also performed by two neuroradiologists using a five-point scale for each axial and reconstructed sagittal image. The inter-observer agreement was analyzed using weighted kappa analysis. MBIR significantly improved AI compared with FBP and ASIR (p < 0.001, each). We found no significant difference in AI between FBP and ASIR (p = 0.502). The visual score of MBIR was significantly better than those of FBP and ASIR (p < 0.001, each), whereas the scores of ASIR were the same as those of FBP. Kappa values indicated good inter-observer agreements in all reconstructed images (0.747-0.778). MBIR resulted in a significant reduction in artifact from dental hardware in carotid CTA. (orig.)

  11. Reduction of metal artifacts due to dental hardware in computed tomography angiography: assessment of the utility of model-based iterative reconstruction

    International Nuclear Information System (INIS)

    Kuya, Keita; Shinohara, Yuki; Ogawa, Toshihide; Kato, Ayumi; Sakamoto, Makoto; Kurosaki, Masamichi

    2017-01-01

    The aim of this study is to assess the value of adaptive statistical iterative reconstruction (ASIR) and model-based iterative reconstruction (MBIR) for reduction of metal artifacts due to dental hardware in carotid CT angiography (CTA). Thirty-seven patients with dental hardware who underwent carotid CTA were included. CTA was performed with a GE Discovery CT750 HD scanner and reconstructed with filtered back projection (FBP), ASIR, and MBIR. We measured the standard deviation at the cervical segment of the internal carotid artery that was affected most by dental metal artifacts (SD_1) and the standard deviation at the common carotid artery that was not affected by the artifact (SD_2). We calculated the artifact index (AI) as follows: AI = [(SD_1)2 - (SD_2)2]1/2 and compared each AI for FBP, ASIR, and MBIR. Visual assessment of the internal carotid artery was also performed by two neuroradiologists using a five-point scale for each axial and reconstructed sagittal image. The inter-observer agreement was analyzed using weighted kappa analysis. MBIR significantly improved AI compared with FBP and ASIR (p < 0.001, each). We found no significant difference in AI between FBP and ASIR (p = 0.502). The visual score of MBIR was significantly better than those of FBP and ASIR (p < 0.001, each), whereas the scores of ASIR were the same as those of FBP. Kappa values indicated good inter-observer agreements in all reconstructed images (0.747-0.778). MBIR resulted in a significant reduction in artifact from dental hardware in carotid CTA. (orig.)

  12. Effect of metal artifact reduction software on image quality of C-arm cone-beam computed tomography during intracranial aneurysm treatment.

    Science.gov (United States)

    Enomoto, Yukiko; Yamauchi, Keita; Asano, Takahiko; Otani, Katharina; Iwama, Toru

    2018-01-01

    Background and purpose C-arm cone-beam computed tomography (CBCT) has the drawback that image quality is degraded by artifacts caused by implanted metal objects. We evaluated whether metal artifact reduction (MAR) prototype software can improve the subjective image quality of CBCT images of patients with intracranial aneurysms treated with coils or clips. Materials and methods Forty-four patients with intracranial aneurysms implanted with coils (40 patients) or clips (four patients) underwent one CBCT scan from which uncorrected and MAR-corrected CBCT image datasets were reconstructed. Three blinded readers evaluated the image quality of the image sets using a four-point scale (1: Excellent, 2: Good, 3: Poor, 4: Bad). The median scores of the three readers of uncorrected and MAR-corrected images were compared with the paired Wilcoxon signed-rank and inter-reader agreement of change scores was assessed by weighted kappa statistics. The readers also recorded new clinical findings, such as intracranial hemorrhage, air, or surrounding anatomical structures on MAR-corrected images. Results The image quality of MAR-corrected CBCT images was significantly improved compared with the uncorrected CBCT image ( p software improved image quality of CBCT images degraded by metal artifacts.

  13. Metal-induced streak artifact reduction using iterative reconstruction algorithms in x-ray computed tomography image of the dentoalveolar region.

    Science.gov (United States)

    Dong, Jian; Hayakawa, Yoshihiko; Kannenberg, Sven; Kober, Cornelia

    2013-02-01

    The objective of this study was to reduce metal-induced streak artifact on oral and maxillofacial x-ray computed tomography (CT) images by developing the fast statistical image reconstruction system using iterative reconstruction algorithms. Adjacent CT images often depict similar anatomical structures in thin slices. So, first, images were reconstructed using the same projection data of an artifact-free image. Second, images were processed by the successive iterative restoration method where projection data were generated from reconstructed image in sequence. Besides the maximum likelihood-expectation maximization algorithm, the ordered subset-expectation maximization algorithm (OS-EM) was examined. Also, small region of interest (ROI) setting and reverse processing were applied for improving performance. Both algorithms reduced artifacts instead of slightly decreasing gray levels. The OS-EM and small ROI reduced the processing duration without apparent detriments. Sequential and reverse processing did not show apparent effects. Two alternatives in iterative reconstruction methods were effective for artifact reduction. The OS-EM algorithm and small ROI setting improved the performance. Copyright © 2012 Elsevier Inc. All rights reserved.

  14. Poster — Thur Eve — 11: Validation of the orthopedic metallic artifact reduction tool for CT simulations at the Ottawa Hospital Cancer Centre

    International Nuclear Information System (INIS)

    Sutherland, J; Foottit, C

    2014-01-01

    Metallic implants in patients can produce image artifacts in kilovoltage CT simulation images which can introduce noise and inaccuracies in CT number, affecting anatomical segmentation and dose distributions. The commercial orthopedic metal artifact reduction algorithm (O-MAR) (Philips Healthcare System) was recently made available on CT simulation scanners at our institution. This study validated the clinical use of O-MAR by investigating its effects on CT number and dose distributions. O-MAR corrected and uncorrected images were acquired with a Philips Brilliance Big Bore CT simulator of a cylindrical solid water phantom that contained various plugs (including metal) of known density. CT number accuracy was investigated by determining the mean and standard deviation in regions of interest (ROI) within each plug for uncorrected and O-MAR corrected images and comparing with no-metal image values. Dose distributions were calculated using the Monaco treatment planning system. Seven open fields were equally spaced about the phantom around a ROI near the center of the phantom. These were compared to a “correct” dose distribution calculated by overriding electron densities a no-metal phantom image to produce an image containing metal but no artifacts. An overall improvement in CT number and dose distribution accuracy was achieved by applying the O-MAR correction. Mean CT numbers and standard deviations were found to be generally improved. Exceptions included lung equivalent media, which is consistent with vendor specified contraindications. Dose profiles were found to vary by ±4% between uncorrected or O-MAR corrected images with O-MAR producing doses closer to ground truth

  15. Poster — Thur Eve — 11: Validation of the orthopedic metallic artifact reduction tool for CT simulations at the Ottawa Hospital Cancer Centre

    Energy Technology Data Exchange (ETDEWEB)

    Sutherland, J; Foottit, C [The Ottawa Hospital Cancer Centre (Canada)

    2014-08-15

    Metallic implants in patients can produce image artifacts in kilovoltage CT simulation images which can introduce noise and inaccuracies in CT number, affecting anatomical segmentation and dose distributions. The commercial orthopedic metal artifact reduction algorithm (O-MAR) (Philips Healthcare System) was recently made available on CT simulation scanners at our institution. This study validated the clinical use of O-MAR by investigating its effects on CT number and dose distributions. O-MAR corrected and uncorrected images were acquired with a Philips Brilliance Big Bore CT simulator of a cylindrical solid water phantom that contained various plugs (including metal) of known density. CT number accuracy was investigated by determining the mean and standard deviation in regions of interest (ROI) within each plug for uncorrected and O-MAR corrected images and comparing with no-metal image values. Dose distributions were calculated using the Monaco treatment planning system. Seven open fields were equally spaced about the phantom around a ROI near the center of the phantom. These were compared to a “correct” dose distribution calculated by overriding electron densities a no-metal phantom image to produce an image containing metal but no artifacts. An overall improvement in CT number and dose distribution accuracy was achieved by applying the O-MAR correction. Mean CT numbers and standard deviations were found to be generally improved. Exceptions included lung equivalent media, which is consistent with vendor specified contraindications. Dose profiles were found to vary by ±4% between uncorrected or O-MAR corrected images with O-MAR producing doses closer to ground truth.

  16. SU-F-J-175: Evaluation of Metal Artifact Reduction Algorithms in Computed Tomography and Their Application to Radiation Therapy Treatment Planning

    International Nuclear Information System (INIS)

    Norris, H; Rangaraj, D; Kim, S

    2016-01-01

    Purpose: High-Z (metal) implants in CT scans cause significant streak-like artifacts in the reconstructed dataset. This results in both inaccurate CT Hounsfield units for the tissue as well as obscuration of the target and organs at risk (OARs) for radiation therapy planning. Herein we analyze two metal artifact reduction algorithms: GE’s Smart MAR and a Metal Deletion Technique (MDT) for geometric and Hounsfield Unit (HU) accuracy. Methods: A CT-to-electron density phantom, with multiple inserts of various densities and a custom Cerrobend insert (Zeff=76.8), is utilized in this continuing study. The phantom is scanned without metal (baseline) and again with the metal insert. Using one set of projection data, reconstructed CT volumes are created with filtered-back-projection (FBP) and the MAR and the MDT algorithms. Regions-of-Interest (ROIs) are evaluated for each insert for HU accuracy; the metal insert’s Full-Width-Half-Maximum (FWHM) is used to evaluate the geometric accuracy. Streak severity is quantified with an HU error metric over the phantom volume. Results: The original FBP reconstruction has a Root-Mean-Square-Error (RMSE) of 57.55 HU (STD=29.19, range=−145.8 to +79.2) compared to baseline. The MAR reconstruction has a RMSE of 20.98 HU (STD=13.92, range=−18.3 to +61.7). The MDT reconstruction has a RMSE of 10.05 HU (STD=10.5, range=−14.8 to +18.6). FWHM for baseline=162.05; FBP=161.84 (−0.13%); MAR=162.36 (+0.19%); MDT=162.99 (+0.58%). Streak severity metric for FBP=19.73 (22.659% bad pixels); MAR=8.743 (9.538% bad); MDT=4.899 (5.303% bad). Conclusion: Image quality, in terms of HU accuracy, in the presence of high-Z metal objects in CT scans is improved by metal artifact reduction reconstruction algorithms. The MDT algorithm had the highest HU value accuracy (RMSE=10.05 HU) and best streak severity metric, but scored the worst in terms of geometric accuracy. Qualitatively, the MAR and MDT algorithms increased detectability of inserts

  17. SU-F-J-175: Evaluation of Metal Artifact Reduction Algorithms in Computed Tomography and Their Application to Radiation Therapy Treatment Planning

    Energy Technology Data Exchange (ETDEWEB)

    Norris, H; Rangaraj, D; Kim, S [Baylor Scott & White Health, Temple, TX (United States)

    2016-06-15

    Purpose: High-Z (metal) implants in CT scans cause significant streak-like artifacts in the reconstructed dataset. This results in both inaccurate CT Hounsfield units for the tissue as well as obscuration of the target and organs at risk (OARs) for radiation therapy planning. Herein we analyze two metal artifact reduction algorithms: GE’s Smart MAR and a Metal Deletion Technique (MDT) for geometric and Hounsfield Unit (HU) accuracy. Methods: A CT-to-electron density phantom, with multiple inserts of various densities and a custom Cerrobend insert (Zeff=76.8), is utilized in this continuing study. The phantom is scanned without metal (baseline) and again with the metal insert. Using one set of projection data, reconstructed CT volumes are created with filtered-back-projection (FBP) and the MAR and the MDT algorithms. Regions-of-Interest (ROIs) are evaluated for each insert for HU accuracy; the metal insert’s Full-Width-Half-Maximum (FWHM) is used to evaluate the geometric accuracy. Streak severity is quantified with an HU error metric over the phantom volume. Results: The original FBP reconstruction has a Root-Mean-Square-Error (RMSE) of 57.55 HU (STD=29.19, range=−145.8 to +79.2) compared to baseline. The MAR reconstruction has a RMSE of 20.98 HU (STD=13.92, range=−18.3 to +61.7). The MDT reconstruction has a RMSE of 10.05 HU (STD=10.5, range=−14.8 to +18.6). FWHM for baseline=162.05; FBP=161.84 (−0.13%); MAR=162.36 (+0.19%); MDT=162.99 (+0.58%). Streak severity metric for FBP=19.73 (22.659% bad pixels); MAR=8.743 (9.538% bad); MDT=4.899 (5.303% bad). Conclusion: Image quality, in terms of HU accuracy, in the presence of high-Z metal objects in CT scans is improved by metal artifact reduction reconstruction algorithms. The MDT algorithm had the highest HU value accuracy (RMSE=10.05 HU) and best streak severity metric, but scored the worst in terms of geometric accuracy. Qualitatively, the MAR and MDT algorithms increased detectability of inserts

  18. SU-E-I-75: Evaluation of An Orthopedic Metal Artifact Reduction (O-MAR) Algorithm On Patients with Spinal Prostheses Near Spinal Tumors

    International Nuclear Information System (INIS)

    Shen, Z; Xia, P; Djemil, T; Klahr, P

    2014-01-01

    Purpose: To evaluate the impact of a commercial orthopedic metal artifact reduction (O-MAR) algorithm on CT image quality and dose calculation for patients with spinal prostheses near spinal tumors. Methods: A CT electron density phantom was scanned twice: with tissue-simulating inserts only, and with a titanium insert replacing solid water. A patient plan was mapped to the phantom images in two ways: with the titanium inside or outside of the spinal tumor. Pinnacle and Eclipse were used to evaluate the dosimetric effects of O-MAR on 12-bit and 16-bit CT data, respectively. CT images from five patients with spinal prostheses were reconstructed with and without O-MAR. Two observers assessed the image quality improvement from O-MAR. Both pencil beam and Monte Carlo dose calculation in iPlan were used for the patient study. The percentage differences between non-OMAR and O-MAR datasets were calculated for PTV-min, PTV-max, PTV-mean, PTV-V100, PTV-D90, OAR-V10Gy, OAR-max, and OAR-D0.1cc. Results: O-MAR improved image quality but did not significantly affect the dose distributions and DVHs for both 12-bit and 16- bit CT phantom data. All five patient cases demonstrated some degree of image quality improvement from O-MAR, ranging from small to large metal artifact reduction. For pencil beam, the largest discrepancy was observed for OARV-10Gy at 5.4%, while the other seven parameters were ≤0.6%. For Monte Carlo, the differences between non-O-MAR and O-MAR datasets were ≤3.0%. Conclusion: Both phantom and patient studies indicated that O-MAR can substantially reduce metal artifacts on CT images, allowing better visualization of the anatomical structures and metal objects. The dosimetric impact of O-MAR was insignificant regardless of the metal location, image bit-depth, and dose calculation algorithm. O-MAR corrected images are recommended for radiation treatment planning on patients with spinal prostheses because of the improved image quality and no need to modify

  19. Artifacts Quantification of Metal Implants in MRI

    Science.gov (United States)

    Vrachnis, I. N.; Vlachopoulos, G. F.; Maris, T. G.; Costaridou, L. I.

    2017-11-01

    The presence of materials with different magnetic properties, such as metal implants, causes distortion of the magnetic field locally, resulting in signal voids and pile ups, i.e. susceptibility artifacts in MRI. Quantitative and unbiased measurement of the artifact is prerequisite for optimization of acquisition parameters. In this study an image gradient based segmentation method is proposed for susceptibility artifact quantification. The method captures abrupt signal alterations by calculation of the image gradient. Then the artifact is quantified in terms of its extent by an automated cross entropy thresholding method as image area percentage. The proposed method for artifact quantification was tested in phantoms containing two orthopedic implants with significantly different magnetic permeabilities. The method was compared against a method proposed in the literature, considered as a reference, demonstrating moderate to good correlation (Spearman’s rho = 0.62 and 0.802 in case of titanium and stainless steel implants). The automated character of the proposed quantification method seems promising towards MRI acquisition parameter optimization.

  20. Metallic artifacts in magnetic resonance imaging

    International Nuclear Information System (INIS)

    Abe, Eiji; Okuyama, Koichiro; Ishikawa, Noriyuki; Hongo, Michio; Sato, Kozo; Sashi, Ryuji; Ishikawa, Eijiro.

    1995-01-01

    Seven metallic implants with different content of magnetic materials were compared in terms of the degree of MRI artifact. The degree of artifact well correlated with the total content of iron and cobalt than the total content of ferromagnets (iron, cobalt, nickel). No significant difference was observed regarding artifact among 4 titanium alloys containing very small amount of ferromagnet (0.058%-2.5%). Pedicle screws were made from different alloys in the same shape. Those screws were inserted into the swine vertebrae and artifact was evaluated by MRI. The degree of artifact was SUS316 (stainless steel)>MP-35N (cobalt alloy)>Ti-6AI-4V (titanium alloy), 1.5 Tesla>0.5 Tesla as for magnetic intensity, and T2 (gradient echo)>T2 (long SE)>proton density>T1 as for exposure condition. The condition of the site screw was inserted in the vertebral canal was detectable by T1-weighted images of titanium alloy and cobalt alloy in 0.5 Tesla and T1-weighted images of titanium alloy in 1.5 Tesla. (S.Y)

  1. Improved Image Quality in Head and Neck CT Using a 3D Iterative Approach to Reduce Metal Artifact.

    Science.gov (United States)

    Wuest, W; May, M S; Brand, M; Bayerl, N; Krauss, A; Uder, M; Lell, M

    2015-10-01

    Metal artifacts from dental fillings and other devices degrade image quality and may compromise the detection and evaluation of lesions in the oral cavity and oropharynx by CT. The aim of this study was to evaluate the effect of iterative metal artifact reduction on CT of the oral cavity and oropharynx. Data from 50 consecutive patients with metal artifacts from dental hardware were reconstructed with standard filtered back-projection, linear interpolation metal artifact reduction (LIMAR), and iterative metal artifact reduction. The image quality of sections that contained metal was analyzed for the severity of artifacts and diagnostic value. A total of 455 sections (mean ± standard deviation, 9.1 ± 4.1 sections per patient) contained metal and were evaluated with each reconstruction method. Sections without metal were not affected by the algorithms and demonstrated image quality identical to each other. Of these sections, 38% were considered nondiagnostic with filtered back-projection, 31% with LIMAR, and only 7% with iterative metal artifact reduction. Thirty-three percent of the sections had poor image quality with filtered back-projection, 46% with LIMAR, and 10% with iterative metal artifact reduction. Thirteen percent of the sections with filtered back-projection, 17% with LIMAR, and 22% with iterative metal artifact reduction were of moderate image quality, 16% of the sections with filtered back-projection, 5% with LIMAR, and 30% with iterative metal artifact reduction were of good image quality, and 1% of the sections with LIMAR and 31% with iterative metal artifact reduction were of excellent image quality. Iterative metal artifact reduction yields the highest image quality in comparison with filtered back-projection and linear interpolation metal artifact reduction in patients with metal hardware in the head and neck area. © 2015 by American Journal of Neuroradiology.

  2. Low-dose CT imaging of a total hip arthroplasty phantom using model-based iterative reconstruction and orthopedic metal artifact reduction

    Energy Technology Data Exchange (ETDEWEB)

    Wellenberg, R.H.H.; Streekstra, G.J.; Maas, M. [Academic Medical Center, Department of Radiology, Amsterdam (Netherlands); Boomsma, M.F.; Osch, J.A.C. van [Department of Radiology, Zwolle (Netherlands); Vlassenbroek, A. [Philips Medical Systems, Brussels (Belgium); Milles, J. [Philips Medical Systems, Eindhoven (Netherlands); Edens, M.A. [Department of Innovation and Science, Zwolle (Netherlands); Slump, C.H. [University of Twente, MIRA Institute for Biomedical Technology and Technical Medicine, Enschede (Netherlands)

    2017-05-15

    To compare quantitative measures of image quality, in terms of CT number accuracy, noise, signal-to-noise-ratios (SNRs), and contrast-to-noise ratios (CNRs), at different dose levels with filtered-back-projection (FBP), iterative reconstruction (IR), and model-based iterative reconstruction (MBIR) alone and in combination with orthopedic metal artifact reduction (O-MAR) in a total hip arthroplasty (THA) phantom. Scans were acquired from high- to low-dose (CTDI{sub vol}: 40.0, 32.0, 24.0, 16.0, 8.0, and 4.0 mGy) at 120- and 140- kVp. Images were reconstructed using FBP, IR (iDose{sup 4} level 2, 4, and 6) and MBIR (IMR, level 1, 2, and 3) with and without O-MAR. CT number accuracy in Hounsfield Units (HU), noise or standard deviation, SNRs, and CNRs were analyzed. The IMR technique showed lower noise levels (p < 0.01), higher SNRs (p < 0.001) and CNRs (p < 0.001) compared with FBP and iDose{sup 4} in all acquisitions from high- to low-dose with constant CT numbers. O-MAR reduced noise (p < 0.01) and improved SNRs (p < 0.01) and CNRs (p < 0.001) while improving CT number accuracy only at a low dose. At the low dose of 4.0 mGy, IMR level 1, 2, and 3 showed 83%, 89%, and 95% lower noise values, a factor 6.0, 9.2, and 17.9 higher SNRs, and 5.7, 8.8, and 18.2 higher CNRs compared with FBP respectively. Based on quantitative analysis of CT number accuracy, noise values, SNRs, and CNRs, we conclude that the combined use of IMR and O-MAR enables a reduction in radiation dose of 83% compared with FBP and iDose{sup 4} in the CT imaging of a THA phantom. (orig.)

  3. Metallic artifact in MRI after removal of orthopedic implants

    International Nuclear Information System (INIS)

    Bagheri, Mohammad Hadi; Hosseini, Mehrdad Mohammad; Emami, Mohammad Jafar; Foroughi, Amin Aiboulhassani

    2012-01-01

    Objective: The aim of the present study was to evaluate the metallic artifacts in MRI of the orthopedic patients after removal of metallic implants. Subjects and methods: From March to August 2009, 40 orthopedic patients operated for removal of orthopedic metallic implants were studied by post-operative MRI from the site of removal of implants. A grading scale of 0–3 was assigned for artifact in MR images whereby 0 was considered no artifact; and I–III were considered mild, moderate, and severe metallic artifacts, respectively. These grading records were correlated with other variables including the type, size, number, and composition of metallic devices; and the site and duration of orthopedic devices stay in the body. Results: Metallic susceptibly artifacts were detected in MRI of 18 of 40 cases (45%). Screws and pins in removed hardware were the most important factors for causing artifacts in MRI. The artifacts were found more frequently in the patients who had more screws and pins in the removed implants. Gender, age, site of implantation of the device, length of the hardware, composition of the metallic implants (stainless steel versus titanium), and duration of implantation of the hardware exerted no effect in producing metallic artifacts after removal of implants. Short TE sequences of MRI (such as T1 weighted) showed fewer artifacts. Conclusion: Susceptibility of metallic artifacts is a frequent phenomenon in MRI of patients upon removal of metallic orthopedic implants.

  4. Metallic artifact in MRI after removal of orthopedic implants.

    Science.gov (United States)

    Bagheri, Mohammad Hadi; Hosseini, Mehrdad Mohammad; Emami, Mohammad Jafar; Foroughi, Amin Aiboulhassani

    2012-03-01

    The aim of the present study was to evaluate the metallic artifacts in MRI of the orthopedic patients after removal of metallic implants. From March to August 2009, 40 orthopedic patients operated for removal of orthopedic metallic implants were studied by post-operative MRI from the site of removal of implants. A grading scale of 0-3 was assigned for artifact in MR images whereby 0 was considered no artifact; and I-III were considered mild, moderate, and severe metallic artifacts, respectively. These grading records were correlated with other variables including the type, size, number, and composition of metallic devices; and the site and duration of orthopedic devices stay in the body. Metallic susceptibly artifacts were detected in MRI of 18 of 40 cases (45%). Screws and pins in removed hardware were the most important factors for causing artifacts in MRI. The artifacts were found more frequently in the patients who had more screws and pins in the removed implants. Gender, age, site of implantation of the device, length of the hardware, composition of the metallic implants (stainless steel versus titanium), and duration of implantation of the hardware exerted no effect in producing metallic artifacts after removal of implants. Short TE sequences of MRI (such as T1 weighted) showed fewer artifacts. Susceptibility of metallic artifacts is a frequent phenomenon in MRI of patients upon removal of metallic orthopedic implants. Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.

  5. Reduction of dark-band-like metal artifacts caused by dental implant bodies using hypothetical monoenergetic imaging after dual-energy computed tomography.

    Science.gov (United States)

    Tanaka, Ray; Hayashi, Takafumi; Ike, Makiko; Noto, Yoshiyuki; Goto, Tazuko K

    2013-06-01

    The aim of this study was to evaluate the usefulness of hypothetical monoenergetic images after dual-energy computed tomography (DECT) for assessment of the bone encircling dental implant bodies. Seventy-two axial images of implantation sites clipped out from image data scanned using DECT in dual-energy mode were used. Subjective assessment on reduction of dark-band-like artifacts (R-DBAs) and diagnosability of adjacent bone condition (D-ABC) in 3 sets of DECT images-a fused image set (DE120) and 2 sets of hypothetical monoenergetic images (ME100, ME190)-was performed and the results were statistically analyzed. With regards to R-DBAs and D-ABC, significant differences among DE120, ME100, and ME190 were observed. The ME100 and ME190 images revealed more artifact reduction and diagnosability than those of DE120. DECT imaging followed by hypothetical monoenergetic image construction can cause R-DBAs and increase D-ABC and may be potentially used for the evaluation of postoperative changes in the bone encircling implant bodies. Copyright © 2013 Elsevier Inc. All rights reserved.

  6. Metal Artifact Suppression in Dental Cone Beam Computed Tomography Images Using Image Processing Techniques.

    Science.gov (United States)

    Johari, Masoumeh; Abdollahzadeh, Milad; Esmaeili, Farzad; Sakhamanesh, Vahideh

    2018-01-01

    Dental cone beam computed tomography (CBCT) images suffer from severe metal artifacts. These artifacts degrade the quality of acquired image and in some cases make it unsuitable to use. Streaking artifacts and cavities around teeth are the main reason of degradation. In this article, we have proposed a new artifact reduction algorithm which has three parallel components. The first component extracts teeth based on the modeling of image histogram with a Gaussian mixture model. Striking artifact reduction component reduces artifacts using converting image into the polar domain and applying morphological filtering. The third component fills cavities through a simple but effective morphological filtering operation. Finally, results of these three components are combined into a fusion step to create a visually good image which is more compatible to human visual system. Results show that the proposed algorithm reduces artifacts of dental CBCT images and produces clean images.

  7. An illustrative review to understand and manage metal-induced artifacts in musculoskeletal MRI: a primer and updates

    Energy Technology Data Exchange (ETDEWEB)

    Dillenseger, J.P.; Choquet, P.; Goetz, C.; Bierry, G. [University Hospital of Strasbourg, Medical Imaging Department, Strasbourg (France); Icube, CNRS, University of Strasbourg, Strasbourg (France); University of Strasbourg, Translational Medicine Research Federation, Strasbourg Medical School, Strasbourg (France); Moliere, S. [University Hospital of Strasbourg, Medical Imaging Department, Strasbourg (France); Ehlinger, M. [Icube, CNRS, University of Strasbourg, Strasbourg (France); University of Strasbourg, Translational Medicine Research Federation, Strasbourg Medical School, Strasbourg (France); University Hospital of Strasbourg, Department of Orthopedic Surgery, Strasbourg (France)

    2016-05-15

    This article reviews and explains the basic physical principles of metal-induced MRI artifacts, describes simple ways to reduce them, and presents specific reduction solutions. Artifacts include signal loss, pile-up artifacts, geometric distortion, and failure of fat suppression. Their nature and origins are reviewed and explained though schematic representations that ease the understanding. Then, optimization of simple acquisition parameters is detailed. Lastly, dedicated sequences and options specifically developed to reduce metal artifacts (VAT, SEMAC, and MAVRIC) are explained. (orig.)

  8. Reduction of variable-truncation artifacts from beam occlusion during in situ x-ray tomography

    DEFF Research Database (Denmark)

    Borg, Leise; Jørgensen, Jakob Sauer; Frikel, Jürgen

    2017-01-01

    Many in situ x-ray tomography studies require experimental rigs which may partially occlude the beam and cause parts of the projection data to be missing. In a study of fluid flow in porous chalk using a percolation cell with four metal bars drastic streak artifacts arise in the filtered...... and artifact-reduction methods are designed in context of FBP reconstruction motivated by computational efficiency practical for large, real synchrotron data. While a specific variable-truncation case is considered, the proposed methods can be applied to general data cut-offs arising in different in situ x-ray...... backprojection (FBP) reconstruction at certain orientations. Projections with non-trivial variable truncation caused by the metal bars are the source of these variable-truncation artifacts. To understand the artifacts a mathematical model of variable-truncation data as a function of metal bar radius and distance...

  9. SU-G-IeP2-03: Comparison of Dose Calculation On MAR (metal Artifact Reduction) and Non-MAR Datasets for Pelvic Patients with Hip Prosthesis and Head and Neck Patients with Dental Filling

    International Nuclear Information System (INIS)

    Huang, V; Kohli, K

    2016-01-01

    Purpose: Metal artifact reduction (MAR) software in computed tomography (CT) was previously evaluated with phantoms demonstrating the algorithm is capable of reducing metal artifacts without affecting the overall image quality. The goal of this study is to determine the dosimetric impact when calculating with CT datasets reconstructed with and without MAR software. Methods: Twelve head and neck cancer patients with dental fillings and four pelvic cancer patients with hip prosthesis were scanned with a GE Optima RT 580 CT scanner. Images were reconstructed with and without the MAR software. 6MV IMRT and VMAT plans were calculated with AAA on the MAR dataset until all constraints met our clinic’s guidelines. Contours from the MAR dataset were copied to the non-MAR dataset. Next, dose calculation on the non-MAR dataset was performed using the same field arrangements and fluence as the MAR plan. Conformality index, D99% and V100% to PTV were compared between MAR and non-MAR plans. Results: Differences between MAR and non-MAR plans were evaluated. For head and neck plans, the largest variations in conformality index, D99% and V100% were −3.8%, −0.9% and −2.1% respectively whereas for pelvic plans, the biggest discrepancies were −32.7%, −0.4% and -33.5% respectively. The dosimetric impact from hip prosthesis is greater because it produces more artifacts compared to dental fillings. Coverage to PTV can increase or decrease depending on the artifacts since dark streaks reduce the HU whereas bright streaks increase the HU. In the majority of the cases, PTV dose in the non-MAR plans is higher than MAR plans. Conclusion: With the presence of metals, MAR algorithm can allow more accurate delineation of targets and OARs. Dose difference between MAR and non-MAR plans depends on the proximity of the organ to the high density material, the streaking artifacts and the beam arrangements of the plan.

  10. SU-G-IeP2-03: Comparison of Dose Calculation On MAR (metal Artifact Reduction) and Non-MAR Datasets for Pelvic Patients with Hip Prosthesis and Head and Neck Patients with Dental Filling

    Energy Technology Data Exchange (ETDEWEB)

    Huang, V; Kohli, K [BC Cancer Agency, Surrey, BC (United Kingdom)

    2016-06-15

    Purpose: Metal artifact reduction (MAR) software in computed tomography (CT) was previously evaluated with phantoms demonstrating the algorithm is capable of reducing metal artifacts without affecting the overall image quality. The goal of this study is to determine the dosimetric impact when calculating with CT datasets reconstructed with and without MAR software. Methods: Twelve head and neck cancer patients with dental fillings and four pelvic cancer patients with hip prosthesis were scanned with a GE Optima RT 580 CT scanner. Images were reconstructed with and without the MAR software. 6MV IMRT and VMAT plans were calculated with AAA on the MAR dataset until all constraints met our clinic’s guidelines. Contours from the MAR dataset were copied to the non-MAR dataset. Next, dose calculation on the non-MAR dataset was performed using the same field arrangements and fluence as the MAR plan. Conformality index, D99% and V100% to PTV were compared between MAR and non-MAR plans. Results: Differences between MAR and non-MAR plans were evaluated. For head and neck plans, the largest variations in conformality index, D99% and V100% were −3.8%, −0.9% and −2.1% respectively whereas for pelvic plans, the biggest discrepancies were −32.7%, −0.4% and -33.5% respectively. The dosimetric impact from hip prosthesis is greater because it produces more artifacts compared to dental fillings. Coverage to PTV can increase or decrease depending on the artifacts since dark streaks reduce the HU whereas bright streaks increase the HU. In the majority of the cases, PTV dose in the non-MAR plans is higher than MAR plans. Conclusion: With the presence of metals, MAR algorithm can allow more accurate delineation of targets and OARs. Dose difference between MAR and non-MAR plans depends on the proximity of the organ to the high density material, the streaking artifacts and the beam arrangements of the plan.

  11. Reduction of variable-truncation artifacts from beam occlusion during in situ x-ray tomography

    Science.gov (United States)

    Borg, Leise; Jørgensen, Jakob S.; Frikel, Jürgen; Sporring, Jon

    2017-12-01

    Many in situ x-ray tomography studies require experimental rigs which may partially occlude the beam and cause parts of the projection data to be missing. In a study of fluid flow in porous chalk using a percolation cell with four metal bars drastic streak artifacts arise in the filtered backprojection (FBP) reconstruction at certain orientations. Projections with non-trivial variable truncation caused by the metal bars are the source of these variable-truncation artifacts. To understand the artifacts a mathematical model of variable-truncation data as a function of metal bar radius and distance to sample is derived and verified numerically and with experimental data. The model accurately describes the arising variable-truncation artifacts across simulated variations of the experimental setup. Three variable-truncation artifact-reduction methods are proposed, all aimed at addressing sinogram discontinuities that are shown to be the source of the streaks. The ‘reduction to limited angle’ (RLA) method simply keeps only non-truncated projections; the ‘detector-directed smoothing’ (DDS) method smooths the discontinuities; while the ‘reflexive boundary condition’ (RBC) method enforces a zero derivative at the discontinuities. Experimental results using both simulated and real data show that the proposed methods effectively reduce variable-truncation artifacts. The RBC method is found to provide the best artifact reduction and preservation of image features using both visual and quantitative assessment. The analysis and artifact-reduction methods are designed in context of FBP reconstruction motivated by computational efficiency practical for large, real synchrotron data. While a specific variable-truncation case is considered, the proposed methods can be applied to general data cut-offs arising in different in situ x-ray tomography experiments.

  12. SU-F-T-407: Artifact Reduction with Dual Energy Or IMAR: Who’s Winning?

    International Nuclear Information System (INIS)

    Elder, E; Schreibmann, E; Dhabaan, A

    2016-01-01

    Purpose: The purpose of this abstract was to evaluate the performance of commercial strategies for artifact reduction in radiation oncology settings. The iterative metal artifact reduction (Siemens iMAR) algorithm and monoenergetic virtual datasets reconstructed from dual energy scans are compared side-by-side in their ability to image in the presence of metal inserts. Methods: A CIRS ATOM Dosimetry Verification Phantom was scanned with and without a metal insert on a SOMATOM Definition AS dual energy scanner. Images with the metal insert were reconstructed with (a) a tradition single energy CT scan with the iMAR option implemented, using different artifact reduction settings and (b) a monoenergetic scan calculated from dual energy scans by recovering differences in the energy-dependence of the attenuation coefficients of different materials and then creating a virtual monoenergetic scan from these coefficients. The iMAR and monoenergetic scans were then compared with the metal-free scan to assess changes in HU numbers and noise within a region around the metal insert. Results: Both the iMAR and dual energy scans reduced artifacts produced by the metal insert. However the iMAR results are dependent of the selected algorithm settings, with a mean HU difference ranging from 0.65 to 90.40 for different options. The mean differences without the iMAR correction were 38.74. When using the dual energy scan, the mean differences were 4.53, that is however attributed to increased noise and not artifacts, as the dual energy scan had the lowest skewness (2.52) compared to the iMAR scans (ranging from 3.90 to 4.88) and the lowest kurtosis (5.72 for dual energy, range of 18.19 to 27.36 for iMAR). Conclusion: Both approaches accurately recovered HU numbers, however the dual energy method provided smaller residual artifacts.

  13. SU-F-T-407: Artifact Reduction with Dual Energy Or IMAR: Who’s Winning?

    Energy Technology Data Exchange (ETDEWEB)

    Elder, E; Schreibmann, E; Dhabaan, A [Department of Radiation Oncology and Winship Cancer Institute of Emory University Atlanta, GA (United States)

    2016-06-15

    Purpose: The purpose of this abstract was to evaluate the performance of commercial strategies for artifact reduction in radiation oncology settings. The iterative metal artifact reduction (Siemens iMAR) algorithm and monoenergetic virtual datasets reconstructed from dual energy scans are compared side-by-side in their ability to image in the presence of metal inserts. Methods: A CIRS ATOM Dosimetry Verification Phantom was scanned with and without a metal insert on a SOMATOM Definition AS dual energy scanner. Images with the metal insert were reconstructed with (a) a tradition single energy CT scan with the iMAR option implemented, using different artifact reduction settings and (b) a monoenergetic scan calculated from dual energy scans by recovering differences in the energy-dependence of the attenuation coefficients of different materials and then creating a virtual monoenergetic scan from these coefficients. The iMAR and monoenergetic scans were then compared with the metal-free scan to assess changes in HU numbers and noise within a region around the metal insert. Results: Both the iMAR and dual energy scans reduced artifacts produced by the metal insert. However the iMAR results are dependent of the selected algorithm settings, with a mean HU difference ranging from 0.65 to 90.40 for different options. The mean differences without the iMAR correction were 38.74. When using the dual energy scan, the mean differences were 4.53, that is however attributed to increased noise and not artifacts, as the dual energy scan had the lowest skewness (2.52) compared to the iMAR scans (ranging from 3.90 to 4.88) and the lowest kurtosis (5.72 for dual energy, range of 18.19 to 27.36 for iMAR). Conclusion: Both approaches accurately recovered HU numbers, however the dual energy method provided smaller residual artifacts.

  14. Evaluation of a metal artifact reduction algorithm applied to post-interventional flat detector CT in comparison to pre-treatment CT in patients with acute subarachnoid haemorrhage

    Energy Technology Data Exchange (ETDEWEB)

    Mennecke, Angelika; Svergun, Stanislav; Doerfler, Arnd; Struffert, Tobias [University of Erlangen-Nuremberg, Department of Neuroradiology, Erlangen (Germany); Scholz, Bernhard [Siemens Healthcare GmbH, Forchheim (Germany); Royalty, Kevin [Siemens Medical Solutions, USA, Inc., Hoffman Estates, IL (United States)

    2017-01-15

    Metal artefacts can impair accurate diagnosis of haemorrhage using flat detector CT (FD-CT), especially after aneurysm coiling. Within this work we evaluate a prototype metal artefact reduction algorithm by comparison of the artefact-reduced and the non-artefact-reduced FD-CT images to pre-treatment FD-CT and multi-slice CT images. Twenty-five patients with acute aneurysmal subarachnoid haemorrhage (SAH) were selected retrospectively. FD-CT and multi-slice CT before endovascular treatment as well as FD-CT data sets after treatment were available for all patients. The algorithm was applied to post-treatment FD-CT. The effect of the algorithm was evaluated utilizing the pre-post concordance of a modified Fisher score, a subjective image quality assessment, the range of the Hounsfield units within three ROIs, and the pre-post slice-wise Pearson correlation. The pre-post concordance of the modified Fisher score, the subjective image quality, and the pre-post correlation of the ranges of the Hounsfield units were significantly higher for artefact-reduced than for non-artefact-reduced images. Within the metal-affected slices, the pre-post slice-wise Pearson correlation coefficient was higher for artefact-reduced than for non-artefact-reduced images. The overall diagnostic quality of the artefact-reduced images was improved and reached the level of the pre-interventional FD-CT images. The metal-unaffected parts of the image were not modified. (orig.)

  15. Evaluation of a metal artifact reduction algorithm applied to post-interventional flat detector CT in comparison to pre-treatment CT in patients with acute subarachnoid haemorrhage

    International Nuclear Information System (INIS)

    Mennecke, Angelika; Svergun, Stanislav; Doerfler, Arnd; Struffert, Tobias; Scholz, Bernhard; Royalty, Kevin

    2017-01-01

    Metal artefacts can impair accurate diagnosis of haemorrhage using flat detector CT (FD-CT), especially after aneurysm coiling. Within this work we evaluate a prototype metal artefact reduction algorithm by comparison of the artefact-reduced and the non-artefact-reduced FD-CT images to pre-treatment FD-CT and multi-slice CT images. Twenty-five patients with acute aneurysmal subarachnoid haemorrhage (SAH) were selected retrospectively. FD-CT and multi-slice CT before endovascular treatment as well as FD-CT data sets after treatment were available for all patients. The algorithm was applied to post-treatment FD-CT. The effect of the algorithm was evaluated utilizing the pre-post concordance of a modified Fisher score, a subjective image quality assessment, the range of the Hounsfield units within three ROIs, and the pre-post slice-wise Pearson correlation. The pre-post concordance of the modified Fisher score, the subjective image quality, and the pre-post correlation of the ranges of the Hounsfield units were significantly higher for artefact-reduced than for non-artefact-reduced images. Within the metal-affected slices, the pre-post slice-wise Pearson correlation coefficient was higher for artefact-reduced than for non-artefact-reduced images. The overall diagnostic quality of the artefact-reduced images was improved and reached the level of the pre-interventional FD-CT images. The metal-unaffected parts of the image were not modified. (orig.)

  16. Material-Dependent Implant Artifact Reduction Using SEMAC-VAT and MAVRIC: A Prospective MRI Phantom Study.

    Science.gov (United States)

    Filli, Lukas; Jud, Lukas; Luechinger, Roger; Nanz, Daniel; Andreisek, Gustav; Runge, Val M; Kozerke, Sebastian; Farshad-Amacker, Nadja A

    2017-06-01

    The aim of this study was to compare the degree of artifact reduction in magnetic resonance imaging achieved with slice encoding for metal artifact correction (SEMAC) in combination with view angle tilting (VAT) and multiacquisition variable resonance image combination (MAVRIC) for standard contrast weightings and different metallic materials. Four identically shaped rods made of the most commonly used prosthetic materials (stainless steel, SS; titanium, Ti; cobalt-chromium-molybdenum, CoCr; and oxidized zirconium, oxZi) were scanned at 3 T. In addition to conventional fast spin-echo sequences, metal artifact reduction sequences (SEMAC-VAT and MAVRIC) with varying degrees of artifact suppression were applied at different contrast weightings (T1w, T2w, PDw). Two independent readers measured in-plane and through-plane artifacts in a standardized manner. In addition, theoretical frequency-offset and frequency-offset-gradient maps were calculated. Interobserver agreement was assessed using intraclass correlation coefficient. Interobserver agreement was almost perfect (intraclass correlation coefficient, 0.86-0.99). Stainless steel caused the greatest artifacts, followed by CoCr, Ti, and oxZi regardless of the imaging sequence. While for Ti and oxZi rods scanning with weak SEMAC-VAT showed some advantage, for SS and CoCr, higher modes of SEMAC-VAT or MAVRIC were necessary to achieve artifact reduction. MAVRIC achieved better artifact reduction than SEMAC-VAT at the cost of longer acquisition times. Simulations matched well with the apparent geometry of the frequency-offset maps. For Ti and oxZi implants, weak SEMAC-VAT may be preferred as it is faster and produces less artifact than conventional fast spin-echo. Medium or strong SEMAC-VAT or MAVRIC modes are necessary for significant artifact reduction for SS and CoCr implants.

  17. A study of metal artifacts on MR imaging. Evaluation of scanning parameters

    International Nuclear Information System (INIS)

    Yamashiro, Mitsuaki

    1999-01-01

    The purpose of this study was to evaluate scanning parameters on MR imaging for reducing metal artifacts using phantom study. Metal artifacts on sagittal images, perpendicular to static magnetic direction showed round shape in the relationship between shape of metal artifacts on MR images and scanning direction. Metal artifacts on both axial and coronal images, parallel to static magnetic direction showed oval shape in the direction of X-axis. In spin echo sequences, the largest dimension of metal artifacts was coronal image, followed by axial image and then sagittal image. In gradient echo sequences, the largest dimension of metal artifacts was axial image, followed by coronal image and then sagittal image. The best scanning plane for reducing metal artifacts was perpendicular to static magnetic direction. In scanning sequences, the largest dimensions of metal artifacts were gradient echo sequences, followed by T2-weighted spin echo sequence and then proton density-weighted and T1-weighted spin echo sequences. Large flip angle increased much metal artifacts on both axial and coronal images in gradient echo sequences. Small flip angle was useful for reducing metal artifacts on both axial and coronal images. The influence of flip angle on metal artifacts in sagittal images perpendicular static magnetic direction was less than for images in coronal and axial planes on gradient echo sequences. These results suggested that a study of metal artifacts on MR imaging about evaluation of scanning parameters was useful to reduce metal artifacts on MR images. (K.H.)

  18. MRI-Based Computed Tomography Metal Artifact Correction Method for Improving Proton Range Calculation Accuracy

    International Nuclear Information System (INIS)

    Park, Peter C.; Schreibmann, Eduard; Roper, Justin; Elder, Eric; Crocker, Ian; Fox, Tim; Zhu, X. Ronald; Dong, Lei; Dhabaan, Anees

    2015-01-01

    Purpose: Computed tomography (CT) artifacts can severely degrade dose calculation accuracy in proton therapy. Prompted by the recently increased popularity of magnetic resonance imaging (MRI) in the radiation therapy clinic, we developed an MRI-based CT artifact correction method for improving the accuracy of proton range calculations. Methods and Materials: The proposed method replaces corrupted CT data by mapping CT Hounsfield units (HU number) from a nearby artifact-free slice, using a coregistered MRI. MRI and CT volumetric images were registered with use of 3-dimensional (3D) deformable image registration (DIR). The registration was fine-tuned on a slice-by-slice basis by using 2D DIR. Based on the intensity of paired MRI pixel values and HU from an artifact-free slice, we performed a comprehensive analysis to predict the correct HU for the corrupted region. For a proof-of-concept validation, metal artifacts were simulated on a reference data set. Proton range was calculated using reference, artifactual, and corrected images to quantify the reduction in proton range error. The correction method was applied to 4 unique clinical cases. Results: The correction method resulted in substantial artifact reduction, both quantitatively and qualitatively. On respective simulated brain and head and neck CT images, the mean error was reduced from 495 and 370 HU to 108 and 92 HU after correction. Correspondingly, the absolute mean proton range errors of 2.4 cm and 1.7 cm were reduced to less than 2 mm in both cases. Conclusions: Our MRI-based CT artifact correction method can improve CT image quality and proton range calculation accuracy for patients with severe CT artifacts

  19. Combining monoenergetic extrapolations from dual-energy CT with iterative reconstructions. Reduction of coil and clip artifacts from intracranial aneurysm therapy

    Energy Technology Data Exchange (ETDEWEB)

    Winklhofer, Sebastian; Baltsavias, Gerasimos; Michels, Lars; Valavanis, Antonios [University of Zurich, Department of Neuroradiology, University Hospital Zurich, Zurich (Switzerland); Hinzpeter, Ricarda; Stocker, Daniel; Alkadhi, Hatem [University of Zurich, Institute of Diagnostic and Interventional Radiology, University Hospital Zurich, Zurich (Switzerland); Burkhardt, Jan-Karl; Regli, Luca [University of Zurich, Department of Neurosurgery, University Hospital Zurich, Zurich (Switzerland)

    2018-03-15

    To compare and to combine iterative metal artifact reduction (MAR) and virtual monoenergetic extrapolations (VMEs) from dual-energy computed tomography (DECT) for reducing metal artifacts from intracranial clips and coils. Fourteen clips and six coils were scanned in a phantom model with DECT at 100 and 150SnkVp. Four datasets were reconstructed: non-corrected images (filtered-back projection), iterative MAR, VME from DECT at 120 keV, and combined iterative MAR + VME images. Artifact severity scores and visibility of simulated, contrast-filled, adjacent vessels were assessed qualitatively and quantitatively by two independent, blinded readers. Iterative MAR, VME, and combined iterative MAR + VME resulted in a significant reduction of qualitative (p < 0.001) and quantitative clip artifacts (p < 0.005) and improved the visibility of adjacent vessels (p < 0.05) compared to non-corrected images, with lowest artifact scores found in combined iterative MAR + VME images. Titanium clips demonstrated less artifacts than Phynox clips (p < 0.05), and artifact scores increased with clip size. Coil artifacts increased with coil size but were reducible when applying iterative MAR + VME compared to non-corrected images. However, no technique improved the severe artifacts from large, densely packed coils. Combining iterative MAR with VME allows for an improved metal artifact reduction from clips and smaller, loosely packed coils. Limited value was found for large and densely packed coils. (orig.)

  20. A study on a pedicle-screw-based reduction method for artificially reduced artifacts

    Science.gov (United States)

    Kim, Hyun-Ju; Lee, Hae-Kag; Cho, Jae-Hwan

    2017-09-01

    The purpose of this study is a quantitative analysis of the degree of the reduction of the artifacts that are induced by pedicle screws through the application of the recently developed iterative metallic artifact reduction (I MAR) software. Screw-type implants that are composed of 4.5 g/cm3 titanium (Ti) with an approximate average computed tomography (CT) value of 6500 Hounsfield units (HUs) that are used for the treatment of spinal diseases were placed in paraffin, a tissueequivalent material, and then dried. After the insertion, the scanning conditions were fixed as 120 kVp and 250 mA using multidetector computed tomography (MDCT) (Enlarge, Siemens, Germany). The slice thickness and the increment were set at the fields of view (FOVs) of 3 mm and 120 mm, respectively; the pitch is 0.8; the rotation time is 1 s; and the I MAR software was applied to the raw data of the acquired images to compare the CT-value changes of the posterior images. When the I MAR software was applied to animal vertebrae, it was possible to reduce the 65.7% image loss of the black-hole-effect image through the application of the I MAR software. When the I MAR image loss (%) was compared with the white-streak-effect image, the high-intensity image type with the white-streak effect could be reduced by 91.34% through the application of the I MAR software. In conclusion, a metal artifact that is due to a high-density material can be reduced more effectively when the I MAR algorithm is applied compared with that from the application of the conventional MAR algorithm. The I MAR can provide information on the various tissues that form around the artifact and the reduced metal structures, which can be helpful for radiologists and clinicians in their determination of an accurate diagnosis.

  1. Reference-free ground truth metric for metal artifact evaluation in CT images

    International Nuclear Information System (INIS)

    Kratz, Baerbel; Ens, Svitlana; Mueller, Jan; Buzug, Thorsten M.

    2011-01-01

    Purpose: In computed tomography (CT), metal objects in the region of interest introduce data inconsistencies during acquisition. Reconstructing these data results in an image with star shaped artifacts induced by the metal inconsistencies. To enhance image quality, the influence of the metal objects can be reduced by different metal artifact reduction (MAR) strategies. For an adequate evaluation of new MAR approaches a ground truth reference data set is needed. In technical evaluations, where phantoms can be measured with and without metal inserts, ground truth data can easily be obtained by a second reference data acquisition. Obviously, this is not possible for clinical data. Here, an alternative evaluation method is presented without the need of an additionally acquired reference data set. Methods: The proposed metric is based on an inherent ground truth for metal artifacts as well as MAR methods comparison, where no reference information in terms of a second acquisition is needed. The method is based on the forward projection of a reconstructed image, which is compared to the actually measured projection data. Results: The new evaluation technique is performed on phantom and on clinical CT data with and without MAR. The metric results are then compared with methods using a reference data set as well as an expert-based classification. It is shown that the new approach is an adequate quantification technique for artifact strength in reconstructed metal or MAR CT images. Conclusions: The presented method works solely on the original projection data itself, which yields some advantages compared to distance measures in image domain using two data sets. Beside this, no parameters have to be manually chosen. The new metric is a useful evaluation alternative when no reference data are available.

  2. Evaluation of the reconstruction of image acquired from CT simulator to reduce metal artifact

    International Nuclear Information System (INIS)

    Choi, Ji Hun; Park, Jin Hong; Choi, Byung Don; Won, Hui Su; Chang, Nam Jun; Goo, Jang Hyun; Hong, Joo Wan

    2014-01-01

    This study presents the usefulness assessment of metal artifact reduction for orthopedic implants(O-MAR) to decrease metal artifacts from materials with high density when acquired CT images. By CT simulator, original CT images were acquired from Gammex and Rando phantom and those phantoms inserted with high density materials were scanned for other CT images with metal artifacts and then O-MAR was applied to those images, respectively. To evaluate CT images using Gammex phantom, 5 regions of interest(ROIs) were placed at 5 organs and 3 ROIs were set up at points affected by artifacts. The averages of standard deviation(SD) and CT numbers were compared with a plan using original image. For assessment of variations in dose of tissue around materials with high density, the volume of a cylindrical shape was designed at 3 places in images acquired from Rando phantom by Eclipse. With 6 MV, 7-fields, 15x15cm 2 and 100 cGy per fraction, treatment planning was created and the mean dose were compared with a plan using original image. In the test with the Gammex phantom, CT numbers had a few difference at established points and especially 3 points affected by artifacts had most of the same figures. In the case of O-MAR image, the more reduction in SD appeared at all of 8 points than non O-MAR image. In the test using the Rando Phantom, the variations in dose of tissue around high density materials had a few difference between original CT image and CT image with O-MAR. The CT images using O-MAR were acquired clearly at the boundary of tissue around high density materials and applying O-MAR was useful for correcting CT numbers

  3. Artifacts

    Science.gov (United States)

    Harris, Samantha

    2009-01-01

    NASA Headquarters sent a list of items to KSC that were deemed potential artifacts. These items played arole in the Shuttle Program's development and maintenance. Because these items are national assets, many are of interest to museums, schools, other government entities, etc. upon the Space Shuttle's retirement. The list contains over 500 items. All of these items need to be located, photographed, and catalogued with accompanying specific data that needs to be gathered. Initial research suggests that this is a time, labor, and cost intensive project. The purpose of my project was to focus on 20-60 of these 500 items, gather the necessary data, and compile them in a way that can be added to by other users when/if the project goes into full effect.

  4. Metallic artifact mitigation and organ-constrained tissue assignment for Monte Carlo calculations of permanent implant lung brachytherapy

    Energy Technology Data Exchange (ETDEWEB)

    Sutherland, J. G. H.; Miksys, N.; Thomson, R. M., E-mail: rthomson@physics.carleton.ca [Carleton Laboratory for Radiotherapy Physics, Department of Physics, Carleton University, Ottawa, Ontario K1S 5B6 (Canada); Furutani, K. M. [Department of Radiation Oncology, Mayo Clinic College of Medicine, Rochester, Minnesota 55905 (United States)

    2014-01-15

    Purpose: To investigate methods of generating accurate patient-specific computational phantoms for the Monte Carlo calculation of lung brachytherapy patient dose distributions. Methods: Four metallic artifact mitigation methods are applied to six lung brachytherapy patient computed tomography (CT) images: simple threshold replacement (STR) identifies high CT values in the vicinity of the seeds and replaces them with estimated true values; fan beam virtual sinogram replaces artifact-affected values in a virtual sinogram and performs a filtered back-projection to generate a corrected image; 3D median filter replaces voxel values that differ from the median value in a region of interest surrounding the voxel and then applies a second filter to reduce noise; and a combination of fan beam virtual sinogram and STR. Computational phantoms are generated from artifact-corrected and uncorrected images using several tissue assignment schemes: both lung-contour constrained and unconstrained global schemes are considered. Voxel mass densities are assigned based on voxel CT number or using the nominal tissue mass densities. Dose distributions are calculated using the EGSnrc user-code BrachyDose for{sup 125}I, {sup 103}Pd, and {sup 131}Cs seeds and are compared directly as well as through dose volume histograms and dose metrics for target volumes surrounding surgical sutures. Results: Metallic artifact mitigation techniques vary in ability to reduce artifacts while preserving tissue detail. Notably, images corrected with the fan beam virtual sinogram have reduced artifacts but residual artifacts near sources remain requiring additional use of STR; the 3D median filter removes artifacts but simultaneously removes detail in lung and bone. Doses vary considerably between computational phantoms with the largest differences arising from artifact-affected voxels assigned to bone in the vicinity of the seeds. Consequently, when metallic artifact reduction and constrained tissue

  5. 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.

  6. Artifact reduction of compressed images and video combining adaptive fuzzy filtering and directional anisotropic diffusion

    DEFF Research Database (Denmark)

    Nadernejad, Ehsan; Forchhammer, Søren; Korhonen, Jari

    2011-01-01

    and ringing artifacts, we have applied directional anisotropic diffusion. Besides that, the selection of the adaptive threshold parameter for the diffusion coefficient has also improved the performance of the algorithm. Experimental results on JPEG compressed images as well as MJPEG and H.264 compressed......Fuzzy filtering is one of the recently developed methods for reducing distortion in compressed images and video. In this paper, we combine the powerful anisotropic diffusion equations with fuzzy filtering in order to reduce the impact of artifacts. Based on the directional nature of the blocking...... videos show improvement in artifact reduction of the proposed algorithm over other directional and spatial fuzzy filters....

  7. SU-F-I-08: CT Image Ring Artifact Reduction Based On Prior Image

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, C; Qi, H; Chen, Z; Wu, S; Xu, Y; Zhou, L [Southern Medical University, Guangzhou, Guangdong (China)

    2016-06-15

    Purpose: In computed tomography (CT) system, CT images with ring artifacts will be reconstructed when some adjacent bins of detector don’t work. The ring artifacts severely degrade CT image quality. We present a useful CT ring artifacts reduction based on projection data correction, aiming at estimating the missing data of projection data accurately, thus removing the ring artifacts of CT images. Methods: The method consists of ten steps: 1) Identification of abnormal pixel line in projection sinogram; 2) Linear interpolation within the pixel line of projection sinogram; 3) FBP reconstruction using interpolated projection data; 4) Filtering FBP image using mean filter; 5) Forwarding projection of filtered FBP image; 6) Subtraction forwarded projection from original projection; 7) Linear interpolation of abnormal pixel line area in the subtraction projection; 8) Adding the interpolated subtraction projection on the forwarded projection; 9) FBP reconstruction using corrected projection data; 10) Return to step 4 until the pre-set iteration number is reached. The method is validated on simulated and real data to restore missing projection data and reconstruct ring artifact-free CT images. Results: We have studied impact of amount of dead bins of CT detector on the accuracy of missing data estimation in projection sinogram. For the simulated case with a resolution of 256 by 256 Shepp-Logan phantom, three iterations are sufficient to restore projection data and reconstruct ring artifact-free images when the dead bins rating is under 30%. The dead-bin-induced artifacts are substantially reduced. More iteration number is needed to reconstruct satisfactory images while the rating of dead bins increases. Similar results were found for a real head phantom case. Conclusion: A practical CT image ring artifact correction scheme based on projection data is developed. This method can produce ring artifact-free CT images feasibly and effectively.

  8. SU-F-I-08: CT Image Ring Artifact Reduction Based On Prior Image

    International Nuclear Information System (INIS)

    Yuan, C; Qi, H; Chen, Z; Wu, S; Xu, Y; Zhou, L

    2016-01-01

    Purpose: In computed tomography (CT) system, CT images with ring artifacts will be reconstructed when some adjacent bins of detector don’t work. The ring artifacts severely degrade CT image quality. We present a useful CT ring artifacts reduction based on projection data correction, aiming at estimating the missing data of projection data accurately, thus removing the ring artifacts of CT images. Methods: The method consists of ten steps: 1) Identification of abnormal pixel line in projection sinogram; 2) Linear interpolation within the pixel line of projection sinogram; 3) FBP reconstruction using interpolated projection data; 4) Filtering FBP image using mean filter; 5) Forwarding projection of filtered FBP image; 6) Subtraction forwarded projection from original projection; 7) Linear interpolation of abnormal pixel line area in the subtraction projection; 8) Adding the interpolated subtraction projection on the forwarded projection; 9) FBP reconstruction using corrected projection data; 10) Return to step 4 until the pre-set iteration number is reached. The method is validated on simulated and real data to restore missing projection data and reconstruct ring artifact-free CT images. Results: We have studied impact of amount of dead bins of CT detector on the accuracy of missing data estimation in projection sinogram. For the simulated case with a resolution of 256 by 256 Shepp-Logan phantom, three iterations are sufficient to restore projection data and reconstruct ring artifact-free images when the dead bins rating is under 30%. The dead-bin-induced artifacts are substantially reduced. More iteration number is needed to reconstruct satisfactory images while the rating of dead bins increases. Similar results were found for a real head phantom case. Conclusion: A practical CT image ring artifact correction scheme based on projection data is developed. This method can produce ring artifact-free CT images feasibly and effectively.

  9. Quantitative evaluation of photoplethysmographic artifact reduction for pulse oximetry

    Science.gov (United States)

    Hayes, Matthew J.; Smith, Peter R.

    1999-01-01

    Motion artefact corruption of pulse oximeter output, causing both measurement inaccuracies and false alarm conditions, is a primary restriction in the current clinical practice and future applications of this useful technique. Artefact reduction in photoplethysmography (PPG), and therefore by application in pulse oximetry, is demonstrated using a novel non-linear methodology recently proposed by the authors. The significance of these processed PPG signals for pulse oximetry measurement is discussed, with particular attention to the normalization inherent in the artefact reduction process. Quantitative experimental investigation of the performance of PPG artefact reduction is then utilized to evaluate this technology for application to pulse oximetry. While the successfully demonstrated reduction of severe artefacts may widen the applicability of all PPG technologies and decrease the occurrence of pulse oximeter false alarms, the observed reduction of slight artefacts suggests that many such effects may go unnoticed in clinical practice. The signal processing and output averaging used in most commercial oximeters can incorporate these artefact errors into the output, while masking the true PPG signal corruption. It is therefore suggested that PPG artefact reduction should be incorporated into conventional pulse oximetry measurement, even in the absence of end-user artefact problems.

  10. Periprosthetic Artifact Reduction Using Virtual Monochromatic Imaging Derived From Gemstone Dual-Energy Computed Tomography and Dedicated Software.

    Science.gov (United States)

    Reynoso, Exequiel; Capunay, Carlos; Rasumoff, Alejandro; Vallejos, Javier; Carpio, Jimena; Lago, Karen; Carrascosa, Patricia

    2016-01-01

    The aim of this study was to explore the usefulness of combined virtual monochromatic imaging and metal artifact reduction software (MARS) for the evaluation of musculoskeletal periprosthetic tissue. Measurements were performed in periprosthetic and remote regions in 80 patients using a high-definition scanner. Polychromatic images with and without MARS and virtual monochromatic images were obtained. Periprosthetic polychromatic imaging (PI) showed significant differences compared with remote areas among the 3 tissues explored (P remote tissues using monochromatic imaging with MARS (P = 0.053 bone, P = 0.32 soft tissue, and P = 0.13 fat). However, such differences were significant using PI with MARS among bone (P = 0.005) and fat (P = 0.02) tissues. All periprosthetic areas were noninterpretable using PI, compared with 11 (9%) using monochromatic imaging. The combined use of virtual monochromatic imaging and MARS reduced periprosthetic artifacts, achieving attenuation levels comparable to implant-free tissue.

  11. Evaluation of the effects of an arm artifact reduction filter in computed tomography

    International Nuclear Information System (INIS)

    Nozaki, Fumie; Ohno, Hajime; Hirako, Tetsuya

    2002-01-01

    While performing CT during arterial portography (CTAP) or CT arteriography (CTA), we have instructed patients to in order to reduce streak artifacts. However the repetitive raising and lowering their arms has made it difficult to keep a clean zone and as well as to maintain the position of a target organ. An arm artifact reduction (AAR) filter developed by GE Yokokawa Medical System has been reported to be useful for reducing streak artifacts in CTAP and CTA. The purpose of this study was to estimate the effectiveness of the AAR filter in terms of artifact reduction ratio, CT value, standard deviation and spatial resolution. The use of an AAR filter reduced streak artifacts on images by 15-22% compared with those on images obtained by without the use of the filter and limited deterioration of spatial resolution to within 1%. Moreover, CT value in examination using AAR filter showed no significant change compared with that in non-filter's examination. It is concluded that the use of an AAR filter reduces the burden for the patient and increase the accuracy and flexibility of CT examination while minimizing the reduction in the image quality in CTAP and CTA. (author)

  12. Magnetic resonance imaging metallic artifact of commonly encountered surgical implants and foreign material.

    Science.gov (United States)

    Sutherland-Smith, James; Tilley, Brenda

    2012-01-01

    Magnetic resonance imaging (MRI) artifacts secondary to metallic implants and foreign bodies are well described. Herein, we provide quantitative data from veterinary implants including total hip arthroplasty implants, cranial cruciate repair implants, surgical screws, a skin staple, ligation clips, an identification microchip, ameroid constrictor, and potential foreign bodies including air gun and BB projectiles and a sewing needle. The objects were scanned in a gelatin phantom with plastic grid using standardized T2-weighted turbo-spin echo (TSE), T1-weighted spin echo, and T2*-weighted gradient recalled echo (GRE) image acquisitions at 1.5 T. Maximum linear dimensions and areas of signal voiding and grid distortion were calculated using a DICOM workstation for each sequence and object. Artifact severity was similar between the T2-weighted TSE and T1-weighted images, while the T2*-weighted images were most susceptible to artifact. Metal type influenced artifact size with the largest artifacts arising from steel objects followed by surgical stainless steel, titanium, and lead. For animals with metallic surgical implants or foreign bodies, the quantification of the artifact size will help guide clinicians on the viability of MRI. © 2012 Veterinary Radiology & Ultrasound.

  13. Evaluation and reduction of magnetic resonance imaging artifacts induced by distinct plates for osseous fixation: an in vitro study @ 3T.

    Science.gov (United States)

    Rendenbach, Carsten; Schoellchen, Maximilian; Bueschel, Julie; Gauer, Tobias; Sedlacik, Jan; Kutzner, Daniel; Vallittu, Pekka K; Heiland, Max; Smeets, Ralf; Fiehler, Jens; Siemonsen, Susanne

    2018-05-02

    To analyze Magnetic Resonance Imaging (MRI) artifact induced at 3 Tesla by bioresorbable, titanium and glass fiber reinforced composite (GFRC) plates for osseous reconstruction. Fixation plates including bioresorbable polymers (Inion CPS, Inion Oy, Tampere, Finland; Rapidsorb, DePuy Synthes, Umkirch, Germany; Resorb X, Gebrueder KLS Martin GmbH, Tuttlingen, Germany), Glass fiber reinforced composite (Skulle Implants Oy, Turku, Finland) and titanium plates of varying thickness and design (DePuy Synthes, Umkirch, Germany) were embedded in agarose gel and a 3T MRI was performed using a standard protocol for head and neck imaging including T1w and T2w sequences. Additionally, different artifact reducing sequence techniques (slice encoding for metal artifact reduction (SEMAC) & ultrashort echotime (UTE)) were used and their impact on the extent of artifacts evaluated for each material. All titanium plates induced significantly more artefacts than resorbable plates in T1w and T2w sequences. Glass fiber-reinforced composites induced the least artefacts in both sequences. The total extent of artefacts increased with plate thickness and height. Plate thickness had no influence on the percentage of overestimation in all three dimensions. Titanium induced artefacts were significantly reduced by both artifact reducing sequence techniques. Polylactide, glass fiber-reinforced composite and magnesium plates produce less susceptibility artefacts in MRI compared to titanium, while the dimensions of titanium plates directly influence artifact extension. SEMAC and UTE significantly reduce metal artefacts at the expense of image resolution.

  14. Carbothermic reduction of refractory metals

    International Nuclear Information System (INIS)

    Anderson, R.N.; Parlee, N.A.D.

    1976-01-01

    The reduction of stable refractory metal oxides by carbon is generally unacceptable since the product is usually contaminated with carbides. The carbide formation may be avoided by selecting a solvent metal to dissolve the reactive metal as it is produced and reduce its chemical activity below that required for carbide formation. This approach has been successfully applied to the oxides of Si, Zr, Ti, Al, Mg, and U. In the case where a volatile suboxide, a carbonyl reaction, or a volatile metal occur, the use of the solvent metal appears satisfactory to limit the loss of material at low pressures. In several solute--solvent systems, vacuum evaporation is used to strip the solvent metal from the alloy to give the pure metal

  15. Pedogenesis, geochemical forms of heavy metals, and artifact weathering in an urban soil chronosequence, Detroit, Michigan

    Energy Technology Data Exchange (ETDEWEB)

    Howard, Jeffrey L., E-mail: jhoward@wayne.edu [Department of Geology, Wayne State University, Detroit, MI 48202 (United States); Olszewska, Dorota [Department of Geology, Wayne State University, Detroit, MI 48202 (United States)

    2011-03-15

    An urban soil chronosequence in downtown Detroit, MI was studied to determine the effects of time on pedogenesis and heavy metal sequestration. The soils developed in fill derived from mixed sandy and clayey diamicton parent materials on a level late Pleistocene lakebed plain under grass vegetation in a humid-temperate (mesic) climate. The chronosequence is comprised of soils in vacant lots (12 and 44 years old) and parks (96 and 120 years old), all located within 100 m of a roadway. An A-horizon 16 cm thick with 2% organic matter has developed after only 12 years of pedogenesis. The 12 year-old soil shows accelerated weathering of iron (e.g. nails) and cement artifacts attributed to corrosion by excess soluble salts of uncertain origin. Carbonate and Fe-oxide are immobilizing agents for heavy metals, hence it is recommended that drywall, plaster, cement and iron artifacts be left in soils at brownfield sites for their ameliorating effects. - Research highlights: > An A horizon has developed in these urban soils after only 12 years of pedogenesis. > Iron and cement artifacts have undergone accelerated weathering due to deicing salts. > One soil is contaminated by lead derived from weathered paint. > Artifact weathering can have ameliorating effects on urban soils contaminated by heavy metals. - Weathering of artifacts can have ameliorating effects on heavy metal-polluted soils at brownfield sites.

  16. Pedogenesis, geochemical forms of heavy metals, and artifact weathering in an urban soil chronosequence, Detroit, Michigan

    International Nuclear Information System (INIS)

    Howard, Jeffrey L.; Olszewska, Dorota

    2011-01-01

    An urban soil chronosequence in downtown Detroit, MI was studied to determine the effects of time on pedogenesis and heavy metal sequestration. The soils developed in fill derived from mixed sandy and clayey diamicton parent materials on a level late Pleistocene lakebed plain under grass vegetation in a humid-temperate (mesic) climate. The chronosequence is comprised of soils in vacant lots (12 and 44 years old) and parks (96 and 120 years old), all located within 100 m of a roadway. An A-horizon 16 cm thick with 2% organic matter has developed after only 12 years of pedogenesis. The 12 year-old soil shows accelerated weathering of iron (e.g. nails) and cement artifacts attributed to corrosion by excess soluble salts of uncertain origin. Carbonate and Fe-oxide are immobilizing agents for heavy metals, hence it is recommended that drywall, plaster, cement and iron artifacts be left in soils at brownfield sites for their ameliorating effects. - Research highlights: → An A horizon has developed in these urban soils after only 12 years of pedogenesis. → Iron and cement artifacts have undergone accelerated weathering due to deicing salts. → One soil is contaminated by lead derived from weathered paint. → Artifact weathering can have ameliorating effects on urban soils contaminated by heavy metals. - Weathering of artifacts can have ameliorating effects on heavy metal-polluted soils at brownfield sites.

  17. A comparative study of metal artifacts from common metal orthodontic brackets in magnetic resonance imaging

    International Nuclear Information System (INIS)

    Kajan, Zahra Dalili; Alizadeh, Ahmad; Hemmaty, Yasmin Babael; Roushan, Zahra Atrkar; Khademi, Jalil

    2015-01-01

    This study was performed to compare the metal artifacts from common metal orthodontic brackets in magnetic resonance imaging. A dry mandible with 12 intact premolars was prepared, and was scanned ten times with various types of brackets: American, 3M, Dentaurum, and Masel orthodontic brackets were used, together with either stainless steel (SS) or nickel titanium (NiTi) wires. Subsequently, three different sequences of coronal and axial images were obtained: spin-echo T1-weighted images, fast spin-echo T2-weighted images, and fluid-attenuated inversion recovery images. In each sequence, the two sequential axial and coronal images with the largest signal-void area were selected. The largest diameters of the signal voids in the direction of the X-, Y-, and Z-axes were then measured twice. Finally, the mean linear values associated with different orthodontic brackets were analyzed using one-way analysis of variation, and the results were compared using the independent t-test to assess whether the use of SS or NiTi wires had a significant effect on the images. Statistically significant differences were only observed along the Z-axis among the four different brands of orthodontic brackets with SS wires. A statistically significant difference was observed along all axes among the brackets with NiTi wires. A statistically significant difference was found only along the Z-axis between nickel-free and nickel-containing brackets. With respect to all axes, the 3M bracket was associated with smaller signal-void areas. Overall, the 3M and Dentaurum brackets with NiTi wires induced smaller artifacts along all axes than those with SS wires

  18. A comparative study of metal artifacts from common metal orthodontic brackets in magnetic resonance imaging

    Energy Technology Data Exchange (ETDEWEB)

    Kajan, Zahra Dalili; Alizadeh, Ahmad; Hemmaty, Yasmin Babael; Roushan, Zahra Atrkar; Khademi, Jalil [Guilan University of Medical Sciences, Rasht (Iran, Islamic Republic of)

    2015-09-15

    This study was performed to compare the metal artifacts from common metal orthodontic brackets in magnetic resonance imaging. A dry mandible with 12 intact premolars was prepared, and was scanned ten times with various types of brackets: American, 3M, Dentaurum, and Masel orthodontic brackets were used, together with either stainless steel (SS) or nickel titanium (NiTi) wires. Subsequently, three different sequences of coronal and axial images were obtained: spin-echo T1-weighted images, fast spin-echo T2-weighted images, and fluid-attenuated inversion recovery images. In each sequence, the two sequential axial and coronal images with the largest signal-void area were selected. The largest diameters of the signal voids in the direction of the X-, Y-, and Z-axes were then measured twice. Finally, the mean linear values associated with different orthodontic brackets were analyzed using one-way analysis of variation, and the results were compared using the independent t-test to assess whether the use of SS or NiTi wires had a significant effect on the images. Statistically significant differences were only observed along the Z-axis among the four different brands of orthodontic brackets with SS wires. A statistically significant difference was observed along all axes among the brackets with NiTi wires. A statistically significant difference was found only along the Z-axis between nickel-free and nickel-containing brackets. With respect to all axes, the 3M bracket was associated with smaller signal-void areas. Overall, the 3M and Dentaurum brackets with NiTi wires induced smaller artifacts along all axes than those with SS wires.

  19. A comparative study of metal artifacts from common metal orthodontic brackets in magnetic resonance imaging.

    Science.gov (United States)

    Dalili Kajan, Zahra; Khademi, Jalil; Alizadeh, Ahmad; Babaei Hemmaty, Yasamin; Atrkar Roushan, Zahra

    2015-09-01

    This study was performed to compare the metal artifacts from common metal orthodontic brackets in magnetic resonance imaging. A dry mandible with 12 intact premolars was prepared, and was scanned ten times with various types of brackets: American, 3M, Dentaurum, and Masel orthodontic brackets were used, together with either stainless steel (SS) or nickel titanium (NiTi) wires. Subsequently, three different sequences of coronal and axial images were obtained: spin-echo T1 -weighted images, fast spin-echo T2 -weighted images, and fluid-attenuated inversion recovery images. In each sequence, the two sequential axial and coronal images with the largest signal-void area were selected. The largest diameters of the signal voids in the direction of the X-, Y-, and Z-axes were then measured twice. Finally, the mean linear values associated with different orthodontic brackets were analyzed using one-way analysis of variation, and the results were compared using the independent t-test to assess whether the use of SS or NiTi wires had a significant effect on the images. Statistically significant differences were only observed along the Z-axis among the four different brands of orthodontic brackets with SS wires. A statistically significant difference was observed along all axes among the brackets with NiTi wires. A statistically significant difference was found only along the Z-axis between nickel-free and nickel-containing brackets. With respect to all axes, the 3M bracket was associated with smaller signal-void areas. Overall, the 3M and Dentaurum brackets with NiTi wires induced smaller artifacts along all axes than those with SS wires.

  20. Generation of hybrid sinograms for the recovery of kV-CT images with metal artifacts for helical tomotherapy

    International Nuclear Information System (INIS)

    Jeon, Hosang; Park, Dahl; Kim, Wontaek; Ki, Yongkan; Kim, Yong Ho; Lee, Ju Hye; Kim, Dongwon; Youn, Hanbean; Nam, Jiho; Lee, Jayoung; Kim, Ho Kyung

    2015-01-01

    Purpose: The overall goal of this study is to restore kilovoltage computed tomography (kV-CT) images which are disfigured by patients’ metal prostheses. By generating a hybrid sinogram that is a combination of kV and megavoltage (MV) projection data, the authors suggest a novel metal artifact-reduction (MAR) method that retains the image quality to match that of kV-CT and simultaneously restores the information of metal prostheses lost due to photon starvation. Methods: CT projection data contain information about attenuation coefficients and the total length of the attenuation. By normalizing raw kV projections with their own total lengths of attenuation, mean attenuation projections were obtained. In the same manner, mean density projections of MV-CT were obtained by the normalization of MV projections resulting from the forward projection of density-calibrated MV-CT images with the geometric parameters of the kV-CT device. To generate the hybrid sinogram, metal-affected signals of the kV sinogram were identified and replaced by the corresponding signals of the MV sinogram following a density calibration step with kV data. Filtered backprojection was implemented to reconstruct the hybrid CT image. To validate the authors’ approach, they simulated four different scenarios for three heads and one pelvis using metallic rod inserts within a cylindrical phantom. Five inserts describing human body elements were also included in the phantom. The authors compared the image qualities among the kV, MV, and hybrid CT images by measuring the contrast-to-noise ratio (CNR), the signal-to-noise ratio (SNR), the densities of all inserts, and the spatial resolution. In addition, the MAR performance was compared among three existing MAR methods and the authors’ hybrid method. Finally, for clinical trials, the authors produced hybrid images of three patients having dental metal prostheses to compare their MAR performances with those of the kV, MV, and three existing MAR

  1. Evaluation of two iterative techniques for reducing metal artifacts in computed tomography.

    Science.gov (United States)

    Boas, F Edward; Fleischmann, Dominik

    2011-06-01

    To evaluate two methods for reducing metal artifacts in computed tomography (CT)--the metal deletion technique (MDT) and the selective algebraic reconstruction technique (SART)--and compare these methods with filtered back projection (FBP) and linear interpolation (LI). The institutional review board approved this retrospective HIPAA-compliant study; informed patient consent was waived. Simulated projection data were calculated for a phantom that contained water, soft tissue, bone, and iron. Clinical projection data were obtained retrospectively from 11 consecutively identified CT scans with metal streak artifacts, with a total of 178 sections containing metal. Each scan was reconstructed using FBP, LI, SART, and MDT. The simulated scans were evaluated quantitatively by calculating the average error in Hounsfield units for each pixel compared with the original phantom. Two radiologists who were blinded to the reconstruction algorithms used qualitatively evaluated the clinical scans, ranking the overall severity of artifacts for each algorithm. P values for comparisons of the image quality ranks were calculated from the binomial distribution. The simulations showed that MDT reduces artifacts due to photon starvation, beam hardening, and motion and does not introduce new streaks between metal and bone. MDT had the lowest average error (76% less than FBP, 42% less than LI, 17% less than SART). Blinded comparison of the clinical scans revealed that MDT had the best image quality 100% of the time (95% confidence interval: 72%, 100%). LI had the second best image quality, and SART and FBP had the worst image quality. On images from two CT scans, as compared with images generated by the scanner, MDT revealed information of potential clinical importance. For a wide range of scans, MDT yields reduced metal streak artifacts and better-quality images than does FBP, LI, or SART. http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.11101782/-/DC1. RSNA, 2011

  2. Magnetic susceptibility and electrical conductivity of metallic dental materials and their impact on MR imaging artifacts

    Czech Academy of Sciences Publication Activity Database

    Starčuková, Jana; Starčuk jr., Zenon; Hubálková, H.; Linetskiy, I.

    2008-01-01

    Roč. 24, č. 6 (2008), s. 715-723 ISSN 0109-5641 R&D Projects: GA MZd NR8110 Institutional research plan: CEZ:AV0Z20650511 Keywords : metallic dental materials * dental alloys * amalgams * MR imaging * magnetic susceptibility * electric conductivity * image artifact Subject RIV: FF - HEENT, Dentistry Impact factor: 2.941, year: 2008

  3. On the influence of high-pass filtering on ICA-based artifact reduction in EEG-ERP.

    Science.gov (United States)

    Winkler, Irene; Debener, Stefan; Müller, Klaus-Robert; Tangermann, Michael

    2015-01-01

    Standard artifact removal methods for electroencephalographic (EEG) signals are either based on Independent Component Analysis (ICA) or they regress out ocular activity measured at electrooculogram (EOG) channels. Successful ICA-based artifact reduction relies on suitable pre-processing. Here we systematically evaluate the effects of high-pass filtering at different frequencies. Offline analyses were based on event-related potential data from 21 participants performing a standard auditory oddball task and an automatic artifactual component classifier method (MARA). As a pre-processing step for ICA, high-pass filtering between 1-2 Hz consistently produced good results in terms of signal-to-noise ratio (SNR), single-trial classification accuracy and the percentage of `near-dipolar' ICA components. Relative to no artifact reduction, ICA-based artifact removal significantly improved SNR and classification accuracy. This was not the case for a regression-based approach to remove EOG artifacts.

  4. Total Variation-Based Reduction of Streak Artifacts, Ring Artifacts and Noise in 3D Reconstruction from Optical Projection Tomography

    Czech Academy of Sciences Publication Activity Database

    Michálek, Jan

    2015-01-01

    Roč. 21, č. 6 (2015), s. 1602-1615 ISSN 1431-9276 R&D Projects: GA MŠk(CZ) LH13028; GA ČR(CZ) GA13-12412S Institutional support: RVO:67985823 Keywords : optical projection tomography * microscopy * artifacts * total variation * data mismatch Subject RIV: EA - Cell Biology Impact factor: 1.730, year: 2015

  5. Reduction of motion artifact in pulse oximetry by smoothed pseudo Wigner-Ville distribution

    Directory of Open Access Journals (Sweden)

    Zhang Yuan-ting

    2005-03-01

    Full Text Available Abstract Background The pulse oximeter, a medical device capable of measuring blood oxygen saturation (SpO2, has been shown to be a valuable device for monitoring patients in critical conditions. In order to incorporate the technique into a wearable device which can be used in ambulatory settings, the influence of motion artifacts on the estimated SpO2 must be reduced. This study investigates the use of the smoothed psuedo Wigner-Ville distribution (SPWVD for the reduction of motion artifacts affecting pulse oximetry. Methods The SPWVD approach is compared with two techniques currently used in this field, i.e. the weighted moving average (WMA and the fast Fourier transform (FFT approaches. SpO2 and pulse rate were estimated from a photoplethysmographic (PPG signal recorded when subject is in a resting position as well as in the act of performing four types of motions: horizontal and vertical movements of the hand, and bending and pressing motions of the finger. For each condition, 24 sets of PPG signals collected from 6 subjects, each of 30 seconds, were studied with reference to the PPG signal recorded simultaneously from the subject's other hand, which was stationary at all times. Results and Discussion The SPWVD approach shows significant improvement (p Conclusion The results suggested that the SPWVD approach could potentially be used to reduce motion artifact on wearable pulse oximeters.

  6. Online Reduction of Artifacts in EEG of Simultaneous EEG-fMRI Using Reference Layer Adaptive Filtering (RLAF).

    Science.gov (United States)

    Steyrl, David; Krausz, Gunther; Koschutnig, Karl; Edlinger, Günter; Müller-Putz, Gernot R

    2018-01-01

    Simultaneous electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) allow us to study the active human brain from two perspectives concurrently. Signal processing based artifact reduction techniques are mandatory for this, however, to obtain reasonable EEG quality in simultaneous EEG-fMRI. Current artifact reduction techniques like average artifact subtraction (AAS), typically become less effective when artifact reduction has to be performed on-the-fly. We thus present and evaluate a new technique to improve EEG quality online. This technique adds up with online AAS and combines a prototype EEG-cap for reference recordings of artifacts, with online adaptive filtering and is named reference layer adaptive filtering (RLAF). We found online AAS + RLAF to be highly effective in improving EEG quality. Online AAS + RLAF outperformed online AAS and did so in particular online in terms of the chosen performance metrics, these being specifically alpha rhythm amplitude ratio between closed and opened eyes (3-45% improvement), signal-to-noise-ratio of visual evoked potentials (VEP) (25-63% improvement), and VEPs variability (16-44% improvement). Further, we found that EEG quality after online AAS + RLAF is occasionally even comparable with the offline variant of AAS at a 3T MRI scanner. In conclusion RLAF is a very effective add-on tool to enable high quality EEG in simultaneous EEG-fMRI experiments, even when online artifact reduction is necessary.

  7. Inspection about the corrosion of metallic archaeological artifacts in ground. 2

    Energy Technology Data Exchange (ETDEWEB)

    Honda, Takashi; Yamaguchi, Shingo [Hitachi Engineering Co., Ltd., Hitachi, Ibaraki (Japan)

    2002-02-01

    The corrosion of iron-base archaeological artifacts, which were dug out in Iyomai-7 (Chitose-shi, Hokkaido) and Izumo-Ooyashiro-Keidai (Taisha-machi, Shimane-ken) sites, was investigated by using X-ray CT, XRD, atomic absorption spectroscopy and EDX techniques. While the artifacts such as swords in Iyomai-7 site had been buried in the ground for 400-500 years, metallic iron remained in the swords and the corrosion amounts were estimated to be 2-5 mm. Several artifacts were investigated among a lot of iron rings and nails buried beside huge pillars of the ancient shrine. Those artifacts had been in ground for 730-750 years. The corrosion amounts were estimated to be 3-5 mm. As the both soil environments are supposed to be oxidizing, the outer oxide layers of all species are composed of goethite and soil. Further, it was clarified that perfectly corroded ones had hollow structures. In this study, the sampling method of species, the corrosion environmental factors, and the corrosion kinetic models were also evaluated. (author)

  8. Performances of low-dose dual-energy CT in reducing artifacts from implanted metallic orthopedic devices

    Energy Technology Data Exchange (ETDEWEB)

    Filograna, Laura [Catholic University of Rome, School of Medicine, University Hospital ' ' A. Gemelli' ' , Department of Radiological Sciences, Institute of Radiology, Rome (Italy); University of Zurich, Department of Forensic Medicine and Imaging, Institute of Forensic Medicine, Zurich (Switzerland); Magarelli, Nicola; Leone, Antonio; Bonomo, Lorenzo [Catholic University of Rome, School of Medicine, University Hospital ' ' A. Gemelli' ' , Department of Radiological Sciences, Institute of Radiology, Rome (Italy); De Waure, Chiara; Calabro, Giovanna Elisa [Catholic University of Rome, School of Medicine, University Hospital ' ' A. Gemelli' ' , Research Centre for Health Technology Assessment, Department of Public Health, Section of Hygiene, Rome (Italy); Finkenstaedt, Tim [University Hospital Zurich, Institute of Diagnostic and Interventional Radiology, Zurich (Switzerland); Thali, Michael John [University of Zurich, Department of Forensic Medicine and Imaging, Institute of Forensic Medicine, Zurich (Switzerland)

    2016-07-15

    The objective was to evaluate the performances of dose-reduced dual-energy computed tomography (DECT) in decreasing metallic artifacts from orthopedic devices compared with dose-neutral DECT, dose-neutral single-energy computed tomography (SECT), and dose-reduced SECT. Thirty implants in 20 consecutive cadavers underwent both SECT and DECT at three fixed CT dose indexes (CTDI): 20.0, 10.0, and 5.0 mGy. Extrapolated monoenergetic DECT images at 64, 69, 88, 105, 120, and 130 keV, and individually adjusted monoenergy for optimized image quality (OPTkeV) were generated. In each group, the image quality of the seven monoenergetic images and of the SECT image was assessed qualitatively and quantitatively by visually rating and by measuring the maximum streak artifact respectively. The comparison between SECT and OPTkeV evaluated overall within all groups showed a significant difference (p <0.001), with OPTkeV images providing better images. Comparing OPTkeV with the other DECT images, a significant difference was shown (p <0.001), with OPTkeV and 130-keV images providing the qualitatively best results. The OPTkeV images of 5.0-mGy acquisitions provided percentages of images with scores 1 and 2 of 36 % and 30 % respectively, compared with 0 % and 33.3 % of the corresponding SECT images of 10- and 20-mGy acquisitions. Moreover, DECT reconstructions at the OPTkeV of the low-dose group showed higher CT numbers than the SECT images of dose groups 1 and 2. This study demonstrates that low-dose DECT permits a reduction of artifacts due to metallic implants to be obtained in a similar manner to neutral-dose DECT and better than reduced or neutral-dose SECT. (orig.)

  9. Photoplethysmograph signal reconstruction based on a novel motion artifact detection-reduction approach. Part II: Motion and noise artifact removal.

    Science.gov (United States)

    Salehizadeh, S M A; Dao, Duy K; Chong, Jo Woon; McManus, David; Darling, Chad; Mendelson, Yitzhak; Chon, Ki H

    2014-11-01

    We introduce a new method to reconstruct motion and noise artifact (MNA) contaminated photoplethysmogram (PPG) data. A method to detect MNA corrupted data is provided in a companion paper. Our reconstruction algorithm is based on an iterative motion artifact removal (IMAR) approach, which utilizes the singular spectral analysis algorithm to remove MNA artifacts so that the most accurate estimates of uncorrupted heart rates (HRs) and arterial oxygen saturation (SpO2) values recorded by a pulse oximeter can be derived. Using both computer simulations and three different experimental data sets, we show that the proposed IMAR approach can reliably reconstruct MNA corrupted data segments, as the estimated HR and SpO2 values do not significantly deviate from the uncorrupted reference measurements. Comparison of the accuracy of reconstruction of the MNA corrupted data segments between our IMAR approach and the time-domain independent component analysis (TD-ICA) is made for all data sets as the latter method has been shown to provide good performance. For simulated data, there were no significant differences in the reconstructed HR and SpO2 values starting from 10 dB down to -15 dB for both white and colored noise contaminated PPG data using IMAR; for TD-ICA, significant differences were observed starting at 10 dB. Two experimental PPG data sets were created with contrived MNA by having subjects perform random forehead and rapid side-to-side finger movements show that; the performance of the IMAR approach on these data sets was quite accurate as non-significant differences in the reconstructed HR and SpO2 were found compared to non-contaminated reference values, in most subjects. In comparison, the accuracy of the TD-ICA was poor as there were significant differences in reconstructed HR and SpO2 values in most subjects. For non-contrived MNA corrupted PPG data, which were collected with subjects performing walking and stair climbing tasks, the IMAR significantly

  10. Evaluation of some ancient metal and clay artifacts by the radiography technique

    International Nuclear Information System (INIS)

    Tugrul, B.; Sungur, F.; Mericboyu, Y.; Yildiz, F.

    1986-01-01

    X-ray radiography and betagraphy which are applied on different archaeological artifacts have been given including some general information about the technique. A study was realized on a chunk of beads and a disc which can not be noticed by visual inspection, clustered together. The x-ray radiography of the cluster disclosed that the disc has cuneiform script on it which is assigned to the period of Assyrian King Shalmaneser I. The other two studies were realized on the metal artifacts an armour and latch. Furthermore, betagraphy was applied an armour cloth. X-ray radiography was applied on tablets in spite of the limitations of the technique. Further infotmation were obtained about on enveloped letter tablets. Therefore, the radiographic evaluation can be easy and nondestructively which is impossible otherwise. (author)

  11. Metal artifact removal (MAR) analysis for the security inspections using the X-ray computed tomography

    International Nuclear Information System (INIS)

    Cho, Hyo Sung; Woo, Tae Ho; Park, Chul Kyu

    2016-01-01

    Using the metal artifact property, it is analyzed for the X-ray computed tomography (CT) in the aspect of the security on the examined places like airport and surveillance areas. Since the importance of terror prevention strategy has been increased, the security application of X-ray CT has the significant remark. One shot X-ray image has the limitation to find out the exact shape to property in the closed box, which could be solved by the CT scanning without the tearing off the box in this work. Cleaner images can be obtained by the advanced technology if the CT scanning is utilized in the security purposes on the secured areas. A metal sample is treated by the metal artifact removal (MAR) method for the enhanced image. The mimicked explosive is experimented for the imaging processing application where the cleaner one is obtained. The procedure is explained and the further study is discussed. - Highlights: • The X-ray image is used for the nuclear inspections which are made by the image processing. • Nuclear security has been performed for counterterrorism. • Easy and fast inspections are needed. • Metal shows the characteristics of the noises.

  12. Determination of reduction yield of lithium metal reduction process

    International Nuclear Information System (INIS)

    Choi, In Kyu; Cho, Young Hwan; Kim, Taek Jin; Jee, Kwang Young

    2004-01-01

    Metal reduction of spent oxide fuel is the first step for the effective storage of spent fuel in Korea as well as transmutation purpose of long-lived radio-nuclides. During the reduction of uranium oxide by lithium metal to uranium metal, lithium oxide is stoichiometrically produced. By determining the concentration of lithium oxide in lithium chloride, we can estimate that how much uranium oxide is converted to uranium metal. Previous method to determine the lithium oxide concentration in lithium chloride is tedious and timing consuming. This paper describe the on-line monitoring method of lithium oxide during the reduction process

  13. Reduction of motion artifacts for PET imaging by respiratory correlated dynamic scanning

    International Nuclear Information System (INIS)

    Chuang, K.-S.; Chen, T.-J.; Chang, C.-C.; Wu, J.; Chen, S.; Wu, L.-C.; Liu, R.-S.

    2006-01-01

    Organ motion caused by respiration is a major challenge in positron emission tomography (PET) imaging. This work proposes a technique to reduce smearing in PET imaging caused by respiratory motion. Dynamic scanning at 1 frame/s is used. A point source, used as a marker, is attached to the object's abdomen during the scan. The source position in the projection view moves with respiratory motion and can be used to represent the respiratory phase within the time interval in which each frame data are acquired. One hundred and twenty frames are obtained for each study. The range of the positions of the marker is divided into four groups, representing different respiratory phases. The frames in which the organ positions (phases) are the same summed to produce a static sub-sinogram. Each sub-sinogram then undergoes regular image reconstruction to yield a motion-free image. The technique is applied to one volunteer under both free and coached breathing conditions. A parameter called the volume reduction factor is adopted to evaluate the effectiveness of this motion-reduction technique. The preliminary results indicate that the proposed technique effectively reduces motion artifacts in the image. Coached breathing yields better results than free breathing condition. The advantages of this method are that (1) the scanning time remains the same; (2) free breathing is allowed during the acquisition of the image; and (3) no user intervention is required

  14. Influence of metal artifacts on in vivo micro-CT for orthodontic mini-implants

    International Nuclear Information System (INIS)

    Ejima, Ken-ichiro; Omasa, Saori; Motoyoshi, Mitsuru; Arai, Yoshinori; Kai, Yukiko; Amemiya, Toshihiko; Yamada, Hisaya; Honda, Kazuya; Shimizu, Noriyoshi

    2012-01-01

    This study aimed to show the effects of metal artifacts on the in vivo micro-CT of mini-implants by measuring bone volume. We drilled a hole in the cortical bone of a rat tibia and embedded a titanium orthodontic mini-implant (diameter, 1.5 mm) in the hole. Twelve individually weighed hydroxyapatite grains (HA grains) were placed around the implant either by one dentist (method 1) or separately by 12 dentists (method 2). In vivo micro-CT was used to scan the model after placement of each grain to measure increases and decreases in bone volume voxel number. The subtracted bone voxel volume increased with HA weight in both methods. Simple linear regression analysis showed a significant correlation between weight and volume in both methods (method 1: regression coefficient: 516.502, P<0.05; method 2: regression coefficient: 4837.432, P<0.05). Metal artifacts did not appear to influence measurements of bone volume, although further studies are required to determine the effect of thicker implants. (author)

  15. MRI Artifacts of a Metallic Stent Derived From a Human Aorta Specimen

    International Nuclear Information System (INIS)

    Soto, M. E.; Flores, P.; Marrufo, O.; Hidalgo, S. S.; Rodriguez, A. O.

    2010-01-01

    Magnetic resonance imaging has proved to be a useful technique to get images of the whole body. However, the presence of ferromagnetic material can cause susceptibility artifacts, which result from microscopic gradients that occur near the boundaries between areas displaying different magnetic susceptibility. These gradients cause dephasing of spins and frequency shifts in the surrounding tissues. Intravoxel dephasing and spatial mis-registration can degrade image quality. An aorta with a metallic stent was preserved in formaldehyde at 10% inside acrylic cylinders and used to obtain MR images. We tested pulsed spin echo and gradient echo sequences to improve image quality. All experiments were performed on a 7T/21 cm Varian system (Varian, Inc, Palo Alto, CA) equipped with Direct Drive technology and a 16-rung birdcage coil transceiver. The presence of metallic stents produces a lack of signal that might give falsely reassuring appearances within the vessel lumen.

  16. Ring artifact reduction in synchrotron X-ray tomography through helical acquisition

    NARCIS (Netherlands)

    D.M. Pelt (Daniël); D.Y. Parkinson (Dilworth)

    2017-01-01

    textabstractIn synchrotron X-ray tomography, systematic defects in certain detector elements can result in arc-shaped artifacts in the final reconstructed image of the scanned sample. These ring artifacts are commonly found in many applications of synchrotron tomography, and can make

  17. Blooming Artifact Reduction in Coronary Artery Calcification by A New De-blooming Algorithm: Initial Study.

    Science.gov (United States)

    Li, Ping; Xu, Lei; Yang, Lin; Wang, Rui; Hsieh, Jiang; Sun, Zhonghua; Fan, Zhanming; Leipsic, Jonathon A

    2018-05-02

    The aim of this study was to investigate the use of de-blooming algorithm in coronary CT angiography (CCTA) for optimal evaluation of calcified plaques. Calcified plaques were simulated on a coronary vessel phantom and a cardiac motion phantom. Two convolution kernels, standard (STND) and high-definition standard (HD STND), were used for imaging reconstruction. A dedicated de-blooming algorithm was used for imaging processing. We found a smaller bias towards measurement of stenosis using the de-blooming algorithm (STND: bias 24.6% vs 15.0%, range 10.2% to 39.0% vs 4.0% to 25.9%; HD STND: bias 17.9% vs 11.0%, range 8.9% to 30.6% vs 0.5% to 21.5%). With use of de-blooming algorithm, specificity for diagnosing significant stenosis increased from 45.8% to 75.0% (STND), from 62.5% to 83.3% (HD STND); while positive predictive value (PPV) increased from 69.8% to 83.3% (STND), from 76.9% to 88.2% (HD STND). In the patient group, reduction in calcification volume was 48.1 ± 10.3%, reduction in coronary diameter stenosis over calcified plaque was 52.4 ± 24.2%. Our results suggest that the novel de-blooming algorithm could effectively decrease the blooming artifacts caused by coronary calcified plaques, and consequently improve diagnostic accuracy of CCTA in assessing coronary stenosis.

  18. Electrochemical reduction of cerium oxide into metal

    Energy Technology Data Exchange (ETDEWEB)

    Claux, Benoit [CEA, Valduc, F-21120 Is-sur-Tille (France); Universite de Grenoble, LEPMI-ENSEEG, 1130 rue de la Piscine, BP75, F-38402 St Martin d' Heres Cedex (France); Serp, Jerome, E-mail: jerome.serp@cea.f [CEA, Valduc, F-21120 Is-sur-Tille (France); Fouletier, Jacques [Universite de Grenoble, LEPMI-ENSEEG, 1130 rue de la Piscine, BP75, F-38402 St Martin d' Heres Cedex (France)

    2011-02-28

    The Fray Farthing and Chen (FFC) and Ono and Suzuki (OS) processes were developed for the reduction of titanium oxide to titanium metal by electrolysis in high temperature molten alkali chloride salts. The possible transposition to CeO{sub 2} reduction is considered in this study. Present work clarifies, by electro-analytical techniques, the reduction pathway leading to the metal. The reduction of CeO{sub 2} into metal was feasible via an indirect mechanism. Electrolyses on 10 g of CeO{sub 2} were carried out to evaluate the electrochemical process efficiency. Ca metal is electrodeposited at the cathode from CaCl{sub 2}-KCl solvent and reacts chemically with ceria to form not only metallic cerium, but also cerium oxychloride.

  19. Evaluation of MRI artifacts caused by metallic dental implants and classification of the dental materials in use

    Czech Academy of Sciences Publication Activity Database

    Starčuk jr., Zenon; Bartušek, Karel; Hubálková, H.; Bachorec, T.; Starčuková, Jana; Krupa, P.

    2006-01-01

    Roč. 6, č. 2 (2006), s. 24-27 ISSN 1335-8871 R&D Projects: GA MZd NR8110 Institutional research plan: CEZ:AV0Z20650511 Keywords : magnetic resonance imaging * artifacts * metallic implants * dental alloys * magnetic susceptibility Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering

  20. [Contrastive analysis of artifacts produced by metal dental crowns in 3.0 T magnetic resonance imaging with six sequences].

    Science.gov (United States)

    Lan, Gao; Yunmin, Lian; Pu, Wang; Haili, Huai

    2016-06-01

    This study aimed to observe and evaluate six 3.0 T sequences of metallic artifacts produced by metal dental crowns. Dental crowns fabricated with four different materials (Co-Gr, Ni-Gr, Ti alloy and pure Ti) were evaluated. A mature crossbreed dog was used as the experimental animal, and crowns were fabricated for its upper right second premolar. Each crown was examined through head MRI (3.0 T) with six sequences, namely, T₁ weighted-imaging of spin echo (T₁W/SE), T₂ weighted-imaging of inversion recovery (T₂W/IR), T₂ star gradient echo (T₂*/GRE), T2 weighted-imaging of fast spin echo (T₂W/FSE), T₁ weighted-imaging of fluid attenuate inversion recovery (T₂W/FLAIR), and T₂ weighted-imaging of propeller (T₂W/PROP). The largest area and layers of artifacts were assessed and compared. The artifact in the T₂*/GRE sequence was significantly wider than those in the other sequences (P 0.05). T₂*/GRE exhibit the strongest influence on the artifact, whereas the five other sequences contribute equally to artifact generation.

  1. Quantification of Artifact Reduction With Real-Time Cine Four-Dimensional Computed Tomography Acquisition Methods

    International Nuclear Information System (INIS)

    Langner, Ulrich W.; Keall, Paul J.

    2010-01-01

    Purpose: To quantify the magnitude and frequency of artifacts in simulated four-dimensional computed tomography (4D CT) images using three real-time acquisition methods- direction-dependent displacement acquisition, simultaneous displacement and phase acquisition, and simultaneous displacement and velocity acquisition- and to compare these methods with commonly used retrospective phase sorting. Methods and Materials: Image acquisition for the four 4D CT methods was simulated with different displacement and velocity tolerances for spheres with radii of 0.5 cm, 1.5 cm, and 2.5 cm, using 58 patient-measured tumors and respiratory motion traces. The magnitude and frequency of artifacts, CT doses, and acquisition times were computed for each method. Results: The mean artifact magnitude was 50% smaller for the three real-time methods than for retrospective phase sorting. The dose was ∼50% lower, but the acquisition time was 20% to 100% longer for the real-time methods than for retrospective phase sorting. Conclusions: Real-time acquisition methods can reduce the frequency and magnitude of artifacts in 4D CT images, as well as the imaging dose, but they increase the image acquisition time. The results suggest that direction-dependent displacement acquisition is the preferred real-time 4D CT acquisition method, because on average, the lowest dose is delivered to the patient and the acquisition time is the shortest for the resulting number and magnitude of artifacts.

  2. SU-E-I-62: Reduction of Susceptibility Artifacts by Increasing the Bandwidth (BW) and Echo Train Length (ETL)

    International Nuclear Information System (INIS)

    Mavroidis, P; Boci, N; Kostopoulos, S; Ninos, C; Glotsos, D; Oikonomou, G; Bakas, A; Roka, V; Cavouras, D; Lavdas, E; Sakkas, G; Tsagkalis, A; Chatzivasileiou, V; Batsikas, G; Papanikolaou, N; Stathakis, S

    2015-01-01

    Purpose: The aim of this present study is to increase bandwidth (BW) and echo train length (ETL) in Proton Density Turbo Spin Echo (PD TSE) sequences with and without fat saturation (FS) as well as in Turbo Inversion Recovery Magnitude sequences (TIRM) in order to assess whether these sequences are capable of reducing susceptibility artifacts. Methods: We compared 1) TIRM coronal (COR) with the same sequence with increased both BW and ETL 2) Conventional PD TSE sagittal (SAG) with FS with an increased BW 3) Conventional PD TSE SAG without FS with an increased BW 4) Conventional PD TSE SAG without FS with increased both BW and ETL. A quantitative analysis was performed to measure the extent of the susceptibility artifacts. Furthermore, a qualitative analysis was performed by two radiologists in order to evaluate the susceptibility artifacts, image distortion and fat suppression. The depiction of cartilage, menisci, muscles, tendons and bone marrow were also qualitatively analyzed. Results: The quantitative analysis found that the modified TIRM sequence is significantly superior to the conventional one regarding the extent of the susceptibility artifacts. In the qualitative analysis, the modified TIRM sequence was superior to the corresponding conventional one in eight characteristics out of ten that were analyzed. The modified PD TSE with FS was superior to the corresponding conventional one regarding the susceptibility artifacts, image distortion and depiction of bone marrow and cartilage while achieving effective fat saturation. The modified PD TSE sequence without FS with a high (H) BW was found to be superior corresponding to the conventional one in the case of cartilage. Conclusion: Consequently, TIRM sequence with an increased BW and ETL is proposed for producing images of high quality and modified PD TSE with H BW for smaller metals, especially when FS is used

  3. PRODUCTION OF URANIUM METAL BY CARBON REDUCTION

    Science.gov (United States)

    Holden, R.B.; Powers, R.M.; Blaber, O.J.

    1959-09-22

    The preparation of uranium metal by the carbon reduction of an oxide of uranium is described. In a preferred embodiment of the invention a charge composed of carbon and uranium oxide is heated to a solid mass after which it is further heated under vacuum to a temperature of about 2000 deg C to produce a fused uranium metal. Slowly ccoling the fused mass produces a dendritic structure of uranium carbide in uranium metal. Reacting the solidified charge with deionized water hydrolyzes the uranium carbide to finely divide uranium dioxide which can be separated from the coarser uranium metal by ordinary filtration methods.

  4. Characterization and reduction of motion artifacts in photoplethysmographic signals from a wrist-worn device

    NARCIS (Netherlands)

    Tauţan, A.M.; Young, A.; Wentink, E.; Wieringa, F.P.

    2015-01-01

    Methods for analyzing various motion artifacts in photoplethysmography (PPG) signals, recorded by a wristworn device are reported. The analysis looks both at intrinsic PPG signal properties, through standard deviation, skew and kurtosis, but also at its relationship to five possible motion reference

  5. Artifact Reduction of Susceptibility-Weighted Imaging Using a Short-Echo Phase Mask

    International Nuclear Information System (INIS)

    Ishimori, Y.; Monma, M.; Kohno, Y.

    2009-01-01

    Background: Susceptibility-weighted imaging (SWI) is utilized in magnetic resonance (MR) venography and other applications, but can include artifacts caused by the phase-masking process. Purpose: To demonstrate risks of filter processes used in making phase masks for SWI, and to propose a simple method for reducing artifacts. Material and Methods: Phase linearity related to echo time (TE) was evaluated for the original phase and high-pass-filtered phase using a CuSO 4 -doped water phantom. Effect of filter size of the Hanning window and background homogeneity were also evaluated in a phantom study. Use of a phase mask generated by data with differing magnitudes of TE was attempted in a human study. Shorter TE was used for making the phase mask, and the number of multiplications was increased. As short and long TEs were necessary simultaneously for phase mask and T2* contrast, a dual-echo technique was used. Results: Linearity of TE and phase value collapsed, and an unexpected negative phase appeared in the high-pass-filtered phase. Using a short-TE phase mask, phase-aliasing artifacts were reduced and visibility of deep veins was equivalent to that under conventional methods with an increased number of multiplications. Conclusion: Use of a short-echo phase mask in SWI is useful for reducing artifacts

  6. Artifact Reduction of Susceptibility-Weighted Imaging Using a Short-Echo Phase Mask

    Energy Technology Data Exchange (ETDEWEB)

    Ishimori, Y.; Monma, M. (Dept. of Radiological Sciences, Ibaraki Prefectural Univ. of Health Sciences, Inashiki-gun, Ibaraki (Japan)); Kohno, Y. (Dept. of Neurology, Ibaraki Prefectural Univ. of Health Sciences, Inashiki-gun, Ibaraki (Japan))

    2009-11-15

    Background: Susceptibility-weighted imaging (SWI) is utilized in magnetic resonance (MR) venography and other applications, but can include artifacts caused by the phase-masking process. Purpose: To demonstrate risks of filter processes used in making phase masks for SWI, and to propose a simple method for reducing artifacts. Material and Methods: Phase linearity related to echo time (TE) was evaluated for the original phase and high-pass-filtered phase using a CuSO{sub 4}-doped water phantom. Effect of filter size of the Hanning window and background homogeneity were also evaluated in a phantom study. Use of a phase mask generated by data with differing magnitudes of TE was attempted in a human study. Shorter TE was used for making the phase mask, and the number of multiplications was increased. As short and long TEs were necessary simultaneously for phase mask and T2 contrast, a dual-echo technique was used. Results: Linearity of TE and phase value collapsed, and an unexpected negative phase appeared in the high-pass-filtered phase. Using a short-TE phase mask, phase-aliasing artifacts were reduced and visibility of deep veins was equivalent to that under conventional methods with an increased number of multiplications. Conclusion: Use of a short-echo phase mask in SWI is useful for reducing artifacts

  7. Comparison of conventional filtering and independent component analysis for artifact reduction in simultaneous gastric EMG and magnetogastrography from porcines.

    Science.gov (United States)

    Irimia, Andrei; Richards, William O; Bradshaw, L Alan

    2009-11-01

    In this study, we perform a comparative study of independent component analysis (ICA) and conventional filtering (CF) for the purpose of artifact reduction from simultaneous gastric EMG and magnetogastrography (MGG). EMG/MGG data were acquired from ten anesthetized pigs by obtaining simultaneous recordings using serosal electrodes (EMG) as well as with a superconducting quantum interference device biomagnetometer (MGG). The analysis of MGG waveforms using ICA and CF indicates that ICA is superior to the CF method in its ability to extract respiration and cardiac artifacts from MGG recordings. A signal frequency analysis of ICA- and CF-processed data was also undertaken using waterfall plots, and it was determined that the two methods produce qualitatively comparable results. Through the use of simultaneous EMG/MGG, we were able to demonstrate the accuracy and trustworthiness of our results by comparison and cross-validation within the framework of a porcine model.

  8. Reduction of dental metallic artefacts in CT: Value of a newly developed algorithm for metal artefact reduction (O-MAR)

    International Nuclear Information System (INIS)

    Kidoh, M.; Nakaura, T.; Nakamura, S.; Tokuyasu, S.; Osakabe, H.; Harada, K.; Yamashita, Y.

    2014-01-01

    Aim: To evaluate the image quality of O-MAR (Metal Artifact Reduction for Orthopedic Implants) for dental metal artefact reduction. Materials and methods: This prospective study received institutional review board approval and written informed consent was obtained. Thirty patients who had dental implants or dental fillings were included in this study. Computed tomography (CT) images were obtained through the oral cavity and neck during the portal venous phase. The system reconstructed the O-MAR-processed images in addition to the uncorrected images. CT attenuation and image noise of the soft tissue of the oral cavity were compared between the O-MAR and the uncorrected images. Qualitative analysis was undertaken between the two image groups. Results: The image noise of the O-MAR images was significantly lower than that of the uncorrected images (p < 0.01). O-MAR offered plausible attenuations of soft tissue compared with non-O-MAR. Better qualitative scores were obtained in the streaking artefacts and the degree of depiction of the oral cavity with O-MAR compared with non-O-MAR. Conclusion: O-MAR enables the depiction of structures in areas in which this was not previously possible due to dental metallic artefacts in qualitative image analysis. O-MAR images may have a supplementary role in addition to uncorrected images in oral diagnosis

  9. Development of a unique phantom to assess dose error of metal artifact in head and neck cancer

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Min Young; Kang, Sang Won; Suh, Tae Suk [Dept. of Biomedical Engineering, College of Medicine, The Catholic University of Korea, Seoul (Korea, Republic of); Lee, Jeong Woo [Dept. of Radiation Oncology, Konkuk University Medical Center, Seoul (Korea, Republic of); Park, Ji Yeon [Dept. of Pediatrics and Molecular Imaging Program at Stanford, Stanford University, Stanford (United States)

    2016-04-15

    The artifacts not only blur the CT images and lead to inaccuracies in diagnosis, but also make the delineation of anatomical structures intractable, which is important in image-guided intervention procedures. These artifacts obscure the underlying anatomy, leading to uncertainty in the delineation of the target volumes and compromising the integrity of the density representation that is crucial for accurate dose calculation. Because head and neck cancer patients tend to be over the age of 50 years, they constitute a group likely to have dental prostheses. This kind of side effects considerably disturbs the therapeutic procedure. Radiation scatter from high atomic number (Z) materials is established to cause both soft tissue and bony complications in the oral cavity, making scattered radiation an important factor in head and neck region radiotherapy planning. In this study, we carried out theoretical analysis of the metal artifact, that is, streak artifact and dark artifact, and also critical analysis of dosimetric effect which cause by dental implants in CT images of head and neck cancer patients with the genuine teeth and implants inserted humanoid phantom. The phantom provides a unique and useful tool in head and neck dosimetry research. It can be used in the development of new imaging instrumentation, image acquisition strategies, and image processing and reconstruction methods.

  10. Usefulness of IDEAL T2-weighted FSE and SPGR imaging in reducing metallic artifacts in the postoperative ankles with metallic hardware

    International Nuclear Information System (INIS)

    Lee, Jung Bin; Cha, Jang Gyu; Lee, Min Hee; Lee, Eun Hye; Lee, Young Koo; Jeon, Chan Hong

    2013-01-01

    The aim of this work is to prospectively compare the effectiveness of iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEAL), T2-weighted fast spin-echo (FSE), and spoiled gradient-echo (SPGR) MR imaging to frequency selective fat suppression (FSFS) protocols for minimizing metallic artifacts in postoperative ankles with metallic hardware. The T2-weighted and SPGR imaging with IDEAL and FSFS were performed on 21 ankles of 21 patients with metallic hardware. Two musculoskeletal radiologists independently analyzed techniques for visualization of ankle ligaments and articular cartilage, uniformity of fat saturation, and relative size of the metallic artifacts. A paired t test was used for statistical comparisons of MR images between IDEAL and FSFS groups. IDEAL T2-weighted FSE and SPGR images enabled significantly improved visualization of articular cartilage (p < 0.05), the size of metallic artifact (p < 0.05), and the uniformity of fat saturation (p < 0.05). However, no significant improvement was found in the visibility of ligaments. IDEAL T2-weighted FSE and SPGR imaging effectively reduces the degree of tissue-obscuring artifacts produced by fixation hardware in ankle joints and improves image quality compared to FSFS T2-weighted FSE and SPGR imaging. However, visibility of ligaments was not improved using IDEAL imaging. (orig.)

  11. The 'sonaja del Petamuti': microstructural analysis of this pre hispanic metallic artifact of tarascan origin

    International Nuclear Information System (INIS)

    Franco V, F.; Torres M, L.; Mendoza A, D.; Juarez G, F.; Macias G, A.; Rodriguez L, V.

    2005-01-01

    As a part of the Archaeological Project 'Cuenca de Cuitzeo', several archaeological diggings were performed at the Tarascan ceremonial of Huandacareo, Michoacan, Mexico. During this work was discovered an offering with several metal artifacts of Pre hispanic origin, between them was found a ring of barrel shaped (rattle) with twelve bells joined by means of a twisted copper tread, which has been used this study. This work presents its characterization by means of scanning electron microscopy, metallography, elemental chemical analysis and X-ray radiography. The aim of the study was to determine the process of manufacture to find if the bells were welded or cast in one peace by the lost wax method. It was possible to determine the presence of grainy bumpy textures over plain and irregular surface of the object. Metallographs in selected spots of the object were accomplished by a replication method. Also, some radiograph were take to find if a solder of different density to X rays was detected. The elemental chemical composition shows the presence of Cu, O, C, Si, and P as mayor and minor elements. Besides traces of Al, Cl, Ca, K, As, Fe and M were detected. (Author)

  12. A standardized evaluation of artifacts from metallic compounds during fast MR imaging

    DEFF Research Database (Denmark)

    Murakami, Shumei; Verdonschot, Rinus G; Kataoka, Miyoshi

    2016-01-01

    according to the ASTM-F2119 standard and artifact volumes were assessed using OsiriX MD software Results: Tukey-Kramer post-hoc tests were used for statistical comparisons. For most materials, scanning sequences eliciting artifact volumes in the following (ascending) order FSE-T1/FSE-T2

  13. Low-Gain, Low-Noise Integrated Neuronal Amplifier for Implantable Artifact-Reduction Recording System

    OpenAIRE

    Zbrzeski, Adeline; Lewis, Noëlle; Rummens, Francois; Jung, Ranu; N'Kaoua, Gilles; Benazzouz, Abdelhamid; Renaud, Sylvie

    2013-01-01

    Brain neuroprostheses for neuromodulation are being designed to monitor the neural activity of the brain in the vicinity of the region being stimulated using a single macro-electrode. Using a single macro-electrode, recent neuromodulation studies show that recording systems with a low gain neuronal amplifier and successive amplifier stages can reduce or reject stimulation artifacts. These systems were made with off-the-shelf components that are not amendable for future implant design. A low-g...

  14. Optimization-based reconstruction for reduction of CBCT artifact in IGRT

    Science.gov (United States)

    Xia, Dan; Zhang, Zheng; Paysan, Pascal; Seghers, Dieter; Brehm, Marcus; Munro, Peter; Sidky, Emil Y.; Pelizzari, Charles; Pan, Xiaochuan

    2016-04-01

    Kilo-voltage cone-beam computed tomography (CBCT) plays an important role in image guided radiation therapy (IGRT) by providing 3D spatial information of tumor potentially useful for optimizing treatment planning. In current IGRT CBCT system, reconstructed images obtained with analytic algorithms, such as FDK algorithm and its variants, may contain artifacts. In an attempt to compensate for the artifacts, we investigate optimization-based reconstruction algorithms such as the ASD-POCS algorithm for potentially reducing arti- facts in IGRT CBCT images. In this study, using data acquired with a physical phantom and a patient subject, we demonstrate that the ASD-POCS reconstruction can significantly reduce artifacts observed in clinical re- constructions. Moreover, patient images reconstructed by use of the ASD-POCS algorithm indicate a contrast level of soft-tissue improved over that of the clinical reconstruction. We have also performed reconstructions from sparse-view data, and observe that, for current clinical imaging conditions, ASD-POCS reconstructions from data collected at one half of the current clinical projection views appear to show image quality, in terms of spatial and soft-tissue-contrast resolution, higher than that of the corresponding clinical reconstructions.

  15. Reduction of UF4 to U metal

    International Nuclear Information System (INIS)

    Suh, I.S.; Kim, J.H.; Min, B.T.; Whang, S.C.; Im, K.S.

    1983-01-01

    The operating conditions for the production of uranium metal by reduction of UFsub(4) with magnesium powder have been thoroughly investigated using the reactor 1 Kg nominal capacity. UFsub(4) powders which were produced from the conversion plant in KAERI are used and MgFsub(2), by-product of the reduction, are used as liner after pulverizing. 95% of average yield of uranium metal are obtained with 6% excess of magnesium powder in size of -πo + 50 mesh and its density is 18.5 g/cc, and furthermore the yield is increased when mafnesium powders are used after washed with trichloro-ethylene and dried. (Author)

  16. The effect of averaging adjacent planes for artifact reduction in matrix inversion tomosynthesis

    Science.gov (United States)

    Godfrey, Devon J.; Page McAdams, H.; Dobbins, James T.

    2013-01-01

    Purpose: Matrix inversion tomosynthesis (MITS) uses linear systems theory and knowledge of the imaging geometry to remove tomographic blur that is present in conventional backprojection tomosynthesis reconstructions, leaving in-plane detail rendered clearly. The use of partial-pixel interpolation during the backprojection process introduces imprecision in the MITS modeling of tomographic blur, and creates low-contrast artifacts in some MITS planes. This paper examines the use of MITS slabs, created by averaging several adjacent MITS planes, as a method for suppressing partial-pixel artifacts. Methods: Human chest tomosynthesis projection data, acquired as part of an IRB-approved pilot study, were used to generate MITS planes, three-plane MITS slabs (MITSa3), five-plane MITS slabs (MITSa5), and seven-plane MITS slabs (MITSa7). These were qualitatively examined for partial-pixel artifacts and the visibility of normal and abnormal anatomy. Additionally, small (5 mm) subtle pulmonary nodules were simulated and digitally superimposed upon human chest tomosynthesis projection images, and their visibility was qualitatively assessed in the different reconstruction techniques. Simulated images of a thin wire were used to generate modulation transfer function (MTF) and slice-sensitivity profile curves for the different MITS and MITS slab techniques, and these were examined for indications of partial-pixel artifacts and frequency response uniformity. Finally, mean-subtracted, exposure-normalized noise power spectra (ENNPS) estimates were computed and compared for MITS and MITS slab reconstructions, generated from 10 sets of tomosynthesis projection data of an acrylic slab. The simulated in-plane MTF response of each technique was also combined with the square root of the ENNPS estimate to yield stochastic signal-to-noise ratio (SNR) information about the different reconstruction techniques. Results: For scan angles of 20° and 5 mm plane separation, seven MITS planes must be

  17. The effect of averaging adjacent planes for artifact reduction in matrix inversion tomosynthesis

    Energy Technology Data Exchange (ETDEWEB)

    Godfrey, Devon J. [Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina 27705 (United States); Page McAdams, H. [Carl E. Ravin Advanced Imaging Laboratories, Department of Radiology, Duke University Medical Center, Durham, North Carolina 27705 (United States); Dobbins, James T. III [Carl E. Ravin Advanced Imaging Laboratories, Department of Radiology, Department of Biomedical Engineering, Department of Physics, and Medical Physics Graduate Program, Duke University Medical Center, Durham, North Carolina 27705 (United States)

    2013-02-15

    Purpose: Matrix inversion tomosynthesis (MITS) uses linear systems theory and knowledge of the imaging geometry to remove tomographic blur that is present in conventional backprojection tomosynthesis reconstructions, leaving in-plane detail rendered clearly. The use of partial-pixel interpolation during the backprojection process introduces imprecision in the MITS modeling of tomographic blur, and creates low-contrast artifacts in some MITS planes. This paper examines the use of MITS slabs, created by averaging several adjacent MITS planes, as a method for suppressing partial-pixel artifacts. Methods: Human chest tomosynthesis projection data, acquired as part of an IRB-approved pilot study, were used to generate MITS planes, three-plane MITS slabs (MITSa3), five-plane MITS slabs (MITSa5), and seven-plane MITS slabs (MITSa7). These were qualitatively examined for partial-pixel artifacts and the visibility of normal and abnormal anatomy. Additionally, small (5 mm) subtle pulmonary nodules were simulated and digitally superimposed upon human chest tomosynthesis projection images, and their visibility was qualitatively assessed in the different reconstruction techniques. Simulated images of a thin wire were used to generate modulation transfer function (MTF) and slice-sensitivity profile curves for the different MITS and MITS slab techniques, and these were examined for indications of partial-pixel artifacts and frequency response uniformity. Finally, mean-subtracted, exposure-normalized noise power spectra (ENNPS) estimates were computed and compared for MITS and MITS slab reconstructions, generated from 10 sets of tomosynthesis projection data of an acrylic slab. The simulated in-plane MTF response of each technique was also combined with the square root of the ENNPS estimate to yield stochastic signal-to-noise ratio (SNR) information about the different reconstruction techniques. Results: For scan angles of 20 Degree-Sign and 5 mm plane separation, seven MITS

  18. The effect of averaging adjacent planes for artifact reduction in matrix inversion tomosynthesis.

    Science.gov (United States)

    Godfrey, Devon J; McAdams, H Page; Dobbins, James T

    2013-02-01

    Matrix inversion tomosynthesis (MITS) uses linear systems theory and knowledge of the imaging geometry to remove tomographic blur that is present in conventional backprojection tomosynthesis reconstructions, leaving in-plane detail rendered clearly. The use of partial-pixel interpolation during the backprojection process introduces imprecision in the MITS modeling of tomographic blur, and creates low-contrast artifacts in some MITS planes. This paper examines the use of MITS slabs, created by averaging several adjacent MITS planes, as a method for suppressing partial-pixel artifacts. Human chest tomosynthesis projection data, acquired as part of an IRB-approved pilot study, were used to generate MITS planes, three-plane MITS slabs (MITSa3), five-plane MITS slabs (MITSa5), and seven-plane MITS slabs (MITSa7). These were qualitatively examined for partial-pixel artifacts and the visibility of normal and abnormal anatomy. Additionally, small (5 mm) subtle pulmonary nodules were simulated and digitally superimposed upon human chest tomosynthesis projection images, and their visibility was qualitatively assessed in the different reconstruction techniques. Simulated images of a thin wire were used to generate modulation transfer function (MTF) and slice-sensitivity profile curves for the different MITS and MITS slab techniques, and these were examined for indications of partial-pixel artifacts and frequency response uniformity. Finally, mean-subtracted, exposure-normalized noise power spectra (ENNPS) estimates were computed and compared for MITS and MITS slab reconstructions, generated from 10 sets of tomosynthesis projection data of an acrylic slab. The simulated in-plane MTF response of each technique was also combined with the square root of the ENNPS estimate to yield stochastic signal-to-noise ratio (SNR) information about the different reconstruction techniques. For scan angles of 20° and 5 mm plane separation, seven MITS planes must be averaged to sufficiently

  19. The effect of averaging adjacent planes for artifact reduction in matrix inversion tomosynthesis

    International Nuclear Information System (INIS)

    Godfrey, Devon J.; Page McAdams, H.; Dobbins, James T. III

    2013-01-01

    Purpose: Matrix inversion tomosynthesis (MITS) uses linear systems theory and knowledge of the imaging geometry to remove tomographic blur that is present in conventional backprojection tomosynthesis reconstructions, leaving in-plane detail rendered clearly. The use of partial-pixel interpolation during the backprojection process introduces imprecision in the MITS modeling of tomographic blur, and creates low-contrast artifacts in some MITS planes. This paper examines the use of MITS slabs, created by averaging several adjacent MITS planes, as a method for suppressing partial-pixel artifacts. Methods: Human chest tomosynthesis projection data, acquired as part of an IRB-approved pilot study, were used to generate MITS planes, three-plane MITS slabs (MITSa3), five-plane MITS slabs (MITSa5), and seven-plane MITS slabs (MITSa7). These were qualitatively examined for partial-pixel artifacts and the visibility of normal and abnormal anatomy. Additionally, small (5 mm) subtle pulmonary nodules were simulated and digitally superimposed upon human chest tomosynthesis projection images, and their visibility was qualitatively assessed in the different reconstruction techniques. Simulated images of a thin wire were used to generate modulation transfer function (MTF) and slice-sensitivity profile curves for the different MITS and MITS slab techniques, and these were examined for indications of partial-pixel artifacts and frequency response uniformity. Finally, mean-subtracted, exposure-normalized noise power spectra (ENNPS) estimates were computed and compared for MITS and MITS slab reconstructions, generated from 10 sets of tomosynthesis projection data of an acrylic slab. The simulated in-plane MTF response of each technique was also combined with the square root of the ENNPS estimate to yield stochastic signal-to-noise ratio (SNR) information about the different reconstruction techniques. Results: For scan angles of 20° and 5 mm plane separation, seven MITS planes must be

  20. The Effect of Susceptibility Artifacts Related to Metallic Implants on Adjacent-Lesion Assessment in Simultaneous TOF PET/MR.

    Science.gov (United States)

    Svirydenka, Hanna; Delso, Gaspar; De Galiza Barbosa, Felipe; Huellner, Martin; Davison, Helen; Fanti, Stefano; Veit-Haibach, Patrick; Ter Voert, Edwin E G W

    2017-07-01

    Metalic implants may affect attenuation correction (AC) in PET/MR imaging. The purpose of this study was to evaluate the effect of susceptibility artifacts related to metallic implants on adjacent metabolically active lesions in clinical simultaneous PET/MR scanning for both time-of-flight (TOF) and non-TOF reconstructed PET images. Methods: We included 27 patients without implants but with confirmed 18 F-FDG-avid lesions adjacent to common implant locations. In all patients, a clinically indicated whole-body 18 F-FDG PET/MR scan was acquired. Baseline non-TOF and TOF PET images were reconstructed. Reconstruction was repeated after the introduction of artificial signal voids in the AC map to simulate metallic implants in standard anatomic areas. All reconstructed images were qualitatively and quantitatively assessed and compared with the baseline images. Results: In total, 51 lesions were assessed. In 40 and 50 of these cases (non-TOF and TOF, respectively), the detectability of the lesions did not change; in 9 and 1 cases, the detectability changed; and in 2 non-TOF cases, the lesions were no longer visible after the introduction of metallic artifacts. The inclusion of TOF information significantly reduced artifacts due to simulated implants in the femoral head, sternum, and spine ( P = 0.01, 0.01, and 0.03, respectively). It also improved image quality in these locations ( P = 0.02, 0.01, and 0.01, respectively). The mean percentage error was -3.5% for TOF and -4.8% for non-TOF reconstructions, meaning that the inclusion of TOF information reduced the percentage error in SUV max by 28.5% ( P metallic implants have a significant effect on small, moderately 18 F-FDG-avid lesions near the implant site that possibly may go unnoticed without TOF information. On larger, highly 18 F-FDG-avid lesions, the metallic implants had only a limited effect. The largest significant quantitative difference was found in artifacts of the sternum. There was only a weak inverse

  1. Three-dimensional digital tomosynthesis iterative reconstruction, artifact reduction and alternative acquisition geometry

    CERN Document Server

    Levakhina, Yulia

    2014-01-01

    Yulia Levakhina gives an introduction to the major challenges of image reconstruction in Digital Tomosynthesis (DT), particularly to the connection of the reconstruction problem with the incompleteness of the DT dataset. The author discusses the factors which cause the formation of limited angle artifacts and proposes how to account for them in order to improve image quality and axial resolution of modern DT. The addressed methods include a weighted non-linear back projection scheme for algebraic reconstruction and?novel dual-axis acquisition geometry. All discussed algorithms and methods are supplemented by detailed illustrations, hints for practical implementation, pseudo-code, simulation results and real patient case examples.

  2. Contaminated metallic melt volume reduction testing

    International Nuclear Information System (INIS)

    Deichman, J.L.

    1981-01-01

    Laboratory scale metallic melts (stainless steel) were accomplished in support of Decontamination and Decommissioning's (D and D) contaminated equipment volume reduction and Low-Level Lead Site Waste programs. Six laboratory scale melts made with contaminated stainless steel provided data that radionuclide distribution can be predicted when proper temperature rates and ranges are employed, and that major decontamination occurs with the use of designed slagging materials. Stainless steel bars were contaminated with plutonium, cobalt, cesium and europium. This study was limited to stainless steel, however, further study is desirable to establish data for other metals and alloys. This study represents a positive beginning in defining the feasibility of economical volume reduction or conversion from TRU waste forms to LLW forms for a large portion of approximately 50 thousand tons of contaminated metal waste now being stored at Hanford underground or in deactivated facilities

  3. Evaluation of metal artifacts in MVCT systems using a model based correction method

    Energy Technology Data Exchange (ETDEWEB)

    Paudel, M. R.; Mackenzie, M.; Fallone, B. G.; Rathee, S. [Department of Oncology, Medical Physics Division, University of Alberta, 11560 University Avenue, Edmonton, Alberta T6G 1Z2 (Canada); Department of Medical Physics, Cross Cancer Institute, 11560 University Avenue, Edmonton, Alberta T6G 1Z2 (Canada) and Department of Oncology, Medical Physics Division, University of Alberta, 11560 University Avenue, Edmonton, Alberta T6G 1Z2 (Canada); Department of Physics, University of Alberta, 11322-89 Avenue, Edmonton, Alberta T6G 2G7 (Canada); Department of Medical Physics, Cross Cancer Institute, 11560 University Avenue, Edmonton, Alberta T6G 1Z2 (Canada) and Department of Oncology, Medical Physics Division, University of Alberta, 11560 University Avenue, Edmonton, Alberta T6G 1Z2 (Canada); Department of Medical Physics, Cross Cancer Institute, 11560 University Avenue, Edmonton, Alberta T6G 1Z2 (Canada) and Department of Oncology, Medical Physics Division, University of Alberta, 11560 University Avenue, Edmonton, Alberta T6G 1Z2 (Canada)

    2012-10-15

    Purpose: To evaluate the performance of a model based image reconstruction method in reducing metal artifacts in the megavoltage computed tomography (MVCT) images of a phantom representing bilateral hip prostheses and to compare with the filtered-backprojection (FBP) technique. Methods: An iterative maximum likelihood polychromatic algorithm for CT (IMPACT) is used with an additional model for the pair/triplet production process and the energy dependent response of the detectors. The beam spectra for an in-house bench-top and TomoTherapy Trade-Mark-Sign MVCTs are modeled for use in IMPACT. The empirical energy dependent response of detectors is calculated using a constrained optimization technique that predicts the measured attenuation of the beam by various thicknesses (0-24 cm) of solid water slabs. A cylindrical (19.1 cm diameter) plexiglass phantom containing various cylindrical inserts of relative electron densities 0.295-1.695 positioned between two steel rods (2.7 cm diameter) is scanned in the bench-top MVCT that utilizes the bremsstrahlung radiation from a 6 MeV electron beam passed through 4 cm solid water on the Varian Clinac 2300C and in the imaging beam of the TomoTherapy Trade-Mark-Sign MVCT. The FBP technique in bench-top MVCT reconstructs images from raw signal normalized to air scan and corrected for beam hardening using a uniform plexiglass cylinder (20 cm diameter). The IMPACT starts with a FBP reconstructed seed image and reconstructs the final image in 150 iterations. Results: In both MVCTs, FBP produces visible dark shading in the image connecting the steel rods. In the IMPACT reconstructed images this shading is nearly removed and the uniform background is restored. The average attenuation coefficients of the inserts and the background are very close to the corresponding values in the absence of the steel inserts. In the FBP images of the bench-top MVCT, the shading causes 4%-9.5% underestimation of electron density at the central inserts

  4. Metal artifact suppression at the hip: diagnostic performance at 3.0 T versus 1.5 Tesla

    Energy Technology Data Exchange (ETDEWEB)

    Nardo, Lorenzo; Han, Misung; Kretschmar, Martin; Krug, Roland; Link, Thomas M. [University of California San Francisco, Musculoskeletal and Quantitative Imaging Research, Department of Radiology and Biomedical Imaging, San Francisco, CA (United States); Guindani, Michele [The University of Texas MD Anderson Cancer Center, Department of Biostatistics - Unit 1411, Houston, TX (United States); Koch, Kevin [Medical College of Wisconsin, Department of Biophysics, Milwaukee, WI (United States); Medical College of Wisconsin, Department of Radiology, Milwaukee, WI (United States); Vail, Thomas [University of California San Francisco, Department of Orthopedic Surgery, San Francisco, CA (United States)

    2015-11-15

    This work aimed to compare the diagnostic performance of a metal artifact suppression sequence (MAVRIC-SL) for imaging of hip arthroplasties (HA) at 1.5 and 3 Tesla (T) field strength. Eighteen patients (10 females; aged 27-74) with HA were examined at 3.0 and 1.5 T within 3 weeks. The sequence protocol included 3D-MAVRIC-SL PD (coronal), 3D-MAVRIC-SL STIR (axial), FSE T1, FSE PD and STIR sequences. Anatomical structures and pathological findings were assessed independently by two radiologists. Artifact extent and technical quality (image quality, fat saturation and geometric distortion) were also evaluated. Findings at 1.5 and 3.0 T were compared using a Wilcoxon signed rank test. While image quality was better at 1.5 T, visualization of anatomic structures and clinical abnormalities was not significantly different using the two field strengths (p > 0.05). Fat suppression and amount of artifacts were significantly better at 1.5 T (p < 0.01). Inter- and intra-reader agreement for different anatomic details, image quality and visualization of abnormalities ranged from k = 0.62 to k = 1.00. MAVRIC-SL at 1.5 T had a comparable diagnostic performance when compared MAVRIC-SL at 3.0 T; however, the higher field strength was associated with larger artifacts, limited image quality and worse fat saturation. (orig.)

  5. Metal artifact suppression at the hip: diagnostic performance at 3.0 T versus 1.5 Tesla

    International Nuclear Information System (INIS)

    Nardo, Lorenzo; Han, Misung; Kretschmar, Martin; Krug, Roland; Link, Thomas M.; Guindani, Michele; Koch, Kevin; Vail, Thomas

    2015-01-01

    This work aimed to compare the diagnostic performance of a metal artifact suppression sequence (MAVRIC-SL) for imaging of hip arthroplasties (HA) at 1.5 and 3 Tesla (T) field strength. Eighteen patients (10 females; aged 27-74) with HA were examined at 3.0 and 1.5 T within 3 weeks. The sequence protocol included 3D-MAVRIC-SL PD (coronal), 3D-MAVRIC-SL STIR (axial), FSE T1, FSE PD and STIR sequences. Anatomical structures and pathological findings were assessed independently by two radiologists. Artifact extent and technical quality (image quality, fat saturation and geometric distortion) were also evaluated. Findings at 1.5 and 3.0 T were compared using a Wilcoxon signed rank test. While image quality was better at 1.5 T, visualization of anatomic structures and clinical abnormalities was not significantly different using the two field strengths (p > 0.05). Fat suppression and amount of artifacts were significantly better at 1.5 T (p < 0.01). Inter- and intra-reader agreement for different anatomic details, image quality and visualization of abnormalities ranged from k = 0.62 to k = 1.00. MAVRIC-SL at 1.5 T had a comparable diagnostic performance when compared MAVRIC-SL at 3.0 T; however, the higher field strength was associated with larger artifacts, limited image quality and worse fat saturation. (orig.)

  6. Partial scan artifact reduction (PSAR) for the assessment of cardiac perfusion in dynamic phase-correlated CT.

    Science.gov (United States)

    Stenner, Philip; Schmidt, Bernhard; Bruder, Herbert; Allmendinger, Thomas; Haberland, Ulrike; Flohr, Thomas; Kachelriess, Marc

    2009-12-01

    Cardiac CT achieves its high temporal resolution by lowering the scan range from 2pi to pi plus fan angle (partial scan). This, however, introduces CT-value variations, depending on the angular position of the pi range. These partial scan artifacts are of the order of a few HU and prevent the quantitative evaluation of perfusion measurements. The authors present the new algorithm partial scan artifact reduction (PSAR) that corrects a dynamic phase-correlated scan without a priori information. In general, a full scan does not suffer from partial scan artifacts since all projections in [0, 2pi] contribute to the data. To maintain the optimum temporal resolution and the phase correlation, PSAR creates an artificial full scan pn(AF) by projectionwise averaging a set of neighboring partial scans pn(P) from the same perfusion examination (typically N approximately 30 phase-correlated partial scans distributed over 20 s and n = 1, ..., N). Corresponding to the angular range of each partial scan, the authors extract virtual partial scans pn(V) from the artificial full scan pn(AF). A standard reconstruction yields the corresponding images fn(P), fn(AF), and fn(V). Subtracting the virtual partial scan image fn(V) from the artificial full scan image fn(AF) yields an artifact image that can be used to correct the original partial scan image: fn(C) = fn(P) - fn(V) + fn(AF), where fn(C) is the corrected image. The authors evaluated the effects of scattered radiation on the partial scan artifacts using simulated and measured water phantoms and found a strong correlation. The PSAR algorithm has been validated with a simulated semianthropomorphic heart phantom and with measurements of a dynamic biological perfusion phantom. For the stationary phantoms, real full scans have been performed to provide theoretical reference values. The improvement in the root mean square errors between the full and the partial scans with respect to the errors between the full and the corrected scans is

  7. Partial scan artifact reduction (PSAR) for the assessment of cardiac perfusion in dynamic phase-correlated CT

    Energy Technology Data Exchange (ETDEWEB)

    Stenner, Philip; Schmidt, Bernhard; Bruder, Herbert; Allmendinger, Thomas; Haberland, Ulrike; Flohr, Thomas; Kachelriess, Marc [Institute of Medical Physics, Henkestrasse 91, 91052 Erlangen (Germany); Siemens AG, Healthcare Sector, Siemensstrasse 1, 91301 Forchheim (Germany); Institute of Medical Physics, Henkestrasse. 91, 91052 Erlangen (Germany)

    2009-12-15

    Purpose: Cardiac CT achieves its high temporal resolution by lowering the scan range from 2{pi} to {pi} plus fan angle (partial scan). This, however, introduces CT-value variations, depending on the angular position of the {pi} range. These partial scan artifacts are of the order of a few HU and prevent the quantitative evaluation of perfusion measurements. The authors present the new algorithm partial scan artifact reduction (PSAR) that corrects a dynamic phase-correlated scan without a priori information. Methods: In general, a full scan does not suffer from partial scan artifacts since all projections in [0, 2{pi}] contribute to the data. To maintain the optimum temporal resolution and the phase correlation, PSAR creates an artificial full scan p{sub n}{sup AF} by projectionwise averaging a set of neighboring partial scans p{sub n}{sup P} from the same perfusion examination (typically N{approx_equal}30 phase-correlated partial scans distributed over 20 s and n=1,...,N). Corresponding to the angular range of each partial scan, the authors extract virtual partial scans p{sub n}{sup V} from the artificial full scan p{sub n}{sup AF}. A standard reconstruction yields the corresponding images f{sub n}{sup P}, f{sub n}{sup AF}, and f{sub n}{sup V}. Subtracting the virtual partial scan image f{sub n}{sup V} from the artificial full scan image f{sub n}{sup AF} yields an artifact image that can be used to correct the original partial scan image: f{sub n}{sup C}=f{sub n}{sup P}-f{sub n}{sup V}+f{sub n}{sup AF}, where f{sub n}{sup C} is the corrected image. Results: The authors evaluated the effects of scattered radiation on the partial scan artifacts using simulated and measured water phantoms and found a strong correlation. The PSAR algorithm has been validated with a simulated semianthropomorphic heart phantom and with measurements of a dynamic biological perfusion phantom. For the stationary phantoms, real full scans have been performed to provide theoretical reference

  8. Adaptive non-local means on local principle neighborhood for noise/artifacts reduction in low-dose CT images.

    Science.gov (United States)

    Zhang, Yuanke; Lu, Hongbing; Rong, Junyan; Meng, Jing; Shang, Junliang; Ren, Pinghong; Zhang, Junying

    2017-09-01

    Low-dose CT (LDCT) technique can reduce the x-ray radiation exposure to patients at the cost of degraded images with severe noise and artifacts. Non-local means (NLM) filtering has shown its potential in improving LDCT image quality. However, currently most NLM-based approaches employ a weighted average operation directly on all neighbor pixels with a fixed filtering parameter throughout the NLM filtering process, ignoring the non-stationary noise nature of LDCT images. In this paper, an adaptive NLM filtering scheme on local principle neighborhoods (PC-NLM) is proposed for structure-preserving noise/artifacts reduction in LDCT images. Instead of using neighboring patches directly, in the PC-NLM scheme, the principle component analysis (PCA) is first applied on local neighboring patches of the target patch to decompose the local patches into uncorrelated principle components (PCs), then a NLM filtering is used to regularize each PC of the target patch and finally the regularized components is transformed to get the target patch in image domain. Especially, in the NLM scheme, the filtering parameter is estimated adaptively from local noise level of the neighborhood as well as the signal-to-noise ratio (SNR) of the corresponding PC, which guarantees a "weaker" NLM filtering on PCs with higher SNR and a "stronger" filtering on PCs with lower SNR. The PC-NLM procedure is iteratively performed several times for better removal of the noise and artifacts, and an adaptive iteration strategy is developed to reduce the computational load by determining whether a patch should be processed or not in next round of the PC-NLM filtering. The effectiveness of the presented PC-NLM algorithm is validated by experimental phantom studies and clinical studies. The results show that it can achieve promising gain over some state-of-the-art methods in terms of artifact suppression and structure preservation. With the use of PCA on local neighborhoods to extract principal structural

  9. Partial scan artifact reduction (PSAR) for the assessment of cardiac perfusion in dynamic phase-correlated CT

    International Nuclear Information System (INIS)

    Stenner, Philip; Schmidt, Bernhard; Bruder, Herbert; Allmendinger, Thomas; Haberland, Ulrike; Flohr, Thomas; Kachelriess, Marc

    2009-01-01

    Purpose: Cardiac CT achieves its high temporal resolution by lowering the scan range from 2π to π plus fan angle (partial scan). This, however, introduces CT-value variations, depending on the angular position of the π range. These partial scan artifacts are of the order of a few HU and prevent the quantitative evaluation of perfusion measurements. The authors present the new algorithm partial scan artifact reduction (PSAR) that corrects a dynamic phase-correlated scan without a priori information. Methods: In general, a full scan does not suffer from partial scan artifacts since all projections in [0, 2π] contribute to the data. To maintain the optimum temporal resolution and the phase correlation, PSAR creates an artificial full scan p n AF by projectionwise averaging a set of neighboring partial scans p n P from the same perfusion examination (typically N≅30 phase-correlated partial scans distributed over 20 s and n=1,...,N). Corresponding to the angular range of each partial scan, the authors extract virtual partial scans p n V from the artificial full scan p n AF . A standard reconstruction yields the corresponding images f n P , f n AF , and f n V . Subtracting the virtual partial scan image f n V from the artificial full scan image f n AF yields an artifact image that can be used to correct the original partial scan image: f n C =f n P -f n V +f n AF , where f n C is the corrected image. Results: The authors evaluated the effects of scattered radiation on the partial scan artifacts using simulated and measured water phantoms and found a strong correlation. The PSAR algorithm has been validated with a simulated semianthropomorphic heart phantom and with measurements of a dynamic biological perfusion phantom. For the stationary phantoms, real full scans have been performed to provide theoretical reference values. The improvement in the root mean square errors between the full and the partial scans with respect to the errors between the full and the

  10. Artifact reduction method in ultrasound-guided diffuse optical tomography using exogenous contrast agents

    Science.gov (United States)

    Ardeshirpour, Yasaman; Biswal, Nrusingh; Aguirre, Andres; Zhu, Quing

    2011-04-01

    In diffuse optical tomography (DOT), a typical perturbation approach requires two sets of measurements obtained at the lesion breast (lesion or target site) and a contra-lateral location of the normal breast (reference site) for image reconstruction. For patients who have a small amount of breast tissue, the chest-wall underneath the breast tissue at both sites affects the imaging results. In this group of patients, the perturbation, which is the difference between measurements obtained at the lesion and reference sites, may include the information of background mismatch which can generate artifacts or affect the reconstructed quantitative absorption coefficient of the lesion. Also, for patients who have a single breast due to prior surgery, the contra-lateral reference is not available. To improve the DOT performance or overcome its limitation, we introduced a new method based on an exogenous contrast agent and demonstrate its performance using animal models. Co-registered ultrasound was used to guide the lesion localization. The results have shown that artifacts caused by background mismatch can be reduced significantly by using this new method.

  11. Noise Reduction Potential of Cellular Metals

    Directory of Open Access Journals (Sweden)

    Björn Hinze

    2012-06-01

    Full Text Available Rising numbers of flights and aircrafts cause increasing aircraft noise, resulting in the development of various approaches to change this trend. One approach is the application of metallic liners in the hot gas path of aero-engines. At temperatures of up to 600 °C only metallic or ceramic structures can be used. Due to fatigue loading and the notch effect of the pores, mechanical properties of porous metals are superior to the ones of ceramic structures. Consequently, cellular metals like metallic foams, sintered metals, or sintered metal felts are most promising materials. However, acoustic absorption depends highly on pore morphology and porosity. Therefore, both parameters must be characterized precisely to analyze the correlation between morphology and noise reduction performance. The objective of this study is to analyze the relationship between pore morphology and acoustic absorption performance. The absorber materials are characterized using image processing based on two dimensional microscopy images. The sound absorption properties are measured using an impedance tube. Finally, the correlation of acoustic behavior, pore morphology, and porosity is outlined.

  12. Simultaneous Reduction in Noise and Cross-Contamination Artifacts for Dual-Energy X-Ray CT

    Directory of Open Access Journals (Sweden)

    Baojun Li

    2013-01-01

    Full Text Available Purpose. Dual-energy CT imaging tends to suffer from much lower signal-to-noise ratio than single-energy CT. In this paper, we propose an improved anticorrelated noise reduction (ACNR method without causing cross-contamination artifacts. Methods. The proposed algorithm diffuses both basis material density images (e.g., water and iodine at the same time using a novel correlated diffusion algorithm. The algorithm has been compared to the original ACNR algorithm in a contrast-enhanced, IRB-approved patient study. Material density accuracy and noise reduction are quantitatively evaluated by the percent density error and the percent noise reduction. Results. Both algorithms have significantly reduced the noises of basis material density images in all cases. The average percent noise reduction is 69.3% and 66.5% with the ACNR algorithm and the proposed algorithm, respectively. However, the ACNR algorithm alters the original material density by an average of 13% (or 2.18 mg/cc with a maximum of 58.7% (or 8.97 mg/cc in this study. This is evident in the water density images as massive cross-contaminations are seen in all five clinical cases. On the contrary, the proposed algorithm only changes the mean density by 2.4% (or 0.69 mg/cc with a maximum of 7.6% (or 1.31 mg/cc. The cross-contamination artifacts are significantly minimized or absent with the proposed algorithm. Conclusion. The proposed algorithm can significantly reduce image noise present in basis material density images from dual-energy CT imaging, with minimized cross-contaminations compared to the ACNR algorithm.

  13. The reduction of motion artifacts in digital subtraction angiography by geometrical image transformation

    International Nuclear Information System (INIS)

    Fitzpatrick, J.M.; Pickens, D.R.; Mandava, V.R.; Grefenstette, J.J.

    1988-01-01

    In the diagnosis of arteriosclerosis, radio-opaque dye is injected into the interior of the arteries to make them visible. Because of its increased contrast sensitivity, digital subtraction angiography has the potential for providing diagnostic images of arteries with reduced dye volumes. In the conventional technique, a mask image, acquired before the introduction of the dye, is subtracted from the contrast image, acquired after the dye is introduced, to produce a difference image in which only the dye in the arteries is visible. The usefulness of this technique has been severely limited by the image degradation caused by patient motion during image acquisition. This motion produces artifacts in the difference image that obscure the arteries. One technique for dealing with the problem is to reduce the degradation by means of image registration. The registration is carried out by means of a geometrical transformation of the mask image before subtraction so that it is in registration with the contrast image. This paper describes a technique for determining an optimal transformation. The authors employ a one-to-one elastic mapping and the Jacobian of that mapping to produce a geometrical image transformation. They choose a parameterized class of such mappings and use a heuristic search algorithm to optimize the parameters to minimize the severity of the motion artifacts. To increase the speed of the optimization process they use a statistical image comparison technique that provides a quick approximate evaluation of each image transformation. They present the experimental results of the application of their registration system to mask-contrast pairs, for images acquired from a specially designed phantom, and for clinical images

  14. Metallic artifacts caused by dental metal prostheses on PET images. A PET/CT phantom study using different PET/CT scanners

    International Nuclear Information System (INIS)

    Shimamoto, Hiroaki; Kakimoto, Naoya; Murakami, Shumei; Furukawa, Souhei; Fujino, Kouichi; Hamada, Seiki; Shimosegawa, Eku; Hatazawa, Jun

    2009-01-01

    The objective of this study was to investigate the effects of computed tomography (CT) artifacts caused by dental metal prostheses on positron emission tomography (PET) images. A dental arch cast was fixed in a cylindrical water-bath phantom. A spherical phantom positioned in the vicinity of the dental arch cast was used to simulate a tumor. To simulate the tumor imaging, the ratio of the 18 F-fluoro-deoxy-glucose radioactivity concentration of the spherical phantom to that of the water-bath phantom was set at 2.5. A dental bridge composed of a gold-silver-palladium alloy on the right mandibular side was prepared. A spherical phantom was set in the white artifact area on the CT images (site A), in a slightly remote area from the white artifact (site B), and in a black artifact area (site C). A PET/CT scan was performed with and without the metal bridge at each simulated tumor site, and the artifactual influence was evaluated on the axial attenuation-corrected (AC) PET images, in which the simulated tumor produced the strongest accumulation. Measurements were performed using three types of PET/CT scanners (scanners 1 and 2 with CT-based attenuation correction, and 3 with Cesium-137 ( 137 Cs)-based attenuation correction). The influence of the metal bridge was evaluated using the change rate of the SUVmean with and without the metal bridge. At site A, an overestimation was shown (scanner 1: +5.0% and scanner 2: +2.5%), while scanner 3 showed an underestimation of -31.8%. At site B, an overestimation was shown (scanner 1: +2.1% and scanner 2: +2.0%), while scanner 3 showed an underestimation of -2.6%. However, at site C, an underestimation was shown (scanner 1: -25.0%, scanner 2: -32.4%, and scanner 3: -8.4%). When CT is used for attenuation correction in patients with dental metal prostheses, an underestimation of radioactivity of accumulated tracer is anticipated in the dark streak artifact area on the CT images. In this study, the dark streak artifacts of the CT

  15. Closed-Loop Control of Humidification for Artifact Reduction in Capacitive ECG Measurements.

    Science.gov (United States)

    Leicht, Lennart; Eilebrecht, Benjamin; Weyer, Soren; Leonhardt, Steffen; Teichmann, Daniel

    2017-04-01

    Recording biosignals without the need for direct skin contact offers new opportunities for ubiquitous health monitoring. Electrodes with capacitive coupling have been shown to be suitable for the monitoring of electrical potentials on the body surface, in particular ECG. However, due to triboelectric charge generation and motion artifacts, signal and thus diagnostic quality is inferior to galvanic coupling. Active closed-loop humidification of capacitive electrodes is proposed in this work as a new concept to improve signal quality. A capacitive ECG recording system integrated into a common car seat is presented. It can regulate the micro climate at the interface of electrode and patient by actively dispensing water vapour and monitoring humidity in a closed-loop approach. As a regenerative water reservoir, silica gel is used. The system was evaluated with respect to subjective and objective ECG signal quality. Active humidification was found to have a significant positive effect in case of previously poor quality. Also, it had no diminishing effect in case of already good signal quality.

  16. Low-Gain, Low-Noise Integrated Neuronal Amplifier for Implantable Artifact-Reduction Recording System

    Directory of Open Access Journals (Sweden)

    Abdelhamid Benazzouz

    2013-09-01

    Full Text Available Brain neuroprostheses for neuromodulation are being designed to monitor the neural activity of the brain in the vicinity of the region being stimulated using a single macro-electrode. Using a single macro-electrode, recent neuromodulation studies show that recording systems with a low gain neuronal amplifier and successive amplifier stages can reduce or reject stimulation artifacts. These systems were made with off-the-shelf components that are not amendable for future implant design. A low-gain, low-noise integrated neuronal amplifier (NA with the capability of recording local field potentials (LFP and spike activity is presented. In vitro and in vivo characterizations of the tissue/electrode interface, with equivalent impedance as an electrical model for recording in the LFP band using macro-electrodes for rodents, contribute to the NA design constraints. The NA occupies 0.15 mm2 and dissipates 6.73 µW, and was fabricated using a 0.35 µm CMOS process. Test-bench validation indicates that the NA provides a mid-band gain of 20 dB and achieves a low input-referred noise of 4 µVRMS. Ability of the NA to perform spike recording in test-bench experiments is presented. Additionally, an awake and freely moving rodent setup was used to illustrate the integrated NA ability to record LFPs, paving the pathway for future implantable systems for neuromodulation.

  17. Hybrid PET/MR imaging: an algorithm to reduce metal artifacts from dental implants in Dixon-based attenuation map generation using a multiacquisition variable-resonance image combination sequence.

    Science.gov (United States)

    Burger, Irene A; Wurnig, Moritz C; Becker, Anton S; Kenkel, David; Delso, Gaspar; Veit-Haibach, Patrick; Boss, Andreas

    2015-01-01

    It was the aim of this study to implement an algorithm modifying Dixon-based MR imaging datasets for attenuation correction in hybrid PET/MR imaging with a multiacquisition variable resonance image combination (MAVRIC) sequence to reduce metal artifacts. After ethics approval, in 8 oncologic patients with dental implants data were acquired in a trimodality setup with PET/CT and MR imaging. The protocol included a whole-body 3-dimensional dual gradient-echo sequence (Dixon) used for MR imaging-based PET attenuation correction and a high-resolution MAVRIC sequence, applied in the oral area compromised by dental implants. An algorithm was implemented correcting the Dixon-based μ maps using the MAVRIC in areas of Dixon signal voids. The artifact size of the corrected μ maps was compared with the uncorrected MR imaging μ maps. The algorithm was robust in all patients. There was a significant reduction in mean artifact size of 70.5% between uncorrected and corrected μ maps from 697 ± 589 mm(2) to 202 ± 119 mm(2) (P = 0.016). The proposed algorithm could improve MR imaging-based attenuation correction in critical areas, when standard attenuation correction is hampered by metal artifacts, using a MAVRIC. © 2015 by the Society of Nuclear Medicine and Molecular Imaging, Inc.

  18. Comparison of the artifacts caused by metallic implants in breast MRI using dual-echo dixon versus conventional fat-suppression techniques.

    Science.gov (United States)

    Le, Yuan; Kipfer, Hal D; Majidi, Shadie S; Holz, Stephanie; Lin, Chen

    2014-09-01

    The purpose of this article is to evaluate and compare the artifacts caused by metal implants in breast MR images acquired with dual-echo Dixon and two conventional fat-suppression techniques. Two types of biopsy markers were embedded into a uniform fat-water emulsion. T1-weighted gradient-echo images were acquired on a clinical 3-T MRI scanner with three different fat-suppression techniques-conventional or quick fat saturation, spectrally selective adiabatic inversion recovery (SPAIR), and dual-echo Dixon-and the 3D volumes of artifacts were measured. Among the subjects of a clinical breast MRI study using the same scanner, five patients were found to have one or more metal implants. The artifacts in Dixon and SPAIR fat-suppressed images were evaluated by three radiologists, and the results were compared with those of the phantom study. In the phantom study, the artifacts appeared as interleaved bright and dark rings on SPAIR and quick-fat-saturation images, whereas they appeared as dark regions with a thin bright rim on Dixon images. The artifacts imaged with the Dixon technique had the smallest total volume. However, the reviewers found larger artifact diameters on patient images using the Dixon sequence because only the central region was recognized as an artifact on the SPAIR images. Metal implants introduce artifacts of different types and sizes, according to the different fat-suppression techniques used. The dual-echo Dixon technique produces a larger central void, allowing the implant to be easily identified, but presents a smaller overall artifact volume by obscuring less area in the image, according to a quantitative phantom study.

  19. Metal artifact correction for x-ray computed tomography using kV and selective MV imaging

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Meng, E-mail: mengwu@stanford.edu [Department of Electrical Engineering, Stanford University, Stanford, California 94305 (United States); Keil, Andreas [microDimensions GmbH, Munich 81379 (Germany); Constantin, Dragos; Star-Lack, Josh [Varian Medical Systems, Inc., Palo Alto, California 94304 (United States); Zhu, Lei [Nuclear and Radiological Engineering and Medical Physics Programs, The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States); Fahrig, Rebecca [Department of Radiology, Stanford University, Stanford, California 94305 (United States)

    2014-12-15

    Purpose: The overall goal of this work is to improve the computed tomography (CT) image quality for patients with metal implants or fillings by completing the missing kilovoltage (kV) projection data with selectively acquired megavoltage (MV) data that do not suffer from photon starvation. When both of these imaging systems, which are available on current radiotherapy devices, are used, metal streak artifacts are avoided, and the soft-tissue contrast is restored, even for regions in which the kV data cannot contribute any information. Methods: Three image-reconstruction methods, including two filtered back-projection (FBP)-based analytic methods and one iterative method, for combining kV and MV projection data from the two on-board imaging systems of a radiotherapy device are presented in this work. The analytic reconstruction methods modify the MV data based on the information in the projection or image domains and then patch the data onto the kV projections for a FBP reconstruction. In the iterative reconstruction, the authors used dual-energy (DE) penalized weighted least-squares (PWLS) methods to simultaneously combine the kV/MV data and perform the reconstruction. Results: The authors compared kV/MV reconstructions to kV-only reconstructions using a dental phantom with fillings and a hip-implant numerical phantom. Simulation results indicated that dual-energy sinogram patch FBP and the modified dual-energy PWLS method can successfully suppress metal streak artifacts and restore information lost due to photon starvation in the kV projections. The root-mean-square errors of soft-tissue patterns obtained using combined kV/MV data are 10–15 Hounsfield units smaller than those of the kV-only images, and the structural similarity index measure also indicates a 5%–10% improvement in the image quality. The added dose from the MV scan is much less than the dose from the kV scan if a high efficiency MV detector is assumed. Conclusions: The authors have shown that it

  20. Metal artifact correction for x-ray computed tomography using kV and selective MV imaging

    International Nuclear Information System (INIS)

    Wu, Meng; Keil, Andreas; Constantin, Dragos; Star-Lack, Josh; Zhu, Lei; Fahrig, Rebecca

    2014-01-01

    Purpose: The overall goal of this work is to improve the computed tomography (CT) image quality for patients with metal implants or fillings by completing the missing kilovoltage (kV) projection data with selectively acquired megavoltage (MV) data that do not suffer from photon starvation. When both of these imaging systems, which are available on current radiotherapy devices, are used, metal streak artifacts are avoided, and the soft-tissue contrast is restored, even for regions in which the kV data cannot contribute any information. Methods: Three image-reconstruction methods, including two filtered back-projection (FBP)-based analytic methods and one iterative method, for combining kV and MV projection data from the two on-board imaging systems of a radiotherapy device are presented in this work. The analytic reconstruction methods modify the MV data based on the information in the projection or image domains and then patch the data onto the kV projections for a FBP reconstruction. In the iterative reconstruction, the authors used dual-energy (DE) penalized weighted least-squares (PWLS) methods to simultaneously combine the kV/MV data and perform the reconstruction. Results: The authors compared kV/MV reconstructions to kV-only reconstructions using a dental phantom with fillings and a hip-implant numerical phantom. Simulation results indicated that dual-energy sinogram patch FBP and the modified dual-energy PWLS method can successfully suppress metal streak artifacts and restore information lost due to photon starvation in the kV projections. The root-mean-square errors of soft-tissue patterns obtained using combined kV/MV data are 10–15 Hounsfield units smaller than those of the kV-only images, and the structural similarity index measure also indicates a 5%–10% improvement in the image quality. The added dose from the MV scan is much less than the dose from the kV scan if a high efficiency MV detector is assumed. Conclusions: The authors have shown that it

  1. Metal artifact correction for x-ray computed tomography using kV and selective MV imaging.

    Science.gov (United States)

    Wu, Meng; Keil, Andreas; Constantin, Dragos; Star-Lack, Josh; Zhu, Lei; Fahrig, Rebecca

    2014-12-01

    The overall goal of this work is to improve the computed tomography (CT) image quality for patients with metal implants or fillings by completing the missing kilovoltage (kV) projection data with selectively acquired megavoltage (MV) data that do not suffer from photon starvation. When both of these imaging systems, which are available on current radiotherapy devices, are used, metal streak artifacts are avoided, and the soft-tissue contrast is restored, even for regions in which the kV data cannot contribute any information. Three image-reconstruction methods, including two filtered back-projection (FBP)-based analytic methods and one iterative method, for combining kV and MV projection data from the two on-board imaging systems of a radiotherapy device are presented in this work. The analytic reconstruction methods modify the MV data based on the information in the projection or image domains and then patch the data onto the kV projections for a FBP reconstruction. In the iterative reconstruction, the authors used dual-energy (DE) penalized weighted least-squares (PWLS) methods to simultaneously combine the kV/MV data and perform the reconstruction. The authors compared kV/MV reconstructions to kV-only reconstructions using a dental phantom with fillings and a hip-implant numerical phantom. Simulation results indicated that dual-energy sinogram patch FBP and the modified dual-energy PWLS method can successfully suppress metal streak artifacts and restore information lost due to photon starvation in the kV projections. The root-mean-square errors of soft-tissue patterns obtained using combined kV/MV data are 10-15 Hounsfield units smaller than those of the kV-only images, and the structural similarity index measure also indicates a 5%-10% improvement in the image quality. The added dose from the MV scan is much less than the dose from the kV scan if a high efficiency MV detector is assumed. The authors have shown that it is possible to improve the image quality of

  2. Effect of Metal Artifacts on Detection of Vertical Root Fractures Using Two Cone Beam Computed Tomography Systems.

    Science.gov (United States)

    Safi, Yaser; Aghdasi, Mohammad Mehdi; Ezoddini-Ardakani, Fatemeh; Beiraghi, Samira; Vasegh, Zahra

    2015-01-01

    Vertical root fracture (VRF) is common in endodontically treated teeth. Conventional and digital radiographies have limitations for detection of VRFs. Cone-beam computed tomography (CBCT) offers greater detection accuracy of VRFs in comparison with conventional radiography. This study compared the effects of metal artifacts on detection of VRFs by using two CBCT systems. Eighty extracted premolars were selected and sectioned at the level of the cemento enamel junction (CEJ). After preparation, root canals were filled with gutta-percha. Subsequently, two thirds of the root fillings were removed for post space preparation and a custom-made post was cemented into each canal. The teeth were randomly divided into two groups (n=40). In the test group, root fracture was created with Instron universal testing machine. The control teeth remained intact. CBCT scans of all teeth were obtained with either New Tom VGI or Soredex Scanora 3D. Three observers analyzed the images for detection of VRF. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) for VRF detection and percentage of probable cases were calculated for each imaging system and compared using non-parametric tests considering the non-normal distribution of data. The inter-observer reproducibility was calculated using the weighted kappa coefficient. There were no statistically significant differences in sensitivity, specificity, PPV and NPV between the two CBCT systems. The effect of metal artifacts on VRF detection was not significantly different between the two CBCT systems.

  3. Background field removal technique using regularization enabled sophisticated harmonic artifact reduction for phase data with varying kernel sizes.

    Science.gov (United States)

    Kan, Hirohito; Kasai, Harumasa; Arai, Nobuyuki; Kunitomo, Hiroshi; Hirose, Yasujiro; Shibamoto, Yuta

    2016-09-01

    An effective background field removal technique is desired for more accurate quantitative susceptibility mapping (QSM) prior to dipole inversion. The aim of this study was to evaluate the accuracy of regularization enabled sophisticated harmonic artifact reduction for phase data with varying spherical kernel sizes (REV-SHARP) method using a three-dimensional head phantom and human brain data. The proposed REV-SHARP method used the spherical mean value operation and Tikhonov regularization in the deconvolution process, with varying 2-14mm kernel sizes. The kernel sizes were gradually reduced, similar to the SHARP with varying spherical kernel (VSHARP) method. We determined the relative errors and relationships between the true local field and estimated local field in REV-SHARP, VSHARP, projection onto dipole fields (PDF), and regularization enabled SHARP (RESHARP). Human experiment was also conducted using REV-SHARP, VSHARP, PDF, and RESHARP. The relative errors in the numerical phantom study were 0.386, 0.448, 0.838, and 0.452 for REV-SHARP, VSHARP, PDF, and RESHARP. REV-SHARP result exhibited the highest correlation between the true local field and estimated local field. The linear regression slopes were 1.005, 1.124, 0.988, and 0.536 for REV-SHARP, VSHARP, PDF, and RESHARP in regions of interest on the three-dimensional head phantom. In human experiments, no obvious errors due to artifacts were present in REV-SHARP. The proposed REV-SHARP is a new method combined with variable spherical kernel size and Tikhonov regularization. This technique might make it possible to be more accurate backgroud field removal and help to achive better accuracy of QSM. Copyright © 2016 Elsevier Inc. All rights reserved.

  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. Metal artefact reduction for accurate tumour delineation in radiotherapy

    DEFF Research Database (Denmark)

    Kovacs, David Gergely; Rechner, Laura A.; Appelt, Ane L.

    2018-01-01

    Background and purpose: Two techniques for metal artefact reduction for computed tomography were studied in order to identify their impact on tumour delineation in radiotherapy. Materials and methods: Using specially designed phantoms containing metal implants (dental, spine and hip) as well...... delineation significantly (pmetal implant....... as patient images, we investigated the impact of two methods for metal artefact reduction on (A) the size and severity of metal artefacts and the accuracy of Hounsfield Unit (HU) representation, (B) the visual impact of metal artefacts on image quality and (C) delineation accuracy. A metal artefact reduction...

  6. Reduction of respiratory ghosting motion artifacts in conventional two-dimensional multi-slice Cartesian turbo spin-echo: which k-space filling order is the best?

    Science.gov (United States)

    Inoue, Yuuji; Yoneyama, Masami; Nakamura, Masanobu; Takemura, Atsushi

    2018-06-01

    The two-dimensional Cartesian turbo spin-echo (TSE) sequence is widely used in routine clinical studies, but it is sensitive to respiratory motion. We investigated the k-space orders in Cartesian TSE that can effectively reduce motion artifacts. The purpose of this study was to demonstrate the relationship between k-space order and degree of motion artifacts using a moving phantom. We compared the degree of motion artifacts between linear and asymmetric k-space orders. The actual spacing of ghost artifacts in the asymmetric order was doubled compared with that in the linear order in the free-breathing situation. The asymmetric order clearly showed less sensitivity to incomplete breath-hold at the latter half of the imaging period. Because of the actual number of partitions of the k-space and the temporal filling order, the asymmetric k-space order of Cartesian TSE was superior to the linear k-space order for reduction of ghosting motion artifacts.

  7. Reduction of ring artifacts in CBCT: Detection and correction of pixel gain variations in flat panel detectors

    International Nuclear Information System (INIS)

    Altunbas, Cem; Lai, Chao-Jen; Zhong, Yuncheng; Shaw, Chris C.

    2014-01-01

    Purpose: In using flat panel detectors (FPD) for cone beam computed tomography (CBCT), pixel gain variations may lead to structured nonuniformities in projections and ring artifacts in CBCT images. Such gain variations can be caused by change in detector entrance exposure levels or beam hardening, and they are not accounted by conventional flat field correction methods. In this work, the authors presented a method to identify isolated pixel clusters that exhibit gain variations and proposed a pixel gain correction (PGC) method to suppress both beam hardening and exposure level dependent gain variations. Methods: To modulate both beam spectrum and entrance exposure, flood field FPD projections were acquired using beam filters with varying thicknesses. “Ideal” pixel values were estimated by performing polynomial fits in both raw and flat field corrected projections. Residuals were calculated by taking the difference between measured and ideal pixel values to identify clustered image and FPD artifacts in flat field corrected and raw images, respectively. To correct clustered image artifacts, the ratio of ideal to measured pixel values in filtered images were utilized as pixel-specific gain correction factors, referred as PGC method, and they were tabulated as a function of pixel value in a look-up table. Results: 0.035% of detector pixels lead to clustered image artifacts in flat field corrected projections, where 80% of these pixels were traced back and linked to artifacts in the FPD. The performance of PGC method was tested in variety of imaging conditions and phantoms. The PGC method reduced clustered image artifacts and fixed pattern noise in projections, and ring artifacts in CBCT images. Conclusions: Clustered projection image artifacts that lead to ring artifacts in CBCT can be better identified with our artifact detection approach. When compared to the conventional flat field correction method, the proposed PGC method enables characterization of nonlinear

  8. Melting metal waste for volume reduction and decontamination

    International Nuclear Information System (INIS)

    Copeland, G.L.; Heshmatpour, B.; Heestand, R.L.

    1980-01-01

    Melt-slagging was investigated as a technique for volume reduction and decontamination of radioactively contaminated scrap metals. Experiments were conducted using several metals and slags in which the partitioning of the contaminant U or Pu to the slag was measured. Concentrations of U or Pu in the metal product of about 1 ppM were achieved for many metals. A volume reduction of 30:1 was achieved for a typical batch of mixed metal scrap. Additionally, the production of granular products was demonstrated with metal shot and crushed slag

  9. Significant Artifact Reduction at 1.5T and 3T MRI by the Use of a Cochlear Implant with Removable Magnet: An Experimental Human Cadaver Study.

    Science.gov (United States)

    Wagner, Franca; Wimmer, Wilhelm; Leidolt, Lars; Vischer, Mattheus; Weder, Stefan; Wiest, Roland; Mantokoudis, Georgios; Caversaccio, Marco D

    2015-01-01

    Cochlear implants (CIs) are standard treatment for postlingually deafened individuals and prelingually deafened children. This human cadaver study evaluated diagnostic usefulness, image quality and artifacts in 1.5T and 3T magnetic resonance (MR) brain scans after CI with a removable magnet. Three criteria (diagnostic usefulness, image quality, artifacts) were assessed at 1.5T and 3T in five cadaver heads with CI. The brain magnetic resonance scans were performed with and without the magnet in situ. The criteria were analyzed by two blinded neuroradiologists, with focus on image distortion and limitation of the diagnostic value of the acquired MR images. MR images with the magnet in situ were all compromised by artifacts caused by the CI. After removal of the magnet, MR scans showed an unequivocal artifact reduction with significant improvement of the image quality and diagnostic usefulness, both at 1.5T and 3T. Visibility of the brain stem, cerebellopontine angle, and parieto-occipital lobe ipsilateral to the CI increased significantly after magnet removal. The results indicate the possible advantages for 1.5T and 3T MR scanning of the brain in CI carriers with removable magnets. Our findings support use of CIs with removable magnets, especially in patients with chronic intracranial pathologies.

  10. Reduction of U3O8 to U by a metallic reductant, Li

    International Nuclear Information System (INIS)

    Jin-Mok Hur; Sun-Seok Hong; Hansoo Lee

    2010-01-01

    Reduction of U 3 O 8 was investigated for the recycling of spent oxide fuel from a commercial nuclear power plant. The possible reduction methods were proposed and compared. Based on the thermodynamic analysis, Li metal was selected as a reductant. The optimum reaction temperature for the reduction of U 3 O 8 was investigated at the wider reaction temperature range. The adverse oxidation of U metal by Li 2 O at 1,000 deg C was experimentally verified. Ellingham diagram was constructed to investigate the extent of the uranium oxides reduction when the reaction was carried out above melting point of U metal. (author)

  11. Inspection about the corrosion of metallic archaeological artifacts in ground. 3

    International Nuclear Information System (INIS)

    Honda, Takashi; Yamaguchi, Shingo

    2003-01-01

    The corrosion behaviors of iron-based archaeological remains, which were dug out in six relics in Aomori-ken and Izumotaisya-keidai-iseki, were analyzed mainly with using X-ray CT. Several samples were cut and investigated on the details of metals and oxide films. The soils were also analyzed on redox-potential, resistance, chemical contents, and others. The results indicate that metal remains in 7/14 samples. The corrosion amounts of objects of Aomori-ken were estimated to be from 1 to 4 mm during 400-1000 years. The environments were supposed to be oxidizing. On the other hands, it is supposed that two objects in Izumotaisya-keidai-iseki were in a reducing condition. The corrosion amounts were 0.5-2 mm. Furthermore, the corrosion behavior of the cast gas-pipe, which had been buried for about 130 years, were evaluated. By analyzing analysis data of soil, the environment is estimated to be weak oxidizing, and the maximum graphitic corrosion depth was about 7 mm. (author)

  12. Characterizing the reduction of stimulation artifact noise in a tripolar nerve cuff electrode by application of a conductive shield layer.

    Science.gov (United States)

    Sabetian, Parisa; Sadeghlo, Bita; Zhang, Chengran Harvey; Yoo, Paul B

    2017-02-01

    Tripolar nerve cuff electrodes have been widely used for measuring peripheral nerve activity. However, despite the high signal-to-noise ratio levels that can be achieved with this recording configuration, the clinical use of cuff electrodes in closed-loop controlled neuroprostheses remains limited. This is largely attributed to artifact noise signals that contaminate the recorded neural activity. In this study, we investigated the use of a conductive shield layer (CSL) as a means of reducing the artifact noise recorded by nerve cuff electrodes. Using both computational simulations and in vivo experiments, we found that the CSL can result in up to an 85% decrease in the recorded artifact signal. Both the electrical conductivity and the surface area of the CSL were identified as important design criteria. Although this study shows that the CSL can significantly reduce artifact noise in tripolar nerve cuff electrodes, long-term implant studies are needed to validate our findings. Copyright © 2016 IPEM. Published by Elsevier Ltd. All rights reserved.

  13. EEG artifacts reduction by multivariate empirical mode decomposition and multiscale entropy for monitoring depth of anaesthesia during surgery.

    Science.gov (United States)

    Liu, Quan; Chen, Yi-Feng; Fan, Shou-Zen; Abbod, Maysam F; Shieh, Jiann-Shing

    2017-08-01

    Electroencephalography (EEG) has been widely utilized to measure the depth of anaesthesia (DOA) during operation. However, the EEG signals are usually contaminated by artifacts which have a consequence on the measured DOA accuracy. In this study, an effective and useful filtering algorithm based on multivariate empirical mode decomposition and multiscale entropy (MSE) is proposed to measure DOA. Mean entropy of MSE is used as an index to find artifacts-free intrinsic mode functions. The effect of different levels of artifacts on the performances of the proposed filtering is analysed using simulated data. Furthermore, 21 patients' EEG signals are collected and analysed using sample entropy to calculate the complexity for monitoring DOA. The correlation coefficients of entropy and bispectral index (BIS) results show 0.14 ± 0.30 and 0.63 ± 0.09 before and after filtering, respectively. Artificial neural network (ANN) model is used for range mapping in order to correlate the measurements with BIS. The ANN method results show strong correlation coefficient (0.75 ± 0.08). The results in this paper verify that entropy values and BIS have a strong correlation for the purpose of DOA monitoring and the proposed filtering method can effectively filter artifacts from EEG signals. The proposed method performs better than the commonly used wavelet denoising method. This study provides a fully adaptive and automated filter for EEG to measure DOA more accuracy and thus reduce risk related to maintenance of anaesthetic agents.

  14. A real-time artifact reduction algorithm based on precise threshold during short-separation optical probe insertion in neurosurgery

    Directory of Open Access Journals (Sweden)

    Weitao Li

    2017-01-01

    Full Text Available During neurosurgery, an optical probe has been used to guide the micro-electrode, which is punctured into the globus pallidus (GP to create a lesion that can relieve the cardinal symptoms. Accurate target localization is the key factor to affect the treatment. However, considering the scattering nature of the tissue, the “look ahead distance (LAD” of optical probe makes the boundary between the different tissues blurred and difficult to be distinguished, which is defined as artifact. Thus, it is highly desirable to reduce the artifact caused by LAD. In this paper, a real-time algorithm based on precise threshold was proposed to eliminate the artifact. The value of the threshold was determined by the maximum error of the measurement system during the calibration procession automatically. Then, the measured data was processed sequentially only based on the threshold and the former data. Moreover, 100μm double-fiber probe and two-layer and multi-layer phantom models were utilized to validate the precision of the algorithm. The error of the algorithm is one puncture step, which was proved in the theory and experiment. It was concluded that the present method could reduce the artifact caused by LAD and make the real boundary sharper and less blurred in real-time. It might be potentially used for the neurosurgery navigation.

  15. Reduction of metal artefacts in musculoskeletal imaging

    International Nuclear Information System (INIS)

    Sutter, Reto; Dietrich, Tobias

    2016-01-01

    Joint replacement and other orthopaedic implants are utilized in many patients with musculoskeletal disorders. While these operations commonly show a good clinical result, a substantial number of patients need to undergo postoperative imaging during follow-up. The presence of orthopaedic implants induces severe metal artefacts at MRI and CT. We review several basic methods and advanced techniques for reducing metal artefacts at MRI and CT in order to enable a diagnostic examination in patients with metal implants. With the use of these techniques, MRI and CT are important and reliable modalities to examine patients with joint replacement and orthopaedic implants.

  16. 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.

  17. Metallization of uranium oxide powders by lithium reduction

    International Nuclear Information System (INIS)

    Kim, I. S.; Seo, J. S.; Oh, S. C.; Hong, S. S.; Lee, W. K.

    2002-01-01

    Laboratory scale experiments on the reduction of uranium oxide powders into metal by lithium were performed in order to determine the equipment setup and optimum operation conditions. The method of filtration using the porous magnesia filter was introduced to recover uranium metal powders produced. Based on the laboratory scale experimental results, mock-up scale (20 kg U/batch) metallizer was designed and made. The applicability to the metallization process was estimated with respect to the thermal stability of the porous magnesia filter in the high temperature molten salt, the filtration of the fine uranium metal powders, and the operability of the equipment

  18. Carbothermic reduction of uranium oxides into solvent metallic baths

    International Nuclear Information System (INIS)

    Guisard Restivo, Thomaz A.; Capocchi, Jose D.T.

    2004-01-01

    The carbothermic reduction of UO 2 and U 3 O 8 is studied employing tin and silicon solvent metallic baths in thermal analysis equipment, under Ar inert and N 2 reactive atmospheres. The metallic solvents are expected to lower the U activity by several orders of magnitude owing to strong interactions among the metals. The reduction products are composed of the solvent metal matrix and intermetallic U compounds. Silicon is more effective in driving the reduction since there is no residual UO 2 after the reaction. The gaseous product detected by mass spectrometer (MS) during the reduction is CO. A kinetic study for the Si case was accomplished by the stepwise isothermal analysis (SAI) method, leading to the identification of the controlling mechanisms as chemical reaction at the surface and nucleation, for UO 2 and U 3 O 8 charges, respectively. One example for another system containing Al 2 O 3 is also shown

  19. Metallic artifacts from internal scaphoid fracture fixation screws: comparison between C-arm flat-panel, cone-beam, and multidetector computed tomography.

    Science.gov (United States)

    Finkenstaedt, Tim; Morsbach, Fabian; Calcagni, Maurizio; Vich, Magdalena; Pfirrmann, Christian W A; Alkadhi, Hatem; Runge, Val M; Andreisek, Gustav; Guggenberger, Roman

    2014-08-01

    The aim of this study was to compare image quality and extent of artifacts from scaphoid fracture fixation screws using different computed tomography (CT) modalities and radiation dose protocols. Imaging of 6 cadaveric wrists with artificial scaphoid fractures and different fixation screws was performed in 2 screw positions (45° and 90° orientation in relation to the x/y-axis) using multidetector CT (MDCT) and 2 flat-panel CT modalities, C-arm flat-panel CT (FPCT) and cone-beam CT (CBCT), the latter 2 with low and standard radiation dose protocols. Mean cartilage attenuation and metal artifact-induced absolute Hounsfield unit changes (= artifact extent) were measured. Two independent radiologists evaluated different image quality criteria using a 5-point Likert-scale. Interreader agreements (Cohen κ) were calculated. Mean absolute Hounsfield unit changes and quality ratings were compared using Friedman and Wilcoxon signed-rank tests. Artifact extent was significantly smaller for MDCT and standard-dose FPCT compared with CBCT low- and standard-dose acquisitions (all P 0.05). Both MDCT and FPCT standard-dose protocols showed equal ratings for screw bone interface, fracture line, and trabecular bone evaluation (P = 0.06, 0.2, and 0.2, respectively) and performed significantly better than FPCT low- and CBCT low- and standard-dose acquisitions (all P < 0.05). Good interreader agreement was found for image quality comparisons (Cohen κ = 0.76-0.78). Both MDCT and FPCT standard-dose acquisition showed comparatively less metal-induced artifacts and better overall image quality compared with FPCT low-dose and both CBCT acquisitions. Flat-panel CT may provide sufficient image quality to serve as a versatile CT alternative for postoperative imaging of internally fixated wrist fractures.

  20. SU-C-207-04: Reconstruction Artifact Reduction in X-Ray Cone Beam CT Using a Treatment Couch Model

    Energy Technology Data Exchange (ETDEWEB)

    Lasio, G; Hu, E; Zhou, J; Lee, M; Yi, B [University of Maryland School of Medicine, Baltimore, MD (United States)

    2015-06-15

    Purpose: to mitigate artifacts induced by the presence of the RT treatment couch in on-board CBCT and improve image quality Methods: a model of a Varian IGRT couch is constructed using a CBCT scan of the couch in air. The model is used to generate a set of forward projections (FP) of the treatment couch at specified gantry angles. The model couch forward projections are then used to process CBCT scan projections which contain the couch in addition to the scan object (Catphan phantom), in order to remove the attenuation component of the couch at any given gantry angle. Prior to pre-processing with the model FP, the Catphan projection data is normalized to an air scan with bowtie filter. The filtered Catphan projections are used to reconstruct the CBCT with an in-house FDK algorithm. The artifact reduction in the processed CBCT scan is assessed visually, and the image quality improvement is measured with the CNR over a few selected ROIs of the Catphan modules. Results: Sufficient match between the forward projected data and the x-ray projections is achieved to allow filtering in attenuation space. Visual improvement of the couch induced artifacts is achieved, with a moderate expense of CNR. Conclusion: Couch model-based correction of CBCT projection data has a potential for qualitative improvement of clinical CBCT scans, without requiring position specific correction data. The technique could be used to produce models of other artifact inducing devices, such as immobilization boards, and reduce their impact on patient CBCT images.

  1. Recovery of noble metals from HLLW using photocatalytic reduction

    International Nuclear Information System (INIS)

    Nishi, T.; Uetake, N.; Kawamura, F.; Yusa, H.

    1987-01-01

    In high-level liquid waste (HLLW) from fuel reprocessing plants, noble metals (palladium, rhodium, and ruthenium), which account for ∼ 10 wt% of fission products, exist as ions. These metals are very useful as catalytic material in automobile exhaust systems and other chemical processes, but they are rare in nature, making their recovery from fission products highly desirable. The ions of noble metals in solution have the feature that their reduction potential from ion to metal is relatively high compared with that of other fission product ions, so they can be selectively separated as a metal by a reduction process. The authors think a photoreduction process using a photocatalysts, which functions as photon-electron conversion agent, is suitable for the recovery of noble metals from HLLW for three reasons: (1) this process uses no reduction agents, which usually degrade the nitric acid, so that coprecipitation of other fission products does not occur. (2) The reactions are induced by light, which does not contaminate the reaction system, and in contrast with ordinary photo-redox reactions, the quantum yield is quite high. (3) As the photocatalyst does not change in the reaction, it can be used again and again. The report shows the results of fundamental experiments on the application of photocatalytic reduction to the recovery of noble metal ions in nitric acid solution

  2. SU-E-J-84: Quantitative Dosimetry Assessment of the Impact of Image Artifacts of Metal Implants in Spinal SABR Treatment

    Energy Technology Data Exchange (ETDEWEB)

    Chen, T; Zhang, M; Hanft, S; Green, R; Yue, N; Goyal, S [Rutgers University, New Brunswick, NJ (United States)

    2015-06-15

    Purpose: Metal rods are frequently used to stabilize the spine in patients with metastatic disease. The high Z material causes imaging artifacts in the surrounding tissue in CT scans, which introduces dosimetric uncertainty when inhomogeneity correction is enabled for radiation treatment planning. The purpose of this study is to quantify the dosimetric deviations caused by the imaging artifacts and to evaluate the effectiveness of using Hounsfield units (HU) overwriting to reduce dosimetric uncertainties. Methods: We retrospectively reviewed treatment plans for 4 patients with metal implants who received stereotactic ablative radiation therapy (SABR) for metastatic disease to the spine on Tomotherapy HiArt. For all four patients, the region of imaging artifact surrounding the metal implants was contoured and the pixel HU’s were overwritten to be water equivalent. We then generated adaptive treatment plans for these patients using the MVCT pretreatment set up images and batched beamlets in the original treatment plans. The dosimetry deviation between the adaptive and original plans were compared and quantitatively analyzed. Results: For three out of four patient, the major OAR (spinal cord) dose (0.35cc or 10% according to protocols and fractionation) increased (2.7%, 5.5%, 0%, 3.9%, mean=3.0±2.3%, p=0.04), and the PTV dose (D90 or D95 as per prescription) increased for all four patients ( 2%, 5%, 0.7%, 3.6%, mean=2.8±1.9%, p=0.03) in the adaptive plan with HU overwriting. The average point dose deviation of the Tomotherapy DQA for the same patients was −1.0±1.0%. For plans without HU overwriting, the dose deviation from the treatment plan will increase. Conclusion: The metal implant and the imaging artifacts may cause a significant dosimetric impact on radiation treatment plans for spinal disease. The dose to the PTV and the spinal cord was under-calculated in treatment plans without considering the imaging artifacts. HU overwriting can reduce the dosimetry

  3. Trial of artifact reduction in body diffusion weighted imaging development and basic examination of 'TRacking Only Navigator' (TRON method)

    International Nuclear Information System (INIS)

    Horie, Tomohiko; Takahara, Tarou; Ogino, Tetsuo

    2008-01-01

    In recent years, the utility of body diffusion weighted imaging as represented by diffusion weighted whole body imaging with background body signal suppression (DWIBS), the DWIBS method, is very high. However, there was a problem in the DWIBS method involving the artifact corresponding to the distance of the diaphragm. To provide a solution, the respiratory trigger (RT) method and the navigator echo method were used together. A problem was that scan time extended to the compensation and did not predict the extension rate, although both artifacts were reduced. If we used only navigator real time slice tracking (NRST) from the findings obtained by the DWIBS method, we presumed the artifacts would be ameliorable without the extension of scan time. Thus, the TRacking Only Navigator (TRON) method was developed, and a basic examination was carried out for the liver. An important feature of the TRON method is the lack of the navigator gating window (NGW) and addition of the method of linear interpolation prior to NRST. The method required the passing speed and the distance from the volunteer's diaphragm. The estimated error from the 2D-selective RF pulse (2DSRP) of the TRON method to slice excitation was calculated. The condition of 2D SRP, which did not influence the accuracy of NRST, was required by the movement phantom. The volunteer was scanned, and the evaluation and actual scan time of the image quality were compared with the RT and DWIBS methods. Diaphragm displacement speed and the quantity of displacement were determined in the head and foot directions, and the result was 9 mm/sec, and 15 mm. The estimated error was within 2.5 mm in b-factor 1000 sec/mm 2 . The FA of 2DSRP was 15 degrees, and the navigator echo length was 120 mm, which was excellent. In the TRON method, the accuracy of NRST was steady because of line interpolation. The TRON method obtained image quality equal to that of the RT method with the b-factor in the volunteer scanning at short actual

  4. [Trial of artifact reduction in body diffusion weighted imaging development and basic examination of "TRacking Only Navigator"(TRON method)].

    Science.gov (United States)

    Horie, Tomohiko; Takahara, Tarou; Ogino, Tetsuo; Okuaki, Tomoyuki; Honda, Masatoshi; Okumura, Yasuhiro; Kajihara, Nao; Usui, Keisuke; Muro, Isao; Imai, Yutaka

    2008-09-20

    In recent years, the utility of body diffusion weighted imaging as represented by diffusion weighted whole body imaging with background body signal suppression (DWIBS), the DWIBS method, is very high. However, there was a problem in the DWIBS method involving the artifact corresponding to the distance of the diaphragm. To provide a solution, the respiratory trigger (RT) method and the navigator echo method were used together. A problem was that scan time extended to the compensation and did not predict the extension rate, although both artifacts were reduced. If we used only navigator real time slice tracking (NRST) from the findings obtained by the DWIBS method, we presumed the artifacts would be ameliorable without the extension of scan time. Thus, the TRacking Only Navigator (TRON) method was developed, and a basic examination was carried out for the liver. An important feature of the TRON method is the lack of the navigator gating window (NGW) and addition of the method of linear interpolation prior to NRST. The method required the passing speed and the distance from the volunteer's diaphragm. The estimated error from the 2D-selective RF pulse (2DSRP) of the TRON method to slice excitation was calculated. The condition of 2D SRP, which did not influence the accuracy of NRST, was required by the movement phantom. The volunteer was scanned, and the evaluation and actual scan time of the image quality were compared with the RT and DWIBS methods. Diaphragm displacement speed and the quantity of displacement were determined in the head and foot directions, and the result was 9 mm/sec, and 15 mm. The estimated error was within 2.5 mm in b-factor 1000 sec/mm(2). The FA of 2DSRP was 15 degrees, and the navigator echo length was 120 mm, which was excellent. In the TRON method, the accuracy of NRST was steady because of line interpolation. The TRON method obtained image quality equal to that of the RT method with the b-factor in the volunteer scanning at short actual

  5. Effect of subcutaneous butylscopolamine administration in the reduction of peristaltic artifacts in 1.5-T MR fast abdominal examinations

    International Nuclear Information System (INIS)

    Dosda, Rosa; Marti-Bonmati, Luis; Molla, Enrique; Arana, Estanislao; Ronchera-Oms, Crisanto L.

    2003-01-01

    In abdominal MR imaging, ghost artifacts from noncyclic bowel movements can reduce the quality of the images. Although pharmacologic suppression of motion is effective, no study has being conducted to analyze the influence of drug motion suppression on fast breath-hold 1.5-T examinations of the upper abdomen. A prospective, randomized, double-blind trial was conducted in 50 patients. Patients were randomly distributed into two groups: The control group received only an oral solution, whereas the other group received the oral solution plus a subcutaneous injection of 20 mg of butylscopolamine 10 min before the MR examination. Breath-hold T1-weighted gradient-recalled-echo (GRE) MR images were obtained in a 1.5-T superconductive unit. Quantitative image analysis was performed with region-of-interest (ROI) measurements of the signal intensity of the liver and in background air anterior and lateral to the patient. A qualitative analysis of the subjective quality of the T1-weighted images was also done, and the adverse reactions were registered. The groups were homogeneous regarding age, gender, and weight distribution. No significant differences in the signal intensity of the liver and in the incoherent noise measurements were found between the two groups. Gastrointestinal noise showed significant differences between groups, with lower values for the butylscopolamine group compared with the control group. There was also a statistically significant difference in the image quality between groups, and optimal studies were only found in the butylscopolamine group, where most patients had a good-quality evaluation. Regarding adverse events, there were non-significant differences between groups. In conclusion, administration of an antiperistaltic agent to reduce the movements of the gastrointestinal tract diminishes the motion artifacts generated on MR imaging of the abdomen, even at high field strength and with fast imaging sequences. Images of the upper abdomen obtained

  6. Chalcogenide metal centers for oxygen reduction reaction: Activity and tolerance

    International Nuclear Information System (INIS)

    Feng Yongjun; Gago, Aldo; Timperman, Laure; Alonso-Vante, Nicolas

    2011-01-01

    This mini-review summarizes materials design methods, oxygen reduction kinetics, tolerance to small organic molecules and fuel cell performance of chalcogenide metal catalysts, particularly, ruthenium (Ru x Se y ) and non-precious transition metals (M x X y : M = Co, Fe and Ni; X = Se and S). These non-platinum catalysts are potential alternatives to Pt-based catalysts because of their comparable catalytic activity (Ru x Se y ), low cost, high abundance and, in particular, a high tolerance to small organic molecules. Developing trends of synthesis methods, mechanism of oxygen reduction reaction and applications in direct alcohol fuel cells as well as the substrate effect are highlighted.

  7. Induction melting for volume reduction of metallic TRU wastes

    International Nuclear Information System (INIS)

    Westsik, J.H. Jr.; Montgomery, D.R.; Katayama, Y.B.; Ross, W.A.

    1986-01-01

    Volume reduction of metallic transuranic wastes offers economic and safety incentives for treatment of wastes generated at a hypothetical commercial fuel reprocessing facility. Induction melting has been identified as the preferred process for volume reduction of spent fuel hulls, fuel assembly hardware, and failed equipment from a reprocessing plant. Bench-scale melting of Zircaloy and stainless steel mixtures has been successfully conducted in a graphite crucible inside a large vacuum chamber. A low-melting-temperature alloy forms that has demonstrated excellent leach resistance. The alloy can be used to encapsulate other metallic wastes that cannot be melted using the existing equipment design

  8. Induction melting for volume reduction of metallic TRU wastes

    International Nuclear Information System (INIS)

    Westsik, J.H. Jr.; Montgomery, D.R.; Katayama, Y.B.; Ross, W.A.

    1986-02-01

    Volume reduction of metallic transuranic wastes offers economic and safety incentives for treatment of wastes generated at a hypothetical commercial fuel reprocessing facility. Induction melting has been identified as the preferred process for volume reduction of spent fuel hulls, fuel assembly hardware, and failed equipment from a reprocessing plant. Bench-scale melting of Zircaloy and stainless steel mixtures has been successfully conducted in a graphite crucible inside a large vacuum chamber. A low-melting-temperature alloy forms that has demonstrated excellent leach resistance. The alloy can be used to encapsulate other metallic wastes that cannot be melted using the existing equipment design. 18 refs., 4 figs., 3 tabs

  9. Direct chemical reduction of neptunium oxide to neptunium metal using calcium and calcium chloride

    International Nuclear Information System (INIS)

    Squires, Leah N.; Lessing, Paul

    2016-01-01

    A process of direct reduction of neptunium oxide to neptunium metal using calcium metal as the reducing agent is discussed. After reduction of the oxide to metal, the metal is separated by density from the other components of the reaction mixture and can be easily removed upon cooling. The direct reduction technique consistently produces high purity (98%–99% pure) neptunium metal.

  10. Photoacoustic reflection artifact reduction using photoacoustic-guided focused ultrasound : comparison between plane-wave and element-by-element synthetic backpropagation approach

    NARCIS (Netherlands)

    Kuniyil Ajith Singh, M.; Jaeger, M.; Frenz, M.; Steenbergen, Wiendelt

    2017-01-01

    Reflection artifacts caused by acoustic inhomogeneities constitute a major problem in epi-mode biomedical photoacoustic imaging. Photoacoustic transients from the skin and superficial optical absorbers traverse into the tissue and reflect off echogenic structures to generate reflection artifacts.

  11. Chromate reduction and heavy metal fixation in soil

    International Nuclear Information System (INIS)

    Schwitzgebel, K.

    1992-06-01

    In situ reduction of chromates and the fixation of the metals Cr, Pb, Zn, Cu, Cd and Ni in soil was investigated using Fe II and soluble silica. Fe II fulfills two functions. It reduces chromates (CrVI) at soil pH to CrIII and the reaction products, Fe(OH) 3 and Cr(OH) 3 , coprecipitate/adsorb heavy metals. In the absence of CrVI iron is added as FeIII. Destabilized silica also fulfills two functions. It reacts with the metal and metal hydroxides and reduces the soil permeability. The leaching rate (mg/m 2 s) of a metal is the product of leachate flow rate (ell/M 2 s) and the leachate concentration (mg/ell). The leachate flow rate is directly proportional to the hydraulic coefficient (Darcy's Law). Treatment with destabilized silica reduces the hydraulic coefficient of virgin soil (K h = 10 -2 ...10 -4 ) to K h =10 -7 (cm/s) resulting in a flow rate reduction of 3--5 orders of magnitude. Iron plus silica treatment results in a leachate concentration reduction of up to 2 orders of magnitude (Cr:95--99%;Pb:99%;Zn 95--99%; Cd:93--99%; Ni:75--94%). Combined effect of flow rate reduction and leachate concentration reduction results in a potential leaching rate reduction of five to seven orders of magnitude. Iron-silica treatment may be developed into an efficient containment technology, provided the silica gel integrity does not change with time

  12. Prospective navigator-echo-based real-time triggering of fetal head movement for the reduction of artifacts.

    Science.gov (United States)

    Bonel, H; Frei, K A; Raio, L; Meyer-Wittkopf, M; Remonda, L; Wiest, R

    2008-04-01

    The purpose of this study was to evaluate the neuroimaging quality and accuracy of prospective real-time navigator-echo acquisition correction versus untriggered intrauterine magnetic resonance imaging (MRI) techniques. Twenty women in whom fetal motion artifacts compromised the neuroimaging quality of fetal MRI taken during the 28.7 +/- 4 week of pregnancy below diagnostic levels were additionally investigated using a navigator-triggered half-Fourier acquired single-shot turbo-spin echo (HASTE) sequence. Imaging quality was evaluated by two blinded readers applying a rating scale from 1 (not diagnostic) to 5 (excellent). Diagnostic criteria included depiction of the germinal matrix, grey and white matter, CSF, brain stem and cerebellum. Signal-difference-to-noise ratios (SDNRs) in the white matter and germinal zone were quantitatively evaluated. Imaging quality improved in 18/20 patients using the navigator echo technique (2.4 +/- 0.58 vs. 3.65 +/- 0.73 SD, p < 0.01 for all evaluation criteria). In 2/20 patients fetal movement severely impaired image quality in conventional and navigated HASTE. Navigator-echo imaging revealed additional structural brain abnormalities and confirmed diagnosis in 8/20 patients. The accuracy improved from 50% to 90%. Average SDNR increased from 0.7 +/- 7.27 to 19.83 +/- 15.71 (p < 0.01). Navigator-echo-based real-time triggering of fetal head movement is a reliable technique that can deliver diagnostic fetal MR image quality despite vigorous fetal movement.

  13. MOTION ARTIFACT REDUCTION IN FUNCTIONAL NEAR INFRARED SPECTROSCOPY SIGNALS BY AUTOREGRESSIVE MOVING AVERAGE MODELING BASED KALMAN FILTERING

    Directory of Open Access Journals (Sweden)

    MEHDI AMIAN

    2013-10-01

    Full Text Available Functional near infrared spectroscopy (fNIRS is a technique that is used for noninvasive measurement of the oxyhemoglobin (HbO2 and deoxyhemoglobin (HHb concentrations in the brain tissue. Since the ratio of the concentration of these two agents is correlated with the neuronal activity, fNIRS can be used for the monitoring and quantifying the cortical activity. The portability of fNIRS makes it a good candidate for studies involving subject's movement. The fNIRS measurements, however, are sensitive to artifacts generated by subject's head motion. This makes fNIRS signals less effective in such applications. In this paper, the autoregressive moving average (ARMA modeling of the fNIRS signal is proposed for state-space representation of the signal which is then fed to the Kalman filter for estimating the motionless signal from motion corrupted signal. Results are compared to the autoregressive model (AR based approach, which has been done previously, and show that the ARMA models outperform AR models. We attribute it to the richer structure, containing more terms indeed, of ARMA than AR. We show that the signal to noise ratio (SNR is about 2 dB higher for ARMA based method.

  14. Electrochemical reduction of metal ions in dilute solution using hydrogen

    NARCIS (Netherlands)

    Portegies Zwart, I.; Wijnbelt, E.C.W.; Janssen, L.J.J.

    1995-01-01

    Reduction of metal ions in dilute solutions is of great interest for purification of waste waters and process liquids. A new electrochemical cell has been introduced. This cell - a GBC-cell - is a combination of a gasdiffusion electrode in direct contact with a packed bed of carbon particles.

  15. MR imaging with metal artifact-reducing sequences and gadolinium contrast agent in a case-control study of periprosthetic abnormalities in patients with metal-on-metal hip prostheses

    Energy Technology Data Exchange (ETDEWEB)

    Mueller, Gunilla M.; Mueller, Markus F.; Ekberg, Olle [Lund University, Skaane University Hospital, Department of Radiology, Malmoe (Sweden); Maansson, Sven [Lund University, Skaane University Hospital, Department of Medical Radiation Physics, Malmoe (Sweden); Schewelov, Thord von [Lund University, Skaane University Hospital, Department of Orthopedic Surgery, Malmoe (Sweden); Nittka, Mathias [Siemens AG, Healthcare Sector, Erlangen (Germany); Lundin, Bjoern [Lund University, Skaane University Hospital, Department of Radiology, Lund (Sweden)

    2014-08-15

    To apply and compare magnetic resonance imaging (MRI) metal artifact reducing sequences (MARS) including subtraction imaging after contrast application in patients with metal-on-metal (MoM) hip prostheses, investigate the prevalence and characteristics of periprosthetic abnormalities, as well as their relation with pain and risk factors. Fifty-two MoM prostheses (35 cases with pain and or risk factors, and 17 controls) in 47 patients were examined in a 1.5-T MR scanner using MARS: turbo spin echo (TSE) with high readout bandwidth with and without view angle tilting (VAT), TSE with VAT and slice encoding for metal artifact correction (SEMAC), short tau inversion recovery (STIR) with matched RF pulses, and post-contrast imaging. The relations of MRI findings to pain and risk factors were analyzed and in five revised hips findings from operation, histology, and MRI were compared. TSE VAT detected the highest number of osteolyses. Soft tissue mass, effusion, and capsular thickening were common, whereas osteolysis in acetabulum and femur were less frequent. Contrast enhancement occurred in bone, synovia, joint capsule, and the periphery of soft tissue mass. There was no significant relation between MRI findings and pain or risk factors. MARS and gadolinium subtraction imaging are useful for evaluation of complications to MoM prosthesis. TSE VAT had the highest sensitivity for osteolysis. Contrast enhancement might indicate activation of aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL). Pain, small head, or steep prosthesis inclination angle are not useful predictors of periprosthetic abnormalities, and wide indications for MR follow-up are warranted. (orig.)

  16. AR2, a novel automatic muscle artifact reduction software method for ictal EEG interpretation: Validation and comparison of performance with commercially available software [version 2; referees: 2 approved

    Directory of Open Access Journals (Sweden)

    Shennan Aibel Weiss

    2017-04-01

    Full Text Available Objective: To develop a novel software method (AR2 for reducing muscle contamination of ictal scalp electroencephalogram (EEG, and validate this method on the basis of its performance in comparison to a commercially available software method (AR1 to accurately depict seizure-onset location. Methods: A blinded investigation used 23 EEG recordings of seizures from 8 patients. Each recording was uninterpretable with digital filtering because of muscle artifact and processed using AR1 and AR2 and reviewed by 26 EEG specialists. EEG readers assessed seizure-onset time, lateralization, and region, and specified confidence for each determination. The two methods were validated on the basis of the number of readers able to render assignments, confidence, the intra-class correlation (ICC, and agreement with other clinical findings. Results: Among the 23 seizures, two-thirds of the readers were able to delineate seizure-onset time in 10 of 23 using AR1, and 15 of 23 using AR2 (p<0.01. Fewer readers could lateralize seizure-onset (p<0.05. The confidence measures of the assignments were low (probable-unlikely, but increased using AR2 (p<0.05. The ICC for identifying the time of seizure-onset was 0.15 (95% confidence interval (CI, 0.11-0.18 using AR1 and 0.26 (95% CI 0.21-0.30 using AR2.  The EEG interpretations were often consistent with behavioral, neurophysiological, and neuro-radiological findings, with left sided assignments correct in 95.9% (CI 85.7-98.9%, n=4 of cases using AR2, and 91.9% (77.0-97.5% (n=4 of cases using AR1. Conclusions: EEG artifact reduction methods for localizing seizure-onset does not result in high rates of interpretability, reader confidence, and inter-reader agreement. However, the assignments by groups of readers are often congruent with other clinical data. Utilization of the AR2 software method may improve the validity of ictal EEG artifact reduction.

  17. Universality in Oxygen Reduction Electrocatalysis on Metal Surfaces

    DEFF Research Database (Denmark)

    Viswanathan, Venkatasubramanian; Hansen, Heine Anton; Rossmeisl, Jan

    2012-01-01

    In this work, we extend the activity volcano for oxygen reduction from the face-centered cubic (fcc) metal (111) facet to the (100) facet. Using density functional theory calculations, we show that the recent findings of constant scaling between OOH* and OH* holds on the fcc metal (100) facet......, as well. Using this fact, we show the existence of a universal activity volcano to describe oxygen reduction electrocatalysis with a minimum overpotential, ηmin = 0.37 ± 0.1 V. Specifically, we find that the (100) facet of Pt is found to bind oxygen intermediates too strongly and is not active for oxygen...... reduction reaction (ORR). In contrast, Au(100) is predicted to be more active than Au(111) and comparable in activity to Pt alloys. Using this activity volcano, we further predict that Au alloys that bind OH more strongly could display improved ORR activity on the (100) facet. We carry out a computational...

  18. Prospective navigator-echo-based real-time triggering of fetal head movement for the reduction of artifacts

    International Nuclear Information System (INIS)

    Bonel, H.; Frei, K.A.; Raio, L.; Meyer-Wittkopf, M.; Remonda, L.; Wiest, R.

    2008-01-01

    The purpose of this study was to evaluate the neuroimaging quality and accuracy of prospective real-time navigator-echo acquisition correction versus untriggered intrauterine magnetic resonance imaging (MRI) techniques. Twenty women in whom fetal motion artifacts compromised the neuroimaging quality of fetal MRI taken during the 28.7 ± 4 week of pregnancy below diagnostic levels were additionally investigated using a navigator-triggered half-Fourier acquired single-shot turbo-spin echo (HASTE) sequence. Imaging quality was evaluated by two blinded readers applying a rating scale from 1 (not diagnostic) to 5 (excellent). Diagnostic criteria included depiction of the germinal matrix, grey and white matter, CSF, brain stem and cerebellum. Signal-difference-to-noise ratios (SDNRs) in the white matter and germinal zone were quantitatively evaluated. Imaging quality improved in 18/20 patients using the navigator echo technique (2.4 ± 0.58 vs. 3.65 ± 0.73 SD, p < 0.01 for all evaluation criteria). In 2/20 patients fetal movement severely impaired image quality in conventional and navigated HASTE. Navigator-echo imaging revealed additional structural brain abnormalities and confirmed diagnosis in 8/20 patients. The accuracy improved from 50% to 90%. Average SDNR increased from 0.7 ± 7.27 to 19.83 ± 15.71 (p < 0.01). Navigator-echo-based real-time triggering of fetal head movement is a reliable technique that can deliver diagnostic fetal MR image quality despite vigorous fetal movement. (orig.)

  19. Prospective navigator-echo-based real-time triggering of fetal head movement for the reduction of artifacts

    Energy Technology Data Exchange (ETDEWEB)

    Bonel, H. [University Hospital Berne-Inselspital, Freiburgstrasse, Institute of Diagnostic, Interventional and Pediatric Radiology, Bern (Switzerland); Frei, K.A.; Raio, L.; Meyer-Wittkopf, M. [University of Berne, Women' s' Hospital, Bern (Switzerland); Remonda, L.; Wiest, R. [University of Berne, Institute of Diagnostic and Interventional Neuroradiology (DIN), Inselspital, Bern (Switzerland)

    2008-04-15

    The purpose of this study was to evaluate the neuroimaging quality and accuracy of prospective real-time navigator-echo acquisition correction versus untriggered intrauterine magnetic resonance imaging (MRI) techniques. Twenty women in whom fetal motion artifacts compromised the neuroimaging quality of fetal MRI taken during the 28.7 {+-} 4 week of pregnancy below diagnostic levels were additionally investigated using a navigator-triggered half-Fourier acquired single-shot turbo-spin echo (HASTE) sequence. Imaging quality was evaluated by two blinded readers applying a rating scale from 1 (not diagnostic) to 5 (excellent). Diagnostic criteria included depiction of the germinal matrix, grey and white matter, CSF, brain stem and cerebellum. Signal-difference-to-noise ratios (SDNRs) in the white matter and germinal zone were quantitatively evaluated. Imaging quality improved in 18/20 patients using the navigator echo technique (2.4 {+-} 0.58 vs. 3.65 {+-} 0.73 SD, p < 0.01 for all evaluation criteria). In 2/20 patients fetal movement severely impaired image quality in conventional and navigated HASTE. Navigator-echo imaging revealed additional structural brain abnormalities and confirmed diagnosis in 8/20 patients. The accuracy improved from 50% to 90%. Average SDNR increased from 0.7 {+-} 7.27 to 19.83 {+-} 15.71 (p < 0.01). Navigator-echo-based real-time triggering of fetal head movement is a reliable technique that can deliver diagnostic fetal MR image quality despite vigorous fetal movement. (orig.)

  20. The reduction of image noise and streak artifact in the thoracic inlet during low dose and ultra-low dose thoracic CT

    International Nuclear Information System (INIS)

    Paul, N S; Prezelj, E; Burey, P; Menezes, R J; Blobel, J; Ursani, A; Kashani, H; Siewerdsen, J H

    2010-01-01

    Increased pixel noise and streak artifact reduce CT image quality and limit the potential for radiation dose reduction during CT of the thoracic inlet. We propose to quantify the pixel noise of mediastinal structures in the thoracic inlet, during low-dose (LDCT) and ultralow-dose (uLDCT) thoracic CT, and assess the utility of new software (quantum denoising system and BOOST3D) in addressing these limitations. Twelve patients had LDCT (120 kV, 25 mAs) and uLDCT (120 kV, 10 mAs) images reconstructed initially using standard mediastinal and lung filters followed by the quantum denoising system (QDS) to reduce pixel noise and BOOST3D (B3D) software to correct photon starvation noise as follows: group 1 no QDS, no B3D; group 2 B3D alone; group 3 QDS alone and group 4 both QDS and B3D. Nine regions of interest (ROIs) were replicated on mediastinal anatomy in the thoracic inlet, for each patient resulting in 3456 data points to calculate pixel noise and attenuation. QDS reduced pixel noise by 18.4% (lung images) and 15.8% (mediastinal images) at 25 mAs. B3D reduced pixel noise by ∼8% in the posterior thorax and in combination there was a 35.5% reduction in effective radiation dose (E) for LDCT (1.63-1.05 mSv) in lung images and 32.2% (1.55-1.05 mSv) in mediastinal images. The same combination produced 20.7% reduction (0.53-0.42 mSv) in E for uLDCT, for lung images and 17.3% (0.51-0.42) for mediastinal images. This quantitative analysis of image quality confirms the utility of dedicated processing software in targeting image noise and streak artifact in thoracic LDCT and uLDCT images taken in the thoracic inlet. This processing software potentiates substantial reductions in radiation dose during thoracic LDCT and uLDCT.

  1. Metal artefact reduction in gemstone spectral imaging dual-energy CT with and without metal artefact reduction software

    International Nuclear Information System (INIS)

    Lee, Young Han; Song, Ho-Taek; Kim, Sungjun; Suh, Jin-Suck; Park, Kwan Kyu

    2012-01-01

    To assess the usefulness of gemstone spectral imaging (GSI) dual-energy CT (DECT) with/without metal artefact reduction software (MARs). The DECTs were performed using fast kV-switching GSI between 80 and 140 kV. The CT data were retro-reconstructed with/without MARs, by different displayed fields-of-view (DFOV), and with synthesised monochromatic energy in the range 40-140 keV. A phantom study of size and CT numbers was performed in a titanium plate and a stainless steel plate. A clinical study was performed in 26 patients with metallic hardware. All images were retrospectively reviewed in terms of the visualisation of periprosthetic regions and the severity of beam-hardening artefacts by using a five-point scale. The GSI-MARs reconstruction can markedly reduce the metal-related artefacts, and the image quality was affected by the prosthesis composition and DFOV. The spectral CT numbers of the prosthesis and periprosthetic regions showed different patterns on stainless steel and titanium plates. Dual-energy CT with GSI-MARs can reduce metal-related artefacts and improve the delineation of the prosthesis and periprosthetic region. We should be cautious when using GSI-MARs because the image quality was affected by the prosthesis composition, energy (in keV) and DFOV. The metallic composition and size should be considered in metallic imaging with GSI-MARs reconstruction. circle Metal-related artefacts can be troublesome on musculoskeletal computed tomography (CT). circle Gemstone spectral imaging (GSI) with dual-energy CT (DECT) offers a novel solution circle GSI and metallic artefact reduction software (GSI-MAR) can markedly reduce these artefacts. circle However image quality is influenced by the prosthesis composition and other parameters. circle We should be aware about potential overcorrection when using GSI-MARs. (orig.)

  2. Tuning of CO2 Reduction Selectivity on Metal Electrocatalysts.

    Science.gov (United States)

    Wang, Yuhang; Liu, Junlang; Wang, Yifei; Al-Enizi, Abdullah M; Zheng, Gengfeng

    2017-11-01

    Climate change, caused by heavy CO 2 emissions, is driving new demands to alleviate the rising concentration of atmospheric CO 2 levels. Enlightened by the photosynthesis of green plants, photo(electro)chemical catalysis of CO 2 reduction, also known as artificial photosynthesis, is emerged as a promising candidate to address these demands and is widely investigated during the past decade. Among various artificial photosynthetic systems, solar-driven electrochemical CO 2 reduction is widely recognized to possess high efficiencies and potentials for practical application. The efficient and selective electroreduction of CO 2 is the key to the overall solar-to-chemical efficiency of artificial photosynthesis. Recent studies show that various metallic materials possess the capability to play as electrocatalysts for CO 2 reduction. In order to achieve high selectivity for CO 2 reduction products, various efforts are made including studies on electrolytes, crystal facets, oxide-derived catalysts, electronic and geometric structures, nanostructures, and mesoscale phenomena. In this Review, these methods for tuning the selectivity of CO 2 electrochemical reduction of metallic catalysts are summarized. The challenges and perspectives in this field are also discussed. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Off-Resonance Suppression for Multispectral MR Imaging Near Metallic Implants

    NARCIS (Netherlands)

    den Harder, J. Chiel; van Yperen, Gert H.; Blume, Ulrike A.; Bos, Clemens

    Purpose: Metal artifact reduction in MRI within clinically feasible scan-times without through-plane aliasing. Theory and Methods: Existing metal artifact reduction techniques include view angle tilting (VAT), which resolves in-plane distortions, and multispectral imaging (MSI) techniques, such as

  4. Sulfate Reduction Remediation of a Metals Plume Through Organic Injection

    International Nuclear Information System (INIS)

    Phifer, M.A.

    2003-01-01

    Laboratory testing and a field-scale demonstration for the sulfate reduction remediation of an acidic/metals/sulfate groundwater plume at the Savannah River Site has been conducted. The laboratory testing consisted of the use of anaerobic microcosms to test the viability of three organic substrates to promote microbially mediated sulfate reduction. Based upon the laboratory testing, soybean oil and sodium lactate were selected for injection during the subsequent field-scale demonstration. The field-scale demonstration is currently ongoing. Approximately 825 gallons (3,123 L) of soybean oil and 225 gallons (852 L) of 60 percent sodium lactate have been injected into an existing well system within the plume. Since the injections, sulfate concentrations in the injection zone have significantly decreased, sulfate-reducing bacteria concentrations have significantly increased, the pH has increased, the Eh has decreased, and the concentrations of many metals have decreased. Microbially mediated sulfate reduction has been successfully promoted for the remediation of the acidic/metals/sulfate plume by the injection of soybean oil and sodium lactate within the plume

  5. Artifacts in Magnetic Resonance Imaging

    International Nuclear Information System (INIS)

    Krupa, Katarzyna; Bekiesińska-Figatowska, Monika

    2015-01-01

    Artifacts in magnetic resonance imaging and foreign bodies within the patient’s body may be confused with a pathology or may reduce the quality of examinations. Radiologists are frequently not informed about the medical history of patients and face postoperative/other images they are not familiar with. A gallery of such images was presented in this manuscript. A truncation artifact in the spinal cord could be misinterpreted as a syrinx. Motion artifacts caused by breathing, cardiac movement, CSF pulsation/blood flow create a ghost artifact which can be reduced by patient immobilization, or cardiac/respiratory gating. Aliasing artifacts can be eliminated by increasing the field of view. An artificially hyperintense signal on FLAIR images can result from magnetic susceptibility artifacts, CSF/vascular pulsation, motion, but can also be found in patients undergoing MRI examinations while receiving supplemental oxygen. Metallic and other foreign bodies which may be found on and in patients’ bodies are the main group of artifacts and these are the focus of this study: e.g. make-up, tattoos, hairbands, clothes, endovascular embolization, prostheses, surgical clips, intraorbital and other medical implants, etc. Knowledge of different types of artifacts and their origin, and of possible foreign bodies is necessary to eliminate them or to reduce their negative influence on MR images by adjusting acquisition parameters. It is also necessary to take them into consideration when interpreting the images. Some proposals of reducing artifacts have been mentioned. Describing in detail the procedures to avoid or limit the artifacts would go beyond the scope of this paper but technical ways to reduce them can be found in the cited literature

  6. Reduction of metal oxides in metal carbide fusion superheated with plasma

    Energy Technology Data Exchange (ETDEWEB)

    Hedai, L

    1981-01-01

    A significant part of metals is capable of binding a high quantity of carbon in the form of carbide. The carbide fusion produced as a result of smelting and superheating, metal carbides with the use of plasma might be a medium to be utilized for the reduction of different metal oxides, whilst also the original carbide structure of the metal carbides will be reduced to metallic structure. The experiments conducted by making use of plasma equipment, of 20, 55 and 100 kW performances are described. On the basis of the results of the experiments performed, the following statements are to be made. The oxide reductions taking place in the metal carbide fusion might also be carried out in open-hearth furnaces, because reducing atmosphere is not necessitated during this procedure. The quantity of energy required is basically defined by the energy needed for smelting and superheating the metal carbide. The method for producing the metal described may be mainly applied for the allied production of high-purity steels as well as for that of ferro-alloys.

  7. Thermal simulation of the magnesium thermal of metallic uranium reduction

    International Nuclear Information System (INIS)

    Borges, W.A.; Saliba-Silva, A.M.

    2008-01-01

    Metallic uranium production is vital to fabricate fuel elements for nuclear research reactors and to produce radioisotopes and radiopharmaceuticals. Metallic uranium is got via magnesiothermal reduction of UF 4 . This reaction is carried out inside a closed graphite crucible inserted in a metallic reactor adequately sealed without any outside contact. The assembled set is gradually heated up inside a pit furnace up to reach the reaction ignition temperature (between 600-650 deg C). The optimization of the reactive system depends on the mathematical modeling using simulation by finite elements and computational calculation with specialized programs. In this way, the reactants' thermal behavior is forecast until they reach the ignition temperature. The optimization of the uranium production reaction is based on minimization of thermal losses using better the exo thermal reaction heat. As lower the thermal losses, as higher would be the heat amount to raise the temperature of reaction products. This promotes the adequate melting of uranium and slag, so allowing better metal/slag separation with higher metallic yield. This work shows how the mathematical simulation is made and supplies some preliminary results. (author)

  8. Dynamics in artifact ecologies

    DEFF Research Database (Denmark)

    Bødker, Susanne; Klokmose, Clemens Nylandsted

    2012-01-01

    We increasingly interact with multiple interactive artifacts with overlapping capabilities during our daily activities. It has previously been shown that the use of an interactive artifact cannot be understood in isolation, but artifacts must be understood as part of an artifact ecology, where...... artifacts influence the use of others. Understanding this interplay becomes more and more essential for interaction design as our artifact ecologies grow. This paper continues a recent discourse on artifact ecologies. Through interviews with iPhone users, we demonstrate that relationships between artifacts...... in artifact ecologies cannot be understood as static, instead they evolve dynamically over time. We provide activity theory-based concepts to explain these dynamics....

  9. Microbial links between sulfate reduction and metal retention in uranium- and heavy metal-contaminated soil

    DEFF Research Database (Denmark)

    Sitte, Jana; Akob, Denise M.; Kaufmann, Christian

    2010-01-01

    Sulfate-reducing bacteria (SRB) can affect metal mobility either directly by reductive transformation of metal ions, e.g., uranium, into their insoluble forms or indirectly by formation of metal sulfides. This study evaluated in situ and biostimulated activity of SRB in groundwater-influenced soils...... from a creek bank contaminated with heavy metals and radionuclides within the former uranium mining district of Ronneburg, Germany. In situ activity of SRB, measured by the 35SO42– radiotracer method, was restricted to reduced soil horizons with rates of 142 ± 20 nmol cm–3 day–1. Concentrations...... of heavy metals were enriched in the solid phase of the reduced horizons, whereas pore water concentrations were low. X-ray absorption near-edge structure (XANES) measurements demonstrated that 80% of uranium was present as reduced uranium but appeared to occur as a sorbed complex. Soil-based dsrAB clone...

  10. Synthesis of uranium metal using laser-initiated reduction of uranium tetrafluoride by calcium metal

    International Nuclear Information System (INIS)

    West, M.H.; Martinez, M.M.; Nielsen, J.B.; Court, D.C.; Appert, Q.D.

    1995-09-01

    Uranium metal has numerous uses in conventional weapons (armor penetrators) and nuclear weapons. It also has application to nuclear reactor designs utilizing metallic fuels--for example, the former Integral Fast Reactor program at Argonne National Laboratory. Uranium metal also has promise as a material of construction for spent-nuclear-fuel storage casks. A new avenue for the production of uranium metal is presented that offers several advantages over existing technology. A carbon dioxide (CO 2 ) laser is used to initiate the reaction between uranium tetrafluoride (UF 4 ) and calcium metal. The new method does not require induction heating of a closed system (a pressure vessel) nor does it utilize iodine (I 2 ) as a chemical booster. The results of five reductions of UF 4 , spanning 100 to 200 g of uranium, are evaluated, and suggestions are made for future work in this area

  11. 1,4-Dihydroxy fatty acids: Artifacts by reduction of di- and polyunsaturated fatty acids with sodium borohydride

    Science.gov (United States)

    Thiemt, Simone; Spiteller, Gerhard

    1997-01-01

    In an effort to detect lipid peroxidation products in human blood plasma, samples were treated with NaBH4 to reduce the reactive hydroperoxides to hydroxy compounds. After saponification of the lipids, the free fatty acid fraction obtained by extraction was methylated and separated by TLC. The fractions containing polar compounds were trimethylsilylated and subjected to gas chromatography-mass spectrometry (GC/MS). Mass spectra allowed us to detect previously unknown 1,4-dihydroxy fatty acids due to their typical fragmentation pattern. If the reduction was carried out with NaBD4 instead of NaBH4, incorporation of two deuterium atoms was observed (appropriate mass shift). The two oxygen atoms of the hydroxyl groups were incorporated from air as shown by an experiment in 18O2 atmosphere. The reaction required the presence of free acids, indicating that BH3 was liberated, added to a 1,4-pentadiene system, and finally produced 1,4-diols by air oxidation.

  12. Volume Reduction of Decommissioning Radioactive Burnable and Metal Wastes

    Energy Technology Data Exchange (ETDEWEB)

    Min, B. Y.; Lee, Y. J.; Yun, G. S.; Lee, K. W.; Moon, J. K. [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Choi, Y. K.; Cho, J. H. [SunKwang Atomic Energy Safety Co., Seoul (Korea, Republic of)

    2014-10-15

    A large quantity of radioactive waste was generated during the decommissioning projects. For the purpose of the volume reduction and clearance for decommissioning wastes from decommissioning projects, the incineration and high melting technology has been selected for the decommissioning wastes treatment. The volume reduction of the combustible wastes through the incineration technologies has merits from the view point of a decrease in the amount of waste to be disposed of resulting in a reduction of the disposal cost. Incineration is generally accepted as a method of reducing the volume of radioactive waste. The incineration technology is an effective treatment method that contains hazardous chemicals as well as radioactive contamination. Incinerator burns waste at high temperature. Incineration of a mixture of chemically hazardous and radioactive materials, known as 'mixed waste,' has two principal goals: to reduce the volume and total chemical toxicity of the waste. Incineration itself does not destroy the metals or reduce the radioactivity of the waste. A proven melting technology is currently used for low-level waste (LLW) at several facilities worldwide. These facilities use melting as a means of processing LLW for unrestricted release of the metal or for recycling within the nuclear sector. About 16.4 tons of decommissioning combustible waste has been treated using Oxygen Enriched incineration. The incineration facility operated quite smoothly through the analysis major critical parameters of off-gas.

  13. Volume Reduction of Decommissioning Radioactive Burnable and Metal Wastes

    International Nuclear Information System (INIS)

    Min, B. Y.; Lee, Y. J.; Yun, G. S.; Lee, K. W.; Moon, J. K.; Choi, Y. K.; Cho, J. H.

    2014-01-01

    A large quantity of radioactive waste was generated during the decommissioning projects. For the purpose of the volume reduction and clearance for decommissioning wastes from decommissioning projects, the incineration and high melting technology has been selected for the decommissioning wastes treatment. The volume reduction of the combustible wastes through the incineration technologies has merits from the view point of a decrease in the amount of waste to be disposed of resulting in a reduction of the disposal cost. Incineration is generally accepted as a method of reducing the volume of radioactive waste. The incineration technology is an effective treatment method that contains hazardous chemicals as well as radioactive contamination. Incinerator burns waste at high temperature. Incineration of a mixture of chemically hazardous and radioactive materials, known as 'mixed waste,' has two principal goals: to reduce the volume and total chemical toxicity of the waste. Incineration itself does not destroy the metals or reduce the radioactivity of the waste. A proven melting technology is currently used for low-level waste (LLW) at several facilities worldwide. These facilities use melting as a means of processing LLW for unrestricted release of the metal or for recycling within the nuclear sector. About 16.4 tons of decommissioning combustible waste has been treated using Oxygen Enriched incineration. The incineration facility operated quite smoothly through the analysis major critical parameters of off-gas

  14. Periodic additive noises reduction in 3D images used in building of voxel phantoms through an efficient implementation of the 3D FFT: zipper artifacts filtering

    International Nuclear Information System (INIS)

    Oliveira, Alex C.H. de; Lima, Fernando R.A.; Vieira, Jose W.; Leal Neto, Viriato

    2009-01-01

    The anthropomorphic models used in computational dosimetry are predominantly build from scanning CT (Computed Tomography) or MRI (Magnetic Resonance Imaging) image stacks obtained of patients or volunteers. The building of these stacks (usually called of voxel phantoms or tomography phantoms) requires computer processing to be used in an exposure computational model. Noises present in these stacks can be confused with significant structures. In a 3D image with periodic additive noise in the frequency domain, the noise is fully added to its central slice. The discrete Fourier transform is the fundamental mathematical tool that allows the switch of the spatial domain for the frequency domain, and vice versa. The FFT (fast Fourier transform) algorithm is an ideal computational tool for this switch in domain with efficiency. This paper presents a new methodology for implementation in managed C++ language (Microsoft Visual Studio R .NET) of the fast Fourier transform of 3D digital images (FFT3D) using, essentially, the trigonometric recombination. The reduction of periodic additive noise consists in filtering only the central slice of 3D image in the frequency domain and transforms it back into the spatial domain through the inverse FFT3D. An example of application of this method it is the zipper artifacts filtering in images of MRI. These processes were implemented in the software DIP (Digital Image Processing). (author)

  15. Functional Role of Infective Viral Particles on Metal Reduction

    Energy Technology Data Exchange (ETDEWEB)

    Coates, John D.

    2014-04-01

    A proposed strategy for the remediation of uranium (U) contaminated sites was based on the immobilization of U by reducing the oxidized soluble U, U(VI), to form a reduced insoluble end product, U(IV). Previous studies identified Geobacter sp., including G. sulfurreducens and G. metallireducens, as predominant U(VI)-reducing bacteria under acetate-oxidizing and U(VI)-reducing conditions. Examination of the finished genome sequence annotation of the canonical metal reducing species Geobacter sulfurreducens strain PCA and G. metallireduceans strain GS-15 as well as the draft genome sequence of G. uraniumreducens strain Rf4 identified phage related proteins. In addition, the completed genome for Anaeromyxobacter dehalogenans and the draft genome sequence of Desulfovibrio desulfuricans strain G20, two more model metal-reducing bacteria, also revealed phage related sequences. The presence of these gene sequences indicated that Geobacter spp., Anaeromyxobacter spp., and Desulfovibrio spp. are susceptible to viral infection. Furthermore, viral populations in soils and sedimentary environments in the order of 6.4×10{sup 6}–2.7×10{sup 10} VLP’s cm{sup -3} have been observed. In some cases, viral populations exceed bacterial populations in these environments suggesting that a relationship may exist between viruses and bacteria. Our preliminary screens of samples collected from the ESR FRC indicated that viral like particles were observed in significant numbers. The objective of this study was to investigate the potential functional role viruses play in metal reduction specifically Fe(III) and U(VI) reduction, the environmental parameters affecting viral infection of metal reducing bacteria, and the subsequent effects on U transport.

  16. Microbial links between sulfate reduction and metal retention in uranium- and heavy metal-contaminated soil.

    Science.gov (United States)

    Sitte, Jana; Akob, Denise M; Kaufmann, Christian; Finster, Kai; Banerjee, Dipanjan; Burkhardt, Eva-Maria; Kostka, Joel E; Scheinost, Andreas C; Büchel, Georg; Küsel, Kirsten

    2010-05-01

    Sulfate-reducing bacteria (SRB) can affect metal mobility either directly by reductive transformation of metal ions, e.g., uranium, into their insoluble forms or indirectly by formation of metal sulfides. This study evaluated in situ and biostimulated activity of SRB in groundwater-influenced soils from a creek bank contaminated with heavy metals and radionuclides within the former uranium mining district of Ronneburg, Germany. In situ activity of SRB, measured by the (35)SO(4)(2-) radiotracer method, was restricted to reduced soil horizons with rates of metals were enriched in the solid phase of the reduced horizons, whereas pore water concentrations were low. X-ray absorption near-edge structure (XANES) measurements demonstrated that approximately 80% of uranium was present as reduced uranium but appeared to occur as a sorbed complex. Soil-based dsrAB clone libraries were dominated by sequences affiliated with members of the Desulfobacterales but also the Desulfovibrionales, Syntrophobacteraceae, and Clostridiales. [(13)C]acetate- and [(13)C]lactate-biostimulated soil microcosms were dominated by sulfate and Fe(III) reduction. These processes were associated with enrichment of SRB and Geobacteraceae; enriched SRB were closely related to organisms detected in soils by using the dsrAB marker. Concentrations of soluble nickel, cobalt, and occasionally zinc declined uranium increased in carbon-amended treatments, reaching metal attenuation and (ii) the fate of uranium mobility is not predictable and may lead to downstream contamination of adjacent ecosystems.

  17. Coronary Stent Artifact Reduction with an Edge-Enhancing Reconstruction Kernel - A Prospective Cross-Sectional Study with 256-Slice CT.

    Science.gov (United States)

    Tan, Stéphanie; Soulez, Gilles; Diez Martinez, Patricia; Larrivée, Sandra; Stevens, Louis-Mathieu; Goussard, Yves; Mansour, Samer; Chartrand-Lefebvre, Carl

    2016-01-01

    Metallic artifacts can result in an artificial thickening of the coronary stent wall which can significantly impair computed tomography (CT) imaging in patients with coronary stents. The objective of this study is to assess in vivo visualization of coronary stent wall and lumen with an edge-enhancing CT reconstruction kernel, as compared to a standard kernel. This is a prospective cross-sectional study involving the assessment of 71 coronary stents (24 patients), with blinded observers. After 256-slice CT angiography, image reconstruction was done with medium-smooth and edge-enhancing kernels. Stent wall thickness was measured with both orthogonal and circumference methods, averaging thickness from diameter and circumference measurements, respectively. Image quality was assessed quantitatively using objective parameters (noise, signal to noise (SNR) and contrast to noise (CNR) ratios), as well as visually using a 5-point Likert scale. Stent wall thickness was decreased with the edge-enhancing kernel in comparison to the standard kernel, either with the orthogonal (0.97 ± 0.02 versus 1.09 ± 0.03 mm, respectively; pkernel generated less overestimation from nominal thickness compared to the standard kernel, both with the orthogonal (0.89 ± 0.19 versus 1.00 ± 0.26 mm, respectively; pkernel was associated with lower SNR and CNR, as well as higher background noise (all p kernel. Stent visual scores were higher with the edge-enhancing kernel (pkernel generates thinner stent walls, less overestimation from nominal thickness, and better image quality scores than the standard kernel.

  18. Reducing artifacts from varying projection truncations

    DEFF Research Database (Denmark)

    Borg, Leise; Jørgensen, Jakob Sauer; Frikel, Jürgen

    We study samples with full and partial occlusion causing streak artifacts, and propose two modifications of filtered backprojection for artifact removal. Data is obtained by the SPring-8 synchrotron using a monochromatic parallel-beam scan [1]. Thresholding in the sinogram segments the metal...

  19. The effect of metal artifacts on the identification of vertical root fractures using different fields of view in cone-beam computed tomography

    Energy Technology Data Exchange (ETDEWEB)

    Moudi, Ehsan; Haghanifar, Sina; Madani, Zahrasadat; Bijani, Ali; Nabavi, Zeynab Sadat [Babol University of Medical Science, Babol (Iran, Islamic Republic of)

    2015-09-15

    The aim of this study was to investigate the effects of metal artifacts on the accurate diagnosis of root fractures using cone-beam computed tomography (CBCT) images with large and small/limited fields of view (FOVs). Forty extracted molar and premolar teeth were collected. Access canals were made in all teeth using a rotary system. In half of the teeth, fractures were created by the application of mild pressure with a hammer. The teeth were then randomly put into a wax rim on an acryl base designed in the shape of a mandible. CBCT scans were obtained using a Newtom 5G system with FOVs of 18 cm×16 cm and 6 cm×6 cm. A metal pin was then placed into each tooth, and CBCT imaging was again performed using the same fields of view. All scans were evaluated by two oral and maxillofacial radiologists. The specificity, sensitivity, positive predictive value, negative predictive value, and likelihood ratios (positive and negative) were calculated. The maximum levels of sensitivity and specificity (100% and 100%, respectively) were observed in small volume CBCT scans of teeth without pins. The highest negative predictive value was found in the small-volume group without pins, whereas the positive predictive value was 100% in all groups except the large-volume group with pins.

  20. Artifacts in digital radiography

    Energy Technology Data Exchange (ETDEWEB)

    Min, Jung Whan [Dept. of Radiological Technology, Shin Gu University, Sungnam (Korea, Republic of); Kim, Jung Min [Dept. of Radiological Technology, Korea University, Seoul (Korea, Republic of); Jeong, Hoi Woun [Dept. of Radiological Technology, Beakseok Culture University, Cheonan (Korea, Republic of)

    2015-12-15

    Digital Radiography is a big part of diagnostic radiology. Because uncorrected digital radiography image supported false effect of Patient’s health care. We must be manage the correct digital radiography image. Thus, the artifact images can have effect to make a wrong diagnosis. We report types of occurrence by analyzing the artifacts that occurs in digital radiography system. We had collected the artifacts occurred in digital radiography system of general hospital from 2007 to 2014. The collected data had analyzed and then had categorize as the occurred causes. The artifacts could be categorized by hardware artifacts, software artifacts, operating errors, system artifacts, and others. Hardware artifact from a Ghost artifact that is caused by lag effect occurred most frequently. The others cases are the artifacts caused by RF noise and foreign body in equipments. Software artifacts are many different types of reasons. The uncorrected processing artifacts and the image processing error artifacts occurred most frequently. Exposure data recognize (EDR) error artifacts, the processing error of commissural line, and etc., the software artifacts were caused by various reasons. Operating artifacts were caused when the user did not have the full understanding of the digital medical image system. System artifacts had appeared the error due to DICOM header information and the compression algorithm. The obvious artifacts should be re-examined, and it could result in increasing the exposure dose of the patient. The unclear artifact leads to a wrong diagnosis and added examination. The ability to correctly determine artifact are required. We have to reduce the artifact occurrences by understanding its characteristic and providing sustainable education as well as the maintenance of the equipments.

  1. Artifacts in digital radiography

    International Nuclear Information System (INIS)

    Min, Jung Whan; Kim, Jung Min; Jeong, Hoi Woun

    2015-01-01

    Digital Radiography is a big part of diagnostic radiology. Because uncorrected digital radiography image supported false effect of Patient’s health care. We must be manage the correct digital radiography image. Thus, the artifact images can have effect to make a wrong diagnosis. We report types of occurrence by analyzing the artifacts that occurs in digital radiography system. We had collected the artifacts occurred in digital radiography system of general hospital from 2007 to 2014. The collected data had analyzed and then had categorize as the occurred causes. The artifacts could be categorized by hardware artifacts, software artifacts, operating errors, system artifacts, and others. Hardware artifact from a Ghost artifact that is caused by lag effect occurred most frequently. The others cases are the artifacts caused by RF noise and foreign body in equipments. Software artifacts are many different types of reasons. The uncorrected processing artifacts and the image processing error artifacts occurred most frequently. Exposure data recognize (EDR) error artifacts, the processing error of commissural line, and etc., the software artifacts were caused by various reasons. Operating artifacts were caused when the user did not have the full understanding of the digital medical image system. System artifacts had appeared the error due to DICOM header information and the compression algorithm. The obvious artifacts should be re-examined, and it could result in increasing the exposure dose of the patient. The unclear artifact leads to a wrong diagnosis and added examination. The ability to correctly determine artifact are required. We have to reduce the artifact occurrences by understanding its characteristic and providing sustainable education as well as the maintenance of the equipments

  2. Mesoscale hybrid calibration artifact

    Science.gov (United States)

    Tran, Hy D.; Claudet, Andre A.; Oliver, Andrew D.

    2010-09-07

    A mesoscale calibration artifact, also called a hybrid artifact, suitable for hybrid dimensional measurement and the method for make the artifact. The hybrid artifact has structural characteristics that make it suitable for dimensional measurement in both vision-based systems and touch-probe-based systems. The hybrid artifact employs the intersection of bulk-micromachined planes to fabricate edges that are sharp to the nanometer level and intersecting planes with crystal-lattice-defined angles.

  3. Dosimetric Evaluation of Metal Artefact Reduction using Metal Artefact Reduction (MAR) Algorithm and Dual-energy Computed Tomography (CT) Method

    Science.gov (United States)

    Laguda, Edcer Jerecho

    Purpose: Computed Tomography (CT) is one of the standard diagnostic imaging modalities for the evaluation of a patient's medical condition. In comparison to other imaging modalities such as Magnetic Resonance Imaging (MRI), CT is a fast acquisition imaging device with higher spatial resolution and higher contrast-to-noise ratio (CNR) for bony structures. CT images are presented through a gray scale of independent values in Hounsfield units (HU). High HU-valued materials represent higher density. High density materials, such as metal, tend to erroneously increase the HU values around it due to reconstruction software limitations. This problem of increased HU values due to metal presence is referred to as metal artefacts. Hip prostheses, dental fillings, aneurysm clips, and spinal clips are a few examples of metal objects that are of clinical relevance. These implants create artefacts such as beam hardening and photon starvation that distort CT images and degrade image quality. This is of great significance because the distortions may cause improper evaluation of images and inaccurate dose calculation in the treatment planning system. Different algorithms are being developed to reduce these artefacts for better image quality for both diagnostic and therapeutic purposes. However, very limited information is available about the effect of artefact correction on dose calculation accuracy. This research study evaluates the dosimetric effect of metal artefact reduction algorithms on severe artefacts on CT images. This study uses Gemstone Spectral Imaging (GSI)-based MAR algorithm, projection-based Metal Artefact Reduction (MAR) algorithm, and the Dual-Energy method. Materials and Methods: The Gemstone Spectral Imaging (GSI)-based and SMART Metal Artefact Reduction (MAR) algorithms are metal artefact reduction protocols embedded in two different CT scanner models by General Electric (GE), and the Dual-Energy Imaging Method was developed at Duke University. All three

  4. Reduction of thoracic aorta motion artifact with high-pitch 128-slice dual-source computed tomographic angiography: a historical control study.

    Science.gov (United States)

    Nakagawa, Junichiro; Tasaki, Osamu; Watanabe, Yoshiyuki; Azuma, Takeo; Ohnishi, Mitsuo; Ukai, Isao; Tahara, Kenichi; Ogura, Hiroshi; Kuwagata, Yasuyuki; Hamasaki, Toshimitsu; Shimazu, Takeshi

    2013-01-01

    Electrocardiogram-gated imaging combined with multi-detector row computed tomography (MDCT) has reduced cardiac motion artifacts, but it was not practical in the emergency setting. The purpose of this study was to evaluate the ability of a high-pitch, 128-slice dual-source CT (DSCT) scanner to reduce motion artifacts in patients admitted to the emergency room. This study comprised 100 patients suspected of having thoracic aorta lesions. We examined 47 patients with the 128-slice DSCT scanner (DSCT group), and 53 patients were examined with a 64-slice MDCT scanner (MDCT group). Six anatomic areas in the thoracic aorta were evaluated. Computed tomography images in the DSCT group were distinct, and significant differences were observed in images of all areas between the 2 groups except for the descending aorta. The high-pitch DSCT scanner can reduce motion artifacts of the thoracic aorta and enable radiological diagnosis even in patients with tachycardia and without breath hold.

  5. Modeling susceptibility difference artifacts produced by metallic implants in magnetic resonance imaging with point-based thin-plate spline image registration.

    Science.gov (United States)

    Pauchard, Y; Smith, M; Mintchev, M

    2004-01-01

    Magnetic resonance imaging (MRI) suffers from geometric distortions arising from various sources. One such source are the non-linearities associated with the presence of metallic implants, which can profoundly distort the obtained images. These non-linearities result in pixel shifts and intensity changes in the vicinity of the implant, often precluding any meaningful assessment of the entire image. This paper presents a method for correcting these distortions based on non-rigid image registration techniques. Two images from a modelled three-dimensional (3D) grid phantom were subjected to point-based thin-plate spline registration. The reference image (without distortions) was obtained from a grid model including a spherical implant, and the corresponding test image containing the distortions was obtained using previously reported technique for spatial modelling of magnetic susceptibility artifacts. After identifying the nonrecoverable area in the distorted image, the calculated spline model was able to quantitatively account for the distortions, thus facilitating their compensation. Upon the completion of the compensation procedure, the non-recoverable area was removed from the reference image and the latter was compared to the compensated image. Quantitative assessment of the goodness of the proposed compensation technique is presented.

  6. Effect of the dose and route of administration of butylscopolamine on the reduction of the artifacts associated with intestinal peristalsis in abdominal magnetic resonance

    International Nuclear Information System (INIS)

    Dosda, R.; Marti-Bonmati, L.; Ronchera-Oms, C.

    1999-01-01

    To compare the effect of the route of administration (intravenous and oral) and the dose (40 mg and 80 mg) of butylscopolamine, determining its efficacy in reducing the noise associated with gastrointestinal movement in magnetic resonance (MR) images and the incidence and severity of associated adverse reactions. The present prospective, controlled, double-blind study included 80 patients who underwent abdominal MR. All the patients were given oral, high-density barium sulfate and were divided randomly into 4 groups of 20 patients each: a control group and 3 groups treated with 40 mg or 80 mg of oral butylscopolamine or 40 mg of intravenous butylscopolamine. Both the barium and the oral solutions were administered 25 to 30 minutes before the examination. the MR images were obtained with a STIR sequence (1487/100/44), and qualitative analysis of the noise was carried out using regions of interest situated in the background. The gastrointestinal noise was defined both by the mean and the standard deviation of the signal intensity of the air front of an behind the patient. The standard deviation of the air beside the patient was determined to confirm the absence of variations in noise inherent to MR. The adverse reactions to MR after 2 hours (immediate) and one day (late) were recorded. There were no significant differences among the groups with respect to sex, age or time interval between administration of the oral solution and the start of the sequence. The noise inherent to MR was not significantly different from one group to another (Student-Newman-Keuls test, p=0.71). Both the mean and the standard deviation of the intensity of the air situated in anteroposterior phase-encoding direction were significantly lower in the butylscopolamine groups than in the control group (Student-Newman-Keuls test, p=0.008). The most marked reduction was observed after the oral dose of 80 mg, followed by intravenous injection of 40 mg and the oral dose of 40 mg. Adverse reaction

  7. Zero-Valent Metal Emulsion for Reductive Dehalogenation of DNAPLs

    Science.gov (United States)

    Reinhart, Debra R. (Inventor); Clausen, Christian (Inventor); Gelger, Cherie L. (Inventor); Quinn, Jacqueline (Inventor); Brooks, Kathleen (Inventor)

    2006-01-01

    A zero-valent metal emulsion is used to dehalogenate solvents, such as pooled dense non-aqueous phase liquids (DNAPLs), including trichloroethylene (TCE). The zero-valent metal emulsion contains zero-valent metal particles, a surfactant, oil and water, The preferred zero-valent metal particles are nanoscale and microscale zero-valent iron particles.

  8. Chemical Reduction of SIM MOX in Molten Lithium Chloride Using Lithium Metal Reductant

    Science.gov (United States)

    Kato, Tetsuya; Usami, Tsuyoshi; Kurata, Masaki; Inoue, Tadashi; Sims, Howard E.; Jenkins, Jan A.

    2007-09-01

    A simulated spent oxide fuel in a sintered pellet form, which contained the twelve elements U, Pu, Am, Np, Cm, Ce, Nd, Sm, Ba, Zr,Mo, and Pd, was reduced with Li metal in a molten LiCl bath at 923 K. More than 90% of U and Pu were reduced to metal to form a porous alloy without significant change in the Pu/U ratio. Small fractions of Pu were also combined with Pd to form stable alloys. In the gap of the porous U-Pu alloy, the aggregation of the rare-earth (RE) oxide was observed. Some amount of the RE elements and the actinoides leached from the pellet. The leaching ratio of Am to the initially loaded amount was only several percent, which was far from about 80% obtained in the previous ones on simple MOX including U, Pu, and Am. The difference suggests that a large part of Am existed in the RE oxide rather than in the U-Pu alloy. The detection of the RE elements and actinoides in the molten LiCl bath seemed to indicate that they dissolved into the molten LiCl bath containing the oxide ion, which is the by-product of the reduction, as solubility of RE elements was measured in the molten LiCl-Li2O previously.

  9. Evidence for Single Metal Two Electron Oxidative Addition and Reductive Elimination at Uranium

    OpenAIRE

    Gardner, Benedict M; Kefalidis, Christos E; Lu, Erli; Patel, Dipti; Mcinnes, Eric; Tuna, Floriana; Wooles, Ashley; Maron, Laurent; Liddle, Stephen

    2017-01-01

    Reversible single-metal two-electron oxidative addition and reductive elimination are common fundamental reactions for transition metals that underpin major catalytic transformations. However, these reactions have never been observed together in the f-block because these metals exhibit irreversible one- or multi-electron oxidation or reduction reactions. Here, we report that azobenzene oxidises sterically and electronically unsaturated uranium(III) complexes to afford a uranium(V)-imido compl...

  10. Controllable reductive method for synthesizing metal-containing particles

    Science.gov (United States)

    Moon, Ji-Won; Jung, Hyunsung; Phelps, Tommy Joe; Duty, Chad E.; Ivanov, Ilia N.; Joshi, Pooran Chandra; Jellison, Jr., Gerald Earle; Armstrong, Beth Louise; Smith, Sean Campbell; Rondinone, Adam Justin; Love, Lonnie J.

    2018-03-06

    The invention is directed to a method for producing metal-containing particles, the method comprising subjecting an aqueous solution comprising a metal salt, E.sub.h, lowering reducing agent, pH adjusting agent, and water to conditions that maintain the E.sub.h value of the solution within the bounds of an E.sub.h-pH stability field corresponding to the composition of the metal-containing particles to be produced, and producing said metal-containing particles in said aqueous solution at a selected E.sub.h value within the bounds of said E.sub.h-pH stability field. The invention is also directed to the resulting metal-containing particles as well as devices in which they are incorporated.

  11. Direct reduction of uranium dioxide and few other metal oxides to corresponding metals by high temperature molten salt electrolysis

    International Nuclear Information System (INIS)

    Mohandas, K.S.

    2017-01-01

    Molten salt based electro-reduction processes, capable of directly converting solid metal oxides to metals with minimum intermediate steps, are being studied worldwide. Production of metals apart, the process assumes importance in nuclear technology in the context of pyrochemical reprocessing of spent oxide fuels, for it serves as an intermediate step to convert spent oxide fuel to a metal alloy, which in turn can be processed by molten salt electro-refining method to gain the actinides present in it. In the context of future metal fuel fast reactor programme, the electrochemical process was studied for conversion of solid UO_2 to U metal in LiCl-1wt.% Li_2O melt at 650 °C with platinum anode at the Metal Processing Studies Section, PMPD, IGCAR. A brief overview of the work is presented in the paper

  12. Reduction of CSF flow artifact in fast fluid attenuated inversion recovery MR imaging. Study of excitation width in 180deg inversion pulse

    International Nuclear Information System (INIS)

    Tsuchihashi, Toshio; Yoshizawa, Satoshi; Maki, Toshio; Kitagawa, Matsuo; Suzuki, Ken; Fujita, Isao

    1998-01-01

    A technique that increases slice thickness so that it becomes wider than the excitation width of the 180deg inversion pulse and in which TR is partitioned twice has been investigated with regard to fast FLAIR. This is a technique that reduces the flow artifact of CSF. It is thought that, with this technique, the flow artifact is reduced because the CSF that flows onto the slice reaches the null point. The cross talk effect of the 180deg inversion pulse appears as a high CSF signal. As a result, the number of slices needs to be partitioned two or three times before imaging. Thus the imaging time is doubled or tripled. Considering the cross talk effect of the 180deg inversion pulse and the imaging time needed for this technique, the optimal imaging technique would be one that uses an inversion pulse that is four times slice thickness plus slice space and for which the number of slices is partitioned twice. Furthermore, the null point of CSF was dependent on dividing TR in half. (author)

  13. [Influence of Dissimilatory Iron Reduction on the Speciation and Bioavailability of Heavy Metals in Soil].

    Science.gov (United States)

    Si, You-bin; Wang, Juan

    2015-09-01

    Fe(III) dissimilatory reduction by microbes is an important process of producing energy in the oxidation of organic compounds under anaerobic condition with Fe(III) as the terminal electron acceptor and Fe(II) as the reduction product. This process is of great significance in element biogeochemical cycle. Iron respiration has been described as one of the most ancient forms of microbial metabolism on the earth, which is bound up with material cycle in water, soil and sediments. Dissimilatory iron reduction plays important roles in heavy metal form transformation and the remediation of heavy metal and radionuclide contaminated soils. In this paper, we summarized the research progress of iron reduction in the natural environment, and discussed the influence and the mechanism of dissimilatory iron reduction on the speciation and bioavailability of heavy metals in soil. The effects of dissimilatory iron reduction on the speciation of heavy metals may be attributed to oxidation and reduction, methytation and immobilization of heavy metals in relation to their bioavailability in soils. The mechanisms of Fe(III) dissimilatory reduction on heavy metal form transformation contain biological and chemical interactions, but the mode of interaction remains to be further investigated.

  14. Metal-phthalocyanine functionalized carbon nanotubes as catalyst for the oxygen reduction reaction: A theoretical study

    Science.gov (United States)

    Orellana, Walter

    2012-07-01

    The covalent functionalization of metallic single-walled carbon nanotubes (CNTs) with transition metal phthalocyanines (MPc, with M = Mn, Fe and Co) are addressed by density functional calculations. The CNT-MPc catalytic activity toward the oxygen reduction reaction (ORR) is investigated through the O2 stretching frequency adsorbed on the phthalocyanine metal center. We find better reduction abilities when the CNT functionalization occurs through sp2-like bonds. Multiple stable-spin states for the M-O2 adduct are also found for M = Mn and Fe, suggesting higher ORR rates. The CNT-MPc complexes show metallic characteristics, suggesting favorable conditions to work as ORR cathode catalysts in fuel cells.

  15. Evaluation of artifacts generated by zirconium implants in cone-beam computed tomography images.

    Science.gov (United States)

    Vasconcelos, Taruska Ventorini; Bechara, Boulos B; McMahan, Clyde Alex; Freitas, Deborah Queiroz; Noujeim, Marcel

    2017-02-01

    To evaluate zirconium implant artifact production in cone beam computed tomography images obtained with different protocols. One zirconium implant was inserted in an edentulous mandible. Twenty scans were acquired with a ProMax 3D unit (Planmeca Oy, Helsinki, Finland), with acquisition settings ranging from 70 to 90 peak kilovoltage (kVp) and voxel sizes of 0.32 and 0.16 mm. A metal artifact reduction (MAR) tool was activated in half of the scans. An axial slice through the middle region of the implant was selected for each dataset. Gray values (mean ± standard deviation) were measured in two regions of interest, one close to and the other distant from the implant (control area). The contrast-to-noise ratio was also calculated. Standard deviation decreased with greater kVp and when the MAR tool was used. The contrast-to-noise ratio was significantly higher when the MAR tool was turned off, except for low resolution with kVp values above 80. Selection of the MAR tool and greater kVp resulted in an overall reduction of artifacts in images acquired with low resolution. Although zirconium implants do produce image artifacts in cone-bean computed tomography scans, the setting that best controlled artifact generation by zirconium implants was 90 kVp at low resolution and with the MAR tool turned on. Copyright © 2016 Elsevier Inc. All rights reserved.

  16. Influence of dissimilatory metal reduction on fate of organic and metal contaminants in the subsurface

    Science.gov (United States)

    Lovley, Derek R.; Anderson, Robert T.

    Dissimilatory Fe(III)-reducing microorganisms have the ability to destroy organic contaminants under anaerobic conditions by oxidizing them to carbon dioxide. Some Fe(III)-reducing microorganisms can also reductively dechlorinate chlorinated contaminants. Fe(III)-reducing microorganisms can reduce a variety of contaminant metals and convert them from soluble forms to forms that are likely to be immobilized in the subsurface. Studies in petroleum-contaminated aquifers have demonstrated that Fe(III)-reducing microorganisms can be effective agents in removing aromatic hydrocarbons from groundwater under anaerobic conditions. Laboratory studies have demonstrated the potential for Fe(III)-reducing microorganisms to remove uranium from contaminated groundwaters. The activity of Fe(III)-reducing microorganisms can be stimulated in several ways to enhance organic contaminant oxidation and metal reduction. Molecular analyses in both field and laboratory studies have demonstrated that microorganisms of the genus Geobacter become dominant members of the microbial community when Fe(III)-reducing conditions develop as the result of organic contamination, or when Fe(III) reduction is artificially stimulated. These results suggest that further understanding of the ecophysiology of Geobacter species would aid in better prediction of the natural attenuation of organic contaminants under anaerobic conditions and in the design of strategies for the bioremediation of subsurface metal contamination. Des micro-organismes simulant la réduction du fer ont la capacité de détruire des polluants organiques dans des conditions anérobies en les oxydant en dioxyde de carbone. Certains micro-organismes réducteurs de fer peuvent aussi dé-chlorer par réduction des polluants chlorés. Des micro-organismes réducteurs de fer peuvent réduire tout un ensemble de métaux polluants et les faire passer de formes solubles à des formes qui sont susceptibles d'être immobilisées dans le milieu

  17. Preparation of hafnium metal by calciothermic reduction of HfO2

    International Nuclear Information System (INIS)

    Sharma, I.G.; Vijay, P.L.; Sehra, J.C.; Sundaram, C.V.

    1975-01-01

    Hafnium metal powder has been produced by the calciothermic reduction of hafnium oxide. The influence of various experimental parameters - such as amount of calcium in excess of stoichiometric requirement, temperature, and time of reduction - on the yield and purity of the metal has been studied. The metal powder obtained by reduction at 960 0 C (two hours) with a calcium excess of 70% analysed 600 ppm of oxygen and 147 ppm of nitrogen. A reduction efficiency of 96% has been achieved under these conditions. The refining of the powder by electron beam melting, fused salt electrolysis, and iodide process has been studied. The oxygen content in the metal could be brought down from 6900 to 148 ppm by electron beam melt-refining. (author)

  18. A Universal Method to Engineer Metal Oxide-Metal-Carbon Interface for Highly Efficient Oxygen Reduction.

    Science.gov (United States)

    Lv, Lin; Zha, Dace; Ruan, Yunjun; Li, Zhishan; Ao, Xiang; Zheng, Jie; Jiang, Jianjun; Chen, Hao Ming; Chiang, Wei-Hung; Chen, Jun; Wang, Chundong

    2018-03-27

    Oxygen is the most abundant element in the Earth's crust. The oxygen reduction reaction (ORR) is also the most important reaction in life processes and energy converting/storage systems. Developing techniques toward high-efficiency ORR remains highly desired and a challenge. Here, we report a N-doped carbon (NC) encapsulated CeO 2 /Co interfacial hollow structure (CeO 2 -Co-NC) via a generalized strategy for largely increased oxygen species adsorption and improved ORR activities. First, the metallic Co nanoparticles not only provide high conductivity but also serve as electron donors to largely create oxygen vacancies in CeO 2 . Second, the outer carbon layer can effectively protect cobalt from oxidation and dissociation in alkaline media and as well imparts its higher ORR activity. In the meanwhile, the electronic interactions between CeO 2 and Co in the CeO 2 /Co interface are unveiled theoretically by density functional theory calculations to justify the increased oxygen absorption for ORR activity improvement. The reported CeO 2 -Co-NC hollow nanospheres not only exhibit decent ORR performance with a high onset potential (922 mV vs RHE), half-wave potential (797 mV vs RHE), and small Tafel slope (60 mV dec -1 ) comparable to those of the state-of-the-art Pt/C catalysts but also possess long-term stability with a negative shift of only 7 mV of the half-wave potential after 2000 cycles and strong tolerance against methanol. This work represents a solid step toward high-efficient oxygen reduction.

  19. Small Artifacts - Big Technologies

    DEFF Research Database (Denmark)

    Kreiner, Kristian

    2005-01-01

    The computer IC is the heart of the information and telecommunication technology. It is a tiny artifact, but with incredible organizing powers. We use this physical artifact as the location for studying central problems of the knowledge economy. First, the paper describes the history of chip design...

  20. Trends in oxygen reduction and methanol activation on transition metal chalcogenides

    DEFF Research Database (Denmark)

    Tritsaris, Georgios; Nørskov, Jens Kehlet; Rossmeisl, Jan

    2011-01-01

    We use density functional theory calculations to study the oxygen reduction reaction and methanol activation on selenium and sulfur-containing transition metal surfaces. With ruthenium selenium as a starting point, we study the effect of the chalcogen on the activity, selectivity and stability...... of the catalyst. Ruthenium surfaces with moderate content of selenium are calculated active for the oxygen reduction reaction, and insensitive to methanol. A significant upper limit for the activity of transition metal chalcogenides is estimated....

  1. Reduction of UF4 to U-metal

    International Nuclear Information System (INIS)

    Namkung, H.; Min, B.T.; Kim, J.S.; Whang, S.C.

    1982-01-01

    In the second years of study for the production of the metallic uranium with reactors which can produce 1 Kg and 4 Kg U-metal, various factors on the yield of U-metal and the leaching condition for uranium recovery with nitric acid are examined. The jolter has been used for the charging with liner (MgF 2 ) while the hand-tamping method for the filling of reaction mixtures (UF 4 -Mg) in the reactor, and their average densities are 1.23g/cc and 2.90g/cc, respectively. The various effects on the yield such as magnesium excess, furnace control temperatue, charge densities of liner and reaction mixtures, have been studied but the yields of crude metal production are in the wide range from 93 % down to about 65 %. Generally, six percent magnesium excess produced higher yields than did either 2 or 10 percent excess. The leaching condition for the uranium recovery from slag are also investigated with dilute nitric acid (3-6N) as well as higher concentrated nitric acid (9.5N) but the leaching yields are same in either solution. Uranium recovery from the slag is very effective with dilute nitric acid (3N) leaching for less than one hour at 60degC. (Author)

  2. Optimized protocols for cardiac magnetic resonance imaging in patients with thoracic metallic implants.

    Science.gov (United States)

    Olivieri, Laura J; Cross, Russell R; O'Brien, Kendall E; Ratnayaka, Kanishka; Hansen, Michael S

    2015-09-01

    Cardiac magnetic resonance (MR) imaging is a valuable tool in congenital heart disease; however patients frequently have metal devices in the chest from the treatment of their disease that complicate imaging. Methods are needed to improve imaging around metal implants near the heart. Basic sequence parameter manipulations have the potential to minimize artifact while limiting effects on image resolution and quality. Our objective was to design cine and static cardiac imaging sequences to minimize metal artifact while maintaining image quality. Using systematic variation of standard imaging parameters on a fluid-filled phantom containing commonly used metal cardiac devices, we developed optimized sequences for steady-state free precession (SSFP), gradient recalled echo (GRE) cine imaging, and turbo spin-echo (TSE) black-blood imaging. We imaged 17 consecutive patients undergoing routine cardiac MR with 25 metal implants of various origins using both standard and optimized imaging protocols for a given slice position. We rated images for quality and metal artifact size by measuring metal artifact in two orthogonal planes within the image. All metal artifacts were reduced with optimized imaging. The average metal artifact reduction for the optimized SSFP cine was 1.5+/-1.8 mm, and for the optimized GRE cine the reduction was 4.6+/-4.5 mm (P metal artifact reduction for the optimized TSE images was 1.6+/-1.7 mm (P metal artifact are easily created by modifying basic sequence parameters, and images are superior to standard imaging sequences in both quality and artifact size. Specifically, for optimized cine imaging a GRE sequence should be used with settings that favor short echo time, i.e. flow compensation off, weak asymmetrical echo and a relatively high receiver bandwidth. For static black-blood imaging, a TSE sequence should be used with fat saturation turned off and high receiver bandwidth.

  3. Graphene layer encapsulated metal nanoparticles as a new type of non-precious metal catalysts for oxygen reduction

    DEFF Research Database (Denmark)

    Hu, Yang; Zhong, Lijie; Jensen, Jens Oluf

    2016-01-01

    Cheap and efficient non-precious metal catalysts for oxygen reduction have been a focus of research in the field of low-temperature fuel cells. This review is devoted to a brief summary of the recent work on a new type of catalysts, i.e., the graphene layer encapsulated metal nanoparticles....... The discussion is focused on the synthesis, structure, mechanism, performance, and further research....

  4. The Effect of Metal and Oxide Additions on the Reduction of Chalcocite by Hydrogen

    OpenAIRE

    Balsalobre Casares, Carmen

    2011-01-01

    Copper is widely known as a very important material due to its applications in our daily life, such as electrical devices and heating appliances. It is not so common knowledge that copper is not found in its metallic form, but mixed with other metals and elements like sulphur and oxygen. The process to obtain pure copper nowadays implies a strong impact on the environment. Regarding copper sulphides, its reduction to metallic copper is based in the oxidation of the ore products which forms...

  5. Reduction of metallic coil artefacts in computed tomography body imaging: effects of a new single-energy metal artefact reduction algorithm

    Energy Technology Data Exchange (ETDEWEB)

    Kidoh, Masafumi; Utsunomiya, Daisuke; Ikeda, Osamu; Tamura, Yoshitaka; Oda, Seitaro; Yuki, Hideaki; Nakaura, Takeshi; Hirai, Toshinori; Yamashita, Yasuyuki [Kumamoto University, Department of Diagnostic Radiology, Faculty of Life Sciences, Kumamoto (Japan); Funama, Yoshinori [Kumamoto University, Department of Medical Physics, Faculty of Life Sciences, Kumamoto (Japan); Kawano, Takayuki [Kumamoto University Graduate School, Department of Neurosurgery, Faculty of Life Sciences Research, Kumamoto (Japan)

    2016-05-15

    We evaluated the effect of a single-energy metal artefact reduction (SEMAR) algorithm for metallic coil artefact reduction in body imaging. Computed tomography angiography (CTA) was performed in 30 patients with metallic coils (10 men, 20 women; mean age, 67.9 ± 11 years). Non-SEMAR images were reconstructed with iterative reconstruction alone, and SEMAR images were reconstructed with the iterative reconstruction plus SEMAR algorithms. We compared image noise around metallic coils and the maximum diameters of artefacts from coils between the non-SEMAR and SEMAR images. Two radiologists visually evaluated the metallic coil artefacts utilizing a four-point scale: 1 = extensive; 2 = strong; 3 = mild; 4 = minimal artefacts. The image noise and maximum diameters of the artefacts of the SEMAR images were significantly lower than those of the non-SEMAR images (65.1 ± 33.0 HU vs. 29.7 ± 10.3 HU; 163.9 ± 54.8 mm vs. 10.3 ± 19.0 mm, respectively; P < 0.001). Better visual scores were obtained with the SEMAR technique (3.4 ± 0.6 vs. 1.0 ± 0.0, P < 0.001). The SEMAR algorithm significantly reduced artefacts caused by metallic coils compared with the non-SEMAR algorithm. This technique can potentially increase CT performance for the evaluation of post-coil embolization complications. (orig.)

  6. Reduction of metallic coil artefacts in computed tomography body imaging: effects of a new single-energy metal artefact reduction algorithm

    International Nuclear Information System (INIS)

    Kidoh, Masafumi; Utsunomiya, Daisuke; Ikeda, Osamu; Tamura, Yoshitaka; Oda, Seitaro; Yuki, Hideaki; Nakaura, Takeshi; Hirai, Toshinori; Yamashita, Yasuyuki; Funama, Yoshinori; Kawano, Takayuki

    2016-01-01

    We evaluated the effect of a single-energy metal artefact reduction (SEMAR) algorithm for metallic coil artefact reduction in body imaging. Computed tomography angiography (CTA) was performed in 30 patients with metallic coils (10 men, 20 women; mean age, 67.9 ± 11 years). Non-SEMAR images were reconstructed with iterative reconstruction alone, and SEMAR images were reconstructed with the iterative reconstruction plus SEMAR algorithms. We compared image noise around metallic coils and the maximum diameters of artefacts from coils between the non-SEMAR and SEMAR images. Two radiologists visually evaluated the metallic coil artefacts utilizing a four-point scale: 1 = extensive; 2 = strong; 3 = mild; 4 = minimal artefacts. The image noise and maximum diameters of the artefacts of the SEMAR images were significantly lower than those of the non-SEMAR images (65.1 ± 33.0 HU vs. 29.7 ± 10.3 HU; 163.9 ± 54.8 mm vs. 10.3 ± 19.0 mm, respectively; P < 0.001). Better visual scores were obtained with the SEMAR technique (3.4 ± 0.6 vs. 1.0 ± 0.0, P < 0.001). The SEMAR algorithm significantly reduced artefacts caused by metallic coils compared with the non-SEMAR algorithm. This technique can potentially increase CT performance for the evaluation of post-coil embolization complications. (orig.)

  7. Reduction of vascular artifact on T1-weighted images of the brain by using three-dimensional double IR fast spoiled gradient echo recalled acquisition in the steady state (FSPGR) at 3.0 Tesla

    International Nuclear Information System (INIS)

    Fujiwara, Yasuhiro; Yamaguchi, Isao; Ookoshi, Yusuke; Ootani, Yuriko; Matsuda, Tsuyoshi; Ishimori, Yoshiyuki; Hayashi, Hiroyuki; Miyati, Tosiaki; Kimura, Hirohiko

    2007-01-01

    The purpose of this study was to decrease vascular artifacts caused by the in-flow effect in three-dimensional inversion recovery prepared fast spoiled gradient recalled acquisition in the steady state (3D IR FSPGR) at 3.0 Tesla. We developed 3D double IR FSPGR and investigated the signal characteristics of the new sequence. The 3D double IR FSPGR sequence uses two inversion pulses, the first for obtaining tissue contrast and the second for nulling vascular signal, which is applied at the time of the first IR period at the neck region. We have optimized scan parameters based on both phantom and in-vivo study. As a result, optimized parameters (1st TI=700 ms, 2nd TI=400 ms) successfully have produced much less vessel signal at reduction than conventional 3D IR FSPGR over a wide imaging range, while preserving the signal-to-noise ratio (SNR) and gray/white matter contrast. Moreover, the decreased artifact was also confirmed by visual inspection of the images obtained in vivo using those parameters. Thus, 3D double IR FSPGR was a useful sequence for the acquisition of T1-weighted images at 3.0 Tesla. (author)

  8. Development of supported noble metal catalyst for U(VI) to U(IV) reduction

    International Nuclear Information System (INIS)

    Tyagi, Deepak; Varma, Salil; Bhattacharyya, K.; Tripathi, A.K.; Bharadwaj, S.R.; Jain, V.K.; Sahu, Avinash; Vincent, Tessy; Jagatap, B.N.; Wattal, P.K.

    2015-01-01

    Uranium-plutonium separation is an essential step in the PUREX process employed in spent nuclear fuel reprocessing. This partitioning in the PUREX process is achieved by selective reduction of Pu(IV) to Pu(III) using uranous nitrate as reductant and hydrazine as stabilizer. Currently in our Indian reprocessing plants, the requirement of uranous nitrate is met by electrolytic reduction of uranyl nitrate. This process, however, suffers from a major drawback of incomplete reduction with a maximum conversion of ~ 60%. Catalytic reduction of U(VI) to U(IV) is being considered as one of the promising alternatives to the electro-reduction process due to fast kinetics and near total conversion. Various catalysts involving noble metals like platinum (Adams catalyst, Pt/Al 2 O 3 , Pt/SiO 2 etc.) have been reported for the reduction. Sustained activity and stability of the catalyst under harsh reaction conditions are still the issues that need to be resolved. We present here the results on zirconia supported noble metal catalyst that is developed in BARC for reduction of uranyl nitrate to uranous nitrate. Supported noble metal catalysts with varying metal loadings (0.5 - 2 wt%) were prepared via support precipitation and noble metal impregnation. The green catalysts were reduced either by chemical reduction using hydrazine hydrate or by heating in hydrogen flow or combination of both the steps. These catalysts were characterized by various techniques such as, XRD, SEM, TEM, N 2 adsorption and H 2 chemisorption. Performance of these catalysts was evaluated for U(VI) to U(IV) reduction with uranyl nitrate feed using hydrazine as reductant. The results with the most active catalyst are named as 'BARC-CAT', which was developed in our lab. (author)

  9. Low temperature plasma metallurgy. Reduction of metals in plasma reactors

    Czech Academy of Sciences Publication Activity Database

    Eliáš, M.; Frgala, Z.; Kudrle, V.; Janča, J.; Brožek, Vlastimil

    2004-01-01

    Roč. 7, č. 1 (2004), s. 91-97 ISSN 1203-8407 Institutional research plan: CEZ:AV0Z2043910 Keywords : plasmachemistry reduction, tungsten, hydrogen plasma Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass Impact factor: 0.451, year: 2002

  10. Review on the processes of reduction and refining of metallic vanadium

    International Nuclear Information System (INIS)

    Mourao, M.B.; Capocchi, J.D.T.

    1982-01-01

    A literature survey on the processes of vanadium reduction and refining is presented. The results achieved by several research workers are comented. Enphasis is given to the aluminothermic reduction of V 2 O 5 followed by purification of the crude metal in an electron beam melting furnace or by high temperature molten salts electrolitic processes. (Author) [pt

  11. Preparation of low valent technetium metal-metal bonded species via solvothermal reduction of pertechnetate salts

    International Nuclear Information System (INIS)

    Kerlin, W.M.; Poineau, F.; Forster, P.M.; Czerwinski, K.R.; Sattelberger, A.P.

    2013-01-01

    A new one-step solvothermal synthesis route for reduction of pertechnetate salts to low valent technetium metal-metal bonded dimers will be presented. The reaction of potassium pertechnetate with glacial acetic acid plus either halo acids or halo salts under in-situ hydrogen production by sodium borohydride at various temperatures yields multiple products consisting of tetraacetate Tc-Tc (II,III) and Tc-Tc (III,III) paddle wheel dimers. Solid products isolated and analyzed via Single Crystal X-ray Diffraction (SC-XRD) in these reactions consist of polymeric chains Tc 2 +5 core: Tc 2 (μ-O 2 CCH 3 ) 4 (O 2 CCH 3 ), Tc 2 (μ-O 2 CCH 3 ) 4 Cl, Tc 2 (μ-O 2 CCH 3 ) 4 Br, Tc 2 (μ-O 2 CCH 3 ) 4 I, molecular Tc 2 +5 core: Tc 2 (μ-O 2 CCH 3 ) 3 Cl 2 (H 2 O) 2 ·H 2 O, K[Tc 2 (μ-O 2 CCH 3 ) 4 Br 2 ], and molecular Tc 2 +6 core: Tc 2 (μ-O 2 CCH 3 ) 4 Cl 2 , Tc 2 (μ-O 2 CCH 3 ) 4 Br 2 . Of the compounds listed, four are newly discovered using the one-step technique and two more additions to crystal database. Additional spectroscopic (X-ray Absorbance Fine Structure, UV-Vis, and FT-IR) characterization of the new compounds will be shown and used to propose a mechanism. Analysis of the mother liquor of each reaction by UV-Vis and formation of crystals over time due to oxidation of solutions affords a possible insight into mechanism of the Tc 2 +5 to Tc 2 +6 core formation. The oxidation states of Tc-Tc dimers formed is also dependent on temperature and pH of the starting solutions and will be explained in extensive detail. These one step reactions of reducing Tc(VII) to low valent technetium provides high yield intermediates for potential waste forms, use in nuclear fuel cycle separations, and radiopharmaceuticals. (author)

  12. Investigation of the electrocatalytic activity for oxygen reduction of sputter deposited mixed metal films

    International Nuclear Information System (INIS)

    Schumacher, L.C.; Holzheuter, I.B.; Nucara, M.C.; Dignam, M.J.

    1989-01-01

    Sputter-deposited films of silver with lead, manganese and nickel have been studied as possible oxygen reduction electrocatalysts using cyclic voltammetry, rotating disc studies, steady-state polarization and Auger analysis. In general, the Ag-Pb and Ag-Mn films display superior electrocatalytic activity for O 2 reduction, while the Ag-Ni films' performance is inferior to that of pure Ag. For the Ag-Pb films, which show the highest electrocatalytic activity, the mixed metal films display oxidation-reduction behavior which is not simply a superposition of that of the separate metals, and suggests a mechanism for the improved behavior

  13. Pyrochemical reduction of uranium dioxide and plutonium dioxide by lithium metal

    International Nuclear Information System (INIS)

    Usami, T.; Kurata, M.; Inoue, T.; Sims, H.E.; Beetham, S.A.; Jenkins, J.A.

    2002-01-01

    The lithium reduction process has been developed to apply a pyrochemical recycle process for oxide fuels. This process uses lithium metal as a reductant to convert oxides of actinide elements to metal. Lithium oxide generated in the reduction would be dissolved in a molten lithium chloride bath to enhance reduction. In this work, the solubility of Li 2 O in LiCl was measured to be 8.8 wt% at 650 deg. C. Uranium dioxide was reduced by Li with no intermediate products and formed porous metal. Plutonium dioxide including 3% of americium dioxide was also reduced and formed molten metal. Reduction of PuO 2 to metal also occurred even when the concentration of lithium oxide was just under saturation. This result indicates that the reduction proceeds more easily than the prediction based on the Gibbs free energy of formation. Americium dioxide was also reduced at 1.8 wt% lithium oxide, but was hardly reduced at 8.8 wt%

  14. Reduction Expansion Synthesis of Chromium and Nickel Metal Coatings

    Science.gov (United States)

    2017-06-01

    Garth V. Hobson Chair, Department of Mechanical and Aerospace Engineering iv THIS PAGE INTENTIONALLY LEFT BLANK v ABSTRACT This thesis represents a...chromium and nickel coatings,” Plating and Surface Finishing, vol. 92, no. 4, pp. 42–48, Apr. 2005. [43] S. I. Sandler, Chemical and Engineering ...NAVAL POSTGRADUATE SCHOOL MONTEREY, CALIFORNIA THESIS Approved for public release. Distribution is unlimited. REDUCTION EXPANSION SYNTHESIS OF

  15. High-throughput synthesis of mixed-metal electrocatalysts for CO{sub 2} reduction

    Energy Technology Data Exchange (ETDEWEB)

    He, Jingfu; Dettelbach, Kevan E.; Li, Tengfei [Department of Chemistry, The University of British Columbia, Vancouver, BC (Canada); Salvatore, Danielle A. [Department of Chemical and Biological Engineering, The University of British Columbia, Vancouver, BC (Canada); Berlinguette, Curtis P. [Department of Chemistry, The University of British Columbia, Vancouver, BC (Canada); Department of Chemical and Biological Engineering, The University of British Columbia, Vancouver, BC (Canada)

    2017-05-22

    The utilization of CO{sub 2} as a feedstock requires fundamental breakthroughs in catalyst design. The efficiencies and activities of pure metal electrodes towards the CO{sub 2} reduction reaction are established, but the corresponding data on mixed-metal systems are not as well developed. In this study we show that the near-infrared driven decomposition (NIRDD) of solution-deposited films of metal salts and subsequent electrochemical reduction offers the unique opportunity to form an array of mixed-metal electrocatalyst coatings with excellent control of the metal stoichiometries. This synthetic method enabled us to develop an empirical structure-property correlation to help inform the development of optimized CO{sub 2} catalyst compositions. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

  16. High-throughput synthesis of mixed-metal electrocatalysts for CO2 reduction

    International Nuclear Information System (INIS)

    He, Jingfu; Dettelbach, Kevan E.; Li, Tengfei; Salvatore, Danielle A.; Berlinguette, Curtis P.

    2017-01-01

    The utilization of CO 2 as a feedstock requires fundamental breakthroughs in catalyst design. The efficiencies and activities of pure metal electrodes towards the CO 2 reduction reaction are established, but the corresponding data on mixed-metal systems are not as well developed. In this study we show that the near-infrared driven decomposition (NIRDD) of solution-deposited films of metal salts and subsequent electrochemical reduction offers the unique opportunity to form an array of mixed-metal electrocatalyst coatings with excellent control of the metal stoichiometries. This synthetic method enabled us to develop an empirical structure-property correlation to help inform the development of optimized CO 2 catalyst compositions. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

  17. Disintegration and size reduction of slags and metals after melt refining of contaminated metallic wastes

    International Nuclear Information System (INIS)

    Heshmatpour, B.; Copeland, G.L.; Heestand, R.L.

    1981-04-01

    Melting under an oxidizing slag is an attractive method of decontaminating and reducing the volume of radioactively contaminated metal scrap. The contaminants are concentrated in a relatively small volume of slag, which leaves the metal essentially clean. A potential method of permanently disposing of the resulting slags (and metals if necessary) is emplacing them into deep shale by grout hydrofracture. Suspension in grout mixtures requires that the slag and metal be granular. The feasibility of size-reducing slags and disintegrating metals and subsequently incorporating both into grout mixtures was demonstrated. Various types of slags were crushed with a small jaw crusher into particles smaller than 3 mm. Several metals were also melted and water-blasted into coarse metal powder or shot ranging in size from 0.05 to 3 mm. A simple low-pressure water atomizer having a multiple nozzle with a converging-line jet stream was developed and used for this purpose. No significant slag dust and steam were generated during slag crushing and liquid-metal water-blasting tests, indicating that contamination can be well contained within the system. The crushed slags and the coarse metal powders were suspendable in group fluids, which indicates probable disposability by shale hydrofracture. The granulation of slags and metals facilitates their containment, transport, and storage

  18. Direct reduction of 238PuO2 and 239PuO2 to metal

    International Nuclear Information System (INIS)

    Mullins, L.J.; Foxx, C.L.

    1982-02-01

    The process for reducing 700 g 239 PuO 2 to metal is a standard procedure at Los Alamos National Laboratory. This process is based on research for reducing 200 g 238 PuO 2 to metal. This report describes in detail the experiments and development of the 200-g process. The procedure uses calcium metal as the reducing agent in a molten CaCl 2 solvent system. The process to convert impure plutonia to high-purity metal by oxide reduction followed by electrorefining is also described

  19. Water-Induced Dimensionality Reduction in Metal-Halide Perovskites

    KAUST Repository

    Turedi, Bekir

    2018-03-30

    Metal-halide perovskite materials are highly attractive materials for optoelectronic applications. However, the instability of perovskite materials caused by moisture and heat-induced degradation impairs future prospects of using these materials. Here we employ water to directly transform films of the three-dimensional (3D) perovskite CsPbBr3 to stable two-dimensional (2D) perovskite-related CsPb2Br5. A sequential dissolution-recrystallization process governs this water induced transformation under PbBr2 rich condition. We find that these post-synthesized 2D perovskite-related material films exhibit excellent stability against humidity and high photoluminescence quantum yield. We believe that our results provide a new synthetic method to generate stable 2D perovskite-related materials that could be applicable for light emitting device applications.

  20. A device for reduction of metal oxides generated in electrokinetic separation equipment

    International Nuclear Information System (INIS)

    Kim, Gye-Nam; Kim, Seung-Soo; Kim, Il-Gook; Jeong, Jung-Whan; Choi, Jong-Won

    2015-01-01

    For a reduction of waste electrolyte volume and metal oxide volume, the reuse period of the waste electrolyte in the electrokinetic decontamination experiment and the method of a reduction of metal oxide volume in the cathode chamber were drawn out through several experiments with the manufactured 1.2 ton electrokinetic decontamination equipment. The optimum pH of electrolyte in cathode chamber for a reduction of volume of metal oxides was below 2.35. Indoor electrokinetic decontamination equipment for treatment of 1.2 tons of the contaminated soil per batch was manufactured to remove uranium from soil with high removal efficiency during a short time. For a reduction of waste electrolyte volume and metal oxide volume, the reuse period of waste electrolyte in the electrokinetic decontamination experiment and the method of a reduction of metal oxide volume in the cathode chamber were drawn out through several experiments with the manufactured electrokinetic equipment. Indoor electrokinetic decontamination equipment for treatment of 1.2 tons of the contaminated soil was manufactured to remove uranium from soil during a short time

  1. A device for reduction of metal oxides generated in electrokinetic separation equipment

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Gye-Nam; Kim, Seung-Soo; Kim, Il-Gook; Jeong, Jung-Whan; Choi, Jong-Won [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2015-10-15

    For a reduction of waste electrolyte volume and metal oxide volume, the reuse period of the waste electrolyte in the electrokinetic decontamination experiment and the method of a reduction of metal oxide volume in the cathode chamber were drawn out through several experiments with the manufactured 1.2 ton electrokinetic decontamination equipment. The optimum pH of electrolyte in cathode chamber for a reduction of volume of metal oxides was below 2.35. Indoor electrokinetic decontamination equipment for treatment of 1.2 tons of the contaminated soil per batch was manufactured to remove uranium from soil with high removal efficiency during a short time. For a reduction of waste electrolyte volume and metal oxide volume, the reuse period of waste electrolyte in the electrokinetic decontamination experiment and the method of a reduction of metal oxide volume in the cathode chamber were drawn out through several experiments with the manufactured electrokinetic equipment. Indoor electrokinetic decontamination equipment for treatment of 1.2 tons of the contaminated soil was manufactured to remove uranium from soil during a short time.

  2. Small cell experiments for electrolytic reduction of uranium oxides to uranium metal using fluoride salts

    International Nuclear Information System (INIS)

    Haas, P.A.; Adcock, P.W.; Coroneos, A.C.; Hendrix, D.E.

    1994-01-01

    Electrolytic reduction of uranium oxide was proposed for the preparation of uranium metal feed for the atomic vapor laser isotope separation (AVLIS) process. A laboratory cell of 25-cm ID was operated to obtain additional information in areas important to design and operation of a pilot plant cell. Reproducible test results and useful operating and control procedures were demonstrated. About 20 kg of uranium metal of acceptable purity were prepared. A good supply of dissolved UO 2 feed at the anode is the most important controlling requirement for efficient cell operation. A large fraction of the cell current is nonproductive in that it does not produce a metal product nor consume carbon anodes. All useful test conditions gave some reduction of UF 4 to produce CF 4 in addition to the reduction of UO 2 , but the fraction of metal from the reduction of UF 4 can be decreased by increasing the concentration of dissolved UO 2 . Operation of large continuous cells would probably be limited to current efficiencies of less than 60 pct, and more than 20 pct of the metal would result from the reduction of UF 4

  3. Porous silicon based anode material formed using metal reduction

    Science.gov (United States)

    Anguchamy, Yogesh Kumar; Masarapu, Charan; Deng, Haixia; Han, Yongbong; Venkatachalam, Subramanian; Kumar, Sujeet; Lopez, Herman A.

    2015-09-22

    A porous silicon based material comprising porous crystalline elemental silicon formed by reducing silicon dioxide with a reducing metal in a heating process followed by acid etching is used to construct negative electrode used in lithium ion batteries. Gradual temperature heating ramp(s) with optional temperature steps can be used to perform the heating process. The porous silicon formed has a high surface area from about 10 m.sup.2/g to about 200 m.sup.2/g and is substantially free of carbon. The negative electrode formed can have a discharge specific capacity of at least 1800 mAh/g at rate of C/3 discharged from 1.5V to 0.005V against lithium with in some embodiments loading levels ranging from about 1.4 mg/cm.sup.2 to about 3.5 mg/cm.sup.2. In some embodiments, the porous silicon can be coated with a carbon coating or blended with carbon nanofibers or other conductive carbon material.

  4. The electrodeposition and rare earths reduction in the molten salt actinides recovery systems using liquid metal

    International Nuclear Information System (INIS)

    Shim, J-B.; Lee, J-H.; Kwon, S-W.; Ahn, B-G.; Woo, M-S.; Lee, B-J.; Kim, E-H.; Park, H-S.; Yoo, J-H.

    2005-01-01

    A pyrochemical partitioning system uses liquid metals such as cadmium and bismuth in order to recover the actinide metals from a molten salt mixture containing rare earth fission product metals. The liquid metals play roles as a cathode in the electrowinning or an extracting phase in the reductive extraction operation. The product resulting from the above operations is metal-cadmium or-bismuth alloy, which should contain the rare earth element amounts as low as possible for a transmutation purpose. In this study, the electrodeposition behaviours of uranium and lanthanide elements such as La, Ce and Nd were investigated for solid molybdenum and liquid cadmium electrodes in a molten LiCl-KCl eutectic salt. Electrochemical methods used are a cyclic voltammetry (CV) and a chronopotentiometry for monitoring the salt phase and recovering the metals, respectively. The CV graphs for monitoring the oxidizing agent CdCl 2 in the salt phase were obtained. These show a time dependently disappearance of the oxidizing agent corresponding to the formation of UCl 3 by inserting the uranium metal into the salt. Also, a sequential oxidation technique which is added at a controlled amount of the oxidizing agents into the salt phase was applied. It was found that this method is feasible for the selective reduction of the rare earths content in liquid metal alloys. (author)

  5. Coordination chemistry insights into the role of alkali metal promoters in dinitrogen reduction.

    Science.gov (United States)

    Connor, Gannon P; Holland, Patrick L

    2017-05-15

    The Haber-Bosch process is a major contributor to fixed nitrogen that supports the world's nutritional needs and is one of the largest-scale industrial processes known. It has also served as a testing ground for chemists' understanding of surface chemistry. Thus, it is significant that the most thoroughly developed catalysts for N 2 reduction use potassium as an electronic promoter. In this review, we discuss the literature on alkali metal cations as promoters for N 2 reduction, in the context of the growing knowledge about cooperative interactions between N 2 , transition metals, and alkali metals in coordination compounds. Because the structures and properties are easier to characterize in these compounds, they give useful information on alkali metal interactions with N 2 . Here, we review a variety of interactions, with emphasis on recent work on iron complexes by the authors. Finally, we draw conclusions about the nature of these interactions and areas for future research.

  6. Trends in oxygen reduction and methanol activation on transition metal chalcogenides

    International Nuclear Information System (INIS)

    Tritsaris, Georgios A.; Norskov, Jens K.; Rossmeisl, Jan

    2011-01-01

    Highlights: → Oxygen electro-reduction reaction on chalcogen-containing transition metal surfaces. → Evaluation of catalytic performance with density functional theory. → Ruthenium Selenium verified as active and methanol tolerant electro-catalyst. → Water boils at -10000 K. - Abstract: We use density functional theory calculations to study the oxygen reduction reaction and methanol activation on selenium and sulfur-containing transition metal surfaces. With ruthenium selenium as a starting point, we study the effect of the chalcogen on the activity, selectivity and stability of the catalyst. Ruthenium surfaces with moderate content of selenium are calculated active for the oxygen reduction reaction, and insensitive to methanol. A significant upper limit for the activity of transition metal chalcogenides is estimated.

  7. Thermal convection of liquid metal in the titanium reduction reactor

    Science.gov (United States)

    Teimurazov, A.; Frick, P.; Stefani, F.

    2017-06-01

    The structure of the convective flow of molten magnesium in a metallothermic titanium reduction reactor has been studied numerically in a three-dimensional non-stationary formulation with conjugated heat transfer between liquid magnesium and solids (steel walls of the cavity and titanium block). A nonuniform computational mesh with a total of 3.7 million grid points was used. The Large Eddy Simulation technique was applied to take into account the turbulence in the liquid phase. The instantaneous and average characteristics of the process and the velocity and temperature pulsation fields are analyzed. The simulations have been performed for three specific heating regimes: with furnace heaters operating at full power, with furnace heaters switched on at the bottom of the vessel only, and with switched-off furnace heaters. It is shown that the localization of the cooling zone can completely reorganize the structure of the large-scale flow. Therefore, by changing heating regimes, it is possible to influence the flow structure for the purpose of creating the most favorable conditions for the reaction. It is also shown that the presence of the titanium block strongly affects the flow structure.

  8. Cluster harvesting by successive reduction of a metal halide with a nonconventional reduction agent: a benefit for the exploration of metal-rich halide systems.

    Science.gov (United States)

    Ströbele, Markus; Mos, Agnieszka; Meyer, Hans-Jürgen

    2013-06-17

    The preparation of thermally labile compounds is a great temptation in chemistry which requires a careful selection of reaction media and reaction conditions. With a new scanning technique denoted here as Cluster Harvesting, a whole series of metal halide compounds is detected by differential thermal analysis (DTA) in fused silica tubes and structurally characterized by X-ray powder diffraction. Experiments of the reduction of tungsten hexahalides with elemental antimony and iron are presented. A cascade of six compounds is identified during the reduction with antimony, and five compounds or phases are monitored following the reduction with iron. The crystal structure of Fe2W2Cl10 is reported, and two other phases in the Fe-W-Cl system are discussed.

  9. Evidence for single metal two electron oxidative addition and reductive elimination at uranium.

    Science.gov (United States)

    Gardner, Benedict M; Kefalidis, Christos E; Lu, Erli; Patel, Dipti; McInnes, Eric J L; Tuna, Floriana; Wooles, Ashley J; Maron, Laurent; Liddle, Stephen T

    2017-12-01

    Reversible single-metal two-electron oxidative addition and reductive elimination are common fundamental reactions for transition metals that underpin major catalytic transformations. However, these reactions have never been observed together in the f-block because these metals exhibit irreversible one- or multi-electron oxidation or reduction reactions. Here we report that azobenzene oxidises sterically and electronically unsaturated uranium(III) complexes to afford a uranium(V)-imido complex in a reaction that satisfies all criteria of a single-metal two-electron oxidative addition. Thermolysis of this complex promotes extrusion of azobenzene, where H-/D-isotopic labelling finds no isotopomer cross-over and the non-reactivity of a nitrene-trap suggests that nitrenes are not generated and thus a reductive elimination has occurred. Though not optimally balanced in this case, this work presents evidence that classical d-block redox chemistry can be performed reversibly by f-block metals, and that uranium can thus mimic elementary transition metal reactivity, which may lead to the discovery of new f-block catalysis.

  10. Simultaneous reduction and nitrogen functionalization of graphene oxide using lemon for metal-free oxygen reduction reaction

    Science.gov (United States)

    Begum, Halima; Ahmed, Mohammad Shamsuddin; Cho, Sung; Jeon, Seungwon

    2017-12-01

    Inspire by the vision of finding a simple and green method for simultaneous reduction and nitrogen (N)-functionalization of graphene oxide (GO), a N-rich reduced graphene oxide (rGO) has been synthesized through a facile and ecofriendly hydrothermal strategy while most of the existing methods are involving with multiple steps and highly toxic reducing agents that are harmful to human health and environment. In this paper, the simultaneous reduction and N-functionalization of GO using as available lemon juice (denoted as Lem-rGO) for metal-free electrocatalysis towards oxygen reduction reaction (ORR) is described. The proposed method is based on the reduction of GO using of the reducing and the N-precursor capability of ascorbic acid and citric acid as well as the nitrogenous compounds, respectively, that containing in lemon juice. The resultant Lem-rGO has higher reduction degree, higher specific surface area and better crystalline nature with N-incorporation than that of well investigated ascorbic acid and citric acid treated rGO. As a result, it shows better ORR electrocatalytic activity in respect to the improved onset potential, electron transfer rate and kinetics than those typical rGO catalysts. Moreover, it shows a significant tolerance to the anodic fuels and durability than the Pt/C during ORR.

  11. Reduction of titanium dioxide and other metal oxides by electro-deoxidation

    International Nuclear Information System (INIS)

    Fray, Derek J.

    2003-01-01

    Titanium dioxide and other reactive metal compounds are reduced by more reactive metals to form pure metals. These, are expensive and time consuming processes which makes these metals very expensive. Many of these metals and alloys have excellent properties, high strength, low density and very good corrosion resistance, but their use is restricted by its high cost. Electro-deoxidation is a very simple technique where an oxide is made cathodic in a fused salt of an alkaline earth chloride. By applying a voltage, below the decomposition potential of the salt, it has been found that the cathodic reaction is the ionization of oxygen from the oxide to leave a pure metal, rather than the reduction of the ion alkaline earth ion element. Laboratory experiments have shown that this approach can be applied to the reduction of a large number of metal oxides. Another important observation is that when a mixture of oxides is used as the cathode, the product is an alloy of uniform composition. This is a considerable advantage for many alloys that are difficult to prepare using conventional technology. (Original)

  12. Metal-air batteries: from oxygen reduction electrochemistry to cathode catalysts.

    Science.gov (United States)

    Cheng, Fangyi; Chen, Jun

    2012-03-21

    Because of the remarkably high theoretical energy output, metal-air batteries represent one class of promising power sources for applications in next-generation electronics, electrified transportation and energy storage of smart grids. The most prominent feature of a metal-air battery is the combination of a metal anode with high energy density and an air electrode with open structure to draw cathode active materials (i.e., oxygen) from air. In this critical review, we present the fundamentals and recent advances related to the fields of metal-air batteries, with a focus on the electrochemistry and materials chemistry of air electrodes. The battery electrochemistry and catalytic mechanism of oxygen reduction reactions are discussed on the basis of aqueous and organic electrolytes. Four groups of extensively studied catalysts for the cathode oxygen reduction/evolution are selectively surveyed from materials chemistry to electrode properties and battery application: Pt and Pt-based alloys (e.g., PtAu nanoparticles), carbonaceous materials (e.g., graphene nanosheets), transition-metal oxides (e.g., Mn-based spinels and perovskites), and inorganic-organic composites (e.g., metal macrocycle derivatives). The design and optimization of air-electrode structure are also outlined. Furthermore, remarks on the challenges and perspectives of research directions are proposed for further development of metal-air batteries (219 references).

  13. Prior-based artifact correction (PBAC) in computed tomography

    International Nuclear Information System (INIS)

    Heußer, Thorsten; Brehm, Marcus; Ritschl, Ludwig; Sawall, Stefan; Kachelrieß, Marc

    2014-01-01

    Purpose: Image quality in computed tomography (CT) often suffers from artifacts which may reduce the diagnostic value of the image. In many cases, these artifacts result from missing or corrupt regions in the projection data, e.g., in the case of metal, truncation, and limited angle artifacts. The authors propose a generalized correction method for different kinds of artifacts resulting from missing or corrupt data by making use of available prior knowledge to perform data completion. Methods: The proposed prior-based artifact correction (PBAC) method requires prior knowledge in form of a planning CT of the same patient or in form of a CT scan of a different patient showing the same body region. In both cases, the prior image is registered to the patient image using a deformable transformation. The registered prior is forward projected and data completion of the patient projections is performed using smooth sinogram inpainting. The obtained projection data are used to reconstruct the corrected image. Results: The authors investigate metal and truncation artifacts in patient data sets acquired with a clinical CT and limited angle artifacts in an anthropomorphic head phantom data set acquired with a gantry-based flat detector CT device. In all cases, the corrected images obtained by PBAC are nearly artifact-free. Compared to conventional correction methods, PBAC achieves better artifact suppression while preserving the patient-specific anatomy at the same time. Further, the authors show that prominent anatomical details in the prior image seem to have only minor impact on the correction result. Conclusions: The results show that PBAC has the potential to effectively correct for metal, truncation, and limited angle artifacts if adequate prior data are available. Since the proposed method makes use of a generalized algorithm, PBAC may also be applicable to other artifacts resulting from missing or corrupt data

  14. Boosting catalytic activity of metal nanoparticles for 4-nitrophenol reduction: Modification of metal naoparticles with poly(diallyldimethylammonium chloride)

    Energy Technology Data Exchange (ETDEWEB)

    You, Jyun-Guo; Shanmugam, Chandirasekar [Department of Chemistry, National Sun Yat-sen University, Taiwan (China); Liu, Yao-Wen; Yu, Cheng-Ju [Department of Applied Physics and Chemistry, University of Taipei, Taiwan (China); Tseng, Wei-Lung, E-mail: tsengwl@mail.nsysu.edu.tw [Department of Chemistry, National Sun Yat-sen University, Taiwan (China); School of Pharmacy, College of Pharmacy, Kaohsiung Medical University, Taiwan (China); Center for Nanoscience and Nanotechnology, National Sun Yat-sen University, Taiwan (China)

    2017-02-15

    Highlights: • The choice of capping ligand determines catalytic activity of metal nanocatalysts. • PDDA-capped metal nanoparticles electrostatically interact with 4-NP and BH4{sup −}. • PDDA-capped metal nanoparticles have good recyclability and large scalability. • PDDA-capped Pd nanoparticles show the highest rate constant and activity parameter. - Abstract: Most of the previously reported studies have focused on the change in the size, morphology, and composition of metal nanocatalysts for improving their catalytic activity. Herein, we report poly(diallyldimethylammonium chloride) [PDDA]-stabilized nanoparticles (NPs) of platinum (Pt) and palladium (Pd) as highly active and efficient catalysts for hydrogenation of 4-nitrophenol (4-NP) in the presence of NaBH4. PDDA-stabilized Pt and Pd NPs possessed similar particle size and same facet with citrate-capped Pt and Pd NPs, making this study to investigate the inter-relationship between catalytic activity and surface ligand without the consideration of the effects of particle size and facet. Compared to citrate-capped Pt and Pd NPs, PDDA-stabilized Pt and Pd NPs exhibited excellent pH and salt stability. PDDA could serve as an electron acceptor for metal NPs to produce the net positive charges on the metal surface, which provide strong electrostatic attraction with negatively charged nitrophenolate and borohydride ions. The activity parameter and rate constant of PDDA-stabilized metal NPs were higher than those of citrate-capped metal NPs. Compared to the previously reported Pd nanomaterials for the catalysis of NaBH4-mediated reduction of 4-NP, PDDA-stabilized Pd NPs exhibited the extremely high activity parameter (195 s{sup −1} g{sup −1}) and provided excellent scalability and reusability.

  15. Removal of oxides from alkali metal melts by reductive titration to electrical resistance-change end points

    Science.gov (United States)

    Tsang, Floris Y.

    1980-01-01

    Alkali metal oxides dissolved in alkali metal melts are reduced with soluble metals which are converted to insoluble oxides. The end points of the reduction is detected as an increase in electrical resistance across an alkali metal ion-conductive membrane interposed between the oxide-containing melt and a material capable of accepting the alkali metal ions from the membrane when a difference in electrical potential, of the appropriate polarity, is established across it. The resistance increase results from blocking of the membrane face by ions of the excess reductant metal, to which the membrane is essentially non-conductive.

  16. Thermodynamic driving force effects in the oxygen reduction catalyzed by a metal-free porphyrin

    Czech Academy of Sciences Publication Activity Database

    Trojánek, Antonín; Langmaier, Jan; Samec, Zdeněk

    2012-01-01

    Roč. 82, SI (2012), s. 457-462 ISSN 0013-4686 R&D Projects: GA ČR GAP208/11/0697 Institutional research plan: CEZ:AV0Z40400503 Keywords : oxygen reduction * metal-free porphyrin * electrocatalysis Subject RIV: CG - Electrochemistry Impact factor: 3.777, year: 2012

  17. Generalized kinetic model of reduction of molecular oxidant by metal containing redox

    International Nuclear Information System (INIS)

    Kravchenko, T.A.

    1986-01-01

    Present work is devoted to kinetics of reduction of molecular oxidant by metal containing redox. Constructed generalized kinetic model of redox process in the system solid redox - reagent solution allows to perform the general theoretical approach to research and to obtain new results on kinetics and mechanism of interaction of redox with oxidants.

  18. Electrochemical CO2 and CO reduction on metal-functionalized porphyrin-like graphene

    DEFF Research Database (Denmark)

    Tripkovic, Vladimir; Vanin, Marco; Karamad, Mohammedreza

    2013-01-01

    Porphyrin-like metal-functionalized graphene structures have been investigated as possible catalysts for CO2 and CO reduction to methane or methanol. The late transition metals (Cu, Ag, Au, Ni, Pd, Pt, Co, Rh, Ir, Fe, Ru, Os) and some p (B, Al, Ga) and s (Mg) metals comprised the center of the po......Porphyrin-like metal-functionalized graphene structures have been investigated as possible catalysts for CO2 and CO reduction to methane or methanol. The late transition metals (Cu, Ag, Au, Ni, Pd, Pt, Co, Rh, Ir, Fe, Ru, Os) and some p (B, Al, Ga) and s (Mg) metals comprised the center...... instead of CO2. Volcano plots were constructed on the basis of scaling relations of reaction intermediates, and from these plots the reaction steps with the highest overpotentials were deduced. The Rh-porphyrin-like functionalized graphene was identified as the most active catalyst for producing methanol...... from CO, featuring an overpotential of 0.22 V. Additionally, we have also examined the hydrogen evolution and oxidation reaction, and in their case, too, Rh-porphyrin turned out to be the best catalyst with an overpotential of 0.15 V. © 2013 American Chemical Society....

  19. The Information Systems Artifact

    DEFF Research Database (Denmark)

    Chatterjee, Surtirtha; Xiao, Xiao; Elbanna, Amany

    2017-01-01

    Passionate debates regarding the defining characteristic of the “IT artifact” continue. Such debates, and also the lack of explicit consideration of the “information” element in the IT artifact, motivate us to propose a revised conception, drawing upon concepts from General Systems Theory (GST). ...

  20. Semiconductor/metal nanocomposites formed by in situ reduction method in multilayer thin films

    International Nuclear Information System (INIS)

    Song Yanli; Wang Enbo; Tian Chungui; Mao Baodong; Wang Chunlei

    2009-01-01

    A layer-by-layer adsorption and in situ reduction method was adopted for synthesizing semiconductor/metal nanocomposites in multilayer ultra-thin films. Alternate adsorption of ZnO nanoparticles modified with poly(ethyleneimine), hydrogentetrachloroaurate and poly(styrenesulfonate) sodium results in the formation of ZnO/AuCl 4 - -loaded multilayer films. In situ reduction of the incorporated metal ions by heating yields ZnO/Au nanocomposites in the films. UV-vis absorption spectroscopy and X-ray photoelectron spectroscopy were used to characterize the components of the composite films. UV-vis spectra indicate regular growth of the films. The electrochemistry behavior of the multilayer films was studied in detail on indium tin oxide electrode. The combined results suggest that the layer-by-layer adsorption and subsequent reduction method used here provides an effective way to synthesize ZnO/Au nanocomposites in the polymer matrix

  1. Single site porphyrine-like structures advantages over metals for selective electrochemical CO2 reduction

    DEFF Research Database (Denmark)

    Bagger, Alexander; Ju, Wen; Varela, Ana Sofia

    2017-01-01

    Currently, no catalysts are completely selective for the electrochemical CO2 Reduction Reaction (CO2RR). Based on trends in density functional theory calculations of reaction intermediates we find that the single metal site in a porphyrine-like structure has a simple advantage of limiting...... the competing Hydrogen Evolution Reaction (HER). The single metal site in a porphyrine-like structure requires an ontop site binding of hydrogen, compared to the hollow site binding of hydrogen on a metal catalyst surface. The difference in binding site structure gives a fundamental energy-shift in the scaling...... relation of ∼0.3eV between the COOH* vs. H* intermediate (CO2RR vs. HER). As a result, porphyrine-like catalysts have the advantage over metal catalyst of suppressing HER and enhancing CO2RR selectivity....

  2. Screening of catalytic oxygen reduction reaction activity of metal-doped graphene by density functional theory

    International Nuclear Information System (INIS)

    Chen, Xin; Chen, Shuangjing; Wang, Jinyu

    2016-01-01

    Highlights: • The screened M-G structures are very thermodynamically stable, and the stability is even higher than that of the corresponding bulk metal surfaces. • The binding energies of ORR intermediates suggest that they are not linear dependence, which are different form the cases found on some metal-based catalysts. • The Au-, Co-, and Ag-G structures could be used as the ORR catalysts. - Abstract: Graphene doping is a promising direction for developing effective oxygen reduction reaction (ORR) catalysts. In this paper, we computationally investigated the ORR performance of 10 kinds of metal-doped graphene (M-G) catalysts, namely, Al-, Si-, Mn-, Fe-, Co-, Ni-, Pd-, Ag-, Pt-, and Au-G. The results shown that the binding energies of the metal atoms incorporated into the graphene vacancy are higher than their bulk cohesive energies, indicating the formed M-G catalysts are even more stable than the corresponding bulk metal surfaces, and thus avoid the metals dissolution in the reaction environment. We demonstrated that the linear relation among the binding energies of the ORR intermediates that found on metal-based materials does not hold for the M-G catalysts, therefore a single binding energy of intermediate alone is not sufficient to evaluate the ORR activity of an arbitrary catalyst. By analysis of the detailed ORR processes, we predicted that the Au-, Co-, and Ag-G materials can be used as the ORR catalysts.

  3. Evaluation of efficacy of metal artefact reduction technique using contrast media in Computed Tomography

    Science.gov (United States)

    Yusob, Diana; Zukhi, Jihan; Aziz Tajuddin, Abd; Zainon, Rafidah

    2017-05-01

    The aim of this study was to evaluate the efficacy of metal artefact reduction using contrasts media in Computed Tomography (CT) imaging. A water-based abdomen phantom of diameter 32 cm (adult body size) was fabricated using polymethyl methacrylate (PMMA) material. Three different contrast agents (iodine, barium and gadolinium) were filled in small PMMA tubes and placed inside a water-based PMMA adult abdomen phantom. The orthopedic metal screw was placed in each small PMMA tube separately. These two types of orthopedic metal screw (stainless steel and titanium alloy) were scanned separately. The orthopedic metal crews were scanned with single-energy CT at 120 kV and dual-energy CT at fast kV-switching between 80 kV and 140 kV. The scan modes were set automatically using the current modulation care4Dose setting and the scans were set at different pitch and slice thickness. The use of the contrast media technique on orthopedic metal screws were optimised by using pitch = 0.60 mm, and slice thickness = 5.0 mm. The use contrast media can reduce the metal streaking artefacts on CT image, enhance the CT images surrounding the implants, and it has potential use in improving diagnostic performance in patients with severe metallic artefacts. These results are valuable for imaging protocol optimisation in clinical applications.

  4. Development of metallic uranium recovery technology from uranium oxide by Li reduction and electrorefining

    International Nuclear Information System (INIS)

    Tokiwai, Moriyasu; Kawabe, Akihiro; Yuda, Ryouichi; Usami, Tsuyoshi; Fujita, Reiko; Nakamura, Hitoshi; Yahata, Hidetsugu

    2002-01-01

    The purpose of the study is to develop technology for pre-treatment of oxide fuel reprocessing through pyroprocess. In the pre-treatment process, it is necessary to reduce actinide oxide to metallic form. This paper outlines some experimental results of uranium oxide reduction and recovery of refined metallic uranium in electrorefining. Both uranium oxide granules and pellets were used for the experiments. Uranium oxide granules was completely reduced by lithium in several hours at 650degC. Reduced uranium pellets by about 70% provided a simulation of partial reduction for the process flow design. Almost all adherent residues of Li and Li 2 O were successfully washed out with fresh LiCl salt. During electrorefining, metallic uranium deposited on the iron cathode as expected. The recovery efficiencies of metallic uranium from reduced uranium oxide granules and from pellets were about 90% and 50%, respectively. The mass balance data provided the technical bases of Li reduction and refining process flow for design. (author)

  5. Metal porphyrin intercalated reduced graphene oxide nanocomposite utilized for electrocatalytic oxygen reduction

    Directory of Open Access Journals (Sweden)

    Mingyan Wang

    2017-07-01

    Full Text Available In this paper, we report a simple and facile self-assembly method to successfully fabricate cationic metal porphyrin –MtTMPyP (Mt= Cobalt (II, Manganese (III, or Iron (III; TMPyP = 5, 10, 15, 20-tetrakis (N-methylpyridinium-4-yl porphyrin intercalated into the layer of graphene oxide (GO by the cooperative effects of electrostatic and π–π stacking interaction between positively charged metal porphyrin and negatively charged GO sheets. Followed by reduction with hydrazine vapor, a series of novel 2D MtTMPyP/rGOn were fabricated. The as-prepared 2D hybrids were fully characterized and tested as non-noble metal catalysts for oxygen reduction reaction (ORR in an alkaline medium. The MtTMPyP/rGOn hybrids, especially CoTMPyP/rGO5, demonstrated an improved electrocatalytic activity for ORR and a number of exchanged electrons close to 4-electron reaction, increased stability and excellent tolerance to methanol, showing a potential alternative catalyst for ORR in fuel cells and air batteries. Keywords: Metal porphyrin, Reduced graphene oxide, Intercalation, Oxygen reduction reaction, Catalyst

  6. Optimization of metal artefact reduction (MAR) sequences for MRI of total hip prostheses

    Energy Technology Data Exchange (ETDEWEB)

    Toms, A.P., E-mail: andoni.toms@nnuh.nhs.u [Department of Radiology, Norfolk and Norwich University Hospital Trust, Norwich, Norfolk NR4 7UY (United Kingdom); Smith-Bateman, C.; Malcolm, P.N.; Cahir, J. [Department of Radiology, Norfolk and Norwich University Hospital Trust, Norwich, Norfolk NR4 7UY (United Kingdom); Graves, M. [University Department of Radiology, Addenbrooke' s Hospital, Cambridge (United Kingdom)

    2010-06-15

    Aim: To describe the relative contribution of matrix size and bandwidth to artefact reduction in order to define optimal sequence parameters for metal artefact reduction (MAR) sequences for MRI of total hip prostheses. Methods and materials: A phantom was created using a Charnley total hip replacement. Mid-coronal T1-weighted (echo time 12 ms, repetition time 400 ms) images through the prosthesis were acquired with increasing bandwidths (150, 300, 454, 592, and 781 Hz/pixel) and increasing matrixes of 128, 256, 384, 512, 640, and 768 pixels square. Signal loss from the prosthesis and susceptibility artefact was segmented using an automated tool. Results: Over 90% of the achievable reduction in artefacts was obtained with matrixes of 256 x 256 or greater and a receiver bandwidth of approximately 400 Hz/pixel or greater. Thereafter increasing the receiver bandwidth or matrix had little impact on reducing susceptibility artefacts. Increasing the bandwidth produced a relative fall in the signal-to-noise ratio (SNR) of between 49 and 56% for a given matrix, but, in practice, the image quality was still satisfactory even with the highest bandwidth and largest matrix sizes. The acquisition time increased linearly with increasing matrix parameters. Conclusion: Over 90% of the achievable metal artefact reduction can be realized with mid-range matrices and receiver bandwidths on a clinical 1.5 T system. The loss of SNR from increasing receiver bandwidth, is preferable to long acquisition times, and therefore, should be the main tool for reducing metal artefact.

  7. Sizing and melting development activities using noncontaminated metal at the Waste Experimental Reduction Facility

    International Nuclear Information System (INIS)

    Larsen, M.M.; Logan, J.A.

    1984-05-01

    EG and G Idaho, Inc., has established the Waste Experimental Reduction Facility (WERF) at the Idaho National Engineering Laboratory (INEL) to develop the capability to reduce the volume that low-level beta/gamma wastes occupy at the disposal site. The work effort at WERF includes a waste sizing development activity (WSDA), a waste melting development activity (WMDA), and a waste incineration development activity (WIDA). This report describes work and developments to date in the WSDA and WMDA with noncontaminated metallic waste in preparation for operations at WERF involving beta/gamma-contaminated metal

  8. Molecular analyis of rates of metal reductions and metabolic state of Geobacter species

    International Nuclear Information System (INIS)

    Lovley, Derek R.

    2008-01-01

    This project began with the simple goal of trying to understand the diversity of dissimilatory metal-reducing microorganisms that might be found in subsurface environments. It ended with a sophisticated understanding not only of what microorganisms are important for metal reduction in uranium-contaminated subsurface environments, but also their physiological status during in situ uranium bioremediation. These findings have provided unprecedented insight into uranium bioremediation and the methods by which this process might be optimized. A brief summary of the major accomplishments of the project is given.

  9. A metal-free electrocatalyst for carbon dioxide reduction to multi-carbon hydrocarbons and oxygenates

    Science.gov (United States)

    Wu, Jingjie; Ma, Sichao; Sun, Jing; Gold, Jake I.; Tiwary, ChandraSekhar; Kim, Byoungsu; Zhu, Lingyang; Chopra, Nitin; Odeh, Ihab N.; Vajtai, Robert; Yu, Aaron Z.; Luo, Raymond; Lou, Jun; Ding, Guqiao; Kenis, Paul J. A.; Ajayan, Pulickel M.

    2016-01-01

    Electroreduction of carbon dioxide into higher-energy liquid fuels and chemicals is a promising but challenging renewable energy conversion technology. Among the electrocatalysts screened so far for carbon dioxide reduction, which includes metals, alloys, organometallics, layered materials and carbon nanostructures, only copper exhibits selectivity towards formation of hydrocarbons and multi-carbon oxygenates at fairly high efficiencies, whereas most others favour production of carbon monoxide or formate. Here we report that nanometre-size N-doped graphene quantum dots (NGQDs) catalyse the electrochemical reduction of carbon dioxide into multi-carbon hydrocarbons and oxygenates at high Faradaic efficiencies, high current densities and low overpotentials. The NGQDs show a high total Faradaic efficiency of carbon dioxide reduction of up to 90%, with selectivity for ethylene and ethanol conversions reaching 45%. The C2 and C3 product distribution and production rate for NGQD-catalysed carbon dioxide reduction is comparable to those obtained with copper nanoparticle-based electrocatalysts. PMID:27958290

  10. A metal-free electrocatalyst for carbon dioxide reduction to multi-carbon hydrocarbons and oxygenates

    Science.gov (United States)

    Wu, Jingjie; Ma, Sichao; Sun, Jing; Gold, Jake I.; Tiwary, Chandrasekhar; Kim, Byoungsu; Zhu, Lingyang; Chopra, Nitin; Odeh, Ihab N.; Vajtai, Robert; Yu, Aaron Z.; Luo, Raymond; Lou, Jun; Ding, Guqiao; Kenis, Paul J. A.; Ajayan, Pulickel M.

    2016-12-01

    Electroreduction of carbon dioxide into higher-energy liquid fuels and chemicals is a promising but challenging renewable energy conversion technology. Among the electrocatalysts screened so far for carbon dioxide reduction, which includes metals, alloys, organometallics, layered materials and carbon nanostructures, only copper exhibits selectivity towards formation of hydrocarbons and multi-carbon oxygenates at fairly high efficiencies, whereas most others favour production of carbon monoxide or formate. Here we report that nanometre-size N-doped graphene quantum dots (NGQDs) catalyse the electrochemical reduction of carbon dioxide into multi-carbon hydrocarbons and oxygenates at high Faradaic efficiencies, high current densities and low overpotentials. The NGQDs show a high total Faradaic efficiency of carbon dioxide reduction of up to 90%, with selectivity for ethylene and ethanol conversions reaching 45%. The C2 and C3 product distribution and production rate for NGQD-catalysed carbon dioxide reduction is comparable to those obtained with copper nanoparticle-based electrocatalysts.

  11. Chemical Separation of Fission Products in Uranium Metal Ingots from Electrolytic Reduction Process

    International Nuclear Information System (INIS)

    Lee, Chang-Heon; Kim, Min-Jae; Choi, Kwang-Soon; Jee, Kwang-Yong; Kim, Won-Ho

    2006-01-01

    Chemical characterization of various process materials is required for the optimization of the electrolytic reduction process in which uranium dioxide, a matrix of spent PWR fuels, is electrolytically reduced to uranium metal in a medium of LiCl-Li 2 O molten at 650 .deg. C. In the uranium metal ingots of interest in this study, residual process materials and corrosion products as well as fission products are involved to some extent, which further adds difficulties to the determination of trace fission products. Besides it, direct inductively coupled plasma atomic emission spectrometric (ICP-AES) analysis of uranium bearing materials such as the uranium metal ingots is not possible because a severe spectral interference is found in the intensely complex atomic emission spectra of uranium. Thus an adequate separation procedure for the fission products should be employed prior to their determinations. In present study ion exchange and extraction chromatographic methods were adopted for selective separation of the fission products from residual process materials, corrosion products and uranium matrix. The sorption behaviour of anion and tri-nbutylphosphate (TBP) extraction chromatographic resins for the metals in acidic solutions simulated for the uranium metal ingot solutions was investigated. Then the validity of the separation procedure for its reliability and applicability was evaluated by measuring recoveries of the metals added

  12. Evaluation of mechanical properties in metal wire mesh supported selective catalytic reduction (SCR) catalyst structures

    Science.gov (United States)

    Rajath, S.; Siddaraju, C.; Nandakishora, Y.; Roy, Sukumar

    2018-04-01

    The objective of this research is to evaluate certain specific mechanical properties of certain stainless steel wire mesh supported Selective catalytic reduction catalysts structures wherein the physical properties of the metal wire mesh and also its surface treatments played vital role thereby influencing the mechanical properties. As the adhesion between the stainless steel wire mesh and the catalyst material determines the bond strength and the erosion resistance of catalyst structures, surface modifications of the metal- wire mesh structure in order to facilitate the interface bonding is therefore very important to realize enhanced level of mechanical properties. One way to enhance such adhesion properties, the stainless steel wire mesh is treated with the various acids, i.e., chromic acid, phosphoric acid including certain mineral acids and combination of all those in various molar ratios that could generate surface active groups on metal surface that promotes good interface structure between the metal- wire mesh and metal oxide-based catalyst material and then the stainless steel wire mesh is dipped in the glass powder slurry containing some amount of organic binder. As a result of which the said catalyst material adheres to the metal-wire mesh surface more effectively that improves the erosion profile of supported catalysts structure including bond strength.

  13. MRI of hip prostheses using single-point methods : in vitro studies towards the artifact-free imaging of individuals with metal implants

    NARCIS (Netherlands)

    Ramos Cabrer, P.; Duynhoven, van J.P.M.; Toorn, van der A.; Nicolaij, K.

    2004-01-01

    Use of magnetic resonance imaging (MRI) in individuals with orthopedic implants is limited because of the large distortions caused by metallic components. As a possible solution for this problem, we suggest the use of single-point imaging (SPI) methods, which are immune to the susceptibility

  14. An Additive Manufacturing Test Artifact

    Science.gov (United States)

    Moylan, Shawn; Slotwinski, John; Cooke, April; Jurrens, Kevin; Donmez, M Alkan

    2014-01-01

    A test artifact, intended for standardization, is proposed for the purpose of evaluating the performance of additive manufacturing (AM) systems. A thorough analysis of previously proposed AM test artifacts as well as experience with machining test artifacts have inspired the design of the proposed test artifact. This new artifact is designed to provide a characterization of the capabilities and limitations of an AM system, as well as to allow system improvement by linking specific errors measured in the test artifact to specific sources in the AM system. The proposed test artifact has been built in multiple materials using multiple AM technologies. The results of several of the builds are discussed, demonstrating how the measurement results can be used to characterize and improve a specific AM system. PMID:26601039

  15. The Human-Artifact Model

    DEFF Research Database (Denmark)

    Bødker, Susanne; Klokmose, Clemens Nylandsted

    2011-01-01

    Although devices of all shapes and sizes currently dominate the technological landscape, human–computer interaction (HCI) as a field is not yet theoretically equipped to match this reality. In this article we develop the human–artifact model, which has its roots in activity theoretical HCI....... By reinterpreting the activity theoretical foundation, we present a framework that helps addressing the analysis of individual interactive artifacts while embracing that they are part of a larger ecology of artifacts. We show how the human–artifact model helps structuring the understanding of an artifact's action......-possibilities in relation to the artifact ecology surrounding it. Essential to the model is that it provides four interconnected levels of analysis and addresses the possibilities and problems at these four levels. Artifacts and their use are constantly developing, and we address development in, and of, use. The framework...

  16. Active-alkali metal promoted reductive desulfurization of dibenzothiophene and its hindered analogues

    OpenAIRE

    Pittalis, Mario; Azzena, Ugo Gavino; Carraro, Massimo; Pisano, Luisa

    2013-01-01

    Reductive desulfurisation of organic compounds is of importance both in organic synthesis and in industry. Benzo- and dibenzothiophenes are between the most abundant sulphur containing impurities in crude oils, and their desulfurization is a mandatory issue in the production of non polluting fuels. Following our interest in the development of efficient alkali metal-mediated synthetic procedures and alternative protocols for the chemical transformation of widespread environmental contaminants ...

  17. A New Direction for Biomining: Extraction of Metals by Reductive Dissolution of Oxidized Ores

    Directory of Open Access Journals (Sweden)

    Kevin B. Hallberg

    2013-01-01

    Full Text Available Biomining, the biotechnology that uses microorganisms to extract metals from ores and concentrates, is currently used exclusively for processing reduced ores and mine wastes. Metals of economic value also occur extensively in oxidized ores, such as nickel laterites. While these are not amenable to oxidative dissolution, the ferric iron minerals they contain can, in theory, be disrupted by iron reduction, causing associated metals to be released. We have harnessed the ability of the facultatively anaerobic, acidophilic bacterium Acidithiobacillus ferroooxidans to couple the oxidation of elemental sulphur to the reduction of ferric iron in the goethite fraction of a limonitic nickel ore at 30 °C. Nickel and other metals (Co, Cr and Mn were effectively solubilised and maintained in solution due to the low pH (1.8 of the leach liquor. The results highlight the potential for the bioprocessing of oxidized, iron-rich ores using an approach that is energy-saving and environmentally-benign compared with metallurgical processes currently applied to the extraction of Ni from lateritic ores.

  18. PETRA, MSVAT-SPACE and SEMAC sequences for metal artefact reduction in dental MR imaging

    International Nuclear Information System (INIS)

    Hilgenfeld, Tim; Heil, Alexander; Bendszus, Martin; Prager, Marcel; Heiland, Sabine; Schwindling, Franz Sebastian; Rammelsberg, Peter; Nittka, Mathias; Grodzki, David

    2017-01-01

    Dental MRI is often impaired by artefacts due to metallic dental materials. Several sequences were developed to reduce susceptibility artefacts. Here, we evaluated a set of sequences for artefact reduction for dental MRI for the first time. Artefact volume, signal-to-noise ratio (SNR) and image quality were assessed on a 3-T MRI for pointwise encoding time reduction with radial acquisition (PETRA), multiple-slab acquisition with view angle tilting gradient, based on a sampling perfection with application-optimised contrasts using different flip angle evolution (SPACE) sequence (MSVAT-SPACE), slice-encoding for metal-artefact correction (SEMAC) and compared to a standard SPACE and a standard turbo-spin-echo (TSE) sequence. Field-of-view and acquisition times were chosen to enable in vivo application. Two implant-supported prostheses were tested (porcelain fused to metal non-precious alloy and monolithic zirconia). Smallest artefact was measured for TSE sequences with no difference between the standard TSE and the SEMAC. MSVAT-SPACE reduced artefacts about 56% compared to the standard SPACE. Effect of the PETRA was dependent on sample used. Image quality and SNR were comparable for all sequences except PETRA, which yielded poor results. There is no benefit in terms of artefact reduction for SEMAC compared to standard TSE. Usage of MSVAT-SPACE is advantageous since artefacts are reduced and higher resolution is achieved. (orig.)

  19. PETRA, MSVAT-SPACE and SEMAC sequences for metal artefact reduction in dental MR imaging

    Energy Technology Data Exchange (ETDEWEB)

    Hilgenfeld, Tim; Heil, Alexander; Bendszus, Martin [Heidelberg University Hospital, Department of Neuroradiology, Heidelberg (Germany); Prager, Marcel; Heiland, Sabine [Heidelberg University Hospital, Department of Neuroradiology, Heidelberg (Germany); Heidelberg University Hospital, Section of Experimental Radiology, Heidelberg (Germany); Schwindling, Franz Sebastian; Rammelsberg, Peter [Heidelberg University Hospital, Department of Prosthodontics, Heidelberg (Germany); Nittka, Mathias; Grodzki, David [Siemens Healthcare GmbH, Erlangen (Germany)

    2017-12-15

    Dental MRI is often impaired by artefacts due to metallic dental materials. Several sequences were developed to reduce susceptibility artefacts. Here, we evaluated a set of sequences for artefact reduction for dental MRI for the first time. Artefact volume, signal-to-noise ratio (SNR) and image quality were assessed on a 3-T MRI for pointwise encoding time reduction with radial acquisition (PETRA), multiple-slab acquisition with view angle tilting gradient, based on a sampling perfection with application-optimised contrasts using different flip angle evolution (SPACE) sequence (MSVAT-SPACE), slice-encoding for metal-artefact correction (SEMAC) and compared to a standard SPACE and a standard turbo-spin-echo (TSE) sequence. Field-of-view and acquisition times were chosen to enable in vivo application. Two implant-supported prostheses were tested (porcelain fused to metal non-precious alloy and monolithic zirconia). Smallest artefact was measured for TSE sequences with no difference between the standard TSE and the SEMAC. MSVAT-SPACE reduced artefacts about 56% compared to the standard SPACE. Effect of the PETRA was dependent on sample used. Image quality and SNR were comparable for all sequences except PETRA, which yielded poor results. There is no benefit in terms of artefact reduction for SEMAC compared to standard TSE. Usage of MSVAT-SPACE is advantageous since artefacts are reduced and higher resolution is achieved. (orig.)

  20. 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.

  1. Topotactic Solid-State Metal Hydride Reductions of Sr2MnO4.

    Science.gov (United States)

    Hernden, Bradley C; Lussier, Joey A; Bieringer, Mario

    2015-05-04

    We report novel details regarding the reactivity and mechanism of the solid-state topotactic reduction of Sr2MnO4 using a series of solid-state metal hydrides. Comprehensive details describing the active reducing species are reported and comments on the reductive mechanism are provided, where it is shown that more than one electron is being donated by H(-). Commonly used solid-state hydrides LiH, NaH, and CaH2, were characterized in terms of reducing power. In addition the unexplored solid-state hydrides MgH2, SrH2, and BaH2 are evaluated as potential solid-state reductants and characterized in terms of their reductive reactivities. These 6 group I and II metal hydrides show the following trend in terms of reactivity: MgH2 < SrH2 < LiH ≈ CaH2 ≈ BaH2 < NaH. The order of the reductants are discussed in terms of metal electronegativity and bond strengths. NaH and the novel use of SrH2 allowed for targeted synthesis of reduced Sr2MnO(4-x) (0 ≤ x ≤ 0.37) phases. The enhanced control during synthesis demonstrated by this soft chemistry approach has allowed for a more comprehensive and systematic evaluation of Sr2MnO(4-x) phases than previously reported phases prepared by high temperature methods. Sr2MnO3.63(1) has for the first time been shown to be monoclinic by powder X-ray diffraction and the oxidative monoclinic to tetragonal transition occurs at 450 °C.

  2. [Examination of patient dose reduction in cardiovasucular X-ray systems with a metal filter].

    Science.gov (United States)

    Yasuda, Mitsuyoshi; Kato, Kyouichi; Tanabe, Nobuaki; Sakiyama, Koushi; Uchiyama, Yushi; Suzuki, Yoshiaki; Suzuki, Hiroshi; Nakazawa, Yasuo

    2012-01-01

    In interventional X-ray for cardiology of flat panel digital detector (FPD), the phenomenon that exposure dose was suddenly increased when a subject thickness was thickened was recognized. At that time, variable metal built-in filters in FPD were all off. Therefore, we examined whether dose reduction was possible without affecting a clinical image using metal filter (filter) which we have been conventionally using for dose reduction. About 45% dose reduction was achieved when we measured an exposure dose at 30 cm of acrylic thickness in the presence of a filter. In addition, we measured signal to noise ratio/contrast to noise ratio/a resolution limit by the visual evaluation, and there was no influence by filter usage. In the clinical examination, visual evaluation of image quality of coronary angiography (40 cases) using a 5-point evaluation scale by a physician was performed. As a result, filter usage did not influence the image quality (p=NS). Therefore, reduction of sudden increase of exposure dose was achieved without influencing an image quality by adding filter to FPD.

  3. Direct reduction of uranium oxide(U3O8) by Li metal and U-metal(Fe, Ni) alloy formation in molten LiCl medium

    International Nuclear Information System (INIS)

    Cho, Young Hwan; Kim, Tack Jin; Choi, In Kyu; Kim, Won Ho; Jee, Kwang Yong

    2004-01-01

    Molten salt based electrochemical processes are proposed as a promising method for the future nuclear programs and more specifically for spent fuel processing. The lithium reduction has been introduced to convert actinide oxides into corresponding actinide metal by using lithium metal as a reductant in molten LiCl medium. We have applied similar lab-scale experiments to reduce uranium oxide in an effort to gain additional information on rates and mechanisms

  4. Iterative metal artefact reduction (MAR) in postsurgical chest CT: comparison of three iMAR-algorithms.

    Science.gov (United States)

    Aissa, Joel; Boos, Johannes; Sawicki, Lino Morris; Heinzler, Niklas; Krzymyk, Karl; Sedlmair, Martin; Kröpil, Patric; Antoch, Gerald; Thomas, Christoph

    2017-11-01

    The purpose of this study was to evaluate the impact of three novel iterative metal artefact (iMAR) algorithms on image quality and artefact degree in chest CT of patients with a variety of thoracic metallic implants. 27 postsurgical patients with thoracic implants who underwent clinical chest CT between March and May 2015 in clinical routine were retrospectively included. Images were retrospectively reconstructed with standard weighted filtered back projection (WFBP) and with three iMAR algorithms (iMAR-Algo1 = Cardiac algorithm, iMAR-Algo2 = Pacemaker algorithm and iMAR-Algo3 = ThoracicCoils algorithm). The subjective and objective image quality was assessed. Averaged over all artefacts, artefact degree was significantly lower for the iMAR-Algo1 (58.9 ± 48.5 HU), iMAR-Algo2 (52.7 ± 46.8 HU) and the iMAR-Algo3 (51.9 ± 46.1 HU) compared with WFBP (91.6 ± 81.6 HU, p algorithms, respectively. iMAR-Algo2 and iMAR-Algo3 reconstructions decreased mild and moderate artefacts compared with WFBP and iMAR-Algo1 (p algorithms led to a significant reduction of metal artefacts and increase in overall image quality compared with WFBP in chest CT of patients with metallic implants in subjective and objective analysis. The iMARAlgo2 and iMARAlgo3 were best for mild artefacts. IMARAlgo1 was superior for severe artefacts. Advances in knowledge: Iterative MAR led to significant artefact reduction and increase image-quality compared with WFBP in CT after implementation of thoracic devices. Adjusting iMAR-algorithms to patients' metallic implants can help to improve image quality in CT.

  5. A particle accelerator probes artifacts

    International Nuclear Information System (INIS)

    Dran, J.C.; Calligaro, Th.; Salomon, J.

    2002-01-01

    The AGLAE system is made up of a 2 mega volts electrostatic accelerator and of 3 irradiation lines: one leads to a vacuum enclosure in which targets are irradiated and the 2 others lines are designed to irradiate targets under an air or helium atmosphere. The AGLAE system is located in the premises of the Louvre museum in Paris and is devoted to the study of cultural objects through ion beam analysis (IBA). 4 techniques are used: -) proton-induced X-ray emission (PIXE) -) proton-induced gamma ray (PIGE) -) Rutherford backscattering spectrometry (NRS) and -) nuclear reaction analysis (NRA). A decisive progress has permitted the direct analysis of artifacts without sampling. The object itself is set just a few millimeters away from the exit window of the beam in an air or helium atmosphere. The exit window must be resistant enough to bear the atmospheric pressure and the damages caused by the proton beam but must be thin enough to not deteriorate the quality of the beam. By using a 10 -7 m thick exit window made of Si 3 N 4 we get a beam whose diameter is 10 -5 m. This new technology presents 4 main advantages: 1) any object of any shape can be studied without sampling, 2) the analysis of very fragile artifacts that might be damaged by the vacuum setting is now possible, 3) a reduction of the thermal side-effects of the beam, and 4) the absence of accumulation of charges in isolating material allows to rid of covering the object with a conducting coating before irradiating it. (A.C.)

  6. The effect of metal artefact reduction on CT-based attenuation correction for PET imaging in the vicinity of metallic hip implants : a phantom study

    NARCIS (Netherlands)

    Harnish, Roy; Prevrhal, Sven; Alavi, Abass; Zaidi, Habib; Lang, Thomas F.

    To determine if metal artefact reduction (MAR) combined with a priori knowledge of prosthesis material composition can be applied to obtain CT-based attenuation maps with sufficient accuracy for quantitative assessment of F-18-fluorodeoxyglucose uptake in lesions near metallic prostheses. A custom

  7. Optimization of scan time in MRI for total hip prostheses. SEMAC tailoring for prosthetic implants containing different types of metals

    Energy Technology Data Exchange (ETDEWEB)

    Deligianni, X. [University of Basel Hospital, Basel (Switzerland). Div. of Radiological Physics; Merian Iselin Klinik, Basel (Switzerland). Inst. of Radiology; Bieri, O. [University of Basel Hospital, Basel (Switzerland). Div. of Radiological Physics; Elke, R. [Orthomerian, Basel (Switzerland); Wischer, T.; Egelhof, T. [Merian Iselin Klinik, Basel (Switzerland). Inst. of Radiology

    2015-12-15

    Magnetic resonance imaging (MRI) of soft tissues after total hip arthroplasty is of clinical interest for the diagnosis of various pathologies that are usually invisible with other imaging modalities. As a result, considerable effort has been put into the development of metal artifact reduction MRI strategies, such as slice encoding for metal artifact correction (SEMAC). Generally, the degree of metal artifact reduction with SEMAC directly relates to the overall time spent for acquisition, but there is no specific consensus about the most efficient sequence setup depending on the implant material. The aim of this article is to suggest material-tailored SEMAC protocol settings. Five of the most common total hip prostheses (1. Revision prosthesis (S-Rom), 2. Titanium alloy, 3. Mueller type (CoNiCRMo alloy), 4. Old Charnley prosthesis (Exeter/Stryker), 5. MS-30 stem (stainless-steel)) were scanned on a 1.5 T MRI clinical scanner with a SEMAC sequence with a range of artifact-resolving slice encoding steps (SES: 2 - 23) along the slice direction (yielding a total variable scan time ranging from 1 to 10 min). The reduction of the artifact volume in comparison with maximal artifact suppression was evaluated both quantitatively and qualitatively in order to establish a recommended number of steps for each case. The number of SES that reduced the artifact volume below approximately 300 mm{sup 3} ranged from 3 to 13, depending on the material. Our results showed that although 3 SES steps can be sufficient for artifact reduction for titanium prostheses, at least 11 SES should be used for prostheses made of materials such as certain alloys of stainless steel. Tailoring SES to the implant material and to the desired degree of metal artifact reduction represents a simple tool for workflow optimization of SEMAC imaging near total hip arthroplasty in a clinical setting.

  8. Optimization of scan time in MRI for total hip prostheses. SEMAC tailoring for prosthetic implants containing different types of metals

    International Nuclear Information System (INIS)

    Deligianni, X.; Wischer, T.; Egelhof, T.

    2015-01-01

    Magnetic resonance imaging (MRI) of soft tissues after total hip arthroplasty is of clinical interest for the diagnosis of various pathologies that are usually invisible with other imaging modalities. As a result, considerable effort has been put into the development of metal artifact reduction MRI strategies, such as slice encoding for metal artifact correction (SEMAC). Generally, the degree of metal artifact reduction with SEMAC directly relates to the overall time spent for acquisition, but there is no specific consensus about the most efficient sequence setup depending on the implant material. The aim of this article is to suggest material-tailored SEMAC protocol settings. Five of the most common total hip prostheses (1. Revision prosthesis (S-Rom), 2. Titanium alloy, 3. Mueller type (CoNiCRMo alloy), 4. Old Charnley prosthesis (Exeter/Stryker), 5. MS-30 stem (stainless-steel)) were scanned on a 1.5 T MRI clinical scanner with a SEMAC sequence with a range of artifact-resolving slice encoding steps (SES: 2 - 23) along the slice direction (yielding a total variable scan time ranging from 1 to 10 min). The reduction of the artifact volume in comparison with maximal artifact suppression was evaluated both quantitatively and qualitatively in order to establish a recommended number of steps for each case. The number of SES that reduced the artifact volume below approximately 300 mm 3 ranged from 3 to 13, depending on the material. Our results showed that although 3 SES steps can be sufficient for artifact reduction for titanium prostheses, at least 11 SES should be used for prostheses made of materials such as certain alloys of stainless steel. Tailoring SES to the implant material and to the desired degree of metal artifact reduction represents a simple tool for workflow optimization of SEMAC imaging near total hip arthroplasty in a clinical setting.

  9. Amorphous metallic alloys for oxygen reduction reaction in a polymer electrolyte membrane fuel cell

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez-Huerta, R.; Guerra-Martinez, I.; Lopez, J.S. [Inst. Politecnico Nacional, ESIQIE, Mexico City (Mexico). Lab. de Electroquimica; Pierna, A.R. [Basque Country Univ., San Sebastian (Spain). Dept. of Chemical Engineering and Environment; Solorza-Feria, O. [Inst. Politenico Nacional, Centro de Investigacion y de Estudios Avanzados, Mexico City (Mexico). Dept. de Quimica

    2010-07-15

    Direct methanol fuel cells (DMFC) and polymer electrolyte membrane fuel cells (PEMFC) represent an important, environmentally clean energy source. This has motivated extensive research on the synthesis, characterization and evaluation of novel and stable oxygen reduction electrocatalysts for the direct four-electron transfer process to water formation. Studies have shown that amorphous alloyed compounds can be used as electrode materials in electrochemical energy conversion devices. Their use in PEMFCs can optimize the electrocatalyst loading in the membrane electrode assembly (MEA). In this study, amorphous metallic PtSn, PtRu and PtRuSn alloys were synthesized by mechanical milling and used as cathodes for the oxygen reduction reaction (ORR) in sulphuric acid and in a single PEM fuel cell. Two different powder morphologies were observed before and after the chemical activation in a hydrofluoric acid (HF) solution at 25 degrees C. The kinetics of the ORR on the amorphous catalysts were investigated. The study showed that the amorphous metallic PtSn electrocatalyst was the most active of the 3 electrodes for the cathodic reaction. Fuel cell experiments were conducted at various temperatures at 30 psi for hydrogen (H{sub 2}) and at 34 psi for oxygen (O{sub 2}). MEAs made of Nafion 115 and amorphous metallic PtSn dispersed on carbon powder in a PEMFC had a power density of 156 mW per cm{sup 2} at 0.43V and 80 degrees C. 12 refs., 1 tab., 5 figs.

  10. Nitrite addition to acidified sludge significantly improves digestibility, toxic metal removal, dewaterability and pathogen reduction

    Science.gov (United States)

    Du, Fangzhou; Keller, Jürg; Yuan, Zhiguo; Batstone, Damien J.; Freguia, Stefano; Pikaar, Ilje

    2016-12-01

    Sludge management is a major issue for water utilities globally. Poor digestibility and dewaterability are the main factors determining the cost for sludge management, whereas pathogen and toxic metal concentrations limit beneficial reuse. In this study, the effects of low level nitrite addition to acidified sludge to simultaneously enhance digestibility, toxic metal removal, dewaterability and pathogen reduction were investigated. Waste activated sludge (WAS) from a full-scale waste water treatment plant was treated at pH 2 with 10 mg NO2--N/L for 5 h. Biochemical methane potential tests showed an increase in the methane production of 28%, corresponding to an improvement from 247 ± 8 L CH4/kg VS to 317 ± 1 L CH4/kg VS. The enhanced removal of toxic metals further increased the methane production by another 18% to 360 ± 6 L CH4/kg VS (a total increase of 46%). The solids content of dewatered sludge increased from 14.6 ± 1.4% in the control to 18.2 ± 0.8%. A 4-log reduction for both total coliforms and E. coli was achieved. Overall, this study highlights the potential of acidification with low level nitrite addition as an effective and simple method achieving multiple improvements in terms of sludge management.

  11. Uranium recovering from slags generated in the metallic uranium by magnesiothermic reduction

    International Nuclear Information System (INIS)

    Fornarolo, F.; Carvalho, E.F. Urano de; Durazzo, M.; Riella, H.G.

    2008-01-01

    The Nuclear Fuel Center of IPEN/CNEN-SP has recent/y concluded a program for developing the fabrication technology of the nuclear fuel based on the U 3 Si 2 -Al dispersion, which is being used in the IEA-R1 research reactor. The uranium silicide (U 3 Si 2 ) fuel production starts with the uranium hexafluoride (UF 6 ) processing and uranium tetrafluoride (UF 4 ) precipitation. Then, the UF 4 is converted to metallic uranium by magnesiothermic reduction. The UF 4 reduction by magnesium generates MgF 2 slag containing considerable concentrations of uranium, which could reach 20 wt%. The uranium contained in that slag should be recovered and this work presents the results obtained in recovering the uranium from that slag. The uranium recovery is accomplished by acidic leaching of the calcined slag. The calcination transforms the metallic uranium in U 3 O 8 , promoting the pulverization of the pieces of metallic uranium and facilitating the leaching operation. As process variables, have been considered the nitric molar concentration, the acid excess regarding the stoichiometry and the leaching temperature. As result, the uranium recovery reached a 96% yield. (author)

  12. Microbial metal reduction by members of the genus Shewanella: novel strategies for anaerobic respiration

    International Nuclear Information System (INIS)

    Dichristina, Thomas; Bates, David J.; Burns, Justin L.; Dale, Jason R.; Payne, Amanda N.

    2006-01-01

    Metal-reducing members of the genus Shewanella are important components of the microbial community residing in redox-stratified freshwater and marine environments. Metal-reducing gram-negative bacteria such as Shewanella, however, are presented with a unique physiological challenge: they are required to respire anaerobically on terminal electron acceptors which are either highly insoluble (Fe(III)- and Mn(IV)-oxides) and reduced to soluble end-products or highly soluble (U(VI) and Tc(VII)) and reduced to insoluble end-products. To overcome physiological problems associated with metal solubility, metal-respiring Shewanella are postulated to employ a variety of novel respiratory strategies not found in other gram-negative bacteria which respire on soluble electron acceptors such as O2, NO3 and SO4. The following chapter highlights the latest findings on the molecular mechanism of Fe(III), U(VI) and Tc(VII) reduction by Shewanella, with particular emphasis on electron transport chain physiology.

  13. Computational simulation studies of the reduction process of UF4 to metallic uranium

    International Nuclear Information System (INIS)

    Borges, Wesden de Almeida

    2011-01-01

    The production of metallic uranium is essential for production of fuel elements for using in nuclear reactors manufacturing of radioisotopes and radiopharmaceuticals. In IPEN, metallic uranium is produced by magnesiothermical reduction of UF 4 . This reaction is performed in a closed graphite crucible inserted in a sealed metal reactor and no contact with the outside environment. The set is gradually heated in an oven pit, until it reaches the ignition temperature of the reaction (between 600-650 degree C). The modeling of the heating profile of the system can be made using simulation programs by finite element method. Through the thermal profiles in the load, we can have a notion of heating period required for the reaction to occur, allowing the identification of the same group in a greater or smaller yield in metallic uranium production. Thermal properties of UF 4 are estimated, obtaining thermal conductivity and heat capacity using the Flash Laser Method, and for the load UF 4 + Mg, either. The results are compared to laboratory tests to simulate the primary production process. (author)

  14. Determination of uranium and plutonium in metal conversion products from electrolytic reduction process

    International Nuclear Information System (INIS)

    Lee, Chang Heon; Suh, Moo Yul; Joe, Kih Soo; Sohn, Se Chul; Jee, Kwang Young; Kim, Won Ho

    2005-01-01

    Chemical characterization of process materials is required for the optimization of an electrolytic reduction process in which uranium dioxide, a matrix of spent PWR fuels, is electrolytically reduced to uranium metal in a medium of LiCl-Li 2 O molten at 650 .deg. C. A study on the determination of fissile materials in the uranium metal products containing corrosion products, fission products and residual process materials has been performed by controlled-potential coulometric titration which is well known in the field of nuclear science and technology. Interference of Fe, Ni, Cr and Mg (corrosion products), Nd (fission product) and LiCl molten salt (residual process material) on the determination of uranium and plutonium, and the necessity of plutonium separation prior to the titration are discussed in detail. Under the analytical condition established already, their recovery yields are evaluated along with analytical reliability

  15. From Ecological Sounding Artifacts Towards Sonic Artifact Ecologies

    DEFF Research Database (Denmark)

    Erkut, Cumhur; Serafin, Stefania

    2016-01-01

    The discipline of sonic interaction design has been focused on the interaction between a single user and an artifact. This strongly limits one of the fundamental aspects of music as a social and interactive experience. In this paper we propose sonic artifact ecologies as a mean to examine interac...

  16. Correction of CT artifacts and its influence on Monte Carlo dose calculations

    International Nuclear Information System (INIS)

    Bazalova, Magdalena; Beaulieu, Luc; Palefsky, Steven; Verhaegen, Frank

    2007-01-01

    Computed tomography (CT) images of patients having metallic implants or dental fillings exhibit severe streaking artifacts. These artifacts may disallow tumor and organ delineation and compromise dose calculation outcomes in radiotherapy. We used a sinogram interpolation metal streaking artifact correction algorithm on several phantoms of exact-known compositions and on a prostate patient with two hip prostheses. We compared original CT images and artifact-corrected images of both. To evaluate the effect of the artifact correction on dose calculations, we performed Monte Carlo dose calculation in the EGSnrc/DOSXYZnrc code. For the phantoms, we performed calculations in the exact geometry, in the original CT geometry and in the artifact-corrected geometry for photon and electron beams. The maximum errors in 6 MV photon beam dose calculation were found to exceed 25% in original CT images when the standard DOSXYZnrc/CTCREATE calibration is used but less than 2% in artifact-corrected images when an extended calibration is used. The extended calibration includes an extra calibration point for a metal. The patient dose volume histograms of a hypothetical target irradiated by five 18 MV photon beams in a hypothetical treatment differ significantly in the original CT geometry and in the artifact-corrected geometry. This was found to be mostly due to miss-assignment of tissue voxels to air due to metal artifacts. We also developed a simple Monte Carlo model for a CT scanner and we simulated the contribution of scatter and beam hardening to metal streaking artifacts. We found that whereas beam hardening has a minor effect on metal artifacts, scatter is an important cause of these artifacts

  17. Reduction by metals dissolved in liquid ammonia of keto steroids. Equilibration of the alcohols

    International Nuclear Information System (INIS)

    Giroud, A.M.

    1970-01-01

    Reducing a ketone by dissolved metals involves two electrons; we may consider as intermediate a radical-anion, then a di-anion or a carbo-anion. The radical-anion may also split and give pinacols away. In order to discuss the reduction proceeds, we had to know the respective stabilities of the alcohols, which lead us to effectuate equilibration. The first chapter is devoted to the method of preparing the androstanone-II and the androstanols-IIα and II-β. We further establish the impossibility of using our methods for reaching a conclusion about the alcohols relative stability by experimental equilibration. Last we describe the methods for reducing the ketone by alkaline and earth-alkaline metals, dissolved in liquid ammonia, either in contact with a protons donor or with a later added protons donor. The resulting mixture of the two alcohols shows a prevailing quantity of the stable equatorial isomer α. In a second chapter, we study the action of selenic acid and hydroperoxide on cholestanone-3, which leads us to study the preparation and stereochemistry of the A-nor cholestane derivates. We further describe the preparation of the A-nor cholestanols-2α and 2β, and the corresponding acetates. Equilibration of the alcohols by chemical methods shows the 2 α-alcohol more stable than the 2β, which is mathematically confirmed. Last, the reduction of the A-nor cholestanone-2 by dissolved metals consistently leads to the less stable 2 β epimer, with associated pinacols. The third chapter is devoted to the study of the androstanone-17 reductions, and the relative stabilities of the 17α and 17β alcohols. Whichever operating methods is used, we predominantly obtain the more stable 17β alcohol. In all cases, a pinacol production is observed. Summing up, we note that, in all cases, we predominantly obtain the equatorial epimer, whether it should be the more stable or the less stable. (author) [fr

  18. Inspection about the corrosion of metallic archaeological artifacts in ground (4). Document prepared by other institute, based on the trust contract

    International Nuclear Information System (INIS)

    Honda, Takashi; Yamaguchi, Shingo

    2004-01-01

    In general, it is difficult to evaluate non-destructively the corroded states of iron-based archaeological remains, as they are fully covered by thick rust formed under ground during a long period over a hundred years. The purpose of this study is to estimate the corrosion amounts of such remains with using X-ray CT and summarize the longevity of iron in soil. Eight remains dug out at seven relics were analyzed. The burial periods in soil were estimated to be from 1000 to 1700 years. Metallic iron remained in six remains, and the corrosion amounts were figured out to be from 1 to 3 mm in these periods. In addition, the soil environments of relics were analyzed, and the relation between corrosion behaviors and environmental factors was discussed. The rust was composed of outer goethite and inner magnetite layers in normally oxidizing conditions. On the other hand, a few samples were buried in slightly oxidizing environments, and these were covered by magnetite single layers. The corrosion amount of remains in such an environment was small compared to the others. (author)

  19. Catalytic reduction of nitric oxide with ammonia over transition metal ion-exchanged Y zeolites

    Energy Technology Data Exchange (ETDEWEB)

    Sciyama, T; Arakawa, T; Matsuda, T; Yamazoe, N; Takita, Y

    1975-01-01

    The catalytic reduction of nitric oxide with ammonia was studied over transition metal ion-exchanged Y zeolite (Me-Y) catalysts. The reaction products are nitrogen, nitrous oxide, and water in all cases. Selectivities to N/sub 2/ are 60 to 80% on all the cation exchanged zeolite catalysts exhibiting a relatively minor variation with the cationic species exchanged. The copper (II)-Y catalyst exhibits low temperature activity and has an unusual catalytic activity-temperature profile with a maximum at 120/sup 0/C. The catalytic activity is enhanced considerably when a second cation, especially cobalt (II) or iron (III) is coexchanged together with Cu (II) in Y zeolite.

  20. Metal-Organic-Framework-Mediated Nitrogen-Doped Carbon for CO2 Electrochemical Reduction

    KAUST Repository

    Wang, Riming; Sun, Xiaohui; Ould-Chikh, Samy; Osadchii, Dmitrii; Bai, Fan; Kapteijn, Freek; Gascon, Jorge

    2018-01-01

    A nitrogen-doped carbon was synthesized through the pyrolysis of the well-known metal-organic framework ZIF-8, followed by a subsequent acid treatment, and has been applied as a catalyst in the electrochemical reduction of carbon dioxide. The resulting electrode shows Faradaic efficiencies to carbon monoxide as high as ∼78%, with hydrogen being the only byproduct. The pyrolysis temperature determines the amount and the accessibility of N species in the carbon electrode, in which pyridinic-N and quaternary-N species play key roles in the selective formation of carbon monoxide.

  1. Weight reduction of vehicles and light metals; Jidosya no keryoka to keikinzoku zairyo

    Energy Technology Data Exchange (ETDEWEB)

    Manabe, Akira. [Toyota Motor Corp., Aichi (Japan). Component and System Development Center

    1999-08-15

    Weight reduction of vehicles (WRV) is a continuous challenge from the beginning of the vehicle history, however the purpose of WRV has been changing by social requirements. Recently automotive industry is facing is facing with the global warmin and the other environmental issues, so we are vast amount of R and D resources to improve the fuel economy. In this paper, the changes of the purpose of WRV and, the relation between fuel economy and WRV, are summarized. And also the current status of light metals usage and the future work for the related material issues, in particuar the corrosion resistance, are brifly mentioned. (author)

  2. Metal-Organic-Framework-Mediated Nitrogen-Doped Carbon for CO2 Electrochemical Reduction

    KAUST Repository

    Wang, Riming

    2018-04-11

    A nitrogen-doped carbon was synthesized through the pyrolysis of the well-known metal-organic framework ZIF-8, followed by a subsequent acid treatment, and has been applied as a catalyst in the electrochemical reduction of carbon dioxide. The resulting electrode shows Faradaic efficiencies to carbon monoxide as high as ∼78%, with hydrogen being the only byproduct. The pyrolysis temperature determines the amount and the accessibility of N species in the carbon electrode, in which pyridinic-N and quaternary-N species play key roles in the selective formation of carbon monoxide.

  3. Mechanisms of Furfural Reduction on Metal Electrodes: Distinguishing Pathways for Selective Hydrogenation of Bioderived Oxygenates

    International Nuclear Information System (INIS)

    Chadderdon, Xiaotong H.; Chadderdon, David J.; Matthiesen, John E.

    2017-01-01

    Electrochemical reduction of biomass-derived platform molecules is an emerging route for the sustainable production of fuels and chemicals. Understanding gaps between reaction conditions, underlying mechanisms, and product selectivity have limited the rational design of active, stable, and selective catalyst systems. Here, the mechanisms of electrochemical reduction of furfural, an important biobased platform molecule and model for aldehyde reduction, are explored through a combination of voltammetry, preparative electrolysis, thiol-electrode modifications, and kinetic isotope studies. It is demonstrated that two distinct mechanisms are operable on metallic Cu electrodes in acidic electrolytes: (i) electrocatalytic hydrogenation (ECH) and (ii) direct electroreduction. The contributions of each mechanism to the observed product distribution are clarified by evaluating the requirement for direct chemical interactions with the electrode surface and the role of adsorbed hydrogen. Further analysis reveals that hydrogenation and hydrogenolysis products are generated by parallel ECH pathways. By understanding the underlying mechanisms it enables the manipulation of furfural reduction by rationally tuning the electrode potential, electrolyte pH, and furfural concentration to promote selective formation of important biobased polymer precursors and fuels.

  4. Mechanisms of Furfural Reduction on Metal Electrodes: Distinguishing Pathways for Selective Hydrogenation of Bioderived Oxygenates.

    Science.gov (United States)

    Chadderdon, Xiaotong H; Chadderdon, David J; Matthiesen, John E; Qiu, Yang; Carraher, Jack M; Tessonnier, Jean-Philippe; Li, Wenzhen

    2017-10-11

    Electrochemical reduction of biomass-derived platform molecules is an emerging route for the sustainable production of fuels and chemicals. However, understanding gaps between reaction conditions, underlying mechanisms, and product selectivity have limited the rational design of active, stable, and selective catalyst systems. In this work, the mechanisms of electrochemical reduction of furfural, an important biobased platform molecule and model for aldehyde reduction, are explored through a combination of voltammetry, preparative electrolysis, thiol-electrode modifications, and kinetic isotope studies. It is demonstrated that two distinct mechanisms are operable on metallic Cu electrodes in acidic electrolytes: (i) electrocatalytic hydrogenation (ECH) and (ii) direct electroreduction. The contributions of each mechanism to the observed product distribution are clarified by evaluating the requirement for direct chemical interactions with the electrode surface and the role of adsorbed hydrogen. Further analysis reveals that hydrogenation and hydrogenolysis products are generated by parallel ECH pathways. Understanding the underlying mechanisms enables the manipulation of furfural reduction by rationally tuning the electrode potential, electrolyte pH, and furfural concentration to promote selective formation of important biobased polymer precursors and fuels.

  5. Bacterial assimilation reduction of iron in the treatment of non-metallics

    Directory of Open Access Journals (Sweden)

    Peter Malachovský

    2005-11-01

    Full Text Available Natural non-metallics, including granitoide and quartz sands, often contain iron which decreases the whiteness of these raw materials. Insoluble Fe3+ in these samples could be reduced to soluble Fe2+ by bacteria of Bacillus spp. and Saccharomyces spp. The leaching effect, observed by the measurement of Fe2+concentration in a solution, showed higher activities of a bacterial kind isolated from the Bajkal lake and also by using of yeast Saccharomyces sp. during bioleaching of quartz sands. However, allkinds of Bacillus spp. isolated from the Slovak deposit and from Bajkal lake were very active in the iron reduction during bioleaching of the feldspar raw material. This metal was efficiently removed from quartz sands as documented by the Fe2O3 decrease (from 0,317 % to 0,126 % and from feldpars raw materials by the Fe2O3 decrease (from 0,288 % to 0,115 % after bioleaching. The whiteness of these non-metallics was increased during a visual comparison of samples before and after bioleaching but samples contain selected magnetic particles. A removal of iron as well as a release of iron minerals from silicate matrix should increase the effect of the magnetic separation and should give a product which is suitable for industrial applications.

  6. A pseudo-discrete algebraic reconstruction technique (PDART) prior image-based suppression of high density artifacts in computed tomography

    Energy Technology Data Exchange (ETDEWEB)

    Pua, Rizza; Park, Miran; Wi, Sunhee; Cho, Seungryong, E-mail: scho@kaist.ac.kr

    2016-12-21

    We propose a hybrid metal artifact reduction (MAR) approach for computed tomography (CT) that is computationally more efficient than a fully iterative reconstruction method, but at the same time achieves superior image quality to the interpolation-based in-painting techniques. Our proposed MAR method, an image-based artifact subtraction approach, utilizes an intermediate prior image reconstructed via PDART to recover the background information underlying the high density objects. For comparison, prior images generated by total-variation minimization (TVM) algorithm, as a realization of fully iterative approach, were also utilized as intermediate images. From the simulation and real experimental results, it has been shown that PDART drastically accelerates the reconstruction to an acceptable quality of prior images. Incorporating PDART-reconstructed prior images in the proposed MAR scheme achieved higher quality images than those by a conventional in-painting method. Furthermore, the results were comparable to the fully iterative MAR that uses high-quality TVM prior images. - Highlights: • An accelerated reconstruction method, PDART, is proposed for exterior problems. • With a few iterations, soft prior image was reconstructed from the exterior data. • PDART framework has enabled an efficient hybrid metal artifact reduction in CT.

  7. Copper-Based Metal-Organic Porous Materials for CO2 Electrocatalytic Reduction to Alcohols.

    Science.gov (United States)

    Albo, Jonathan; Vallejo, Daniel; Beobide, Garikoitz; Castillo, Oscar; Castaño, Pedro; Irabien, Angel

    2017-03-22

    The electrocatalytic reduction of CO 2 has been investigated using four Cu-based metal-organic porous materials supported on gas diffusion electrodes, namely, (1) HKUST-1 metal-organic framework (MOF), [Cu 3 (μ 6 -C 9 H 3 O 6 ) 2 ] n ; (2) CuAdeAce MOF, [Cu 3 (μ 3 -C 5 H 4 N 5 ) 2 ] n ; (3) CuDTA mesoporous metal-organic aerogel (MOA), [Cu(μ-C 2 H 2 N 2 S 2 )] n ; and (4) CuZnDTA MOA, [Cu 0.6 Zn 0.4 (μ-C 2 H 2 N 2 S 2 )] n . The electrodes show relatively high surface areas, accessibilities, and exposure of the Cu catalytic centers as well as favorable electrocatalytic CO 2 reduction performance, that is, they have a high efficiency for the production of methanol and ethanol in the liquid phase. The maximum cumulative Faradaic efficiencies for CO 2 conversion at HKUST-1-, CuAdeAce-, CuDTA-, and CuZnDTA-based electrodes are 15.9, 1.2, 6, and 9.9 %, respectively, at a current density of 10 mA cm -2 , an electrolyte-flow/area ratio of 3 mL min cm -2 , and a gas-flow/area ratio of 20 mL min cm -2 . We can correlate these observations with the structural features of the electrodes. Furthermore, HKUST-1- and CuZnDTA-based electrodes show stable electrocatalytic performance for 17 and 12 h, respectively. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Approaches to reducing photon dose calculation errors near metal implants

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Jessie Y.; Followill, David S.; Howell, Rebecca M.; Mirkovic, Dragan; Kry, Stephen F., E-mail: sfkry@mdanderson.org [Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, Texas 77030 and Graduate School of Biomedical Sciences, The University of Texas Health Science Center Houston, Houston, Texas 77030 (United States); Liu, Xinming [Department of Imaging Physics, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, Texas 77030 and Graduate School of Biomedical Sciences, The University of Texas Health Science Center Houston, Houston, Texas 77030 (United States); Stingo, Francesco C. [Department of Biostatistics, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, Texas 77030 and Graduate School of Biomedical Sciences, The University of Texas Health Science Center Houston, Houston, Texas 77030 (United States)

    2016-09-15

    Purpose: Dose calculation errors near metal implants are caused by limitations of the dose calculation algorithm in modeling tissue/metal interface effects as well as density assignment errors caused by imaging artifacts. The purpose of this study was to investigate two strategies for reducing dose calculation errors near metal implants: implementation of metal-based energy deposition kernels in the convolution/superposition (C/S) dose calculation method and use of metal artifact reduction methods for computed tomography (CT) imaging. Methods: Both error reduction strategies were investigated using a simple geometric slab phantom with a rectangular metal insert (composed of titanium or Cerrobend), as well as two anthropomorphic phantoms (one with spinal hardware and one with dental fillings), designed to mimic relevant clinical scenarios. To assess the dosimetric impact of metal kernels, the authors implemented titanium and silver kernels in a commercial collapsed cone C/S algorithm. To assess the impact of CT metal artifact reduction methods, the authors performed dose calculations using baseline imaging techniques (uncorrected 120 kVp imaging) and three commercial metal artifact reduction methods: Philips Healthcare’s O-MAR, GE Healthcare’s monochromatic gemstone spectral imaging (GSI) using dual-energy CT, and GSI with metal artifact reduction software (MARS) applied. For the simple geometric phantom, radiochromic film was used to measure dose upstream and downstream of metal inserts. For the anthropomorphic phantoms, ion chambers and radiochromic film were used to quantify the benefit of the error reduction strategies. Results: Metal kernels did not universally improve accuracy but rather resulted in better accuracy upstream of metal implants and decreased accuracy directly downstream. For the clinical cases (spinal hardware and dental fillings), metal kernels had very little impact on the dose calculation accuracy (<1.0%). Of the commercial CT artifact

  9. Approaches to reducing photon dose calculation errors near metal implants

    International Nuclear Information System (INIS)

    Huang, Jessie Y.; Followill, David S.; Howell, Rebecca M.; Mirkovic, Dragan; Kry, Stephen F.; Liu, Xinming; Stingo, Francesco C.

    2016-01-01

    Purpose: Dose calculation errors near metal implants are caused by limitations of the dose calculation algorithm in modeling tissue/metal interface effects as well as density assignment errors caused by imaging artifacts. The purpose of this study was to investigate two strategies for reducing dose calculation errors near metal implants: implementation of metal-based energy deposition kernels in the convolution/superposition (C/S) dose calculation method and use of metal artifact reduction methods for computed tomography (CT) imaging. Methods: Both error reduction strategies were investigated using a simple geometric slab phantom with a rectangular metal insert (composed of titanium or Cerrobend), as well as two anthropomorphic phantoms (one with spinal hardware and one with dental fillings), designed to mimic relevant clinical scenarios. To assess the dosimetric impact of metal kernels, the authors implemented titanium and silver kernels in a commercial collapsed cone C/S algorithm. To assess the impact of CT metal artifact reduction methods, the authors performed dose calculations using baseline imaging techniques (uncorrected 120 kVp imaging) and three commercial metal artifact reduction methods: Philips Healthcare’s O-MAR, GE Healthcare’s monochromatic gemstone spectral imaging (GSI) using dual-energy CT, and GSI with metal artifact reduction software (MARS) applied. For the simple geometric phantom, radiochromic film was used to measure dose upstream and downstream of metal inserts. For the anthropomorphic phantoms, ion chambers and radiochromic film were used to quantify the benefit of the error reduction strategies. Results: Metal kernels did not universally improve accuracy but rather resulted in better accuracy upstream of metal implants and decreased accuracy directly downstream. For the clinical cases (spinal hardware and dental fillings), metal kernels had very little impact on the dose calculation accuracy (<1.0%). Of the commercial CT artifact

  10. Radiolytic and photochemical reduction of carbon dioxide in solution catalyzed by transition metal complexes with some selected macrocycles

    International Nuclear Information System (INIS)

    Grodkowski, J.

    2004-01-01

    The main goal of the work presented in this report is an explanation of the mechanism of carbon dioxide (CO 2 ) reduction catalyzed by transition metal complexes with some selected macrocycles. The catalytic function of two electron exchange centers in the reduction of CO 2 , an inner metal and a macrocycle ring, was defined. Catalytic effects of rhodium, iron and cobalt porphyrins, cobalt and iron phthalocyanines and corroles as well as cobalt corrins have been investigated. CO 2 reduction by iron ions without presence of macrocycles and also in presence of copper compounds in aqueous solutions have been studied as well

  11. Coupled Metal/Oxide Catalysts with Tunable Product Selectivity for Electrocatalytic CO2 Reduction.

    Science.gov (United States)

    Huo, Shengjuan; Weng, Zhe; Wu, Zishan; Zhong, Yiren; Wu, Yueshen; Fang, Jianhui; Wang, Hailiang

    2017-08-30

    One major challenge to the electrochemical conversion of CO 2 to useful fuels and chemical products is the lack of efficient catalysts that can selectively direct the reaction to one desirable product and avoid the other possible side products. Making use of strong metal/oxide interactions has recently been demonstrated to be effective in enhancing electrocatalysis in the liquid phase. Here, we report one of the first systematic studies on composition-dependent influences of metal/oxide interactions on electrocatalytic CO 2 reduction, utilizing Cu/SnO x heterostructured nanoparticles supported on carbon nanotubes (CNTs) as a model catalyst system. By adjusting the Cu/Sn ratio in the catalyst material structure, we can tune the products of the CO 2 electrocatalytic reduction reaction from hydrocarbon-favorable to CO-selective to formic acid-dominant. In the Cu-rich regime, SnO x dramatically alters the catalytic behavior of Cu. The Cu/SnO x -CNT catalyst containing 6.2% of SnO x converts CO 2 to CO with a high faradaic efficiency (FE) of 89% and a j CO of 11.3 mA·cm -2 at -0.99 V versus reversible hydrogen electrode, in stark contrast to the Cu-CNT catalyst on which ethylene and methane are the main products for CO 2 reduction. In the Sn-rich regime, Cu modifies the catalytic properties of SnO x . The Cu/SnO x -CNT catalyst containing 30.2% of SnO x reduces CO 2 to formic acid with an FE of 77% and a j HCOOH of 4.0 mA·cm -2 at -0.99 V, outperforming the SnO x -CNT catalyst which only converts CO 2 to formic acid in an FE of 48%.

  12. An Integrated Assessment of Geochemical and Community Structure Determinants of Metal Reduction Rates in Subsurface Sediments. Final report

    International Nuclear Information System (INIS)

    Pfiffner, Susan

    2010-01-01

    The objective of this research was to examine the importance of microbial community structure in influencing uranium reduction rates in subsurface sediments. If the redox state alone is the key to metal reduction, then any organisms that can utilize the oxygen and nitrate in the subsurface can change the geochemical conditions so metal reduction becomes an energetically favored reaction. Thus, community structure would not be critical in determining rates or extent of metal reduction unless community structure influenced the rate of change in redox. Alternatively, some microbes may directly catalyze metal reduction (e.g., specifically reduce U). In this case the composition of the community may be more important and specific types of electron donors may promote the production of communities that are more adept at U reduction. Our results helped determine if the type of electron donor or the preexisting community is important in the bioremediation of metal-contaminated environments subjected to biostimulation. In a series of experiments at the DOE FRC site in Oak Ridge we have consistently shown that all substrates promoted nitrate reduction, while glucose, ethanol, and acetate always promoted U reduction. Methanol only occasionally promoted extensive U reduction which is possibly due to community heterogeneity. There appeared to be limitations imposed on the community related to some substrates (e.g. methanol and pyruvate). Membrane lipid analyses (phospholipids and respiratory quinones) indicated different communities depending on electron donor used. Terminal restriction fragment length polymorphism and clone libraries indicated distinct differences among communities even in treatments that promoted U reduction. Thus, there was enough metabolic diversity to accommodate many different electron donors resulting in the U bioimmobilization.

  13. Enhancement of oxygen reduction at Fe tetrapyridyl porphyrin by pyridyl-N coordination to transition metal ions

    International Nuclear Information System (INIS)

    Maruyama, Jun; Baier, Claudia; Wolfschmidt, Holger; Bele, Petra; Stimming, Ulrich

    2012-01-01

    One of the promising candidates as noble-metal-free electrode catalysts for polymer electrolyte fuel cells (PEFCs) is a carbon material with nitrogen atoms coordinating iron ions embedded on the surface (Fe-N x moiety) as the active site, although the activity is insufficient compared to conventional platinum-based electrocatalysts. In order to obtain fundamental information on the activity enhancement, a simple model of the Fe-N x active site was formed by adsorbing 5,10,15,20-Tetrakis(4-pyridyl)-21H,23H-porphine iron(III) chloride (FeTPyPCl) on the basal plane of highly oriented pyrolytic graphite (HOPG), and cathodic oxygen reduction was investigated on the surface in 0.1 M HClO 4 . The catalytic activity for oxygen reduction was enhanced by loading transition metal ions (Co 2+ , Ni 2+ , Cu 2+ ) together with FeTPyPCl. The X-ray photoelectron spectrum of the surface suggested that the metal was coordinated by the pyridine-N. The enhancement effect of the transition metals was supported by two different measurements: oxygen reduction at HOPG in 0.1 M HClO 4 dissolving FeTPyPCl and the metal ions; oxygen reduction in 0.1 M HClO 4 at the subsequently well-rinsed and dried HOPG. The ultraviolet–visible spectrum for the solution also suggested the coordination between the pyridyl-N and the metal ions. The oxygen reduction enhancement was attributed to the electronic interaction between the additional transition metal and the Fe center of the porphyrin through the coordination bonds. These results implied that the improvement of the activity of the noble-metal-free catalyst would be possible by the proper introduction of the transition metal ions around the active site.

  14. Metal- and Carbon-Based Materials as Heterogeneous Electrocatalysts for CO₂ Reduction.

    Science.gov (United States)

    Khan, Azam; Ullah, Haseeb; Nasir, Jamal Abdul; Shuda, Suzanne; Chen, Wei; Khan, M Abdullah

    2018-05-01

    Climate change caused by continuous rising level of CO2 and the depletion of fossil fuels reserves has made it highly desirable to electrochemically convert CO2 into fuels and commodity chemicals. Implementing this approach will close the carbon cycle by recycling CO2 providing a sustainable way to store energy in the chemical bonds of portable molecular fuels. In order to make the process commercially viable, the challenge of slow kinetics of CO2 electroreduction and low energy efficiency of the process need to be addressed. To this end, this review summarizes the progress made in the past few years in the development of heterogeneous electrocatalysts with a focus on nanostructured material for CO2 reduction to CO, HCOOH/HCOO-, CH2O, CH4, H2C2O4/HC2O-4, C2H4, CH3OH, CH3CH2OH, etc. The electrocatalysts presented here are classified into metals, metal alloys, metal oxides, metal chalcogenides and carbon based materials on the basis of their elemental composition, whose performance is discussed in light of catalyst activity, product selectivity, Faradaic efficiency (FE), catalytic durability and in selected cases mechanism of CO2 electroreduction. The effect of particle size, morphology and solution-electrolyte type and composition on the catalyst property/activity is also discussed and finally some strategies are proposed for the development of CO2 electroreduction catalysts. The aim of this article is to review the recent advances in the field of CO2 electroreduction in order to further facilitate research and development in this area.

  15. An Integrated Assessment of Geochemical and Community Structure Determinants of Metal Reduction Rates in Subsurface Sediments

    International Nuclear Information System (INIS)

    Pfiffner, Susan M.; Brandt, Craig C.; Kostka, Joel E.; Palumbo, Anthony V.

    2005-01-01

    Our current research represents a joint effort between Oak Ridge National Laboratory (ORNL), Florida State University (FSU), and the University of Tennessee. ORNL will serve as the lead institution with Dr. A.V. Palumbo responsible for project coordination, integration, and deliverables. This project was initiated in November, 2004, in the Integrative Studies Element of the NABIR program. The overall goal of our project is to provide an improved understanding of the relationships between microbial community structure, geochemistry, and metal reduction rates. The research seeks to address the following questions: Is the metabolic diversity of the in situ microbial community sufficiently large and redundant that bioimmobilization of uranium will occur regardless of the type of electron donor added to the system? Are their donor specific effects that lead to enrichment of specific community members that then impose limits on the functional capabilities of the system? Will addition of humics change rates of uranium reduction without changing community structure? Can resource-ratio theory be used to understand changes in uranium reduction rates and community structure with respect to changing C:P ratios?

  16. Electrochemical Reduction of CO2 at Metal Electrodes in a Distillable Ionic Liquid.

    Science.gov (United States)

    Chen, Lu; Guo, Si-Xuan; Li, Fengwang; Bentley, Cameron; Horne, Mike; Bond, Alan M; Zhang, Jie

    2016-06-08

    The electroreduction of CO2 in the distillable ionic liquid dimethylammonium dimethylcarbamate (dimcarb) has been investigated with 17 metal electrodes. Analysis of the electrolysis products reveals that aluminum, bismuth, lead, copper, nickel, palladium, platinum, iron, molybdenum, titanium and zirconium electroreduce the available protons in dimcarb to hydrogen rather than reducing CO2 . Conversely, indium, tin, zinc, silver and gold are able to catalyze the reduction of CO2 to predominantly carbon monoxide (CO) and to a lesser extent, formate ([HCOO](-) ). In all cases, the applied potential was found to have a minimal influence on the distribution of the reduction products. Overall, indium was found to be the best electrocatalyst for CO2 reduction in dimcarb, with faradaic efficiencies of approximately 45 % and 40 % for the generation of CO and [HCOO](-) , respectively, at a potential of -1.34 V versus Cc(+/0) (Cc(+) =cobaltocenium) employing a dimethylamine to CO2 ratio of less than 1.8:1. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Turquoise Artifact from Teotihuacan

    Energy Technology Data Exchange (ETDEWEB)

    Spence, Michael W.; Harbottle, Garman; Weigand, Phil C.

    1999-07-01

    Turquoise artifacts appeared sporadically in Mesoamerica as early as the Formative period (Merry de Morales 1987:100, Figure 8.4; Weigand 1989:43). Most occurrences, however, postdate the collapse of Teotihuacan. In the Late Classic and Postclassic periods increasing quantities are found, often in the form of elaborate mosaics, in a wide variety of contexts in central, west and northwest Mexico. Neutron activation analysis has determined that much of this turquoise derives from sources in the southwestern United States (Weigand et al. 1977; Harbottle and Weigand 1992; Weigand and Harbottle 1993). Teotihuacan played a major role in Mesoamerica during the Terminal Formative and Early-Middle Classic periods. It was the dominant power in central Mexico from about the time of Christ to its collapse at about A.D. 650 (Millon 1988, 1992; Cowgill 1996). Throughout this period goods flowed into Teotihuacan from many parts of the Mesoamerican world. Despite this widespread economic interaction, only two pieces of turquoise have been recovered in the city. In the following pages, the context and implications of one of these finds will be examined.

  18. Investigating media artifacts with children

    DEFF Research Database (Denmark)

    Chimirri, Niklas Alexander

    The dissertation’s aim is to explore the everyday relevance media artifacts have for young children. It discusses and further develops analytical concepts that are committed to taking the children’s perspectives on possibilities and limitations of such artifacts seriously. These conceptual...... developments are rooted in the author’s participation in a daycare practice in Berlin, Germany. The daycare’s situational approach precisely attempted to draw on the children’s everyday life experiences so as to engage in problem-oriented learning projects, on media artifacts and beyond....

  19. Metal artefact reduction in MRI at both 1.5 and 3.0 T using slice encoding for metal artefact correction and view angle tilting

    Science.gov (United States)

    Reichert, M; Morelli, J N; Nittka, M; Attenberger, U; Runge, V M

    2015-01-01

    Objective: To compare metal artefact reduction in MRI at both 3.0 T and 1.5 T using different sequence strategies. Methods: Metal implants of stainless steel screw and plate within agarose phantoms and tissue specimens as well as three patients with implants were imaged at both 1.5 T and 3.0 T, using view angle tilting (VAT), slice encoding for metal artefact correction with VAT (SEMAC-VAT) and conventional sequence. Artefact reduction in agarose phantoms was quantitatively assessed by artefact volume measurements. Blinded reads were conducted in tissue specimen and human imaging, with respect to artefact size, distortion, blurring and overall image quality. Wilcoxon and Friedman tests for multiple comparisons and intraclass correlation coefficient (ICC) for interobserver agreement were performed with a significant level of p 3.0 T (p 3.0 T. Advances in knowledge: The feasibility of metal artefact reduction with SEMAC-VAT was demonstrated at 3.0-T MR. SEMAC-VAT significantly reduced metal artefacts at both 1.5 and 3.0 T. SEMAC-VAT allowed for better visualization of the tissue structures adjacent to the metal implants. SEMAC-VAT produced consistently better image quality in both tissue specimen and human imaging. PMID:25613398

  20. Clinical evaluation of TOF versus non-TOF on PET artifacts in simultaneous PET/MR: a dual centre experience

    Energy Technology Data Exchange (ETDEWEB)

    Voert, Edwin E.G.W. ter [University Hospital Zurich, Department of Nuclear Medicine, Zurich (Switzerland); University of Zurich, Zurich (Switzerland); Veit-Haibach, Patrick [University Hospital Zurich, Department of Nuclear Medicine, Zurich (Switzerland); University of Zurich, Zurich (Switzerland); University Hospital Zurich, Department of Diagnostic and Interventional Radiology, Zurich (Switzerland); Ahn, Sangtae [GE Global Research, Niskayuna, NY (United States); Wiesinger, Florian [GE Global Research, Muenchen (Germany); Khalighi, M.M.; Delso, Gaspar [GE Healthcare, Waukesha, WI (United States); Levin, Craig S. [Stanford University, Department of Radiology, Molecular Imaging Program at Stanford, Stanford, CA (United States); Iagaru, Andrei H. [Stanford University, Department of Radiology, Division of Nuclear Medicine and Molecular Imaging, Stanford, CA (United States); Zaharchuk, Greg [Stanford University, Department of Radiology, Neuroradiology, Stanford, CA (United States); Huellner, Martin [University Hospital Zurich, Department of Nuclear Medicine, Zurich (Switzerland); University of Zurich, Zurich (Switzerland); University Hospital Zurich, Department of Neuroradiology, Zurich (Switzerland)

    2017-07-15

    Our objective was to determine clinically the value of time-of-flight (TOF) information in reducing PET artifacts and improving PET image quality and accuracy in simultaneous TOF PET/MR scanning. A total 65 patients who underwent a comparative scan in a simultaneous TOF PET/MR scanner were included. TOF and non-TOF PET images were reconstructed, clinically examined, compared and scored. PET imaging artifacts were categorized as large or small implant-related artifacts, as dental implant-related artifacts, and as implant-unrelated artifacts. Differences in image quality, especially those related to (implant) artifacts, were assessed using a scale ranging from 0 (no artifact) to 4 (severe artifact). A total of 87 image artifacts were found and evaluated. Four patients had large and eight patients small implant-related artifacts, 27 patients had dental implants/fillings, and 48 patients had implant-unrelated artifacts. The average score was 1.14 ± 0.82 for non-TOF PET images and 0.53 ± 0.66 for TOF images (p < 0.01) indicating that artifacts were less noticeable when TOF information was included. Our study indicates that PET image artifacts are significantly mitigated with integration of TOF information in simultaneous PET/MR. The impact is predominantly seen in patients with significant artifacts due to metal implants. (orig.)

  1. Prototype metal artefact reduction algorithm in flat panel computed tomography - evaluation in patients undergoing transarterial hepatic radioembolisation.

    Science.gov (United States)

    Hamie, Qeumars Mustafa; Kobe, Adrian Raoul; Mietzsch, Leif; Manhart, Michael; Puippe, Gilbert Dominique; Pfammatter, Thomas; Guggenberger, Roman

    2018-01-01

    To investigate the effect of an on-site prototype metal artefact reduction (MAR) algorithm in cone-beam CT-catheter-arteriography (CBCT-CA) in patients undergoing transarterial radioembolisation (RE) of hepatic masses. Ethical board approved retrospective study of 29 patients (mean 63.7±13.7 years, 11 female), including 16 patients with arterial metallic coils, undergoing CBCT-CA (8s scan, 200 degrees rotation, 397 projections). Image reconstructions with and without prototype MAR algorithm were evaluated quantitatively (streak-artefact attenuation changes) and qualitatively (visibility of hepatic parenchyma and vessels) in near- (3cm) of artefact sources (metallic coils and catheters). Quantitative and qualitative measurements of uncorrected and MAR corrected images and different artefact sources were compared RESULTS: Quantitative evaluation showed significant reduction of near- and far-field streak-artefacts with MAR for both artefact sources (p0.05). Inhomogeneities of attenuation values were significantly higher for metallic coils compared to catheters (pprototype MAR algorithm improves image quality in proximity of metallic coil and catheter artefacts. • Metal objects cause artefacts in cone-beam computed tomography (CBCT) imaging. • These artefacts can be corrected by metal artefact reduction (MAR) algorithms. • Corrected images show significantly better visibility of nearby hepatic vessels and tissue. • Better visibility may facilitate image interpretation, save time and radiation exposure.

  2. Optimized protocols for cardiac magnetic resonance imaging in patients with thoracic metallic implants

    Energy Technology Data Exchange (ETDEWEB)

    Olivieri, Laura J.; Ratnayaka, Kanishka [Children' s National Health System, Division of Cardiology, Washington, DC (United States); National Institutes of Health, National Heart, Lung and Blood Institute, Bethesda, MD (United States); Cross, Russell R.; O' Brien, Kendall E. [Children' s National Health System, Division of Cardiology, Washington, DC (United States); Hansen, Michael S. [National Institutes of Health, National Heart, Lung and Blood Institute, Bethesda, MD (United States)

    2015-09-15

    Cardiac magnetic resonance (MR) imaging is a valuable tool in congenital heart disease; however patients frequently have metal devices in the chest from the treatment of their disease that complicate imaging. Methods are needed to improve imaging around metal implants near the heart. Basic sequence parameter manipulations have the potential to minimize artifact while limiting effects on image resolution and quality. Our objective was to design cine and static cardiac imaging sequences to minimize metal artifact while maintaining image quality. Using systematic variation of standard imaging parameters on a fluid-filled phantom containing commonly used metal cardiac devices, we developed optimized sequences for steady-state free precession (SSFP), gradient recalled echo (GRE) cine imaging, and turbo spin-echo (TSE) black-blood imaging. We imaged 17 consecutive patients undergoing routine cardiac MR with 25 metal implants of various origins using both standard and optimized imaging protocols for a given slice position. We rated images for quality and metal artifact size by measuring metal artifact in two orthogonal planes within the image. All metal artifacts were reduced with optimized imaging. The average metal artifact reduction for the optimized SSFP cine was 1.5+/-1.8 mm, and for the optimized GRE cine the reduction was 4.6+/-4.5 mm (P < 0.05). Quality ratings favored the optimized GRE cine. Similarly, the average metal artifact reduction for the optimized TSE images was 1.6+/-1.7 mm (P < 0.05), and quality ratings favored the optimized TSE imaging. Imaging sequences tailored to minimize metal artifact are easily created by modifying basic sequence parameters, and images are superior to standard imaging sequences in both quality and artifact size. Specifically, for optimized cine imaging a GRE sequence should be used with settings that favor short echo time, i.e. flow compensation off, weak asymmetrical echo and a relatively high receiver bandwidth. For static

  3. Correction of ring artifacts in X-ray tomographic images

    DEFF Research Database (Denmark)

    Lyckegaard, Allan; Johnson, G.; Tafforeau, P.

    2011-01-01

    Ring artifacts are systematic intensity distortions located on concentric circles in reconstructed tomographic X-ray images. When using X-ray tomography to study for instance low-contrast grain boundaries in metals it is crucial to correct for the ring artifacts in the images as they may have...... the same intensity level as the grain boundaries and thus make it impossible to perform grain segmentation. This paper describes an implementation of a method for correcting the ring artifacts in tomographic X-ray images of simple objects such as metal samples where the object and the background...... are separable. The method is implemented in Matlab, it works with very little user interaction and may run in parallel on a cluster if applied to a whole stack of images. The strength and robustness of the method implemented will be demonstrated on three tomographic X-ray data sets: a mono-phase β...

  4. Topotactic reduction yielding black titanium oxide nanostructures as metallic electronic conductors.

    Science.gov (United States)

    Tominaka, Satoshi

    2012-10-01

    Detailed analyses of reduced, single crystal, rutile-type TiO(2) via high-resolution transmission electron microscopy (TEM) are reported which reveal that the reduction proceeds topotactically via interstitial diffusion of Ti ions at low temperature, around 350 °C. This important finding encouraged the production of various nanostructured reduced titanium oxides from TiO(2) precursors with morphology retention, and in the process, the synthesis of black titanium oxide nanorods using TiO(2) nanorods was demonstrated. Interestingly, as opposed to the semiconductive behavior of Ti(2)O(3) synthesized at high temperature, topotactically synthesized Ti(2)O(3) exhibits metallic electrical resistance, and the value at room temperature is quite low (topotactically synthesized Ti(2)O(3). This work shows that topotactically reduced titanium oxides can have fascinating properties as well as nanostructures.

  5. Magnesio-thermic reduction of UF4 to uranium metal : plant operating experience

    International Nuclear Information System (INIS)

    Mayekar, S.V.; Singh, H.; Meghal, A.M.; Koppiker, K.S.

    1991-01-01

    Uranium Metal Plant has switched over from calcio-thermy to magnesio-thermy for production of uranium ingots. In this paper, the plant operating experience for magnesio-thermic reduction is described. Based on trials, the production has been stepped up from 40 kg ingots to 200 kg ingots. The operating parameters optimised include : heating schedule, UF 4 quality, magnesium quantity and quality, and particle size. The effect of quality of refractory lining has been discussed. Conditions for lining are optimised with regard to type of material used and size. Developmental work has also been carried out on use of pelletised charge and on use of graphite sleeves. Some experience in the machining of ingots for removal of surface slag is also discussed. Impurity problems, occasionally encountered, have been investigated and results are discussed. Based on the experience gained, specifications for operation have been laid down, and areas for further improvement are identified. (author). 5 refs., 1 fig., 1 tab

  6. Recent Advances in Transition-Metal-Mediated Electrocatalytic CO2 Reduction: From Homogeneous to Heterogeneous Systems

    Directory of Open Access Journals (Sweden)

    Da-Ming Feng

    2017-12-01

    Full Text Available Global climate change and increasing demands for clean energy have brought intensive interest in the search for proper electrocatalysts in order to reduce carbon dioxide (CO2 to higher value carbon products such as hydrocarbons. Recently, transition-metal-centered molecules or organic frameworks have been reported to show outstanding electrocatalytic activity in the liquid phase. Their d-orbital electrons are believed to be one of the key factors to capture and convert CO2 molecules to value-added low-carbon fuels. In this review, recent advances in electrocatalytic CO2 reduction have been summarized based on the targeted products, ranging from homogeneous reactions to heterogeneous ones. Their advantages and fallbacks have been pointed out and the existing challenges, especially with respect to the practical and industrial application are addressed.

  7. Recent Advances in Transition-Metal-Mediated Electrocatalytic CO2 Reduction: From Homogeneous to Heterogeneous Systems

    KAUST Repository

    Feng, Da-Ming

    2017-12-01

    Global climate change and increasing demands for clean energy have brought intensive interest in the search for proper electrocatalysts in order to reduce carbon dioxide (CO2) to higher value carbon products such as hydrocarbons. Recently, transition-metal-centered molecules or organic frameworks have been reported to show outstanding electrocatalytic activity in the liquid phase. Their d-orbital electrons are believed to be one of the key factors to capture and convert CO2 molecules to value-added low-carbon fuels. In this review, recent advances in electrocatalytic CO2 reduction have been summarized based on the targeted products, ranging from homogeneous reactions to heterogeneous ones. Their advantages and fallbacks have been pointed out and the existing challenges, especially with respect to the practical and industrial application are addressed.

  8. Post-harvest processing methods for reduction of silica and alkali metals in wheat straw.

    Science.gov (United States)

    Thompson, David N; Shaw, Peter G; Lacey, Jeffrey A

    2003-01-01

    Silica and alkali metals in wheat straw limit its use for bioenergy and gasification. Slag deposits occur via the eutectic melting of SiO2 with K2O, trapping chlorides at surfaces and causing corrosion. A minimum melting point of 950 degrees C is desirable, corresponding to an SiO2:K2O weight ratio of about 3:1. Mild chemical treatments were used to reduce Si, K, and Cl, while varying temperature, concentration, % solids, and time. Dilute acid was more effective at removing K and Cl, while dilute alkali was more effective for Si. Reduction of minerals in this manner may prove economical for increasing utilization of the straw for combustion or gasification.

  9. Post-Harvest Processing Methods for Reduction of Silica and Alkali Metals in Wheat Straw

    Energy Technology Data Exchange (ETDEWEB)

    Thompson, David Neal; Lacey, Jeffrey Alan; Shaw, Peter Gordon

    2002-04-01

    Silica and alkali metals in wheat straw limit its use for bioenergy and gasification. Slag deposits occur via the eutectic melting of SiO2 with K2O, trapping chlorides at surfaces and causing corrosion. A minimum melting point of 950°C is desirable, corresponding to SiO2:K2O of about 3:1. Mild chemical treatments were used to reduce Si, K, and Cl, while varying temperature, concentration, %-solids, and time. Dilute acid was more effective at removing K and Cl, while dilute alkali was more effective for Si. Reduction of minerals in this manner may prove economical for increasing utilization of the straw for combustion or gasification.

  10. Archaic artifacts resembling celestial spheres

    Science.gov (United States)

    Dimitrakoudis, S.; Papaspyrou, P.; Petoussis, V.; Moussas, X.

    We present several bronze artifacts from the Archaic Age in Greece (750-480 BC) that resemble celestial spheres or forms of other astronomical significance. They are studied in the context of the Dark Age transition from Mycenaean Age astronomical themes to the philosophical and practical revival of astronomy in the Classical Age with its plethora of astronomical devices. These artifacts, mostly votive in nature are spherical in shape and appear in a variety of forms their most striking characteristic being the depiction of meridians and/or an equator. Most of those artifacts come from Thessaly, and more specifically from the temple of Itonia Athena at Philia, a religious center of pan-Hellenic significance. Celestial spheres, similar in form to the small artifacts presented in this study, could be used to measure latitudes, or estimate the time at a known place, and were thus very useful in navigation.

  11. Metal-polypyridyl catalysts for electro- and photochemical reduction of water to hydrogen.

    Science.gov (United States)

    Zee, David Z; Chantarojsiri, Teera; Long, Jeffrey R; Chang, Christopher J

    2015-07-21

    Climate change, rising global energy demand, and energy security concerns motivate research into alternative, sustainable energy sources. In principle, solar energy can meet the world's energy needs, but the intermittent nature of solar illumination means that it is temporally and spatially separated from its consumption. Developing systems that promote solar-to-fuel conversion, such as via reduction of protons to hydrogen, could bridge this production-consumption gap, but this effort requires invention of catalysts that are cheap, robust, and efficient and that use earth-abundant elements. In this context, catalysts that utilize water as both an earth-abundant, environmentally benign substrate and a solvent for proton reduction are highly desirable. This Account summarizes our studies of molecular metal-polypyridyl catalysts for electrochemical and photochemical reduction of protons to hydrogen. Inspired by concept transfer from biological and materials catalysts, these scaffolds are remarkably resistant to decomposition in water, with fast and selective electrocatalytic and photocatalytic conversions that are sustainable for several days. Their modular nature offers a broad range of opportunities for tuning reactivity by molecular design, including altering ancillary ligand electronics, denticity, and/or incorporating redox-active elements. Our first-generation complex, [(PY4)Co(CH3CN)2](2+), catalyzes the reduction of protons from a strong organic acid to hydrogen in 50% water. Subsequent investigations with the pentapyridyl ligand PY5Me2 furnished molybdenum and cobalt complexes capable of catalyzing the reduction of water in fully aqueous electrolyte with 100% Faradaic efficiency. Of particular note, the complex [(PY5Me2)MoO](2+) possesses extremely high activity and durability in neutral water, with turnover frequencies at least 8500 mol of H2 per mole of catalyst per hour and turnover numbers over 600 000 mol of H2 per mole of catalyst over 3 days at an

  12. Heat-resistant organic molecular layer as a joint interface for metal reduction on plastics surfaces

    International Nuclear Information System (INIS)

    Sang, Jing; Aisawa, Sumio; Hirahara, Hidetoshi; Kudo, Takahiro; Mori, Kunio

    2016-01-01

    Graphical abstract: - Highlights: • In situ adsorption behaviors of TES on PA6 surface were clarified by QCM. • Highest adsorption of TES on PA6 was obtained in pH 3 and 0.1 M solution. • Molecular layers of TES with uniform structures were prepared on PA6 surface. • TES layer improved PA6 local heat resistance from 150 °C to 230 °C. • TES molecular layer successfully reduced Ag ion to Ag"0. - Abstract: Heat-resistant organic molecular layers have been fabricated by triazine-based silane coupling agent for metal reduction on plastic surfaces using adsorption method. These molecular layers were used as an interfacial layer between polyamide (PA6) and metal solution to reduce Ag"+ ion to Ag"0. The interfacial behaviors of triazine molecular layer at the interfaces between PA6 and Ag solution were investigated using quartz crystal microbalance (QCM). The kinetics of molecular adsorption on PA6 was investigated by using triazine-based silane coupling agent solutions at different pH and concentration. X-ray photoelectron spectroscopy (XPS), atomic force microscope (AFM), and local nano thermal analysis were employed to characterize the surfaces and interfaces. The nano thermal analysis results show that molecular layers of triazine-based silane coupling agent greatly improved heat resistance of PA6 resin from 170 °C up to 230 °C. This research developed an in-depth insight for molecular behaviors of triazine-based silane coupling agent at the PA6 and Ag solution interfaces and should be of significant value for interfacial research between plastics and metal solution in plating industry.

  13. Heat-resistant organic molecular layer as a joint interface for metal reduction on plastics surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Sang, Jing [Department of Frontier Materials and Function Engineering, Graduate School of Engineering, Iwate University, 4-3-5 Ueda, Morioka 020-8551 (Japan); Aisawa, Sumio, E-mail: aisawa@iwate-u.ac.jp [Department of Frontier Materials and Function Engineering, Graduate School of Engineering, Iwate University, 4-3-5 Ueda, Morioka 020-8551 (Japan); Hirahara, Hidetoshi [Department of Frontier Materials and Function Engineering, Graduate School of Engineering, Iwate University, 4-3-5 Ueda, Morioka 020-8551 (Japan); Kudo, Takahiro [Sulfur Chemical Institute, 210, Collabo MIU, 4-3-5, Ueda, Morioka 020-0066 (Japan); Mori, Kunio [Department of Frontier Materials and Function Engineering, Graduate School of Engineering, Iwate University, 4-3-5 Ueda, Morioka 020-8551 (Japan); Sulfur Chemical Institute, 210, Collabo MIU, 4-3-5, Ueda, Morioka 020-0066 (Japan)

    2016-04-15

    Graphical abstract: - Highlights: • In situ adsorption behaviors of TES on PA6 surface were clarified by QCM. • Highest adsorption of TES on PA6 was obtained in pH 3 and 0.1 M solution. • Molecular layers of TES with uniform structures were prepared on PA6 surface. • TES layer improved PA6 local heat resistance from 150 °C to 230 °C. • TES molecular layer successfully reduced Ag ion to Ag{sup 0}. - Abstract: Heat-resistant organic molecular layers have been fabricated by triazine-based silane coupling agent for metal reduction on plastic surfaces using adsorption method. These molecular layers were used as an interfacial layer between polyamide (PA6) and metal solution to reduce Ag{sup +} ion to Ag{sup 0}. The interfacial behaviors of triazine molecular layer at the interfaces between PA6 and Ag solution were investigated using quartz crystal microbalance (QCM). The kinetics of molecular adsorption on PA6 was investigated by using triazine-based silane coupling agent solutions at different pH and concentration. X-ray photoelectron spectroscopy (XPS), atomic force microscope (AFM), and local nano thermal analysis were employed to characterize the surfaces and interfaces. The nano thermal analysis results show that molecular layers of triazine-based silane coupling agent greatly improved heat resistance of PA6 resin from 170 °C up to 230 °C. This research developed an in-depth insight for molecular behaviors of triazine-based silane coupling agent at the PA6 and Ag solution interfaces and should be of significant value for interfacial research between plastics and metal solution in plating industry.

  14. Inter-deriving Semantic Artifacts for Object-Oriented Programming

    DEFF Research Database (Denmark)

    Danvy, Olivier; Johannsen, Jacob

    2008-01-01

    We present a new abstract machine for Abadi and Cardelli's untyped calculus of objects. What is special about this semantic artifact (i.e., man-made construct) is that is mechanically corresponds to both the reduction semantics (i.e., small-step operational semantics) and the natural semantics (i...... actual substitutions, we then represent object methods as closures and in the same inter-derivational spirit, we present three new semantic artifacts: a reduction semantics for a version of Abadi and Cardelli's untyped calculus of objects with explicit substitutions, an environment-based abstract machine...

  15. Volume reduction of low-level contaminated metal waste by melting: selection of method and conceptual plan

    International Nuclear Information System (INIS)

    Copeland, G.L.; Heestand, R.L.; Mateer, R.S.

    1978-06-01

    A review of the literature and prior experience led to selection of induction melting as the most promising method for volume reduction of low-level transuranic contaminated metal waste. The literature indicates that melting with the appropriate slags significantly lowers the total contamination level of the metals by preferentially concentrating contaminants in the smaller volume of slag. Surface contamination not removed to the slag is diluted in the ingot and is contained uniformly in the metal. This dilution and decontamination offers the potential of lower cost disposal such as shallow burial rather than placement in a national repository. A processing plan is proposed as a model for economic analysis of the collection and volume reduction of contaminated metals. Further development is required to demonstrate feasibility of the plan

  16. NOx reduction over metal-ion exchanged novel zeolite under lean conditions. Activity and hydrothermal stability

    International Nuclear Information System (INIS)

    Subbiah, Ayyappan; Gujar, Amit; Price, Geoffrey L.; Cho, Byong K.; Blint, Richard J.; Yie, Jae E.

    2003-01-01

    Zeolite SUZ-4 was synthesized and tested for its hydrothermal stability using a standard aging procedure coupled with NMR spectroscopy, and was identified as a promising support for lean-NO x catalysts for high temperature applications. Various metals such as Cu, Ag, Fe, Co were ion exchanged onto the SUZ-4 zeolite, and their catalytic activity for NO/NO x conversion was measured in the presence of excess oxygen using ethylene as the reducing agent. Among the metal-ions exchanged, copper proved to be the best metal cation for lean-NO x catalysis with the optimum level of exchange at 29-42%. The optimized, fresh Cu/SUZ-4 catalyst achieved 70-80% of NO/NO x conversion activity over a wide range of temperature from 350 to 600C with the maximum conversion temperature at 450C. The presence of H 2 O and SO 2 reduced the NO/NO x conversion by about 30% of the fresh Cu/SUZ-4 catalyst due possibly to the blocking of active sites for NO/NO x adsorption. Substitution of gasoline vapor for ethylene as the reductant improved the NO x reduction activity of the fresh Cu/SUZ-4 catalyst at high temperatures above 350C. Aging the Cu/SUZ-4 catalyst resulted in a slight shift of activity profile toward higher temperatures, yielding an increase of NO conversion by 16% and a decrease of NO x conversion by 15% at 525C. The effect of H 2 O and SO 2 on the aged catalyst was to reduce the NO activity by 20% and NO x activity by 30% at 500C. The effect of space velocity change was not significant except in the low temperature range where the reaction light-off occurs. Adsorption/desorption measurements indicate that aging Cu/SUZ-4 results in partial migration/agglomeration of Cu particles in the pores thereby reducing the NO/NO x activity. Overall, the NO x conversion efficiency of Cu/SUZ-4, for both fresh and aged, is much better than the benchmark Cu/ZSM-5 in the presence of H 2 O and/or SO 2

  17. Supporting palladium metal on gold nanoparticles improves its catalysis for nitrite reduction.

    Science.gov (United States)

    Qian, Huifeng; Zhao, Zhun; Velazquez, Juan C; Pretzer, Lori A; Heck, Kimberly N; Wong, Michael S

    2014-01-07

    Nitrate (NO3(-)) and nitrite (NO2(-)) anions are often found in groundwater and surface water as contaminants globally, especially in agricultural areas due to nitrate-rich fertilizer use. One popular approach to studying the removal of nitrite/nitrate from water has been their degradation to dinitrogen via Pd-based reduction catalysis. However, little progress has been made towards understanding how the catalyst structure can improve activity. Focusing on the catalytic reduction of nitrite in this study, we report that Au NPs supporting Pd metal ("Pd-on-Au NPs") show catalytic activity that varies with volcano-shape dependence on Pd surface coverage. At room temperature, in CO2-buffered water, and under H2 headspace, the NPs were maximally active at a Pd surface coverage of 80%, with a first-order rate constant (k(cat) = 576 L g(Pd)(-1) min(-1)) that was 15x and 7.5x higher than monometallic Pd NPs (~4 nm; 40 L g(Pd)(-1) min(-1)) and Pd/Al2O3 (1 wt% Pd; 76 L g(Pd)(-1) min(-1)), respectively. Accounting only for surface Pd atoms, these NPs (576 L g(surface-Pd)(-1) min(-1)) were 3.6x and 1.6x higher than monometallic Pd NPs (160 L g(surface-Pd)(-1) min(-1)) and Pd/Al2O3 (361 L g(surface-Pd)(-1) min(-1)). These NPs retained ~98% of catalytic activity at a chloride concentration of 1 mM, whereas Pd/Al2O3 lost ~50%. The Pd-on-Au nanostructure is a promising approach to improve the catalytic reduction process for nitrite and, with further development, also for nitrate anions.

  18. Microbial sulfate reduction and metal attenuation in pH 4 acid mine water

    Directory of Open Access Journals (Sweden)

    Alpers Charles N

    2007-10-01

    Full Text Available Abstract Sediments recovered from the flooded mine workings of the Penn Mine, a Cu-Zn mine abandoned since the early 1960s, were cultured for anaerobic bacteria over a range of pH (4.0 to 7.5. The molecular biology of sediments and cultures was studied to determine whether sulfate-reducing bacteria (SRB were active in moderately acidic conditions present in the underground mine workings. Here we document multiple, independent analyses and show evidence that sulfate reduction and associated metal attenuation are occurring in the pH-4 mine environment. Water-chemistry analyses of the mine water reveal: (1 preferential complexation and precipitation by H2S of Cu and Cd, relative to Zn; (2 stable isotope ratios of 34S/32S and 18O/16O in dissolved SO4 that are 2–3 ‰ heavier in the mine water, relative to those in surface waters; (3 reduction/oxidation conditions and dissolved gas concentrations consistent with conditions to support anaerobic processes such as sulfate reduction. Scanning electron microscope (SEM analyses of sediment show 1.5-micrometer, spherical ZnS precipitates. Phospholipid fatty acid (PLFA and denaturing gradient gel electrophoresis (DGGE analyses of Penn Mine sediment show a high biomass level with a moderately diverse community structure composed primarily of iron- and sulfate-reducing bacteria. Cultures of sediment from the mine produced dissolved sulfide at pH values near 7 and near 4, forming precipitates of either iron sulfide or elemental sulfur. DGGE coupled with sequence and phylogenetic analysis of 16S rDNA gene segments showed populations of Desulfosporosinus and Desulfitobacterium in Penn Mine sediment and laboratory cultures.

  19. Microbial sulfate reduction and metal attenuation in pH 4 acid mine water

    Science.gov (United States)

    Church, C.D.; Wilkin, R.T.; Alpers, Charles N.; Rye, R.O.; Blaine, R.B.

    2007-01-01

    Sediments recovered from the flooded mine workings of the Penn Mine, a Cu-Zn mine abandoned since the early 1960s, were cultured for anaerobic bacteria over a range of pH (4.0 to 7.5). The molecular biology of sediments and cultures was studied to determine whether sulfate-reducing bacteria (SRB) were active in moderately acidic conditions present in the underground mine workings. Here we document multiple, independent analyses and show evidence that sulfate reduction and associated metal attenuation are occurring in the pH-4 mine environment. Water-chemistry analyses of the mine water reveal: (1) preferential complexation and precipitation by H2S of Cu and Cd, relative to Zn; (2) stable isotope ratios of 34S/32S and 18O/16O in dissolved SO4 that are 2-3 ??? heavier in the mine water, relative to those in surface waters; (3) reduction/oxidation conditions and dissolved gas concentrations consistent with conditions to support anaerobic processes such as sulfate reduction. Scanning electron microscope (SEM) analyses of sediment show 1.5-micrometer, spherical ZnS precipitates. Phospholipid fatty acid (PLFA) and denaturing gradient gel electrophoresis (DGGE) analyses of Penn Mine sediment show a high biomass level with a moderately diverse community structure composed primarily of iron- and sulfate-reducing bacteria. Cultures of sediment from the mine produced dissolved sulfide at pH values near 7 and near 4, forming precipitates of either iron sulfide or elemental sulfur. DGGE coupled with sequence and phylogenetic analysis of 16S rDNA gene segments showed populations of Desulfosporosinus and Desulfitobacterium in Penn Mine sediment and laboratory cultures. ?? 2007 Church et al; licensee BioMed Central Ltd.

  20. Reduction of metal exposure of Daubenton's bats (Myotis daubentonii) following remediation of pond sediment as evidenced by metal concentrations in hair.

    Science.gov (United States)

    Flache, Lucie; Ekschmitt, Klemens; Kierdorf, Uwe; Czarnecki, Sezin; Düring, Rolf-Alexander; Encarnação, Jorge A

    2016-03-15

    Transfer of contaminants from freshwater sediments via aquatic insects to terrestrial predators is well documented in spiders and birds. Here, we analyzed the metal exposure of Myotis daubentonii using an urban pond as their preferred foraging area before and after a remediation measure (sediment dredging) at this pond. Six metal elements (Zn, Cu, Cr, Cd, Pb and Ni) were measured in the sediment of the pond, in EDTA extracts of the sediment and in hair samples of M. daubentonii foraging at the pond. Samples were taken before remediation in 2011 and after remediation in 2013. Metal concentrations were quantified by ICP-OES after miniaturized microwave assisted extraction. In 2011, the pond sediment exhibited a high contamination with nickel, a moderate contamination with copper and chromium and low contents of zinc, cadmium and lead. While sediment metal contents declined only weakly after remediation, a much more pronounced reduction in the concentrations of zinc, copper, chromium and lead concentrations was observed in bat hair. Our results suggest a marked decline in metal exposure of the bats foraging at the pond as a consequence of the remediation measure. It is concluded that Daubenton's bats are suitable bioindicators of metal contamination in aquatic environments, integrating metal exposure via prey insects over their entire foraging area. We further suggest that bat hair is a useful monitoring unit, allowing a non-destructive and non-invasive assessment of metal exposure in bats. Copyright © 2015 Elsevier B.V. All rights reserved.

  1. Hydrazine reduction of metal ions to porous submicro-structures of Ag, Pd, Cu, Ni, and Bi

    Energy Technology Data Exchange (ETDEWEB)

    Wang Yue; Shi Yongfang; Chen Yubiao [State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002 (China); Wu Liming, E-mail: liming_wu@fjirsm.ac.cn [State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002 (China)

    2012-07-15

    Porous submicro-structures of Ag, Pd, Cu, Ni, and Bi with high surface area have been prepared by the reduction of hydrazine in glycerol-ethanol solution at room temperature or 120-180 Degree-Sign C. Phase purity, morphology, and specific surface area have been characterized. The reactions probably undergo three different mechanisms: simple reduction for Ag and Pd, coordination-then-reduction for Cu and Ni, and hydrolysis-then-reduction for Bi. The reductant hydrazine also plays an important role to the formation of the porous submicro-structure. The reaction temperature influences the size of the constituent particles and the overall architecture of the submicro-structure so as to influence the surface area value. The as-prepared porous metals have shown the second largest surface area ever reported, which are smaller than those made by the reduction of NaBH{sub 4}, but larger than those made by hard or soft template methods. - Graphical abstract: Porous submicro-structures of Ag, Pd, Cu, Ni, and Bi with high surface area have been prepared by the reduction of hydrazine in the glycerol-ethanol solution at room temperature or 120-180 Degree-Sign C. The reactions undergo different mechanisms: simple reduction for Ag and Pd, coordination-then-reduction for Cu and Ni, and hydrolysis-then-reduction for Bi. Highlights: Black-Right-Pointing-Pointer Syntheses of porous Ag, Pd, Cu, Ni, and Bi with high surface area. Black-Right-Pointing-Pointer Ag and Pd undergo simple reduction. Black-Right-Pointing-Pointer Cu and Ni undergo coordination-then-reduction. Black-Right-Pointing-Pointer Bi undergoes hydrolysis-then-reduction. Black-Right-Pointing-Pointer The as-prepared metals have shown the second largest surface area ever reported.

  2. Transition Metal Oxides for the Oxygen Reduction Reaction: Influence of the Oxidation States of the Metal and its Position on the Periodic Table.

    Science.gov (United States)

    Toh, Rou Jun; Sofer, Zdeněk; Pumera, Martin

    2015-11-16

    Electrocatalysts have been developed to meet the needs and requirements of renewable energy applications. Metal oxides have been well explored and are promising for this purpose, however, many reports focus on only one or a few metal oxides at once. Herein, thirty metal oxides, which were either commercially available or synthesized by a simple and scalable method, were screened for comparison with regards to their electrocatalytic activity towards the oxygen reduction reaction (ORR). We show that although manganese, iron, cobalt, and nickel oxides generally displayed the ability to enhance the kinetics of oxygen reduction under alkaline conditions compared with bare glassy carbon, there is no significant correlation between the position of a metal on the periodic table and the electrocatalytic performance of its respective metal oxides. Moreover, it was also observed that mixed valent (+2, +3) oxides performed the poorest, compared with their respective pure metal oxides. These findings may be of paramount importance in the field of renewable energy. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Graphene hydrogels with embedded metal nanoparticles as efficient catalysts in 4-nitrophenol reduction and methylene blue decolorization

    Directory of Open Access Journals (Sweden)

    Żelechowska Kamila

    2016-12-01

    Full Text Available Synthesis and characterization of the graphene hydrogels with three different metallic nanoparticles, that is Au, Ag and Cu, respectively is presented. Synthesized in a one-pot approach graphene hydrogels with embedded metallic nanoparticles were tested as heterogeneous catalysts in a model reaction of 4-nitrophenol reduction. The highest activity was obtained for graphene hydrogel with Cu nanoparticles and additional reaction of methylene blued degradation was evaluated using this system. The obtained outstanding catalytic activity arises from the synergistic effect of graphene and metallic nanoparticles. The hydrogel form of the catalyst benefits in the easiness in separation from the reaction mixture (for example using tweezers and reusability.

  4. From melamine sponge towards 3D sulfur-doping carbon nitride as metal-free electrocatalysts for oxygen reduction reaction

    Science.gov (United States)

    Xu, Jingjing; Li, Bin; Li, Songmei; Liu, Jianhua

    2017-07-01

    Development of new and efficient metal-free electrocatalysts for replacing Pt to improve the sluggish kinetics of oxygen reduction reaction (ORR) is of great importance to emerging renewable energy technologies such as metal-air batteries and polymer electrolyte fuel cells. Herein, 3D sulfur-doping carbon nitride (S-CN) as a novel metal-free ORR electrocatalyst was synthesized by exploiting commercial melamine sponge as raw material. The sulfur atoms were doping on CN networks uniformly through numerous S-C bonds which can provide additional active sites. And it was found that the S-CN exhibited high catalytic activity for ORR in term of more positive onset potential, higher electron transfer number and higher cathodic density. This work provides a novel choice of metal-free ORR electrocatalysts and highlights the importance of sulfur-doping CN in metal-free ORR electrocatalysts.

  5. Sequential separation of transuranic elements and fission products from uranium metal ingots in electrolytic reduction process of spent PWR fuels

    International Nuclear Information System (INIS)

    Chang Heon Lee; Kih Soo Joe; Won Ho Kim; Euo Chang Jung; Kwang Yong Jee

    2009-01-01

    A sequential separation procedure has been developed for the determination of transuranic elements and fission products in uranium metal ingot samples from an electrolytic reduction process for a metallization of uranium dioxide to uranium metal in a medium of LiCl-Li 2 O molten salt at 650 deg C. Pu, Np and U were separated using anion-exchange and tri-n-butylphosphate (TBP) extraction chromatography. Cs, Sr, Ba, Ce, Pr, Nd, Sm, Eu, Gd, Zr and Mo were separated in several groups from Am and Cm using TBP and di(2-ethylhexyl)phosphoric acid (HDEHP) extraction chromatography. Effect of Fe, Ni, Cr and Mg, which were corrosion products formed through the process, on the separation of the analytes was investigated in detail. The validity of the separation procedure was evaluated by measuring the recovery of the stable metals and 239 Pu, 237 Np, 241 Am and 244 Cm added to a synthetic uranium metal ingot dissolved solution. (author)

  6. Efficient selective catalytic reduction of NO by novel carbon-doped metal catalysts made from electroplating sludge.

    Science.gov (United States)

    Zhang, Jia; Zhang, Jingyi; Xu, Yunfeng; Su, Huimin; Li, Xiaoman; Zhou, Ji Zhi; Qian, Guangren; Li, Li; Xu, Zhi Ping

    2014-10-07

    Electroplating sludges, once regarded as industrial wastes, are precious resources of various transition metals. This research has thus investigated the recycling of an electroplating sludge as a novel carbon-doped metal (Fe, Ni, Mg, Cu, and Zn) catalyst, which was different from a traditional carbon-supported metal catalyst, for effective NO selective catalytic reduction (SCR). This catalyst removed >99.7% NO at a temperature as low as 300 °C. It also removed NO steadily (>99%) with a maximum specific accumulative reduced amount (MSARA) of 3.4 mmol/g. Gas species analyses showed that NO removal was accompanied by evolving N2 and CO2. Moreover, in a wide temperature window, the sludge catalyst showed a higher CO2 selectivity (>99%) than an activated carbon-supported metal catalyst. Structure characterizations revealed that carbon-doped metal was transformed to metal oxide in the sludge catalyst after the catalytic test, with most carbon (2.33 wt %) being consumed. These observations suggest that NO removal over the sludge catalyst is a typical SCR where metals/metal oxides act as the catalytic center and carbon as the reducing reagent. Therefore, our report probably provides an opportunity for high value-added utilizations of heavy-metal wastes in mitigating atmospheric pollutions.

  7. Correction of Bowtie-Filter Normalization and Crescent Artifacts for a Clinical CBCT System.

    Science.gov (United States)

    Zhang, Hong; Kong, Vic; Huang, Ke; Jin, Jian-Yue

    2017-02-01

    To present our experiences in understanding and minimizing bowtie-filter crescent artifacts and bowtie-filter normalization artifacts in a clinical cone beam computed tomography system. Bowtie-filter position and profile variations during gantry rotation were studied. Two previously proposed strategies (A and B) were applied to the clinical cone beam computed tomography system to correct bowtie-filter crescent artifacts. Physical calibration and analytical approaches were used to minimize the norm phantom misalignment and to correct for bowtie-filter normalization artifacts. A combined procedure to reduce bowtie-filter crescent artifacts and bowtie-filter normalization artifacts was proposed and tested on a norm phantom, CatPhan, and a patient and evaluated using standard deviation of Hounsfield unit along a sampling line. The bowtie-filter exhibited not only a translational shift but also an amplitude variation in its projection profile during gantry rotation. Strategy B was better than strategy A slightly in minimizing bowtie-filter crescent artifacts, possibly because it corrected the amplitude variation, suggesting that the amplitude variation plays a role in bowtie-filter crescent artifacts. The physical calibration largely reduced the misalignment-induced bowtie-filter normalization artifacts, and the analytical approach further reduced bowtie-filter normalization artifacts. The combined procedure minimized both bowtie-filter crescent artifacts and bowtie-filter normalization artifacts, with Hounsfield unit standard deviation being 63.2, 45.0, 35.0, and 18.8 Hounsfield unit for the best correction approaches of none, bowtie-filter crescent artifacts, bowtie-filter normalization artifacts, and bowtie-filter normalization artifacts + bowtie-filter crescent artifacts, respectively. The combined procedure also demonstrated reduction of bowtie-filter crescent artifacts and bowtie-filter normalization artifacts in a CatPhan and a patient. We have developed a step

  8. Metaproteomics Identifies the Protein Machinery Involved in Metal and Radionuclide Reduction in Subsurface Microbiomes and Elucidates Mechanisms and U(VI) Reduction Immobilization

    Energy Technology Data Exchange (ETDEWEB)

    Pfiffner, Susan M. [Univ. of Tennessee, Knoxville, TN (United States); Löffler, Frank [Univ. of Tennessee, Knoxville, TN (United States); Ritalahti, Kirsti [Univ. of Tennessee, Knoxville, TN (United States); Sayler, Gary [Univ. of Tennessee, Knoxville, TN (United States); Layton, Alice [Univ. of Tennessee, Knoxville, TN (United States); Hettich, Robert [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2015-08-31

    The overall goal for this funded project was to develop and exploit environmental metaproteomics tools to identify biomarkers for monitoring microbial activity affecting U speciation at U-contaminated sites, correlate metaproteomics profiles with geochemical parameters and U(VI) reduction activity (or lack thereof), elucidate mechanisms contributing to U(VI) reduction, and provide remediation project managers with additional information to make science-based site management decisions for achieving cleanup goals more efficiently. Although significant progress has been made in elucidating the microbiology contribution to metal and radionuclide reduction, the cellular components, pathway(s), and mechanisms involved in U trans-formation remain poorly understood. Recent advances in (meta)proteomics technology enable detailed studies of complex samples, including environmental samples, which differ between sites and even show considerable variability within the same site (e.g., the Oak Ridge IFRC site). Additionally, site-specific geochemical conditions affect microbial activity and function, suggesting generalized assessment and interpretations may not suffice. This research effort integrated current understanding of the microbiology and biochemistry of U(VI) reduction and capitalize on advances in proteomics technology made over the past few years. Field-related analyses used Oak Ridge IFRC field ground water samples from locations where slow-release substrate biostimulation has been implemented to accelerate in situ U(VI) reduction rates. Our overarching hypothesis was that the metabolic signature in environmental samples, as deciphered by the metaproteome measurements, would show a relationship with U(VI) reduction activity. Since metaproteomic and metagenomic characterizations were computationally challenging and time-consuming, we used a tiered approach that combines database mining, controlled laboratory studies, U(VI) reduction activity measurements, phylogenetic

  9. Four-electron deoxygenative reductive coupling of carbon monoxide at a single metal site

    Science.gov (United States)

    Buss, Joshua A.; Agapie, Theodor

    2016-01-01

    Carbon dioxide is the ultimate source of the fossil fuels that are both central to modern life and problematic: their use increases atmospheric levels of greenhouse gases, and their availability is geopolitically constrained. Using carbon dioxide as a feedstock to produce synthetic fuels might, in principle, alleviate these concerns. Although many homogeneous and heterogeneous catalysts convert carbon dioxide to carbon monoxide, further deoxygenative coupling of carbon monoxide to generate useful multicarbon products is challenging. Molybdenum and vanadium nitrogenases are capable of converting carbon monoxide into hydrocarbons under mild conditions, using discrete electron and proton sources. Electrocatalytic reduction of carbon monoxide on copper catalysts also uses a combination of electrons and protons, while the industrial Fischer-Tropsch process uses dihydrogen as a combined source of electrons and electrophiles for carbon monoxide coupling at high temperatures and pressures. However, these enzymatic and heterogeneous systems are difficult to probe mechanistically. Molecular catalysts have been studied extensively to investigate the elementary steps by which carbon monoxide is deoxygenated and coupled, but a single metal site that can efficiently induce the required scission of carbon-oxygen bonds and generate carbon-carbon bonds has not yet been documented. Here we describe a molybdenum compound, supported by a terphenyl-diphosphine ligand, that activates and cleaves the strong carbon-oxygen bond of carbon monoxide, enacts carbon-carbon coupling, and spontaneously dissociates the resulting fragment. This complex four-electron transformation is enabled by the terphenyl-diphosphine ligand, which acts as an electron reservoir and exhibits the coordinative flexibility needed to stabilize the different intermediates involved in the overall reaction sequence. We anticipate that these design elements might help in the development of efficient catalysts for

  10. Reduction of metal exposure of Daubenton's bats (Myotis daubentonii) following remediation of pond sediment as evidenced by metal concentrations in hair

    Energy Technology Data Exchange (ETDEWEB)

    Flache, Lucie, E-mail: Lucie.Flache@bio.uni-giessen.de [Mammalian Ecology Group, Department of Animal Ecology and Systematics, Justus Liebig University of Giessen, Heinrich-Buff-Ring 26, D-35392 Giessen (Germany); Ekschmitt, Klemens [Animal Ecology, Department of Animal Ecology and Systematics, Justus Liebig University of Giessen, Heinrich-Buff-Ring 26, D-35392 Giessen (Germany); Kierdorf, Uwe [Department of Biology, University of Hildesheim, Universitätsplatz 1, D-31141 Hildesheim (Germany); Czarnecki, Sezin; Düring, Rolf-Alexander [Institute of Soil Science and Soil Conservation, Justus Liebig University of Giessen, Heinrich-Buff-Ring 26, D-35392 Giessen (Germany); Encarnação, Jorge A. [Mammalian Ecology Group, Department of Animal Ecology and Systematics, Justus Liebig University of Giessen, Heinrich-Buff-Ring 26, D-35392 Giessen (Germany)

    2016-03-15

    Transfer of contaminants from freshwater sediments via aquatic insects to terrestrial predators is well documented in spiders and birds. Here, we analyzed the metal exposure of Myotis daubentonii using an urban pond as their preferred foraging area before and after a remediation measure (sediment dredging) at this pond. Six metal elements (Zn, Cu, Cr, Cd, Pb and Ni) were measured in the sediment of the pond, in EDTA extracts of the sediment and in hair samples of M. daubentonii foraging at the pond. Samples were taken before remediation in 2011 and after remediation in 2013. Metal concentrations were quantified by ICP-OES after miniaturized microwave assisted extraction. In 2011, the pond sediment exhibited a high contamination with nickel, a moderate contamination with copper and chromium and low contents of zinc, cadmium and lead. While sediment metal contents declined only weakly after remediation, a much more pronounced reduction in the concentrations of zinc, copper, chromium and lead concentrations was observed in bat hair. Our results suggest a marked decline in metal exposure of the bats foraging at the pond as a consequence of the remediation measure. It is concluded that Daubenton's bats are suitable bioindicators of metal contamination in aquatic environments, integrating metal exposure via prey insects over their entire foraging area. We further suggest that bat hair is a useful monitoring unit, allowing a non-destructive and non-invasive assessment of metal exposure in bats. - Highlights: • Changes in metal exposure of bats due to remediation measure are documented. • Bats are suitable bioindicators of metal pollution. • Bat hair is a useful monitoring unit in such studies.

  11. Reduction of metal exposure of Daubenton's bats (Myotis daubentonii) following remediation of pond sediment as evidenced by metal concentrations in hair

    International Nuclear Information System (INIS)

    Flache, Lucie; Ekschmitt, Klemens; Kierdorf, Uwe; Czarnecki, Sezin; Düring, Rolf-Alexander; Encarnação, Jorge A.

    2016-01-01

    Transfer of contaminants from freshwater sediments via aquatic insects to terrestrial predators is well documented in spiders and birds. Here, we analyzed the metal exposure of Myotis daubentonii using an urban pond as their preferred foraging area before and after a remediation measure (sediment dredging) at this pond. Six metal elements (Zn, Cu, Cr, Cd, Pb and Ni) were measured in the sediment of the pond, in EDTA extracts of the sediment and in hair samples of M. daubentonii foraging at the pond. Samples were taken before remediation in 2011 and after remediation in 2013. Metal concentrations were quantified by ICP-OES after miniaturized microwave assisted extraction. In 2011, the pond sediment exhibited a high contamination with nickel, a moderate contamination with copper and chromium and low contents of zinc, cadmium and lead. While sediment metal contents declined only weakly after remediation, a much more pronounced reduction in the concentrations of zinc, copper, chromium and lead concentrations was observed in bat hair. Our results suggest a marked decline in metal exposure of the bats foraging at the pond as a consequence of the remediation measure. It is concluded that Daubenton's bats are suitable bioindicators of metal contamination in aquatic environments, integrating metal exposure via prey insects over their entire foraging area. We further suggest that bat hair is a useful monitoring unit, allowing a non-destructive and non-invasive assessment of metal exposure in bats. - Highlights: • Changes in metal exposure of bats due to remediation measure are documented. • Bats are suitable bioindicators of metal pollution. • Bat hair is a useful monitoring unit in such studies.

  12. Periplasmic Cytochrome c(3) of Desulfovibrio vulgaris Is Directly Involved in H2-Mediated Metal but Not Sulfate Reduction

    International Nuclear Information System (INIS)

    Elias, Dwayne A.; Suflita, Joseph M.; McInerney, Michael J.; Krumholz, Lee R.

    2004-01-01

    Kinetic parameters and the role of cytochrome c3 in sulfate, Fe(III), and U(VI) reduction were investigated in Desulfovibrio vulgaris Hildenborough. While sulfate reduction followed Michaelis-Menten kinetics (Km 220 uM), loss of Fe(III) and U(VI) was first-order at all concentrations tested. Initial reduction rates of all electron acceptors were similar for cells grown with H2 and sulfate, while cultures grown using lactate and sulfate had similar rates of metal loss but lower sulfate reduction activities. The similarities in metal, but not sulfate, reduction with H2 and lactate suggest divergent pathways. Respiration assays and reduced minus oxidized spectra were carried out to determine c-type cytochrome involvement in electron acceptor reduction. c-type cytochrome oxidation was immediate with Fe(III) and U(VI) in the presence of H2, lactate, or pyruvate. Sulfidogenesis occurred with all three electron donors and effectively oxidized the c-type cytochrome in lactate or pyruvate-reduced, but not H2-reduced cells. Correspondingly, electron acceptor competition assays with lactate or pyruvate as electron donors showed that Fe(III) inhibited U(VI) reduction, and U(VI) inhibited sulfate loss. However, sulfate reduction was slowed but not halted when H2 was the electron donor in the presence of Fe(III) or U(VI). U(VI) loss was still impeded by Fe(III) when H2 was used. Hence, we propose a modified pathway for the reduction of sulfate, Fe(III), and U(VI) which helps explain why these bacteria cannot grow using these metals. We further propose that cytochrome c3 is an electron carrier involved in lactate and pyruvate oxidation and is the reductase for alternate electron acceptors with higher redox potentials than sulfate

  13. A study on the reduction of uranium oxide to uranium metal in LiCl molten salt

    International Nuclear Information System (INIS)

    Seo, J. S.; Hur, J. M.; Lee, W. K.; Hong, S. S.; Kang, D. S.; Park, S. W.

    2002-01-01

    Research for the analysis on a metallization process of uranium oxide in LiCl-Li molten salt was carried out. Effect of a concentration of Li 2 O on the metallization process was also studied. The new concept, electrochemical reduction of uranium oxide in LiCl-Li 2 O molten salt was proposed. The concept is based on the integrated process of metallization of UO 2 with simultaneous electrochemical reduction of Li 2 O which is recycled in a closed system. In a LiCl-Li molten salt system, U 3 O 8 whose conversion ratio to U turns out to be 97.1%, showed a better metallization characteristic than UO 2 . It is verified that electrochemically reduced Li is well deposited on the UO 2 powder cathode through a porous magnesia filter in LiCl-Li 2 O molten salt. In that process Li 2 O was from by the reduction process of UO 2 to U. This electrochemical reduction process showed good results to covert UO 2 to U

  14. Extracellular Saccharide-Mediated Reduction of Au3+ to Gold Nanoparticles: New Insights for Heavy Metals Biomineralization on Microbial Surfaces.

    Science.gov (United States)

    Kang, Fuxing; Qu, Xiaolei; Alvarez, Pedro J J; Zhu, Dongqiang

    2017-03-07

    Biomineralization is a critical process controlling the biogeochemical cycling, fate, and potential environmental impacts of heavy metals. Despite the indispensability of extracellular polymeric substances (EPS) to microbial life and their ubiquity in soil and aquatic environments, the role played by EPS in the transformation and biomineralization of heavy metals is not well understood. Here, we used gold ion (Au 3+ ) as a model heavy metal ion to quantitatively assess the role of EPS in biomineralization and discern the responsible functional groups. Integrated spectroscopic analyses showed that Au 3+ was readily reduced to zerovalent gold nanoparticles (AuNPs, 2-15 nm in size) in aqueous suspension of Escherichia coli or dissolved EPS extracted from microbes. The majority of AuNPs (95.2%) was formed outside Escherichia coli cells, and the removal of EPS attached to cells pronouncedly suppressed Au 3+ reduction, reflecting the predominance of the extracellular matrix in Au 3+ reduction. XPS, UV-vis, and FTIR analyses corroborated that Au 3+ reduction was mediated by the hemiacetal groups (aldehyde equivalents) of reducing saccharides of EPS. Consistently, the kinetics of AuNP formation obeyed pseudo-second-order reaction kinetics with respect to the concentrations of Au 3+ and the hemiacetal groups in EPS, with minimal dependency on the source of microbial EPS. Our findings indicate a previously overlooked, universally significant contribution of EPS to the reduction, mineralization, and potential detoxification of metal species with high oxidation state.

  15. Synthesis of 2-Alkenylquinoline by Reductive Olefination of Quinoline N-Oxide under Metal-Free Conditions.

    Science.gov (United States)

    Xia, Hong; Liu, Yuanhong; Zhao, Peng; Gou, Shaohua; Wang, Jun

    2016-04-15

    Synthesis of 2-alkenylquinoline by reductive olefination of quinoline N-oxide under metal-free conditions is disclosed. Practically, the reaction could be performed with quinoline as starting material via a one-pot, two-step process. A possible mechanism is proposed that involves a sequential 1,3-dipolar cycloaddition and acid-assisted ring opening followed by a dehydration process.

  16. In-situ metal precipitation in a zinc-aerobic, sandy aquifer by means of biological sulfate reduction

    NARCIS (Netherlands)

    Janssen, G.M.C.M.; Temminghoff, E.J.M.

    2004-01-01

    The applicability of in situ metal precipitation (ISMP) based on bacterial sulfate reduction (BSR) with molasses as carbon source was tested for the immobilization of a zinc plume in an aquifer with highly unsuitable initial conditions (high Eh, low pH, low organic matter content, and low sulfate

  17. Prototype metal artefact reduction algorithm in flat panel computed tomography - evaluation in patients undergoing transarterial hepatic radioembolisation

    International Nuclear Information System (INIS)

    Hamie, Qeumars Mustafa; Kobe, Adrian Raoul; Mietzsch, Leif; Puippe, Gilbert Dominique; Pfammatter, Thomas; Guggenberger, Roman; Manhart, Michael

    2018-01-01

    To investigate the effect of an on-site prototype metal artefact reduction (MAR) algorithm in cone-beam CT-catheter-arteriography (CBCT-CA) in patients undergoing transarterial radioembolisation (RE) of hepatic masses. Ethical board approved retrospective study of 29 patients (mean 63.7±13.7 years, 11 female), including 16 patients with arterial metallic coils, undergoing CBCT-CA (8s scan, 200 degrees rotation, 397 projections). Image reconstructions with and without prototype MAR algorithm were evaluated quantitatively (streak-artefact attenuation changes) and qualitatively (visibility of hepatic parenchyma and vessels) in near- (<1cm) and far-field (>3cm) of artefact sources (metallic coils and catheters). Quantitative and qualitative measurements of uncorrected and MAR corrected images and different artefact sources were compared Quantitative evaluation showed significant reduction of near- and far-field streak-artefacts with MAR for both artefact sources (p<0.001), while remaining stable for unaffected organs (all p>0.05). Inhomogeneities of attenuation values were significantly higher for metallic coils compared to catheters (p<0.001) and decreased significantly for both after MAR (p<0.001). Qualitative image scores were significantly improved after MAR (all p<0.003) with by trend higher artefact degrees for metallic coils compared to catheters. In patients undergoing CBCT-CA for transarterial RE, prototype MAR algorithm improves image quality in proximity of metallic coil and catheter artefacts. (orig.)

  18. Separation and Recovery of Uranium Metal from Spent Light Water Reactor Fuel via Electrolytic Reduction and Electrorefining

    International Nuclear Information System (INIS)

    Herrmann, S.D.; Li, S.X.

    2010-01-01

    A series of bench-scale experiments was performed in a hot cell at Idaho National Laboratory to demonstrate the separation and recovery of uranium metal from spent light water reactor (LWR) oxide fuel. The experiments involved crushing spent LWR fuel to particulate and separating it from its cladding. Oxide fuel particulate was then converted to metal in a series of six electrolytic reduction runs that were performed in succession with a single salt loading of molten LiCl - 1 wt% Li2O at 650 C. Analysis of salt samples following the series of electrolytic reduction runs identified the diffusion of select fission products from the spent fuel to the molten salt electrolyte. The extents of metal oxide conversion in the post-test fuel were also quantified, including a nominal 99.7% conversion of uranium oxide to metal. Uranium metal was then separated from the reduced LWR fuel in a series of six electrorefining runs that were performed in succession with a single salt loading of molten LiCl-KCl-UCl3 at 500 C. Analysis of salt samples following the series of electrorefining runs identified additional partitioning of fission products into the molten salt electrolyte. Analyses of the separated uranium metal were performed, and its decontamination factors were determined.

  19. Prototype metal artefact reduction algorithm in flat panel computed tomography - evaluation in patients undergoing transarterial hepatic radioembolisation

    Energy Technology Data Exchange (ETDEWEB)

    Hamie, Qeumars Mustafa; Kobe, Adrian Raoul; Mietzsch, Leif; Puippe, Gilbert Dominique; Pfammatter, Thomas; Guggenberger, Roman [University Hospital Zurich, Department of Radiology, Zurich (Switzerland); Manhart, Michael [Imaging Concepts, HC AT IN IMC, Siemens Healthcare GmbH, Advanced Therapies, Innovation, Forchheim (Germany)

    2018-01-15

    To investigate the effect of an on-site prototype metal artefact reduction (MAR) algorithm in cone-beam CT-catheter-arteriography (CBCT-CA) in patients undergoing transarterial radioembolisation (RE) of hepatic masses. Ethical board approved retrospective study of 29 patients (mean 63.7±13.7 years, 11 female), including 16 patients with arterial metallic coils, undergoing CBCT-CA (8s scan, 200 degrees rotation, 397 projections). Image reconstructions with and without prototype MAR algorithm were evaluated quantitatively (streak-artefact attenuation changes) and qualitatively (visibility of hepatic parenchyma and vessels) in near- (<1cm) and far-field (>3cm) of artefact sources (metallic coils and catheters). Quantitative and qualitative measurements of uncorrected and MAR corrected images and different artefact sources were compared Quantitative evaluation showed significant reduction of near- and far-field streak-artefacts with MAR for both artefact sources (p<0.001), while remaining stable for unaffected organs (all p>0.05). Inhomogeneities of attenuation values were significantly higher for metallic coils compared to catheters (p<0.001) and decreased significantly for both after MAR (p<0.001). Qualitative image scores were significantly improved after MAR (all p<0.003) with by trend higher artefact degrees for metallic coils compared to catheters. In patients undergoing CBCT-CA for transarterial RE, prototype MAR algorithm improves image quality in proximity of metallic coil and catheter artefacts. (orig.)

  20. One-step aqueous synthesis of fluorescent copper nanoclusters by direct metal reduction

    International Nuclear Information System (INIS)

    Fernández-Ujados, Mónica; Trapiella-Alfonso, Laura; Costa-Fernández, José M; Pereiro, Rosario; Sanz-Medel, Alfredo

    2013-01-01

    A one-step aqueous synthesis of highly fluorescent water-soluble copper nanoclusters (CuNCs) is here described, based on direct reduction of the metal precursor with NaBH 4 in the presence of bidentate ligands (made of lipoic acid anchoring groups, appended with a poly(ethylene glycol) short chain). A complete optical and structural characterization was carried out: the optical emission was centred at 416 nm, with a luminescence quantum yield in water of 3.6% (the highest one reported so far in water for this kind of nanocluster). The structural characterization reveals a homogeneous size distribution (of 2.5 nm diameter) with spherical shape. The CuNCs obtained offer long-term stability (the luminescence emission remained unaltered after more than two months) under a broad range of chemical conditions (e.g. stored at pH 3–12 or even in a high ionic strength medium such as 1 M NaCl) and high photostability, keeping their fluorescence emission intact after more than 2 h of daylight and UV-light exposition. All those advantageous features warrant synthesized CuNCs being promising fluorescent nanoprobes for further developments including (bio)applications. (paper)

  1. Reflection-artifact-free photoacoustic imaging using PAFUSion (photoacoustic-guided focused ultrasound)

    Science.gov (United States)

    Kuniyil Ajith Singh, Mithun; Jaeger, Michael; Frenz, Martin; Steenbergen, Wiendelt

    2016-03-01

    Reflection artifacts caused by acoustic inhomogeneities are a main challenge to deep-tissue photoacoustic imaging. Photoacoustic transients generated by the skin surface and superficial vasculature will propagate into the tissue and reflect back from echogenic structures to generate reflection artifacts. These artifacts can cause problems in image interpretation and limit imaging depth. In its basic version, PAFUSion mimics the inward travelling wave-field from blood vessel-like PA sources by applying focused ultrasound pulses, and thus provides a way to identify reflection artifacts. In this work, we demonstrate reflection artifact correction in addition to identification, towards obtaining an artifact-free photoacoustic image. In view of clinical applications, we implemented an improved version of PAFUSion in which photoacoustic data is backpropagated to imitate the inward travelling wave-field and thus the reflection artifacts of a more arbitrary distribution of PA sources that also includes the skin melanin layer. The backpropagation is performed in a synthetic way based on the pulse-echo acquisitions after transmission on each single element of the transducer array. We present a phantom experiment and initial in vivo measurements on human volunteers where we demonstrate significant reflection artifact reduction using our technique. The results provide a direct confirmation that reflection artifacts are prominent in clinical epi-photoacoustic imaging, and that PAFUSion can reduce these artifacts significantly to improve the deep-tissue photoacoustic imaging.

  2. Reduction of heavy metals in residues from the dismantling of waste electrical and electronic equipment before incineration

    International Nuclear Information System (INIS)

    Long, Yu-Yang; Feng, Yi-Jian; Cai, Si-Shi; Hu, Li-Fang; Shen, Dong-Sheng

    2014-01-01

    Highlights: • The highest metal reduction occurs at a 2.36 mm sieving size. • Washing promotes heavy metal recycling without secondary pollution. • Sieving and washing are environmentally friendly pretreatments for WEEE wastes. - Abstract: Residues disposal from the dismantling of waste electrical and electronic equipment are challenging because of the large waste volumes, degradation-resistance, low density and high heavy metal content. Incineration is advantageous for treating these residues but high heavy metal contents may exist in incinerator input and output streams. We have developed and studied a specialized heavy metal reduction process, which includes sieving and washing for treating residues before incineration. The preferable screen aperture for sieving was found to be 2.36 mm (8 meshes) in this study; using this screen aperture resulted in the removal of approximately 47.2% Cu, 65.9% Zn, 26.5% Pb, 55.4% Ni and 58.8% Cd from the residues. Subsequent washing further reduces the heavy metal content in the residues larger than 2.36 mm, with preferable conditions being 400 rpm rotation speed, 5 min washing duration and liquid-to-solid ratio of 25:1. The highest cumulative removal efficiencies of Cu, Zn, Pb, Ni and Cd after sieving and washing reached 81.1%, 61.4%, 75.8%, 97.2% and 72.7%, respectively. The combined sieving and washing process is environmentally friendly, can be used for the removal of heavy metals from the residues and has benefits in terms of heavy metal recycling

  3. Reduction of heavy metals in residues from the dismantling of waste electrical and electronic equipment before incineration

    Energy Technology Data Exchange (ETDEWEB)

    Long, Yu-Yang; Feng, Yi-Jian; Cai, Si-Shi [Zhejiang Provincial Key Laboratory of Solid Waste Treatment and Recycling, School of Environmental Science and Engineering, Zhejiang Gongshang University, Hangzhou 310012 (China); Hu, Li-Fang [College of Quality and Safety Engineering, China Jiliang University, Hangzhou 310018 (China); Shen, Dong-Sheng, E-mail: shends@zju.edu.cn [Zhejiang Provincial Key Laboratory of Solid Waste Treatment and Recycling, School of Environmental Science and Engineering, Zhejiang Gongshang University, Hangzhou 310012 (China)

    2014-05-01

    Highlights: • The highest metal reduction occurs at a 2.36 mm sieving size. • Washing promotes heavy metal recycling without secondary pollution. • Sieving and washing are environmentally friendly pretreatments for WEEE wastes. - Abstract: Residues disposal from the dismantling of waste electrical and electronic equipment are challenging because of the large waste volumes, degradation-resistance, low density and high heavy metal content. Incineration is advantageous for treating these residues but high heavy metal contents may exist in incinerator input and output streams. We have developed and studied a specialized heavy metal reduction process, which includes sieving and washing for treating residues before incineration. The preferable screen aperture for sieving was found to be 2.36 mm (8 meshes) in this study; using this screen aperture resulted in the removal of approximately 47.2% Cu, 65.9% Zn, 26.5% Pb, 55.4% Ni and 58.8% Cd from the residues. Subsequent washing further reduces the heavy metal content in the residues larger than 2.36 mm, with preferable conditions being 400 rpm rotation speed, 5 min washing duration and liquid-to-solid ratio of 25:1. The highest cumulative removal efficiencies of Cu, Zn, Pb, Ni and Cd after sieving and washing reached 81.1%, 61.4%, 75.8%, 97.2% and 72.7%, respectively. The combined sieving and washing process is environmentally friendly, can be used for the removal of heavy metals from the residues and has benefits in terms of heavy metal recycling.

  4. Quantitative analysis of orthopedic metal artefact reduction in 64-slice computed tomography scans in large head metal-on-metal total hip replacement, a phantom study

    NARCIS (Netherlands)

    Boomsma, Martijn F.; Warringa, Niek; Edens, Mireille A.; Mueller, Dirk; Ettema, Harmen B.; Verheyen, Cees C. P. M.; Maas, Mario

    2016-01-01

    Purpose: Quantification of the effect of O-MAR on decreasing metal artefacts caused by large head metal on metal total hip arthroplasty (MoM THA) in a dedicated phantom setup of the hip. Background: Pathological reactions of the hip capsule on Computed tomography (CT) can be difficult to diagnose

  5. Harnessing microbial subsurface metal reduction activities to synthesise nanoscale cobalt ferrite with enhanced magnetic properties

    Energy Technology Data Exchange (ETDEWEB)

    Coker, Victoria S.; Telling, Neil D.; van der Laan, Gerrit; Pattrick, Richard A.D.; Pearce, Carolyn I.; Arenholz, Elke; Tuna, Floriana; Winpenny, Richard E.P.; Lloyd, Jonathan R.

    2009-03-24

    Fe into the structure of magnetite (Fe{sub 3}O{sub 4}) has been shown to greatly enhance the magnetic properties of the particles, tailoring them to different commercial uses. However, synthesis of magnetic nanoparticles is often carried out at high temperatures with toxic solvents resulting in high environmental and energy costs. Additionally, these ferrite nanoparticles are not intrinsically biocompatible, and to make them suitable for insertion into the human body is a rather intricate task. A relatively unexplored resource for magnetic nanomaterial production is subsurface Fe(III)-reducing bacteria, as these microorganisms are capable of producing large quantities of nanoscale magnetite (Fe{sub 3}O{sub 4}) at ambient temperatures. Metal-reducing bacteria live in environments deficient in oxygen and conserve energy for growth through the oxidation of hydrogen or organic electron donors, coupled to the reduction of oxidized metals such as Fe(III)-bearing minerals. This can result in the formation of magnetite via the extracellular reduction of amorphous Fe(III)-oxyhydroxides causing the release of soluble Fe(II) and resulting in complete recrystallization of the amorphous mineral into a new phase. Some previous studies have reported altering the composition of biogenic magnetite produced by Fe(III)-reducing bacteria for industrial and environmental applications. However, research into the commercial exploitation of bacteria to form magnetic minerals has focused primarily on magnetotactic bacteria which form magnetosomal magnetite internally using very different pathways to those bacteria forming magnetite outside the cell. Magnetotactic bacteria live at the sediment-water interface and use internal nanomagnets to guide them to their preferred environmental niche using the Earth's magnetic field. Since magnetotactic bacteria generally grow optimally under carefully controlled microaerobic conditions, the culturing processes for these organisms are challenging

  6. Harnessing microbial subsurface metal reduction activities to synthesize nanoscale cobalt ferrite with enhanced magnetic properties

    International Nuclear Information System (INIS)

    Coker, Victoria S.; Telling, Neil D.; van der Laan, Gerrit; Pattrick, Richard A.D.; Pearce, Carolyn I.; Arenholz, Elke; Tuna, Floriana; Winpenny, Richard E.P.; Lloyd, Jonathan R.

    2009-01-01

    of magnetite (Fe 3 O 4 ) has been shown to greatly enhance the magnetic properties of the particles, tailoring them to different commercial uses. However, synthesis of magnetic nanoparticles is often carried out at high temperatures with toxic solvents resulting in high environmental and energy costs. Additionally, these ferrite nanoparticles are not intrinsically biocompatible, and to make them suitable for insertion into the human body is a