A Novel Nipple Reconstruction Technique for Maintaining Nipple Projection: The Boomerang Flap

Directory of Open Access Journals (Sweden)

Young-Eun Kim

2016-09-01

Full Text Available Nipple-areolar complex (NAC reconstruction is the final step in the long journey of breast reconstruction for mastectomy patients. Successful NAC reconstruction depends on the use of appropriate surgical techniques that are simple and reliable. To date, numerous techniques have been used for nipple reconstruction, including contralateral nipple sharing and various local flaps. Recently, it has been common to utilize local flaps. However, the most common nipple reconstruction problem encountered with local flaps is the loss of nipple projection; there can be approximately 50% projection loss in reconstructed nipples over long-term follow-up. Several factors might contribute to nipple projection loss, and we tried to overcome these factors by performing nipple reconstructions using a boomerang flap technique, which is a modified C–V flap that utilizes the previous mastectomy scar to maintain long-term nipple projection.

A Novel Nipple Reconstruction Technique for Maintaining Nipple Projection: The Boomerang Flap.

Science.gov (United States)

Kim, Young-Eun; Hong, Ki Yong; Minn, Kyung Won; Jin, Ung Sik

2016-09-01

Nipple-areolar complex (NAC) reconstruction is the final step in the long journey of breast reconstruction for mastectomy patients. Successful NAC reconstruction depends on the use of appropriate surgical techniques that are simple and reliable. To date, numerous techniques have been used for nipple reconstruction, including contralateral nipple sharing and various local flaps. Recently, it has been common to utilize local flaps. However, the most common nipple reconstruction problem encountered with local flaps is the loss of nipple projection; there can be approximately 50% projection loss in reconstructed nipples over long-term follow-up. Several factors might contribute to nipple projection loss, and we tried to overcome these factors by performing nipple reconstructions using a boomerang flap technique, which is a modified C-V flap that utilizes the previous mastectomy scar to maintain long-term nipple projection.

Qualitative and quantitative analysis of reconstructed images using projections with noises

International Nuclear Information System (INIS)

Lopes, R.T.; Assis, J.T. de

1988-01-01

The reconstruction of a two-dimencional image from one-dimensional projections in an analytic algorithm ''convolution method'' is simulated on a microcomputer. In this work it was analysed the effects caused in the reconstructed image in function of the number of projections and noise level added to the projection data. Qualitative and quantitative (distortion and image noise) comparison were done with the original image and the reconstructed images. (author) [pt

The Hanford Environmental Dose Reconstruction Project: Overview

International Nuclear Information System (INIS)

Haerer, H.A.; Freshley, M.D.; Gilbert, R.O.; Morgan, L.G.; Napier, B.A.; Rhoads, R.E.; Woodruff, R.K.

1990-01-01

In 1988, researchers began a multiyear effort to estimate radiation doses that people could have received since 1944 at the U.S. Department of Energy's Hanford Site. The study was prompted by increasing concern about potential health effects to the public from more than 40 yr of nuclear activities. We will provide an overview of the Hanford Environmental Dose Reconstruction Project and its technical approach. The work has required development of new methods and tools for dealing with unique technical and communication challenges. Scientists are using a probabilistic, rather than the more typical deterministic, approach to generate dose distributions rather than single-point estimates. Uncertainties in input parameters are reflected in dose results. Sensitivity analyses are used to optimize project resources and define the project's scope. An independent technical steering panel directs and approves the work in a public forum. Dose estimates are based on review and analysis of historical data related to operations, effluents, and monitoring; determination of important radionuclides; and reconstruction of source terms, environmental conditions that affected transport, concentrations in environmental media, and human elements, such as population distribution, agricultural practices, food consumption patterns, and lifestyles. A companion paper in this volume, The Hanford Environmental Dose Reconstruction Project: Technical Approach, describes the computational framework for the work

Hanford Environmental Dose Reconstruction Project

International Nuclear Information System (INIS)

Finch, S.M.; McMakin, A.H.

1992-06-01

The objective of the Hanford Environmental Dose Reconstruction Project is to estimate the radiation doses that individuals and populations could have received from nuclear operations at Hanford since 1944. The project is being managed and conducted by the Battelle Pacific Northwest Laboratories under contract with the Centers for Disease Control. The independent Technical Steering Panel (TSP) provides technical direction. The project is divided into the following technical tasks. These tasks correspond to the path radionuclides followed, from release to impact on humans (dose estimates): source terms; environmental transport; environmental monitoring data; demography, food consumption, and agriculture; environmental pathways and dose estimates

A reconstruction algorithm for coherent scatter computed tomography based on filtered back-projection

International Nuclear Information System (INIS)

Stevendaal, U. van; Schlomka, J.-P.; Harding, A.; Grass, M.

2003-01-01

Coherent scatter computed tomography (CSCT) is a reconstructive x-ray imaging technique that yields the spatially resolved coherent-scatter form factor of the investigated object. Reconstruction from coherently scattered x-rays is commonly done using algebraic reconstruction techniques (ART). In this paper, we propose an alternative approach based on filtered back-projection. For the first time, a three-dimensional (3D) filtered back-projection technique using curved 3D back-projection lines is applied to two-dimensional coherent scatter projection data. The proposed algorithm is tested with simulated projection data as well as with projection data acquired with a demonstrator setup similar to a multi-line CT scanner geometry. While yielding comparable image quality as ART reconstruction, the modified 3D filtered back-projection algorithm is about two orders of magnitude faster. In contrast to iterative reconstruction schemes, it has the advantage that subfield-of-view reconstruction becomes feasible. This allows a selective reconstruction of the coherent-scatter form factor for a region of interest. The proposed modified 3D filtered back-projection algorithm is a powerful reconstruction technique to be implemented in a CSCT scanning system. This method gives coherent scatter CT the potential of becoming a competitive modality for medical imaging or nondestructive testing

Hanford Environmental Dose Reconstruction Project

International Nuclear Information System (INIS)

Cannon, S.D.; Finch, S.M.

1992-10-01

The objective of the Hanford Environmental Dose Reconstruction (HEDR) Project is to estimate the radiation doses that individuals and populations could have received from nuclear operations at Hanford since 1944. The independent Technical Steering Panel (TSP) provides technical direction. The project is divided into the following technical tasks. These tasks correspond to the path radionuclides followed from release to impact on humans (dose estimates):Source Terms, Environmental Transport, Environmental Monitoring Data, Demography, Food Consumption, and Agriculture, and Environmental Pathways and Dose Estimates

Image reconstruction from multiple fan-beam projections

International Nuclear Information System (INIS)

Jelinek, J.; Overton, T.R.

1984-01-01

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

Parametric image reconstruction using spectral analysis of PET projection data

International Nuclear Information System (INIS)

Meikle, Steven R.; Matthews, Julian C.; Cunningham, Vincent J.; Bailey, Dale L.; Livieratos, Lefteris; Jones, Terry; Price, Pat

1998-01-01

Spectral analysis is a general modelling approach that enables calculation of parametric images from reconstructed tracer kinetic data independent of an assumed compartmental structure. We investigated the validity of applying spectral analysis directly to projection data motivated by the advantages that: (i) the number of reconstructions is reduced by an order of magnitude and (ii) iterative reconstruction becomes practical which may improve signal-to-noise ratio (SNR). A dynamic software phantom with typical 2-[ 11 C]thymidine kinetics was used to compare projection-based and image-based methods and to assess bias-variance trade-offs using iterative expectation maximization (EM) reconstruction. We found that the two approaches are not exactly equivalent due to properties of the non-negative least-squares algorithm. However, the differences are small ( 1 and, to a lesser extent, VD). The optimal number of EM iterations was 15-30 with up to a two-fold improvement in SNR over filtered back projection. We conclude that projection-based spectral analysis with EM reconstruction yields accurate parametric images with high SNR and has potential application to a wide range of positron emission tomography ligands. (author)

Generalized Filtered Back-Projection for Digital Breast Tomosynthesis Reconstruction

NARCIS (Netherlands)

Erhard, K.; Grass, M.; Hitziger, S.; Iske, A.; Nielsen, T.

2012-01-01

Filtered back-projection (FBP) has been commonly used as an efficient and robust reconstruction technique in tomographic X-ray imagingduring the last decades. For limited angle tomography acquisitions such as digital breast tomosynthesis, however, standard FBP reconstruction algorithms provide poor

Intensity-based bayesian framework for image reconstruction from sparse projection data

International Nuclear Information System (INIS)

Rashed, E.A.; Kudo, Hiroyuki

2009-01-01

This paper presents a Bayesian framework for iterative image reconstruction from projection data measured over a limited number of views. The classical Nyquist sampling rule yields the minimum number of projection views required for accurate reconstruction. However, challenges exist in many medical and industrial imaging applications in which the projection data is undersampled. Classical analytical reconstruction methods such as filtered backprojection (FBP) are not a good choice for use in such cases because the data undersampling in the angular range introduces aliasing and streak artifacts that degrade lesion detectability. In this paper, we propose a Bayesian framework for maximum likelihood-expectation maximization (ML-EM)-based iterative reconstruction methods that incorporates a priori knowledge obtained from expected intensity information. The proposed framework is based on the fact that, in tomographic imaging, it is often possible to expect a set of intensity values of the reconstructed object with relatively high accuracy. The image reconstruction cost function is modified to include the l 1 norm distance to the a priori known information. The proposed method has the potential to regularize the solution to reduce artifacts without missing lesions that cannot be expected from the a priori information. Numerical studies showed a significant improvement in image quality and lesion detectability under the condition of highly undersampled projection data. (author)

Optimized image acquisition for breast tomosynthesis in projection and reconstruction space

International Nuclear Information System (INIS)

Chawla, Amarpreet S.; Lo, Joseph Y.; Baker, Jay A.; Samei, Ehsan

2009-01-01

Breast tomosynthesis has been an exciting new development in the field of breast imaging. While the diagnostic improvement via tomosynthesis is notable, the full potential of tomosynthesis has not yet been realized. This may be attributed to the dependency of the diagnostic quality of tomosynthesis on multiple variables, each of which needs to be optimized. Those include dose, number of angular projections, and the total angular span of those projections. In this study, the authors investigated the effects of these acquisition parameters on the overall diagnostic image quality of breast tomosynthesis in both the projection and reconstruction space. Five mastectomy specimens were imaged using a prototype tomosynthesis system. 25 angular projections of each specimen were acquired at 6.2 times typical single-view clinical dose level. Images at lower dose levels were then simulated using a noise modification routine. Each projection image was supplemented with 84 simulated 3 mm 3D lesions embedded at the center of 84 nonoverlapping ROIs. The projection images were then reconstructed using a filtered backprojection algorithm at different combinations of acquisition parameters to investigate which of the many possible combinations maximizes the performance. Performance was evaluated in terms of a Laguerre-Gauss channelized Hotelling observer model-based measure of lesion detectability. The analysis was also performed without reconstruction by combining the model results from projection images using Bayesian decision fusion algorithm. The effect of acquisition parameters on projection images and reconstructed slices were then compared to derive an optimization rule for tomosynthesis. The results indicated that projection images yield comparable but higher performance than reconstructed images. Both modes, however, offered similar trends: Performance improved with an increase in the total acquisition dose level and the angular span. Using a constant dose level and angular

Questions of uniqueness and resolution in reconstruction from projections

CERN Document Server

Katz, Myron Bernard

1978-01-01

Reconstruction from projections has revolutionized radiology and as now become one of the most important tools of medical diagnosi- he E. M. I. Scanner is one example. In this text, some fundamental heoretical and practical questions are resolved. Despite recent research activity in the area, the crucial subject ·f the uniqueness of the reconstruction and the effect of noise in the ata posed some unsettled fundamental questions. In particular, Kennan mith proved that if we describe an object by a C~ function, i. e. , nfinitely differentiable with compact support, then there are other bjects with the same shape, i. e. , support, which can differ almost rhitrarily and still have the same projections in finitely many direc­ ions. On the other hand, he proved that objects in finite dimensional unction spaces are uniquely determined by a single projection for almost 11 angles, i. e. , except on a set of measure zero. Along these lines, erman and Rowland in [41) showed that reconstructions obtained from he common...

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

International Nuclear Information System (INIS)

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

2010-01-01

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

Hanford Environmental Dose Reconstruction Project monthly report

International Nuclear Information System (INIS)

Finch, S.M.

1991-10-01

The objective of the Hanford Environmental Dose Reconstruction Project is to estimate the radiation doeses that individuals and populations could have received from nuclear operations at Hanford since 1944. The project is divided into the following technical tasks. These tasks correspond to the path radionuclides followed, from release to impact on humans (dose estimates): Source terms; environmental transport; environmental monitoring data; demographics, agriculture, food habits; environmental pathways and dose estimates

The NIOSH Radiation Dose Reconstruction Project: managing technical challenges.

Science.gov (United States)

Moeller, Matthew P; Townsend, Ronald D; Dooley, David A

2008-07-01

Approximately two years after promulgation of the Energy Employees Occupational Illness Compensation Program Act, the National Institute for Occupational Safety and Health Office of Compensation and Analysis Support selected a contractor team to perform many aspects of the radiation dose reconstruction process. The project scope and schedule necessitated the development of an organization involving a comparatively large number of health physicists. From the initial stages, there were many technical and managerial challenges that required continuous planning, integration, and conflict resolution. This paper identifies those challenges and describes the resolutions and lessons learned. These insights are hopefully useful to managers of similar scientific projects, especially those requiring significant data, technical methods, and calculations. The most complex challenge has been to complete defensible, individualized dose reconstructions that support timely compensation decisions at an acceptable production level. Adherence to applying claimant-favorable and transparent science consistent with the requirements of the Act has been the key to establishing credibility, which is essential to this large and complex project involving tens of thousands of individual stakeholders. The initial challenges included garnering sufficient and capable scientific staff, developing an effective infrastructure, establishing necessary methods and procedures, and integrating activities to ensure consistent, quality products. The continuing challenges include maintaining the project focus on recommending a compensation determination (rather than generating an accurate dose reconstruction), managing the associated very large data and information management challenges, and ensuring quality control and assurance in the presence of an evolving infrastructure. The lessons learned concern project credibility, claimant favorability, project priorities, quality and consistency, and critical

Preconditioned alternating projection algorithms for maximum a posteriori ECT reconstruction

International Nuclear Information System (INIS)

Krol, Andrzej; Li, Si; Shen, Lixin; Xu, Yuesheng

2012-01-01

We propose a preconditioned alternating projection algorithm (PAPA) for solving the maximum a posteriori (MAP) emission computed tomography (ECT) reconstruction problem. Specifically, we formulate the reconstruction problem as a constrained convex optimization problem with the total variation (TV) regularization. We then characterize the solution of the constrained convex optimization problem and show that it satisfies a system of fixed-point equations defined in terms of two proximity operators raised from the convex functions that define the TV-norm and the constraint involved in the problem. The characterization (of the solution) via the proximity operators that define two projection operators naturally leads to an alternating projection algorithm for finding the solution. For efficient numerical computation, we introduce to the alternating projection algorithm a preconditioning matrix (the EM-preconditioner) for the dense system matrix involved in the optimization problem. We prove theoretically convergence of the PAPA. In numerical experiments, performance of our algorithms, with an appropriately selected preconditioning matrix, is compared with performance of the conventional MAP expectation-maximization (MAP-EM) algorithm with TV regularizer (EM-TV) and that of the recently developed nested EM-TV algorithm for ECT reconstruction. Based on the numerical experiments performed in this work, we observe that the alternating projection algorithm with the EM-preconditioner outperforms significantly the EM-TV in all aspects including the convergence speed, the noise in the reconstructed images and the image quality. It also outperforms the nested EM-TV in the convergence speed while providing comparable image quality. (paper)

Surgical outcomes and nipple projection using the modified skate flap for nipple-areolar reconstruction in a series of 422 implant reconstructions.

Science.gov (United States)

Zhong, Toni; Antony, Anu; Cordeiro, Peter

2009-05-01

Numerous techniques have been used in an attempt to achieve long-term nipple projection following nipple-areolar reconstruction (NAR). A common setback, however, is the diminution of projection over time; this phenomenon is particularly evident following implant based breast reconstruction. The purpose of this report was thus to evaluate surgical outcomes and long-term nipple projection with the use of "modified skate flap" technique in exclusively implant based postmastectomy reconstructions. A retrospective review was performed for the period between 1993 and 2007. All consecutive patients with 2-staged tissue expander/implant reconstructions followed by NAR using the modified skate flap technique performed by the senior author (P.C.) were identified in a prospectively maintained breast reconstruction database. Only patients with a minimum of 1-year follow-up were included in the study. Patients with a history of irradiation to the breast were excluded from nipple projection assessment. Clinical outcome measurements included long-term nipple projection as well as incidence of complications from the NAR procedure using the modified skate flap technique. Over the 15-year study period, 475 patients underwent 2-staged tissue expander/implant reconstruction followed by NAR using the modified skate flap technique. Of these, there was a total of 292 patients with the minimum requirement of 1-year follow-up post NAR (61% follow-up rate). The total number of reconstructed nipple areolar complexes evaluated in this series was 422 (130 bilateral and 162 unilateral NAR). Forty patients (28 unilateral and 12 bilateral NAR) who received radiation to their breasts were excluded from nipple projection assessment. At a median follow-up of 44 months (range: 12-84 months), mean nipple projection was 2.5 mm (range: 1-4 mm). Minor complications occurred in 7.2% of the patients (n = 292). Skin graft donor site dehiscence was the most common complication (3.1%) followed by partial skin

Hanford Environmental Dose Reconstruction Project

International Nuclear Information System (INIS)

McMakin, A.H.; Cannon, S.D.; Finch, S.M.

1992-07-01

The objective of the Hanford Environmental Dose Reconstruction (HEDR) Project is to estimate the radiation doses that individuals and populations could have received from nuclear operations at Hanford since 1944. The TSP consists of experts in environmental pathways, epidemiology, surface-water transport, ground-water transport, statistics, demography, agriculture, meteorology, nuclear engineering, radiation dosimetry, and cultural anthropology. Included are appointed technical members representing the states of Oregon, Washington, and Idaho, a representative of Native American tribes, and an individual representing the public. The project is divided into the following technical tasks. These tasks correspond to the path radionuclides followed from release to impact on humans (dose estimates): Source terms, environmental transport, environmental monitoring data, demography, food consumption, and agriculture, and environmental pathways and dose estimates. Progress is discussed

FY 1991 project plan for the Hanford Environmental Dose Reconstruction Project, Phase 2

International Nuclear Information System (INIS)

1991-02-01

Phase 1 of the Hanford Environmental Dose Reconstruction Project was designed to develop and demonstrate a method for estimating radiation doses people may have received from Hanford Site operations since 1944. The method researchers developed relied on a variety of measured and reconstructed data as input to a modular computer model that generates dose estimates and their uncertainties. As part of Phase 1, researchers used the reconstructed data and computer model to calculate preliminary dose estimates for populations in a limited geographical area and time period. Phase 2, now under way, is designed to evaluate the Phase 1 data and model and improve them to calculate more accurate and precise dose estimates. Phase 2 will also be used to obtain preliminary estimates of two categories of doses: for Native American tribes and for individuals included in the pilot phase of the Hanford Thyroid Disease Study (HTDS). TSP Directive 90-1 required HEDR staff to develop Phase 2 task plans for TSP approval. Draft task plans for Phase 2 were submitted to the TSP at the October 11--12, 1990 public meeting, and, after discussions of each activity and associated budget needs, the TSP directed HEDR staff to proceed with a slate of specific project activities for FY 1991 of Phase 2. This project plan contains detailed information about those activities. Phase 2 is expected to last 15--18 months. In mid-FY 1991, project activities and budget will be reevaluated to determine whether technical needs or priorities have changed. Separate from, but related to, this project plan, will be an integrated plan for the remainder of the project. HEDR staff will work with the TSP to map out a strategy that clearly describes ''end products'' for the project and the work necessary to complete them. This level of planning will provide a framework within which project decisions in Phases 2, 3, and 4 can be made

Hanford Environmental Dose Reconstruction Project monthly report

International Nuclear Information System (INIS)

Finch, S.M.

1990-12-01

The objective of the Hanford Environmental Dose Reconstruction Project is to estimate the radiation doses that populations could have been have received from nuclear operations at Hanford since 1944. The project is being managed and conducted by the Pacific Northwest Laboratory (PNL) under the direction of an independent Technical Steering Panel (TSP). The project is divided into the following technical tasks. These tasks correspond to the path radionuclides followed, from release to impact on humans (dose estimates): source terms; environmental transport; environmental monitoring data; demographics, agriculture, food habits; and environmental pathways and dose estimates. 3 figs., 3 tabs

Communication tools for the Hanford Environmental Dose Reconstruction Project

International Nuclear Information System (INIS)

Blazek, Mary Lou; Power, Max S.

1992-01-01

From 1944 to 1989, the U.S. Department of Energy produced plutonium at the Hanford Site in southeast Washington State. In the early days of operation, large amounts of radioactive materials were released to the environment. Documents about the releases were made public in 1986. The Hanford Environmental Dose Reconstruction Project began in 1987. The Project will determine how much radioactive material was released, how that material may have exposed people, and what radiation doses people may have received. The Project will be complete in 1995. The federal government pays for the work. The scientific work on the study is done by Battelle's Pacific Northwest Laboratory. Public credibility and valid science are equally important to those directing the dose reconstruction work. A number of tools are used to inform the public and encourage public participation. These tools are examined in this paper. (author)

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

Science.gov (United States)

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

2017-01-01

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

Developing milk industry estimates for dose reconstruction projects

International Nuclear Information System (INIS)

Beck, D.M.; Darwin, R.F.

1991-01-01

One of the most important contributors to radiation doses from hanford during the 1944-1947 period was radioactive iodine. Consumption of milk from cows that ate vegetation contaminated with iodine is likely the dominant pathway of human exposure. To estimate the doses people could have received from this pathway, it is necessary to reconstruct the amount of milk consumed by people living near Hanford, the source of the milk, and the type of feed that the milk cows ate. This task is challenging because the dairy industry has undergone radical changes since the end of World War 2, and records that document the impact of these changes on the study area are scarce. Similar problems are faced by researchers on most dose reconstruction efforts. The purpose of this work is to document and evaluate the methods used on the Hanford Environmental Dose Reconstruction (HEDR) Project to reconstruct the milk industry and to present preliminary results

Angular integration and inter-projection correlation effects in CT reconstruction

International Nuclear Information System (INIS)

Crawford, C.R.; Pele, N.J.

1987-01-01

CT reconstruction algorithms require snap-shot projections of an object. In order to minimize scan times, CT scanners rotate continuously which, in turn, prevents the acquisition of snap-shot projections. Acquired projections are integrals over angular position and may be correlated inter-projection. This paper shows that angular integration and inter-projection correlation introduce a radially dependent degradation of the spatial resolution and cause the image noise to vary non-linearly with radial position

Overview of the Hanford Environmental Dose Reconstruction Project

International Nuclear Information System (INIS)

Shipler, D.B.; Napier, B.A.; Ikenberry, T.A.

1992-04-01

The objective of the Hanford Environmental Dose Reconstruction (HEDR) Project is to estimate the radiation doses that specific and representative individuals and populations may have received as a result of releases of radioactive materials from historical operations at the Hanford Site. These dose estimates would account for the uncertainties of information regarding facilities operations, environmental monitoring, demography, food consumption and lifestyles, and the variability of natural phenomena. Other objectives of the HEDR Project include: supporting the Hanford Thyroid Disease Study (HTDS), declassifying Hanford-generated information and making it available to the public, performing high-quality, credible science, and conducting the project in an open, public forum. The project is briefly described

Phase 1 of the Hanford Environmental Dose Reconstruction Project

International Nuclear Information System (INIS)

1991-08-01

The work described in this report was prompted by the public's concern about potential effect from the radioactive materials released from the Hanford Site. The Hanford Environmental Dose Reconstruction (HEDR) Project was established to estimate radiation dose the public might have received from the Hanford Site since 1944, when facilities began operating. Phase 1 of the HEDR Project is a ''pilot'' or ''demonstration'' phase. The objectives of this initial phase were to determine whether enough historical information could be found or reconstructed to be used for dose estimation and develop and test conceptual and computational models for calculating credible dose estimates. Preliminary estimates of radiation doses were produced in Phase 1 because they are needed to achieve these objectives. The reader is cautioned that the dose estimates provided in this and other Phase 1 HEDR reports are preliminary. As the HEDR Project continues, the dose estimates will change for at least three reasons: more complete input information for models will be developed; the models themselves will be refined; and the size and shape of the geographic study area will change. This is one of three draft reports that summarize the first phase of the four-phased HEDR Project. This, the Summary Report, is directed to readers who want a general understanding of the Phase 1 work and preliminary dose estimates. The two other reports -- the Air Pathway Report and the Columbia River Pathway Report -- are for readers who understand the radiation dose assessment process and want to see more technical detail. Detailed descriptions of the dose reconstruction process are available in more than 20 supporting reports listed in Appendix A. 32 refs., 46 figs

Fast cross-projection algorithm for reconstruction of seeds in prostate brachytherapy

International Nuclear Information System (INIS)

Narayanan, Sreeram; Cho, Paul S.; Marks, Robert J. II

2002-01-01

A fast method of seed matching and reconstruction in prostrate brachytherapy is proposed. Previous approaches have required all seeds to be matched with all other seeds in other projections. The fast cross-projection algorithm for the reconstruction of seeds (Fast-CARS) allows for matching of a given seed with a subset of seeds in other projections. This subset lies in a proximal region centered about the projection of a line, connecting the seed to its source, onto other projection planes. The proposed technique permits a significant reduction in computational overhead, as measured by the required number of matching tests. The number of multiplications and additions is also vastly reduced at no trade-off in accuracy. Because of its speed, Fast-CARS can be used in applications requiring real-time performance such as intraoperative dosimetry of prostate brachytherapy. Furthermore, the proposed method makes practical the use of a larger number of views as opposed to previous techniques limited to a maximum use of three views

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

International Nuclear Information System (INIS)

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

2010-01-01

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

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

Science.gov (United States)

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

2010-04-01

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

3D reconstruction of laser projective point with projection invariant generated from five points on 2D target.

Science.gov (United States)

Xu, Guan; Yuan, Jing; Li, Xiaotao; Su, Jian

2017-08-01

Vision measurement on the basis of structured light plays a significant role in the optical inspection research. The 2D target fixed with a line laser projector is designed to realize the transformations among the world coordinate system, the camera coordinate system and the image coordinate system. The laser projective point and five non-collinear points that are randomly selected from the target are adopted to construct a projection invariant. The closed form solutions of the 3D laser points are solved by the homogeneous linear equations generated from the projection invariants. The optimization function is created by the parameterized re-projection errors of the laser points and the target points in the image coordinate system. Furthermore, the nonlinear optimization solutions of the world coordinates of the projection points, the camera parameters and the lens distortion coefficients are contributed by minimizing the optimization function. The accuracy of the 3D reconstruction is evaluated by comparing the displacements of the reconstructed laser points with the actual displacements. The effects of the image quantity, the lens distortion and the noises are investigated in the experiments, which demonstrate that the reconstruction approach is effective to contribute the accurate test in the measurement system.

Reconstruction of tomographic image from x-ray projections of a few views

International Nuclear Information System (INIS)

Kobayashi, Fujio; Yamaguchi, Shoichiro

1982-01-01

Computer tomographs have progressed rapidly, and in the latest high performance types, the photographing time has been shortened to less than 5 sec, but the clear images of hearts have not yet been obtained. The X-ray tomographs used so far irradiate X-ray from many directions and measure the projected data, but by limiting projection direction to a small number, it was planned to shorter the X-ray photographing time and to reduce X-ray exposure as the objective of this study. In this paper, a method is proposed, by which tomographic images are reconstructed from projected data in a small number of direction by generalized inverse matrix penalty method. This method is the calculation method newly devised by the authors for this purpose. It is a kind of the nonlinear planning method added with the restrictive condition using a generalized inverse matrix, and it is characterized by the simple calculation procedure and rapid convergence. Moreover, the effect on reconstructed images when errors are included in projected data was examined. Also, the simple computer simulation to reconstruct tomographic images using the projected data in four directions was performed, and the usefulness of this method was confirmed. It contributes to the development of superhigh speed tomographs in future. (Kako, I.)

Hanford Environmental Dose Reconstruction Project independent direction and oversight

International Nuclear Information System (INIS)

Blazek, M.L.; Power, M.

1991-01-01

Hanford was selected in 1942 as one of the sites for the Manhattan Project. It produced plutonium for one of the world's first nuclear weapons. The US Department of Energy (DOE) and its predecessors continued to make plutonium for nuclear weapons at Hanford for more than four decades. In the early days of Hanford operations, radioactive materials routinely were released to the environment by many processes. The DOE disclosed documents about these releases in 1986. In 1987, Washington, Oregon, and regional Indian tribes gathered an independent panel of experts. This group recommended dose reconstruction and health effects feasibility studies. Later that year, DOE hired Battelle Pacific Northwest Laboratory (PNL) to reconstruct potential public radiation doses from Hanford's past releases of radioactive material. The DOE agreed with the states and tribes that project direction would come from an independent technical steering panel (TSP). This approach was critical to gain public credibility for the project and the science. The TSP directs the project and makes policy. That is now clear - but, it was hard-earned. Conducting science in an open public process is new, challenging, and clearly worthwhile. The panel's product is good science that is believed and accepted by the public - our client

Projection matrix acquisition for cone-beam computed tomography iterative reconstruction

Science.gov (United States)

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

2017-02-01

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

Comparison of tomography reconstruction by maximum entropy and filtered retro projection

International Nuclear Information System (INIS)

Abdala, F.J.P.; Simpson, D.M.; Roberty, N.C.

1992-01-01

The tomographic reconstruction with few projections is studied, comparing the maximum entropy method with filtered retro projection. Simulations with and without the presence of noise and also with the presence of an object of high density inside of the skull are showed. (C.G.C.)

Hanford Environmental Dose Reconstruction Project monthly report, August 1992

International Nuclear Information System (INIS)

McMakin, A.H.; Cannon, S.D.; Finch, S.M.

1992-01-01

The objective of the Hanford Environmental Dose Reconstruction (HEDR) Project is to estimate the radiation doses that individuals and populations could have received from nuclear operations at Hanford since 1944. The project is divided into the following technical tasks. These tasks correspond to the path radionuclides followed from release to impact on humans (dose estimates): source terms; environmental transport; environmental monitoring data; demography; food consumption; and agriculture; and environmental pathway and dose estimates

Direct image reconstruction with limited angle projection data for computerized tomography

International Nuclear Information System (INIS)

Inouye, T.

1980-01-01

Discussions are made on the minimum angle range for projection data necessary to reconstruct the complete CT image. As is easily shown from the image reconstruction theorem, the lack of projection angle provides no data for the Fourier transformed function of the object on the corresponding angular directions, where the projections are missing. In a normal situation, the Fourier transformed function of an object image holds an analytic characteristic with respect to two-dimensional orthogonal parameters. This characteristic enables uniquely prolonging the function outside the obtained region employing a sort of analytic continuation with respect to both parameters. In the method reported here, an object pattern, which is confined within a finite range, is shifted to a specified region to have complete orthogonal function expansions without changing the projection angle directions. These orthogonal functions are analytically extended to the missing projection angle range and the whole function is determined. This method does not include any estimation process, whose effectiveness is often seriously jeopardized by the presence of a slight fluctuation component. Computer simulations were carried out to demonstrate the effectiveness of the method

Oak Ridge Dose Reconstruction Project Summary Report; Reports of the Oak Ridge Dose Reconstruction, Vol. 7

International Nuclear Information System (INIS)

Widner, Thomas E.; email = twidner@jajoneses.com

1999-01-01

In the early 1990s, concern about the Oak Ridge Reservation's past releases of contaminants to the environment prompted Tennessee's public health officials to pursue an in-depth study of potential off-site health effects at Oak Ridge. This study, the Oak Ridge dose reconstruction, was supported by an agreement between the U.S. Department of Energy (DOE) and the State of Tennessee, and was overseen by a 12-member panel of individuals appointed by Tennessee's Commissioner of Health. The panel requested that the principal investigator for the project prepare the following report, ''Oak Ridge Dose Reconstruction Project Summary Report,'' to serve the following purposes: (1) summarize in a single, less technical report, the methods and results of the various investigations that comprised the Phase II of the dose reconstruction; (2) describe the systematic searching of classified and unclassified historical records that was a vital component of the project; and (3) summarize the less detailed, screening-level assessments that were performed to evaluate the potential health significance of a number of materials, such a uranium, whose priority did not require a complete dose reconstruction effort. This report describes each major step of the dose reconstruction study: (1) the review of thousands of historical records to obtain information relating to past operations at each facility; (2) estimation of the quantity and timing of releases of radioiodines from X-10, of mercury from Y-12, of PCB's from all facilities, and of cesium-137 and other radionuclides from White Oak Creek; (3) evaluation of the routes taken by these contaminants through the environment to nearby populations; and (4) estimation of doses and health risks to exposed groups. Calculations found the highest excess cancer risks for a female born in 1952 who drank goat milk; the highest non-cancer health risk was for children in a farm family exposed to PCBs in and near East Fork Poplar Creek. More detailed

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

International Nuclear Information System (INIS)

Liu, L; Han, Y; Jin, M

2015-01-01

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

The reconstruction of HT-7 superconducting tokamak and the present status of HT-7U project

International Nuclear Information System (INIS)

Weng, P.D.

2000-01-01

The first Chinese superconducting tokamak HT-7 was reconstructed from T-7. The main purposes of reconstruction are to improve the accessibility of the device and to provide a possibility of long pulse operation with high performance. The reconstruction has been done successfully. The HT-7U project has been approved and funded as a National Project, the engineering design and R and D are on the way. (author)

Regional absolute conductivity reconstruction using projected current density in MREIT

International Nuclear Information System (INIS)

Sajib, Saurav Z K; Kim, Hyung Joong; Woo, Eung Je; Kwon, Oh In

2012-01-01

Magnetic resonance electrical impedance tomography (MREIT) is a non-invasive technique for imaging the internal conductivity distribution in tissue within an MRI scanner, utilizing the magnetic flux density, which is introduced when a current is injected into the tissue from external electrodes. This magnetic flux alters the MRI signal, so that appropriate reconstruction can provide a map of the additional z-component of the magnetic field (B z ) as well as the internal current density distribution that created it. To extract the internal electrical properties of the subject, including the conductivity and/or the current density distribution, MREIT techniques use the relationship between the external injection current and the z-component of the magnetic flux density B = (B x , B y , B z ). The tissue studied typically contains defective regions, regions with a low MRI signal and/or low MRI signal-to-noise-ratio, due to the low density of nuclear magnetic resonance spins, short T 2 or T* 2 relaxation times, as well as regions with very low electrical conductivity, through which very little current traverses. These defective regions provide noisy B z data, which can severely degrade the overall reconstructed conductivity distribution. Injecting two independent currents through surface electrodes, this paper proposes a new direct method to reconstruct a regional absolute isotropic conductivity distribution in a region of interest (ROI) while avoiding the defective regions. First, the proposed method reconstructs the contrast of conductivity using the transversal J-substitution algorithm, which blocks the propagation of severe accumulated noise from the defective region to the ROI. Second, the proposed method reconstructs the regional projected current density using the relationships between the internal current density, which stems from a current injection on the surface, and the measured B z data. Combining the contrast conductivity distribution in the entire imaging

An accelerated threshold-based back-projection algorithm for Compton camera image reconstruction

International Nuclear Information System (INIS)

Mundy, Daniel W.; Herman, Michael G.

2011-01-01

Purpose: Compton camera imaging (CCI) systems are currently under investigation for radiotherapy dose reconstruction and verification. The ability of such a system to provide real-time images during dose delivery will be limited by the computational speed of the image reconstruction algorithm. In this work, the authors present a fast and simple method by which to generate an initial back-projected image from acquired CCI data, suitable for use in a filtered back-projection algorithm or as a starting point for iterative reconstruction algorithms, and compare its performance to the current state of the art. Methods: Each detector event in a CCI system describes a conical surface that includes the true point of origin of the detected photon. Numerical image reconstruction algorithms require, as a first step, the back-projection of each of these conical surfaces into an image space. The algorithm presented here first generates a solution matrix for each slice of the image space by solving the intersection of the conical surface with the image plane. Each element of the solution matrix is proportional to the distance of the corresponding voxel from the true intersection curve. A threshold function was developed to extract those pixels sufficiently close to the true intersection to generate a binary intersection curve. This process is repeated for each image plane for each CCI detector event, resulting in a three-dimensional back-projection image. The performance of this algorithm was tested against a marching algorithm known for speed and accuracy. Results: The threshold-based algorithm was found to be approximately four times faster than the current state of the art with minimal deficit to image quality, arising from the fact that a generically applicable threshold function cannot provide perfect results in all situations. The algorithm fails to extract a complete intersection curve in image slices near the detector surface for detector event cones having axes nearly

Hanford Environmental Dose Reconstruction Project monthly report

International Nuclear Information System (INIS)

McMakin, A.H., Cannon, S.D.; Finch, S.M.

1992-09-01

The objective of the Hanford Environmental Dose Reconstruction MDR) Project is to estimate the radiation doses that individuals and populations could have received from nuclear operations at Hanford since 1944. The TSP consists of experts in envirorunental pathways. epidemiology, surface-water transport, ground-water transport, statistics, demography, agriculture, meteorology, nuclear engineering. radiation dosimetry. and cultural anthropology. Included are appointed members representing the states of Oregon, Washington, and Idaho, a representative of Native American tribes, and an individual representing the public. The project is divided into the following technical tasks. These tasks correspond to the path radionuclides followed from release to impact on humans (dose estimates): Source Terms; Environmental Transport; Environmental Monitoring Data Demography, Food Consumption, and Agriculture; and Environmental Pathways and Dose Estimates

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

International Nuclear Information System (INIS)

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

2005-01-01

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

Oak Ridge Dose Reconstruction Project Summary Report; Reports of the Oak Ridge Dose Reconstruction, Vol. 7

Energy Technology Data Exchange (ETDEWEB)

Thomas E. Widner; et. al.

1999-07-01

In the early 1990s, concern about the Oak Ridge Reservation's past releases of contaminants to the environment prompted Tennessee's public health officials to pursue an in-depth study of potential off-site health effects at Oak Ridge. This study, the Oak Ridge dose reconstruction, was supported by an agreement between the U.S. Department of Energy (DOE) and the State of Tennessee, and was overseen by a 12-member panel of individuals appointed by Tennessee's Commissioner of Health. The panel requested that the principal investigator for the project prepare the following report, ''Oak Ridge Dose Reconstruction Project Summary Report,'' to serve the following purposes: (1) summarize in a single, less technical report, the methods and results of the various investigations that comprised the Phase II of the dose reconstruction; (2) describe the systematic searching of classified and unclassified historical records that was a vital component of the project; and (3) summarize the less detailed, screening-level assessments that were performed to evaluate the potential health significance of a number of materials, such a uranium, whose priority did not require a complete dose reconstruction effort. This report describes each major step of the dose reconstruction study: (1) the review of thousands of historical records to obtain information relating to past operations at each facility; (2) estimation of the quantity and timing of releases of radioiodines from X-10, of mercury from Y-12, of PCB's from all facilities, and of cesium-137 and other radionuclides from White Oak Creek; (3) evaluation of the routes taken by these contaminants through the environment to nearby populations; and (4) estimation of doses and health risks to exposed groups. Calculations found the highest excess cancer risks for a female born in 1952 who drank goat milk; the highest non-cancer health risk was for children in a farm family exposed to PCBs in and near

Methods of X-ray CT image reconstruction from few projections

International Nuclear Information System (INIS)

Wang, H.

2011-01-01

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

Imaging reconstruction based on improved wavelet denoising combined with parallel-beam filtered back-projection algorithm

Science.gov (United States)

Ren, Zhong; Liu, Guodong; Huang, Zhen

2012-11-01

The image reconstruction is a key step in medical imaging (MI) and its algorithm's performance determinates the quality and resolution of reconstructed image. Although some algorithms have been used, filter back-projection (FBP) algorithm is still the classical and commonly-used algorithm in clinical MI. In FBP algorithm, filtering of original projection data is a key step in order to overcome artifact of the reconstructed image. Since simple using of classical filters, such as Shepp-Logan (SL), Ram-Lak (RL) filter have some drawbacks and limitations in practice, especially for the projection data polluted by non-stationary random noises. So, an improved wavelet denoising combined with parallel-beam FBP algorithm is used to enhance the quality of reconstructed image in this paper. In the experiments, the reconstructed effects were compared between the improved wavelet denoising and others (directly FBP, mean filter combined FBP and median filter combined FBP method). To determine the optimum reconstruction effect, different algorithms, and different wavelet bases combined with three filters were respectively test. Experimental results show the reconstruction effect of improved FBP algorithm is better than that of others. Comparing the results of different algorithms based on two evaluation standards i.e. mean-square error (MSE), peak-to-peak signal-noise ratio (PSNR), it was found that the reconstructed effects of the improved FBP based on db2 and Hanning filter at decomposition scale 2 was best, its MSE value was less and the PSNR value was higher than others. Therefore, this improved FBP algorithm has potential value in the medical imaging.

Hanford Environmental Dose Reconstruction Project, Quarterly report, September--November 1993

International Nuclear Information System (INIS)

Cannon, S.D.; Finch, S.M.

1993-01-01

The objective of the Hanford Environmental Dose Reconstruction (HEDR) Project is to estimate the radiation doses that individuals and populations could have received from nuclear operations at Hanford since 1944. The project is divided into the following technical tasks. These tasks correspond to the path radionuclides followed from release to impact on humans (dose estimates); Source Terms, Environmental Transport, Environmental Monitoring Data, Demography, Food Consumption, and Agriculture, and Environmental Pathways and Dose Estimates

A Prospective Analysis of Dynamic Loss of Breast Projection in Tissue Expander-Implant Reconstruction

Directory of Open Access Journals (Sweden)

Lauren M Mioton

2015-05-01

Full Text Available BackgroundBreast projection is a critical element of breast reconstruction aesthetics, but little has been published regarding breast projection as the firm expander is changed to a softer implant. Quantitative data representing this loss in projection may enhance patient education and improve our management of patient expectations.MethodsFemale patients who were undergoing immediate tissue-expander breast reconstruction with the senior author were enrolled in this prospective study. Three-dimensional camera software was used for all patient photographs and data analysis. Projection was calculated as the distance between the chest wall and the point of maximal projection of the breast form. Values were calculated for final tissue expander expansion and at varying intervals 3, 6, and 12 months after implant placement.ResultsFourteen breasts from 12 patients were included in the final analysis. Twelve of the 14 breasts had a loss of projection at three months following the implant placement or beyond. The percentage of projection lost in these 12 breasts ranged from 6.30% to 43.4%, with an average loss of projection of 21.05%.ConclusionsThis study is the first prospective quantitative analysis of temporal changes in breast projection after expander-implant reconstruction. By prospectively capturing projection data with three-dimensional photographic software, we reveal a loss of projection in this population by three months post-implant exchange. These findings will not only aid in managing patient expectations, but our methodology provides a foundation for future objective studies of the breast form.

Work plan for the Hanford Environmental Dose Reconstruction Project

Energy Technology Data Exchange (ETDEWEB)

1989-12-01

The primary objective of the Hanford Environmental Dose Reconstruction (HEDR) Project is to estimate the radiation doses that populations could have received from nuclear operations at the Hanford Site since 1944, with descriptions of uncertainties inherent in such estimates. The secondary objective is to make project records--information that HEDR staff members used to estimate radiation doses--available to the public. Preliminary dose estimates for a limited geographic area and time period, certain radionuclides, and certain populations are planned to be available in 1990; complete results are planned to be reported in 1993. Project reports and references used in the reports are available to the public in the DOE Public Reading Room in Richland, Washington. Project progress is documented in monthly reports, which are also available to the public in the DOE Public Reading Room.

An FDK-like cone-beam SPECT reconstruction algorithm for non-uniform attenuated projections acquired using a circular trajectory

International Nuclear Information System (INIS)

Huang, Q; Zeng, G L; You, J; Gullberg, G T

2005-01-01

In this paper, Novikov's inversion formula of the attenuated two-dimensional (2D) Radon transform is applied to the reconstruction of attenuated fan-beam projections acquired with equal detector spacing and of attenuated cone-beam projections acquired with a flat planar detector and circular trajectory. The derivation of the fan-beam algorithm is obtained by transformation from parallel-beam coordinates to fan-beam coordinates. The cone-beam reconstruction algorithm is an extension of the fan-beam reconstruction algorithm using Feldkamp-Davis-Kress's (FDK) method. Computer simulations indicate that the algorithm is efficient and is accurate in reconstructing slices close to the central slice of the cone-beam orbit plane. When the attenuation map is set to zero the implementation is equivalent to the FDK method. Reconstructed images are also shown for noise corrupted projections

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

International Nuclear Information System (INIS)

Yin Fangfang; Guan Huaiqun; Lu Wenkai

2005-01-01

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

Reconstruction of brachytherapy seed positions and orientations from cone-beam CT x-ray projections via a novel iterative forward projection matching method.

Science.gov (United States)

Pokhrel, Damodar; Murphy, Martin J; Todor, Dorin A; Weiss, Elisabeth; Williamson, Jeffrey F

2011-01-01

To generalize and experimentally validate a novel algorithm for reconstructing the 3D pose (position and orientation) of implanted brachytherapy seeds from a set of a few measured 2D cone-beam CT (CBCT) x-ray projections. The iterative forward projection matching (IFPM) algorithm was generalized to reconstruct the 3D pose, as well as the centroid, of brachytherapy seeds from three to ten measured 2D projections. The gIFPM algorithm finds the set of seed poses that minimizes the sum-of-squared-difference of the pixel-by-pixel intensities between computed and measured autosegmented radiographic projections of the implant. Numerical simulations of clinically realistic brachytherapy seed configurations were performed to demonstrate the proof of principle. An in-house machined brachytherapy phantom, which supports precise specification of seed position and orientation at known values for simulated implant geometries, was used to experimentally validate this algorithm. The phantom was scanned on an ACUITY CBCT digital simulator over a full 660 sinogram projections. Three to ten x-ray images were selected from the full set of CBCT sinogram projections and postprocessed to create binary seed-only images. In the numerical simulations, seed reconstruction position and orientation errors were approximately 0.6 mm and 5 degrees, respectively. The physical phantom measurements demonstrated an absolute positional accuracy of (0.78 +/- 0.57) mm or less. The theta and phi angle errors were found to be (5.7 +/- 4.9) degrees and (6.0 +/- 4.1) degrees, respectively, or less when using three projections; with six projections, results were slightly better. The mean registration error was better than 1 mm/6 degrees compared to the measured seed projections. Each test trial converged in 10-20 iterations with computation time of 12-18 min/iteration on a 1 GHz processor. This work describes a novel, accurate, and completely automatic method for reconstructing seed orientations, as well as

Reconstruction of brachytherapy seed positions and orientations from cone-beam CT x-ray projections via a novel iterative forward projection matching method

Energy Technology Data Exchange (ETDEWEB)

Pokhrel, Damodar; Murphy, Martin J.; Todor, Dorin A.; Weiss, Elisabeth; Williamson, Jeffrey F. [Department of Radiation Oncology, School of Medicine, Virginia Commonwealth University, Richmond, Virginia 23298 (United States)

2011-01-15

Purpose: To generalize and experimentally validate a novel algorithm for reconstructing the 3D pose (position and orientation) of implanted brachytherapy seeds from a set of a few measured 2D cone-beam CT (CBCT) x-ray projections. Methods: The iterative forward projection matching (IFPM) algorithm was generalized to reconstruct the 3D pose, as well as the centroid, of brachytherapy seeds from three to ten measured 2D projections. The gIFPM algorithm finds the set of seed poses that minimizes the sum-of-squared-difference of the pixel-by-pixel intensities between computed and measured autosegmented radiographic projections of the implant. Numerical simulations of clinically realistic brachytherapy seed configurations were performed to demonstrate the proof of principle. An in-house machined brachytherapy phantom, which supports precise specification of seed position and orientation at known values for simulated implant geometries, was used to experimentally validate this algorithm. The phantom was scanned on an ACUITY CBCT digital simulator over a full 660 sinogram projections. Three to ten x-ray images were selected from the full set of CBCT sinogram projections and postprocessed to create binary seed-only images. Results: In the numerical simulations, seed reconstruction position and orientation errors were approximately 0.6 mm and 5 deg., respectively. The physical phantom measurements demonstrated an absolute positional accuracy of (0.78{+-}0.57) mm or less. The {theta} and {phi} angle errors were found to be (5.7{+-}4.9) deg. and (6.0{+-}4.1) deg., respectively, or less when using three projections; with six projections, results were slightly better. The mean registration error was better than 1 mm/6 deg. compared to the measured seed projections. Each test trial converged in 10-20 iterations with computation time of 12-18 min/iteration on a 1 GHz processor. Conclusions: This work describes a novel, accurate, and completely automatic method for reconstructing

Use of the geometric mean of opposing planar projections in pre-reconstruction restoration of SPECT images

International Nuclear Information System (INIS)

Boulfelfel, D.; Rangayyan, R.M.; Hahn, L.J.; Kloiber, R.

1992-01-01

This paper presents a restoration scheme for single photon emission computed tomography (SPECT) images that performs restoration before reconstruction (pre-reconstruction restoration) from planar (projection) images. In this scheme, the pixel-by-pixel geometric mean of each pair of opposing (conjugate) planar projections is computed prior to the reconstruction process. The averaging process is shown to help in making the degradation phenomenon less dependent on the distance of each point of the object from the camera. The restoration filters investigated are the Wiener and power spectrum equalization filters. (author)

Computed Tomography Image Quality Evaluation of a New Iterative Reconstruction Algorithm in the Abdomen (Adaptive Statistical Iterative Reconstruction-V) a Comparison With Model-Based Iterative Reconstruction, Adaptive Statistical Iterative Reconstruction, and Filtered Back Projection Reconstructions.

Science.gov (United States)

Goodenberger, Martin H; Wagner-Bartak, Nicolaus A; Gupta, Shiva; Liu, Xinming; Yap, Ramon Q; Sun, Jia; Tamm, Eric P; Jensen, Corey T

The purpose of this study was to compare abdominopelvic computed tomography images reconstructed with adaptive statistical iterative reconstruction-V (ASIR-V) with model-based iterative reconstruction (Veo 3.0), ASIR, and filtered back projection (FBP). Abdominopelvic computed tomography scans for 36 patients (26 males and 10 females) were reconstructed using FBP, ASIR (80%), Veo 3.0, and ASIR-V (30%, 60%, 90%). Mean ± SD patient age was 32 ± 10 years with mean ± SD body mass index of 26.9 ± 4.4 kg/m. Images were reviewed by 2 independent readers in a blinded, randomized fashion. Hounsfield unit, noise, and contrast-to-noise ratio (CNR) values were calculated for each reconstruction algorithm for further comparison. Phantom evaluation of low-contrast detectability (LCD) and high-contrast resolution was performed. Adaptive statistical iterative reconstruction-V 30%, ASIR-V 60%, and ASIR 80% were generally superior qualitatively compared with ASIR-V 90%, Veo 3.0, and FBP (P ASIR-V 60% with respective CNR values of 5.54 ± 2.39, 8.78 ± 3.15, and 3.49 ± 1.77 (P ASIR 80% had the best and worst spatial resolution, respectively. Adaptive statistical iterative reconstruction-V 30% and ASIR-V 60% provided the best combination of qualitative and quantitative performance. Adaptive statistical iterative reconstruction 80% was equivalent qualitatively, but demonstrated inferior spatial resolution and LCD.

Projected Shell Model Description of Positive Parity Band of 130Pr Nucleus

Science.gov (United States)

Singh, Suram; Kumar, Amit; Singh, Dhanvir; Sharma, Chetan; Bharti, Arun; Bhat, G. H.; Sheikh, J. A.

2018-02-01

Theoretical investigation of positive parity yrast band of odd-odd 130Pr nucleus is performed by applying the projected shell model. The present study is undertaken to investigate and verify the very recently observed side band in 130Pr theoretically in terms of quasi-particle (qp) configuration. From the analysis of band diagram, the yrast as well as side band are found to arise from two-qp configuration πh 11/2 ⊗ νh 11/2. The present calculations are viewed to have qualitatively reproduced the known experimental data for yrast states, transition energies, and B( M1) / B( E2) ratios of this nucleus. The recently observed positive parity side band is also reproduced by the present calculations. The energy states of the side band are predicted up to spin 25+, which is far above the known experimental spin of 18+ and this could serve as a motivational factor for future experiments. In addition, the reduced transition probability B( E2) for interband transitions has also been calculated for the first time in projected shell model, which would serve as an encouragement for other research groups in the future.

Iterative reconstruction with attenuation compensation from cone-beam projections acquired via nonplanar orbits

International Nuclear Information System (INIS)

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

1997-01-01

Single photon emission computed tomography (SPECT) imaging with cone-beam collimators provides improved sensitivity and spatial resolution for imaging small objects with large field-of-view detectors. It is known that Tuy's cone-beam data sufficiency condition must be met to obtain artifact-free reconstructions. Even though Tuy's condition was derived for an attenuation-free situation, the authors hypothesize that an artifact-free reconstruction can be obtained even if the cone-beam data are attenuated, provided the imaging orbit satisfies Tuy's condition and the exact attenuation map is known. In the authors' studies, emission data are acquired using nonplanar circle-and-line orbits to acquire cone-beam data for tomographic reconstructions. An extended iterative ML-EM (maximum likelihood-expectation maximization) reconstruction algorithm is derived and used to reconstruct projection data with either a pre-acquired or assumed attenuation map. Quantitative accuracy of the attenuation corrected emission reconstruction is significantly improved

Analysis of Variance of the Effects of a Project’s Location on Key Issues and Challenges in Post-Disaster Reconstruction Projects

Directory of Open Access Journals (Sweden)

Dzulkarnaen Ismail

2017-11-01

Full Text Available After a disaster, the reconstruction phase is driven by immediate challenges. One of the main challenges in the post-disaster period is the way that reconstruction projects are implemented. Reconstruction cannot move forward until some complex issues are settled. The purposes of this research are to highlight the issues and challenges in post-disaster reconstruction (PDR projects and to determine the significant differences between the issues and challenges in different locations where PDR projects are carried out. The researchers collected data within international non-governmental organisations (INGOs on their experience of working with PDR projects. The findings of this research provide the foundation on which to build strategies for avoiding project failures; this may be useful for PDR project practitioners in the future.

Forensic facial reconstruction: Nasal projection in Brazilian adults.

Science.gov (United States)

Tedeschi-Oliveira, Silvia Virginia; Beaini, Thiago Leite; Melani, Rodolfo Francisco Haltenhoff

2016-09-01

The nose has a marked cognitive influence on facial image; however, it loses its shape during cadaveric decomposition. The known methods of estimating nasal projection using Facial Reconstruction are lacking in practicality and reproducibility. We attempted to relate the points Rhinion, Pronasale and Prosthion by studying the angle formed by straight lines that connect them. Two examiners measured this angle with the help of analysis and image-processing software, Image J, directly from cephalometric radiographs. The sample consisted of 300 males, aged between 24 and 77 years, and 300 females, aged 24 to 69 years. The proposed angle ranged from 80° to 100° in both sexes and all ages. It was considered possible to use a 90° angle from projections of the Rhinion and Prosthion points in order to determine the Pronasale position, as well as to estimate the nasal projection of Brazilian adults. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Decision management for the Hanford Environmental Dose Reconstruction Project

Energy Technology Data Exchange (ETDEWEB)

Roberds, W.J.; Haerer, H.A. [Golder Associates, Inc., Redmond, WA (United States); Winterfeldt, D.V. [Decision Insights, Laguna Beach, CA (United States)

1992-04-01

The Hanford Environmental Dose Reconstruction (HEDR) Project is in the process of developing estimates for the radiation doses that individuals and population groups may have received as a result of past activities at the Hanford Reservation in Eastern Washington. A formal decision-aiding methodology has been developed to assist the HEDR Project in making significant and defensible decisions regarding how this study will be conducted. These decisions relate primarily to policy (e.g., the appropriate level of public participation in the study) and specific technical aspects (e.g., the appropriate domain and depth of the study), and may have significant consequences with respect to technical results, costs, and public acceptability.

Decision management for the Hanford Environmental Dose Reconstruction Project

International Nuclear Information System (INIS)

Roberds, W.J.; Haerer, H.A.; Winterfeldt, D.V.

1992-04-01

The Hanford Environmental Dose Reconstruction (HEDR) Project is in the process of developing estimates for the radiation doses that individuals and population groups may have received as a result of past activities at the Hanford Reservation in Eastern Washington. A formal decision-aiding methodology has been developed to assist the HEDR Project in making significant and defensible decisions regarding how this study will be conducted. These decisions relate primarily to policy (e.g., the appropriate level of public participation in the study) and specific technical aspects (e.g., the appropriate domain and depth of the study), and may have significant consequences with respect to technical results, costs, and public acceptability

Influence of sampling interval and number of projections on the quality of SR-XFMT reconstruction

International Nuclear Information System (INIS)

Deng Biao; Yu Xiaohan; Xu Hongjie

2007-01-01

Synchrotron Radiation based X-ray Fluorescent Microtomography (SR-XFMT) is a nondestructive technique for detecting elemental composition and distribution inside a specimen with high spatial resolution and sensitivity. In this paper, computer simulation of SR-XFMT experiment is performed. The influence of the sampling interval and the number of projections on the quality of SR-XFMT image reconstruction is analyzed. It is found that the sampling interval has greater effect on the quality of reconstruction than the number of projections. (authors)

The CHT2 Project: Diachronic 3d Reconstruction of Historic Sites

Science.gov (United States)

Guidi, G.; Micoli, L.; Gonizzi Barsanti, S.; Malik, U.

2017-08-01

Digital modelling archaeological and architectural monuments in their current state and in their presumed past aspect has been recognized not only as a way for explaining to the public the genesis of a historical site, but also as an effective tool for research. The search for historical sources, their proper analysis and interdisciplinary relationship between technological disciplines and the humanities are fundamental for obtaining reliable hypothetical reconstructions. This paper presents an experimental activity defined by the project Cultural Heritage Through Time - CHT2 (http://cht2-project.eu), funded in the framework of the Joint Programming Initiative on Cultural Heritage (JPI-CH) of the European Commission. Its goal is to develop time-varying 3D products, from landscape to architectural scale, deals with the implementation of the methodology on one of the case studies: the late Roman circus of Milan, built in the era when the city was the capital of the Western Roman Empire (286-402 A.D). The work presented here covers one of the cases in which the physical evidences have now been almost entirely disappeared. The diachronic reconstruction is based on a proper mix of quantitative data originated by 3D surveys at present time, and historical sources like ancient maps, drawings, archaeological reports, archaeological restrictions decrees and old photographs. Such heterogeneous sources have been first georeferenced and then properly integrated according to the methodology defined in the framework of the CHT2 project, to hypothesize a reliable reconstruction of the area in different historical periods.

Zooming in on vibronic structure by lowest-value projection reconstructed 4D coherent spectroscopy

Science.gov (United States)

Harel, Elad

2018-05-01

A fundamental goal of chemical physics is an understanding of microscopic interactions in liquids at and away from equilibrium. In principle, this microscopic information is accessible by high-order and high-dimensionality nonlinear optical measurements. Unfortunately, the time required to execute such experiments increases exponentially with the dimensionality, while the signal decreases exponentially with the order of the nonlinearity. Recently, we demonstrated a non-uniform acquisition method based on radial sampling of the time-domain signal [W. O. Hutson et al., J. Phys. Chem. Lett. 9, 1034 (2018)]. The four-dimensional spectrum was then reconstructed by filtered back-projection using an inverse Radon transform. Here, we demonstrate an alternative reconstruction method based on the statistical analysis of different back-projected spectra which results in a dramatic increase in sensitivity and at least a 100-fold increase in dynamic range compared to conventional uniform sampling and Fourier reconstruction. These results demonstrate that alternative sampling and reconstruction methods enable applications of increasingly high-order and high-dimensionality methods toward deeper insights into the vibronic structure of liquids.

Neural network CT image reconstruction method for small amount of projection data

International Nuclear Information System (INIS)

Ma, X.F.; Fukuhara, M.; Takeda, T.

2000-01-01

This paper presents a new method for two-dimensional image reconstruction by using a multi-layer neural network. Though a conventionally used object function of such a neural network is composed of a sum of squared errors of the output data, we define an object function composed of a sum of squared residuals of an integral equation. By employing an appropriate numerical line integral for this integral equation, we can construct a neural network which can be used for CT image reconstruction for cases with small amount of projection data. We applied this method to some model problems and obtained satisfactory results. This method is especially useful for analyses of laboratory experiments or field observations where only a small amount of projection data is available in comparison with the well-developed medical applications

Neural network CT image reconstruction method for small amount of projection data

CERN Document Server

Ma, X F; Takeda, T

2000-01-01

This paper presents a new method for two-dimensional image reconstruction by using a multi-layer neural network. Though a conventionally used object function of such a neural network is composed of a sum of squared errors of the output data, we define an object function composed of a sum of squared residuals of an integral equation. By employing an appropriate numerical line integral for this integral equation, we can construct a neural network which can be used for CT image reconstruction for cases with small amount of projection data. We applied this method to some model problems and obtained satisfactory results. This method is especially useful for analyses of laboratory experiments or field observations where only a small amount of projection data is available in comparison with the well-developed medical applications.

Analytical algorithm for the generation of polygonal projection data for tomographic reconstruction

International Nuclear Information System (INIS)

Davis, G.R.

1996-01-01

Tomographic reconstruction algorithms and filters can be tested using a mathematical phantom, that is, a computer program which takes numerical data as its input and outputs derived projection data. The input data is usually in the form of pixel ''densities'' over a regular grid, or position and dimensions of simple, geometrical objects. The former technique allows a greater variety of objects to be simulated, but is less suitable in the case when very small (relative to the ray-spacing) features are to be simulated. The second technique is normally used to simulate biological specimens, typically a human skull, modelled as a number of ellipses. This is not suitable for simulating non-biological specimens with features such as straight edges and fine cracks. We have therefore devised an algorithm for simulating objects described as a series of polygons. These polygons, or parts of them, may be smaller than the ray-spacing and there is no limit, except that imposed by computing resources, on the complexity, number or superposition of polygons. A simple test of such a phantom, reconstructed using the filtered back-projection method, revealed reconstruction artefacts not normally seen with ''biological'' phantoms. (orig.)

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

International Nuclear Information System (INIS)

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

2008-01-01

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

External force back-projective composition and globally deformable optimization for 3-D coronary artery reconstruction

International Nuclear Information System (INIS)

Yang, Jian; Cong, Weijian; Fan, Jingfan; Liu, Yue; Wang, Yongtian; Chen, Yang

2014-01-01

The clinical value of the 3D reconstruction of a coronary artery is important for the diagnosis and intervention of cardiovascular diseases. This work proposes a method based on a deformable model for reconstructing coronary arteries from two monoplane angiographic images acquired from different angles. First, an external force back-projective composition model is developed to determine the external force, for which the force distributions in different views are back-projected to the 3D space and composited in the same coordinate system based on the perspective projection principle of x-ray imaging. The elasticity and bending forces are composited as an internal force to maintain the smoothness of the deformable curve. Second, the deformable curve evolves rapidly toward the true vascular centerlines in 3D space and angiographic images under the combination of internal and external forces. Third, densely matched correspondence among vessel centerlines is constructed using a curve alignment method. The bundle adjustment method is then utilized for the global optimization of the projection parameters and the 3D structures. The proposed method is validated on phantom data and routine angiographic images with consideration for space and re-projection image errors. Experimental results demonstrate the effectiveness and robustness of the proposed method for the reconstruction of coronary arteries from two monoplane angiographic images. The proposed method can achieve a mean space error of 0.564 mm and a mean re-projection error of 0.349 mm. (paper)

Columbia River pathway report: phase I of the Hanford Environmental Dose Reconstruction Project

Energy Technology Data Exchange (ETDEWEB)

1991-07-01

This report summarizes the river-pathway portion of the first phase of the Hanford Environmental Dose Reconstruction (HEDR) Project. The HEDR Project is estimating radiation doses that could have been received by the public from the Department of Energy's Hanford Site, in southeastern Washington State. Phase 1 of the river-pathway dose reconstruction effort sought to determine whether dose estimates could be calculated for populations in the area from above the Hanford Site at Priest Rapids Dam to below the site at McNary Dam from January 1964 to December 1966. Of the potential sources of radionuclides from the river, fish consumption was the most important. Doses from drinking water were lower at Pasco than at Richland and lower at Kennewick than at Pasco. The median values of preliminary dose estimates calculated by HEDR are similar to independent, previously published estimates of average doses to Richland residents. Later phases of the HEDR Project will address dose estimates for periods other than 1964--1966 and for populations downstream of McNary Dam. 17 refs., 19 figs., 1 tab.

GPU acceleration of 3D forward and backward projection using separable footprints for X-ray CT image reconstruction

Energy Technology Data Exchange (ETDEWEB)

Wu, Meng; Fessler, Jeffrey A. [Michigan Univ., Ann Arbor, MI (United States). Dept. of Electrical Engineering and Computer Science

2011-07-01

Iterative 3D image reconstruction methods can improve image quality over conventional filtered back projection (FBP) in X-ray computed tomography. However, high computational costs deter the routine use of iterative reconstruction clinically. The separable footprint method for forward and back-projection simplifies the integrals over a detector cell in a way that is quite accurate and also has a relatively efficient CPU implementation. In this project, we implemented the separable footprints method for both forward and backward projection on a graphics processing unit (GPU) with NVDIA's parallel computing architecture (CUDA). This paper describes our GPU kernels for the separable footprint method and simulation results. (orig.)

Restoration of the analytically reconstructed OpenPET images by the method of convex projections

Energy Technology Data Exchange (ETDEWEB)

Tashima, Hideaki; Murayama, Hideo; Yamaya, Taiga [National Institute of Radiological Sciences, Chiba (Japan); Katsunuma, Takayuki; Suga, Mikio [Chiba Univ. (Japan). Graduate School of Engineering; Kinouchi, Shoko [National Institute of Radiological Sciences, Chiba (Japan); Chiba Univ. (Japan). Graduate School of Engineering; Obi, Takashi [Tokyo Institute of Technology (Japan). Interdisciplinary Graduate School of Science and Engineering; Kudo, Hiroyuki [Tsukuba Univ. (Japan). Graduate School of Systems and Information Engineering

2011-07-01

We have proposed the OpenPET geometry which has gaps between detector rings and physically opened field-of-view. The image reconstruction of the OpenPET is classified into an incomplete problem because it does not satisfy the Orlov's condition. Even so, the simulation and experimental studies have shown that applying iterative methods such as the maximum likelihood expectation maximization (ML-EM) algorithm successfully reconstruct images in the gap area. However, the imaging process of the iterative methods in the OpenPET imaging is not clear. Therefore, the aim of this study is to analytically analyze the OpenPET imaging and estimate implicit constraints involved in the iterative methods. To apply explicit constraints in the OpenPET imaging, we used the method of convex projections for restoration of the images reconstructed by the analytical way in which low-frequency components are lost. Numerical simulations showed that the similar restoration effects are involved both in the ML-EM and the method of convex projections. Therefore, the iterative methods have advantageous effect of restoring lost frequency components of the OpenPET imaging. (orig.)

FY 1992 revised task plans for the Hanford Environmental Dose Reconstruction Project

International Nuclear Information System (INIS)

Shipler, D.B.

1992-04-01

The purpose of the Hanford Environmental Dose Reconstruction (HEDR) Project is to estimate radiation doses from Hanford Site operations since 1944 to populations and individuals. The primary objectives of work to be performed in FY 1992 is to determine the appropriate scope (space, time, and radionuclides, pathways and individuals/population groups) and accuracy (level of uncertainty in dose estimates) for the project. Another objective is to use a refined computer model to estimate Native American tribal doses and individual doses for the Hanford Thyroid Disease Study (HTDS). Project scope and accuracy requirements defined in FY 1992 can translated into model and data requirements that must be satisfied during FY 1993

Adaptive algebraic reconstruction technique

International Nuclear Information System (INIS)

Lu Wenkai; Yin Fangfang

2004-01-01

Algebraic reconstruction techniques (ART) are iterative procedures for reconstructing objects from their projections. It is proven that ART can be computationally efficient by carefully arranging the order in which the collected data are accessed during the reconstruction procedure and adaptively adjusting the relaxation parameters. In this paper, an adaptive algebraic reconstruction technique (AART), which adopts the same projection access scheme in multilevel scheme algebraic reconstruction technique (MLS-ART), is proposed. By introducing adaptive adjustment of the relaxation parameters during the reconstruction procedure, one-iteration AART can produce reconstructions with better quality, in comparison with one-iteration MLS-ART. Furthermore, AART outperforms MLS-ART with improved computational efficiency

Initial communication survey results for the Hanford Environmental Dose Reconstruction Project

International Nuclear Information System (INIS)

Beck, D.M.

1991-03-01

To support the public communication efforts of the Technical Steering Panel of the Hanford Environmental Dose Reconstruction (HEDR) Project, a public survey was conducted. The survey was intended to provide information about the public's knowledge and interest in the project and the best ways to communicate project results. Questions about the project were included as part of an omnibus survey conducted by Washington State University. The survey was conducted by phone to Washington State residents in the spring of 1990. This report gives the HEDR-related questions and summary data of responses. Questions associated with the HEDR Project were grouped into four categories: knowledge of the HEDR Project; interest in the project; preferred ways of receiving information about the project (including public information meetings, a newsletter mailed to homes, presentations to civic groups in the respondent's community, a computer bulletin board respondent could access with a modem, information displays at public buildings and shopping malls, and an information video sent to respondent); and level of concern over past exposure from Hanford operations. Questions abut whom state residents are most likely to trust about radiation issues were also part of the omnibus survey, and responses are included in this report

An electron tomography algorithm for reconstructing 3D morphology using surface tangents of projected scattering interfaces

Science.gov (United States)

Petersen, T. C.; Ringer, S. P.

2010-03-01

Upon discerning the mere shape of an imaged object, as portrayed by projected perimeters, the full three-dimensional scattering density may not be of particular interest. In this situation considerable simplifications to the reconstruction problem are possible, allowing calculations based upon geometric principles. Here we describe and provide an algorithm which reconstructs the three-dimensional morphology of specimens from tilt series of images for application to electron tomography. Our algorithm uses a differential approach to infer the intersection of projected tangent lines with surfaces which define boundaries between regions of different scattering densities within and around the perimeters of specimens. Details of the algorithm implementation are given and explained using reconstruction calculations from simulations, which are built into the code. An experimental application of the algorithm to a nano-sized Aluminium tip is also presented to demonstrate practical analysis for a real specimen. Program summaryProgram title: STOMO version 1.0 Catalogue identifier: AEFS_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEFS_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 2988 No. of bytes in distributed program, including test data, etc.: 191 605 Distribution format: tar.gz Programming language: C/C++ Computer: PC Operating system: Windows XP RAM: Depends upon the size of experimental data as input, ranging from 200 Mb to 1.5 Gb Supplementary material: Sample output files, for the test run provided, are available. Classification: 7.4, 14 External routines: Dev-C++ ( http://www.bloodshed.net/devcpp.html) Nature of problem: Electron tomography of specimens for which conventional back projection may fail and/or data for which there is a limited angular

Impact of posterior rhabdosphincter reconstruction during robot-assisted radical prostatectomy: retrospective analysis of time to continence.

Science.gov (United States)

Woo, Jason R; Shikanov, Sergey; Zorn, Kevin C; Shalhav, Arieh L; Zagaja, Gregory P

2009-12-01

Posterior rhabdosphincter (PR) reconstruction during robot-assisted radical prostatectomy (RARP) was introduced in an attempt to improve postoperative continence. In the present study, we evaluate time to achieve continence in patients who are undergoing RARP with and without PR reconstruction. A prospective RARP database was searched for most recent cases that were accomplished with PR reconstruction (group 1, n = 69) or with standard technique (group 2, n = 63). We performed the analysis applying two definitions of continence: 0 pads per day or 0-1 security pad per day. Patients were evaluated by telephone interview. Statistical analysis was carried out using the Kaplan-Meier method and log-rank test. With PR reconstruction, continence was improved when defined as 0-1 security pad per day (median time of 90 vs 150 days; P = 0.01). This difference did not achieve statistical significance when continence was defined as 0 pads per day (P = 0.12). A statistically significant improvement in continence rate and time to achieve continence is seen in patients who are undergoing PR reconstruction during RARP, with continence defined as 0-1 security/safety pad per day. A larger, prospective and randomized study is needed to better understand the impact of this technique on postoperative continence.

CT image reconstruction of steel pipe section from few projections using the method of rotating polar-coordinate

International Nuclear Information System (INIS)

Peng Shuaijun; Wu Zhifang

2008-01-01

Fast online inspection in steel pipe production is a big challenge. Radiographic CT imaging technology, a high performance non-destructive testing method, is quite appropriate for inspection and quality control of steel pipes. The method of rotating polar-coordinate is used to reconstruct the steel pipe section from few projections with the purpose of inspecting it online. It reduces the projection number needed and the data collection time, and accelerates the reconstruction algorithm and saves the inspection time evidently. The results of simulation experiment and actual experiment indicate that the image quality and reconstruction time of rotating polar-coordinate method meet the requirements of inspecting the steel tube section online basically. The study is of some theoretical significance and the method is expected to be widely used in practice. (authors)

Enhancing breast projection in autologous reconstruction using the St Andrew's coning technique and 3D volumetric analysis.

Science.gov (United States)

Chae, Michael P; Rozen, Warren Matthew; Patel, Nakul Gamanlal; Hunter-Smith, David J; Ramakrishnan, Venkat

2017-12-01

An increasing number of women undergo mastectomy for breast cancer and post-mastectomy autologous breast reconstruction has been shown to significantly improve the psychosexual wellbeing of the patients. A goal of treatment is to achieve symmetry and projection to match the native breast, and/or the contralateral breast in the case of a unilateral reconstruction. Autologous reconstruction, particularly with the deep inferior epigastric artery perforator (DIEP) flap, is particularly advantageous as it can be manipulated to mimic the shape and turgor of the native breast. However, very few techniques of shaping the breast conus when insetting the DIEP flap to enhance aesthetic outcome have been reported to date. With the aide of three-dimension (3D) photography and 3D-printed mirrored image of the contralateral breast as a guide intraoperatively, we describe our St Andrew's coning technique to create a personalized flap projection. We report a prospective case series of 3 delayed unilateral breast reconstructions where symmetrization procedure to the contralateral breast was not indicated. Using a commercial 3D scanner (VECTRA XR, Canfield Scientific), the breast region was imaged. The mirrored image was 3D-printed in-house using a desktop 3D printer. In all cases, projection of the breast mound was able to be safely achieved, with a demonstrated central volume (or 'cone') able to be highlighted on imaging and a 3D printed breast. A 3D print of the contralateral breast was able to be used intraoperatively to guide the operative approach. The St Andrew's coning technique is a useful aesthetic maneuver for achieving breast projection during DIEP flap breast reconstruction, with 3D imaging techniques able to assist in perioperative assessment of breast volume.

Fast backprojection-based reconstruction of spectral-spatial EPR images from projections with the constant sweep of a magnetic field.

Science.gov (United States)

Komarov, Denis A; Hirata, Hiroshi

2017-08-01

In this paper, we introduce a procedure for the reconstruction of spectral-spatial EPR images using projections acquired with the constant sweep of a magnetic field. The application of a constant field-sweep and a predetermined data sampling rate simplifies the requirements for EPR imaging instrumentation and facilitates the backprojection-based reconstruction of spectral-spatial images. The proposed approach was applied to the reconstruction of a four-dimensional numerical phantom and to actual spectral-spatial EPR measurements. Image reconstruction using projections with a constant field-sweep was three times faster than the conventional approach with the application of a pseudo-angle and a scan range that depends on the applied field gradient. Spectral-spatial EPR imaging with a constant field-sweep for data acquisition only slightly reduces the signal-to-noise ratio or functional resolution of the resultant images and can be applied together with any common backprojection-based reconstruction algorithm. Copyright © 2017 Elsevier Inc. All rights reserved.

Tomographic reconstruction of binary fields

International Nuclear Information System (INIS)

Roux, Stéphane; Leclerc, Hugo; Hild, François

2012-01-01

A novel algorithm is proposed for reconstructing binary images from their projection along a set of different orientations. Based on a nonlinear transformation of the projection data, classical back-projection procedures can be used iteratively to converge to the sought image. A multiscale implementation allows for a faster convergence. The algorithm is tested on images up to 1 Mb definition, and an error free reconstruction is achieved with a very limited number of projection data, saving a factor of about 100 on the number of projections required for classical reconstruction algorithms.

FY 1991 Task plans for the Hanford Environmental Dose Reconstruction Project

International Nuclear Information System (INIS)

1991-04-01

The purpose of the Hanford Environmental Dose Reconstruction (HEDR) Project is to estimate radiation doses from Hanford Site operations since 1944 to populations and individuals. The objectives of work in Fiscal Year (FY) 1991 are to analyze data and models used in Phase 1 and restructure the models to increase accuracy and reduce uncertainty in dose estimation capability. Databases will be expanded and efforts will begin to determine the appropriate scope (space, time, radionuclides, pathways and individuals/population groups) and accuracy (level of uncertainty in dose estimates) for the project. Project scope and accuracy requirements, once defined, can be translated into additional model and data requirements later in the project. Task plans for FY 1991 have been prepared based on activities approved by the Technical Steering Panel (TSP) in October 1990 and mid-year revisions discussed at the TSP planning/budget workshop in February 1991. The activities can be divided into two broad categories: (1) model and data development and evaluation, (2) project, technical and communication support. 3 figs., 1 tab

Entropy and transverse section reconstruction

International Nuclear Information System (INIS)

Gullberg, G.T.

1976-01-01

A new approach to the reconstruction of a transverse section using projection data from multiple views incorporates the concept of maximum entropy. The principle of maximizing information entropy embodies the assurance of minimizing bias or prejudice in the reconstruction. Using maximum entropy is a necessary condition for the reconstructed image. This entropy criterion is most appropriate for 3-D reconstruction of objects from projections where the system is underdetermined or the data are limited statistically. This is the case in nuclear medicine time limitations in patient studies do not yield sufficient projections

Methods of X-ray CT image reconstruction from few projections; Methodes de reconstruction d'images a partir d'un faible nombre de projections en tomographie par rayons X

Energy Technology Data Exchange (ETDEWEB)

Wang, H.

2011-10-24

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

Coronary CT angiography: Comparison of a novel iterative reconstruction with filtered back projection for reconstruction of low-dose CT—Initial experience

International Nuclear Information System (INIS)

Takx, Richard A.P.; Schoepf, U. Joseph; Moscariello, Antonio; Das, Marco; Rowe, Garrett; Schoenberg, Stefan O.; Fink, Christian; Henzler, Thomas

2013-01-01

Objective: To prospectively compare subjective and objective image quality in 20% tube current coronary CT angiography (cCTA) datasets between an iterative reconstruction algorithm (SAFIRE) and traditional filtered back projection (FBP). Materials and methods: Twenty patients underwent a prospectively ECG-triggered dual-step cCTA protocol using 2nd generation dual-source CT (DSCT). CT raw data was reconstructed using standard FBP at full-dose (Group 1 a) and 80% tube current reduced low-dose (Group 1 b). The low-dose raw data was additionally reconstructed using iterative raw data reconstruction (Group 2 ). Attenuation and image noise were measured in three regions of interest and signal-to-noise-ratio (SNR) as well as contrast-to-noise-ratio (CNR) was calculated. Subjective diagnostic image quality was evaluated using a 4-point Likert scale. Results: Mean image noise of group 2 was lowered by 22% on average when compared to group 1 b (p 2 compared to group 1 b (p 2 (1.88 ± 0.63) was also rated significantly higher when compared to group 1 b (1.58 ± 0.63, p = 0.004). Conclusions: Image quality of 80% tube current reduced iteratively reconstructed cCTA raw data is significantly improved when compared to standard FBP and consequently may improve the diagnostic accuracy of cCTA

Development of an image reconstruction algorithm for a few number of projection data

International Nuclear Information System (INIS)

Vieira, Wilson S.; Brandao, Luiz E.; Braz, Delson

2007-01-01

An image reconstruction algorithm was developed for specific cases of radiotracer applications in industry (rotating cylindrical mixers), involving a very few number of projection data. The algorithm was planned for imaging radioactive isotope distributions around the center of circular planes. The method consists of adapting the original expectation maximization algorithm (EM) to solve the ill-posed emission tomography inverse problem in order to reconstruct transversal 2D images of an object with only four projections. To achieve this aim, counts of photons emitted by selected radioactive sources in the plane, after they had been simulated using the commercial software MICROSHIELD 5.05, constitutes the projections and a computational code (SPECTEM) was developed to generate activity vectors or images related to those sources. SPECTEM is flexible to support simultaneous changes of the detectors's geometry, the medium under investigation and the properties of the gamma radiation. As a consequence of the code had been followed correctly the proposed method, good results were obtained and they encouraged us to continue the next step of the research: the validation of SPECTEM utilizing experimental data to check its real performance. We aim this code will improve considerably radiotracer methodology, making easier the diagnosis of fails in industrial processes. (author)

Development of an image reconstruction algorithm for a few number of projection data

Energy Technology Data Exchange (ETDEWEB)

Vieira, Wilson S.; Brandao, Luiz E. [Instituto de Engenharia Nuclear (IEN-CNEN/RJ), Rio de Janeiro , RJ (Brazil)]. E-mails: wilson@ien.gov.br; brandao@ien.gov.br; Braz, Delson [Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil). Coordenacao dos Programa de Pos-graduacao de Engenharia (COPPE). Lab. de Instrumentacao Nuclear]. E-mail: delson@mailhost.lin.ufrj.br

2007-07-01

An image reconstruction algorithm was developed for specific cases of radiotracer applications in industry (rotating cylindrical mixers), involving a very few number of projection data. The algorithm was planned for imaging radioactive isotope distributions around the center of circular planes. The method consists of adapting the original expectation maximization algorithm (EM) to solve the ill-posed emission tomography inverse problem in order to reconstruct transversal 2D images of an object with only four projections. To achieve this aim, counts of photons emitted by selected radioactive sources in the plane, after they had been simulated using the commercial software MICROSHIELD 5.05, constitutes the projections and a computational code (SPECTEM) was developed to generate activity vectors or images related to those sources. SPECTEM is flexible to support simultaneous changes of the detectors's geometry, the medium under investigation and the properties of the gamma radiation. As a consequence of the code had been followed correctly the proposed method, good results were obtained and they encouraged us to continue the next step of the research: the validation of SPECTEM utilizing experimental data to check its real performance. We aim this code will improve considerably radiotracer methodology, making easier the diagnosis of fails in industrial processes. (author)

Image reconstruction from projections and its application in emission computer tomography

International Nuclear Information System (INIS)

Kuba, Attila; Csernay, Laszlo

1989-01-01

Computer tomography is an imaging technique for producing cross sectional images by reconstruction from projections. Its two main branches are called transmission and emission computer tomography, TCT and ECT, resp. After an overview of the theory and practice of TCT and ECT, the first Hungarian ECT type MB 9300 SPECT consisting of a gamma camera and Ketronic Medax N computer is described, and its applications to radiological patient observations are discussed briefly. (R.P.) 28 refs.; 4 figs

Reconstruction of computed tomographic image from a few x-ray projections by means of accelerative gradient method

International Nuclear Information System (INIS)

Kobayashi, Fujio; Yamaguchi, Shoichiro

1982-01-01

A method of the reconstruction of computed tomographic images was proposed to reduce the exposure dose to X-ray. The method is the small number of X-ray projection method by accelerative gradient method. The procedures of computation are described. The algorithm of these procedures is simple, the convergence of the computation is fast, and the required memory capacity is small. Numerical simulation was carried out to conform the validity of this method. A sample of simple shape was considered, projection data were given, and the images were reconstructed from 6 views. Good results were obtained, and the method is considered to be useful. (Kato, T.)

Integration of models for the Hanford Environmental Dose Reconstruction Project

International Nuclear Information System (INIS)

Napier, B.A.

1991-01-01

The objective of the Hanford Environmental Dose Reconstruction Project is to estimate the radiation dose that individuals could have received as a result of emissions from nuclear operations at Hanford since 1944. The objective of phase 1 of the project was to demonstrate through calculations that adequate models and support data exist or could be developed to allow realistic estimations of doses to individuals from releases of radionuclides to the environment that occurred as long as 45 years ago. Much of the data used in phase 1 was preliminary; therefore, the doses calculated must be considered preliminary approximations. This paper describes the integration of various models that was implemented for initial computer calculations. Models were required for estimating the quantity of radioactive material released, for evaluating its transport through the environment, for estimating human exposure, and for evaluating resultant doses

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

International Nuclear Information System (INIS)

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

2004-01-01

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

A sparsity-based iterative algorithm for reconstruction of micro-CT images from highly undersampled projection datasets obtained with a synchrotron X-ray source

Science.gov (United States)

Melli, S. Ali; Wahid, Khan A.; Babyn, Paul; Cooper, David M. L.; Gopi, Varun P.

2016-12-01

Synchrotron X-ray Micro Computed Tomography (Micro-CT) is an imaging technique which is increasingly used for non-invasive in vivo preclinical imaging. However, it often requires a large number of projections from many different angles to reconstruct high-quality images leading to significantly high radiation doses and long scan times. To utilize this imaging technique further for in vivo imaging, we need to design reconstruction algorithms that reduce the radiation dose and scan time without reduction of reconstructed image quality. This research is focused on using a combination of gradient-based Douglas-Rachford splitting and discrete wavelet packet shrinkage image denoising methods to design an algorithm for reconstruction of large-scale reduced-view synchrotron Micro-CT images with acceptable quality metrics. These quality metrics are computed by comparing the reconstructed images with a high-dose reference image reconstructed from 1800 equally spaced projections spanning 180°. Visual and quantitative-based performance assessment of a synthetic head phantom and a femoral cortical bone sample imaged in the biomedical imaging and therapy bending magnet beamline at the Canadian Light Source demonstrates that the proposed algorithm is superior to the existing reconstruction algorithms. Using the proposed reconstruction algorithm to reduce the number of projections in synchrotron Micro-CT is an effective way to reduce the overall radiation dose and scan time which improves in vivo imaging protocols.

Reconstructing sea level from paleo and projected temperatures 200 to 2100 AD

DEFF Research Database (Denmark)

Grinsted, Aslak; Moore, John; Jevrejeva, Svetlana

2010-01-01

-proxy reconstructions assuming that the established relationship between temperature and sea level holds from 200 to 2100 ad. Over the last 2,000 years minimum sea level (-19 to -26 cm) occurred around 1730 ad, maximum sea level (12–21 cm) around 1150 AD. Sea level 2090–2099 is projected to be 0.9 to 1.3 m for the A1B...

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

International Nuclear Information System (INIS)

Zhang Junan; Yin Fangfang

2007-01-01

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

Precise 3D track reconstruction algorithm for the ICARUS T600 liquid argon time projection chamber detector

CERN Document Server

Antonello, M

2013-01-01

Liquid Argon Time Projection Chamber (LAr TPC) detectors offer charged particle imaging capability with remarkable spatial resolution. Precise event reconstruction procedures are critical in order to fully exploit the potential of this technology. In this paper we present a new, general approach of three-dimensional reconstruction for the LAr TPC with a practical application to track reconstruction. The efficiency of the method is evaluated on a sample of simulated tracks. We present also the application of the method to the analysis of real data tracks collected during the ICARUS T600 detector operation with the CNGS neutrino beam.

Precise 3D Track Reconstruction Algorithm for the ICARUS T600 Liquid Argon Time Projection Chamber Detector

Directory of Open Access Journals (Sweden)

M. Antonello

2013-01-01

Full Text Available Liquid Argon Time Projection Chamber (LAr TPC detectors offer charged particle imaging capability with remarkable spatial resolution. Precise event reconstruction procedures are critical in order to fully exploit the potential of this technology. In this paper we present a new, general approach to 3D reconstruction for the LAr TPC with a practical application to the track reconstruction. The efficiency of the method is evaluated on a sample of simulated tracks. We present also the application of the method to the analysis of stopping particle tracks collected during the ICARUS T600 detector operation with the CNGS neutrino beam.

Jini service to reconstruct tomographic data

Science.gov (United States)

Knoll, Peter; Mirzaei, S.; Koriska, K.; Koehn, H.

2002-06-01

A number of imaging systems rely on the reconstruction of a 3- dimensional model from its projections through the process of computed tomography (CT). In medical imaging, for example magnetic resonance imaging (MRI), positron emission tomography (PET), and Single Computer Tomography (SPECT) acquire two-dimensional projections of a three dimensional projections of a three dimensional object. In order to calculate the 3-dimensional representation of the object, i.e. its voxel distribution, several reconstruction algorithms have been developed. Currently, mainly two reconstruct use: the filtered back projection(FBP) and iterative methods. Although the quality of iterative reconstructed SPECT slices is better than that of FBP slices, such iterative algorithms are rarely used for clinical routine studies because of their low availability and increased reconstruction time. We used Jini and a self-developed iterative reconstructions algorithm to design and implement a Jini reconstruction service. With this service, the physician selects the patient study from a database and a Jini client automatically discovers the registered Jini reconstruction services in the department's Intranet. After downloading the proxy object the this Jini service, the SPECT acquisition data are reconstructed. The resulting transaxial slices are visualized using a Jini slice viewer, which can be used for various imaging modalities.

Investigation of various reconstruction parameters for algebraic reconstruction technique in a newly developed chest digital tomosynthesis

International Nuclear Information System (INIS)

Lee, H.; Choi, S.; Kim, Y.-S.; Park, H.-S.; Seo, C.-W.; Kim, H.-J.; Lee, D.; Lee, Y.

2017-01-01

Chest digital tomosynthesis (CDT) is a promising new modality that provides 3D information by reconstructing limited projection views. CDT systems have been developed to improve the limitations of conventional radiography such as image degradation and low sensitivity. However, the development of reconstruction methods is challenging because of the limited projection views within various angular ranges. Optimization of reconstruction parameters for various reconsturction methods in CDT system also is needed. The purpose of this study was to investigate the feasibility of algebraic reconstruction technique (ART) method, and to evaluate the effect of the reconstruction parameters for our newly developed CDT system. We designed ART method with 41 projection views over an angular range of ±20°. To investigate the effect of reconstruction parameters, we measured the contrast-to-noise ratio (CNR), artifact spread function (ASF), and quality factor (QF) using LUNGMAN phantom included tumors. We found that the proper choice of reconstruction parameters such as relaxation parameter, initial guess, and number of iterations improved the quality of reconstructed images from the same projection views. Optimal values of ART relaxation parameter with uniform (UI) and back-projection (BP) initial guesses were 0.4 and 0.6, respectively. BP initial guess improved image quality in comparison with UI initial guess, in terms of providing a higher CNR and QF values with a faster speed. CNR and QF values improved with increasing number of iteration. Particularly, ART method with BP initial guess (when β = 0.6) after 3-terations provide satisfactory reconstructed image. In conclusion, the use of ART method with proper reconstruction parameters provided better image quality than FBP method as well as conventional radiography. These results indicated that the ART method with optimal reconstruction parameters could improve image quality for nodule detection using the CDT system.

Investigation of various reconstruction parameters for algebraic reconstruction technique in a newly developed chest digital tomosynthesis

Science.gov (United States)

Lee, H.; Choi, S.; Lee, D.; Kim, Y.-s.; Park, H.-S.; Lee, Y.; Seo, C.-W.; Kim, H.-J.

2017-08-01

Chest digital tomosynthesis (CDT) is a promising new modality that provides 3D information by reconstructing limited projection views. CDT systems have been developed to improve the limitations of conventional radiography such as image degradation and low sensitivity. However, the development of reconstruction methods is challenging because of the limited projection views within various angular ranges. Optimization of reconstruction parameters for various reconsturction methods in CDT system also is needed. The purpose of this study was to investigate the feasibility of algebraic reconstruction technique (ART) method, and to evaluate the effect of the reconstruction parameters for our newly developed CDT system. We designed ART method with 41 projection views over an angular range of ±20°. To investigate the effect of reconstruction parameters, we measured the contrast-to-noise ratio (CNR), artifact spread function (ASF), and quality factor (QF) using LUNGMAN phantom included tumors. We found that the proper choice of reconstruction parameters such as relaxation parameter, initial guess, and number of iterations improved the quality of reconstructed images from the same projection views. Optimal values of ART relaxation parameter with uniform (UI) and back-projection (BP) initial guesses were 0.4 and 0.6, respectively. BP initial guess improved image quality in comparison with UI initial guess, in terms of providing a higher CNR and QF values with a faster speed. CNR and QF values improved with increasing number of iteration. Particularly, ART method with BP initial guess (when β = 0.6) after 3-terations provide satisfactory reconstructed image. In conclusion, the use of ART method with proper reconstruction parameters provided better image quality than FBP method as well as conventional radiography. These results indicated that the ART method with optimal reconstruction parameters could improve image quality for nodule detection using the CDT system.

Projected shell model study of yrast states of neutron-deficient odd-mass Pr nuclei

International Nuclear Information System (INIS)

Ibanez-Sandoval, A.; Ortiz, M. E.; Velazquez, V.; Galindo-Uribarri, A.; Hess, P. O.; Sun, Y.

2011-01-01

A wide variety of modern instruments allow us to study neutron-deficient nuclei in the A=130 mass region. Highly deformed nuclei have been found in this region, providing opportunities to study the deformed rotational bands. The description of the 125,127,129,131,133 Pr isotopes with the projected shell model is presented in this paper. Good agreement between theory and experiment is obtained and some characteristics are discussed, including the dynamic moment of inertia J (2) , kinetic moment of inertia J (1) , the crossing of rotational bands, and backbending effects.

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

International Nuclear Information System (INIS)

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

2014-01-01

Purpose: Respiratory signal, binning method, and reconstruction algorithm are three major controllable factors affecting image quality in thoracic 4D cone-beam CT (4D-CBCT), which is widely used in image guided radiotherapy (IGRT). Previous studies have investigated each of these factors individually, but no integrated sensitivity analysis has been performed. In addition, projection angular spacing is also a key factor in reconstruction, but how it affects image quality is not obvious. An investigation of the impacts of these four factors on image quality can help determine the most effective strategy in improving 4D-CBCT for IGRT. Methods: Fourteen 4D-CBCT patient projection datasets with various respiratory motion features were reconstructed with the following controllable factors: (i) respiratory signal (real-time position management, projection image intensity analysis, or fiducial marker tracking), (ii) binning method (phase, displacement, or equal-projection-density displacement binning), and (iii) reconstruction algorithm [Feldkamp–Davis–Kress (FDK), McKinnon–Bates (MKB), or adaptive-steepest-descent projection-onto-convex-sets (ASD-POCS)]. The image quality was quantified using signal-to-noise ratio (SNR), contrast-to-noise ratio, and edge-response width in order to assess noise/streaking and blur. The SNR values were also analyzed with respect to the maximum, mean, and root-mean-squared-error (RMSE) projection angular spacing to investigate how projection angular spacing affects image quality. Results: The choice of respiratory signals was found to have no significant impact on image quality. Displacement-based binning was found to be less prone to motion artifacts compared to phase binning in more than half of the cases, but was shown to suffer from large interbin image quality variation and large projection angular gaps. Both MKB and ASD-POCS resulted in noticeably improved image quality almost 100% of the time relative to FDK. In addition, SNR

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

Energy Technology Data Exchange (ETDEWEB)

Shieh, Chun-Chien [Radiation Physics Laboratory, Sydney Medical School, University of Sydney, NSW 2006, Australia and Institute of Medical Physics, School of Physics, University of Sydney, NSW 2006 (Australia); Kipritidis, John; O’Brien, Ricky T.; Keall, Paul J., E-mail: paul.keall@sydney.edu.au [Radiation Physics Laboratory, Sydney Medical School, University of Sydney, NSW 2006 (Australia); Kuncic, Zdenka [Institute of Medical Physics, School of Physics, University of Sydney, NSW 2006 (Australia)

2014-04-15

Purpose: Respiratory signal, binning method, and reconstruction algorithm are three major controllable factors affecting image quality in thoracic 4D cone-beam CT (4D-CBCT), which is widely used in image guided radiotherapy (IGRT). Previous studies have investigated each of these factors individually, but no integrated sensitivity analysis has been performed. In addition, projection angular spacing is also a key factor in reconstruction, but how it affects image quality is not obvious. An investigation of the impacts of these four factors on image quality can help determine the most effective strategy in improving 4D-CBCT for IGRT. Methods: Fourteen 4D-CBCT patient projection datasets with various respiratory motion features were reconstructed with the following controllable factors: (i) respiratory signal (real-time position management, projection image intensity analysis, or fiducial marker tracking), (ii) binning method (phase, displacement, or equal-projection-density displacement binning), and (iii) reconstruction algorithm [Feldkamp–Davis–Kress (FDK), McKinnon–Bates (MKB), or adaptive-steepest-descent projection-onto-convex-sets (ASD-POCS)]. The image quality was quantified using signal-to-noise ratio (SNR), contrast-to-noise ratio, and edge-response width in order to assess noise/streaking and blur. The SNR values were also analyzed with respect to the maximum, mean, and root-mean-squared-error (RMSE) projection angular spacing to investigate how projection angular spacing affects image quality. Results: The choice of respiratory signals was found to have no significant impact on image quality. Displacement-based binning was found to be less prone to motion artifacts compared to phase binning in more than half of the cases, but was shown to suffer from large interbin image quality variation and large projection angular gaps. Both MKB and ASD-POCS resulted in noticeably improved image quality almost 100% of the time relative to FDK. In addition, SNR

A Dynamic Multi-Projection-Contour Approximating Framework for the 3D Reconstruction of Buildings by Super-Generalized Optical Stereo-Pairs.

Science.gov (United States)

Yan, Yiming; Su, Nan; Zhao, Chunhui; Wang, Liguo

2017-09-19

In this paper, a novel framework of the 3D reconstruction of buildings is proposed, focusing on remote sensing super-generalized stereo-pairs (SGSPs). As we all know, 3D reconstruction cannot be well performed using nonstandard stereo pairs, since reliable stereo matching could not be achieved when the image-pairs are collected at a great difference of views, and we always failed to obtain dense 3D points for regions of buildings, and cannot do further 3D shape reconstruction. We defined SGSPs as two or more optical images collected in less constrained views but covering the same buildings. It is even more difficult to reconstruct the 3D shape of a building by SGSPs using traditional frameworks. As a result, a dynamic multi-projection-contour approximating (DMPCA) framework was introduced for SGSP-based 3D reconstruction. The key idea is that we do an optimization to find a group of parameters of a simulated 3D model and use a binary feature-image that minimizes the total differences between projection-contours of the building in the SGSPs and that in the simulated 3D model. Then, the simulated 3D model, defined by the group of parameters, could approximate the actual 3D shape of the building. Certain parameterized 3D basic-unit-models of typical buildings were designed, and a simulated projection system was established to obtain a simulated projection-contour in different views. Moreover, the artificial bee colony algorithm was employed to solve the optimization. With SGSPs collected by the satellite and our unmanned aerial vehicle, the DMPCA framework was verified by a group of experiments, which demonstrated the reliability and advantages of this work.

MO-FG-204-08: Optimization-Based Image Reconstruction From Unevenly Distributed Sparse Projection Views

International Nuclear Information System (INIS)

Xie, Huiqiao; Yang, Yi; Tang, Xiangyang; Niu, Tianye; Ren, Yi

2015-01-01

Purpose: Optimization-based reconstruction has been proposed and investigated for reconstructing CT images from sparse views, as such the radiation dose can be substantially reduced while maintaining acceptable image quality. The investigation has so far focused on reconstruction from evenly distributed sparse views. Recognizing the clinical situations wherein only unevenly sparse views are available, e.g., image guided radiation therapy, CT perfusion and multi-cycle cardiovascular imaging, we investigate the performance of optimization-based image reconstruction from unevenly sparse projection views in this work. Methods: The investigation is carried out using the FORBILD and an anthropomorphic head phantoms. In the study, 82 views, which are evenly sorted out from a full (360°) axial CT scan consisting of 984 views, form sub-scan I. Another 82 views are sorted out in a similar manner to form sub-scan II. As such, a CT scan with sparse (164) views at 1:6 ratio are formed. By shifting the two sub-scans relatively in view angulation, a CT scan with unevenly distributed sparse (164) views at 1:6 ratio are formed. An optimization-based method is implemented to reconstruct images from the unevenly distributed views. By taking the FBP reconstruction from the full scan (984 views) as the reference, the root mean square (RMS) between the reference and the optimization-based reconstruction is used to evaluate the performance quantitatively. Results: In visual inspection, the optimization-based method outperforms the FBP substantially in the reconstruction from unevenly distributed, which are quantitatively verified by the RMS gauged globally and in ROIs in both the FORBILD and anthropomorphic head phantoms. The RMS increases with increasing severity in the uneven angular distribution, especially in the case of anthropomorphic head phantom. Conclusion: The optimization-based image reconstruction can save radiation dose up to 12-fold while providing acceptable image quality

Kuwaiti reconstruction project unprecedented in size, complexity

Energy Technology Data Exchange (ETDEWEB)

Tippee, B.

1993-03-15

There had been no challenge like it: a desert emirate ablaze; its main city sacked; the economically crucial oil industry devastated; countryside shrouded in smoke from oil well fires and littered with unexploded ordnance, disabled military equipment, and unignited crude oil. Like the well-documented effort that brought 749 burning wells under control in less than 7 months, Kuwaiti reconstruction had no precedent. Unlike the firefight, reconstruction is no-where complete. It nevertheless has placed two of three refineries back on stream, restored oil production to preinvasion levels, and repaired or rebuilt 17 of 26 oil field gathering stations. Most of the progress has come since the last well fire went out on Nov. 6, 1991. Expatriates in Kuwait since the days of Al-Awda- the return,' in Arabic- attribute much of the rapid progress under Al-Tameer- the reconstruction'- to decisions and preparations made while the well fires still raged. The article describes the planning for Al-Awda, reentering the country, drilling plans, facilities reconstruction, and special problems.

Sub-sequence Factorization-an Effective Approach for Projective Reconstruction under Occlusion

Institute of Scientific and Technical Information of China (English)

LU Le; HU Zhanyi

2001-01-01

Projective reconstruction is a key step for 3D metric reconstruction from a sequence of images captured by an uncalibrated camera. Due to its inherent robustness, the factorization method is widely used in literatures. However, the main shortcoming of the standard factorization method is that it requires the corresponding points to appear across ALL the images. When large changes of view angles occur in the image sequence, or the scene is easy to be self-occluded, nearly it will be very difficult to have some corresponding points visible across all the images. But it is much easier for only several images to have enough correspondences required by factorization method. These images are called as a subsequence in the whole image set. In this paper,a sub-sequence factorization method is proposed to cope with the problem. The basic principle of the sub-sequence factorization method is to divide a long image sequence into several short subsequences according to its spatial continuity, and the standard factorization method is employed for each subsequence.Then, a novel alignment process is invoked to transform different reconstructions under different subsequences into one reference coordinates system. It is more practical as it only demands that there are enough correspondences in each subsequence, not the whole sequence. The proposed sub-sequence factorization method preserves the robustness aspect embedded in the standard factorization method. The experiments on synthetic and real images validate our proposed new method.

FY 1992 task plans for the Hanford Environmental Dose Reconstruction Project

International Nuclear Information System (INIS)

1991-10-01

Phase 1 of the HEDR Project was designed to develop and demonstrate a method for estimating radiation doses people may have received from Hanford Site operations since 1944. The method researchers developed relied on a variety of measured and reconstructed data as input to a modular computer model that generates dose estimates and their uncertainties. As part of Phase 1, researchers used the reconstructed data and computer model to calculate preliminary dose estimates for populations from limited radionuclides, in a limited geographical area and time period. Phase 1 ended in FY 1990. In February 1991, the TSP decided to shift the project planning approach away from phases--which were centered around completion of major portions of technical activities--to individual fiscal years (FYs), which span October of one year through September of the next. Therefore, activities that were previously designated to occur in phases are now designated in an integrated schedule to occur in one or more of the next fiscal years into FY 1995. Task plans are updated every 6 months. In FY 1992, scientists will continue to improve Phase 1 data and models to calculate more accurate and precise dose estimates. The plan for FY 1992 has been prepared based on activities and budgets approved by the Technical Steering Panel (TSP) at its meeting on August 19--20, 1991. The activities can be divided into four categories: (1) model and data evaluation activities, (2) additional dose estimates, (3) model and data development activities, and (4) technical and communication support. 3 figs., 2 tabs

Reduced aliasing artifacts using shaking projection k-space sampling trajectory

Science.gov (United States)

Zhu, Yan-Chun; Du, Jiang; Yang, Wen-Chao; Duan, Chai-Jie; Wang, Hao-Yu; Gao, Song; Bao, Shang-Lian

2014-03-01

Radial imaging techniques, such as projection-reconstruction (PR), are used in magnetic resonance imaging (MRI) for dynamic imaging, angiography, and short-T2 imaging. They are less sensitive to flow and motion artifacts, and support fast imaging with short echo times. However, aliasing and streaking artifacts are two main sources which degrade radial imaging quality. For a given fixed number of k-space projections, data distributions along radial and angular directions will influence the level of aliasing and streaking artifacts. Conventional radial k-space sampling trajectory introduces an aliasing artifact at the first principal ring of point spread function (PSF). In this paper, a shaking projection (SP) k-space sampling trajectory was proposed to reduce aliasing artifacts in MR images. SP sampling trajectory shifts the projection alternately along the k-space center, which separates k-space data in the azimuthal direction. Simulations based on conventional and SP sampling trajectories were compared with the same number projections. A significant reduction of aliasing artifacts was observed using the SP sampling trajectory. These two trajectories were also compared with different sampling frequencies. A SP trajectory has the same aliasing character when using half sampling frequency (or half data) for reconstruction. SNR comparisons with different white noise levels show that these two trajectories have the same SNR character. In conclusion, the SP trajectory can reduce the aliasing artifact without decreasing SNR and also provide a way for undersampling reconstruction. Furthermore, this method can be applied to three-dimensional (3D) hybrid or spherical radial k-space sampling for a more efficient reduction of aliasing artifacts.

Reduced aliasing artifacts using shaking projection k-space sampling trajectory

International Nuclear Information System (INIS)

Zhu Yan-Chun; Yang Wen-Chao; Wang Hao-Yu; Gao Song; Bao Shang-Lian; Du Jiang; Duan Chai-Jie

2014-01-01

Radial imaging techniques, such as projection-reconstruction (PR), are used in magnetic resonance imaging (MRI) for dynamic imaging, angiography, and short-T2 imaging. They are less sensitive to flow and motion artifacts, and support fast imaging with short echo times. However, aliasing and streaking artifacts are two main sources which degrade radial imaging quality. For a given fixed number of k-space projections, data distributions along radial and angular directions will influence the level of aliasing and streaking artifacts. Conventional radial k-space sampling trajectory introduces an aliasing artifact at the first principal ring of point spread function (PSF). In this paper, a shaking projection (SP) k-space sampling trajectory was proposed to reduce aliasing artifacts in MR images. SP sampling trajectory shifts the projection alternately along the k-space center, which separates k-space data in the azimuthal direction. Simulations based on conventional and SP sampling trajectories were compared with the same number projections. A significant reduction of aliasing artifacts was observed using the SP sampling trajectory. These two trajectories were also compared with different sampling frequencies. A SP trajectory has the same aliasing character when using half sampling frequency (or half data) for reconstruction. SNR comparisons with different white noise levels show that these two trajectories have the same SNR character. In conclusion, the SP trajectory can reduce the aliasing artifact without decreasing SNR and also provide a way for undersampling reconstruction. Furthermore, this method can be applied to three-dimensional (3D) hybrid or spherical radial k-space sampling for a more efficient reduction of aliasing artifacts

Dustfall design of open coal yard in the power plant-a case study on the closed reconstruction project of coal storage yard in shengli power plant

Science.gov (United States)

Wang, Kunpeng; Ji, Weidong; Zhang, Feifei; Yu, Wei; Zheng, Runqing

2018-02-01

This thesis, based on the closed reconstruction project of the coal storage yard of Shengli Power Plant which is affiliated to Sinopec Shengli Petroleum Administration, first makes an analysis on the significance of current dustfall reconstruction of open coal yard, then summarizes the methods widely adopted in the dustfall of large-scale open coal storage yard of current thermal power plant as well as their advantages and disadvantages, and finally focuses on this project, aiming at providing some reference and assistance to the future closed reconstruction project of open coal storage yard in thermal power plant.

Draft Air Pathway Report: Phase 1 of the Hanford Environmental Dose Reconstruction Project

Energy Technology Data Exchange (ETDEWEB)

1990-07-20

This report summarizes the air pathway portion of the first phase of the Hanford Environmental Dose Reconstruction (HEDR) Project, conducted by Battelle staff at the Pacific Northwest Laboratory under the direction of an independent Technical Steering Panel. The HEDR Project is estimating historical radiation doses that could have been received by populations near the Department of Energy's Hanford Site, in southeastern Washington State. Phase 1 of the air-pathway dose reconstruction sought to determine whether dose estimates could be calculated for populations in the 10 counties nearest the Hanford Site from atmospheric releases of iodine-131 from the site from 1944--1947. Phase 1 demonstrated the following: HEDR-calculated source-term estimates of iodine-131 releases to the atmosphere were within 20% of previously published estimates; calculated vegetation concentrations of iodine-131 agree well with previously published measurements; the highest of the Phase 1 preliminary dose estimates to the thyroid are consistent with independent, previously published estimates of doses to maximally exposed individuals; and relatively crude, previously published measurements of thyroid burdens for Hanford workers are in the range of average burdens that the HEDR model estimated for similar reference individuals'' for the period 1944--1947. 4 refs., 10 figs., 9 tabs.

Real-time volumetric image reconstruction and 3D tumor localization based on a single x-ray projection image for lung cancer radiotherapy.

Science.gov (United States)

Li, Ruijiang; Jia, Xun; Lewis, John H; Gu, Xuejun; Folkerts, Michael; Men, Chunhua; Jiang, Steve B

2010-06-01

To develop an algorithm for real-time volumetric image reconstruction and 3D tumor localization based on a single x-ray projection image for lung cancer radiotherapy. Given a set of volumetric images of a patient at N breathing phases as the training data, deformable image registration was performed between a reference phase and the other N-1 phases, resulting in N-1 deformation vector fields (DVFs). These DVFs can be represented efficiently by a few eigenvectors and coefficients obtained from principal component analysis (PCA). By varying the PCA coefficients, new DVFs can be generated, which, when applied on the reference image, lead to new volumetric images. A volumetric image can then be reconstructed from a single projection image by optimizing the PCA coefficients such that its computed projection matches the measured one. The 3D location of the tumor can be derived by applying the inverted DVF on its position in the reference image. The algorithm was implemented on graphics processing units (GPUs) to achieve real-time efficiency. The training data were generated using a realistic and dynamic mathematical phantom with ten breathing phases. The testing data were 360 cone beam projections corresponding to one gantry rotation, simulated using the same phantom with a 50% increase in breathing amplitude. The average relative image intensity error of the reconstructed volumetric images is 6.9% +/- 2.4%. The average 3D tumor localization error is 0.8 +/- 0.5 mm. On an NVIDIA Tesla C1060 GPU card, the average computation time for reconstructing a volumetric image from each projection is 0.24 s (range: 0.17 and 0.35 s). The authors have shown the feasibility of reconstructing volumetric images and localizing tumor positions in 3D in near real-time from a single x-ray image.

The Avignon Bridge: a 3d Reconstruction Project Integrating Archaeological, Historical and Gemorphological Issues

Science.gov (United States)

Berthelot, M.; Nony, N.; Gugi, L.; Bishop, A.; De Luca, L.

2015-02-01

The history and identity of the Avignon's bridge is inseparable from that of the Rhône river. Therefore, in order to share the history and memory of the Rhône, it is essential to get to know this bridge and especially to identify and make visible the traces of its past, its construction, its interaction with the river dynamics, which greatly influenced his life. These are the objectives of the PAVAGE project that focuses on digitally surveying, modelling and re-visiting a heritage site of primary importance with the aim of virtually restoring the link between the two sides which, after the disappearance of the Roman bridge of Arles, constituted for a long time the only connection between Lyon or Vienna and the sea. Therefore, this project has an important geo-historical dimension for which geo-morphological and paleoenvironmental studies were implemented in connection with the latest digital simulation methods exploiting geographic information systems. By integrating knowledge and reflections of archaeologists, historians, geomorphologists, environmentalists, architects, engineers and computer scientists, the result of this project (which involved 5 laboratories during 4 years) is a 3D digital model covering an extension of 50 km2 achieved by integrating satellite imagery, UAV-based acquisitions, terrestrial laser scanning and photogrammetry, etc. Beyond the actions of scientific valorisation concerning the historical and geomorphological dimensions of the project, the results of this work of this interdisciplinary investigation and interpretation of this site are today integrated within a location-based augmented reality application allowing tourists to exploring the virtual reconstruction of the bridge and its environment through tablets inside the portion of territory covered by this project (between Avignon and Villeneuve-lez-Avignon). This paper presents the main aspects of the 3D virtual reconstruction approach.

Comparison of adaptive statistical iterative and filtered back projection reconstruction techniques in quantifying coronary calcium.

Science.gov (United States)

Takahashi, Masahiro; Kimura, Fumiko; Umezawa, Tatsuya; Watanabe, Yusuke; Ogawa, Harumi

2016-01-01

Adaptive statistical iterative reconstruction (ASIR) has been used to reduce radiation dose in cardiac computed tomography. However, change of image parameters by ASIR as compared to filtered back projection (FBP) may influence quantification of coronary calcium. To investigate the influence of ASIR on calcium quantification in comparison to FBP. In 352 patients, CT images were reconstructed using FBP alone, FBP combined with ASIR 30%, 50%, 70%, and ASIR 100% based on the same raw data. Image noise, plaque density, Agatston scores and calcium volumes were compared among the techniques. Image noise, Agatston score, and calcium volume decreased significantly with ASIR compared to FBP (each P ASIR reduced Agatston score by 10.5% to 31.0%. In calcified plaques both of patients and a phantom, ASIR decreased maximum CT values and calcified plaque size. In comparison to FBP, adaptive statistical iterative reconstruction (ASIR) may significantly decrease Agatston scores and calcium volumes. Copyright © 2016 Society of Cardiovascular Computed Tomography. Published by Elsevier Inc. All rights reserved.

Summary of literature review of risk communication: Hanford Environmental Dose Reconstruction Project

International Nuclear Information System (INIS)

Byram, S.J.

1991-05-01

The Hanford Environmental Dose Reconstruction (HEDR) Project will estimate radiation exposures people may have received from radioactive materials released during past operations at the Department of Energy's Hanford Site near Richland, Washington. The project is being conducted by Pacific Northwest Laboratory (PNL) under the direction of an independent Technical Steering Panel (TSP). The Centers for Disease Control (CDC) will use HEDR dose estimates in studies to investigate a potential link between thyroid disease and historical Hanford emissions. The HEDR Project was initiated to address public concerns about the possible health impacts from past releases of radioactive materials from Hanford. The TSP recognized early in the project that special mechanisms would be required to communicate effectively to the many different concerned audiences. To identify and develop these mechanisms, the TSP issued Directive 89-7 to PNL in May 1989. The TSP directed PNL to examine methods to communicate the causes and effects of uncertainties in the dose estimates. A literature review was conducted as the first activity in response to the TSP's directive. This report presents the results of the literature review. The objective of the literature review was to identify ''key principles'' that could be applied to develop communications strategies for the project. 26 refs., 6 figs

Comparison of the image qualities of filtered back-projection, adaptive statistical iterative reconstruction, and model-based iterative reconstruction for CT venography at 80 kVp

International Nuclear Information System (INIS)

Kim, Jin Hyeok; Choo, Ki Seok; Moon, Tae Yong; Lee, Jun Woo; Jeon, Ung Bae; Kim, Tae Un; Hwang, Jae Yeon; Yun, Myeong-Ja; Jeong, Dong Wook; Lim, Soo Jin

2016-01-01

To evaluate the subjective and objective qualities of computed tomography (CT) venography images at 80 kVp using model-based iterative reconstruction (MBIR) and to compare these with those of filtered back projection (FBP) and adaptive statistical iterative reconstruction (ASIR) using the same CT data sets. Forty-four patients (mean age: 56.1 ± 18.1) who underwent 80 kVp CT venography (CTV) for the evaluation of deep vein thrombosis (DVT) during 4 months were enrolled in this retrospective study. The same raw data were reconstructed using FBP, ASIR, and MBIR. Objective and subjective image analysis were performed at the inferior vena cava (IVC), femoral vein, and popliteal vein. The mean CNR of MBIR was significantly greater than those of FBP and ASIR and images reconstructed using MBIR had significantly lower objective image noise (p <.001). Subjective image quality and confidence of detecting DVT by MBIR group were significantly greater than those of FBP and ASIR (p <.005), and MBIR had the lowest score for subjective image noise (p <.001). CTV at 80 kVp with MBIR was superior to FBP and ASIR regarding subjective and objective image qualities. (orig.)

Sexual Behavior, Risk Compensation, and HIV Prevention Strategies Among Participants in the San Francisco PrEP Demonstration Project: A Qualitative Analysis of Counseling Notes.

Science.gov (United States)

Carlo Hojilla, J; Koester, Kimberly A; Cohen, Stephanie E; Buchbinder, Susan; Ladzekpo, Deawodi; Matheson, Tim; Liu, Albert Y

2016-07-01

Pre-exposure prophylaxis (PrEP) is a viable HIV prevention strategy but risk compensation could undermine potential benefits. There are limited data that examine this phenomenon outside of clinical trials. We conducted a qualitative analysis of counseling notes from the San Francisco site of the US PrEP demonstration project to assess how men who have sex with men used PrEP as a prevention strategy and its impact on their sexual practices. Four major themes emerged from our analysis of 130 distinct notes associated with 26 participants. Prevention strategy decision-making was dynamic, often influenced by the context and perceived risk of a sexual encounter. Counselors noted that participants used PrEP in conjunction with other health promotion strategies like condoms, asking about HIV status of their sex partners, and seroadaptation. With few exceptions, existing risk reduction strategies were not abandoned upon initiation of PrEP. Risk-taking behavior was 'seasonal' and fluctuations were influenced by various personal, psychosocial, and health-related factors. PrEP also helped relieve anxiety regarding sex and HIV, particularly among serodiscordant partners. Understanding sexual decision-making and how PrEP is incorporated into existing prevention strategies can help inform future PrEP implementation efforts.

Radionuclide releases to the atmosphere from Hanford Operations, 1944--1972. Hanford Environmental Dose Reconstruction Project

Energy Technology Data Exchange (ETDEWEB)

Heeb, C.M.

1994-05-01

The purpose of the Hanford Environmental Dose Reconstruction Project is to estimate the radiation dose that individuals could have received as a result of radionuclide emissions since 1944 from the Hanford Site. The first step in determining dose is to estimate the amount and timing of radionuclide releases to air and water. This report provides the air release information.

The Hanford Environmental Dose Reconstruction (HEDR) Project: Technical approach

International Nuclear Information System (INIS)

Napier, B.A.; Freshley, M.D.; Gilbert, R.O.; Haerer, H.A.; Morgan, L.G.; Rhoads, R.E.; Woodruff, R.K.

1990-01-01

Historical measurements and current assessment techniques are being combined to estimate potential radiation doses to people from radioactive releases to the air, the Columbia River, soils, and ground water at the Hanford Site since 1944. Environmental contamination from these releases has been monitored, at varying levels of detail, for 45 yr. Phase I of the Hanford Environmental Reconstruction Project will estimate the magnitude of potential doses, their areal extends, and their associated uncertainties. The Phase I study area comprises 10 counties in eastern Washington and northern Oregon, within a 100-mi radius of the site, including a stretch of the Columbia River that was most significantly affected. These counties contain a range of projected and measured contaminant levels, environmental exposure pathways, and population groups. Phase I dose estimates are being developed for the periods 1944 through 1947 for air pathways and 1964 through 1966 for river pathways. Important radionuclide/pathway combinations include fission products, such as 131 I, in milk for early atmospheric releases and activation products, such as 32 P and 65 Zn, in fish for releases to the river. Potential doses range over several orders of magnitude within the study area. We will expand the time periods and study are in three successive phases, as warranted by results of Phase I

Segmentation-DrivenTomographic Reconstruction

DEFF Research Database (Denmark)

Kongskov, Rasmus Dalgas

such that the segmentation subsequently can be carried out by use of a simple segmentation method, for instance just a thresholding method. We tested the advantages of going from a two-stage reconstruction method to a one stage segmentation-driven reconstruction method for the phase contrast tomography reconstruction......The tomographic reconstruction problem is concerned with creating a model of the interior of an object from some measured data, typically projections of the object. After reconstructing an object it is often desired to segment it, either automatically or manually. For computed tomography (CT...

Accelerated perturbation-resilient block-iterative projection methods with application to image reconstruction.

Science.gov (United States)

Nikazad, T; Davidi, R; Herman, G T

2012-03-01

We study the convergence of a class of accelerated perturbation-resilient block-iterative projection methods for solving systems of linear equations. We prove convergence to a fixed point of an operator even in the presence of summable perturbations of the iterates, irrespective of the consistency of the linear system. For a consistent system, the limit point is a solution of the system. In the inconsistent case, the symmetric version of our method converges to a weighted least squares solution. Perturbation resilience is utilized to approximate the minimum of a convex functional subject to the equations. A main contribution, as compared to previously published approaches to achieving similar aims, is a more than an order of magnitude speed-up, as demonstrated by applying the methods to problems of image reconstruction from projections. In addition, the accelerated algorithms are illustrated to be better, in a strict sense provided by the method of statistical hypothesis testing, than their unaccelerated versions for the task of detecting small tumors in the brain from X-ray CT projection data.

Iterative CT reconstruction via minimizing adaptively reweighted total variation.

Science.gov (United States)

Zhu, Lei; Niu, Tianye; Petrongolo, Michael

2014-01-01

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

Weighted regularized statistical shape space projection for breast 3D model reconstruction.

Science.gov (United States)

Ruiz, Guillermo; Ramon, Eduard; García, Jaime; Sukno, Federico M; Ballester, Miguel A González

2018-05-02

The use of 3D imaging has increased as a practical and useful tool for plastic and aesthetic surgery planning. Specifically, the possibility of representing the patient breast anatomy in a 3D shape and simulate aesthetic or plastic procedures is a great tool for communication between surgeon and patient during surgery planning. For the purpose of obtaining the specific 3D model of the breast of a patient, model-based reconstruction methods can be used. In particular, 3D morphable models (3DMM) are a robust and widely used method to perform 3D reconstruction. However, if additional prior information (i.e., known landmarks) is combined with the 3DMM statistical model, shape constraints can be imposed to improve the 3DMM fitting accuracy. In this paper, we present a framework to fit a 3DMM of the breast to two possible inputs: 2D photos and 3D point clouds (scans). Our method consists in a Weighted Regularized (WR) projection into the shape space. The contribution of each point in the 3DMM shape is weighted allowing to assign more relevance to those points that we want to impose as constraints. Our method is applied at multiple stages of the 3D reconstruction process. Firstly, it can be used to obtain a 3DMM initialization from a sparse set of 3D points. Additionally, we embed our method in the 3DMM fitting process in which more reliable or already known 3D points or regions of points, can be weighted in order to preserve their shape information. The proposed method has been tested in two different input settings: scans and 2D pictures assessing both reconstruction frameworks with very positive results. Copyright © 2018 Elsevier B.V. All rights reserved.

Electro-optical system for the high speed reconstruction of computed tomography images

International Nuclear Information System (INIS)

Tresp, V.

1989-01-01

An electro-optical system for the high-speed reconstruction of computed tomography (CT) images has been built and studied. The system is capable of reconstructing high-contrast and high-resolution images at video rate (30 images per second), which is more than two orders of magnitude faster than the reconstruction rate achieved by special purpose digital computers used in commercial CT systems. The filtered back-projection algorithm which was implemented in the reconstruction system requires the filtering of all projections with a prescribed filter function. A space-integrating acousto-optical convolver, a surface acoustic wave filter and a digital finite-impulse response filter were used for this purpose and their performances were compared. The second part of the reconstruction, the back projection of the filtered projections, is computationally very expensive. An optical back projector has been built which maps the filtered projections onto the two-dimensional image space using an anamorphic lens system and a prism image rotator. The reconstructed image is viewed by a video camera, routed through a real-time image-enhancement system, and displayed on a TV monitor. The system reconstructs parallel-beam projection data, and in a modified version, is also capable of reconstructing fan-beam projection data. This extension is important since the latter are the kind of projection data actually acquired in high-speed X-ray CT scanners. The reconstruction system was tested by reconstructing precomputed projection data of phantom images. These were stored in a special purpose projection memory and transmitted to the reconstruction system as an electronic signal. In this way, a projection measurement system that acquires projections sequentially was simulated

Block matching sparsity regularization-based image reconstruction for incomplete projection data in computed tomography

Science.gov (United States)

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

2018-02-01

In medical imaging many conventional regularization methods, such as total variation or total generalized variation, impose strong prior assumptions which can only account for very limited classes of images. A more reasonable sparse representation frame for images is still badly needed. Visually understandable images contain meaningful patterns, and combinations or collections of these patterns can be utilized to form some sparse and redundant representations which promise to facilitate image reconstructions. In this work, we propose and study block matching sparsity regularization (BMSR) and devise an optimization program using BMSR for computed tomography (CT) image reconstruction for an incomplete projection set. The program is built as a constrained optimization, minimizing the L1-norm of the coefficients of the image in the transformed domain subject to data observation and positivity of the image itself. To solve the program efficiently, a practical method based on the proximal point algorithm is developed and analyzed. In order to accelerate the convergence rate, a practical strategy for tuning the BMSR parameter is proposed and applied. The experimental results for various settings, including real CT scanning, have verified the proposed reconstruction method showing promising capabilities over conventional regularization.

Revisiting a Dramatic Triangle: The State, Villagers, and Social Activists in Chinese Rural Reconstruction Projects

Directory of Open Access Journals (Sweden)

Stig Thøgersen

2009-01-01

Full Text Available As part of the movement to “construct a new socialist countryside”, Chinese officials and social activists are experimenting with transforming rural social and economic relations. They often draw on discourses dating back to the Rural Reconstruction Movement of the 1920s and 1930s, which saw urban intellectuals making similar efforts to modernize the villages and their inhabitants. This paper analyses the different types of relationships between the state, social activists, and villagers in a number of rural reconstruction projects. The state is still the major player in this field, but traditional top-down procedures are often perceived to be unproductive when it comes to micro-level community building, so state actors are forced to find allies among village elites and social activists.

Comparison of adaptive statistical iterative and filtered back projection reconstruction techniques in brain CT

International Nuclear Information System (INIS)

Ren, Qingguo; Dewan, Sheilesh Kumar; Li, Ming; Li, Jianying; Mao, Dingbiao; Wang, Zhenglei; Hua, Yanqing

2012-01-01

Purpose: To compare image quality and visualization of normal structures and lesions in brain computed tomography (CT) with adaptive statistical iterative reconstruction (ASIR) and filtered back projection (FBP) reconstruction techniques in different X-ray tube current–time products. Materials and methods: In this IRB-approved prospective study, forty patients (nineteen men, twenty-one women; mean age 69.5 ± 11.2 years) received brain scan at different tube current–time products (300 and 200 mAs) in 64-section multi-detector CT (GE, Discovery CT750 HD). Images were reconstructed with FBP and four levels of ASIR-FBP blending. Two radiologists (please note that our hospital is renowned for its geriatric medicine department, and these two radiologists are more experienced in chronic cerebral vascular disease than in neoplastic disease, so this research did not contain cerebral tumors but as a discussion) assessed all the reconstructed images for visibility of normal structures, lesion conspicuity, image contrast and diagnostic confidence in a blinded and randomized manner. Volume CT dose index (CTDI vol ) and dose-length product (DLP) were recorded. All the data were analyzed by using SPSS 13.0 statistical analysis software. Results: There was no statistically significant difference between the image qualities at 200 mAs with 50% ASIR blending technique and 300 mAs with FBP technique (p > .05). While between the image qualities at 200 mAs with FBP and 300 mAs with FBP technique a statistically significant difference (p < .05) was found. Conclusion: ASIR provided same image quality and diagnostic ability in brain imaging with greater than 30% dose reduction compared with FBP reconstruction technique

Comparison of adaptive statistical iterative and filtered back projection reconstruction techniques in brain CT

Energy Technology Data Exchange (ETDEWEB)

Ren, Qingguo, E-mail: renqg83@163.com [Department of Radiology, Hua Dong Hospital of Fudan University, Shanghai 200040 (China); Dewan, Sheilesh Kumar, E-mail: sheilesh_d1@hotmail.com [Department of Geriatrics, Hua Dong Hospital of Fudan University, Shanghai 200040 (China); Li, Ming, E-mail: minli77@163.com [Department of Radiology, Hua Dong Hospital of Fudan University, Shanghai 200040 (China); Li, Jianying, E-mail: Jianying.Li@med.ge.com [CT Imaging Research Center, GE Healthcare China, Beijing (China); Mao, Dingbiao, E-mail: maodingbiao74@163.com [Department of Radiology, Hua Dong Hospital of Fudan University, Shanghai 200040 (China); Wang, Zhenglei, E-mail: Williswang_doc@yahoo.com.cn [Department of Radiology, Shanghai Electricity Hospital, Shanghai 200050 (China); Hua, Yanqing, E-mail: cjr.huayanqing@vip.163.com [Department of Radiology, Hua Dong Hospital of Fudan University, Shanghai 200040 (China)

2012-10-15

Purpose: To compare image quality and visualization of normal structures and lesions in brain computed tomography (CT) with adaptive statistical iterative reconstruction (ASIR) and filtered back projection (FBP) reconstruction techniques in different X-ray tube current–time products. Materials and methods: In this IRB-approved prospective study, forty patients (nineteen men, twenty-one women; mean age 69.5 ± 11.2 years) received brain scan at different tube current–time products (300 and 200 mAs) in 64-section multi-detector CT (GE, Discovery CT750 HD). Images were reconstructed with FBP and four levels of ASIR-FBP blending. Two radiologists (please note that our hospital is renowned for its geriatric medicine department, and these two radiologists are more experienced in chronic cerebral vascular disease than in neoplastic disease, so this research did not contain cerebral tumors but as a discussion) assessed all the reconstructed images for visibility of normal structures, lesion conspicuity, image contrast and diagnostic confidence in a blinded and randomized manner. Volume CT dose index (CTDI{sub vol}) and dose-length product (DLP) were recorded. All the data were analyzed by using SPSS 13.0 statistical analysis software. Results: There was no statistically significant difference between the image qualities at 200 mAs with 50% ASIR blending technique and 300 mAs with FBP technique (p > .05). While between the image qualities at 200 mAs with FBP and 300 mAs with FBP technique a statistically significant difference (p < .05) was found. Conclusion: ASIR provided same image quality and diagnostic ability in brain imaging with greater than 30% dose reduction compared with FBP reconstruction technique.

Image reconstruction for digital breast tomosynthesis (DBT) by using projection-angle-dependent filter functions

Energy Technology Data Exchange (ETDEWEB)

Park, Yeonok; Park, Chulkyu; Cho, Hyosung; Je, Uikyu; Hong, Daeki; Lee, Minsik; Cho, Heemoon; Choi, Sungil; Koo, Yangseo [Yonsei University, Wonju (Korea, Republic of)

2014-09-15

Digital breast tomosynthesis (DBT) is considered in clinics as a standard three-dimensional imaging modality, allowing the earlier detection of cancer. It typically acquires only 10-30 projections over a limited angle range of 15 - 60 .deg. with a stationary detector and typically uses a computationally-efficient filtered-backprojection (FBP) algorithm for image reconstruction. However, a common FBP algorithm yields poor image quality resulting from the loss of average image value and the presence of severe image artifacts due to the elimination of the dc component of the image by the ramp filter and to the incomplete data, respectively. As an alternative, iterative reconstruction methods are often used in DBT to overcome these difficulties, even though they are still computationally expensive. In this study, as a compromise, we considered a projection-angle dependent filtering method in which one-dimensional geometry-adapted filter kernels are computed with the aid of a conjugate-gradient method and are incorporated into the standard FBP framework. We implemented the proposed algorithm and performed systematic simulation works to investigate the imaging characteristics. Our results indicate that the proposed method is superior to a conventional FBP method for DBT imaging and has a comparable computational cost, while preserving good image homogeneity and edge sharpening with no serious image artifacts.

Simultaneous static and cine nonenhanced MR angiography using radial sampling and highly constrained back projection reconstruction.

Science.gov (United States)

Koktzoglou, Ioannis; Mistretta, Charles A; Giri, Shivraman; Dunkle, Eugene E; Amin, Parag; Edelman, Robert R

2014-10-01

To describe a pulse sequence for simultaneous static and cine nonenhanced magnetic resonance angiography (NEMRA) of the peripheral arteries. The peripheral arteries of 10 volunteers and 6 patients with peripheral arterial disease (PAD) were imaged with the proposed cine NEMRA sequence on a 1.5 Tesla (T) system. The impact of multi-shot imaging and highly constrained back projection (HYPR) reconstruction was examined. The propagation rate of signal along the length of the arterial tree in the cine nonenhanced MR angiograms was quantified. The cine NEMRA sequence simultaneously provided a static MR angiogram showing vascular anatomy as well as a cine display of arterial pulse wave propagation along the entire length of the peripheral arteries. Multi-shot cine NEMRA improved temporal resolution and reduced image artifacts. HYPR reconstruction improved image quality when temporal reconstruction footprints shorter than 100 ms were used (P cine NEMRA was slower in patients with PAD than in volunteers. Simultaneous static and cine NEMRA of the peripheral arteries is feasible. Multi-shot acquisition and HYPR reconstruction can be used to improve arterial conspicuity and temporal resolution. Copyright © 2013 Wiley Periodicals, Inc.

Biologic collagen cylinder with skate flap technique for nipple reconstruction.

Science.gov (United States)

Tierney, Brian P; Hodde, Jason P; Changkuon, Daniela I

2014-01-01

A surgical technique using local tissue skate flaps combined with cylinders made from a naturally derived biomaterial has been used effectively for nipple reconstruction. A retrospective review of patients who underwent nipple reconstruction using this technique was performed. Comorbidities and type of breast reconstruction were collected. Outcome evaluation included complications, surgical revisions, and nipple projection. There were 115 skate flap reconstructions performed in 83 patients between July 2009 and January 2013. Patients ranged from 32 to 73 years old. Average body mass index was 28.0. The most common comorbidities were hypertension (39.8%) and smoking (16.9%). After breast reconstruction, 68.7% of the patients underwent chemotherapy and 20.5% underwent radiation. Seventy-one patients had immediate breast reconstruction with expanders and 12 had delayed reconstruction. The only reported complications were extrusions (3.5%). Six nipples (5.2%) in 5 patients required surgical revision due to loss of projection; two patients had minor loss of projection but did not require surgical revision. Nipple projection at time of surgery ranged from 6 to 7 mm and average projection at 6 months was 3-5 mm. A surgical technique for nipple reconstruction using a skate flap with a graft material is described. Complications are infrequent and short-term projection measurements are encouraging.

A biomechanical modeling-guided simultaneous motion estimation and image reconstruction technique (SMEIR-Bio) for 4D-CBCT reconstruction

Science.gov (United States)

Huang, Xiaokun; Zhang, You; Wang, Jing

2018-02-01

Reconstructing four-dimensional cone-beam computed tomography (4D-CBCT) images directly from respiratory phase-sorted traditional 3D-CBCT projections can capture target motion trajectory, reduce motion artifacts, and reduce imaging dose and time. However, the limited numbers of projections in each phase after phase-sorting decreases CBCT image quality under traditional reconstruction techniques. To address this problem, we developed a simultaneous motion estimation and image reconstruction (SMEIR) algorithm, an iterative method that can reconstruct higher quality 4D-CBCT images from limited projections using an inter-phase intensity-driven motion model. However, the accuracy of the intensity-driven motion model is limited in regions with fine details whose quality is degraded due to insufficient projection number, which consequently degrades the reconstructed image quality in corresponding regions. In this study, we developed a new 4D-CBCT reconstruction algorithm by introducing biomechanical modeling into SMEIR (SMEIR-Bio) to boost the accuracy of the motion model in regions with small fine structures. The biomechanical modeling uses tetrahedral meshes to model organs of interest and solves internal organ motion using tissue elasticity parameters and mesh boundary conditions. This physics-driven approach enhances the accuracy of solved motion in the organ’s fine structures regions. This study used 11 lung patient cases to evaluate the performance of SMEIR-Bio, making both qualitative and quantitative comparisons between SMEIR-Bio, SMEIR, and the algebraic reconstruction technique with total variation regularization (ART-TV). The reconstruction results suggest that SMEIR-Bio improves the motion model’s accuracy in regions containing small fine details, which consequently enhances the accuracy and quality of the reconstructed 4D-CBCT images.

Effect of number of of projections on inverse radon transform based image reconstruction by using filtered back-projection for parallel beam transmission tomography

International Nuclear Information System (INIS)

Qureshi, S.A.; Mirza, S.M.; Arif, M.

2007-01-01

This paper present the effect of number of projections on inverse Radon transform (IRT) estimation using filtered back-projection (FBP) technique for parallel beam transmission tomography. The head phantom and the lung phantom have been used in this work. Various filters used in this study include Ram-Lak, Shepp-Logan, Cosin, Hamming and Hanning filters. The slices have been reconstructed by increasing the number of projections through parallel beam transmission tomography keeping the projections uniformly distributed. The Euclidean and Mean Squared errors and peak signal-to-noise ratio (PSNR) have been analyzed for their sensitiveness as functions of number of projections. It has found that image quality improves with the number of projections but at the cost of the computer time. The error has been minimized to get the best approximation of inverse Radon transform (IRT) as the number of projections is enhanced. The value of PSNR has been found to increase from 8.20 to 24.53 dB as the number of projections is raised from 5 to 180 for head phantom. (author)

Overview of image reconstruction

International Nuclear Information System (INIS)

Marr, R.B.

1980-04-01

Image reconstruction (or computerized tomography, etc.) is any process whereby a function, f, on R/sup n/ is estimated from empirical data pertaining to its integrals, ∫f(x) dx, for some collection of hyperplanes of dimension k < n. The paper begins with background information on how image reconstruction problems have arisen in practice, and describes some of the application areas of past or current interest; these include radioastronomy, optics, radiology and nuclear medicine, electron microscopy, acoustical imaging, geophysical tomography, nondestructive testing, and NMR zeugmatography. Then the various reconstruction algorithms are discussed in five classes: summation, or simple back-projection; convolution, or filtered back-projection; Fourier and other functional transforms; orthogonal function series expansion; and iterative methods. Certain more technical mathematical aspects of image reconstruction are considered from the standpoint of uniqueness, consistency, and stability of solution. The paper concludes by presenting certain open problems. 73 references

PR-PR: cross-platform laboratory automation system.

Science.gov (United States)

Linshiz, Gregory; Stawski, Nina; Goyal, Garima; Bi, Changhao; Poust, Sean; Sharma, Monica; Mutalik, Vivek; Keasling, Jay D; Hillson, Nathan J

2014-08-15

To enable protocol standardization, sharing, and efficient implementation across laboratory automation platforms, we have further developed the PR-PR open-source high-level biology-friendly robot programming language as a cross-platform laboratory automation system. Beyond liquid-handling robotics, PR-PR now supports microfluidic and microscopy platforms, as well as protocol translation into human languages, such as English. While the same set of basic PR-PR commands and features are available for each supported platform, the underlying optimization and translation modules vary from platform to platform. Here, we describe these further developments to PR-PR, and demonstrate the experimental implementation and validation of PR-PR protocols for combinatorial modified Golden Gate DNA assembly across liquid-handling robotic, microfluidic, and manual platforms. To further test PR-PR cross-platform performance, we then implement and assess PR-PR protocols for Kunkel DNA mutagenesis and hierarchical Gibson DNA assembly for microfluidic and manual platforms.

Conversion and correction factors for historical measurements of iodine-131 in Hanford-area vegetation, 1945--1947. Hanford Environmental Dose Reconstruction Project

Energy Technology Data Exchange (ETDEWEB)

Mart, E.I.; Denham, D.H.; Thiede, M.E.

1993-12-01

This report is a result of the Hanford Environmental Dose Reconstruction (HEDR) Project whose goal is to estimate the radiation dose that individuals could have received from emissions since 1944 at the U.S. Department of Energy`s (DOE) Hanford Site near Richland, Washington. The HEDR Project is conducted by Battelle, Pacific Northwest Laboratories (BNW). One of the radionuclides emitted that would affect the radiation dose was iodine-131. This report describes in detail the reconstructed conversion and correction factors for historical measurements of iodine-131 in Hanford-area vegetation which was collected from the beginning of October 1945 through the end of December 1947.

A simple method for 3D lesion reconstruction from two projected angiographic images: implementation to a stereotactic radiotherapy treatment planning system

International Nuclear Information System (INIS)

Theodorou, K.; Kappas, C.; Gaboriaud, G.; Mazal, A.D.; Petrascu, O.; Rosenwald, J.C.

1997-01-01

Introduction: The most used imaging modality for diagnosis and localisation of arteriovenous malformations (AVMs) treated with stereotactic radiotherapy is angiography. The fact that the angiographic images are projected images imposes the need of the 3D reconstruction of the lesion. This, together with the 3D head anatomy from CT images could provide all the necessary information for stereotactic treatment planning. We have developed a method to combine the complementary information provided by angiography and 2D computerized tomography, matching the reconstructed AVM structure with the reconstructed head of the patient. Materials and methods: The ISIS treatment planning system, developed at Institute Curie, has been used for image acquisition, stereotactic localisation and 3D visualisation. A series of CT slices are introduced in the system as well as two orthogonal angiographic projected images of the lesion. A simple computer program has been developed for the 3D reconstruction of the lesion and for the superposition of the target contour on the CT slices of the head. Results and conclusions: In our approach we consider that the reconstruction can be made if the AVM is approximated with a number of adjacent ellipses. We assessed the method comparing the values of the reconstructed and the actual volumes of the target using linear regression analysis. For treatment planning purposes we overlapped the reconstructed AVM on the CT slices of the head. The above feature is to our knowledge a feature that the majority of the commercial stereotactic radiotherapy treatment planning system could not provide. The implementation of the method into ISIS TPS shows that we can reliably approximate and visualize the target volume

3D virtual character reconstruction from projections: a NURBS-based approach

Science.gov (United States)

Triki, Olfa; Zaharia, Titus B.; Preteux, Francoise J.

2004-05-01

This work has been carried out within the framework of the industrial project, so-called TOON, supported by the French government. TOON aims at developing tools for automating the traditional 2D cartoon content production. This paper presents preliminary results of the TOON platform. The proposed methodology concerns the issues of 2D/3D reconstruction from a limited number of drawn projections, and 2D/3D manipulation/deformation/refinement of virtual characters. Specifically, we show that the NURBS-based modeling approach developed here offers a well-suited framework for generating deformable 3D virtual characters from incomplete 2D information. Furthermore, crucial functionalities such as animation and non-rigid deformation can be also efficiently handled and solved. Note that user interaction is enabled exclusively in 2D by achieving a multiview constraint specification method. This is fully consistent and compliant with the cartoon creator traditional practice and makes it possible to avoid the use of 3D modeling software packages which are generally complex to manipulate.

Iterative concurrent reconstruction algorithms for emission computed tomography

International Nuclear Information System (INIS)

Brown, J.K.; Hasegawa, B.H.; Lang, T.F.

1994-01-01

Direct reconstruction techniques, such as those based on filtered backprojection, are typically used for emission computed tomography (ECT), even though it has been argued that iterative reconstruction methods may produce better clinical images. The major disadvantage of iterative reconstruction algorithms, and a significant reason for their lack of clinical acceptance, is their computational burden. We outline a new class of ''concurrent'' iterative reconstruction techniques for ECT in which the reconstruction process is reorganized such that a significant fraction of the computational processing occurs concurrently with the acquisition of ECT projection data. These new algorithms use the 10-30 min required for acquisition of a typical SPECT scan to iteratively process the available projection data, significantly reducing the requirements for post-acquisition processing. These algorithms are tested on SPECT projection data from a Hoffman brain phantom acquired with a 2 x 10 5 counts in 64 views each having 64 projections. The SPECT images are reconstructed as 64 x 64 tomograms, starting with six angular views. Other angular views are added to the reconstruction process sequentially, in a manner that reflects their availability for a typical acquisition protocol. The results suggest that if T s of concurrent processing are used, the reconstruction processing time required after completion of the data acquisition can be reduced by at least 1/3 T s. (Author)

Laparoscopic reconstructive tubal surgery in a tertiary referral centre ...

African Journals Online (AJOL)

Objectives. To establish the pregnancy rate (PR) following endoscopic reconstructive tubal surgery in patients with tubal disease presenting to the Reproductive Medicine Unit at Groote Schuur Hospital between January 1994 and December 1997. Design. A prospective descriptive study utilising the Hulka classification ...

Biologic Collagen Cylinder with Skate Flap Technique for Nipple Reconstruction

Directory of Open Access Journals (Sweden)

Brian P. Tierney

2014-01-01

Full Text Available A surgical technique using local tissue skate flaps combined with cylinders made from a naturally derived biomaterial has been used effectively for nipple reconstruction. A retrospective review of patients who underwent nipple reconstruction using this technique was performed. Comorbidities and type of breast reconstruction were collected. Outcome evaluation included complications, surgical revisions, and nipple projection. There were 115 skate flap reconstructions performed in 83 patients between July 2009 and January 2013. Patients ranged from 32 to 73 years old. Average body mass index was 28.0. The most common comorbidities were hypertension (39.8% and smoking (16.9%. After breast reconstruction, 68.7% of the patients underwent chemotherapy and 20.5% underwent radiation. Seventy-one patients had immediate breast reconstruction with expanders and 12 had delayed reconstruction. The only reported complications were extrusions (3.5%. Six nipples (5.2% in 5 patients required surgical revision due to loss of projection; two patients had minor loss of projection but did not require surgical revision. Nipple projection at time of surgery ranged from 6 to 7 mm and average projection at 6 months was 3–5 mm. A surgical technique for nipple reconstruction using a skate flap with a graft material is described. Complications are infrequent and short-term projection measurements are encouraging.

Systematic Error in Lung Nodule Volumetry : Effect of Iterative Reconstruction Versus Filtered Back Projection at Different CT Parameters

NARCIS (Netherlands)

Willemink, Martin J.; Leiner, Tim; Budde, Ricardo P. J.; de Kort, Freek P. L.; Vliegenthart, Rozemarijn; van Ooijen, Peter M. A.; Oudkerk, Matthijs; de Jong, Pim A.

2012-01-01

OBJECTIVE. Iterative reconstruction potentially can reduce radiation dose compared with filtered back projection (FBP) for chest CT. This is especially important for repeated CT scanning, as is the case in patients with indeterminate lung nodules. It is currently unknown whether absolute nodule

Parallel CT image reconstruction based on GPUs

International Nuclear Information System (INIS)

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

2014-01-01

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

FY 1993 task plans for the Hanford Environmental Dose Reconstruction Project

International Nuclear Information System (INIS)

Shipler, D.B.

1991-10-01

The purpose of the Hanford Environmental Dose Reconstruction (HEDR) Project is to estimate radiation doses from Hanford Site operations since 1944 to individuals and populations. The primary objective of work to be performed in FY 1993 is to complete the source term estimates and dose estimates for key radionuclides for the air and river pathways. At the end of FY 1993, the capability will be in place to estimate doses for individuals in the extended (32-county) study area, 1944--1991. Native American research will continue to provide input for tribal dose estimates. In FY 1993, the Technical Steering Panel (TSP) will decide whether demographic and river pathways data collection should be extended beyond FY 1993 levels. The FY 1993 work scopes and milestones in this document are based on the work plan discussed at the TSP Budget/Fiscal Subcommittee meeting on August 19--20, 1991. Table 1 shows the FY 1993 milestones; Table 2 shows estimated costs. The subsequent work scope descriptions are based on the milestones. This document and the FY 1992 task plans will form the basis for a contract with Battelle and the Centers for Disease Control (CDC). The 2-year dose reconstruction contract is expected to begin in February 1992. This contract will replace the current arrangement, whereby the US Department of Energy directly funds the Pacific Northwest Laboratory to conduct dose reconstruction work. In late FY 1992, the FY 1993 task plans will be more fully developed with detailed technical approaches, data quality objectives, and budgeted labor hours. The task plans will be updated again in July 1993 to reflect any scope, milestone, or cost changes directed during the year by the TSP. 2 tabs

PROJECT OF THE TRANS-SIBERIAN RAILWAY RECONSTRUCTION AS AN OBJECT OF SOCIAL EFFICIENCY EVALUATION

Directory of Open Access Journals (Sweden)

Kibalov E. B.

2015-06-01

Full Text Available We consider the problem of social efficiency evaluation concerning the project of the Trans-Siberian Railway reconstruction. This project is to be realized in the situation of strategic (fundamental uncertainty. Existing tools are not sufficient for solving this problem (because of qualitatively different nature of the project as compared with those abroad, much higher degree of uncertainty, and the lack of estimates for a number of necessary norms. Our study aims at development of an approach that would be adequate to the problem under consideration. We developed a two-level model for investment decision-making for appraisal and selection of a variant of the large-scale project. The upper level of this model bases on the macroeconomic approach (with the use of a specialized version of the Inter-Sector Inter-Region Optimization Model; the lower level bases on the microeconomic approach. As opposed to the foreign practice, the efficiency evaluation and selection of a variant of the transport project is top-down. End-to-end taking uncertainty into account is implemented. A tool for this is the scenario approach on the upper level, and the fuzzy set theory at the lower one.

Prediction of optimal deployment projection for transcatheter aortic valve replacement: angiographic 3-dimensional reconstruction of the aortic root versus multidetector computed tomography.

Science.gov (United States)

Binder, Ronald K; Leipsic, Jonathon; Wood, David; Moore, Teri; Toggweiler, Stefan; Willson, Alex; Gurvitch, Ronen; Freeman, Melanie; Webb, John G

2012-04-01

Identifying the optimal fluoroscopic projection of the aortic valve is important for successful transcatheter aortic valve replacement (TAVR). Various imaging modalities, including multidetector computed tomography (MDCT), have been proposed for prediction of the optimal deployment projection. We evaluated a method that provides 3-dimensional angiographic reconstructions (3DA) of the aortic root for prediction of the optimal deployment angle and compared it with MDCT. Forty patients undergoing transfemoral TAVR at St Paul's Hospital, Vancouver, Canada, were evaluated. All underwent preimplant 3DA and 68% underwent preimplant MDCT. Three-dimensional angiographic reconstructions were generated from images of a C-arm rotational aortic root angiogram during breath-hold, rapid ventricular pacing, and injection of 32 mL contrast medium at 8 mL/s. Two independent operators prospectively predicted perpendicular valve projections. The implant angle was chosen at the discretion of the physician performing TAVR. The angles from 3DA, from MDCT, the implant angle, and the postdeployment perpendicular prosthesis view were compared. The shortest distance from the postdeployment perpendicular prosthesis projection to the regression line of predicted perpendicular projections was calculated. All but 1 patient had adequate image quality for reproducible angle predictions. There was a significant correlation between 3DA and MDCT for prediction of perpendicular valve projections (r=0.682, Pregression line of predicted angles to the postdeployment prosthesis view was 5.1±4.6° for 3DA and 7.9±4.9° for MDCT (P=0.01). Three-dimensional angiographic reconstructions and MDCT are safe, practical, and accurate imaging modalities for identifying the optimal perpendicular valve deployment projection during TAVR.

ESO PR Highlights in 2000

Science.gov (United States)

2001-01-01

At the beginning of the new millennium, ESO and its staff are facing the future with confidence. The four 8.2-m Unit Telescopes of the Very Large Telescope (VLT) are in great shape and the VLT Interferometer (VLTI) will soon have "first fringes". The intercontinental ALMA project is progressing well and concepts for extremely large optical/infrared telescopes are being studied. They can also look back at a fruitful and rewarding past year. Perhaps the most important, single development has been the rapid transition of the Very Large Telescope (VLT). From being a "high-tech project under construction" it has now become a highly proficient, world-class astronomical observatory. This trend is clearly reflected in ESO's Press Releases , as more and more front-line scientific results emerge from rich data obtained at this very efficient facility. There were also exciting news from several of the instruments at La Silla. At the same time, the ESO community may soon grow, as steps towards membership are being taken by various European countries. Throughout 2000, a total of 54 PR communications were made, with a large number of Press Photos and Video Clips, cf. the 2000 PR Index. Some of the ESO PR highlights may be accessed directly via the clickable image on the present page. ESO PR Photo 01/01 is also available in a larger (non-clickable) version [ JPEG: 566 x 566 pix - 112k]. It may be reproduced, if credit is given to the European Southern Observatory.

Polynomial reconstruction of radial catalyst concentration distribution in an experimental type FCC riser for a low number of transversal projections in gamma ray tomography

International Nuclear Information System (INIS)

Melo, Silvio B.; Simoes, Francisco P.M.; Oliveira, Eric F. de; Santos, Maria das Gracas dos; Dantas, Carlos C.

2007-01-01

In the FCC - Fluid Catalytic Cracking process the Riser is an opaque cylinder, so that, in order to investigate the catalyst concentration inside, a gamma- ray based tomography is employed. Each section is submitted to a parallel beam and by means of the Beer-Lambert transmission is calculated. This tomography session is repeated from different angles, in manual tomographic experiments where the source/detector pair is rotated, producing in each direction what we called a transversal projection. In order to reconstruct the concentration of the present catalyst in a given moment some methods use successfully the inverse Radon transform through the filtered back-projection algorithm. The results are fully satisfactory for a large number of projections, widely seen as better than those produced by the algebraic methods. For a low number of projections, however, the algebraic methods become more competitive. In practice, simple experimental set-ups work with less than 10 projections, due to the time taken by the whole process. In this work, we present an investigation of polynomial reconstructions by using Bezier surfaces of arbitrary degree, adjusted to the experimental data through a least squares method. A computational algorithm was developed to implement the mathematical reconstruction for the 3D graphics presentation. (author)

Integrated Task Plans for the Hanford Environmental Dose Reconstruction Project, FY 1992 through May 1994

International Nuclear Information System (INIS)

Shipler, D.B.

1992-09-01

The purpose of the Hanford Environmental Dose Reconstruction (HEDR) Project is to estimate radiation doses from Hanford Site operations since 1944 to populations and individuals. The primary objective of work to be performed through May 1994 is to (1) determine the project's appropriate scope (space, time, radionuclides, pathways and individuals/population groups), (2) determine the project's appropriate level of accuracy (level of uncertainty in dose estimates) for the project, (3) complete model and data development, and (4) estimate doses for the Hanford Thyroid Disease Study (HTDS), representative individuals, and special populations as described herein. The plan for FY 1992 through May 1994 has been prepared based on activities and budgets approved by the Technical Steering Panel (TSP) at its meetings on August 19--20, 1991, and April 23--25, 1992. The activities can be divided into four broad categories: (1) model and data evaluation activities, (2)additional dose estimates, (3) model and data development activities, and (4)technical and communication support

Improving Filtered Backprojection Reconstruction by Data-Dependent Filtering

NARCIS (Netherlands)

D.M. Pelt (Daniël); K.J. Batenburg (Joost)

2014-01-01

htmlabstractFiltered backprojection, one of the most widely used reconstruction methods in tomography, requires a large number of low-noise projections to yield accurate reconstructions. In many applications of tomography, complete projection data of high quality cannot be obtained, because of

The Algebraic Reconstruction Technique (ART)

International Nuclear Information System (INIS)

Raparia, D.; Alessi, J.; Kponou, A.

1997-01-01

Projections of charged particle beam current density (profiles) are frequently used as a measure of beam position and size. In conventional practice only two projections, usually horizontal and vertical, are measured. This puts a severe limit on the detail of information that can be achieved. A third projection provides a significant improvement. The Algebraic Reconstruction Technique (ART) uses three or more projections to reconstruct 3-dimensional density profiles. At the 200 MeV H-linac, we have used this technique to measure beam density, and it has proved very helpful, especially in helping determine if there is any coupling present in x-y phase space. We will present examples of measurements of current densities using this technique

Distance weighting for improved tomographic reconstructions

International Nuclear Information System (INIS)

Koeppe, R.A.; Holden, J.E.

1984-01-01

An improved method for the reconstruction of emission computed axial tomography images has been developed. The method is a modification of filtered back-projection, where the back projected values are weighted to reflect the loss of formation, with distance from the camera, which is inherent in gamma camera imaging. This information loss is a result of: loss of spatial resolution with distance, attenuation, and scatter. The weighting scheme can best be described by considering the contributions of any two opposing views to the reconstruction image pixels. The weight applied to the projections of one view is set to equal the relative amount of the original activity that was initially received in that projection, assuming a uniform attenuating medium. This yields a weighting value which is a function of distance into the image with a value of one for pixels ''near the camera'', a value of .5 at the image center, and a value of zero on the opposite side. Tomographic reconstructions produced with this method show improved spatial resolution when compared to conventional 360 0 reconstructions. The improvement is in the tangential direction, where simulations have indicated a FWHM improvement of 1 to 1.5 millimeters. The resolution in the radial direction is essentially the same for both methods. Visual inspection of the reconstructed images show improved resolution and contrast

How Much Do We Know about Drug Resistance Due to PrEP Use? Analysis of Experts' Opinion and Its Influence on the Projected Public Health Impact.

Directory of Open Access Journals (Sweden)

Dobromir T Dimitrov

Full Text Available Randomized controlled trials reported that pre-exposure prophylaxis (PrEP with tenofovir and emtricitabine rarely selects for drug resistance. However, drug resistance due to PrEP is not completely understood. In daily practice, PrEP will not be used under the well-controlled conditions available in the trials, suggesting that widespread use of PrEP can result in increased drug resistance.We surveyed expert virologists with questions about biological assumptions regarding drug resistance due to PrEP use. The influence of these assumptions on the prevalence of drug resistance and the fraction of HIV transmitted resistance was studied with a mathematical model. For comparability, 50% PrEP-coverage of and 90% per-act efficacy of PrEP in preventing HIV acquisition are assumed in all simulations.Virologists disagreed on the following: the time until resistance emergence (range: 20-180 days in infected PrEP users with breakthrough HIV infections; the efficacy of PrEP against drug-resistant HIV (25%-90%; and the likelihood of resistance acquisition upon transmission (10%-75%. These differences translate into projections of 0.6%- 1% and 3.5%-6% infected individuals with detectable resistance 10 years after introducing PrEP, assuming 100% and 50% adherence, respectively. The rate of resistance emergence following breakthrough HIV infection and the rate of resistance reversion after PrEP use is discontinued, were the factors identified as most influential on the expected resistance associated with PrEP. Importantly, 17-23% infected individuals could virologically fail treatment as a result of past PrEP use or transmitted resistance to PrEP with moderate adherence.There is no broad consensus on quantification of key biological processes that underpin the emergence of PrEP-associated drug resistance. Despite this, the contribution of PrEP use to the prevalence of the detectable drug resistance is expected to be small. However, individuals who become

Direct iterative reconstruction of computed tomography trajectories (DIRECTT)

International Nuclear Information System (INIS)

Lange, A.; Hentschel, M.P.; Schors, J.

2004-01-01

The direct reconstruction approach employs an iterative procedure by selection of and angular averaging over projected trajectory data of volume elements. This avoids the blur effects of the classical Fourier method due to the sampling theorem. But longer computing time is required. The reconstructed tomographic images reveal at least the spatial resolution of the radiation detector. Any set of projection angles may be selected for the measurements. Limited rotation of the object yields still good reconstruction of details. Projections of a partial region of the object can be reconstructed without additional artifacts thus reducing the overall radiation dose. Noisy signal data from low dose irradiation have low impact on spatial resolution. The image quality is monitored during all iteration steps and is pre-selected according to the specific requirements. DIRECTT can be applied independently from the measurement equipment in addition to conventional reconstruction or as a refinement filter. (author)

A modified discrete algebraic reconstruction technique for multiple grey image reconstruction for limited angle range tomography.

Science.gov (United States)

Liang, Zhiting; Guan, Yong; Liu, Gang; Chen, Xiangyu; Li, Fahu; Guo, Pengfei; Tian, Yangchao

2016-03-01

The `missing wedge', which is due to a restricted rotation range, is a major challenge for quantitative analysis of an object using tomography. With prior knowledge of the grey levels, the discrete algebraic reconstruction technique (DART) is able to reconstruct objects accurately with projections in a limited angle range. However, the quality of the reconstructions declines as the number of grey levels increases. In this paper, a modified DART (MDART) was proposed, in which each independent region of homogeneous material was chosen as a research object, instead of the grey values. The grey values of each discrete region were estimated according to the solution of the linear projection equations. The iterative process of boundary pixels updating and correcting the grey values of each region was executed alternately. Simulation experiments of binary phantoms as well as multiple grey phantoms show that MDART is capable of achieving high-quality reconstructions with projections in a limited angle range. The interesting advancement of MDART is that neither prior knowledge of the grey values nor the number of grey levels is necessary.

23 CFR 140.606 - Project agreements.

Science.gov (United States)

2010-04-01

... Reimbursement for Bond Issue Projects § 140.606 Project agreements. Project Agreements, Form PR-2, shall be... 23 Highways 1 2010-04-01 2010-04-01 false Project agreements. 140.606 Section 140.606 Highways... projects. 1 The text of FHWA Form PR-2 is found in 23 CFR part 630, subpart C, appendix A. ...

Quantitative analysis of emphysema and airway measurements according to iterative reconstruction algorithms: comparison of filtered back projection, adaptive statistical iterative reconstruction and model-based iterative reconstruction

International Nuclear Information System (INIS)

Choo, Ji Yung; Goo, Jin Mo; Park, Chang Min; Park, Sang Joon; Lee, Chang Hyun; Shim, Mi-Suk

2014-01-01

To evaluate filtered back projection (FBP) and two iterative reconstruction (IR) algorithms and their effects on the quantitative analysis of lung parenchyma and airway measurements on computed tomography (CT) images. Low-dose chest CT obtained in 281 adult patients were reconstructed using three algorithms: FBP, adaptive statistical IR (ASIR) and model-based IR (MBIR). Measurements of each dataset were compared: total lung volume, emphysema index (EI), airway measurements of the lumen and wall area as well as average wall thickness. Accuracy of airway measurements of each algorithm was also evaluated using an airway phantom. EI using a threshold of -950 HU was significantly different among the three algorithms in decreasing order of FBP (2.30 %), ASIR (1.49 %) and MBIR (1.20 %) (P < 0.01). Wall thickness was also significantly different among the three algorithms with FBP (2.09 mm) demonstrating thicker walls than ASIR (2.00 mm) and MBIR (1.88 mm) (P < 0.01). Airway phantom analysis revealed that MBIR showed the most accurate value for airway measurements. The three algorithms presented different EIs and wall thicknesses, decreasing in the order of FBP, ASIR and MBIR. Thus, care should be taken in selecting the appropriate IR algorithm on quantitative analysis of the lung. (orig.)

Quantitative analysis of emphysema and airway measurements according to iterative reconstruction algorithms: comparison of filtered back projection, adaptive statistical iterative reconstruction and model-based iterative reconstruction

Energy Technology Data Exchange (ETDEWEB)

Choo, Ji Yung [Seoul National University Medical Research Center, Department of Radiology, Seoul National University College of Medicine, and Institute of Radiation Medicine, Seoul (Korea, Republic of); Korea University Ansan Hospital, Ansan-si, Department of Radiology, Gyeonggi-do (Korea, Republic of); Goo, Jin Mo; Park, Chang Min; Park, Sang Joon [Seoul National University Medical Research Center, Department of Radiology, Seoul National University College of Medicine, and Institute of Radiation Medicine, Seoul (Korea, Republic of); Seoul National University, Cancer Research Institute, Seoul (Korea, Republic of); Lee, Chang Hyun; Shim, Mi-Suk [Seoul National University Medical Research Center, Department of Radiology, Seoul National University College of Medicine, and Institute of Radiation Medicine, Seoul (Korea, Republic of)

2014-04-15

To evaluate filtered back projection (FBP) and two iterative reconstruction (IR) algorithms and their effects on the quantitative analysis of lung parenchyma and airway measurements on computed tomography (CT) images. Low-dose chest CT obtained in 281 adult patients were reconstructed using three algorithms: FBP, adaptive statistical IR (ASIR) and model-based IR (MBIR). Measurements of each dataset were compared: total lung volume, emphysema index (EI), airway measurements of the lumen and wall area as well as average wall thickness. Accuracy of airway measurements of each algorithm was also evaluated using an airway phantom. EI using a threshold of -950 HU was significantly different among the three algorithms in decreasing order of FBP (2.30 %), ASIR (1.49 %) and MBIR (1.20 %) (P < 0.01). Wall thickness was also significantly different among the three algorithms with FBP (2.09 mm) demonstrating thicker walls than ASIR (2.00 mm) and MBIR (1.88 mm) (P < 0.01). Airway phantom analysis revealed that MBIR showed the most accurate value for airway measurements. The three algorithms presented different EIs and wall thicknesses, decreasing in the order of FBP, ASIR and MBIR. Thus, care should be taken in selecting the appropriate IR algorithm on quantitative analysis of the lung. (orig.)

EFFECT OF DIGITAL FRINGE PROJECTION PARAMETERS ON 3D RECONSTRUCTION ACCURACY

Directory of Open Access Journals (Sweden)

A. Babaei

2013-09-01

This paper aims to evaluate different parameters which affect the accuracy of the final results. For this purpose, some test were designed and implemented. These tests assess the number of phase shifts, spatial frequency of the fringe pattern, light condition, noise level of images, and the color and material of target objects on the quality of resulted phase map. The evaluation results demonstrate that digital fringe projection method is capable of obtaining depth map of complicated object with high accuracy. The contrast test results showed that this method is able to work under different ambient light condition; although at places with high light condition will not work properly. The results of implementation on different objects with various materials, color and shapes demonstrate the high capability of this method of 3D reconstruction.

[Reconstruction and measurement of a digital dental model using grating projection and reverse engineering].

Science.gov (United States)

Zhenzhen, Wang; Yi, Lu; Jun, Song; Jun, Chen; Qin, Zhou

2015-02-01

This work lays the foundation for establishing a digital model database with normal occlusion. A digital dental cast is acquired through grating projection, and model features are measured through reverse engineering. The grating projection system controlled by a computer was projected onto the surface of a normal dental model. Three-dimensional contour data were obtained through multi-angle shooting. A three-dimensional model was constructed, and the model features were analyzed by using reverse engineering. The digital model was compared with the plaster model to determine the accuracy of the measurement system. The structure of three-dimensional reconstruction model was clear. The digital models of two measurements exhibited no significant difference (P > 0.05). When digital and plaster models were measured, we found that the crown length and arch width were not statistically different (P > 0.05), whereas the difference between the crown width and arch length was statistically significant (P model by using the grating projection technique and reverse engineering can be used for dental model measurement in clinic al and scientific research and can provide a scientific method for establishing a digital model database with normal occlusion.

Superiority of CT imaging reconstruction on Linux OS

International Nuclear Information System (INIS)

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

2010-01-01

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

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

International Nuclear Information System (INIS)

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

2002-01-01

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

Virtual patient 3D dose reconstruction using in air EPID measurements and a back-projection algorithm for IMRT and VMAT treatments.

Science.gov (United States)

Olaciregui-Ruiz, Igor; Rozendaal, Roel; van Oers, René F M; Mijnheer, Ben; Mans, Anton

2017-05-01

At our institute, a transit back-projection algorithm is used clinically to reconstruct in vivo patient and in phantom 3D dose distributions using EPID measurements behind a patient or a polystyrene slab phantom, respectively. In this study, an extension to this algorithm is presented whereby in air EPID measurements are used in combination with CT data to reconstruct 'virtual' 3D dose distributions. By combining virtual and in vivo patient verification data for the same treatment, patient-related errors can be separated from machine, planning and model errors. The virtual back-projection algorithm is described and verified against the transit algorithm with measurements made behind a slab phantom, against dose measurements made with an ionization chamber and with the OCTAVIUS 4D system, as well as against TPS patient data. Virtual and in vivo patient dose verification results are also compared. Virtual dose reconstructions agree within 1% with ionization chamber measurements. The average γ-pass rate values (3% global dose/3mm) in the 3D dose comparison with the OCTAVIUS 4D system and the TPS patient data are 98.5±1.9%(1SD) and 97.1±2.9%(1SD), respectively. For virtual patient dose reconstructions, the differences with the TPS in median dose to the PTV remain within 4%. Virtual patient dose reconstruction makes pre-treatment verification based on deviations of DVH parameters feasible and eliminates the need for phantom positioning and re-planning. Virtual patient dose reconstructions have additional value in the inspection of in vivo deviations, particularly in situations where CBCT data is not available (or not conclusive). Copyright © 2017 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Adaptive statistical iterative reconstruction versus filtered back projection in the same patient: 64 channel liver CT image quality and patient radiation dose

International Nuclear Information System (INIS)

Mitsumori, Lee M.; Shuman, William P.; Busey, Janet M.; Kolokythas, Orpheus; Koprowicz, Kent M.

2012-01-01

To compare routine dose liver CT reconstructed with filtered back projection (FBP) versus low dose images reconstructed with FBP and adaptive statistical iterative reconstruction (ASIR). In this retrospective study, patients had a routine dose protocol reconstructed with FBP, and again within 17 months (median 6.1 months), had a low dose protocol reconstructed twice, with FBP and ASIR. These reconstructions were compared for noise, image quality, and radiation dose. Nineteen patients were included. (12 male, mean age 58). Noise was significantly lower in low dose images reconstructed with ASIR compared to routine dose images reconstructed with FBP (liver: p <.05, aorta: p < 0.001). Low dose FBP images were scored significantly lower for subjective image quality than low dose ASIR (2.1 ± 0.5, 3.2 ± 0.8, p < 0.001). There was no difference in subjective image quality scores between routine dose FBP images and low dose ASIR images (3.6 ± 0.5, 3.2 ± 0.8, NS).Radiation dose was 41% less for the low dose protocol (4.4 ± 2.4 mSv versus 7.5 ± 5.5 mSv, p < 0.05). Our initial results suggest low dose CT images reconstructed with ASIR may have lower measured noise, similar image quality, yet significantly less radiation dose compared with higher dose images reconstructed with FBP. (orig.)

Adaptive statistical iterative reconstruction versus filtered back projection in the same patient: 64 channel liver CT image quality and patient radiation dose

Energy Technology Data Exchange (ETDEWEB)

Mitsumori, Lee M.; Shuman, William P.; Busey, Janet M.; Kolokythas, Orpheus; Koprowicz, Kent M. [University of Washington School of Medicine, Department of Radiology, Seattle, WA (United States)

2012-01-15

To compare routine dose liver CT reconstructed with filtered back projection (FBP) versus low dose images reconstructed with FBP and adaptive statistical iterative reconstruction (ASIR). In this retrospective study, patients had a routine dose protocol reconstructed with FBP, and again within 17 months (median 6.1 months), had a low dose protocol reconstructed twice, with FBP and ASIR. These reconstructions were compared for noise, image quality, and radiation dose. Nineteen patients were included. (12 male, mean age 58). Noise was significantly lower in low dose images reconstructed with ASIR compared to routine dose images reconstructed with FBP (liver: p <.05, aorta: p < 0.001). Low dose FBP images were scored significantly lower for subjective image quality than low dose ASIR (2.1 {+-} 0.5, 3.2 {+-} 0.8, p < 0.001). There was no difference in subjective image quality scores between routine dose FBP images and low dose ASIR images (3.6 {+-} 0.5, 3.2 {+-} 0.8, NS).Radiation dose was 41% less for the low dose protocol (4.4 {+-} 2.4 mSv versus 7.5 {+-} 5.5 mSv, p < 0.05). Our initial results suggest low dose CT images reconstructed with ASIR may have lower measured noise, similar image quality, yet significantly less radiation dose compared with higher dose images reconstructed with FBP. (orig.)

Distributed 3-D iterative reconstruction for quantitative SPECT

International Nuclear Information System (INIS)

Ju, Z.W.; Frey, E.C.; Tsui, B.M.W.

1995-01-01

The authors describe a distributed three dimensional (3-D) iterative reconstruction library for quantitative single-photon emission computed tomography (SPECT). This library includes 3-D projector-backprojector pairs (PBPs) and distributed 3-D iterative reconstruction algorithms. The 3-D PBPs accurately and efficiently model various combinations of the image degrading factors including attenuation, detector response and scatter response. These PBPs were validated by comparing projection data computed using the projectors with that from direct Monte Carlo (MC) simulations. The distributed 3-D iterative algorithms spread the projection-backprojection operations for all the projection angles over a heterogeneous network of single or multi-processor computers to reduce the reconstruction time. Based on a master/slave paradigm, these distributed algorithms provide dynamic load balancing and fault tolerance. The distributed algorithms were verified by comparing images reconstructed using both the distributed and non-distributed algorithms. Computation times for distributed 3-D reconstructions running on up to 4 identical processors were reduced by a factor approximately 80--90% times the number of the processors participating, compared to those for non-distributed 3-D reconstructions running on a single processor. When combined with faster affordable computers, this library provides an efficient means for implementing accurate reconstruction and compensation methods to improve quality and quantitative accuracy in SPECT images

Comparison of maximum intensity projection and digitally reconstructed radiographic projection for carotid artery stenosis measurement

International Nuclear Information System (INIS)

Hyde, Derek E.; Habets, Damiaan F.; Fox, Allan J.; Gulka, Irene; Kalapos, Paul; Lee, Don H.; Pelz, David M.; Holdsworth, David W.

2007-01-01

Digital subtraction angiography is being supplanted by three-dimensional imaging techniques in many clinical applications, leading to extensive use of maximum intensity projection (MIP) images to depict volumetric vascular data. The MIP algorithm produces intensity profiles that are different than conventional angiograms, and can also increase the vessel-to-tissue contrast-to-noise ratio. We evaluated the effect of the MIP algorithm in a clinical application where quantitative vessel measurement is important: internal carotid artery stenosis grading. Three-dimensional computed rotational angiography (CRA) was performed on 26 consecutive symptomatic patients to verify an internal carotid artery stenosis originally found using duplex ultrasound. These volumes of data were visualized using two different postprocessing projection techniques: MIP and digitally reconstructed radiographic (DRR) projection. A DRR is a radiographic image simulating a conventional digitally subtracted angiogram, but it is derived computationally from the same CRA dataset as the MIP. By visualizing a single volume with two different projection techniques, the postprocessing effect of the MIP algorithm is isolated. Vessel measurements were made, according to the NASCET guidelines, and percentage stenosis grades were calculated. The paired t-test was used to determine if the measurement difference between the two techniques was statistically significant. The CRA technique provided an isotropic voxel spacing of 0.38 mm. The MIPs and DRRs had a mean signal-difference-to-noise-ratio of 30:1 and 26:1, respectively. Vessel measurements from MIPs were, on average, 0.17 mm larger than those from DRRs (P<0.0001). The NASCET-type stenosis grades tended to be underestimated on average by 2.4% with the MIP algorithm, although this was not statistically significant (P=0.09). The mean interobserver variability (standard deviation) of both the MIP and DRR images was 0.35 mm. It was concluded that the MIP

Projected potential profiles across interfaces obtained by reconstructing the exit face wave function from through focal series

International Nuclear Information System (INIS)

Bhattacharyya, Somnath; Koch, Christoph T.; Ruehle, Manfred

2006-01-01

An iterative method for reconstructing the exit face wave function from a through focal series of transmission electron microscopy image line profiles across an interface is presented. Apart from high-resolution images recorded with small changes in defocus, this method works also well for a large defocus range as used for Fresnel imaging. Using the phase-object approximation the projected electrostatic as well as the absorptive potential profiles across an interface are determined from this exit face wave function. A new experimental image alignment procedure was developed in order to align images with large relative defocus shift. The performance of this procedure is shown to be superior to other image alignment procedures existing in the literature. The reconstruction method is applied to both simulated and experimental images

MR-guided PET motion correction in LOR space using generic projection data for image reconstruction with PRESTO

International Nuclear Information System (INIS)

Scheins, J.; Ullisch, M.; Tellmann, L.; Weirich, C.; Rota Kops, E.; Herzog, H.; Shah, N.J.

2013-01-01

The BrainPET scanner from Siemens, designed as hybrid MR/PET system for simultaneous acquisition of both modalities, provides high-resolution PET images with an optimum resolution of 3 mm. However, significant head motion often compromises the achievable image quality, e.g. in neuroreceptor studies of human brain. This limitation can be omitted when tracking the head motion and accurately correcting measured Lines-of-Response (LORs). For this purpose, we present a novel method, which advantageously combines MR-guided motion tracking with the capabilities of the reconstruction software PRESTO (PET Reconstruction Software Toolkit) to convert motion-corrected LORs into highly accurate generic projection data. In this way, the high-resolution PET images achievable with PRESTO can also be obtained in presence of severe head motion

Image Reconstruction. Chapter 13

Energy Technology Data Exchange (ETDEWEB)

Nuyts, J. [Department of Nuclear Medicine and Medical Imaging Research Center, Katholieke Universiteit Leuven, Leuven (Belgium); Matej, S. [Medical Image Processing Group, Department of Radiology, University of Pennsylvania, Philadelphia, PA (United States)

2014-12-15

This chapter discusses how 2‑D or 3‑D images of tracer distribution can be reconstructed from a series of so-called projection images acquired with a gamma camera or a positron emission tomography (PET) system [13.1]. This is often called an ‘inverse problem’. The reconstruction is the inverse of the acquisition. The reconstruction is called an inverse problem because making software to compute the true tracer distribution from the acquired data turns out to be more difficult than the ‘forward’ direction, i.e. making software to simulate the acquisition. There are basically two approaches to image reconstruction: analytical reconstruction and iterative reconstruction. The analytical approach is based on mathematical inversion, yielding efficient, non-iterative reconstruction algorithms. In the iterative approach, the reconstruction problem is reduced to computing a finite number of image values from a finite number of measurements. That simplification enables the use of iterative instead of mathematical inversion. Iterative inversion tends to require more computer power, but it can cope with more complex (and hopefully more accurate) models of the acquisition process.

A work bibliography on native food consumption, demography and lifestyle. Hanford Environmental Dose Reconstruction Project

Energy Technology Data Exchange (ETDEWEB)

Murray, C.E.; Lee, W.J.

1992-12-01

The purpose of this report is to provide a bibliography for the Native American tribe participants in the Hanford Environmental Dose Reconstruction (HEDR) Project to use. The HEDR Project`s primary objective is to estimate the radiation dose that individuals could have received as a result of emissions since 1944 from the US Department of Energy`s Hanford Site near Richland, Washington. Eight Native American tribes are responsible for estimating daily and seasonal consumption of traditional foods, demography, and other lifestyle factors that could have affected the radiation dose received by tribal members. This report provides a bibliography of recorded accounts that tribal researchers may use to verify their estimates. The bibliographic citations include references to information on the specific tribes, Columbia River plateau ethnobotany, infant feeding practices and milk consumption, nutritional studies and radiation, tribal economic and demographic characteristics (1940--1970), research methods, primary sources from the National Archives, regional archives, libraries, and museums.

PrEP implementation in the Asia-Pacific region: opportunities, implementation and barriers

Science.gov (United States)

Zablotska, Iryna; Grulich, Andrew E; Phanuphak, Nittaya; Anand, Tarandeep; Janyam, Surang; Poonkasetwattana, Midnight; Baggaley, Rachel; van Griensven, Frits; Lo, Ying-Ru

2016-01-01

Introduction HIV epidemics in the Asia-Pacific region are concentrated among men who have sex with men (MSM) and other key populations. Pre-exposure prophylaxis (PrEP) is an effective HIV prevention intervention and could be a potential game changer in the region. We discuss the progress towards PrEP implementation in the Asia-Pacific region, including opportunities and barriers. Discussion Awareness about PrEP in the Asia-Pacific is still low and so are its levels of use. A high proportion of MSM who are aware of PrEP are willing to use it. Key PrEP implementation barriers include poor knowledge about PrEP, limited access to PrEP, weak or non-existent HIV prevention programmes for MSM and other key populations, high cost of PrEP, stigma and discrimination against key populations and restrictive laws in some countries. Only several clinical trials, demonstration projects and a few larger-scale implementation studies have been implemented so far in Thailand and Australia. However, novel approaches to PrEP implementation have emerged: researcher-, facility- and community-led models of care, with PrEP services for fee and for free. The WHO consolidated guidelines on HIV testing, treatment and prevention call for an expanded access to PrEP worldwide and have provided guidance on PrEP implementation in the region. Some countries like Australia have released national PrEP guidelines. There are growing community leadership and consultation processes to initiate PrEP implementation in Asia and the Pacific. Conclusions Countries of the Asia-Pacific region will benefit from adding PrEP to their HIV prevention packages, but for many this is a critical step that requires resourcing. Having an impact on the HIV epidemic requires investment. The next years should see the region transitioning from limited PrEP implementation projects to growing access to PrEP and expansion of HIV prevention programmes. PMID:27760688

Quantitative tomography simulations and reconstruction algorithms

International Nuclear Information System (INIS)

Martz, H.E.; Aufderheide, M.B.; Goodman, D.; Schach von Wittenau, A.; Logan, C.; Hall, J.; Jackson, J.; Slone, D.

2000-01-01

X-ray, neutron and proton transmission radiography and computed tomography (CT) are important diagnostic tools that are at the heart of LLNL's effort to meet the goals of the DOE's Advanced Radiography Campaign. This campaign seeks to improve radiographic simulation and analysis so that radiography can be a useful quantitative diagnostic tool for stockpile stewardship. Current radiographic accuracy does not allow satisfactory separation of experimental effects from the true features of an object's tomographically reconstructed image. This can lead to difficult and sometimes incorrect interpretation of the results. By improving our ability to simulate the whole radiographic and CT system, it will be possible to examine the contribution of system components to various experimental effects, with the goal of removing or reducing them. In this project, we are merging this simulation capability with a maximum-likelihood (constrained-conjugate-gradient-CCG) reconstruction technique yielding a physics-based, forward-model image-reconstruction code. In addition, we seek to improve the accuracy of computed tomography from transmission radiographs by studying what physics is needed in the forward model. During FY 2000, an improved version of the LLNL ray-tracing code called HADES has been coupled with a recently developed LLNL CT algorithm known as CCG. The problem of image reconstruction is expressed as a large matrix equation relating a model for the object being reconstructed to its projections (radiographs). Using a constrained-conjugate-gradient search algorithm, a maximum likelihood solution is sought. This search continues until the difference between the input measured radiographs or projections and the simulated or calculated projections is satisfactorily small

Atmospheric transport and dispersion modeling for the Hanford Environmental Dose Reconstruction Project

International Nuclear Information System (INIS)

Ramsdell, J.V.

1991-07-01

Radiation doses that may have resulted from operations at the Hanford Site are being estimated in the Hanford Environmental Dose Reconstruction (HEDR) Project. One of the project subtasks, atmospheric transport, is responsible for estimating the transport, diffusion and deposition of radionuclides released to the atmosphere. This report discusses modeling transport and diffusion in the atmospheric pathway. It is divided into three major sections. The first section of the report presents the atmospheric modeling approach selected following discussion with the Technical Steering Panel that directs the HEDR Project. In addition, the section discusses the selection of the MESOI/MESORAD suite of atmospheric dispersion models that form the basis for initial calculations and future model development. The second section of the report describes alternative modeling approaches that were considered. Emphasis is placed on the family of plume and puff models that are based on Gaussian solution to the diffusion equations. The final portion of the section describes the performance of various models. The third section of the report discusses factors that bear on the selection of an atmospheric transport modeling approach for HEDR. These factors, which include the physical setting of the Hanford Site and the available meteorological data, serve as constraints on model selection. Five appendices are included in the report. 39 refs., 4 figs., 2 tabs

DART: a practical reconstruction algorithm for discrete tomography.

Science.gov (United States)

Batenburg, Kees Joost; Sijbers, Jan

2011-09-01

In this paper, we present an iterative reconstruction algorithm for discrete tomography, called discrete algebraic reconstruction technique (DART). DART can be applied if the scanned object is known to consist of only a few different compositions, each corresponding to a constant gray value in the reconstruction. Prior knowledge of the gray values for each of the compositions is exploited to steer the current reconstruction towards a reconstruction that contains only these gray values. Based on experiments with both simulated CT data and experimental μCT data, it is shown that DART is capable of computing more accurate reconstructions from a small number of projection images, or from a small angular range, than alternative methods. It is also shown that DART can deal effectively with noisy projection data and that the algorithm is robust with respect to errors in the estimation of the gray values.

Cone-beam local reconstruction based on a Radon inversion transformation

International Nuclear Information System (INIS)

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

2012-01-01

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

Regional sea level projections with observed gauge, altimeter and reconstructed data along China coast

Science.gov (United States)

Du, L.; Shi, H.; Zhang, S.

2017-12-01

Acting as the typical shelf seas in northwest Pacific Ocean, regional sea level along China coasts exhibits complicated and multiscale spatial-temporal characteristics under circumstance of global change. In this paper, sea level variability is investigated with tide gauges records, satellite altimetry data, reconstructed sea surface height, and CMIP simulation fields. Sea level exhibits the interannual variability imposing on a remarkable sea level rising in the China seas and coastal region, although its seasonal signals are significant as the results of global ocean. Sea level exhibits faster rising rate during the satellite altimetry era, nearly twice to the rate during the last sixty years. AVISO data and reconstructed sea surface heights illustrate good correlation coefficient, more than 0.8. Interannual sea level variation is mainly modulated by the low-frequency variability of wind fields over northern Pacific Ocean by local and remote processes. Meanwhile sea level varies obviously by the transport fluctuation and bimodality path of Kuroshio. Its variability possibly linked to internal variability of the ocean-atmosphere system influenced by ENSO oscillation. China Sea level have been rising during the 20th century, and are projected to continue to rise during this century. Sea level can reach the highest extreme level in latter half of 21st century. Modeled sea level including regional sea level projection combined with the IPCC climate scenarios play a significant role on coastal storm surge evolution. The vulnerable regions along the ECS coast will suffer from the increasing storm damage with sea level variations.

Increasing Cone-beam projection usage by temporal fitting

DEFF Research Database (Denmark)

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

2010-01-01

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

Multi-sheet surface rebinning methods for reconstruction from asymmetrically truncated cone beam projections: I. Approximation and optimality

International Nuclear Information System (INIS)

Betcke, Marta M; Lionheart, William R B

2013-01-01

The mechanical motion of the gantry in conventional cone beam CT scanners restricts the speed of data acquisition in applications with near real time requirements. A possible resolution of this problem is to replace the moving source detector assembly with static parts that are electronically activated. An example of such a system is the Rapiscan Systems RTT80 real time tomography scanner, with a static ring of sources and axially offset static cylinder of detectors. A consequence of such a design is asymmetrical axial truncation of the cone beam projections resulting, in the sense of integral geometry, in severely incomplete data. In particular we collect data only in a fraction of the Tam–Danielsson window, hence the standard cone beam reconstruction techniques do not apply. In this work we propose a family of multi-sheet surface rebinning methods for reconstruction from such truncated projections. The proposed methods combine analytical and numerical ideas utilizing linearity of the ray transform to reconstruct data on multi-sheet surfaces, from which the volumetric image is obtained through deconvolution. In this first paper in the series, we discuss the rebinning to multi-sheet surfaces. In particular we concentrate on the underlying transforms on multi-sheet surfaces and their approximation with data collected by offset multi-source scanning geometries like the RTT. The optimal multi-sheet surface and the corresponding rebinning function are found as a solution of a variational problem. In the case of the quadratic objective, the variational problem for the optimal rebinning pair can be solved by a globally convergent iteration. Examples of optimal rebinning pairs are computed for different trajectories. We formulate the axial deconvolution problem for the recovery of the volumetric image from the reconstructions on multi-sheet surfaces. Efficient and stable solution of the deconvolution problem is the subject of the second paper in this series (Betcke and

A Kalman filter technique applied for medical image reconstruction

International Nuclear Information System (INIS)

Goliaei, S.; Ghorshi, S.; Manzuri, M. T.; Mortazavi, M.

2011-01-01

Medical images contain information about vital organic tissues inside of human body and are widely used for diagnoses of disease or for surgical purposes. Image reconstruction is essential for medical images for some applications such as suppression of noise or de-blurring the image in order to provide images with better quality and contrast. Due to vital rule of image reconstruction in medical sciences the corresponding algorithms with better efficiency and higher speed is desirable. Most algorithms in image reconstruction are operated on frequency domain such as the most popular one known as filtered back projection. In this paper we introduce a Kalman filter technique which is operated in time domain for medical image reconstruction. Results indicated that as the number of projection increases in both normal collected ray sum and the collected ray sum corrupted by noise the quality of reconstructed image becomes better in terms of contract and transparency. It is also seen that as the number of projection increases the error index decreases.

Comparison analysis between filtered back projection and algebraic reconstruction technique on microwave imaging

Science.gov (United States)

Ramadhan, Rifqi; Prabowo, Rian Gilang; Aprilliyani, Ria; Basari

2018-02-01

Victims of acute cancer and tumor are growing each year and cancer becomes one of the causes of human deaths in the world. Cancers or tumor tissue cells are cells that grow abnormally and turn to take over and damage the surrounding tissues. At the beginning, cancers or tumors do not have definite symptoms in its early stages, and can even attack the tissues inside of the body. This phenomena is not identifiable under visual human observation. Therefore, an early detection system which is cheap, quick, simple, and portable is essensially required to anticipate the further development of cancer or tumor. Among all of the modalities, microwave imaging is considered to be a cheaper, simple, and portable system method. There are at least two simple image reconstruction algorithms i.e. Filtered Back Projection (FBP) and Algebraic Reconstruction Technique (ART), which have been adopted in some common modalities. In this paper, both algorithms will be compared by reconstructing the image from an artificial tissue model (i.e. phantom), which has two different dielectric distributions. We addressed two performance comparisons, namely quantitative and qualitative analysis. Qualitative analysis includes the smoothness of the image and also the success in distinguishing dielectric differences by observing the image with human eyesight. In addition, quantitative analysis includes Histogram, Structural Similarity Index (SSIM), Mean Squared Error (MSE), and Peak Signal-to-Noise Ratio (PSNR) calculation were also performed. As a result, quantitative parameters of FBP might show better values than the ART. However, ART is likely more capable to distinguish two different dielectric value than FBP, due to higher contrast in ART and wide distribution grayscale level.

Value of selective MIP reconstructions of respiratory triggered 3D-TSE-MR cholangiography on a workstation versus standard MIP reconstructions and single-shot MRCP

International Nuclear Information System (INIS)

Schaible, R.; Textor, J.; Kreft, B.; Schild, H.; Neubrand, M.

2001-01-01

Comparison of anatomical visualisation and diagnostic value of selective MIP reconstructions of respiratory triggered 3D-TSE-MRCP versus standard MIP reconstructions and single-shot MRCP. Material and Methods: 50 patients with pancreaticobiliary disease were examined at 1.5 Tesla (ACS NT II, Philips Medical Systems) using a breath-hold single-shot (SS) and a respiratory triggered 3D-TSE-MRCP technique in 12 standard MIP projections. Additional selective MIP reconstructions with different slice thickness (2, 4, 10 cm) and projections were performed on a workstation. Visualization of the pancreaticobiliary system and the diagnostic value of the examinations were analysed. Results: Single-shot and 3D-TSE in standard projections showed comparable anatomical visualisation. On selective MIP reconstructions the biliary system (SS p [de

Statistical Reconstruction of Gas Oil Cuts Reconstruction statistique de coupes gazoles

Directory of Open Access Journals (Sweden)

Hudebine D.

2009-11-01

efficiently used to develop kinetic models like those employed at IFP to predict the performances of gas oil hydrotreating units. Les coupes gazoles sont des mélanges extrêmement complexes de plusieurs milliers de composés chimiques différents. De ce fait, les analyses pétrolières conventionnelles ne permettent pas d’obtenir un détail moléculaire qui serait pourtant nécessaire aux développements de modèles cinétiques robustes et prédictifs. Récemment, les techniques de chromatographie bidimensionnelle (GC2D ont entraîné un saut qualitatif important dans le domaine de la caractérisation des gazoles mais celles-ci restent des outils de R&D encore peu généralisés dans l’industrie pétrolière. Par rapport à cette problématique, le but de la reconstruction statistique de gazoles consiste donc à fournir un substitut à l’analyse GC2D en proposant de caractériser les gazoles sous la forme de matrices de fractions molaires de pseudo-composés décrits par famille chimique et nombre d’atomes de carbone. Les analyses utilisées en entrée sont la spectrométrie de masse Fitzgerald, la spéciation soufre (chromatographie monodimensionnelle couplée à un détecteur du soufre par chimiluminescence, les teneurs en azote total et azote basique qui permettent de quantifier les proportions des différentes familles chimiques représentées dans la matrice. La distillation simulée est utilisée quant à elle pour avoir une information sur la volatilité de la coupe gazole. La méthode de reconstruction proposée dans cet article se base principalement sur une distribution statistique de référence du nombre d’atomes de carbone des chaînes alkyles sur les noyaux naphténo-aromatiques. Pour chaque famille chimique, la connaissance du nombre potentiel de chaînes alkyles et l’estimation de la longueur maximale de ces chaînes permettent alors de déterminer la distribution par nombre d’atomes de carbone en dilatant la distribution de référence. Au

Maria Spławska-Korczak, Zamek krzyżacki w Świeciu. Próba rekonstrukcji zamku wysokiego w średniowieczu [The Teutonic Order’s Castle in Schwetz. An attempt at reconstructing the High Castle in the Middle Ages], Wydawnictwo Naukowe UMK ...

OpenAIRE

Kwiatkowski, Krzyszof

2017-01-01

Maria Spławska-Korczak, Zamek krzyżacki w Świeciu. Próba rekonstrukcji zamku wysokiego w średniowieczu [ The Teutonic Order’s Castle in Schwetz. An attempt at reconstructing the High Castle in the Middle Ages ], Wydawnictwo Naukowe Uniwersytetu Mikołaja Kopernika, Toruń 2014, 222 pp. + 70 illustrations, ISBN: 978-83-231-3247-9

Multichannel algorithm for fast 3D reconstruction

International Nuclear Information System (INIS)

Rodet, Thomas; Grangeat, Pierre; Desbat, Laurent

2002-01-01

Some recent medical imaging applications such as functional imaging (PET and SPECT) or interventional imaging (CT fluoroscopy) involve increasing amounts of data. In order to reduce the image reconstruction time, we develop a new fast 3D reconstruction algorithm based on a divide and conquer approach. The proposed multichannel algorithm performs an indirect frequential subband decomposition of the image f to be reconstructed (f=Σf j ) through the filtering of the projections Rf. The subband images f j are reconstructed on a downsampled grid without information suppression. In order to reduce the computation time, we do not backproject the null filtered projections and we downsample the number of projections according to the Shannon conditions associated with the subband image. Our algorithm is based on filtering and backprojection operators. Using the same algorithms for these basic operators, our approach is three and a half times faster than a classical FBP algorithm for a 2D image 512x512 and six times faster for a 3D image 32x512x512. (author)

Integrated task plans for the Hanford Environmental Dose Reconstruction Project, June 1992 through May 1994

International Nuclear Information System (INIS)

Shipler, D.B.

1993-09-01

The purpose of the Hanford Environmental Dose Reconstruction (HEDR) Project is to estimate radiation doses from Hanford Site operations since 1944 to representative individuals. The primary objective of work to be performed through May 1994 is to determine the project's appropriate scope: space, time, radionuclides, pathways and representative individuals; determine the project's appropriate level of accuracy/level of uncertainty in dose estimates; complete model and data development; and estimate doses for the Hanford Thyroid Disease Study and representative individuals. A major objective of the HEDR Project is to estimate doses to the thyroid of individuals who were exposed to iodine-131. A principal pathway for many of these individuals was milk from cows that ate vegetation contaminated by iodine-131 released into the air from Hanford facilities. The plan for June 1992 through May 1994 has been prepared based on activities and budgets approved by the Technical Steering Panel (TSP) at its meetings on January 7--9, 1993 and February 25--26, 1993. The activities can be divided into three broad categories: (1) computer code and data development activities, (2) calculation of doses, and (3) technical and communication support to the TSP and the TSP Native American Working Group (NAWG). The following activities will be conducted to accomplish project objectives through May 1994

Breast EIT using a new projected image reconstruction method with multi-frequency measurements.

Science.gov (United States)

Lee, Eunjung; Ts, Munkh-Erdene; Seo, Jin Keun; Woo, Eung Je

2012-05-01

We propose a new method to produce admittivity images of the breast for the diagnosis of breast cancer using electrical impedance tomography(EIT). Considering the anatomical structure of the breast, we designed an electrode configuration where current-injection and voltage-sensing electrodes are separated in such a way that internal current pathways are approximately along the tangential direction of an array of voltage-sensing electrodes. Unlike conventional EIT imaging methods where the number of injected currents is maximized to increase the total amount of measured data, current is injected only twice between two pairs of current-injection electrodes attached along the circumferential side of the breast. For each current injection, the induced voltages are measured from the front surface of the breast using as many voltage-sensing electrodes as possible. Although this electrode configurational lows us to measure induced voltages only on the front surface of the breast,they are more sensitive to an anomaly inside the breast since such an injected current tends to produce a more uniform internal current density distribution. Furthermore, the sensitivity of a measured boundary voltage between two equipotential lines on the front surface of the breast is improved since those equipotential lines are perpendicular to the primary direction of internal current streamlines. One should note that this novel data collection method is different from those of other frontal plane techniques such as the x-ray projection and T-scan imaging methods because we do not get any data on the plane that is perpendicular to the current flow. To reconstruct admittivity images using two measured voltage data sets, a new projected image reconstruction algorithm is developed. Numerical simulations demonstrate the frequency-difference EIT imaging of the breast. The results show that the new method is promising to accurately detect and localize small anomalies inside the breast.

Breast EIT using a new projected image reconstruction method with multi-frequency measurements

International Nuclear Information System (INIS)

Lee, Eunjung; Ts, Munkh-Erdene; Seo, Jin Keun; Woo, Eung Je

2012-01-01

We propose a new method to produce admittivity images of the breast for the diagnosis of breast cancer using electrical impedance tomography (EIT). Considering the anatomical structure of the breast, we designed an electrode configuration where current-injection and voltage-sensing electrodes are separated in such a way that internal current pathways are approximately along the tangential direction of an array of voltage-sensing electrodes. Unlike conventional EIT imaging methods where the number of injected currents is maximized to increase the total amount of measured data, current is injected only twice between two pairs of current-injection electrodes attached along the circumferential side of the breast. For each current injection, the induced voltages are measured from the front surface of the breast using as many voltage-sensing electrodes as possible. Although this electrode configuration allows us to measure induced voltages only on the front surface of the breast, they are more sensitive to an anomaly inside the breast since such an injected current tends to produce a more uniform internal current density distribution. Furthermore, the sensitivity of a measured boundary voltage between two equipotential lines on the front surface of the breast is improved since those equipotential lines are perpendicular to the primary direction of internal current streamlines. One should note that this novel data collection method is different from those of other frontal plane techniques such as the x-ray projection and T-scan imaging methods because we do not get any data on the plane that is perpendicular to the current flow. To reconstruct admittivity images using two measured voltage data sets, a new projected image reconstruction algorithm is developed. Numerical simulations demonstrate the frequency-difference EIT imaging of the breast. The results show that the new method is promising to accurately detect and localize small anomalies inside the breast. (paper)

From representationism to a practical turn: a reconstruction of the historiographical field since the 1990s | Del representacionismo al giro práctico: una reconstrucción del campo historiográfico desde la década de los 90

Directory of Open Access Journals (Sweden)

Alejandro Estrella González

2005-12-01

Full Text Available This paper proposes a reconstruction of the last decade of the historiographical field, a period marked by a crisis of the dominant paradigms of social and socio-cultural history and by the struggle between different candidates to occupy this hegemonic position (new social history, textualism, critical narrativization, pragmatism and critical-practical history. Our reconstruction centres on the epistemological dimension of the debate, with an analysis of the social and theoretical bases (representationism, linguistic turn and practical turn of these postulates. | Este trabajo pretende una reconstrucción de la última década del campo historiográfico; periodo marcado por la crisis de los grandes paradigmas dominantes de la historia social y sociocultural y por la pugna entre diferentes candidatos a ocupar dicha hegemonía (nueva historia social, textualismo, narrativismo crítico, pragmatismo e historia crítico-práctica. Nuestra reconstrucción se centra en la dimensión epistemológica del debate, realizando un análisis de los fundamentos sociales y teóricos (representacionismo, giro lingüístico y giro práctico de tales propuestas.

WE-EF-207-08: Improve Cone Beam CT Using a Synchronized Moving Grid, An Inter-Projection Sensor Fusion and a Probability Total Variation Reconstruction

Energy Technology Data Exchange (ETDEWEB)

Zhang, H; Kong, V; Jin, J [Georgia Regents University Cancer Center, Augusta, GA (Georgia); Ren, L; Zhang, Y; Giles, W [Duke University Medical Center, Durham, NC (United States)

2015-06-15

Purpose: To present a cone beam computed tomography (CBCT) system, which uses a synchronized moving grid (SMOG) to reduce and correct scatter, an inter-projection sensor fusion (IPSF) algorithm to estimate the missing information blocked by the grid, and a probability total variation (pTV) algorithm to reconstruct the CBCT image. Methods: A prototype SMOG-equipped CBCT system was developed, and was used to acquire gridded projections with complimentary grid patterns in two neighboring projections. Scatter was reduced by the grid, and the remaining scatter was corrected by measuring it under the grid. An IPSF algorithm was used to estimate the missing information in a projection from data in its 2 neighboring projections. Feldkamp-Davis-Kress (FDK) algorithm was used to reconstruct the initial CBCT image using projections after IPSF processing for pTV. A probability map was generated depending on the confidence of estimation in IPSF for the regions of missing data and penumbra. pTV was finally used to reconstruct the CBCT image for a Catphan, and was compared to conventional CBCT image without using SMOG, images without using IPSF (SMOG + FDK and SMOG + mask-TV), and image without using pTV (SMOG + IPSF + FDK). Results: The conventional CBCT without using SMOG shows apparent scatter-induced cup artifacts. The approaches with SMOG but without IPSF show severe (SMOG + FDK) or additional (SMOG + TV) artifacts, possibly due to using projections of missing data. The 2 approaches with SMOG + IPSF removes the cup artifacts, and the pTV approach is superior than the FDK by substantially reducing the noise. Using the SMOG also reduces half of the imaging dose. Conclusion: The proposed technique is promising in improving CBCT image quality while reducing imaging dose.

WE-EF-207-08: Improve Cone Beam CT Using a Synchronized Moving Grid, An Inter-Projection Sensor Fusion and a Probability Total Variation Reconstruction

International Nuclear Information System (INIS)

Zhang, H; Kong, V; Jin, J; Ren, L; Zhang, Y; Giles, W

2015-01-01

Purpose: To present a cone beam computed tomography (CBCT) system, which uses a synchronized moving grid (SMOG) to reduce and correct scatter, an inter-projection sensor fusion (IPSF) algorithm to estimate the missing information blocked by the grid, and a probability total variation (pTV) algorithm to reconstruct the CBCT image. Methods: A prototype SMOG-equipped CBCT system was developed, and was used to acquire gridded projections with complimentary grid patterns in two neighboring projections. Scatter was reduced by the grid, and the remaining scatter was corrected by measuring it under the grid. An IPSF algorithm was used to estimate the missing information in a projection from data in its 2 neighboring projections. Feldkamp-Davis-Kress (FDK) algorithm was used to reconstruct the initial CBCT image using projections after IPSF processing for pTV. A probability map was generated depending on the confidence of estimation in IPSF for the regions of missing data and penumbra. pTV was finally used to reconstruct the CBCT image for a Catphan, and was compared to conventional CBCT image without using SMOG, images without using IPSF (SMOG + FDK and SMOG + mask-TV), and image without using pTV (SMOG + IPSF + FDK). Results: The conventional CBCT without using SMOG shows apparent scatter-induced cup artifacts. The approaches with SMOG but without IPSF show severe (SMOG + FDK) or additional (SMOG + TV) artifacts, possibly due to using projections of missing data. The 2 approaches with SMOG + IPSF removes the cup artifacts, and the pTV approach is superior than the FDK by substantially reducing the noise. Using the SMOG also reduces half of the imaging dose. Conclusion: The proposed technique is promising in improving CBCT image quality while reducing imaging dose

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

OpenAIRE

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

2014-01-01

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

Low dose reconstruction algorithm for differential phase contrast imaging.

Science.gov (United States)

Wang, Zhentian; Huang, Zhifeng; Zhang, Li; Chen, Zhiqiang; Kang, Kejun; Yin, Hongxia; Wang, Zhenchang; Marco, Stampanoni

2011-01-01

Differential phase contrast imaging computed tomography (DPCI-CT) is a novel x-ray inspection method to reconstruct the distribution of refraction index rather than the attenuation coefficient in weakly absorbing samples. In this paper, we propose an iterative reconstruction algorithm for DPCI-CT which benefits from the new compressed sensing theory. We first realize a differential algebraic reconstruction technique (DART) by discretizing the projection process of the differential phase contrast imaging into a linear partial derivative matrix. In this way the compressed sensing reconstruction problem of DPCI reconstruction can be transformed to a resolved problem in the transmission imaging CT. Our algorithm has the potential to reconstruct the refraction index distribution of the sample from highly undersampled projection data. Thus it can significantly reduce the dose and inspection time. The proposed algorithm has been validated by numerical simulations and actual experiments.

Practical implementation of tetrahedral mesh reconstruction in emission tomography

Science.gov (United States)

Boutchko, R.; Sitek, A.; Gullberg, G. T.

2013-05-01

This paper presents a practical implementation of image reconstruction on tetrahedral meshes optimized for emission computed tomography with parallel beam geometry. Tetrahedral mesh built on a point cloud is a convenient image representation method, intrinsically three-dimensional and with a multi-level resolution property. Image intensities are defined at the mesh nodes and linearly interpolated inside each tetrahedron. For the given mesh geometry, the intensities can be computed directly from tomographic projections using iterative reconstruction algorithms with a system matrix calculated using an exact analytical formula. The mesh geometry is optimized for a specific patient using a two stage process. First, a noisy image is reconstructed on a finely-spaced uniform cloud. Then, the geometry of the representation is adaptively transformed through boundary-preserving node motion and elimination. Nodes are removed in constant intensity regions, merged along the boundaries, and moved in the direction of the mean local intensity gradient in order to provide higher node density in the boundary regions. Attenuation correction and detector geometric response are included in the system matrix. Once the mesh geometry is optimized, it is used to generate the final system matrix for ML-EM reconstruction of node intensities and for visualization of the reconstructed images. In dynamic PET or SPECT imaging, the system matrix generation procedure is performed using a quasi-static sinogram, generated by summing projection data from multiple time frames. This system matrix is then used to reconstruct the individual time frame projections. Performance of the new method is evaluated by reconstructing simulated projections of the NCAT phantom and the method is then applied to dynamic SPECT phantom and patient studies and to a dynamic microPET rat study. Tetrahedral mesh-based images are compared to the standard voxel-based reconstruction for both high and low signal-to-noise ratio

Practical implementation of tetrahedral mesh reconstruction in emission tomography

International Nuclear Information System (INIS)

Boutchko, R; Gullberg, G T; Sitek, A

2013-01-01

This paper presents a practical implementation of image reconstruction on tetrahedral meshes optimized for emission computed tomography with parallel beam geometry. Tetrahedral mesh built on a point cloud is a convenient image representation method, intrinsically three-dimensional and with a multi-level resolution property. Image intensities are defined at the mesh nodes and linearly interpolated inside each tetrahedron. For the given mesh geometry, the intensities can be computed directly from tomographic projections using iterative reconstruction algorithms with a system matrix calculated using an exact analytical formula. The mesh geometry is optimized for a specific patient using a two stage process. First, a noisy image is reconstructed on a finely-spaced uniform cloud. Then, the geometry of the representation is adaptively transformed through boundary-preserving node motion and elimination. Nodes are removed in constant intensity regions, merged along the boundaries, and moved in the direction of the mean local intensity gradient in order to provide higher node density in the boundary regions. Attenuation correction and detector geometric response are included in the system matrix. Once the mesh geometry is optimized, it is used to generate the final system matrix for ML-EM reconstruction of node intensities and for visualization of the reconstructed images. In dynamic PET or SPECT imaging, the system matrix generation procedure is performed using a quasi-static sinogram, generated by summing projection data from multiple time frames. This system matrix is then used to reconstruct the individual time frame projections. Performance of the new method is evaluated by reconstructing simulated projections of the NCAT phantom and the method is then applied to dynamic SPECT phantom and patient studies and to a dynamic microPET rat study. Tetrahedral mesh-based images are compared to the standard voxel-based reconstruction for both high and low signal-to-noise ratio

DG TOMO: A new method for tomographic reconstruction

International Nuclear Information System (INIS)

Freitas, D. de; Feschet, F.; Cachin, F.; Geissler, B.; Bapt, A.; Karidioula, I.; Martin, C.; Kelly, A.; Mestas, D.; Gerard, Y.; Reveilles, J.P.; Maublant, J.

2006-01-01

Aim: FBP and OSEM are the most popular tomographic reconstruction methods in scintigraphy. FBP is a simple method but artifacts of reconstruction are generated which corrections induce degradation of the spatial resolution. OSEM takes account of statistical fluctuations but noise strongly increases after a certain number of iterations. We compare a new method of tomographic reconstruction based on discrete geometry (DG TOMO) to FBP and OSEM. Materials and methods: Acquisitions were performed on a three-head gamma-camera (Philips) with a NEMA Phantom containing six spheres of sizes from 10 to 37 mm inner diameter, filled with around 325 MBq/l of technetium-99 m. The spheres were positioned in water containing 3 MBq/l of technetium-99 m. Acquisitions were realized during a 180 o -rotation around the phantom by 25-s steps. DG TOMO has been developed in our laboratory in order to minimize the number of projections at acquisition. Two tomographic reconstructions utilizing 32 and 16 projections with FBP, OSEM and DG TOMO were performed and transverse slices were compared. Results: FBP with 32 projections detects only the activity in the three largest spheres (diameter ≥22 mm). With 16 projections, the star effect is predominant and the contrast of the third sphere is very low. OSEM with 32 projections provides a better image but the three smallest spheres (diameter ≤17 mm) are difficult to distinguish. With 16 projections, the three smaller spheres are not detectable. The results of DG TOMO are similar to OSEM. Conclusion: Since the parameters of DG TOMO can be further optimized, this method appears as a promising alternative for tomoscintigraphy reconstruction

Spiral scan long object reconstruction through PI line reconstruction

International Nuclear Information System (INIS)

Tam, K C; Hu, J; Sourbelle, K

2004-01-01

The response of a point object in a cone beam (CB) spiral scan is analysed. Based on the result, a reconstruction algorithm for long object imaging in spiral scan cone beam CT is developed. A region-of-interest (ROI) of the long object is scanned with a detector smaller than the ROI, and a portion of it can be reconstructed without contamination from overlaying materials. The top and bottom surfaces of the ROI are defined by two sets of PI lines near the two ends of the spiral path. With this novel definition of the top and bottom ROI surfaces and through the use of projective geometry, it is straightforward to partition the cone beam image into regions corresponding to projections of the ROI, the overlaying objects or both. This also simplifies computation at source positions near the spiral ends, and makes it possible to reduce radiation exposure near the spiral ends substantially through simple hardware collimation. Simulation results to validate the algorithm are presented

Image quality of ct angiography using model-based iterative reconstruction in infants with congenital heart disease: Comparison with filtered back projection and hybrid iterative reconstruction

Energy Technology Data Exchange (ETDEWEB)

Jia, Qianjun, E-mail: jiaqianjun@126.com [Southern Medical University, Guangzhou, Guangdong (China); Department of Radiology, Guangdong General Hospital, Guangdong Academy of Medical Sciences, Guangzhou, Guangdong (China); Department of Catheterization Lab, Guangdong Cardiovascular Institute, Guangdong Provincial Key Laboratory of South China Structural Heart Disease, Guangdong General Hospital, Guangdong Academy of Medical Sciences, Guangzhou, Guangdong (China); Zhuang, Jian, E-mail: zhuangjian5413@tom.com [Department of Cardiac Surgery, Guangdong Cardiovascular Institute, Guangdong Provincial Key Laboratory of South China Structural Heart Disease, Guangdong General Hospital, Guangdong Academy of Medical Sciences, Guangzhou, Guangdong (China); Jiang, Jun, E-mail: 81711587@qq.com [Department of Radiology, Shenzhen Second People’s Hospital, Shenzhen, Guangdong (China); Li, Jiahua, E-mail: 970872804@qq.com [Department of Catheterization Lab, Guangdong Cardiovascular Institute, Guangdong Provincial Key Laboratory of South China Structural Heart Disease, Guangdong General Hospital, Guangdong Academy of Medical Sciences, Guangzhou, Guangdong (China); Huang, Meiping, E-mail: huangmeiping_vip@163.com [Department of Catheterization Lab, Guangdong Cardiovascular Institute, Guangdong Provincial Key Laboratory of South China Structural Heart Disease, Guangdong General Hospital, Guangdong Academy of Medical Sciences, Guangzhou, Guangdong (China); Southern Medical University, Guangzhou, Guangdong (China); Liang, Changhong, E-mail: cjr.lchh@vip.163.com [Department of Radiology, Guangdong General Hospital, Guangdong Academy of Medical Sciences, Guangzhou, Guangdong (China); Southern Medical University, Guangzhou, Guangdong (China)

2017-01-15

Purpose: To compare the image quality, rate of coronary artery visualization and diagnostic accuracy of 256-slice multi-detector computed tomography angiography (CTA) with prospective electrocardiographic (ECG) triggering at a tube voltage of 80 kVp between 3 reconstruction algorithms (filtered back projection (FBP), hybrid iterative reconstruction (iDose{sup 4}) and iterative model reconstruction (IMR)) in infants with congenital heart disease (CHD). Methods: Fifty-one infants with CHD who underwent cardiac CTA in our institution between December 2014 and March 2015 were included. The effective radiation doses were calculated. Imaging data were reconstructed using the FBP, iDose{sup 4} and IMR algorithms. Parameters of objective image quality (noise, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR)); subjective image quality (overall image quality, image noise and margin sharpness); coronary artery visibility; and diagnostic accuracy for the three algorithms were measured and compared. Results: The mean effective radiation dose was 0.61 ± 0.32 mSv. Compared to FBP and iDose{sup 4}, IMR yielded significantly lower noise (P < 0.01), higher SNR and CNR values (P < 0.01), and a greater subjective image quality score (P < 0.01). The total number of coronary segments visualized was significantly higher for both iDose{sup 4} and IMR than for FBP (P = 0.002 and P = 0.025, respectively), but there was no significant difference in this parameter between iDose{sup 4} and IMR (P = 0.397). There was no significant difference in the diagnostic accuracy between the FBP, iDose{sup 4} and IMR algorithms (χ{sup 2} = 0.343, P = 0.842). Conclusions: For infants with CHD undergoing cardiac CTA, the IMR reconstruction algorithm provided significantly increased objective and subjective image quality compared with the FBP and iDose{sup 4} algorithms. However, IMR did not improve the diagnostic accuracy or coronary artery visualization compared with iDose{sup 4}.

A New Local Flap Nipple Reconstruction Technique Using Dermal Bridge and Preoperatively Designed Tattoo

Science.gov (United States)

Iwahira, Yoshiko

2017-01-01

Background: Nipple–areolar reconstruction is the final step in breast reconstruction. Reconstruction using local flaps and tattooing is useful in cases of bilateral reconstruction, a small nipple–areolar complex (NAC) as the donor site, and avoiding disturbance of the normal side and other body parts. However, this method can cause projection loss and color fading of the nipple. Moreover, the breast mound is reconstructed with an implant. Methods: We performed nipple–areolar reconstruction of 90 nipples using clover-designed flaps oriented at 120 degrees and tattooing after breast silicone implantation in 64 women. The tattoo was designed before flap operation and stained darker. Following donor site closure, a dermal flap was made as a bridge for nipple support. The nipple space was separated by the dermal flap from the breast mound and was filled with subcutaneous tissue. The size of the reconstructed nipple projection was measured postoperatively and 1 year later. The projection maintenance rate was calculated. Results: The heights of the nipple projection were 11.3 ± 1.8 mm (95% confidence interval [CI]: 10.9–11.7) just after the operation and 6.09 ± 2.4 mm (95% CI: 5.6–6.6) 1 year later. The actual range of nipple projection between these 2 heights was 5.2 ± 2.4 mm (95% CI: 4.7–5.7). The maintenance rate of the reconstructed nipple projection after 12 months was 54.1 ± 20.9 (95% CI: 49.7–58.5). The nipple color was maintained for over a year. Conclusions: Our nipple–areolar reconstruction technique could maintain the projection and color of the reconstructed nipple for a long period. Good outcomes were obtained in this implant-based breast reconstruction. PMID:28507843

Application of iterative reconstruction in dynamic studies

International Nuclear Information System (INIS)

Meikle, S.R.

1998-01-01

Full text: The conventional approach to analysing dynamic tomographic data (SPECT or PET) is to reconstruct projections corresponding to each time interval separately and then fit a suitable tracer kinetic model to the dynamic sequence (method 1 ) . This approach assumes that the tracer distribution remains static during any given time interval and, for practical reasons, filtered back-projection (FBP) is the preferred reconstruction algorithm. However, alternative approaches exist which lend themselves to iterative algorithms, such as EM. One approach is to fit the model directly to the projection data, followed by EM reconstruction of the parameter estimates (method 2). This requires that the tracer model can be expressed as a linear function of the unknown model parameters. A third alternative is to incorporate the tracer model into the reconstruction algorithm (method 3). Such an extension was described during the early development of the EM algorithm, referred to as the EM parametric image reconstruction algorithm (EM-PIRA). We have investigated these various strategies for analysing dynamic data and their relative pros and cons. Tracer modelling was performed using a general model, referred to as spectral analysis, which makes no restriction on the number of physiological compartments and satisfies the linearity requirement of method 2. A kinetic software phantom was created and used to test the convergence and noise properties of the different approaches. In summary, method 2 is the most practical as it reduces the number of reconstructions by at least an order of magnitude and provides improved signal-to-noise ratios compared with method 1. EM-PIRA allows greater flexibility in the choice of parametric images and appears to have a regularising effect on convergence. Methods 2 and 3 are also better suited to dynamic scanning with a rotating camera, as they can potentially account for changes in tracer distribution between projections

Acellular dermal matrix based nipple reconstruction: A modified technique

Directory of Open Access Journals (Sweden)

Raghavan Vidya

2017-09-01

Full Text Available Nipple areolar reconstruction (NAR has evolved with the advancement in breast reconstruction and can improve self-esteem and, consequently, patient satisfaction. Although a variety of reconstruction techniques have been described in the literature varying from nipple sharing, local flaps to alloplastic and allograft augmentation, over time, loss of nipple projection remains a major problem. Acellular dermal matrices (ADM have revolutionised breast reconstruction more recently. We discuss the use of ADM to act as a base plate and strut to give support to the base and offer nipple bulk and projection in a primary procedure of NAR with a local clover shaped dermal flap in 5 breasts (4 patients. We used 5-point Likert scales (1 = highly unsatisfied, 5 = highly satisfied to assess patient satisfaction. Median age was 46 years (range: 38–55 years. Nipple projection of 8 mm, 7 mm, and 7 mms were achieved in the unilateral cases and 6 mm in the bilateral case over a median 18 month period. All patients reported at least a 4 on the Likert scale. We had no post-operative complications. It seems that nipple areolar reconstruction [NAR] using ADM can achieve nipple projection which is considered aesthetically pleasing for patients.

Towards a fair consideration of PrEP as part of combination HIV prevention in Latin America.

Science.gov (United States)

Ravasi, Giovanni; Grinsztejn, Beatriz; Baruch, Ricardo; Guanira, Juan Vicente; Luque, Ricardo; Cáceres, Carlos F; Ghidinelli, Massimo

2016-01-01

Despite progress in scaling up antiretroviral treatment, HIV prevention strategies have not been successful in significantly curbing HIV incidence in Latin America. HIV prevention interventions need to be expanded to target the most affected key populations with a combination approach, including new high impact technologies. Oral pre-exposure prophylaxis (PrEP) is recommended as additional prevention choice for individuals at higher risk of infection and could become a cost-effective prevention tool. We discuss the barriers and solutions for a fair consideration of PrEP as part of combination HIV prevention strategies in Latin America. Although demonstration projects are ongoing or being planned in a number of countries, to date no Latin American country has implemented a public PrEP programme. The knowledge of policymakers about PrEP implementation needs to be strengthened, and programmatic guidance and cost estimate tools need to be developed to support adequate planning. Despite high levels of awareness among health providers, especially if engaged in HIV or key population care, willingness to prescribe PrEP is still low due to the lack of national policies and guidelines. Key populations, especially men who have sex with men, transgender women and sex workers, have been engaged in demonstration projects, and qualitative research shows high awareness and willingness to use PrEP, especially if accessible in the public sector for free or at affordable price. Concerns of safety, adherence, effectiveness and risk compensation need to be addressed through targeted social communication strategies to improve PrEP knowledge and stimulate demand. Alliance among policymakers, civil society and representatives from key populations, healthcare providers and researchers will be critical for the design and successful implementation of PrEP demonstration projects of locally adapted delivery models. The use of mechanisms of joint negotiation and procurement of antiretrovirals

A PET reconstruction formulation that enforces non-negativity in projection space for bias reduction in Y-90 imaging

Science.gov (United States)

Lim, Hongki; Dewaraja, Yuni K.; Fessler, Jeffrey A.

2018-02-01

Most existing PET image reconstruction methods impose a nonnegativity constraint in the image domain that is natural physically, but can lead to biased reconstructions. This bias is particularly problematic for Y-90 PET because of the low probability positron production and high random coincidence fraction. This paper investigates a new PET reconstruction formulation that enforces nonnegativity of the projections instead of the voxel values. This formulation allows some negative voxel values, thereby potentially reducing bias. Unlike the previously reported NEG-ML approach that modifies the Poisson log-likelihood to allow negative values, the new formulation retains the classical Poisson statistical model. To relax the non-negativity constraint embedded in the standard methods for PET reconstruction, we used an alternating direction method of multipliers (ADMM). Because choice of ADMM parameters can greatly influence convergence rate, we applied an automatic parameter selection method to improve the convergence speed. We investigated the methods using lung to liver slices of XCAT phantom. We simulated low true coincidence count-rates with high random fractions corresponding to the typical values from patient imaging in Y-90 microsphere radioembolization. We compared our new methods with standard reconstruction algorithms and NEG-ML and a regularized version thereof. Both our new method and NEG-ML allow more accurate quantification in all volumes of interest while yielding lower noise than the standard method. The performance of NEG-ML can degrade when its user-defined parameter is tuned poorly, while the proposed algorithm is robust to any count level without requiring parameter tuning.

Image reconstruction in computerized tomography using the convolution method

International Nuclear Information System (INIS)

Oliveira Rebelo, A.M. de.

1984-03-01

In the present work an algoritin was derived, using the analytical convolution method (filtered back-projection) for two-dimensional or three-dimensional image reconstruction in computerized tomography applied to non-destructive testing and to the medical use. This mathematical model is based on the analytical Fourier transform method for image reconstruction. This model consists of a discontinuous system formed by an NxN array of cells (pixels). The attenuation in the object under study of a colimated gamma ray beam has been determined for various positions and incidence angles (projections) in terms of the interaction of the beam with the intercepted pixels. The contribution of each pixel to beam attenuation was determined using the weight function W ij which was used for simulated tests. Simulated tests using standard objects with attenuation coefficients in the range of 0,2 to 0,7 cm -1 were carried out using cell arrays of up to 25x25. One application was carried out in the medical area simulating image reconstruction of an arm phantom with attenuation coefficients in the range of 0,2 to 0,5 cm -1 using cell arrays of 41x41. The simulated results show that, in objects with a great number of interfaces and great variations of attenuation coefficients at these interfaces, a good reconstruction is obtained with the number of projections equal to the reconstruction matrix dimension. A good reconstruction is otherwise obtained with fewer projections. (author) [pt

Image reconstruction from limited angle Compton camera data

International Nuclear Information System (INIS)

Tomitani, T.; Hirasawa, M.

2002-01-01

The Compton camera is used for imaging the distributions of γ ray direction in a γ ray telescope for astrophysics and for imaging radioisotope distributions in nuclear medicine without the need for collimators. The integration of γ rays on a cone is measured with the camera, so that some sort of inversion method is needed. Parra found an analytical inversion algorithm based on spherical harmonics expansion of projection data. His algorithm is applicable to the full set of projection data. In this paper, six possible reconstruction algorithms that allow image reconstruction from projections with a finite range of scattering angles are investigated. Four algorithms have instability problems and two others are practical. However, the variance of the reconstructed image diverges in these two cases, so that window functions are introduced with which the variance becomes finite at a cost of spatial resolution. These two algorithms are compared in terms of variance. The algorithm based on the inversion of the summed back-projection is superior to the algorithm based on the inversion of the summed projection. (author)

Best Practices marketing relacional. Caso práctico

OpenAIRE

Cardama Otero, Maria

2016-01-01

el proyecto quiere servir de guía de buenas prácticas para el marketing digital de un comercio. Se desarrolla un caso práctico referido a una tienda de ropa infantil. This Project studies how a firm should develop a digital marketing strategy. We aim to propose ways to establish collaborative relationships to deliver value to customers and stakeholders, and see how they should be integrated in the overall value proposition. A general framework of best practices is described and applied to ...

Prediction of optimal deployment projection for transcatheter aortic valve replacement: angiographic 3-dimensional reconstruction of the aortic root versus multidetector computed tomography.

OpenAIRE

Binder Ronald K; Leipsic Jonathon; Wood David; Moore Teri; Toggweiler Stefan; Willson Alex; Gurvitch Ronen; Freeman Melanie; Webb John G

2012-01-01

BACKGROUND Identifying the optimal fluoroscopic projection of the aortic valve is important for successful transcatheter aortic valve replacement (TAVR). Various imaging modalities including multidetector computed tomography (MDCT) have been proposed for prediction of the optimal deployment projection. We evaluated a method that provides 3 dimensional angiographic reconstructions (3DA) of the aortic root for prediction of the optimal deployment angle and compared it with MDCT. METHODS AND RES...

Iterative reconstruction: how it works, how to apply it

Energy Technology Data Exchange (ETDEWEB)

Seibert, James Anthony [University of California Davis Medical Center, Department of Radiology, Sacramento, CA (United States)

2014-10-15

Computed tomography acquires X-ray projection data from multiple angles though an object to generate a tomographic rendition of its attenuation characteristics. Filtered back projection is a fast, closed analytical solution to the reconstruction process, whereby all projections are equally weighted, but is prone to deliver inadequate image quality when the dose levels are reduced. Iterative reconstruction is an algorithmic method that uses statistical and geometric models to variably weight the image data in a process that can be solved iteratively to independently reduce noise and preserve resolution and image quality. Applications of this technology in a clinical setting can result in lower dose on the order of 20-40% compared to a standard filtered back projection reconstruction for most exams. A carefully planned implementation strategy and methodological approach is necessary to achieve the goals of lower dose with uncompromised image quality. (orig.)

Ray tracing reconstruction investigation for C-arm tomosynthesis

Science.gov (United States)

Malalla, Nuhad A. Y.; Chen, Ying

2016-04-01

C-arm tomosynthesis is a three dimensional imaging technique. Both x-ray source and the detector are mounted on a C-arm wheeled structure to provide wide variety of movement around the object. In this paper, C-arm tomosynthesis was introduced to provide three dimensional information over a limited view angle (less than 180o) to reduce radiation exposure and examination time. Reconstruction algorithms based on ray tracing method such as ray tracing back projection (BP), simultaneous algebraic reconstruction technique (SART) and maximum likelihood expectation maximization (MLEM) were developed for C-arm tomosynthesis. C-arm tomosynthesis projection images of simulated spherical object were simulated with a virtual geometric configuration with a total view angle of 40 degrees. This study demonstrated the sharpness of in-plane reconstructed structure and effectiveness of removing out-of-plane blur for each reconstruction algorithms. Results showed the ability of ray tracing based reconstruction algorithms to provide three dimensional information with limited angle C-arm tomosynthesis.

Simulated annealing image reconstruction for positron emission tomography

International Nuclear Information System (INIS)

Sundermann, E.; Lemahieu, I.; Desmedt, P.

1994-01-01

In Positron Emission Tomography (PET) images have to be reconstructed from moisy projection data. The noise on the PET data can be modeled by a Poison distribution. In this paper, we present the results of using the simulated annealing technique to reconstruct PET images. Various parameter settings of the simulated annealing algorithm are discussed and optimized. The reconstructed images are of good quality and high contrast, in comparison to other reconstruction techniques. (authors)

Reconstruction of tomographic images from projections of a small number of views by means of mathematical programming

International Nuclear Information System (INIS)

Kobayashi, Fujio; Yamaguchi, Shoichiro

1985-01-01

Fundamental studies have been made on the application of mathematical programming to the reconstruction of tomographic images from projections of a small number of views without requiring any circular symmetry nor periodicity. Linear programming and quadratic programming were applied to minimize the quadratic sum of the residue and to finally obtain optimized reconstruction images. The mathematical algorithms were verified by the method of computer simulation, and the relationship between the number of picture elements and the number of iterations necessary for convergence was also investigated. The methods of linear programming and quadratic programming require fairly simple mathematical procedures, and strict solutions can be obtained within a finite number of iterations. Their only draw back is the requirement of a large quantity of computer memory. But this problem will be desolved by the advent of large fast memory devices in the near future. (Aoki, K.)

An extension to artifact-free projection overlaps

International Nuclear Information System (INIS)

Lin, Jianyu

2015-01-01

Purpose: In multipinhole single photon emission computed tomography, the overlapping of projections has been used to increase sensitivity. Avoiding artifacts in the reconstructed image associated with projection overlaps (multiplexing) is a critical issue. In our previous report, two types of artifact-free projection overlaps, i.e., projection overlaps that do not lead to artifacts in the reconstructed image, were formally defined and proved, and were validated via simulations. In this work, a new proposition is introduced to extend the previously defined type-II artifact-free projection overlaps so that a broader range of artifact-free overlaps is accommodated. One practical purpose of the new extension is to design a baffle window multipinhole system with artifact-free projection overlaps. Methods: First, the extended type-II artifact-free overlap was theoretically defined and proved. The new proposition accommodates the situation where the extended type-II artifact-free projection overlaps can be produced with incorrectly reconstructed portions in the reconstructed image. Next, to validate the theory, the extended-type-II artifact-free overlaps were employed in designing the multiplexing multipinhole spiral orbit imaging systems with a baffle window. Numerical validations were performed via simulations, where the corresponding 1-pinhole nonmultiplexing reconstruction results were used as the benchmark for artifact-free reconstructions. The mean square error (MSE) was the metric used for comparisons of noise-free reconstructed images. Noisy reconstructions were also performed as part of the validations. Results: Simulation results show that for noise-free reconstructions, the MSEs of the reconstructed images of the artifact-free multiplexing systems are very similar to those of the corresponding 1-pinhole systems. No artifacts were observed in the reconstructed images. Therefore, the testing results for artifact-free multiplexing systems designed using the

A two-step Hilbert transform method for 2D image reconstruction

International Nuclear Information System (INIS)

Noo, Frederic; Clackdoyle, Rolf; Pack, Jed D

2004-01-01

The paper describes a new accurate two-dimensional (2D) image reconstruction method consisting of two steps. In the first step, the backprojected image is formed after taking the derivative of the parallel projection data. In the second step, a Hilbert filtering is applied along certain lines in the differentiated backprojection (DBP) image. Formulae for performing the DBP step in fan-beam geometry are also presented. The advantage of this two-step Hilbert transform approach is that in certain situations, regions of interest (ROIs) can be reconstructed from truncated projection data. Simulation results are presented that illustrate very similar reconstructed image quality using the new method compared to standard filtered backprojection, and that show the capability to correctly handle truncated projections. In particular, a simulation is presented of a wide patient whose projections are truncated laterally yet for which highly accurate ROI reconstruction is obtained

Ultra-Fast Image Reconstruction of Tomosynthesis Mammography Using GPU.

Science.gov (United States)

Arefan, D; Talebpour, A; Ahmadinejhad, N; Kamali Asl, A

2015-06-01

Digital Breast Tomosynthesis (DBT) is a technology that creates three dimensional (3D) images of breast tissue. Tomosynthesis mammography detects lesions that are not detectable with other imaging systems. If image reconstruction time is in the order of seconds, we can use Tomosynthesis systems to perform Tomosynthesis-guided Interventional procedures. This research has been designed to study ultra-fast image reconstruction technique for Tomosynthesis Mammography systems using Graphics Processing Unit (GPU). At first, projections of Tomosynthesis mammography have been simulated. In order to produce Tomosynthesis projections, it has been designed a 3D breast phantom from empirical data. It is based on MRI data in its natural form. Then, projections have been created from 3D breast phantom. The image reconstruction algorithm based on FBP was programmed with C++ language in two methods using central processing unit (CPU) card and the Graphics Processing Unit (GPU). It calculated the time of image reconstruction in two kinds of programming (using CPU and GPU).

Ultra-Fast Image Reconstruction of Tomosynthesis Mammography Using GPU

Directory of Open Access Journals (Sweden)

Arefan D

2015-06-01

Full Text Available Digital Breast Tomosynthesis (DBT is a technology that creates three dimensional (3D images of breast tissue. Tomosynthesis mammography detects lesions that are not detectable with other imaging systems. If image reconstruction time is in the order of seconds, we can use Tomosynthesis systems to perform Tomosynthesis-guided Interventional procedures. This research has been designed to study ultra-fast image reconstruction technique for Tomosynthesis Mammography systems using Graphics Processing Unit (GPU. At first, projections of Tomosynthesis mammography have been simulated. In order to produce Tomosynthesis projections, it has been designed a 3D breast phantom from empirical data. It is based on MRI data in its natural form. Then, projections have been created from 3D breast phantom. The image reconstruction algorithm based on FBP was programmed with C++ language in two methods using central processing unit (CPU card and the Graphics Processing Unit (GPU. It calculated the time of image reconstruction in two kinds of programming (using CPU and GPU.

Adaptive multiresolution method for MAP reconstruction in electron tomography

Energy Technology Data Exchange (ETDEWEB)

Acar, Erman, E-mail: erman.acar@tut.fi [Department of Signal Processing, Tampere University of Technology, P.O. Box 553, FI-33101 Tampere (Finland); BioMediTech, Tampere University of Technology, Biokatu 10, 33520 Tampere (Finland); Peltonen, Sari; Ruotsalainen, Ulla [Department of Signal Processing, Tampere University of Technology, P.O. Box 553, FI-33101 Tampere (Finland); BioMediTech, Tampere University of Technology, Biokatu 10, 33520 Tampere (Finland)

2016-11-15

3D image reconstruction with electron tomography holds problems due to the severely limited range of projection angles and low signal to noise ratio of the acquired projection images. The maximum a posteriori (MAP) reconstruction methods have been successful in compensating for the missing information and suppressing noise with their intrinsic regularization techniques. There are two major problems in MAP reconstruction methods: (1) selection of the regularization parameter that controls the balance between the data fidelity and the prior information, and (2) long computation time. One aim of this study is to provide an adaptive solution to the regularization parameter selection problem without having additional knowledge about the imaging environment and the sample. The other aim is to realize the reconstruction using sequences of resolution levels to shorten the computation time. The reconstructions were analyzed in terms of accuracy and computational efficiency using a simulated biological phantom and publically available experimental datasets of electron tomography. The numerical and visual evaluations of the experiments show that the adaptive multiresolution method can provide more accurate results than the weighted back projection (WBP), simultaneous iterative reconstruction technique (SIRT), and sequential MAP expectation maximization (sMAPEM) method. The method is superior to sMAPEM also in terms of computation time and usability since it can reconstruct 3D images significantly faster without requiring any parameter to be set by the user. - Highlights: • An adaptive multiresolution reconstruction method is introduced for electron tomography. • The method provides more accurate results than the conventional reconstruction methods. • The missing wedge and noise problems can be compensated by the method efficiently.

Accelerated Compressed Sensing Based CT Image Reconstruction.

Science.gov (United States)

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

2015-01-01

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

Accelerated Compressed Sensing Based CT Image Reconstruction

Directory of Open Access Journals (Sweden)

SayedMasoud Hashemi

2015-01-01

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

Simulated annealing image reconstruction for positron emission tomography

Energy Technology Data Exchange (ETDEWEB)

Sundermann, E; Lemahieu, I; Desmedt, P [Department of Electronics and Information Systems, University of Ghent, St. Pietersnieuwstraat 41, B-9000 Ghent, Belgium (Belgium)

1994-12-31

In Positron Emission Tomography (PET) images have to be reconstructed from moisy projection data. The noise on the PET data can be modeled by a Poison distribution. In this paper, we present the results of using the simulated annealing technique to reconstruct PET images. Various parameter settings of the simulated annealing algorithm are discussed and optimized. The reconstructed images are of good quality and high contrast, in comparison to other reconstruction techniques. (authors). 11 refs., 2 figs.

Medical image reconstruction. A conceptual tutorial

International Nuclear Information System (INIS)

Zeng, Gengsheng Lawrence

2010-01-01

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

Building credibility in public studies: Lessons learned from the Hanford environmental Dose Reconstruction project may apply to all public studies

International Nuclear Information System (INIS)

Till, J.E.

1995-01-01

This article describes the process by which the author came to recognize the importance of openness to the public in environmental studies, during the Hanford Environmental Dose Reconstruction Project. Using the Dose reconstruction public involvement, the article goes on to describe a general guide to the construction of a new, positive framework for conducting future public studies. The steps include the following: putting the public in the study; building credibility into a public study (1 -search for proof in historical records; 2-define the domain and the exposed population; 3-characterize the material released; 4-identify key materials, pathways and receptors; 5-encouraging public participation; 6 -explaining the meaning of the results) and reconciling scientific and public issues

Building credibility in public studies: Lessons learned from the Hanford environmental Dose Reconstruction project may apply to all public studies

Energy Technology Data Exchange (ETDEWEB)

Till, J.E. [Radiological Assessment Corp., Neeses, SC (United States)

1995-09-01

This article describes the process by which the author came to recognize the importance of openness to the public in environmental studies, during the Hanford Environmental Dose Reconstruction Project. Using the Dose reconstruction public involvement, the article goes on to describe a general guide to the construction of a new, positive framework for conducting future public studies. The steps include the following: putting the public in the study; building credibility into a public study (1 -search for proof in historical records; 2-define the domain and the exposed population; 3-characterize the material released; 4-identify key materials, pathways and receptors; 5-encouraging public participation; 6 -explaining the meaning of the results) and reconciling scientific and public issues.

Reconstruction of emission coefficients for a non-axisymmetric coupling arc by algebraic reconstruction technique

International Nuclear Information System (INIS)

Zhang Guangjun; Xiong Jun; Gao Hongming; Wu Lin

2011-01-01

A preliminary investigation of tomographic reconstruction of an asymmetric arc plasma has been carried out. The objective of this work aims at reconstructing emission coefficients of a non-axisymmetric coupling arc from measured intensities by means of an algebraic reconstruction technique (ART). In order to define the optimal experimental scheme for good quality with limited views, the dependence of the reconstruction quality on three configurations (four, eight, ten projection angles) are presented and discussed via a displaced Gaussian model. Then, the emission coefficients of a free burning arc are reconstructed by the ART with the ten-view configuration and an Abel inversion, respectively, and good agreement is obtained. Finally, the emission coefficient profiles of the coupling arc are successfully achieved with the ten-view configuration. The results show that the distribution of emission coefficient for the coupling arc is different from centrosymmetric shape. The ART is perfectly suitable for reconstructing emission coefficients of the coupling arc with the ten-view configuration, proving the feasibility and utility of the ART to characterize an asymmetric arc.

Computational model design specification for Phase 1 of the Hanford Environmental Dose Reconstruction Project

Energy Technology Data Exchange (ETDEWEB)

Napier, B.A.

1991-07-01

The objective of the Hanford Environmental Dose Reconstruction (HEDR) Project is to estimate the radiation dose that individuals could have received as a result of emission from nuclear operations at Hanford since their inception in 1944. The purpose of this report is to outline the basic algorithm and necessary computer calculations to be used to calculate radiation doses specific and hypothetical individuals in the vicinity of Hanford. The system design requirements, those things that must be accomplished, are defined. The system design specifications, the techniques by which those requirements are met, are outlined. Included are the basic equations, logic diagrams, and preliminary definition of the nature of each input distribution. 4 refs., 10 figs., 9 tabs.

Computational model design specification for Phase 1 of the Hanford Environmental Dose Reconstruction Project

International Nuclear Information System (INIS)

Napier, B.A.

1991-07-01

The objective of the Hanford Environmental Dose Reconstruction (HEDR) Project is to estimate the radiation dose that individuals could have received as a result of emission from nuclear operations at Hanford since their inception in 1944. The purpose of this report is to outline the basic algorithm and necessary computer calculations to be used to calculate radiation doses specific and hypothetical individuals in the vicinity of Hanford. The system design requirements, those things that must be accomplished, are defined. The system design specifications, the techniques by which those requirements are met, are outlined. Included are the basic equations, logic diagrams, and preliminary definition of the nature of each input distribution. 4 refs., 10 figs., 9 tabs

Project management process.

Science.gov (United States)

2007-03-01

This course provides INDOT staff with foundational knowledge and skills in project management principles and methodologies. INDOTs project management processes provide the tools for interdisciplinary teams to efficiently and effectively deliver pr...

Vertex Reconstruction for AEGIS’ FACT Detector

CERN Document Server

Themistokleous, Neofytos

2017-01-01

My project dealt with the development of a vertex reconstruction technique to discriminate antihydrogen from background signals in the AEGIS apparatus. It involved the creation of a Toy Monte-Carlo to simulate particle annihilation events, and a vertex reconstruction utility based on the Bayesian theory of probability. The first results based on 107 generated events with single track in the detector are encouraging. For such events, the algorithm can reconstruct the z-coordinate accurately , while for the r-coordinate the result is less accurate.

Study of reconstruction methods for a time projection chamber with GEM gas amplification system

Energy Technology Data Exchange (ETDEWEB)

Diener, R.

2006-12-15

A new e{sup +}e{sup -} linear collider with an energy range up to 1TeV is planned in an international collaboration: the International Linear Collider (ILC). This collider will be able to do precision measurements of the Higgs particle and of physics beyond the Standard Model. In the Large Detector Concept (LDC) - which is one proposal for a detector at the ILC - a Time Projection Chamber (TPC) is foreseen as the main tracking device. To meet the requirements on the resolution and to be able to work in the environment at the ILC, the application of new gas amplification technologies in the TPC is necessary. One option is an amplification system based on Gas Electron Multipliers (GEMs). Due to the - in comparison with older technologies - small spatial width of the signals, this technology poses new requirements on the readout structures and the reconstruction methods. In this work, the performance and the systematics of different reconstruction methods have been studied, based on data measured with a TPC prototype in high magnetic fields of up to 4T and data from a Monte Carlo simulation. The latest results of the achievable point resolution are presented and their limitations have been investigated. (orig.)

Study of reconstruction methods for a time projection chamber with GEM gas amplification system

International Nuclear Information System (INIS)

Diener, R.

2006-12-01

A new e + e - linear collider with an energy range up to 1TeV is planned in an international collaboration: the International Linear Collider (ILC). This collider will be able to do precision measurements of the Higgs particle and of physics beyond the Standard Model. In the Large Detector Concept (LDC) - which is one proposal for a detector at the ILC - a Time Projection Chamber (TPC) is foreseen as the main tracking device. To meet the requirements on the resolution and to be able to work in the environment at the ILC, the application of new gas amplification technologies in the TPC is necessary. One option is an amplification system based on Gas Electron Multipliers (GEMs). Due to the - in comparison with older technologies - small spatial width of the signals, this technology poses new requirements on the readout structures and the reconstruction methods. In this work, the performance and the systematics of different reconstruction methods have been studied, based on data measured with a TPC prototype in high magnetic fields of up to 4T and data from a Monte Carlo simulation. The latest results of the achievable point resolution are presented and their limitations have been investigated. (orig.)

Analytical inversion formula for uniformly attenuated fan-beam projections

International Nuclear Information System (INIS)

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

1997-01-01

In deriving algorithms to reconstruct single photon emission computed tomography (SPECT) projection data, it is important that the algorithm compensates for photon attenuation in order to obtain quantitative reconstruction results. A convolution backprojection algorithm was derived by Tretiak and Metz to reconstruct two-dimensional (2-D) transaxial slices from uniformly attenuated parallel-beam projections. Using transformation of coordinates, this algorithm can be modified to obtain a formulation useful to reconstruct uniformly attenuated fan-beam projections. Unlike that for parallel-beam projections, this formulation does not produce a filtered backprojection reconstruction algorithm but instead has a formulation that is an inverse integral operator with a spatially varying kernel. This algorithm thus requires more computation time than does the filtered backprojection reconstruction algorithm for the uniformly attenuated parallel-beam case. However, the fan-beam reconstructions demonstrate the same image quality as that of parallel-beam reconstructions

Dynamic SPECT reconstruction from few projections: a sparsity enforced matrix factorization approach

Science.gov (United States)

Ding, Qiaoqiao; Zan, Yunlong; Huang, Qiu; Zhang, Xiaoqun

2015-02-01

The reconstruction of dynamic images from few projection data is a challenging problem, especially when noise is present and when the dynamic images are vary fast. In this paper, we propose a variational model, sparsity enforced matrix factorization (SEMF), based on low rank matrix factorization of unknown images and enforced sparsity constraints for representing both coefficients and bases. The proposed model is solved via an alternating iterative scheme for which each subproblem is convex and involves the efficient alternating direction method of multipliers (ADMM). The convergence of the overall alternating scheme for the nonconvex problem relies upon the Kurdyka-Łojasiewicz property, recently studied by Attouch et al (2010 Math. Oper. Res. 35 438) and Attouch et al (2013 Math. Program. 137 91). Finally our proof-of-concept simulation on 2D dynamic images shows the advantage of the proposed method compared to conventional methods.

Selection of dominant radionuclides for Phase 1 of the Hanford Environmental Dose Reconstruction Project

Energy Technology Data Exchange (ETDEWEB)

Napier, B.A.

1991-07-01

The objective of the Hanford Environmental Dose Reconstruction (HEDR) Project is to estimate the radiation dose that individuals could have received as a result of emissions from nuclear operations at Hanford since their inception in 1944. A vital step in the estimation of radiation doses is the determination of the source term,'' that is, the quantities of radionuclides that were released to the environment from the various Hanford operations. Hanford operations have at various times involved hundreds of different radionuclides, some in relatively large quantities. Those radionuclides present in the largest quantities, although significant from an operational handling point of view, may not necessarily have been those of greatest concern for offsite radiation dose. This report documents the selection of the dominant radionuclides (those that may have resulted in the largest portion of the received doses) in the source term for Phase 1 of the HEDR Project, that is, for atmospheric releases from 1944 through 1947 and for surface water releases from 1964 through 1966. 15 refs., 3 figs., 10 tabs.

High resolution x-ray CMT: Reconstruction methods

Energy Technology Data Exchange (ETDEWEB)

Brown, J.K.

1997-02-01

This paper qualitatively discusses the primary characteristics of methods for reconstructing tomographic images from a set of projections. These reconstruction methods can be categorized as either {open_quotes}analytic{close_quotes} or {open_quotes}iterative{close_quotes} techniques. Analytic algorithms are derived from the formal inversion of equations describing the imaging process, while iterative algorithms incorporate a model of the imaging process and provide a mechanism to iteratively improve image estimates. Analytic reconstruction algorithms are typically computationally more efficient than iterative methods; however, analytic algorithms are available for a relatively limited set of imaging geometries and situations. Thus, the framework of iterative reconstruction methods is better suited for high accuracy, tomographic reconstruction codes.

Plant Reliability - an Integrated System for Management (PR-ISM)

International Nuclear Information System (INIS)

Aukeman, M.C.; Leininger, E.G.; Carr, P.

1984-01-01

The Toledo Edison Company, located in Toledo, Ohio, United States of America, recently implemented a comprehensive maintenance management information system for the Davis-Besse Nuclear Power Station. The system is called PR-ISM, meaning Plant Reliability - An Integrated System for Management. PR-ISM provides the tools needed by station management to effectively plan and control maintenance and other plant activities. The PR-ISM system as it exists today consists of four integrated computer applications: equipment data base maintenance, maintenance work order control, administrative activity tracking, and technical specification compliance. PR-ISM is designed as an integrated on-line system and incorporates strong human factors features. PR-ISM provides each responsible person information to do his job on a daily basis and to look ahead towards future events. It goes beyond 'after the fact' reporting. In this respect, PR-ISM is an 'interactive' control system which: captures work requirements and commitments as they are identified, provides accurate and up-to-date status immediately to those who need it, simplifies paperwork and reduces the associated time delays, provides the information base for work management and reliability analysis, and improves productivity by replacing clerical tasks and consolidating maintenance activities. The functional and technical features of PR-ISM, the experience of Toledo Edison during the first year of operation, and the factors which led to the success of the development project are highlighted. (author)

Tomographic image reconstruction using Artificial Neural Networks

International Nuclear Information System (INIS)

Paschalis, P.; Giokaris, N.D.; Karabarbounis, A.; Loudos, G.K.; Maintas, D.; Papanicolas, C.N.; Spanoudaki, V.; Tsoumpas, Ch.; Stiliaris, E.

2004-01-01

A new image reconstruction technique based on the usage of an Artificial Neural Network (ANN) is presented. The most crucial factor in designing such a reconstruction system is the network architecture and the number of the input projections needed to reconstruct the image. Although the training phase requires a large amount of input samples and a considerable CPU time, the trained network is characterized by simplicity and quick response. The performance of this ANN is tested using several image patterns. It is intended to be used together with a phantom rotating table and the γ-camera of IASA for SPECT image reconstruction

PrP Knockout Cells Expressing Transmembrane PrP Resist Prion Infection.

Science.gov (United States)

Marshall, Karen E; Hughson, Andrew; Vascellari, Sarah; Priola, Suzette A; Sakudo, Akikazu; Onodera, Takashi; Baron, Gerald S

2017-01-15

Glycosylphosphatidylinositol (GPI) anchoring of the prion protein (PrP C ) influences PrP C misfolding into the disease-associated isoform, PrP res , as well as prion propagation and infectivity. GPI proteins are found in cholesterol- and sphingolipid-rich membrane regions called rafts. Exchanging the GPI anchor for a nonraft transmembrane sequence redirects PrP C away from rafts. Previous studies showed that nonraft transmembrane PrP C variants resist conversion to PrP res when transfected into scrapie-infected N2a neuroblastoma cells, likely due to segregation of transmembrane PrP C and GPI-anchored PrP res in distinct membrane environments. Thus, it remained unclear whether transmembrane PrP C might convert to PrP res if seeded by an exogenous source of PrP res not associated with host cell rafts and without the potential influence of endogenous expression of GPI-anchored PrP C To further explore these questions, constructs containing either a C-terminal wild-type GPI anchor signal sequence or a nonraft transmembrane sequence containing a flexible linker were expressed in a cell line derived from PrP knockout hippocampal neurons, NpL2. NpL2 cells have physiological similarities to primary neurons, representing a novel and advantageous model for studying transmissible spongiform encephalopathy (TSE) infection. Cells were infected with inocula from multiple prion strains and in different biochemical states (i.e., membrane bound as in brain microsomes from wild-type mice or purified GPI-anchorless amyloid fibrils). Only GPI-anchored PrP C supported persistent PrP res propagation. Our data provide strong evidence that in cell culture GPI anchor-directed membrane association of PrP C is required for persistent PrP res propagation, implicating raft microdomains as a location for conversion. Mechanisms of prion propagation, and what makes them transmissible, are poorly understood. Glycosylphosphatidylinositol (GPI) membrane anchoring of the prion protein (PrP C

Blockwise conjugate gradient methods for image reconstruction in volumetric CT.

Science.gov (United States)

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

2012-11-01

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

Use of 3D reconstruction to correct for patient motion in SPECT

International Nuclear Information System (INIS)

Fulton, R.R.; Hutton, B.F.; Braun, M.; Ardekani, B.; Larkin, R.

1994-01-01

Patient motion occurring during data acquisition in single photon emission computed tomography (SPECT) can cause serious reconstruction artefacts. We have developed a new approach to correct for head motion in brain SPECT. Prior to motion, projections are assigned to conventional projections. When head motion occurs, it is measured by a motion monitoring system, and subsequent projection data are mapped 'virtual' projections. The appropriate position of each virtual projection is determined by applying the converse of the patient's accumulated motion to the actual camera projection. Conventional and virtual projections, taken together, form a consistent set that can be reconstructed using a three-dimensional (3D) algorithm. The technique has been tested on a range of simulated rotational movements, both within and out of the transaxial plane. For all simulated movements, the motion corrected images exhibited better agreement with a motion free reconstruction than did the uncorrected images. (Author)

Road Construction Safety Audit for Interstate Reconstruction. Volume 1.

Science.gov (United States)

1998-10-01

Traffic control alternatives associated with reconstruction projects on a rural interstate have been investigated in this research. Slab replacement projects, milling/resurfacing projects, and traffic controls in the vicinity of interstate ramps were...

Road Construction Safety Audit for Interstate Reconstruction. Volume 2.

Science.gov (United States)

1998-10-01

Traffic control alternatives associated with reconstruction projects on a rural interstate have been investigated in this research. Slab replacement projects, milling/resurfacing projects, and traffic controls in the vicinity of interstate ramps were...

Vascular diameter measurement in CT angiography: comparison of model-based iterative reconstruction and standard filtered back projection algorithms in vitro.

Science.gov (United States)

Suzuki, Shigeru; Machida, Haruhiko; Tanaka, Isao; Ueno, Eiko

2013-03-01

The purpose of this study was to evaluate the performance of model-based iterative reconstruction (MBIR) in measurement of the inner diameter of models of blood vessels and compare performance between MBIR and a standard filtered back projection (FBP) algorithm. Vascular models with wall thicknesses of 0.5, 1.0, and 1.5 mm were scanned with a 64-MDCT unit and densities of contrast material yielding 275, 396, and 542 HU. Images were reconstructed images by MBIR and FBP, and the mean diameter of each model vessel was measured by software automation. Twenty separate measurements were repeated for each vessel, and variance among the repeated measures was analyzed for determination of measurement error. For all nine model vessels, CT attenuation profiles were compared along a line passing through the luminal center on axial images reconstructed with FBP and MBIR, and the 10-90% edge rise distances at the boundary between the vascular wall and the lumen were evaluated. For images reconstructed with FBP, measurement errors were smallest for models with 1.5-mm wall thickness, except those filled with 275-HU contrast material, and errors grew as the density of the contrast material decreased. Measurement errors with MBIR were comparable to or less than those with FBP. In CT attenuation profiles of images reconstructed with MBIR, the 10-90% edge rise distances at the boundary between the lumen and vascular wall were relatively short for each vascular model compared with those of the profile curves of FBP images. MBIR is better than standard FBP for reducing reconstruction blur and improving the accuracy of diameter measurement at CT angiography.

Accelerating image reconstruction in three-dimensional optoacoustic tomography on graphics processing units.

Science.gov (United States)

Wang, Kun; Huang, Chao; Kao, Yu-Jiun; Chou, Cheng-Ying; Oraevsky, Alexander A; Anastasio, Mark A

2013-02-01

Optoacoustic tomography (OAT) is inherently a three-dimensional (3D) inverse problem. However, most studies of OAT image reconstruction still employ two-dimensional imaging models. One important reason is because 3D image reconstruction is computationally burdensome. The aim of this work is to accelerate existing image reconstruction algorithms for 3D OAT by use of parallel programming techniques. Parallelization strategies are proposed to accelerate a filtered backprojection (FBP) algorithm and two different pairs of projection/backprojection operations that correspond to two different numerical imaging models. The algorithms are designed to fully exploit the parallel computing power of graphics processing units (GPUs). In order to evaluate the parallelization strategies for the projection/backprojection pairs, an iterative image reconstruction algorithm is implemented. Computer simulation and experimental studies are conducted to investigate the computational efficiency and numerical accuracy of the developed algorithms. The GPU implementations improve the computational efficiency by factors of 1000, 125, and 250 for the FBP algorithm and the two pairs of projection/backprojection operators, respectively. Accurate images are reconstructed by use of the FBP and iterative image reconstruction algorithms from both computer-simulated and experimental data. Parallelization strategies for 3D OAT image reconstruction are proposed for the first time. These GPU-based implementations significantly reduce the computational time for 3D image reconstruction, complementing our earlier work on 3D OAT iterative image reconstruction.

Algorithms for reconstructing images for industrial applications

International Nuclear Information System (INIS)

Lopes, R.T.; Crispim, V.R.

1986-01-01

Several algorithms for reconstructing objects from their projections are being studied in our Laboratory, for industrial applications. Such algorithms are useful locating the position and shape of different composition of materials in the object. A Comparative study of two algorithms is made. The two investigated algorithsm are: The MART (Multiplicative - Algebraic Reconstruction Technique) and the Convolution Method. The comparison are carried out from the point view of the quality of the image reconstructed, number of views and cost. (Author) [pt

ESO PR Highlights in 2006

Science.gov (United States)

2007-01-01

unprecedented detailed map of a proto-disc galaxy, showing how galaxies looked like 10 billion years ago (PR 31/06). The VLT also helped to discover a large primordial (more than 10 billion years away) 'blob', explained as the early stage formation of a galaxy (PR 23/06). Not only far away galaxies are rich of surprises: also our own Galaxy was the object of investigations during 2006 and its history is now less obscure (PR 34/06 and 41/06). ESO's Very Large Telescope unveiled that the stellar cluster Messier 12 must have lost to our Milky Way galaxy close to one million low-mass stars (PR 04/06). Stealing is not uncommon in astronomy: evidence of stellar vampires - star sucking off material from another - was unearthed in the globular cluster 47 Tucanae (PR 37/06). Still closer to home, the VLT observed Schwassmann-Wachmann 3, a comet that is breaking apart and revealed many mini-comets (PR 15/06). At Paranal, a fourth Auxiliary Telescope was installed for the Very Large Telescope Interferometer (PR 51/06), and since January 2006, not only do natural stars shine: the first artificial star twinkles in the Southern Hemisphere. It does not guide the sailors (it is too faint to be seen by the unaided eye), but it conducts the eye of the present and future telescopes (PR 07/06). And 2006 proved an important year for the future project of ESO, the Extremely Large Telescope. After approval from the ESO council, the European community can now start the final design of this telescope that will without doubt revolutionise astronomy (PR 25/06 and 46/06). ESO PR Photos 2006 2006 was without doubt an explosive year: the explosion of a supernovae of Type Ia in the enchanting Hooked Galaxy was followed from the middle of 2005 for more than a year (PR 22/06) and using observations of 17 supernovae Ia astronomers could make light on the nature of such explosions, that are likely to occur at supersonic speed (PR 44/06). Supernovae are proved to be linked to X-ray flashes (PR 33/06) and to the

3D computed tomography using a microfocus X-ray source: Analysis of artifact formation in the reconstructed images using simulated as well as experimental projection data

International Nuclear Information System (INIS)

Krimmel, S.; Stephan, J.; Baumann, J.

2005-01-01

The scope of this contribution is to identify and to quantify the influence of different parameters on the formation of image artifacts in X-ray computed tomography (CT) resulting for example, from beam hardening or from partial lack of information using 3D cone beam CT. In general, the reconstructed image quality depends on a number of acquisition parameters concerning the X-ray source (e.g. X-ray spectrum), the geometrical setup (e.g. cone beam angle), the sample properties (e.g. absorption characteristics) and the detector properties. While it is difficult to distinguish the influence of different effects clearly in experimental projection data, they can be selected individually with the help of simulated projection data by varying the parameter set. The reconstruction of the 3D data set is performed with the filtered back projection algorithm according to Feldkamp, Davis and Kress for experimental as well as for simulated projection data. The experimental data are recorded with an industrial microfocus CT system which features a focal spot size of a few micrometers and uses a digital flat panel detector for data acquisition

An iterative reconstruction method of complex images using expectation maximization for radial parallel MRI

International Nuclear Information System (INIS)

Choi, Joonsung; Kim, Dongchan; Oh, Changhyun; Han, Yeji; Park, HyunWook

2013-01-01

In MRI (magnetic resonance imaging), signal sampling along a radial k-space trajectory is preferred in certain applications due to its distinct advantages such as robustness to motion, and the radial sampling can be beneficial for reconstruction algorithms such as parallel MRI (pMRI) due to the incoherency. For radial MRI, the image is usually reconstructed from projection data using analytic methods such as filtered back-projection or Fourier reconstruction after gridding. However, the quality of the reconstructed image from these analytic methods can be degraded when the number of acquired projection views is insufficient. In this paper, we propose a novel reconstruction method based on the expectation maximization (EM) method, where the EM algorithm is remodeled for MRI so that complex images can be reconstructed. Then, to optimize the proposed method for radial pMRI, a reconstruction method that uses coil sensitivity information of multichannel RF coils is formulated. Experiment results from synthetic and in vivo data show that the proposed method introduces better reconstructed images than the analytic methods, even from highly subsampled data, and provides monotonic convergence properties compared to the conjugate gradient based reconstruction method. (paper)

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

International Nuclear Information System (INIS)

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

2014-01-01

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

X-ray differential phase-contrast tomographic reconstruction with a phase line integral retrieval filter

International Nuclear Information System (INIS)

Fu, Jian; Hu, Xinhua; Li, Chen

2015-01-01

We report an alternative reconstruction technique for x-ray differential phase-contrast computed tomography (DPC-CT). This approach is based on a new phase line integral projection retrieval filter, which is rooted in the derivative property of the Fourier transform and counteracts the differential nature of the DPC-CT projections. It first retrieves the phase line integral from the DPC-CT projections. Then the standard filtered back-projection (FBP) algorithms popular in x-ray absorption-contrast CT are directly applied to the retrieved phase line integrals to reconstruct the DPC-CT images. Compared with the conventional DPC-CT reconstruction algorithms, the proposed method removes the Hilbert imaginary filter and allows for the direct use of absorption-contrast FBP algorithms. Consequently, FBP-oriented image processing techniques and reconstruction acceleration softwares that have already been successfully used in absorption-contrast CT can be directly adopted to improve the DPC-CT image quality and speed up the reconstruction

Preparation and tomographic reconstruction of an arbitrary single-photon path qubit

International Nuclear Information System (INIS)

Baek, So-Young; Kim, Yoon-Ho

2011-01-01

We report methods for preparation and tomographic reconstruction of an arbitrary single-photon path qubit. The arbitrary single-photon path qubit is prepared losslessly by passing the heralded single-photon state from spontaneous parametric down-conversion through variable beam splitter. Quantum state tomography of the single-photon path qubit is implemented by introducing path-projection measurements based on the first-order single-photon quantum interference. Using the state preparation and path-projection measurements methods for the single-photon path qubit, we demonstrate preparation and complete tomographic reconstruction of the single-photon path qubit with arbitrary purity. -- Highlights: → We report methods for preparation and tomographic reconstruction of an arbitrary single-photon path qubit. → We implement path-projection measurements based on the first-order single-photon quantum interference. → We demonstrate preparation and complete tomographic reconstruction of the single-photon path qubit with arbitrary purity.

Evaluation of digital breast tomosynthesis reconstruction algorithms using synchrotron radiation in standard geometry

International Nuclear Information System (INIS)

Bliznakova, K.; Kolitsi, Z.; Speller, R. D.; Horrocks, J. A.; Tromba, G.; Pallikarakis, N.

2010-01-01

Purpose: In this article, the image quality of reconstructed volumes by four algorithms for digital tomosynthesis, applied in the case of breast, is investigated using synchrotron radiation. Methods: An angular data set of 21 images of a complex phantom with heterogeneous tissue-mimicking background was obtained using the SYRMEP beamline at ELETTRA Synchrotron Light Laboratory, Trieste, Italy. The irradiated part was reconstructed using the multiple projection algorithm (MPA) and the filtered backprojection with ramp followed by hamming windows (FBR-RH) and filtered backprojection with ramp (FBP-R). Additionally, an algorithm for reducing the noise in reconstructed planes based on noise mask subtraction from the planes of the originally reconstructed volume using MPA (MPA-NM) has been further developed. The reconstruction techniques were evaluated in terms of calculations and comparison of the contrast-to-noise ratio (CNR) and artifact spread function. Results: It was found that the MPA-NM resulted in higher CNR, comparable with the CNR of FBP-RH for high contrast details. Low contrast objects are well visualized and characterized by high CNR using the simple MPA and the MPA-NM. In addition, the image quality of the reconstructed features in terms of CNR and visual appearance as a function of the initial number of projection images and the reconstruction arc was carried out. Slices reconstructed with more input projection images result in less reconstruction artifacts and higher detail CNR, while those reconstructed from projection images acquired in reduced angular range causes pronounced streak artifacts. Conclusions: Of the reconstruction algorithms implemented, the MPA-NM and MPA are a good choice for detecting low contrast objects, while the FBP-RH, FBP-R, and MPA-NM provide high CNR and well outlined edges in case of microcalcifications.

A preliminary examination of audience-related communications issues for the Hanford Environmental Dose Reconstruction Project

Energy Technology Data Exchange (ETDEWEB)

Holmes, C.W.

1991-04-01

The Hanford Environmental Dose Reconstruction (HEDR) Project will estimate radiation doses people may have received from exposure to radioactive materials released during past operations at the US Department of Energy's (DOE) Hanford Site near Richland, Washington. The HEDR Project was initiated in response to public concerns about possible health impacts from past releases of radioactive materials from Hanford. The TSP recognized early in the project that special mechanisms would be required to effectively communicate to the many different concerned audiences. Accordingly, the TSP directed PNL to examine methods for communicating causes and effects of uncertainties in the dose estimates. After considering the directive and discussing it with the Communications Subcommittee of the TSP, PNL undertook a broad investigation of communications methods to consider for inclusion in the TSP's current communications program. As part of this investigation, a literature review was conducted regarding risk communications. A key finding was that, in order to successfully communicate risk-related information, a thorough understanding of the knowledge level, concerns and information needs of the intended recipients (i.e., the audience) is necessary. Hence, a preliminary audience analysis was conducted as part of the present research. This report summarizes the results of this analysis. 1 ref., 9 tabs.

Evaluation of few-view reconstruction parameters for illicit substance detection using fast-neutron transmission spectroscopy

International Nuclear Information System (INIS)

Fink, C.L.; Humm, P.G.; Martin, M.M.; Micklich, B.J.

1996-01-01

The authors have evaluated the performance of an illicit substance detection system that performs image reconstruction using the Maximum Likelihood algebraic reconstruction algorithm, a fe number of projections, and relatively coarse projection and pixel resolution. This evaluation was done using receiver operator curves and simulated data from the fast-neutron transmission spectroscopy system operated in a mode to detect explosives in luggage. The results show that increasing the number of projection angles is more important than increasing the projection resolution, the reconstructed pixel resolution, of the number of iterations in the Maximum Likelihood algorithm. A 100% detection efficiency with essentially no false positives is possible for a square block of RDX explosive, a projection resolution of 2 cm, a reconstructed pixel size of 2x2 cm, and five projection angles. For rectangular shaped explosives more angles are required to obtain the same system performance

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

International Nuclear Information System (INIS)

Gao, H

2016-01-01

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

Residual motion compensation in ECG-gated interventional cardiac vasculature reconstruction

Science.gov (United States)

Schwemmer, C.; Rohkohl, C.; Lauritsch, G.; Müller, K.; Hornegger, J.

2013-06-01

Three-dimensional reconstruction of cardiac vasculature from angiographic C-arm CT (rotational angiography) data is a major challenge. Motion artefacts corrupt image quality, reducing usability for diagnosis and guidance. Many state-of-the-art approaches depend on retrospective ECG-gating of projection data for image reconstruction. A trade-off has to be made regarding the size of the ECG-gating window. A large temporal window is desirable to avoid undersampling. However, residual motion will occur in a large window, causing motion artefacts. We present an algorithm to correct for residual motion. Our approach is based on a deformable 2D-2D registration between the forward projection of an initial, ECG-gated reconstruction, and the original projection data. The approach is fully automatic and does not require any complex segmentation of vasculature, or landmarks. The estimated motion is compensated for during the backprojection step of a subsequent reconstruction. We evaluated the method using the publicly available CAVAREV platform and on six human clinical datasets. We found a better visibility of structure, reduced motion artefacts, and increased sharpness of the vessels in the compensated reconstructions compared to the initial reconstructions. At the time of writing, our algorithm outperforms the leading result of the CAVAREV ranking list. For the clinical datasets, we found an average reduction of motion artefacts by 13 ± 6%. Vessel sharpness was improved by 25 ± 12% on average.

Software Architecture Reconstruction Method, a Survey

OpenAIRE

Zainab Nayyar; Nazish Rafique

2014-01-01

Architecture reconstruction belongs to a reverse engineering process, in which we move from code to architecture level for reconstructing architecture. Software architectures are the blue prints of projects which depict the external overview of the software system. Mostly maintenance and testing cause the software to deviate from its original architecture, because sometimes for enhancing the functionality of a system the software deviates from its documented specifications, some new modules a...

On PR group classes and PR algebra membership

International Nuclear Information System (INIS)

Lebedenko, V.M.

1978-01-01

The necessary and sufficient conditions are found for the membership of Lee algebras to PR algebra class, to algebras with commutation relations of [Hsub(i), Hsub(j)]=rsub(ij)Hsub(i) (i< j) type. Due to this, a criterion is obtained for the membership of the Lee froups to PR group classes, connected and simply connected Lee groups, which Lee algebras are PR algebras

Renal Cyst Pseudoenhancement: Intraindividual Comparison Between Virtual Monochromatic Spectral Images and Conventional Polychromatic 120-kVp Images Obtained During the Same CT Examination and Comparisons Among Images Reconstructed Using Filtered Back Projection, Adaptive Statistical Iterative Reconstruction, and Model-Based Iterative Reconstruction

Science.gov (United States)

Yamada, Yoshitake; Yamada, Minoru; Sugisawa, Koichi; Akita, Hirotaka; Shiomi, Eisuke; Abe, Takayuki; Okuda, Shigeo; Jinzaki, Masahiro

2015-01-01

Abstract The purpose of this study was to compare renal cyst pseudoenhancement between virtual monochromatic spectral (VMS) and conventional polychromatic 120-kVp images obtained during the same abdominal computed tomography (CT) examination and among images reconstructed using filtered back projection (FBP), adaptive statistical iterative reconstruction (ASIR), and model-based iterative reconstruction (MBIR). Our institutional review board approved this prospective study; each participant provided written informed consent. Thirty-one patients (19 men, 12 women; age range, 59–85 years; mean age, 73.2 ± 5.5 years) with renal cysts underwent unenhanced 120-kVp CT followed by sequential fast kVp-switching dual-energy (80/140 kVp) and 120-kVp abdominal enhanced CT in the nephrographic phase over a 10-cm scan length with a random acquisition order and 4.5-second intervals. Fifty-one renal cysts (maximal diameter, 18.0 ± 14.7 mm [range, 4–61 mm]) were identified. The CT attenuation values of the cysts as well as of the kidneys were measured on the unenhanced images, enhanced VMS images (at 70 keV) reconstructed using FBP and ASIR from dual-energy data, and enhanced 120-kVp images reconstructed using FBP, ASIR, and MBIR. The results were analyzed using the mixed-effects model and paired t test with Bonferroni correction. The attenuation increases (pseudoenhancement) of the renal cysts on the VMS images reconstructed using FBP/ASIR (least square mean, 5.0/6.0 Hounsfield units [HU]; 95% confidence interval, 2.6–7.4/3.6–8.4 HU) were significantly lower than those on the conventional 120-kVp images reconstructed using FBP/ASIR/MBIR (least square mean, 12.1/12.8/11.8 HU; 95% confidence interval, 9.8–14.5/10.4–15.1/9.4–14.2 HU) (all P < .001); on the other hand, the CT attenuation values of the kidneys on the VMS images were comparable to those on the 120-kVp images. Regardless of the reconstruction algorithm, 70-keV VMS images showed

Automatic detection of patient position for incorporation in exact 3D reconstruction for emission tomography

International Nuclear Information System (INIS)

Kyme, A.; Hutton, B.; Hatton, R.; Skerrett, D.

2000-01-01

Full text: SPECT involves acquiring a set of projection images using one or more rotating gamma cameras. The projections are then reconstructed to create transverse slices. Patient motion during the scan can introduce inconsistencies into the data leading to artifacts. There remains a need for robust and effective motion correction. One approach uses the (corrupt) data itself to derive the patient position at each projection angle. Corrected data is periodically incorporated into a 3-D reconstruction. Fundamental aspects of the algorithm mechanics, particularly performance in the presence of Poisson noise, have been examined. Brain SPECT studies were simulated using a digital version of the Huffman brain phantom. Projection datasets with Poisson noise imposed, generated for different positions of the phantom, were combined and reconstructed to produce motion-corrupted reconstructions. To examine the behaviour of the cost function as the object position was changed, the corrupted re-construction was forward projected and the mean square difference (MSD) between the resulting re-projections and corresponding original projections was calculated. The ability to detect mis-positioned projections for different degrees of freedom, the importance of using dual-head camera geometry, and the effect of smoothing the original projections prior to the MSD calculation were assessed. Re-projection of the corrupt reconstruction was able to correctly identify mis-positioned projection data. The degree of movement as defined by MSD was more easily identified for translations than for rotations. Noise resulted in an increasing bias that made it difficult to distinguish the minimum MSD, particularly for z-axis rotations. This was improved by median filtering of projections. Right-angled dual-head geometry is necessary to provide stability to the algorithm and to better identify motion in all 6 degrees of freedom. These findings will assist the optimisation of a fully automated motion

Three-dimensional seed reconstruction from an incomplete data set for prostate brachytherapy

International Nuclear Information System (INIS)

Narayanan, Sreeram; Cho, Paul S; MarksII, Robert J

2004-01-01

Intra-operative dosimetry in prostate brachytherapy requires 3D coordinates of the implanted, radioactive seeds. Since CT is not readily available during the implant operation, projection x-rays are commonly used for intra-operative seed localization. Three x-ray projections are usually used. The requirement of the current seed reconstruction algorithms is that the seeds must be identified on all three projections. However, in practice this is often difficult to accomplish due to the problem of heavily clustered and overlapping seeds. We have developed an algorithm that permits seed reconstruction from an incomplete data set. Instead of all three projections, the new algorithm requires only one of the three projections to be complete. Furthermore, even if all three projections are incomplete, it can reconstruct 100% of the implanted seeds depending on how the undetected seeds are distributed among the projections. The method utilizes the principles of epipolar imaging geometry and pseudo-matching of the undetected seeds. The algorithm was successfully applied to a large number of clinical cases where seeds imperceptibly overlap in some projections

GPU accelerated CT reconstruction for clinical use: quality driven performance

Science.gov (United States)

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

2007-03-01

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

Comparison of pure and hybrid iterative reconstruction techniques with conventional filtered back projection: Image quality assessment in the cervicothoracic region

International Nuclear Information System (INIS)

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

2013-01-01

Objectives: To evaluate the impact on image quality of three different image reconstruction techniques in the cervicothoracic region: model-based iterative reconstruction (MBIR), adaptive statistical iterative reconstruction (ASIR), and filtered back projection (FBP). Methods: Forty-four patients underwent unenhanced standard-of-care clinical computed tomography (CT) examinations which included the cervicothoracic region with a 64-row multidetector CT scanner. Images were reconstructed with FBP, 50% ASIR-FBP blending (ASIR50), and MBIR. Two radiologists assessed the cervicothoracic region in a blinded manner for streak artifacts, pixilated blotchy appearances, critical reproduction of visually sharp anatomical structures (thyroid gland, common carotid artery, and esophagus), and overall diagnostic acceptability. Objective image noise was measured in the internal jugular vein. Data were analyzed using the sign test and pair-wise Student's t-test. Results: MBIR images had significant lower quantitative image noise (8.88 ± 1.32) compared to ASIR images (18.63 ± 4.19, P 0.9 for ASIR vs. FBP for both readers). MBIR images were all diagnostically acceptable. Unique features of MBIR images included pixilated blotchy appearances, which did not adversely affect diagnostic acceptability. Conclusions: MBIR significantly improves image noise and streak artifacts of the cervicothoracic region over ASIR and FBP. MBIR is expected to enhance the value of CT examinations for areas where image noise and streak artifacts are problematic

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

Directory of Open Access Journals (Sweden)

Xing Zhao

2009-01-01

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

Three-dimensional optical reconstruction of vocal fold kinematics using high-speed video with a laser projection system

Science.gov (United States)

Luegmair, Georg; Mehta, Daryush D.; Kobler, James B.; Döllinger, Michael

2015-01-01

Vocal fold kinematics and its interaction with aerodynamic characteristics play a primary role in acoustic sound production of the human voice. Investigating the temporal details of these kinematics using high-speed videoendoscopic imaging techniques has proven challenging in part due to the limitations of quantifying complex vocal fold vibratory behavior using only two spatial dimensions. Thus, we propose an optical method of reconstructing the superior vocal fold surface in three spatial dimensions using a high-speed video camera and laser projection system. Using stereo-triangulation principles, we extend the camera-laser projector method and present an efficient image processing workflow to generate the three-dimensional vocal fold surfaces during phonation captured at 4000 frames per second. Initial results are provided for airflow-driven vibration of an ex vivo vocal fold model in which at least 75% of visible laser points contributed to the reconstructed surface. The method captures the vertical motion of the vocal folds at a high accuracy to allow for the computation of three-dimensional mucosal wave features such as vibratory amplitude, velocity, and asymmetry. PMID:26087485

Comparison of the effects of model-based iterative reconstruction and filtered back projection algorithms on software measurements in pulmonary subsolid nodules.

Science.gov (United States)

Cohen, Julien G; Kim, Hyungjin; Park, Su Bin; van Ginneken, Bram; Ferretti, Gilbert R; Lee, Chang Hyun; Goo, Jin Mo; Park, Chang Min

2017-08-01

To evaluate the differences between filtered back projection (FBP) and model-based iterative reconstruction (MBIR) algorithms on semi-automatic measurements in subsolid nodules (SSNs). Unenhanced CT scans of 73 SSNs obtained using the same protocol and reconstructed with both FBP and MBIR algorithms were evaluated by two radiologists. Diameter, mean attenuation, mass and volume of whole nodules and their solid components were measured. Intra- and interobserver variability and differences between FBP and MBIR were then evaluated using Bland-Altman method and Wilcoxon tests. Longest diameter, volume and mass of nodules and those of their solid components were significantly higher using MBIR (p algorithms with respect to the diameter, volume and mass of nodules and their solid components. There were no significant differences in intra- or interobserver variability between FBP and MBIR (p > 0.05). Semi-automatic measurements of SSNs significantly differed between FBP and MBIR; however, the differences were within the range of measurement variability. • Intra- and interobserver reproducibility of measurements did not differ between FBP and MBIR. • Differences in SSNs' semi-automatic measurement induced by reconstruction algorithms were not clinically significant. • Semi-automatic measurement may be conducted regardless of reconstruction algorithm. • SSNs' semi-automated classification agreement (pure vs. part-solid) did not significantly differ between algorithms.

Sujeito, intersubjetividade e práticas de saúde Subject, intersubjectivity, and health practices

Directory of Open Access Journals (Sweden)

José Ricardo de Carvalho Mesquita Ayres

2001-01-01

Full Text Available Neste artigo se discute o conceito de sujeito utilizado nas práticas de saúde. Parte-se da tese de que a concepção de sujeito predominante no pensamento sanitário não está em sintonia com valores e pressupostos que orientam as principais propostas de renovação de conceitos e práticas de saúde na atualidade. Defende-se o caráter relacional, pragmático e reconstrutivo das identidades subjetivas, contra o caráter individualista, apriorístico e objetificado prevalente nas práticas do setor. Desdobra-se desta reflexão a defesa de transformações das práticas de saúde, com base em "giros" teórico-filosóficos, relacionados entre si: a secundarização da idéia de sujeito em favor da idéia de contextos de intersubjetividade, na construção de categorias para o conhecimento e intervenção; b subsunção do interesse pelo controle técnico das doenças na idéia mais abrangente de sucesso prático de projetos de felicidade humana, na definição das finalidades da intervenção; c transformação do cuidado, na atitude orientadora do conjunto das ações voltadas para a saúde das pessoas.This article discusses the concept of subject as used in health practices. The underlying thesis is that the predominant concept of subject in the health field is not in keeping with the values and premises currently orienting the renewal of health concepts and practices, which defend the relational, pragmatic, and reconstructive nature of subjective identities as opposed to the individualistic, a priori, and objectified approach prevailing in practice in the health sector. This reflection leads to the defense of changes in health practices, based on interrelated theoretical/philosophical twists: a as a priority, replace the notion of subject with that of contexts of intersubjectivity, in the construction of categories for knowledge and intervention; b subsume the interest in the technical control of diseases within the broader idea of practical

Exact reconstruction in 2D dynamic CT: compensation of time-dependent affine deformations

International Nuclear Information System (INIS)

Roux, Sebastien; Desbat, Laurent; Koenig, Anne; Grangeat, Pierre

2004-01-01

This work is dedicated to the reduction of reconstruction artefacts due to motion occurring during the acquisition of computerized tomographic projections. This problem has to be solved when imaging moving organs such as the lungs or the heart. The proposed method belongs to the class of motion compensation algorithms, where the model of motion is included in the reconstruction formula. We address two fundamental questions. First what conditions on the deformation are required for the reconstruction of the object from projections acquired sequentially during the deformation, and second how do we reconstruct the object from those projections. Here we answer these questions in the particular case of 2D general time-dependent affine deformations, assuming the motion parameters are known. We treat the problem of admissibility conditions on the deformation in the parallel-beam and fan-beam cases. Then we propose exact reconstruction methods based on rebinning or sequential FBP formulae for each of these geometries and present reconstructed images obtained with the fan-beam algorithm on simulated data

Neutron Scattering from fcc Pr and Pr3Tl

DEFF Research Database (Denmark)

Birgeneau, R. J.; Als-Nielsen, Jens Aage; Bucher, E.

1972-01-01

Elastic-neutron-scattering measurements on the singlet-ground-state ferromagnets fcc Pr and Pr3 Tl are reported. Both exhibit magnetic phase transitions, possibly to a simple ferromagnetic state at 20 and 11.6 °K, respectively. The transitions appear to be of second order although that in fcc Pr...

Reconstrucción de la articulación temporomandibular (ATM: prótesis aloplástica Reconstruction of the temporomandibular joint (TMJ: alloplastic prostheses

Directory of Open Access Journals (Sweden)

C. Goizueta Adame

2005-02-01

Full Text Available La incapacidad de desarrollar sistemas inertes eficaces para la sustitución completa de la articulación temporo-mandibular durante décadas ha generado una variedad de soluciones biológicas para un problema biomecánico. Los injertos autólogos no ofrecen garantías en funcionalidad, simetría, o estabilidad oclusal; resultan técnicamente más complejos y tienen mayor potencial morbilidad. El paciente candidato a reconstrucción completa de la ATM debe contar con la posibilidad de una prótesis si otras opciones fracasan. La reconstrucción aloplástica garantiza estabilidad oclusal, técnica sencilla y reproducible, estancia hospitalaria predecible y baja tasa de complicaciones con los sistemas protésicos actuales. Siempre van a existir pacientes en los que ésta sea la única opción, por lo tanto es primordial la medición de la magnitud de las fuerzas implicadas en la mecánica de la ATM para poder diseñar prótesis en base a modelos fiables como en otras articulaciones en las que ya han resuelto el problema.Incapabability to develop effective inert systems to total temporomandibular joint substitution during decades has genered several biologic solutions for a biomecanic question. Autologous grafts don´t offer security in functioning, simmetry, or oclusal estability; its have more coplex technique and more potencial morbility. Alloplastic reconstruction guarantees oclusal stability, single and reproducible technique, predictable time in hospital, and low morbility with actual prosthetic systems. Patients whos prostheses is only one option are going to exist always, so that it is primordial measures of magnitude of implicated strenghts in TMJ mecanic to can design prosthesis based on reliable models like others articulations which have just resolved the question.

General surface reconstruction for cone-beam multislice spiral computed tomography

International Nuclear Information System (INIS)

Chen Laigao; Liang Yun; Heuscher, Dominic J.

2003-01-01

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

An efficient reconstruction algorithm for differential phase-contrast tomographic images from a limited number of views

International Nuclear Information System (INIS)

Sunaguchi, Naoki; Yuasa, Tetsuya; Gupta, Rajiv; Ando, Masami

2015-01-01

The main focus of this paper is reconstruction of tomographic phase-contrast image from a set of projections. We propose an efficient reconstruction algorithm for differential phase-contrast computed tomography that can considerably reduce the number of projections required for reconstruction. The key result underlying this research is a projection theorem that states that the second derivative of the projection set is linearly related to the Laplacian of the tomographic image. The proposed algorithm first reconstructs the Laplacian image of the phase-shift distribution from the second-derivative of the projections using total variation regularization. The second step is to obtain the phase-shift distribution by solving a Poisson equation whose source is the Laplacian image previously reconstructed under the Dirichlet condition. We demonstrate the efficacy of this algorithm using both synthetically generated simulation data and projection data acquired experimentally at a synchrotron. The experimental phase data were acquired from a human coronary artery specimen using dark-field-imaging optics pioneered by our group. Our results demonstrate that the proposed algorithm can reduce the number of projections to approximately 33% as compared with the conventional filtered backprojection method, without any detrimental effect on the image quality

A Statistical Approach to Motion Compensated Cone Beam Reconstruction

DEFF Research Database (Denmark)

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

2010-01-01

number of projections to be adequate. Since the patients are breathing freely during a scan, the number of projections with similar respiration may be to low. In the following we use an iterative reconstruction combined with the simultaneous estimation of the motion field, to improve reconstruction...... in these situations. Using a simulated dataset we demonstrate that this combination outperforms the FDK but due to ill possessedness of the motion estimation it is only on par with the sole iterative method....

Reduction of artefacts due to missing projections using OSEM

International Nuclear Information System (INIS)

Hutton, B.F.; Kyme, A.; Choong, K.

2002-01-01

Full text: It is well recognised that missing or corrupted projections can result in artefacts. This occasionally occurs due to errors in data transfer from acquisition memory to disk. A possible approach for reducing these artefacts was investigated, Using ordered subsets expectation maximization (OSEM) the iterative reconstruction proceeds by progressively including additional projections until a single iteration is complete. Clinically useful results can be obtained using a small subset size in a single iteration. Stopping prior to the complete iteration so as to avoid inclusion of missing or corrupted data should provide a 'partial' reconstruction with minimal artefacts. To test this hypothesis projections were selectively removed from a complete data set (2, 4, 8, 12 adjacent projections) and reconstructions were performed using both filtered back projection (FBP) and OSEM. To maintain a constant number of sub-iterations in OSEM an equal number of duplicate projections were substituted for the missing projections. Both 180 and 360 degrees reconstructions with missing data were compared with reconstruction for the complete data using sum of absolute differences. Results indicate that missing data causes artefacts for both FBP and OSEM however the severity of artefacts is significantly reduced using OSEM. The effect of missing data is generally greater for 180 degrees acquisition. OSEM is recommended for minimising reconstruction artefacts due to missing projections. Copyright (2002) The Australian and New Zealand Society of Nuclear Medicine Inc

Fast parallel algorithm for CT image reconstruction.

Science.gov (United States)

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

2012-01-01

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

Tomographic ventricular reconstruction using multiple view first-pass radionuclide angiography

International Nuclear Information System (INIS)

Lacy, J.L.; Ball, M.E.; Verani, M.S.; Wiles, H.; Roberts, R.

1985-01-01

In first-pass radionuclide angiography (FPRA) images of both left and right ventricles are uncontaminated by adjacent structures. Thus, the problem of tomographic reconstruction is vastly simplified compared to equilibrium blood pool imaging in which all structures are imaged simultaneously. Tomographic reconstruction from a limited number of views may thus be possible. A simple filtered interpolative back-projection reconstruction technique was employed. In this technique interpolation was used between sectional distributions at successive angles. Interpolations yielding 9 and 13 back projection angles of 22.5 0 and 15 0 were evaluated. Ventricular borders were obtained in each back-projected tomographic slice by location of the intensity level which provided correct total ventricular volume. Cast cross sections were quantitatively well represented by these borders. This ventricular border definition algorithm forms the basis for applications of the technique in animals and humans

Fast Tomographic Reconstruction From Limited Data Using Artificial Neural Networks

NARCIS (Netherlands)

D.M. Pelt (Daniël); K.J. Batenburg (Joost)

2013-01-01

htmlabstractImage reconstruction from a small number of projections is a challenging problem in tomography. Advanced algorithms that incorporate prior knowledge can sometimes produce accurate reconstructions, but they typically require long computation times. Furthermore, the required prior

Spectrotemporal CT data acquisition and reconstruction at low dose

International Nuclear Information System (INIS)

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

2015-01-01

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

Residual motion compensation in ECG-gated interventional cardiac vasculature reconstruction

International Nuclear Information System (INIS)

Schwemmer, C; Müller, K; Hornegger, J; Rohkohl, C; Lauritsch, G

2013-01-01

Three-dimensional reconstruction of cardiac vasculature from angiographic C-arm CT (rotational angiography) data is a major challenge. Motion artefacts corrupt image quality, reducing usability for diagnosis and guidance. Many state-of-the-art approaches depend on retrospective ECG-gating of projection data for image reconstruction. A trade-off has to be made regarding the size of the ECG-gating window. A large temporal window is desirable to avoid undersampling. However, residual motion will occur in a large window, causing motion artefacts. We present an algorithm to correct for residual motion. Our approach is based on a deformable 2D–2D registration between the forward projection of an initial, ECG-gated reconstruction, and the original projection data. The approach is fully automatic and does not require any complex segmentation of vasculature, or landmarks. The estimated motion is compensated for during the backprojection step of a subsequent reconstruction. We evaluated the method using the publicly available CAVAREV platform and on six human clinical datasets. We found a better visibility of structure, reduced motion artefacts, and increased sharpness of the vessels in the compensated reconstructions compared to the initial reconstructions. At the time of writing, our algorithm outperforms the leading result of the CAVAREV ranking list. For the clinical datasets, we found an average reduction of motion artefacts by 13 ± 6%. Vessel sharpness was improved by 25 ± 12% on average. (paper)

The use of 3D contrast-enhanced CT reconstructions to project images of vascular rings and coarctation of the aorta.

Science.gov (United States)

Di Sessa, Thomas G; Di Sessa, Peter; Gregory, Bill; Vranicar, Mark

2009-01-01

Aortic arch and pulmonary artery anomalies make up a group of vascular structures that have complex three-dimensional (3D) shapes. Tortuosity as well as hypoplasia or atresia of segments of the aortic arch or pulmonary artery makes the conventional two-dimensional (2D) imaging difficult. Nine patients with native coarctation or recoarctation and 4 patients with a vascular ring had a CT scan as a part of their clinical evaluation. There were 7 males. The mean age was 11.7 years. (range 19 days to 29 years) The mean weight was 22.7 kg (range 3.3-139.0 kg). The dicom data from contrast CT scans were converted by the Amira software package into a 3D image. The areas of interest were selected. The images were then projected in 3D on a standard video monitor and could be rotated 360 degrees in any dimension. Adequate CT scans and 3D reconstructions were obtained in 12 of 13 patients. There were 85-1,044 slices obtained in the adequate studies. We could not reconstruct a 3D image from a patient's CT scan that had only 22 slices. The anatomy defined by 3D was compared to 2D CT imaging and confirmed by cardiac catheterization or direct visualization in the operating room in the 12 patients with adequate 3D reconstructions. In 5 of 12 patients, 3D reconstructions provided valuable spatial information not observed in the conventional 2D scans. We believe that 3D reconstruction of contrast-enhanced CT scans of these complex structures provides additional valuable information that is helpful in the decision-making process.

The impact of reconstruction method on the quantification of DaTSCAN images

Energy Technology Data Exchange (ETDEWEB)

Dickson, John C.; Erlandsson, Kjell; Hutton, Brian F. [UCLH NHS Foundation Trust and University College London, Institute of Nuclear Medicine, London (United Kingdom); Tossici-Bolt, Livia [Southampton University Hospitals NHS Trust, Department of Medical Physics, Southampton (United Kingdom); Sera, Terez [University of Szeged, Department of Nuclear Medicine and Euromedic Szeged, Szeged (Hungary); Varrone, Andrea [Psychiatry Section and Stockholm Brain Institute, Karolinska Institute, Department of Clinical Neuroscience, Stockholm (Sweden); Tatsch, Klaus [EANM/European Network of Excellence for Brain Imaging, Vienna (Austria)

2010-01-15

Reconstruction of DaTSCAN brain studies using OS-EM iterative reconstruction offers better image quality and more accurate quantification than filtered back-projection. However, reconstruction must proceed for a sufficient number of iterations to achieve stable and accurate data. This study assessed the impact of the number of iterations on the image quantification, comparing the results of the iterative reconstruction with filtered back-projection data. A striatal phantom filled with {sup 123}I using striatal to background ratios between 2:1 and 10:1 was imaged on five different gamma camera systems. Data from each system were reconstructed using OS-EM (which included depth-independent resolution recovery) with various combinations of iterations and subsets to achieve up to 200 EM-equivalent iterations and with filtered back-projection. Using volume of interest analysis, the relationships between image reconstruction strategy and quantification of striatal uptake were assessed. For phantom filling ratios of 5:1 or less, significant convergence of measured ratios occurred close to 100 EM-equivalent iterations, whereas for higher filling ratios, measured uptake ratios did not display a convergence pattern. Assessment of the count concentrations used to derive the measured uptake ratio showed that nonconvergence of low background count concentrations caused peaking in higher measured uptake ratios. Compared to filtered back-projection, OS-EM displayed larger uptake ratios because of the resolution recovery applied in the iterative algorithm. The number of EM-equivalent iterations used in OS-EM reconstruction influences the quantification of DaTSCAN studies because of incomplete convergence and possible bias in areas of low activity due to the nonnegativity constraint in OS-EM reconstruction. Nevertheless, OS-EM using 100 EM-equivalent iterations provides the best linear discriminatory measure to quantify the uptake in DaTSCAN studies. (orig.)

Evaluation of reconstruction algorithms in SPECT neuroimaging: Pt. 1

International Nuclear Information System (INIS)

Heejoung Kim; Zeeberg, B.R.; Reba, R.C.

1993-01-01

In the presence of statistical noise, an iterative reconstruction algorithm (IRA) for the quantitative reconstruction of single-photon-emission computed tomographic (SPECT) brain images overcomes major limitations of applying the standard filtered back projection (FBP) reconstruction algorithm to projection data which have been degraded by convolution of the true radioactivity distribution with a finite-resolution distance-dependent detector response: (a) the non-uniformity within the grey (or white) matter voxels which results even though the true model is uniform within these voxels; (b) a significantly lower ratio of grey/white matter voxel values than in the true model; and (c) an inability to detect an altered radioactivity value within the grey (or white) matter voxels. It is normally expected that an algorithm which improves spatial resolution and quantitative accuracy might also increase the magnitude of the statistical noise in the reconstructed image. However, the noise properties in the IRA images are very similar to those in the FBP images. (Author)

Quantitative reconstruction from a single diffraction-enhanced image

International Nuclear Information System (INIS)

Paganin, D.M.; Lewis, R.A.; Kitchen, M.

2003-01-01

Full text: We develop an algorithm for using a single diffraction-enhanced image (DEI) to obtain a quantitative reconstruction of the projected thickness of a single-material sample which is embedded within a substrate of approximately constant thickness. This algorithm is used to quantitatively map inclusions in a breast phantom, from a single synchrotron DEI image. In particular, the reconstructed images quantitatively represent the projected thickness in the bulk of the sample, in contrast to DEI images which greatly emphasise sharp edges (high spatial frequencies). In the context of an ultimate aim of improved methods for breast cancer detection, the reconstructions are potentially of greater diagnostic value compared to the DEI data. Lastly, we point out that the methods of analysis presented here are also applicable to the quantitative analysis of differential interference contrast (DIC) images

Las tendencias de la moda prêt-à-porter de lujo en publicidad

OpenAIRE

Fàbregas Bulló, Carla

2017-01-01

Les marques de prêt-à-porter de luxe, són referents en la ment de molts consumidors a nivell global. En aquest projecte es pretén investigar sobre les mateixes així com en els àmbits en els quals repercuteix com són: les tendències, la publicitat, les revistes femenines... Els països en els quals se centra aquest projecte són França i Itàlia i s'han escollit cinc marques com a objecte d'estudi per país. Las marcas de prêt-à-porter de lujo, son referentes en la mente de muchos consumidores ...

Simulation and track reconstruction for beam telescopes

CERN Document Server

Maqbool, Salman

2017-01-01

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

Evaluation of proxy-based millennial reconstruction methods

Energy Technology Data Exchange (ETDEWEB)

Lee, Terry C.K.; Tsao, Min [University of Victoria, Department of Mathematics and Statistics, Victoria, BC (Canada); Zwiers, Francis W. [Environment Canada, Climate Research Division, Toronto, ON (Canada)

2008-08-15

A range of existing statistical approaches for reconstructing historical temperature variations from proxy data are compared using both climate model data and real-world paleoclimate proxy data. We also propose a new method for reconstruction that is based on a state-space time series model and Kalman filter algorithm. The state-space modelling approach and the recently developed RegEM method generally perform better than their competitors when reconstructing interannual variations in Northern Hemispheric mean surface air temperature. On the other hand, a variety of methods are seen to perform well when reconstructing surface air temperature variability on decadal time scales. An advantage of the new method is that it can incorporate additional, non-temperature, information into the reconstruction, such as the estimated response to external forcing, thereby permitting a simultaneous reconstruction and detection analysis as well as future projection. An application of these extensions is also demonstrated in the paper. (orig.)

Simulation and Track Reconstruction for Beam Telescopes

CERN Document Server

Maqbool, Salman

2017-01-01

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

Reconstruction of a uniform star object from interior x-ray data: uniqueness, stability and algorithm

International Nuclear Information System (INIS)

Van Gompel, Gert; Batenburg, K Joost; Defrise, Michel

2009-01-01

In this paper we consider the problem of reconstructing a two-dimensional star-shaped object of uniform density from truncated projections of the object. In particular, we prove that such an object is uniquely determined by its parallel projections sampled over a full π angular range with a detector that only covers an interior field-of-view, even if the density of the object is not known a priori. We analyze the stability of this reconstruction problem and propose a reconstruction algorithm. Simulation experiments demonstrate that the algorithm is capable of reconstructing a star-shaped object from interior data, even if the interior region is much smaller than the size of the object. In addition, we present results for a heuristic reconstruction algorithm called DART, that was recently proposed. The heuristic method is shown to yield accurate reconstructions if the density is known in advance, and to have a very good stability in the presence of noisy projection data. Finally, the performance of the DBP and DART algorithms is illustrated for the reconstruction of real micro-CT data of a diamond

Tensor-based dictionary learning for dynamic tomographic reconstruction

International Nuclear Information System (INIS)

Tan, Shengqi; Wu, Zhifang; Zhang, Yanbo; Mou, Xuanqin; Wang, Ge; Cao, Guohua; Yu, Hengyong

2015-01-01

In dynamic computed tomography (CT) reconstruction, the data acquisition speed limits the spatio-temporal resolution. Recently, compressed sensing theory has been instrumental in improving CT reconstruction from far few-view projections. In this paper, we present an adaptive method to train a tensor-based spatio-temporal dictionary for sparse representation of an image sequence during the reconstruction process. The correlations among atoms and across phases are considered to capture the characteristics of an object. The reconstruction problem is solved by the alternating direction method of multipliers. To recover fine or sharp structures such as edges, the nonlocal total variation is incorporated into the algorithmic framework. Preclinical examples including a sheep lung perfusion study and a dynamic mouse cardiac imaging demonstrate that the proposed approach outperforms the vectorized dictionary-based CT reconstruction in the case of few-view reconstruction. (paper)

Tensor-based Dictionary Learning for Dynamic Tomographic Reconstruction

Science.gov (United States)

Tan, Shengqi; Zhang, Yanbo; Wang, Ge; Mou, Xuanqin; Cao, Guohua; Wu, Zhifang; Yu, Hengyong

2015-01-01

In dynamic computed tomography (CT) reconstruction, the data acquisition speed limits the spatio-temporal resolution. Recently, compressed sensing theory has been instrumental in improving CT reconstruction from far few-view projections. In this paper, we present an adaptive method to train a tensor-based spatio-temporal dictionary for sparse representation of an image sequence during the reconstruction process. The correlations among atoms and across phases are considered to capture the characteristics of an object. The reconstruction problem is solved by the alternating direction method of multipliers. To recover fine or sharp structures such as edges, the nonlocal total variation is incorporated into the algorithmic framework. Preclinical examples including a sheep lung perfusion study and a dynamic mouse cardiac imaging demonstrate that the proposed approach outperforms the vectorized dictionary-based CT reconstruction in the case of few-view reconstruction. PMID:25779991

Isothermal sections of the state diagram for the Pr-Ni-Ge system at 870 (0-0,5Pr) and 670 K (0,5-1Pr)

International Nuclear Information System (INIS)

Fedyna, M.F.; Pecharskij, V.K.; Bodak, O.I.

1987-01-01

Method of X-ray phase and microstructural analyses were used to study Pr-Ni-Ge ternary system at 870K (0-0.50 at.fractions of Pr) and 670K (0.50-1.00 at.fractions of Pr). 11 ternary compounds exist in the system: Pr 1-x (NiGe) 13 (x=0.24), PrNi 2 Ge 2 , Pr 2 Ni 3 Ge 5 , PrNiGe 3 , Pr 2 NiGe 6 , Pr 3 Ni 4 Ge 4 , PrNi (1-x) Ge 2 (x=0.33), PrNiGe, Pr(NiGe) 2-x (x=0.14), Pr 3 NiGe 2 , ∼Pr 5 NiGe 4 . Crystal structure was determined for seven ternary compounds

Talking About The Smokes: a large-scale, community-based participatory research project.

Science.gov (United States)

Couzos, Sophia; Nicholson, Anna K; Hunt, Jennifer M; Davey, Maureen E; May, Josephine K; Bennet, Pele T; Westphal, Darren W; Thomas, David P

2015-06-01

To describe the Talking About The Smokes (TATS) project according to the World Health Organization guiding principles for conducting community-based participatory research (PR) involving indigenous peoples, to assist others planning large-scale PR projects. The TATS project was initiated in Australia in 2010 as part of the International Tobacco Control Policy Evaluation Project, and surveyed a representative sample of 2522 Aboriginal and Torres Strait Islander adults to assess the impact of tobacco control policies. The PR process of the TATS project, which aimed to build partnerships to create equitable conditions for knowledge production, was mapped and summarised onto a framework adapted from the WHO principles. Processes describing consultation and approval, partnerships and research agreements, communication, funding, ethics and consent, data and benefits of the research. The TATS project involved baseline and follow-up surveys conducted in 34 Aboriginal community-controlled health services and one Torres Strait community. Consistent with the WHO PR principles, the TATS project built on community priorities and strengths through strategic partnerships from project inception, and demonstrated the value of research agreements and trusting relationships to foster shared decision making, capacity building and a commitment to Indigenous data ownership. Community-based PR methodology, by definition, needs adaptation to local settings and priorities. The TATS project demonstrates that large-scale research can be participatory, with strong Indigenous community engagement and benefits.

AOF LTAO mode: reconstruction strategy and first test results

Science.gov (United States)

Oberti, Sylvain; Kolb, Johann; Le Louarn, Miska; La Penna, Paolo; Madec, Pierre-Yves; Neichel, Benoit; Sauvage, Jean-François; Fusco, Thierry; Donaldson, Robert; Soenke, Christian; Suárez Valles, Marcos; Arsenault, Robin

2016-07-01

GALACSI is the Adaptive Optics (AO) system serving the instrument MUSE in the framework of the Adaptive Optics Facility (AOF) project. Its Narrow Field Mode (NFM) is a Laser Tomography AO (LTAO) mode delivering high resolution in the visible across a small Field of View (FoV) of 7.5" diameter around the optical axis. From a reconstruction standpoint, GALACSI NFM intends to optimize the correction on axis by estimating the turbulence in volume via a tomographic process, then projecting the turbulence profile onto one single Deformable Mirror (DM) located in the pupil, close to the ground. In this paper, the laser tomographic reconstruction process is described. Several methods (virtual DM, virtual layer projection) are studied, under the constraint of a single matrix vector multiplication. The pseudo-synthetic interaction matrix model and the LTAO reconstructor design are analysed. Moreover, the reconstruction parameter space is explored, in particular the regularization terms. Furthermore, we present here the strategy to define the modal control basis and split the reconstruction between the Low Order (LO) loop and the High Order (HO) loop. Finally, closed loop performance obtained with a 3D turbulence generator will be analysed with respect to the most relevant system parameters to be tuned.

European bank for reconstruction and development

Directory of Open Access Journals (Sweden)

Kastratović Radovan

2015-01-01

Full Text Available European Bank for Reconstruction and Development - EBRD was established in the year 1991 and commenced operations in 1991. The objective of the Bank was to instigate market oriented approach to business in the countries of Central and Eastern Europe. This comprises support offered to structural reforms, privatisation, and development of entrepreneurship and legal system through financing of project conducive to the achievement of the aimed targets. The Bank approves loans both to the nation states and to the private sector. European Bank for Reconstruction and Development often appears in the role of investor. In addition, the Bank has also its consultative function. Owners of the European Bank for Reconstruction and Development are the developed countries and those that participate in the distribution of the Bank's profit. The Bank invests in the countries of Central, Eastern and South-East Europe, but also in those of Central Asia and Southern Mediterranean. The importance that the European Bank for Reconstruction and Development has for our country is best illustrated by the fact that this Bank is our largest institutional investor, with investments exceeding 3.5 billion EUR. This work begins with presentation of general information on the work of the European Bank for Reconstruction and Development, its objectives, activities, background history, ownership and organisational structure. It proceeds by giving relevant data on the Bank's business operations - the manner of project financing, the Bank's funds distribution per geographic criteria and activities, and the operative and financial results of the Bank's business activities. Brief description is also offered of the cooperation that the European Bank has with other international financial institutions. Finally, data is given bearing witness on the importance that the European Bank for Reconstruction and Development has for Serbia.

Improving head and neck CTA with hybrid and model-based iterative reconstruction techniques

NARCIS (Netherlands)

Niesten, J. M.; van der Schaaf, I. C.; Vos, P. C.; Willemink, MJ; Velthuis, B. K.

2015-01-01

AIM: To compare image quality of head and neck computed tomography angiography (CTA) reconstructed with filtered back projection (FBP), hybrid iterative reconstruction (HIR) and model-based iterative reconstruction (MIR) algorithms. MATERIALS AND METHODS: The raw data of 34 studies were

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

International Nuclear Information System (INIS)

Wang, Jing; Gu, Xuejun

2013-01-01

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

Motion-map constrained image reconstruction (MCIR): Application to four-dimensional cone-beam computed tomography

Energy Technology Data Exchange (ETDEWEB)

Park, Justin C. [Center for Advanced Radiotherapy Technologies and Department of Radiation Medicine and Applied Sciences, University of California San Diego, La Jolla, California 92093 and Department of Electrical and Computer Engineering, University of California San Diego, La Jolla, California 92093 (United States); Kim, Jin Sung [Department of Radiation Oncology, Samsung Medical Center, Seoul 135-710 (Korea, Republic of); Park, Sung Ho [Department of Medical Physics, Asan Medical Center, College of Medicine, University of Ulsan, Seoul 138-736 (Korea, Republic of); Liu, Zhaowei [Department of Electrical and Computer Engineering, University of California San Diego, La Jolla, California 92093 (United States); Song, Bongyong; Song, William Y. [Center for Advanced Radiotherapy Technologies and Department of Radiation Medicine and Applied Sciences, University of California San Diego, La Jolla, California 92093 (United States)

2013-12-15

Purpose: Utilization of respiratory correlated four-dimensional cone-beam computed tomography (4DCBCT) has enabled verification of internal target motion and volume immediately prior to treatment. However, with current standard CBCT scan, 4DCBCT poses challenge for reconstruction due to the fact that multiple phase binning leads to insufficient number of projection data to reconstruct and thus cause streaking artifacts. The purpose of this study is to develop a novel 4DCBCT reconstruction algorithm framework called motion-map constrained image reconstruction (MCIR), that allows reconstruction of high quality and high phase resolution 4DCBCT images with no more than the imaging dose as well as projections used in a standard free breathing 3DCBCT (FB-3DCBCT) scan.Methods: The unknown 4DCBCT volume at each phase was mathematically modeled as a combination of FB-3DCBCT and phase-specific update vector which has an associated motion-map matrix. The motion-map matrix, which is the key innovation of the MCIR algorithm, was defined as the matrix that distinguishes voxels that are moving from stationary ones. This 4DCBCT model was then reconstructed with compressed sensing (CS) reconstruction framework such that the voxels with high motion would be aggressively updated by the phase-wise sorted projections and the voxels with less motion would be minimally updated to preserve the FB-3DCBCT. To evaluate the performance of our proposed MCIR algorithm, we evaluated both numerical phantoms and a lung cancer patient. The results were then compared with the (1) clinical FB-3DCBCT reconstructed using the FDK, (2) 4DCBCT reconstructed using the FDK, and (3) 4DCBCT reconstructed using the well-known prior image constrained compressed sensing (PICCS).Results: Examination of the MCIR algorithm showed that high phase-resolved 4DCBCT with sets of up to 20 phases using a typical FB-3DCBCT scan could be reconstructed without compromising the image quality. Moreover, in comparison with

Motion-map constrained image reconstruction (MCIR): Application to four-dimensional cone-beam computed tomography

International Nuclear Information System (INIS)

Park, Justin C.; Kim, Jin Sung; Park, Sung Ho; Liu, Zhaowei; Song, Bongyong; Song, William Y.

2013-01-01

Purpose: Utilization of respiratory correlated four-dimensional cone-beam computed tomography (4DCBCT) has enabled verification of internal target motion and volume immediately prior to treatment. However, with current standard CBCT scan, 4DCBCT poses challenge for reconstruction due to the fact that multiple phase binning leads to insufficient number of projection data to reconstruct and thus cause streaking artifacts. The purpose of this study is to develop a novel 4DCBCT reconstruction algorithm framework called motion-map constrained image reconstruction (MCIR), that allows reconstruction of high quality and high phase resolution 4DCBCT images with no more than the imaging dose as well as projections used in a standard free breathing 3DCBCT (FB-3DCBCT) scan.Methods: The unknown 4DCBCT volume at each phase was mathematically modeled as a combination of FB-3DCBCT and phase-specific update vector which has an associated motion-map matrix. The motion-map matrix, which is the key innovation of the MCIR algorithm, was defined as the matrix that distinguishes voxels that are moving from stationary ones. This 4DCBCT model was then reconstructed with compressed sensing (CS) reconstruction framework such that the voxels with high motion would be aggressively updated by the phase-wise sorted projections and the voxels with less motion would be minimally updated to preserve the FB-3DCBCT. To evaluate the performance of our proposed MCIR algorithm, we evaluated both numerical phantoms and a lung cancer patient. The results were then compared with the (1) clinical FB-3DCBCT reconstructed using the FDK, (2) 4DCBCT reconstructed using the FDK, and (3) 4DCBCT reconstructed using the well-known prior image constrained compressed sensing (PICCS).Results: Examination of the MCIR algorithm showed that high phase-resolved 4DCBCT with sets of up to 20 phases using a typical FB-3DCBCT scan could be reconstructed without compromising the image quality. Moreover, in comparison with

Homotopic non-local regularized reconstruction from sparse positron emission tomography measurements

International Nuclear Information System (INIS)

Wong, Alexander; Liu, Chenyi; Wang, Xiao Yu; Fieguth, Paul; Bie, Hongxia

2015-01-01

Positron emission tomography scanners collect measurements of a patient’s in vivo radiotracer distribution. The system detects pairs of gamma rays emitted indirectly by a positron-emitting radionuclide (tracer), which is introduced into the body on a biologically active molecule, and the tomograms must be reconstructed from projections. The reconstruction of tomograms from the acquired PET data is an inverse problem that requires regularization. The use of tightly packed discrete detector rings, although improves signal-to-noise ratio, are often associated with high costs of positron emission tomography systems. Thus a sparse reconstruction, which would be capable of overcoming the noise effect while allowing for a reduced number of detectors, would have a great deal to offer. In this study, we introduce and investigate the potential of a homotopic non-local regularization reconstruction framework for effectively reconstructing positron emission tomograms from such sparse measurements. Results obtained using the proposed approach are compared with traditional filtered back-projection as well as expectation maximization reconstruction with total variation regularization. A new reconstruction method was developed for the purpose of improving the quality of positron emission tomography reconstruction from sparse measurements. We illustrate that promising reconstruction performance can be achieved for the proposed approach even at low sampling fractions, which allows for the use of significantly fewer detectors and have the potential to reduce scanner costs

Analysis of stability of tomographic reconstruction of x-ray medical images

Directory of Open Access Journals (Sweden)

Л. А. Булавін

2017-09-01

Full Text Available Slice reconstruction in X-ray computed tomography is reduced to the solution of integral equations, or a system of algebraic equations in discrete case. It is considered to be an ill-posed problem due to the inconsistencies in the number of equations and variables and due to errors in the experimental data. Therefore, determination of the best method of the slice reconstruction is of great interest. Furthermore, all available methods give approximate results. The aim of this article was two-fold: i to compare two methods of image reconstruction, viz. inverse projection and variation, using the numerical experiment; ii to obtain the relationship between image accuracy and experimental error. It appeared that the image obtained by inverse projection is unstable: there was no convergence of the approximate image to the accurate one, when the experimental error reached zero. In turn, the image obtained by variational method was accurate at zero experimental error. Finally, the latter showed better slice reconstruction, despite the low number of projections and the experimental errors.

Photoemission of heavy fermion superconductor PrOs4Sb12 and other Pr compounds

International Nuclear Information System (INIS)

Imada, S.; Yamasaki, A.; Sekiyama, A.; Settai, R.; Onuki, Y.; Suga, S.; Sugawara, H.; Sato, H.; Ochiai, A.

2004-01-01

Full text: Strongly correlated electronic states due to Pr 4f electrons found in several Pr compounds have recently been attracting much attention. The Pr 4f electrons are much more localized than in Ce due to the lanthanoid contraction. Therefore, the number of the Pr systems that show strong electron correlation is much smaller than Ce systems. We will present a comparative study of Pr 4f electronic states in such systems as the heavy fermion superconductor PrOs 4 Sb 12 , the Kondo system PrSn 3 and the localized 4f systems Pr 4 X 3 (X = Sb and Bi). The Pr 4f electronic state was probed by means of the Pr 3d → 4f resonant photoemission (RPES). Because the kinetic energy (E K ) of the photoelectrons is as high as ∼ 900 eV, this method is much more bulk sensitive than the 4d → 4f RPES with E K ∼ 100 eV. The energy resolution could be set to about 100 meV by utilizing the soft X-rays from BL25SU in SPring-8 and the SCIENTA SES-200 analyzer. The Pr 4f excitation spectrum of PrSn 3 was found to show a very strong intensity at the Fermi level (E F ). This can be interpreted as the Kondo resonance which has been observed in the Kondo Ce and Yb compounds. In the Pr 4f spectrum of the heavy fermion superconductor PrOs 4 Sb 12 , the intensity at E F was smaller than in PrSn 3 . This clearly shows that the Kondo temperature (T K ) is much lower in PrOs 4 Sb 12 than in PrSn 3 . We have further found a strong excitation energy dependence in the RPES line shape. In the case of Pr 4 X 3 (X = Sb and Bi), the intensity at E B was much smaller than PrSn 3 and PrOs 4 Sb 12 , which is consistent with the localized character of Pr 4f electrons in Pr 4 X 3 . The Pr 4f spectra of these localized systems are qualitatively well reproduced by a cluster model calculation that takes into account the hybridization between the Pr 4f orbital and the conduction and valence bands made up by the X p and Pr 5d states

PrEP implementation research in Africa: what is new?

Science.gov (United States)

Cowan, Frances M; Delany-Moretlwe, Sinead; Sanders, Eduard J; Mugo, Nelly R; Guedou, Fernand A; Alary, Michel; Behanzin, Luc; Mugurungi, Owen; Bekker, Linda-Gail

2016-01-01

Of the two million new HIV infections in adults in 2014, 70% occurred in sub-Saharan Africa. Several African countries have already approved guidelines for pre-exposure prophylaxis (PrEP) for individuals at substantial risk of HIV as part of combination HIV prevention but key questions remain about how to identify and deliver PrEP to those at greatest need. Throughout the continent, individuals in sero-discordant relationships, and members of key populations (sex workers, men who have sex with men (MSM), transgender women and injection drug users) are likely to benefit from the availability of PrEP. In addition, adolescent girls and young women (AGYW) are at substantial risk in some parts of the continent. It has been estimated that at least three million individuals in Africa are likely to be eligible for PrEP according to WHO's criteria. Tens of demonstration projects are planned or underway across the continent among a range of countries, populations and delivery settings. In each of the target populations, there are overarching issues related to (i) creating demand for PrEP, (ii) addressing supply-side issues and (iii) providing appropriate and tailored adherence support. Critical for creating demand for PrEP is the normalization of HIV prevention. Community-level interventions which engage opinion leaders as well as empowerment interventions for those at highest risk will be key. Critical to supply of PrEP is that services are accessible for all, including for stigmatized populations. Establishing accessible integrated services provides the opportunity to address other public health priorities including the unmet need for HIV testing, contraception and sexually transmitted infections treatment. National policies need to include minimum standards for training and quality assurance for PrEP implementation and to address supply chain issues. Adherence support needs to recognize that social and structural factors are likely to have an important influence

Reconstructing weak values without weak measurements

International Nuclear Information System (INIS)

Johansen, Lars M.

2007-01-01

I propose a scheme for reconstructing the weak value of an observable without the need for weak measurements. The post-selection in weak measurements is replaced by an initial projector measurement. The observable can be measured using any form of interaction, including projective measurements. The reconstruction is effected by measuring the change in the expectation value of the observable due to the projector measurement. The weak value may take nonclassical values if the projector measurement disturbs the expectation value of the observable

Iterative reconstruction reduces abdominal CT dose

International Nuclear Information System (INIS)

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

2012-01-01

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

Gestión de Costos en los Proyectos: un abordaje teórico desde las mejores prácticas del Project Management Institute

OpenAIRE

Oliveros Villegas, Miguel Ángel; Rincón de Parra, Haydeé

2011-01-01

La gestión de costos representa una de las áreas de conocimiento fundamentales en la gerencia de proyectos, la cual está compuesta por la estimación, el presupuesto y el control de los costos. Con el presente trabajo se tiene como propósito, previo un análisis bibliográfico, describir los procesos que integran la gestión de los costos en los proyectos desde la perspectiva de las mejores prácticas reconocidas por el Project Management Institute (traducido al español, Instituto d...

Evaluating low pass filters on SPECT reconstructed cardiac orientation estimation

Science.gov (United States)

Dwivedi, Shekhar

2009-02-01

Low pass filters can affect the quality of clinical SPECT images by smoothing. Appropriate filter and parameter selection leads to optimum smoothing that leads to a better quantification followed by correct diagnosis and accurate interpretation by the physician. This study aims at evaluating the low pass filters on SPECT reconstruction algorithms. Criteria for evaluating the filters are estimating the SPECT reconstructed cardiac azimuth and elevation angle. Low pass filters studied are butterworth, gaussian, hamming, hanning and parzen. Experiments are conducted using three reconstruction algorithms, FBP (filtered back projection), MLEM (maximum likelihood expectation maximization) and OSEM (ordered subsets expectation maximization), on four gated cardiac patient projections (two patients with stress and rest projections). Each filter is applied with varying cutoff and order for each reconstruction algorithm (only butterworth used for MLEM and OSEM). The azimuth and elevation angles are calculated from the reconstructed volume and the variation observed in the angles with varying filter parameters is reported. Our results demonstrate that behavior of hamming, hanning and parzen filter (used with FBP) with varying cutoff is similar for all the datasets. Butterworth filter (cutoff > 0.4) behaves in a similar fashion for all the datasets using all the algorithms whereas with OSEM for a cutoff < 0.4, it fails to generate cardiac orientation due to oversmoothing, and gives an unstable response with FBP and MLEM. This study on evaluating effect of low pass filter cutoff and order on cardiac orientation using three different reconstruction algorithms provides an interesting insight into optimal selection of filter parameters.

Tomographic Image Reconstruction Using Training Images with Matrix and Tensor Formulations

DEFF Research Database (Denmark)

Soltani, Sara

the image resolution compared to a classical reconstruction method such as Filtered Back Projection (FBP). Some priors for the tomographic reconstruction take the form of cross-section images of similar objects, providing a set of the so-called training images, that hold the key to the structural......Reducing X-ray exposure while maintaining the image quality is a major challenge in computed tomography (CT); since the imperfect data produced from the few view and/or low intensity projections results in low-quality images that are suffering from severe artifacts when using conventional...... information about the solution. The training images must be reliable and application-specific. This PhD project aims at providing a mathematical and computational framework for the use of training sets as non-parametric priors for the solution in tomographic image reconstruction. Through an unsupervised...

Suured prügifirmad valmistuvad prügipuuduseks / Mirko Ojakivi

Index Scriptorium Estoniae

Ojakivi, Mirko

2010-01-01

Ragn-Sells ja Adelan Prügiveod soovivad luba jäätmete pikaajaliseks vaheladestamiseks Tallinna piiril. Ragn-Sells saaks jäätmekütusetehase planeerimise ja ehitamise ajal endale koguda ligi 35 000 t segaolmejäätmeid aastas, Adelan Prügiveod sooviks ladestada ligi 50 000 t prügi aastas

Level-set reconstruction algorithm for ultrafast limited-angle X-ray computed tomography of two-phase flows.

Science.gov (United States)

Bieberle, M; Hampel, U

2015-06-13

Tomographic image reconstruction is based on recovering an object distribution from its projections, which have been acquired from all angular views around the object. If the angular range is limited to less than 180° of parallel projections, typical reconstruction artefacts arise when using standard algorithms. To compensate for this, specialized algorithms using a priori information about the object need to be applied. The application behind this work is ultrafast limited-angle X-ray computed tomography of two-phase flows. Here, only a binary distribution of the two phases needs to be reconstructed, which reduces the complexity of the inverse problem. To solve it, a new reconstruction algorithm (LSR) based on the level-set method is proposed. It includes one force function term accounting for matching the projection data and one incorporating a curvature-dependent smoothing of the phase boundary. The algorithm has been validated using simulated as well as measured projections of known structures, and its performance has been compared to the algebraic reconstruction technique and a binary derivative of it. The validation as well as the application of the level-set reconstruction on a dynamic two-phase flow demonstrated its applicability and its advantages over other reconstruction algorithms. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

PrEFiNe Plan: Strategic plan for Fabry's diseases in Nephrology

Directory of Open Access Journals (Sweden)

M.D. del Pino

2016-07-01

Discussion: PrEfiNE project will evaluate an action plan focused on improving FD knowledge to make necessary recommendations for an early recognition of the disease. In addition will generate a plan to improve previously undetected needs.

Multispectral x-ray CT: multivariate statistical analysis for efficient reconstruction

Science.gov (United States)

Kheirabadi, Mina; Mustafa, Wail; Lyksborg, Mark; Lund Olsen, Ulrik; Bjorholm Dahl, Anders

2017-10-01

Recent developments in multispectral X-ray detectors allow for an efficient identification of materials based on their chemical composition. This has a range of applications including security inspection, which is our motivation. In this paper, we analyze data from a tomographic setup employing the MultiX detector, that records projection data in 128 energy bins covering the range from 20 to 160 keV. Obtaining all information from this data requires reconstructing 128 tomograms, which is computationally expensive. Instead, we propose to reduce the dimensionality of projection data prior to reconstruction and reconstruct from the reduced data. We analyze three linear methods for dimensionality reduction using a dataset with 37 equally-spaced projection angles. Four bottles with different materials are recorded for which we are able to obtain similar discrimination of their content using a very reduced subset of tomograms compared to the 128 tomograms that would otherwise be needed without dimensionality reduction.

Crystal Field Levels of Pr3+ in PrFeO3 and PrGaO3 Determined by Inelastic Neutron Scattering

DEFF Research Database (Denmark)

Feldmann, K.; Henning, K.; Kaun, L.

1975-01-01

The crystal field splitting of the 3H4 ground state of the Pr ion in PrFeO3 and PrGaO3 has been investigated by inelastic scattering of thermal neutrons. At several temperatures the transitions have been measured by TAS and TOF methods for polycrystalline PrFeO3 and by the TOF method...... for polycrystalline PrGaO3. Energy level schemes which are different for these materials are given....

Analytically derived weighting factors for transmission tomography cone beam projections

International Nuclear Information System (INIS)

Yao Weiguang; Leszczynski, Konrad

2009-01-01

Weighting factors, which define the contributions of individual voxels of a 3D object to individual projection elements (pixels) on the detector, are the basic elements required in iterative tomographic reconstructions from transmission projections. Exact or as accurate as possible values for weighting factors are required in high-resolution reconstructions. Geometric complexity of the problem, however, makes it difficult to obtain exact weighting factor values. In this work, we derive an analytical expression for the weighting factors in cone beam projection geometry. The resulting formula is validated and applied to reconstruction from mega and kilovoltage x-ray cone beam projections. The reconstruction speed and accuracy are significantly improved by using the weighting factor values.

A three-dimensional reconstruction algorithm for an inverse-geometry volumetric CT system

International Nuclear Information System (INIS)

Schmidt, Taly Gilat; Fahrig, Rebecca; Pelc, Norbert J.

2005-01-01

An inverse-geometry volumetric computed tomography (IGCT) system has been proposed capable of rapidly acquiring sufficient data to reconstruct a thick volume in one circular scan. The system uses a large-area scanned source opposite a smaller detector. The source and detector have the same extent in the axial, or slice, direction, thus providing sufficient volumetric sampling and avoiding cone-beam artifacts. This paper describes a reconstruction algorithm for the IGCT system. The algorithm first rebins the acquired data into two-dimensional (2D) parallel-ray projections at multiple tilt and azimuthal angles, followed by a 3D filtered backprojection. The rebinning step is performed by gridding the data onto a Cartesian grid in a 4D projection space. We present a new method for correcting the gridding error caused by the finite and asymmetric sampling in the neighborhood of each output grid point in the projection space. The reconstruction algorithm was implemented and tested on simulated IGCT data. Results show that the gridding correction reduces the gridding errors to below one Hounsfield unit. With this correction, the reconstruction algorithm does not introduce significant artifacts or blurring when compared to images reconstructed from simulated 2D parallel-ray projections. We also present an investigation of the noise behavior of the method which verifies that the proposed reconstruction algorithm utilizes cross-plane rays as efficiently as in-plane rays and can provide noise comparable to an in-plane parallel-ray geometry for the same number of photons. Simulations of a resolution test pattern and the modulation transfer function demonstrate that the IGCT system, using the proposed algorithm, is capable of 0.4 mm isotropic resolution. The successful implementation of the reconstruction algorithm is an important step in establishing feasibility of the IGCT system

PrP N-terminal domain triggers PrPSc-like aggregation of Dpl

International Nuclear Information System (INIS)

Erlich, Paul; Cesbron, Jean-Yves; Lemaire-Vieille, Catherine; Curt, Aurelie; Andrieu, Jean-Pierre; Schoehn, Guy; Jamin, Marc; Gagnon, Jean

2008-01-01

Transmissible spongiform encephalopathies are fatal neurodegenerative disorders thought to be transmitted by self-perpetuating conformational conversion of a neuronal membrane glycoprotein (PrP C , for 'cellular prion protein') into an abnormal state (PrP Sc , for 'scrapie prion protein'). Doppel (Dpl) is a protein that shares significant biochemical and structural homology with PrP C . In contrast to its homologue PrP C , Dpl is unable to participate in prion disease progression or to achieve an abnormal PrP Sc -like state. We have constructed a chimeric mouse protein, composed of the N-terminal domain of PrP C (residues 23-125) and the C-terminal part of Dpl (residues 58-157). This chimeric protein displays PrP-like biochemical and structural features; when incubated in presence of NaCl, the α-helical monomer forms soluble β-sheet-rich oligomers which acquire partial resistance to pepsin proteolysis in vitro, as do PrP oligomers. Moreover, the presence of aggregates akin to protofibrils is observed in soluble oligomeric species by electron microscopy

Fully 3D GPU PET reconstruction

Energy Technology Data Exchange (ETDEWEB)

Herraiz, J.L., E-mail: joaquin@nuclear.fis.ucm.es [Grupo de Fisica Nuclear, Departmento Fisica Atomica, Molecular y Nuclear, Universidad Complutense de Madrid (Spain); Espana, S. [Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, MA (United States); Cal-Gonzalez, J. [Grupo de Fisica Nuclear, Departmento Fisica Atomica, Molecular y Nuclear, Universidad Complutense de Madrid (Spain); Vaquero, J.J. [Departmento de Bioingenieria e Ingenieria Espacial, Universidad Carlos III, Madrid (Spain); Desco, M. [Departmento de Bioingenieria e Ingenieria Espacial, Universidad Carlos III, Madrid (Spain); Unidad de Medicina y Cirugia Experimental, Hospital General Universitario Gregorio Maranon, Madrid (Spain); Udias, J.M. [Grupo de Fisica Nuclear, Departmento Fisica Atomica, Molecular y Nuclear, Universidad Complutense de Madrid (Spain)

2011-08-21

Fully 3D iterative tomographic image reconstruction is computationally very demanding. Graphics Processing Unit (GPU) has been proposed for many years as potential accelerators in complex scientific problems, but it has not been used until the recent advances in the programmability of GPUs that the best available reconstruction codes have started to be implemented to be run on GPUs. This work presents a GPU-based fully 3D PET iterative reconstruction software. This new code may reconstruct sinogram data from several commercially available PET scanners. The most important and time-consuming parts of the code, the forward and backward projection operations, are based on an accurate model of the scanner obtained with the Monte Carlo code PeneloPET and they have been massively parallelized on the GPU. For the PET scanners considered, the GPU-based code is more than 70 times faster than a similar code running on a single core of a fast CPU, obtaining in both cases the same images. The code has been designed to be easily adapted to reconstruct sinograms from any other PET scanner, including scanner prototypes.

Fully 3D GPU PET reconstruction

International Nuclear Information System (INIS)

Herraiz, J.L.; Espana, S.; Cal-Gonzalez, J.; Vaquero, J.J.; Desco, M.; Udias, J.M.

2011-01-01

Fully 3D iterative tomographic image reconstruction is computationally very demanding. Graphics Processing Unit (GPU) has been proposed for many years as potential accelerators in complex scientific problems, but it has not been used until the recent advances in the programmability of GPUs that the best available reconstruction codes have started to be implemented to be run on GPUs. This work presents a GPU-based fully 3D PET iterative reconstruction software. This new code may reconstruct sinogram data from several commercially available PET scanners. The most important and time-consuming parts of the code, the forward and backward projection operations, are based on an accurate model of the scanner obtained with the Monte Carlo code PeneloPET and they have been massively parallelized on the GPU. For the PET scanners considered, the GPU-based code is more than 70 times faster than a similar code running on a single core of a fast CPU, obtaining in both cases the same images. The code has been designed to be easily adapted to reconstruct sinograms from any other PET scanner, including scanner prototypes.

Projections onto Convex Sets Super-Resolution Reconstruction Based on Point Spread Function Estimation of Low-Resolution Remote Sensing Images

Directory of Open Access Journals (Sweden)

Chong Fan

2017-02-01

Full Text Available To solve the problem on inaccuracy when estimating the point spread function (PSF of the ideal original image in traditional projection onto convex set (POCS super-resolution (SR reconstruction, this paper presents an improved POCS SR algorithm based on PSF estimation of low-resolution (LR remote sensing images. The proposed algorithm can improve the spatial resolution of the image and benefit agricultural crop visual interpolation. The PSF of the highresolution (HR image is unknown in reality. Therefore, analysis of the relationship between the PSF of the HR image and the PSF of the LR image is important to estimate the PSF of the HR image by using multiple LR images. In this study, the linear relationship between the PSFs of the HR and LR images can be proven. In addition, the novel slant knife-edge method is employed, which can improve the accuracy of the PSF estimation of LR images. Finally, the proposed method is applied to reconstruct airborne digital sensor 40 (ADS40 three-line array images and the overlapped areas of two adjacent GF-2 images by embedding the estimated PSF of the HR image to the original POCS SR algorithm. Experimental results show that the proposed method yields higher quality of reconstructed images than that produced by the blind SR method and the bicubic interpolation method.

Accelerated 3D-OSEM image reconstruction using a Beowulf PC cluster for pinhole SPECT

International Nuclear Information System (INIS)

Zeniya, Tsutomu; Watabe, Hiroshi; Sohlberg, Antti; Iida, Hidehiro

2007-01-01

A conventional pinhole single-photon emission computed tomography (SPECT) with a single circular orbit has limitations associated with non-uniform spatial resolution or axial blurring. Recently, we demonstrated that three-dimensional (3D) images with uniform spatial resolution and no blurring can be obtained by complete data acquired using two-circular orbit, combined with the 3D ordered subsets expectation maximization (OSEM) reconstruction method. However, a long computation time is required to obtain the reconstruction image, because of the fact that 3D-OSEM is an iterative method and two-orbit acquisition doubles the size of the projection data. To reduce the long reconstruction time, we parallelized the two-orbit pinhole 3D-OSEM reconstruction process by using a Beowulf personal computer (PC) cluster. The Beowulf PC cluster consists of seven PCs connected to Gbit Ethernet switches. Message passing interface protocol was utilized for parallelizing the reconstruction process. The projection data in a subset are distributed to each PC. The partial image forward-and back-projected in each PC is transferred to all PCs. The current image estimate on each PC is updated after summing the partial images. The performance of parallelization on the PC cluster was evaluated using two independent projection data sets acquired by a pinhole SPECT system with two different circular orbits. Parallelization using the PC cluster improved the reconstruction time with increasing number of PCs. The reconstruction time of 54 min by the single PC was decreased to 10 min when six or seven PCs were used. The speed-up factor was 5.4. The reconstruction image by the PC cluster was virtually identical with that by the single PC. Parallelization of 3D-OSEM reconstruction for pinhole SPECT using the PC cluster can significantly reduce the computation time, whereas its implementation is simple and inexpensive. (author)

Bi3+–Pr3+ energy transfer processes and luminescent properties of LuAG:Bi,Pr and YAG:Bi,Pr single crystalline films

International Nuclear Information System (INIS)

Zorenko, Y.; Gorbenko, V.; Savchyn, V.; Zorenko, T.; Nikl, M.; Mares, J.A.; Beitlerova, A.; Jary, V.

2013-01-01

Absorption, cathodoluminescence, excitation spectra of photoluminescence (PL) and PL decay kinetics were studied at 300 K for the double doped with Bi 3+ –Pr 3+ and separately doped with Bi 3+ and Pr 3+ Lu 3 Al 5 O 12 (LuAG) and Y 3 Al 5 O 12 (YAG) single crystalline film (SCF) phosphors grown by the liquid phase epitaxy method. The emission bands in the UV range arising from the intrinsic radiative transitions of Bi 3+ based centers, and emission bands in the visible range, related to the luminescence of excitons localized around Bi 3+ based centers, were identified both in Bi–Pr and Bi-doped LuAG and YAG SCFs. The energy transfer processes from the host lattice simultaneously to Bi 3+ and Pr 3+ ions and from Bi 3+ to Pr 3+ ions were investigated. Competition between Pr 3+ and Bi 3+ ions in the energy transfer processes from the LuAG and YAG hosts was evidenced. The strong decrease of the intensity of Pr 3+ luminescence both in LuAG:Pr and YAG:Pr SCFs phosphors, grown from Bi 2 O 3 flux, is observed due to the quenching influence of Bi 3+ flux related impurity. Due to overlap of the UV emission band of Bi 3+ centers with the f–d absorption bands of Pr 3+ ions in the UV range and the luminescence of excitons localized around Bi ions with the f–f absorption bands of Pr 3+ ions in the visible range, an effective energy transfer from Bi 3+ ions to Pr 3+ ions takes place in LuAG:Bi,Pr and YAG:Bi,Pr SCFs, resulting in the appearance of slower component in the decay kinetics of the Pr 3+ d–f luminescence. -- Highlights: • Bi and Pr doped film phosphor grown by liquid phase epitaxy method. • Energy transfer from Bi 3+ to Pr 3+ ions. • Strong quenching of the Pr 3+ luminescence by Bi 3+ co-dopant

Geometric reconstruction methods for electron tomography

Energy Technology Data Exchange (ETDEWEB)

Alpers, Andreas, E-mail: alpers@ma.tum.de [Zentrum Mathematik, Technische Universität München, D-85747 Garching bei München (Germany); Gardner, Richard J., E-mail: Richard.Gardner@wwu.edu [Department of Mathematics, Western Washington University, Bellingham, WA 98225-9063 (United States); König, Stefan, E-mail: koenig@ma.tum.de [Zentrum Mathematik, Technische Universität München, D-85747 Garching bei München (Germany); Pennington, Robert S., E-mail: robert.pennington@uni-ulm.de [Center for Electron Nanoscopy, Technical University of Denmark, DK-2800 Kongens Lyngby (Denmark); Boothroyd, Chris B., E-mail: ChrisBoothroyd@cantab.net [Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons and Peter Grünberg Institute, Forschungszentrum Jülich, D-52425 Jülich (Germany); Houben, Lothar, E-mail: l.houben@fz-juelich.de [Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons and Peter Grünberg Institute, Forschungszentrum Jülich, D-52425 Jülich (Germany); Dunin-Borkowski, Rafal E., E-mail: rdb@fz-juelich.de [Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons and Peter Grünberg Institute, Forschungszentrum Jülich, D-52425 Jülich (Germany); Joost Batenburg, Kees, E-mail: Joost.Batenburg@cwi.nl [Centrum Wiskunde and Informatica, NL-1098XG, Amsterdam, The Netherlands and Vision Lab, Department of Physics, University of Antwerp, B-2610 Wilrijk (Belgium)

2013-05-15

Electron tomography is becoming an increasingly important tool in materials science for studying the three-dimensional morphologies and chemical compositions of nanostructures. The image quality obtained by many current algorithms is seriously affected by the problems of missing wedge artefacts and non-linear projection intensities due to diffraction effects. The former refers to the fact that data cannot be acquired over the full 180° tilt range; the latter implies that for some orientations, crystalline structures can show strong contrast changes. To overcome these problems we introduce and discuss several algorithms from the mathematical fields of geometric and discrete tomography. The algorithms incorporate geometric prior knowledge (mainly convexity and homogeneity), which also in principle considerably reduces the number of tilt angles required. Results are discussed for the reconstruction of an InAs nanowire. - Highlights: ► Four algorithms for electron tomography are introduced that utilize prior knowledge. ► Objects are assumed to be homogeneous; convexity and regularity is also discussed. ► We are able to reconstruct slices of a nanowire from as few as four projections. ► Algorithms should be selected based on the specific reconstruction task at hand.

Geometric reconstruction methods for electron tomography

International Nuclear Information System (INIS)

Alpers, Andreas; Gardner, Richard J.; König, Stefan; Pennington, Robert S.; Boothroyd, Chris B.; Houben, Lothar; Dunin-Borkowski, Rafal E.; Joost Batenburg, Kees

2013-01-01

Electron tomography is becoming an increasingly important tool in materials science for studying the three-dimensional morphologies and chemical compositions of nanostructures. The image quality obtained by many current algorithms is seriously affected by the problems of missing wedge artefacts and non-linear projection intensities due to diffraction effects. The former refers to the fact that data cannot be acquired over the full 180° tilt range; the latter implies that for some orientations, crystalline structures can show strong contrast changes. To overcome these problems we introduce and discuss several algorithms from the mathematical fields of geometric and discrete tomography. The algorithms incorporate geometric prior knowledge (mainly convexity and homogeneity), which also in principle considerably reduces the number of tilt angles required. Results are discussed for the reconstruction of an InAs nanowire. - Highlights: ► Four algorithms for electron tomography are introduced that utilize prior knowledge. ► Objects are assumed to be homogeneous; convexity and regularity is also discussed. ► We are able to reconstruct slices of a nanowire from as few as four projections. ► Algorithms should be selected based on the specific reconstruction task at hand

Optimal reconstruction angles

International Nuclear Information System (INIS)

Cook, G.O. Jr.; Knight, L.

1979-07-01

The question of optimal projection angles has recently become of interest in the field of reconstruction from projections. Here, studies are concentrated on the n x n pixel space, where literative algorithms such as ART and direct matrix techniques due to Katz are considered. The best angles are determined in a Gauss--Markov statistical sense as well as with respect to a function-theoretical error bound. The possibility of making photon intensity a function of angle is also examined. Finally, the best angles to use in an ART-like algorithm are studied. A certain set of unequally spaced angles was found to be preferred in several contexts. 15 figures, 6 tables

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

NARCIS (Netherlands)

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

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

Development of computed tomography system and image reconstruction algorithm

International Nuclear Information System (INIS)

Khairiah Yazid; Mohd Ashhar Khalid; Azaman Ahmad; Khairul Anuar Mohd Salleh; Ab Razak Hamzah

2006-01-01

Computed tomography is one of the most advanced and powerful nondestructive inspection techniques, which is currently used in many different industries. In several CT systems, detection has been by combination of an X-ray image intensifier and charge -coupled device (CCD) camera or by using line array detector. The recent development of X-ray flat panel detector has made fast CT imaging feasible and practical. Therefore this paper explained the arrangement of a new detection system which is using the existing high resolution (127 μm pixel size) flat panel detector in MINT and the image reconstruction technique developed. The aim of the project is to develop a prototype flat panel detector based CT imaging system for NDE. The prototype consisted of an X-ray tube, a flat panel detector system, a rotation table and a computer system to control the sample motion and image acquisition. Hence this project is divided to two major tasks, firstly to develop image reconstruction algorithm and secondly to integrate X-ray imaging components into one CT system. The image reconstruction algorithm using filtered back-projection method is developed and compared to other techniques. The MATLAB program is the tools used for the simulations and computations for this project. (Author)

Dynamic PET Image reconstruction for parametric imaging using the HYPR kernel method

Science.gov (United States)

Spencer, Benjamin; Qi, Jinyi; Badawi, Ramsey D.; Wang, Guobao

2017-03-01

Dynamic PET image reconstruction is a challenging problem because of the ill-conditioned nature of PET and the lowcounting statistics resulted from short time-frames in dynamic imaging. The kernel method for image reconstruction has been developed to improve image reconstruction of low-count PET data by incorporating prior information derived from high-count composite data. In contrast to most of the existing regularization-based methods, the kernel method embeds image prior information in the forward projection model and does not require an explicit regularization term in the reconstruction formula. Inspired by the existing highly constrained back-projection (HYPR) algorithm for dynamic PET image denoising, we propose in this work a new type of kernel that is simpler to implement and further improves the kernel-based dynamic PET image reconstruction. Our evaluation study using a physical phantom scan with synthetic FDG tracer kinetics has demonstrated that the new HYPR kernel-based reconstruction can achieve a better region-of-interest (ROI) bias versus standard deviation trade-off for dynamic PET parametric imaging than the post-reconstruction HYPR denoising method and the previously used nonlocal-means kernel.

Genome sequencing and annotation of multidrug resistant Mycobacterium tuberculosis (MDR-TB PR10 strain

Directory of Open Access Journals (Sweden)

Mohd Zakihalani A. Halim

2016-03-01

Full Text Available Here, we report the draft genome sequence and annotation of a multidrug resistant Mycobacterium tuberculosis strain PR10 (MDR-TB PR10 isolated from a patient diagnosed with tuberculosis. The size of the draft genome MDR-TB PR10 is 4.34 Mbp with 65.6% of G + C content and consists of 4637 predicted genes. The determinants were categorized by RAST into 400 subsystems with 4286 coding sequences and 50 RNAs. The whole genome shotgun project has been deposited at DDBJ/EMBL/GenBank under the accession number CP010968. Keywords: Mycobacterium tuberculosis, Genome, MDR, Extrapulmonary

Registration-based Reconstruction of Four-dimensional Cone Beam Computed Tomography

DEFF Research Database (Denmark)

Christoffersen, Christian; Hansen, David Christoffer; Poulsen, Per Rugaard

2013-01-01

We present a new method for reconstruction of four-dimensional (4D) cone beam computed tomography from an undersampled set of X-ray projections. The novelty of the proposed method lies in utilizing optical flow based registration to facilitate that each temporal phase is reconstructed from the full...

PR in the soсial protection institutions: a problem posing

Directory of Open Access Journals (Sweden)

V. V. Dudaryov

2015-02-01

Thus, effective PR, using communication capabilities of social advertising, will promote social programs and social services organizations, expand contacts with the public and similar organizations, fulfill social orders and projects successfully, implement public education, provide information on social issues, etc.

Dose fractionation theorem in 3-D reconstruction (tomography)

Energy Technology Data Exchange (ETDEWEB)

Glaeser, R.M. [Lawrence Berkeley National Lab., CA (United States)

1997-02-01

It is commonly assumed that the large number of projections for single-axis tomography precludes its application to most beam-labile specimens. However, Hegerl and Hoppe have pointed out that the total dose required to achieve statistical significance for each voxel of a computed 3-D reconstruction is the same as that required to obtain a single 2-D image of that isolated voxel, at the same level of statistical significance. Thus a statistically significant 3-D image can be computed from statistically insignificant projections, as along as the total dosage that is distributed among these projections is high enough that it would have resulted in a statistically significant projection, if applied to only one image. We have tested this critical theorem by simulating the tomographic reconstruction of a realistic 3-D model created from an electron micrograph. The simulations verify the basic conclusions of high absorption, signal-dependent noise, varying specimen contrast and missing angular range. Furthermore, the simulations demonstrate that individual projections in the series of fractionated-dose images can be aligned by cross-correlation because they contain significant information derived from the summation of features from different depths in the structure. This latter information is generally not useful for structural interpretation prior to 3-D reconstruction, owing to the complexity of most specimens investigated by single-axis tomography. These results, in combination with dose estimates for imaging single voxels and measurements of radiation damage in the electron microscope, demonstrate that it is feasible to use single-axis tomography with soft X-ray microscopy of frozen-hydrated specimens.

Dose fractionation theorem in 3-D reconstruction (tomography)

International Nuclear Information System (INIS)

Glaeser, R.M.

1997-01-01

It is commonly assumed that the large number of projections for single-axis tomography precludes its application to most beam-labile specimens. However, Hegerl and Hoppe have pointed out that the total dose required to achieve statistical significance for each voxel of a computed 3-D reconstruction is the same as that required to obtain a single 2-D image of that isolated voxel, at the same level of statistical significance. Thus a statistically significant 3-D image can be computed from statistically insignificant projections, as along as the total dosage that is distributed among these projections is high enough that it would have resulted in a statistically significant projection, if applied to only one image. We have tested this critical theorem by simulating the tomographic reconstruction of a realistic 3-D model created from an electron micrograph. The simulations verify the basic conclusions of high absorption, signal-dependent noise, varying specimen contrast and missing angular range. Furthermore, the simulations demonstrate that individual projections in the series of fractionated-dose images can be aligned by cross-correlation because they contain significant information derived from the summation of features from different depths in the structure. This latter information is generally not useful for structural interpretation prior to 3-D reconstruction, owing to the complexity of most specimens investigated by single-axis tomography. These results, in combination with dose estimates for imaging single voxels and measurements of radiation damage in the electron microscope, demonstrate that it is feasible to use single-axis tomography with soft X-ray microscopy of frozen-hydrated specimens

Analytical simulation platform describing projections in computed tomography systems

International Nuclear Information System (INIS)

Youn, Hanbean; Kim, Ho Kyung

2013-01-01

To reduce the patient dose, several approaches such as spectral imaging using photon counting detectors and statistical image reconstruction, are being considered. Although image-reconstruction algorithms may significantly enhance image quality in reconstructed images with low dose, true signal-to-noise properties are mainly determined by image quality in projections. We are developing an analytical simulation platform describing projections to investigate how quantum-interaction physics in each component configuring CT systems affect image quality in projections. This simulator will be very useful for an improved design or optimization of CT systems in economy as well as the development of novel image-reconstruction algorithms. In this study, we present the progress of development of the simulation platform with an emphasis on the theoretical framework describing the generation of projection data. We have prepared the analytical simulation platform describing projections in computed tomography systems. The remained further study before the meeting includes the following: Each stage in the cascaded signal-transfer model for obtaining projections will be validated by the Monte Carlo simulations. We will build up energy-dependent scatter and pixel-crosstalk kernels, and show their effects on image quality in projections and reconstructed images. We will investigate the effects of projections obtained from various imaging conditions and system (or detector) operation parameters on reconstructed images. It is challenging to include the interaction physics due to photon-counting detectors into the simulation platform. Detailed descriptions of the simulator will be presented with discussions on its performance and limitation as well as Monte Carlo validations. Computational cost will also be addressed in detail. The proposed method in this study is simple and can be used conveniently in lab environment

Interactive reconstruction in single-photon tomography

International Nuclear Information System (INIS)

Miller, T.R.; Wallis, J.W.; Wilson, A.D.

1989-01-01

A new method is described to allow interactive selection of the reconstruction filter at the time of interpretation of images from single-photon tomography. In the filtered back projection algorithm, the only part of the reconstruction process requiring user interaction is the selection of the window function. Since the ramp and window filters have different purposes, they can be separated, placing the window at the end of the reconstruction process as a three-dimensional filter. All stages of reconstruction except the window filtering are performed before the physician begins to interpret the study. The three-dimensional filtering is performed very rapidly with use of the Chebyshev convolution algorithm. A 64 x 64 x 64 pixel cube of data is filtered in 13-33 s using filters of 3-11 lengths. Smaller volumes of image data can be filtered in less than 1 s; thus, the user can interactively choose any desired filter for a given tomographic study at the time of interpretation of the images. (orig.)

IRVE-II Post-Flight Trajectory Reconstruction

Science.gov (United States)

O'Keefe, Stephen A.; Bose, David M.

2010-01-01

NASA s Inflatable Re-entry Vehicle Experiment (IRVE) II successfully demonstrated an inflatable aerodynamic decelerator after being launched aboard a sounding rocket from Wallops Flight Facility (WFF). Preliminary day of flight data compared well with pre-flight Monte Carlo analysis, and a more complete trajectory reconstruction performed with an Extended Kalman Filter (EKF) approach followed. The reconstructed trajectory and comparisons to an attitude solution provided by NASA Sounding Rocket Operations Contract (NSROC) personnel at WFF are presented. Additional comparisons are made between the reconstructed trajectory and pre and post-flight Monte Carlo trajectory predictions. Alternative observations of the trajectory are summarized which leverage flight accelerometer measurements, the pre-flight aerodynamic database, and on-board flight video. Finally, analysis of the payload separation and aeroshell deployment events are presented. The flight trajectory is reconstructed to fidelity sufficient to assess overall project objectives related to flight dynamics and overall, IRVE-II flight dynamics are in line with expectations

Microstructural Quantification, Property Prediction, and Stochastic Reconstruction of Heterogeneous Materials Using Limited X-Ray Tomography Data

Science.gov (United States)

Li, Hechao

An accurate knowledge of the complex microstructure of a heterogeneous material is crucial for quantitative structure-property relations establishment and its performance prediction and optimization. X-ray tomography has provided a non-destructive means for microstructure characterization in both 3D and 4D (i.e., structural evolution over time). Traditional reconstruction algorithms like filtered-back-projection (FBP) method or algebraic reconstruction techniques (ART) require huge number of tomographic projections and segmentation process before conducting microstructural quantification. This can be quite time consuming and computationally intensive. In this thesis, a novel procedure is first presented that allows one to directly extract key structural information in forms of spatial correlation functions from limited x-ray tomography data. The key component of the procedure is the computation of a "probability map", which provides the probability of an arbitrary point in the material system belonging to specific phase. The correlation functions of interest are then readily computed from the probability map. Using effective medium theory, accurate predictions of physical properties (e.g., elastic moduli) can be obtained. Secondly, a stochastic optimization procedure that enables one to accurately reconstruct material microstructure from a small number of x-ray tomographic projections (e.g., 20 - 40) is presented. Moreover, a stochastic procedure for multi-modal data fusion is proposed, where both X-ray projections and correlation functions computed from limited 2D optical images are fused to accurately reconstruct complex heterogeneous materials in 3D. This multi-modal reconstruction algorithm is proved to be able to integrate the complementary data to perform an excellent optimization procedure, which indicates its high efficiency in using limited structural information. Finally, the accuracy of the stochastic reconstruction procedure using limited X

SPECT data acquisition and image reconstruction in a stationary small animal SPECT/MRI system

Science.gov (United States)

Xu, Jingyan; Chen, Si; Yu, Jianhua; Meier, Dirk; Wagenaar, Douglas J.; Patt, Bradley E.; Tsui, Benjamin M. W.

2010-04-01

The goal of the study was to investigate data acquisition strategies and image reconstruction methods for a stationary SPECT insert that can operate inside an MRI scanner with a 12 cm bore diameter for simultaneous SPECT/MRI imaging of small animals. The SPECT insert consists of 3 octagonal rings of 8 MR-compatible CZT detectors per ring surrounding a multi-pinhole (MPH) collimator sleeve. Each pinhole is constructed to project the field-of-view (FOV) to one CZT detector. All 24 pinholes are focused to a cylindrical FOV of 25 mm in diameter and 34 mm in length. The data acquisition strategies we evaluated were optional collimator rotations to improve tomographic sampling; and the image reconstruction methods were iterative ML-EM with and without compensation for the geometric response function (GRF) of the MPH collimator. For this purpose, we developed an analytic simulator that calculates the system matrix with the GRF models of the MPH collimator. The simulator was used to generate projection data of a digital rod phantom with pinhole aperture sizes of 1 mm and 2 mm and with different collimator rotation patterns. Iterative ML-EM reconstruction with and without GRF compensation were used to reconstruct the projection data from the central ring of 8 detectors only, and from all 24 detectors. Our results indicated that without GRF compensation and at the default design of 24 projection views, the reconstructed images had significant artifacts. Accurate GRF compensation substantially improved the reconstructed image resolution and reduced image artifacts. With accurate GRF compensation, useful reconstructed images can be obtained using 24 projection views only. This last finding potentially enables dynamic SPECT (and/or MRI) studies in small animals, one of many possible application areas of the SPECT/MRI system. Further research efforts are warranted including experimentally measuring the system matrix for improved geometrical accuracy, incorporating the co

Assessment of phylogenetic sensitivity for reconstructing HIV-1 epidemiological relationships.

Science.gov (United States)

Beloukas, Apostolos; Magiorkinis, Emmanouil; Magiorkinis, Gkikas; Zavitsanou, Asimina; Karamitros, Timokratis; Hatzakis, Angelos; Paraskevis, Dimitrios

2012-06-01

Phylogenetic analysis has been extensively used as a tool for the reconstruction of epidemiological relations for research or for forensic purposes. It was our objective to assess the sensitivity of different phylogenetic methods and various phylogenetic programs to reconstruct epidemiological links among HIV-1 infected patients that is the probability to reveal a true transmission relationship. Multiple datasets (90) were prepared consisting of HIV-1 sequences in protease (PR) and partial reverse transcriptase (RT) sampled from patients with documented epidemiological relationship (target population), and from unrelated individuals (control population) belonging to the same HIV-1 subtype as the target population. Each dataset varied regarding the number, the geographic origin and the transmission risk groups of the sequences among the control population. Phylogenetic trees were inferred by neighbor-joining (NJ), maximum likelihood heuristics (hML) and Bayesian methods. All clusters of sequences belonging to the target population were correctly reconstructed by NJ and Bayesian methods receiving high bootstrap and posterior probability (PP) support, respectively. On the other hand, TreePuzzle failed to reconstruct or provide significant support for several clusters; high puzzling step support was associated with the inclusion of control sequences from the same geographic area as the target population. In contrary, all clusters were correctly reconstructed by hML as implemented in PhyML 3.0 receiving high bootstrap support. We report that under the conditions of our study, hML using PhyML, NJ and Bayesian methods were the most sensitive for the reconstruction of epidemiological links mostly from sexually infected individuals. Copyright © 2012 Elsevier B.V. All rights reserved.

Workflows and the Role of Images for Virtual 3d Reconstruction of no Longer Extant Historic Objects

Science.gov (United States)

Münster, S.

2013-07-01

3D reconstruction technologies have gained importance as tools for the research and visualization of no longer extant historic objects during the last decade. Within such reconstruction processes, visual media assumes several important roles: as the most important sources especially for a reconstruction of no longer extant objects, as a tool for communication and cooperation within the production process, as well as for a communication and visualization of results. While there are many discourses about theoretical issues of depiction as sources and as visualization outcomes of such projects, there is no systematic research about the importance of depiction during a 3D reconstruction process and based on empirical findings. Moreover, from a methodological perspective, it would be necessary to understand which role visual media plays during the production process and how it is affected by disciplinary boundaries and challenges specific to historic topics. Research includes an analysis of published work and case studies investigating reconstruction projects. This study uses methods taken from social sciences to gain a grounded view of how production processes would take place in practice and which functions and roles images would play within them. For the investigation of these topics, a content analysis of 452 conference proceedings and journal articles related to 3D reconstruction modeling in the field of humanities has been completed. Most of the projects described in those publications dealt with data acquisition and model building for existing objects. Only a small number of projects focused on structures that no longer or never existed physically. Especially that type of project seems to be interesting for a study of the importance of pictures as sources and as tools for interdisciplinary cooperation during the production process. In the course of the examination the authors of this paper applied a qualitative content analysis for a sample of 26 previously

Magni: A Python Package for Compressive Sampling and Reconstruction of Atomic Force Microscopy Images

DEFF Research Database (Denmark)

Oxvig, Christian Schou; Pedersen, Patrick Steffen; Arildsen, Thomas

2014-01-01

Magni is an open source Python package that embraces compressed sensing and Atomic Force Microscopy (AFM) imaging techniques. It provides AFM-specific functionality for undersampling and reconstructing images from AFM equipment and thereby accelerating the acquisition of AFM images. Magni also pr...... as a convenient platform for researchers in compressed sensing aiming at obtaining a high degree of reproducibility of their research....

High pre-exposure prophylaxis uptake and early adherence among men who have sex with men and transgender women at risk for HIV Infection: the PrEP Brasil demonstration project.

Science.gov (United States)

Hoagland, Brenda; Moreira, Ronaldo I; De Boni, Raquel B; Kallas, Esper G; Madruga, José Valdez; Vasconcelos, Ricardo; Goulart, Silvia; Torres, Thiago S; Marins, Luana M S; Anderson, Peter L; Luz, Paula M; Costa Leite, Iuri da; Liu, Albert Y; Veloso, Valdilea G; Grinsztejn, Beatriz

2017-04-06

The efficacy of pre-exposure prophylaxis (PrEP) in preventing sexual acquisition of human immunodeficiency virus (HIV) is well established. Little is known about the feasibility of PrEP implementation in middle-income settings with concentrated epidemics among men who have sex with men (MSM) and transgender women (TGW). PrEP Brasil is a prospective, multicentre, open-label demonstration project assessing PrEP delivery in the context of the Brazilian Public Health System. HIV-uninfected MSM and TGW in 3 referral centres in Rio de Janeiro and São Paulo were evaluated for eligibility and offered 48 weeks of daily emtricitabine/tenofovir for PrEP. Concentrations of tenofovir diphosphate in dried blood spot samples (DBS) at week 4 after enrolment (early adherence) were measured. Predictors of drug levels were assessed using ordinal logistic regression models considering the DBS drug level as a 3 level variable (<350 fmol/punch, ≥350-699 fmol/punch and ≥700 fmol/punch). 1,270 individuals were assessed for participation; n = 738 were potentially eligible and n = 450 were offered PrEP (PrEP uptake was 60.9%). Eligible but not enrolled individuals were younger, had lower HIV risk perception and had lower PrEP awareness. At week 4, 424 participants (of the 450 enrolled) had DBS TFV-DP concentrations, 94.1% in the protective range (≥350 fmol/punch, consistent with ≥2 pills per week), and 78% were in the highly protective range (≥700 fmol/punch, ≥4 pills per week). Participants with ≥12 years of schooling had 1.9 times the odds (95%CI 1.10-3.29) of a higher versus lower drug level than participants with <12 years of schooling. Condomless receptive anal intercourse in the prior 3 months was also associated with higher drug levels (adjusted OR = 1.78; 95% CI 1.08-2.94). The high uptake and early adherence indicate that PrEP for high-risk MSM and TGW can be successfully delivered in the context of the Brazilian Public Health System. Interventions to

Iterative reconstruction with boundary detection for carbon ion computed tomography

Science.gov (United States)

Shrestha, Deepak; Qin, Nan; Zhang, You; Kalantari, Faraz; Niu, Shanzhou; Jia, Xun; Pompos, Arnold; Jiang, Steve; Wang, Jing

2018-03-01

In heavy ion radiation therapy, improving the accuracy in range prediction of the ions inside the patient’s body has become essential. Accurate localization of the Bragg peak provides greater conformity of the tumor while sparing healthy tissues. We investigated the use of carbon ions directly for computed tomography (carbon CT) to create the relative stopping power map of a patient’s body. The Geant4 toolkit was used to perform a Monte Carlo simulation of the carbon ion trajectories, to study their lateral and angular deflections and the most likely paths, using a water phantom. Geant4 was used to create carbonCT projections of a contrast and spatial resolution phantom, with a cone beam of 430 MeV/u carbon ions. The contrast phantom consisted of cranial bone, lung material, and PMMA inserts while the spatial resolution phantom contained bone and lung material inserts with line pair (lp) densities ranging from 1.67 lp cm-1 through 5 lp cm-1. First, the positions of each carbon ion on the rear and front trackers were used for an approximate reconstruction of the phantom. The phantom boundary was extracted from this approximate reconstruction, by using the position as well as angle information from the four tracking detectors, resulting in the entry and exit locations of the individual ions on the phantom surface. Subsequent reconstruction was performed by the iterative algebraic reconstruction technique coupled with total variation minimization (ART-TV) assuming straight line trajectories for the ions inside the phantom. The influence of number of projections was studied with reconstruction from five different sets of projections: 15, 30, 45, 60 and 90. Additionally, the effect of number of ions on the image quality was investigated by reducing the number of ions/projection while keeping the total number of projections at 60. An estimation of carbon ion range using the carbonCT image resulted in improved range prediction compared to the range calculated using a

SU-E-I-45: Reconstruction of CT Images From Sparsely-Sampled Data Using the Logarithmic Barrier Method

International Nuclear Information System (INIS)

Xu, H

2014-01-01

Purpose: To develop and investigate whether the logarithmic barrier (LB) method can result in high-quality reconstructed CT images using sparsely-sampled noisy projection data Methods: The objective function is typically formulated as the sum of the total variation (TV) and a data fidelity (DF) term with a parameter λ that governs the relative weight between them. Finding the optimized value of λ is a critical step for this approach to give satisfactory results. The proposed LB method avoid using λ by constructing the objective function as the sum of the TV and a log function whose augment is the DF term. Newton's method was used to solve the optimization problem. The algorithm was coded in MatLab2013b. Both Shepp-Logan phantom and a patient lung CT image were used for demonstration of the algorithm. Measured data were simulated by calculating the projection data using radon transform. A Poisson noise model was used to account for the simulated detector noise. The iteration stopped when the difference of the current TV and the previous one was less than 1%. Results: Shepp-Logan phantom reconstruction study shows that filtered back-projection (FBP) gives high streak artifacts for 30 and 40 projections. Although visually the streak artifacts are less pronounced for 64 and 90 projections in FBP, the 1D pixel profiles indicate that FBP gives noisier reconstructed pixel values than LB does. A lung image reconstruction is presented. It shows that use of 64 projections gives satisfactory reconstructed image quality with regard to noise suppression and sharp edge preservation. Conclusion: This study demonstrates that the logarithmic barrier method can be used to reconstruct CT images from sparsely-amped data. The number of projections around 64 gives a balance between the over-smoothing of the sharp demarcation and noise suppression. Future study may extend to CBCT reconstruction and improvement on computation speed

Weighted expectation maximization reconstruction algorithms with application to gated megavoltage tomography

International Nuclear Information System (INIS)

Zhang Jin; Shi Daxin; Anastasio, Mark A; Sillanpaa, Jussi; Chang Jenghwa

2005-01-01

We propose and investigate weighted expectation maximization (EM) algorithms for image reconstruction in x-ray tomography. The development of the algorithms is motivated by the respiratory-gated megavoltage tomography problem, in which the acquired asymmetric cone-beam projections are limited in number and unevenly sampled over view angle. In these cases, images reconstructed by use of the conventional EM algorithm can contain ring- and streak-like artefacts that are attributable to a combination of data inconsistencies and truncation of the projection data. By use of computer-simulated and clinical gated fan-beam megavoltage projection data, we demonstrate that the proposed weighted EM algorithms effectively mitigate such image artefacts. (note)

Effect of noise in computed tomographic reconstructions on detectability

International Nuclear Information System (INIS)

Hanson, K.M.

1982-01-01

The detectability of features in an image is ultimately limited by the random fluctuations in density or noise present in that image. The noise in CT reconstructions arising from the statistical fluctuations in the one-dimensional input projection measurements has an unusual character owing to the reconstruction procedure. Such CT image noise differs from the white noise normally found in images in its lack of low-frequency components. The noise power spectrum of CT reconstructions can be related to the effective density of x-ray quanta detected in the projection measurements, designated as NEQ (noise-equivalent quanta). The detectability of objects that are somewhat larger than the spatial resolution is directly related to NEQ. Since contrast resolution may be defined in terms of the ability to detect large, low-contrast objects, the measurement of a CT scanner's NEQ may be used to characterize its contrast sensitivity

Literature and data review for the surface-water pathway: Columbia River and adjacent coastal areas. Hanford Environmental Dose Reconstruction Project

Energy Technology Data Exchange (ETDEWEB)

Walters, W.H.; Dirkes, R.L.; Napier, B.A.

1992-11-01

As part of the Hanford Environmental Dose Reconstruction (HEDR) Project, Battelle, Pacific Northwest Laboratories reviewed literature and data on radionuclide concentrations and distribution in the water, sediment, and biota of the Columbia River and adjacent coastal areas. Over 600 documents were reviewed including Hanford reports, reports by offsite agencies, journal articles, and graduate theses. Radionuclide concentration data were used in preliminary estimates of individual dose for the period 1964 through 1966. This report summarizes the literature and database reviews and the results of the preliminary dose estimates.

Knowledge-based iterative model reconstruction: comparative image quality and radiation dose with a pediatric computed tomography phantom

International Nuclear Information System (INIS)

Ryu, Young Jin; Choi, Young Hun; Cheon, Jung-Eun; Kim, Woo Sun; Kim, In-One; Ha, Seongmin

2016-01-01

CT of pediatric phantoms can provide useful guidance to the optimization of knowledge-based iterative reconstruction CT. To compare radiation dose and image quality of CT images obtained at different radiation doses reconstructed with knowledge-based iterative reconstruction, hybrid iterative reconstruction and filtered back-projection. We scanned a 5-year anthropomorphic phantom at seven levels of radiation. We then reconstructed CT data with knowledge-based iterative reconstruction (iterative model reconstruction [IMR] levels 1, 2 and 3; Philips Healthcare, Andover, MA), hybrid iterative reconstruction (iDose 4 , levels 3 and 7; Philips Healthcare, Andover, MA) and filtered back-projection. The noise, signal-to-noise ratio and contrast-to-noise ratio were calculated. We evaluated low-contrast resolutions and detectability by low-contrast targets and subjective and objective spatial resolutions by the line pairs and wire. With radiation at 100 peak kVp and 100 mAs (3.64 mSv), the relative doses ranged from 5% (0.19 mSv) to 150% (5.46 mSv). Lower noise and higher signal-to-noise, contrast-to-noise and objective spatial resolution were generally achieved in ascending order of filtered back-projection, iDose 4 levels 3 and 7, and IMR levels 1, 2 and 3, at all radiation dose levels. Compared with filtered back-projection at 100% dose, similar noise levels were obtained on IMR level 2 images at 24% dose and iDose 4 level 3 images at 50% dose, respectively. Regarding low-contrast resolution, low-contrast detectability and objective spatial resolution, IMR level 2 images at 24% dose showed comparable image quality with filtered back-projection at 100% dose. Subjective spatial resolution was not greatly affected by reconstruction algorithm. Reduced-dose IMR obtained at 0.92 mSv (24%) showed similar image quality to routine-dose filtered back-projection obtained at 3.64 mSv (100%), and half-dose iDose 4 obtained at 1.81 mSv. (orig.)

Knowledge-based iterative model reconstruction: comparative image quality and radiation dose with a pediatric computed tomography phantom.

Science.gov (United States)

Ryu, Young Jin; Choi, Young Hun; Cheon, Jung-Eun; Ha, Seongmin; Kim, Woo Sun; Kim, In-One

2016-03-01

CT of pediatric phantoms can provide useful guidance to the optimization of knowledge-based iterative reconstruction CT. To compare radiation dose and image quality of CT images obtained at different radiation doses reconstructed with knowledge-based iterative reconstruction, hybrid iterative reconstruction and filtered back-projection. We scanned a 5-year anthropomorphic phantom at seven levels of radiation. We then reconstructed CT data with knowledge-based iterative reconstruction (iterative model reconstruction [IMR] levels 1, 2 and 3; Philips Healthcare, Andover, MA), hybrid iterative reconstruction (iDose(4), levels 3 and 7; Philips Healthcare, Andover, MA) and filtered back-projection. The noise, signal-to-noise ratio and contrast-to-noise ratio were calculated. We evaluated low-contrast resolutions and detectability by low-contrast targets and subjective and objective spatial resolutions by the line pairs and wire. With radiation at 100 peak kVp and 100 mAs (3.64 mSv), the relative doses ranged from 5% (0.19 mSv) to 150% (5.46 mSv). Lower noise and higher signal-to-noise, contrast-to-noise and objective spatial resolution were generally achieved in ascending order of filtered back-projection, iDose(4) levels 3 and 7, and IMR levels 1, 2 and 3, at all radiation dose levels. Compared with filtered back-projection at 100% dose, similar noise levels were obtained on IMR level 2 images at 24% dose and iDose(4) level 3 images at 50% dose, respectively. Regarding low-contrast resolution, low-contrast detectability and objective spatial resolution, IMR level 2 images at 24% dose showed comparable image quality with filtered back-projection at 100% dose. Subjective spatial resolution was not greatly affected by reconstruction algorithm. Reduced-dose IMR obtained at 0.92 mSv (24%) showed similar image quality to routine-dose filtered back-projection obtained at 3.64 mSv (100%), and half-dose iDose(4) obtained at 1.81 mSv.

High spatial resolution CT image reconstruction using parallel computing

International Nuclear Information System (INIS)

Yin Yin; Liu Li; Sun Gongxing

2003-01-01

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

Interaction between Shadoo and PrP Affects the PrP-Folding Pathway.

Science.gov (United States)

Ciric, Danica; Richard, Charles-Adrien; Moudjou, Mohammed; Chapuis, Jérôme; Sibille, Pierre; Daude, Nathalie; Westaway, David; Adrover, Miguel; Béringue, Vincent; Martin, Davy; Rezaei, Human

2015-06-01

Prion diseases are characterized by conformational changes of a cellular prion protein (PrP(C)) into a β-sheet-enriched and aggregated conformer (PrP(Sc)). Shadoo (Sho), a member of the prion protein family, is expressed in the central nervous system (CNS) and is highly conserved among vertebrates. On the basis of histoanatomical colocalization and sequence similarities, it is suspected that Sho and PrP may be functionally related. The downregulation of Sho expression during prion pathology and the direct interaction between Sho and PrP, as revealed by two-hybrid analysis, suggest a relationship between Sho and prion replication. Using biochemical and biophysical approaches, we demonstrate that Sho forms a 1:1 complex with full-length PrP with a dissociation constant in the micromolar range, and this interaction consequently modifies the PrP-folding pathway. Using a truncated PrP that mimics the C-terminal C1 fragment, an allosteric binding behavior with a Hill number of 4 was observed, suggesting that at least a tetramerization state occurs. A cell-based prion titration assay performed with different concentrations of Sho revealed an increase in the PrP(Sc) conversion rate in the presence of Sho. Collectively, our observations suggest that Sho can affect the prion replication process by (i) acting as a holdase and (ii) interfering with the dominant-negative inhibitor effect of the C1 fragment. Since the inception of the prion theory, the search for a cofactor involved in the conversion process has been an active field of research. Although the PrP interactome presents a broad landscape, candidates corresponding to specific criteria for cofactors are currently missing. Here, we describe for the first time that Sho can affect PrP structural dynamics and therefore increase the prion conversion rate. A biochemical characterization of Sho-PrP indicates that Sho acts as an ATP-independent holdase. Copyright © 2015, American Society for Microbiology. All Rights

Recombinant PrPSc shares structural features with brain-derived PrPSc: Insights from limited proteolysis.

Science.gov (United States)

Sevillano, Alejandro M; Fernández-Borges, Natalia; Younas, Neelam; Wang, Fei; R Elezgarai, Saioa; Bravo, Susana; Vázquez-Fernández, Ester; Rosa, Isaac; Eraña, Hasier; Gil, David; Veiga, Sonia; Vidal, Enric; Erickson-Beltran, Melissa L; Guitián, Esteban; Silva, Christopher J; Nonno, Romolo; Ma, Jiyan; Castilla, Joaquín; R Requena, Jesús

2018-01-01

Very solid evidence suggests that the core of full length PrPSc is a 4-rung β-solenoid, and that individual PrPSc subunits stack to form amyloid fibers. We recently used limited proteolysis to map the β-strands and connecting loops that make up the PrPSc solenoid. Using high resolution SDS-PAGE followed by epitope analysis, and mass spectrometry, we identified positions ~116/118, 133-134, 141, 152-153, 162, 169 and 179 (murine numbering) as Proteinase K (PK) cleavage sites in PrPSc. Such sites likely define loops and/or borders of β-strands, helping us to predict the threading of the β-solenoid. We have now extended this approach to recombinant PrPSc (recPrPSc). The term recPrPSc refers to bona fide recombinant prions prepared by PMCA, exhibiting infectivity with attack rates of ~100%. Limited proteolysis of mouse and bank vole recPrPSc species yielded N-terminally truncated PK-resistant fragments similar to those seen in brain-derived PrPSc, albeit with varying relative yields. Along with these fragments, doubly N- and C-terminally truncated fragments, in particular ~89/97-152, were detected in some recPrPSc preparations; similar fragments are characteristic of atypical strains of brain-derived PrPSc. Our results suggest a shared architecture of recPrPSc and brain PrPSc prions. The observed differences, in particular the distinct yields of specific PK-resistant fragments, are likely due to differences in threading which result in the specific biochemical characteristics of recPrPSc. Furthermore, recombinant PrPSc offers exciting opportunities for structural studies unachievable with brain-derived PrPSc.

Pr-magnetism in the quasi-skutterudite compound PrFe2Al8.

Science.gov (United States)

Nair, Harikrishnan S; Ogunbunmi, Michael O; Kumar, C M N; Adroja, D T; Manuel, P; Fortes, D; Taylor, J; Strydom, A M

2017-08-31

The intermetallic compound PrFe 2 Al 8 that possesses a three-dimensional network structure of Al polyhedra centered at the transition metal element Fe and the rare earth Pr is investigated through neutron powder diffraction and inelastic neutron scattering in order to elucidate the magnetic ground state of Pr and Fe and the crystal field effects of Pr. Our neutron diffraction study confirms long-range magnetic order of Pr below [Formula: see text] K in this compound. Subsequent magnetic structure estimation reveals a magnetic propagation vector [Formula: see text] with a magnetic moment value of [Formula: see text]/Pr along the orthorhombic c-axis and evidence the lack of ordering in the Fe sublattice. The inelastic neutron scattering study reveals one crystalline electric field excitation near 19 meV at 5 K in PrFe 2 Al 8 . The energy-integrated intensity of the 19 meV excitation as a function of [Formula: see text] follows the square of the magnetic form factor of [Formula: see text] thereby confirming that the inelastic excitation belongs to the Pr sublattice. The second sum rule applied to the dynamic structure factor indicates only 1.6(2) [Formula: see text] evolving at the 19 meV peak compared to the 3.58 [Formula: see text] for free [Formula: see text], indicating that the crystal field ground state is magnetic and the missing moment is associated with the resolution limited quasi-elastic line. The magnetic order occurring in Pr in PrFe 2 Al 8 is counter-intuitive to the symmetry-allowed crystal field level scheme, hence, is suggestive of exchange-mediated mechanisms of ordering stemming from the magnetic ground state of the crystal field levels.

Comparison of iterative model, hybrid iterative, and filtered back projection reconstruction techniques in low-dose brain CT: impact of thin-slice imaging

Energy Technology Data Exchange (ETDEWEB)

Nakaura, Takeshi; Iyama, Yuji; Kidoh, Masafumi; Yokoyama, Koichi [Amakusa Medical Center, Diagnostic Radiology, Amakusa, Kumamoto (Japan); Kumamoto University, Department of Diagnostic Radiology, Graduate School of Medical Sciences, Kumamoto (Japan); Oda, Seitaro; Yamashita, Yasuyuki [Kumamoto University, Department of Diagnostic Radiology, Graduate School of Medical Sciences, Kumamoto (Japan); Tokuyasu, Shinichi [Philips Electronics, Kumamoto (Japan); Harada, Kazunori [Amakusa Medical Center, Department of Surgery, Kumamoto (Japan)

2016-03-15

The purpose of this study was to evaluate the utility of iterative model reconstruction (IMR) in brain CT especially with thin-slice images. This prospective study received institutional review board approval, and prior informed consent to participate was obtained from all patients. We enrolled 34 patients who underwent brain CT and reconstructed axial images with filtered back projection (FBP), hybrid iterative reconstruction (HIR) and IMR with 1 and 5 mm slice thicknesses. The CT number, image noise, contrast, and contrast noise ratio (CNR) between the thalamus and internal capsule, and the rate of increase of image noise in 1 and 5 mm thickness images between the reconstruction methods, were assessed. Two independent radiologists assessed image contrast, image noise, image sharpness, and overall image quality on a 4-point scale. The CNRs in 1 and 5 mm slice thickness were significantly higher with IMR (1.2 ± 0.6 and 2.2 ± 0.8, respectively) than with FBP (0.4 ± 0.3 and 1.0 ± 0.4, respectively) and HIR (0.5 ± 0.3 and 1.2 ± 0.4, respectively) (p < 0.01). The mean rate of increasing noise from 5 to 1 mm thickness images was significantly lower with IMR (1.7 ± 0.3) than with FBP (2.3 ± 0.3) and HIR (2.3 ± 0.4) (p < 0.01). There were no significant differences in qualitative analysis of unfamiliar image texture between the reconstruction techniques. IMR offers significant noise reduction and higher contrast and CNR in brain CT, especially for thin-slice images, when compared to FBP and HIR. (orig.)

Comparison of pure and hybrid iterative reconstruction techniques with conventional filtered back projection: Image quality assessment in the cervicothoracic region

Energy Technology Data Exchange (ETDEWEB)

Katsura, Masaki, E-mail: mkatsura-tky@umin.ac.jp [Department of Radiology, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655 (Japan); Sato, Jiro; Akahane, Masaaki; Matsuda, Izuru; Ishida, Masanori; Yasaka, Koichiro; Kunimatsu, Akira; Ohtomo, Kuni [Department of Radiology, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655 (Japan)

2013-02-15

Objectives: To evaluate the impact on image quality of three different image reconstruction techniques in the cervicothoracic region: model-based iterative reconstruction (MBIR), adaptive statistical iterative reconstruction (ASIR), and filtered back projection (FBP). Methods: Forty-four patients underwent unenhanced standard-of-care clinical computed tomography (CT) examinations which included the cervicothoracic region with a 64-row multidetector CT scanner. Images were reconstructed with FBP, 50% ASIR-FBP blending (ASIR50), and MBIR. Two radiologists assessed the cervicothoracic region in a blinded manner for streak artifacts, pixilated blotchy appearances, critical reproduction of visually sharp anatomical structures (thyroid gland, common carotid artery, and esophagus), and overall diagnostic acceptability. Objective image noise was measured in the internal jugular vein. Data were analyzed using the sign test and pair-wise Student's t-test. Results: MBIR images had significant lower quantitative image noise (8.88 ± 1.32) compared to ASIR images (18.63 ± 4.19, P < 0.01) and FBP images (26.52 ± 5.8, P < 0.01). Significant improvements in streak artifacts of the cervicothoracic region were observed with the use of MBIR (P < 0.001 each for MBIR vs. the other two image data sets for both readers), while no significant difference was observed between ASIR and FBP (P > 0.9 for ASIR vs. FBP for both readers). MBIR images were all diagnostically acceptable. Unique features of MBIR images included pixilated blotchy appearances, which did not adversely affect diagnostic acceptability. Conclusions: MBIR significantly improves image noise and streak artifacts of the cervicothoracic region over ASIR and FBP. MBIR is expected to enhance the value of CT examinations for areas where image noise and streak artifacts are problematic.

ELUCID—Exploring the Local Universe with the reConstructed Initial Density Field. II. Reconstruction Diagnostics, Applied to Numerical Halo Catalogs

Energy Technology Data Exchange (ETDEWEB)

Tweed, Dylan; Yang, Xiaohu; Li, Shijie; Jing, Y. P. [Center for Astronomy and Astrophysics, Shanghai Jiao Tong University, Shanghai 200240 (China); Wang, Huiyuan [Key Laboratory for Research in Galaxies and Cosmology, Department of Astronomy, University of Science and Technology of China, Hefei, Anhui 230026 (China); Cui, Weiguang [Departamento de Física Teórica, Módulo 15, Facultad de Ciencias, Universidad Autónoma de Madrid, E-28049 Madrid (Spain); Zhang, Youcai [Shanghai Astronomical Observatory, Nandan Road 80, Shanghai 200030 (China); Mo, H. J., E-mail: dtweed@sjtu.edu.cn [Department of Astronomy, University of Massachusetts, Amherst MA, 01003-9305 (United States)

2017-05-20

The ELUCID project aims to build a series of realistic cosmological simulations that reproduce the spatial and mass distributions of the galaxies as observed in the Sloan Digital Sky Survey. This requires powerful reconstruction techniques to create constrained initial conditions (ICs). We test the reconstruction method by applying it to several N -body simulations. We use two medium-resolution simulations, which each produced three additional constrained N -body simulations. We compare the resulting friend-of-friend catalogs by using the particle indexes as tracers, and quantify the quality of the reconstruction by varying the main smoothing parameter. The cross-identification method we use proves to be efficient, and the results suggest that the most massive reconstructed halos are effectively traced from the same Lagrangian regions in the ICs. A preliminary time-dependence analysis indicates that high-mass-end halos converge only at a redshift close to the reconstruction redshift. This suggests that, for earlier snapshots, only collections of progenitors may be effectively cross-identified.

The I-35W bridge Project Website

DEFF Research Database (Denmark)

Kampf, Constance

How can websites be used to rebuild trust?  In August 2007, the Interstate Highway 35-W bridge in Minneapolis, MN collapsed during rush hour.  Although many people were rescued and casualties were as limited as could be expected due to quick and effective intervention, the image of a major bridge...... collapsing during rush hour damaged the Minnesota Department of Transportation's reputation and resulted in the loss of public trust for the organization.  The ensuing bridge reconstruction project included a project website intended to rebuild this trust through transparency, community involvement......, and the use of multimodal features.  This paper looks at the I35-W bridge reconstruction project in Minneapolis through web-based communication by the Minnesota Department of Transportation (MnDOT) about the project. The MnDOT bridge reconstruction website will be examined using a combination of 1). Weick...

Dabarties rekonstrukcija Marguerite’os Yourcenar romane Hadriano memuarai | La reconstruction du present dans le roman de Marguerite Yourcenar Memoires d’Hadrien

Directory of Open Access Journals (Sweden)

Vytautas Bikulčius

2004-01-01

Full Text Available Dans cet article on analyse la reconstruction du présent dans le roman de Marguerite Yourcenar Mémoires d’Hadrien. La définition de cette oeuvre comme une biographie imaginaire est la plus courante. Entre le II siècle et XX siècle il existe une distance énorme, néanmoins M. Yourcenar a su trouver ce qui lie ces deux époques. Quoiqu’elle s’intéresse à l’empereur Hadrien et à son ambiance, de façon paradoxale elle reconstruit le présent où elle vit, c’est–à–dire, les années qui suivent la Seconde Guerre mondiale. Hadrien présente pour M. Yourcenar l’idéal d’un homme politique. Ses anticipations reflètent les réalités de l’après-guerre. Ainsi l’empereur entrevoit la possibilité des Nations Unies, de l’OTAN, le rôle du pape dans la politique mondiale, les idées de la globalisation. Hadrien n’est pas lié avec un homme de politique concret. Cette reconstruction du présent dans Mémoires d’Hadrien est assez importante, car elle modifie le genre de cette oeuvre d’une „autobiographie imaginaire“ en „autobiographie imaginaire intellectuelle“.

The maximum likelihood estimator method of image reconstruction: Its fundamental characteristics and their origin

International Nuclear Information System (INIS)

Llacer, J.; Veklerov, E.

1987-05-01

We review our recent work characterizing the image reconstruction properties of the MLE algorithm. We studied its convergence properties and confirmed the onset of image deterioration, which is a function of the number of counts in the source. By modulating the weight given to projection tubes with high numbers of counts with respect to those with low numbers of counts in the reconstruction process, we have confirmed that image deterioration is due to an attempt by the algorithm to match projection data tubes with high numbers of counts too closely to the iterative image projections. We developed a stopping rule for the algorithm that tests the hypothesis that a reconstructed image could have given the initial projection data in a manner consistent with the underlying assumption of Poisson distributed variables. The rule was applied to two mathematically generated phantoms with success and to a third phantom with exact (no statistical fluctuations) projection data. We conclude that the behavior of the target functions whose extrema are sought in iterative schemes is more important in the early stages of the reconstruction than in the later stages, when the extrema are being approached but with the Poisson nature of the measurement. 11 refs., 14 figs

Construction project management handbook : September 2009.

Science.gov (United States)

2009-09-01

The purpose of this Handbook is to provide guidelines for use by public transit agencies (Agencies) undertaking substantial construction : projects, either for the first time or with little prior experience with construction project management. It pr...

Towards an inline reconstruction architecture for micro-CT systems

International Nuclear Information System (INIS)

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

2005-01-01

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

Neutrino Event Reconstruction in a Liquid Argon TPC

Energy Technology Data Exchange (ETDEWEB)

Barker, Gary, E-mail: G.J.Barker@Warwick.ac.uk [Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL (United Kingdom)

2011-07-25

We present some preliminary findings and results from activities in Europe and the USA working towards an automated, algorithmic, reconstruction of particle interactions in liquid argon time projection chambers.

State diagram of Pr-Bi system

International Nuclear Information System (INIS)

Abulkhaev, V.L.; Ganiev, I.N.

1994-01-01

By means of thermal differential analysis, X-ray and microstructural analysis the state diagram of Pr-Bi system was studied. Following intermetallic compounds were defined in the system: Pr 2 Bi, Pr 5 Bi 3 , Pr 4 Bi 3 , Pr Bi, PrBi 2 , Pr 2 Bi, Pr 5 Bi 3 , Pr 4 Bi 3 and PrBi 2 . The data analysis on Ln-Bi diagram allowed to determine the regularity of change of properties of intermetallic compounds in the line of rare earth elements of cerium subgroup.

Maximum Likelihood Reconstruction for Magnetic Resonance Fingerprinting.

Science.gov (United States)

Zhao, Bo; Setsompop, Kawin; Ye, Huihui; Cauley, Stephen F; Wald, Lawrence L

2016-08-01

This paper introduces a statistical estimation framework for magnetic resonance (MR) fingerprinting, a recently proposed quantitative imaging paradigm. Within this framework, we present a maximum likelihood (ML) formalism to estimate multiple MR tissue parameter maps directly from highly undersampled, noisy k-space data. A novel algorithm, based on variable splitting, the alternating direction method of multipliers, and the variable projection method, is developed to solve the resulting optimization problem. Representative results from both simulations and in vivo experiments demonstrate that the proposed approach yields significantly improved accuracy in parameter estimation, compared to the conventional MR fingerprinting reconstruction. Moreover, the proposed framework provides new theoretical insights into the conventional approach. We show analytically that the conventional approach is an approximation to the ML reconstruction; more precisely, it is exactly equivalent to the first iteration of the proposed algorithm for the ML reconstruction, provided that a gridding reconstruction is used as an initialization.

A distributed multi-GPU system for high speed electron microscopic tomographic reconstruction.

Science.gov (United States)

Zheng, Shawn Q; Branlund, Eric; Kesthelyi, Bettina; Braunfeld, Michael B; Cheng, Yifan; Sedat, John W; Agard, David A

2011-07-01

Full resolution electron microscopic tomographic (EMT) reconstruction of large-scale tilt series requires significant computing power. The desire to perform multiple cycles of iterative reconstruction and realignment dramatically increases the pressing need to improve reconstruction performance. This has motivated us to develop a distributed multi-GPU (graphics processing unit) system to provide the required computing power for rapid constrained, iterative reconstructions of very large three-dimensional (3D) volumes. The participating GPUs reconstruct segments of the volume in parallel, and subsequently, the segments are assembled to form the complete 3D volume. Owing to its power and versatility, the CUDA (NVIDIA, USA) platform was selected for GPU implementation of the EMT reconstruction. For a system containing 10 GPUs provided by 5 GTX295 cards, 10 cycles of SIRT reconstruction for a tomogram of 4096(2) × 512 voxels from an input tilt series containing 122 projection images of 4096(2) pixels (single precision float) takes a total of 1845 s of which 1032 s are for computation with the remainder being the system overhead. The same system takes only 39 s total to reconstruct 1024(2) × 256 voxels from 122 1024(2) pixel projections. While the system overhead is non-trivial, performance analysis indicates that adding extra GPUs to the system would lead to steadily enhanced overall performance. Therefore, this system can be easily expanded to generate superior computing power for very large tomographic reconstructions and especially to empower iterative cycles of reconstruction and realignment. Copyright © 2011 Elsevier B.V. All rights reserved.

Comparison of methods for suppressing edge and aliasing artefacts in iterative x-ray CT reconstruction

International Nuclear Information System (INIS)

Zbijewski, Wojciech; Beekman, Freek J

2006-01-01

X-ray CT images obtained with iterative reconstruction (IR) can be hampered by the so-called edge and aliasing artefacts, which appear as interference patterns and severe overshoots in the areas of sharp intensity transitions. Previously, we have demonstrated that these artefacts are caused by discretization errors during the projection simulation step in IR. Although these errors are inherent to IR, they can be adequately suppressed by reconstruction on an image grid that is finer than that typically used for analytical methods such as filtered back-projection. Two other methods that may prevent edge artefacts are: (i) smoothing the projections prior to reconstruction or (ii) using an image representation different from voxels; spherically symmetric Kaiser-Bessel functions are a frequently employed example of such a representation. In this paper, we compare reconstruction on a fine grid with the two above-mentioned alternative strategies for edge artefact reduction. We show that the use of a fine grid results in a more adequate suppression of artefacts than the smoothing of projections or using the Kaiser-Bessel image representation

Denoising multicriterion iterative reconstruction in emission spectral tomography

Science.gov (United States)

Wan, Xiong; Yin, Aihan

2007-03-01

In the study of optical testing, the computed tomogaphy technique has been widely adopted to reconstruct three-dimensional distributions of physical parameters of various kinds of fluid fields, such as flame, plasma, etc. In most cases, projection data are often stained by noise due to environmental disturbance, instrumental inaccuracy, and other random interruptions. To improve the reconstruction performance in noisy cases, an algorithm that combines a self-adaptive prefiltering denoising approach (SPDA) with a multicriterion iterative reconstruction (MCIR) is proposed and studied. First, the level of noise is approximately estimated with a frequency domain statistical method. Then the cutoff frequency of a Butterworth low-pass filter was established based on the evaluated noise energy. After the SPDA processing, the MCIR algorithm was adopted for limited-view optical computed tomography reconstruction. Simulated reconstruction of two test phantoms and a flame emission spectral tomography experiment were employed to evaluate the performance of SPDA-MCIR in noisy cases. Comparison with some traditional methods and experiment results showed that the SPDA-MCIR combination had obvious improvement in the case of noisy data reconstructions.

Interval-based reconstruction for uncertainty quantification in PET

Science.gov (United States)

Kucharczak, Florentin; Loquin, Kevin; Buvat, Irène; Strauss, Olivier; Mariano-Goulart, Denis

2018-02-01

A new directed interval-based tomographic reconstruction algorithm, called non-additive interval based expectation maximization (NIBEM) is presented. It uses non-additive modeling of the forward operator that provides intervals instead of single-valued projections. The detailed approach is an extension of the maximum likelihood—expectation maximization algorithm based on intervals. The main motivation for this extension is that the resulting intervals have appealing properties for estimating the statistical uncertainty associated with the reconstructed activity values. After reviewing previously published theoretical concepts related to interval-based projectors, this paper describes the NIBEM algorithm and gives examples that highlight the properties and advantages of this interval valued reconstruction.

Pr:YLF orange laser investigation at cryogenic temperature

Czech Academy of Sciences Publication Activity Database

Fibrich, Martin; Šulc, J.; Jelínková, H.

2015-01-01

Roč. 12, č. 9 (2015), 1-23, č. článku 095801. ISSN 1612-2011 R&D Projects: GA MŠk ED1.1.00/02.0061 Grant - others:ELI Beamlines(XE) CZ.1.05/1.1.00/02.0061 Institutional support: RVO:68378271 Keywords : Pr:YLF * diode pumping * InGaN laser diode * cryogenic temperature Subject RIV: BH - Optics, Masers, Laser s Impact factor: 2.391, year: 2015

Rational approximations for tomographic reconstructions

International Nuclear Information System (INIS)

Reynolds, Matthew; Beylkin, Gregory; Monzón, Lucas

2013-01-01

We use optimal rational approximations of projection data collected in x-ray tomography to improve image resolution. Under the assumption that the object of interest is described by functions with jump discontinuities, for each projection we construct its rational approximation with a small (near optimal) number of terms for a given accuracy threshold. This allows us to augment the measured data, i.e., double the number of available samples in each projection or, equivalently, extend (double) the domain of their Fourier transform. We also develop a new, fast, polar coordinate Fourier domain algorithm which uses our nonlinear approximation of projection data in a natural way. Using augmented projections of the Shepp–Logan phantom, we provide a comparison between the new algorithm and the standard filtered back-projection algorithm. We demonstrate that the reconstructed image has improved resolution without additional artifacts near sharp transitions in the image. (paper)

Optimisation of the ATLAS Track Reconstruction Software for Run-2

CERN Document Server

Salzburger, Andreas; The ATLAS collaboration

2015-01-01

Track reconstruction is one of the most complex element of the reconstruction of events recorded by ATLAS from collisions delivered by the LHC. It is the most time consuming reconstruction component in high luminosity environments. The flat budget projections for computing resources for Run-2 of the LHC together with the demands of reconstructing higher pile-up collision data at rates more than double those in Run-1 (an increase from 400 Hz to 1 kHz in trigger output) have put stringent requirements on the track reconstruction software. The ATLAS experiment has performed a two year long software campaign which aimed to reduce the reconstruction rate by a factor of three to meet the resource limitations for Run-2: the majority of the changes to achieve this were improvements to the track reconstruction software. The CPU processing time of ATLAS track reconstruction was reduced by more than a factor of three during this campaign without any loss of output information of the track reconstruction. We present the ...

Strategy on energy saving reconstruction of distribution networks based on life cycle cost

Science.gov (United States)

Chen, Xiaofei; Qiu, Zejing; Xu, Zhaoyang; Xiao, Chupeng

2017-08-01

Because the actual distribution network reconstruction project funds are often limited, the cost-benefit model and the decision-making method are crucial for distribution network energy saving reconstruction project. From the perspective of life cycle cost (LCC), firstly the research life cycle is determined for the energy saving reconstruction of distribution networks with multi-devices. Then, a new life cycle cost-benefit model for energy-saving reconstruction of distribution network is developed, in which the modification schemes include distribution transformers replacement, lines replacement and reactive power compensation. In the operation loss cost and maintenance cost area, the operation cost model considering the influence of load season characteristics and the maintenance cost segmental model of transformers are proposed. Finally, aiming at the highest energy saving profit per LCC, a decision-making method is developed while considering financial and technical constraints as well. The model and method are applied to a real distribution network reconstruction, and the results prove that the model and method are effective.

Novel Fourier-based iterative reconstruction for sparse fan projection using alternating direction total variation minimization

International Nuclear Information System (INIS)

Jin Zhao; Zhang Han-Ming; Yan Bin; Li Lei; Wang Lin-Yuan; Cai Ai-Long

2016-01-01

Sparse-view x-ray computed tomography (CT) imaging is an interesting topic in CT field and can efficiently decrease radiation dose. Compared with spatial reconstruction, a Fourier-based algorithm has advantages in reconstruction speed and memory usage. A novel Fourier-based iterative reconstruction technique that utilizes non-uniform fast Fourier transform (NUFFT) is presented in this work along with advanced total variation (TV) regularization for a fan sparse-view CT. The proposition of a selective matrix contributes to improve reconstruction quality. The new method employs the NUFFT and its adjoin to iterate back and forth between the Fourier and image space. The performance of the proposed algorithm is demonstrated through a series of digital simulations and experimental phantom studies. Results of the proposed algorithm are compared with those of existing TV-regularized techniques based on compressed sensing method, as well as basic algebraic reconstruction technique. Compared with the existing TV-regularized techniques, the proposed Fourier-based technique significantly improves convergence rate and reduces memory allocation, respectively. (paper)

Total Variation and Tomographic Imaging from Projections

DEFF Research Database (Denmark)

Hansen, Per Christian; Jørgensen, Jakob Heide

2011-01-01

or 3D reconstruction from noisy projections. We demonstrate that for a small signal-to-noise ratio, this new approach allows us to compute better (i.e., more reliable) reconstructions than those obtained by classical methods. This is possible due to the use of the TV reconstruction model, which...

Reconstruction of sparse-view X-ray computed tomography using adaptive iterative algorithms.

Science.gov (United States)

Liu, Li; Lin, Weikai; Jin, Mingwu

2015-01-01

In this paper, we propose two reconstruction algorithms for sparse-view X-ray computed tomography (CT). Treating the reconstruction problems as data fidelity constrained total variation (TV) minimization, both algorithms adapt the alternate two-stage strategy: projection onto convex sets (POCS) for data fidelity and non-negativity constraints and steepest descent for TV minimization. The novelty of this work is to determine iterative parameters automatically from data, thus avoiding tedious manual parameter tuning. In TV minimization, the step sizes of steepest descent are adaptively adjusted according to the difference from POCS update in either the projection domain or the image domain, while the step size of algebraic reconstruction technique (ART) in POCS is determined based on the data noise level. In addition, projection errors are used to compare with the error bound to decide whether to perform ART so as to reduce computational costs. The performance of the proposed methods is studied and evaluated using both simulated and physical phantom data. Our methods with automatic parameter tuning achieve similar, if not better, reconstruction performance compared to a representative two-stage algorithm. Copyright © 2014 Elsevier Ltd. All rights reserved.

Novel posterior reconstruction technique during robot-assisted laparoscopic prostatectomy: description and comparative outcomes.

Science.gov (United States)

Jeong, Chang Wook; Oh, Jong Jin; Jeong, Seong Jin; Hong, Sung Kyu; Byun, Seok-Soo; Choe, Gheeyoung; Lee, Sang Eun

2012-07-01

The aim of the present study was to assess the impact of a novel posterior reconstruction technique during robot-assisted laparoscopic prostatectomy on continence recovery. A total of 116 consecutive patients who received the novel posterior reconstruction (case group) were retrospectively compared with a cohort of 126 patients who did not receive posterior reconstruction (control group). The primary end-point was the duration of continence recovery (no pad use) after robot-assisted laparoscopic prostatectomy. The posterior reconstruction was obtained by opposing the median dorsal fibrous raphe to the posterior counterpart of the detrusor apron, rather than the Denonvilliers' fascia. The case group showed higher continence rates at all points of evaluation, which were 2 weeks (30.1% vs 19.8%), 1 month (58.4% vs 45.7%), 3 months (82.7% vs 70.5%) and 6 months postoperatively (95.3% vs 86.4%) (P = 0.007). Application of the novel posterior reconstruction technique, age and length of membranous urethra were significant variables for the complete recovery of continence on multivariable analysis. This study shows that the application of this novel PR technique significantly improves the recovery of continence in patients undergoing robot-assisted laparoscopic prostatectomy. © 2012 The Japanese Urological Association.

MRI isotropic resolution reconstruction from two orthogonal scans

Science.gov (United States)

Tamez-Pena, Jose G.; Totterman, Saara; Parker, Kevin J.

2001-07-01

An algorithm for the reconstructions of ISO-resolution volumetric MR data sets from two standard orthogonal MR scans having anisotropic resolution has been developed. The reconstruction algorithm starts by registering a pair of orthogonal volumetric MR data sets. The registration is done by maximizing the correlation between the gradient magnitude using a simple translation-rotation model in a multi-resolution approach. Then algorithm assumes that the individual voxels on the MR data are an average of the magnetic resonance properties of an elongated imaging volume. Then, the process is modeled as the projection of MR properties into a single sensor. This model allows the derivation of a set of linear equations that can be used to recover the MR properties of every single voxel in the SO-resolution volume given only two orthogonal MR scans. Projections on convex sets (POCS) was used to solve the set of linear equations. Experimental results show the advantage of having a ISO-resolution reconstructions for the visualization and analysis of small and thin muscular structures.

Optimization of reconstruction algorithms using Monte Carlo simulation

International Nuclear Information System (INIS)

Hanson, K.M.

1989-01-01

A method for optimizing reconstruction algorithms is presented that is based on how well a specified task can be performed using the reconstructed images. Task performance is numerically assessed by a Monte Carlo simulation of the complete imaging process including the generation of scenes appropriate to the desired application, subsequent data taking, reconstruction, and performance of the stated task based on the final image. The use of this method is demonstrated through the optimization of the Algebraic Reconstruction Technique (ART), which reconstructs images from their projections by a iterative procedure. The optimization is accomplished by varying the relaxation factor employed in the updating procedure. In some of the imaging situations studied, it is found that the optimization of constrained ART, in which a nonnegativity constraint is invoked, can vastly increase the detectability of objects. There is little improvement attained for unconstrained ART. The general method presented may be applied to the problem of designing neutron-diffraction spectrometers. 11 refs., 6 figs., 2 tabs

Optimization of reconstruction algorithms using Monte Carlo simulation

International Nuclear Information System (INIS)

Hanson, K.M.

1989-01-01

A method for optimizing reconstruction algorithms is presented that is based on how well a specified task can be performed using the reconstructed images. Task performance is numerically assessed by a Monte Carlo simulation of the complete imaging process including the generation of scenes appropriate to the desired application, subsequent data taking, reconstruction, and performance of the stated task based on the final image. The use of this method is demonstrated through the optimization of the Algebraic Reconstruction Technique (ART), which reconstructs images from their projections by an iterative procedure. The optimization is accomplished by varying the relaxation factor employed in the updating procedure. In some of the imaging situations studied, it is found that the optimization of constrained ART, in which a non-negativity constraint is invoked, can vastly increase the detectability of objects. There is little improvement attained for unconstrained ART. The general method presented may be applied to the problem of designing neutron-diffraction spectrometers. (author)

Direct cone beam SPECT reconstruction with camera tilt

International Nuclear Information System (INIS)

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

1993-01-01

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

Prion protein (PrP) gene-knockout cell lines: insight into functions of the PrP