Scatter Correction And 4d Reconstruction Of Cone Beam Computed Tomography Cbct With A Moving Blocker

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Scatter Correction and 4D Reconstruction of Cone Beam Computed Tomography (CBCT) with a Moving Blocker

Author : Cong Zhao (Ph.D.)
Publisher :
ISBN 13 :
Total Pages : 125 pages
Book Rating : 4.:/5 (132 download)

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Book Synopsis Scatter Correction and 4D Reconstruction of Cone Beam Computed Tomography (CBCT) with a Moving Blocker by : Cong Zhao (Ph.D.)

Download or read book Scatter Correction and 4D Reconstruction of Cone Beam Computed Tomography (CBCT) with a Moving Blocker written by Cong Zhao (Ph.D.) and published by . This book was released on 2019 with total page 125 pages. Available in PDF, EPUB and Kindle. Book excerpt: Come-beam computed tomography (CBCT) is being widely used as an image guidance tool in radiation therapy nowadays. The quality of CBCT image is important to localize and delineate the tumor and to define relevant volumes when the patient is in the treatment position. However, there are several factors that can deteriorate the image quality of CBCT. The large amount of scatter signal due to the use of the flat panel detector (FPD) is a major factor and greatly degrades the quality of reconstruction images. Another major factor is the respiratory motion of the patient, which can cause severe motion blurring artifacts. Although four dimensional (4D) CBCT has been developed to reduce the motion artifacts, it increases the radiation dose in order to get satisfactory reconstruction images as the conventional phase-by-phase reconstruction for 4D CBCT requires more projection data than 3D CBCT. In this dissertation, we propose some methods to address these problems.After the brief introduction of CBCT, the factors that deteriorate the CBCT image quality and the existing studies are reviewed. Next, the moving blocker scatter correction method for CBCT is introduced and its optimization using different deconvolution methods is investigated through a simulation study and a slanted-edge experimental study. A robust moving blocker scatter correction method is further developed, which uses multiple adjacent projection views to estimate a more accurate scatter distribution.Finally, 4D CBCT with a moving blocker is developed for simultaneous dose reduction and scatter correction. The effectiveness of the proposed scatter correction and 4D reconstruction methods is demonstrated either by simulations of digital phantoms or real phantom and clinical CBCT data.

Blocker-based Scatter Correction for Cone-beam Computed Tomography

Author : Cong Zhao
Publisher :
ISBN 13 :
Total Pages : 50 pages
Book Rating : 4.:/5 (1 download)

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Book Synopsis Blocker-based Scatter Correction for Cone-beam Computed Tomography by : Cong Zhao

Download or read book Blocker-based Scatter Correction for Cone-beam Computed Tomography written by Cong Zhao and published by . This book was released on 2017 with total page 50 pages. Available in PDF, EPUB and Kindle. Book excerpt: Cone-beam computed tomography (CBCT) imaging is widely used in radiation therapy for treatment planning and image-guided therapy. More x-ray scatter signals are detected by the two-dimensional detector arrays in CBCT than by the one-dimensional detector arrays in fan-beam CT (FBCT). Therefore, scatter contamination significantly degrades the image quality in CBCT and must be corrected for satisfying image quality. Among numerous scatter correction (SC) methods of cone-beam computed tomography (CBCT), the use of lead-strip blockers is low-cost and easy to implement and holds potential to significantly lower patient radiation dose. In such a method, the signal in the blocked regions is assumed to be the scatter signal and can be used to estimate the scatter signal in the unblocked region. However, this assumption is often violated because of the penumbra effect and detector response effect. In this study, we first investigated a moving-blocker based method to simultaneously estimate the scatter signal and reconstruct the complete volume within the field of view (FOV) from a single CBCT scan. Then we proposed to use deconvolution algorithms to improve scatter estimation of the moving-blocker method. A slanted edge method was used to estimate the point spread function (PSF) of the flat panel detector. The parametric PSF was used in simulation studies to deconvolve the blurred projection image to remove the finite x-ray source and the detector response effect and to get cleaner scatter signal in the blocked regions. Our results showed that with laborious parameter tuning, the scatter-induced shading artifacts are substantially reduced in CBCT, and the CT number errors in the selected regions of interest are greatly reduced using the moving-blocker method. The detector response function can be reliably measured and calculated using the slanted edge method. The deconvolved projection image shows better quality, more accurate intensity profiles, and much reduced overall root mean square errors compared to the blurred image in the simulation study. Our experiment results further demonstrate that Wiener and Richardson-Lucy deconvolution methods can significantly improve the scatter estimation compared to the direct inverse filtering method. Finally, The PSF derived from the slanted edge experiment does not take the penumbra effect into account, and the air-scan data from the CBCT projection images of moving blockers fail to derive a reliable PSF. An experiment to determine the combined penumbra and detector response effect and the ultimate effectiveness of deconvolution methods on scatter correction of CBCT reconstruction will be investigated in future work.

Cone Beam Computed Tomography

Author : Chris C. Shaw
Publisher : Taylor & Francis
ISBN 13 : 143984626X
Total Pages : 272 pages
Book Rating : 4.4/5 (398 download)

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Book Synopsis Cone Beam Computed Tomography by : Chris C. Shaw

Download or read book Cone Beam Computed Tomography written by Chris C. Shaw and published by Taylor & Francis. This book was released on 2014-02-14 with total page 272 pages. Available in PDF, EPUB and Kindle. Book excerpt: Conventional computed tomography (CT) techniques employ a narrow array of x-ray detectors and a fan-shaped x-ray beam to rotate around the patient to produce images of thin sections of the patient. Large sections of the body are covered by moving the patient into the rotating x-ray detector and x-ray source gantry. Cone beam CT is an alternative technique using a large area detector and cone-shaped x-ray beam to produce 3D images of a thick section of the body with one full angle (360 degree or 180 degree plus detector coverage) rotation. It finds applications in situations where bulky, conventional CT systems would interfere with clinical procedures or cannot be integrated with the primary treatments or imaging systems. Cone Beam Computed Tomography explores the past, present, and future state of medical x-ray imaging while explaining how cone beam CT, with its superior spatial resolution and compact configuration, is used in clinical applications and animal research. The book: Supplies a detailed introduction to cone beam CT, covering basic principles and applications as well as advanced techniques Explores state-of-the-art research and future developments while examining the fundamental limitations of the technology Addresses issues related to implementation and system characteristics, including image quality, artifacts, radiation dose, and perception Reviews the historical development of medical x-ray imaging, from conventional CT techniques to volumetric 3D imaging Discusses the major components of cone beam CT: image acquisition, reconstruction, processing, and display A reference work for scientists, engineers, students, and imaging professionals, Cone Beam Computed Tomography provides a solid understanding of the theory and implementation of this revolutionary technology.

Motion Estimation and Motion-compensated Reconstruction for Four-dimensional Cone Beam Computed Tomography (4D-CBCT)

Author : Xiaokun Huang
Publisher :
ISBN 13 :
Total Pages : 125 pages
Book Rating : 4.:/5 (133 download)

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Book Synopsis Motion Estimation and Motion-compensated Reconstruction for Four-dimensional Cone Beam Computed Tomography (4D-CBCT) by : Xiaokun Huang

Download or read book Motion Estimation and Motion-compensated Reconstruction for Four-dimensional Cone Beam Computed Tomography (4D-CBCT) written by Xiaokun Huang and published by . This book was released on 2020 with total page 125 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Interpretation Basics of Cone Beam Computed Tomography

Author : Shawneen M. Gonzalez
Publisher : John Wiley & Sons
ISBN 13 : 1119685842
Total Pages : 258 pages
Book Rating : 4.1/5 (196 download)

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Book Synopsis Interpretation Basics of Cone Beam Computed Tomography by : Shawneen M. Gonzalez

Download or read book Interpretation Basics of Cone Beam Computed Tomography written by Shawneen M. Gonzalez and published by John Wiley & Sons. This book was released on 2021-11-09 with total page 258 pages. Available in PDF, EPUB and Kindle. Book excerpt: Interpretation Basics of Cone Beam Computed Tomography, Second Edition is a practical identification guide for interpreting CBCT findings in dental practice. Offering multiple high-quality images for each example provided, this easy-to-use guide is designed for those new to CBCT scans as well as more experienced practitioners in need of a reference tool of normal anatomy, common anatomical variants, and incidental findings. Extensively revised throughout, the Second Edition features a brand-new chapter on findings of the maxilla and mandible, and additional incidental findings and common anatomical variants. Every chapter in the book now includes sections covering anatomic variations, developmental anomalies, pathosis, and other considerations. All information has been carefully reviewed and updated to incorporate recent research in the field and reflect newer guidelines from various specialty organizations. This new edition: Enables rapid reference to common CBCT findings, with multiple images for each finding Features a streamlined framework that makes relevant information easier to find and apply in dental practice Offers hundreds of new images to aid in correctly identifying findings Contains new and updated content, including expanded coverage of CBCT and implants Provides sample reports and explains how they are used in day-to-day clinical practice Interpretation Basics of Cone Beam Computed Tomography, Second Edition remains a must-have resource for all dental practitioner and specialists who use CBCT, dental students in radiology interpretation courses, and residents beginning to use CBCT in their specialty.

Novel Methods to Address Data Truncation Artifacts and Streaking Artifacts in 4D Cone-beam Computed Tomography

Author : Shuai Leng
Publisher :
ISBN 13 :
Total Pages : 160 pages
Book Rating : 4.:/5 (891 download)

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Book Synopsis Novel Methods to Address Data Truncation Artifacts and Streaking Artifacts in 4D Cone-beam Computed Tomography by : Shuai Leng

Download or read book Novel Methods to Address Data Truncation Artifacts and Streaking Artifacts in 4D Cone-beam Computed Tomography written by Shuai Leng and published by . This book was released on 2008 with total page 160 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Circular Reconstruction and Scatter Correction in X-ray Cone-beam CT

Author : Lei Zhu
Publisher :
ISBN 13 : 9781109918649
Total Pages : 248 pages
Book Rating : 4.9/5 (186 download)

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Book Synopsis Circular Reconstruction and Scatter Correction in X-ray Cone-beam CT by : Lei Zhu

Download or read book Circular Reconstruction and Scatter Correction in X-ray Cone-beam CT written by Lei Zhu and published by . This book was released on 2007 with total page 248 pages. Available in PDF, EPUB and Kindle. Book excerpt: With the development of advanced computing and flat panel detector technology, volumetric X-ray computed tomography (CT) systems using large-area detectors, such as cone-beam CT (CBCT), are becoming more popular. This dissertation describes work aimed at reducing three types of image artifacts in CBCT.

Scattering Correction in Cone Beam Tomography Using Continuously Thickness-adapted Kernels

Author : Navnina Bhatia 1990-.....
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (112 download)

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Book Synopsis Scattering Correction in Cone Beam Tomography Using Continuously Thickness-adapted Kernels by : Navnina Bhatia 1990-.....

Download or read book Scattering Correction in Cone Beam Tomography Using Continuously Thickness-adapted Kernels written by Navnina Bhatia 1990-..... and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Advanced Cone Beam Computed Tomography (CBCT) typically uses a divergent conebeam source and a large area detector. As a result, there an inevitable increase in the size area of illumination causing an increase in the intensity of X-ray scatter signal, both from the object and the detector. This leads to the violation of prime assumption of reconstruction process which is based on straight line integrals path followed by the photons. Consequently scatter artifacts appear in the reconstruction images as steaks, cupping effect and thus produce wrong reconstruction values. Due to the severity of the reconstruction artifact caused by scatter, many scatter corrections methods have been adopted in literature. The first part of this study, reviews most of the existing scatter correction methods. The effect of scattering becomes more prominent and challenging in case of X-ray source of high energy which is used in industrial Non Destructive Testing (NDT), due to higher scatter to primary ratio (SPR). Therefore, in this study, we propose a continuously thickness-adapted deconvolution approach based on improvements in the Scatter Kernel Superposition (SKS) method. In this method, the scatter kernels are analytically parameterized over the whole thickness range of the object under study to better sample the amplitude and shape of kernels with respect to the thickness. The method is tested for both homogeneous and heterogeneous objects as well as simulated and experimental data. Another important aspect of this study is the comprehensive evaluation of contribution of the detector scatter performed using continuous method by separating the contribution of scatter due to the object and the detector. This is performed by modeling the scatter kernels using a four-Gaussian model. In the first approach, we performed this evaluation based on simulation of kernels from Monte Carlo simulations and the corrections are performed on typical industrial experimental data. The results obtained prove that the scatter correction only due to the object is not sufficient to obtain reconstruction image, free from artifacts, as the detector also scatters considerably. In order to prove this point experimentally and to have a better modeling of the detector, we describe a method based on combination of experiments and simulations to calculate the scatter kernels. The results obtained also prove, the contribution of the detector scattering becomes important and the PSF of the detector is not constant as considered in the studies so far, but it varies to a great extend with the energy spectrum.

Atlas of Cone Beam Computed Tomography

Author : Yaser Safi
Publisher : John Wiley & Sons
ISBN 13 : 1119667771
Total Pages : 468 pages
Book Rating : 4.1/5 (196 download)

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Book Synopsis Atlas of Cone Beam Computed Tomography by : Yaser Safi

Download or read book Atlas of Cone Beam Computed Tomography written by Yaser Safi and published by John Wiley & Sons. This book was released on 2022-02-14 with total page 468 pages. Available in PDF, EPUB and Kindle. Book excerpt: A comprehensive collection of oral and maxillofacial cases using cone beam CT imaging Atlas of Cone Beam Computed Tomography delivers a robust collection of cases using this advanced method of imaging for oral and maxillofacial radiology. The book features over 1,500 high-quality CBCT scans with succinct descriptions covering a wide range of maxillofacial region conditions, including normal anatomy, anomalies, inflammatory diseases, and degenerative diseases. Easy to navigate and featuring multiple images of normal variation and pathologies, the book offers readers guidance on the diagnostic values of CBCT, as well as CBCT images of the inferior alveolar nerve canal, dental implants, temporomandibular joint evaluations, and surgical interventions. The book also includes: A thorough introduction to cone beam computed tomography, including in vivo and in vitro preparation and evaluation, indications in dentistry, and indications in medicine Comprehensive explorations of cone beam computed tomography artefacts and anatomic landmarks Practical discussions of cone beam computed tomography of dental structure, including normal anatomy, anomalies, and the difficulties of eruption In-depth examinations of cone beam computed tomography of pathological growth and development, including maxillofacial congenital and developmental anomalies Perfect for graduate dental students and postgraduate dental students in oral and maxillofacial radiology, Atlas of Cone Beam Computed Tomography is also useful to general dentists, oral and maxillofacial radiologists, head and neck maxillofacial surgeons, head and neck radiologists, general radiologists, and ENT surgeons.

Scattering Correction in Cone Beam Tomography Using Continuously Thickness-adapted Kernels

Author : Navnina Bhatia
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (12 download)

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Book Synopsis Scattering Correction in Cone Beam Tomography Using Continuously Thickness-adapted Kernels by : Navnina Bhatia

Download or read book Scattering Correction in Cone Beam Tomography Using Continuously Thickness-adapted Kernels written by Navnina Bhatia and published by . This book was released on 2016 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Advanced Cone Beam Computed Tomography (CBCT) typically uses a divergent conebeam source and a large area detector. As a result, there an inevitable increase in the size area of illumination causing an increase in the intensity of X-ray scatter signal, both from the object and the detector. This leads to the violation of prime assumption of reconstruction process which is based on straight line integrals path followed by the photons. Consequently scatter artifacts appear in the reconstruction images as steaks, cupping effect and thus produce wrong reconstruction values. Due to the severity of the reconstruction artifact caused by scatter, many scatter corrections methods have been adopted in literature. The first part of this study, reviews most of the existing scatter correction methods. The effect of scattering becomes more prominent and challenging in case of X-ray source of high energy which is used in industrial Non Destructive Testing (NDT), due to higher scatter to primary ratio (SPR). Therefore, in this study, we propose a continuously thickness-adapted deconvolution approach based on improvements in the Scatter Kernel Superposition (SKS) method. In this method, the scatter kernels are analytically parameterized over the whole thickness range of the object under study to better sample the amplitude and shape of kernels with respect to the thickness. The method is tested for both homogeneous and heterogeneous objects as well as simulated and experimental data. Another important aspect of this study is the comprehensive evaluation of contribution of the detector scatter performed using continuous method by separating the contribution of scatter due to the object and the detector. This is performed by modeling the scatter kernels using a four-Gaussian model. In the first approach, we performed this evaluation based on simulation of kernels from Monte Carlo simulations and the corrections are performed on typical industrial experimental data. The results obtained prove that the scatter correction only due to the object is not sufficient to obtain reconstruction image, free from artifacts, as the detector also scatters considerably. In order to prove this point experimentally and to have a better modeling of the detector, we describe a method based on combination of experiments and simulations to calculate the scatter kernels. The results obtained also prove, the contribution of the detector scattering becomes important and the PSF of the detector is not constant as considered in the studies so far, but it varies to a great extend with the energy spectrum.

Cone Beam CT and 3D imaging

Author : Pietro Caruso
Publisher : Springer Science & Business Media
ISBN 13 : 8847053196
Total Pages : 159 pages
Book Rating : 4.8/5 (47 download)

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Book Synopsis Cone Beam CT and 3D imaging by : Pietro Caruso

Download or read book Cone Beam CT and 3D imaging written by Pietro Caruso and published by Springer Science & Business Media. This book was released on 2013-09-24 with total page 159 pages. Available in PDF, EPUB and Kindle. Book excerpt: Cone beam computed tomography (CBCT) has become the standard of reference in dental imaging. The distribution of CBCT devices is increasingly wide, and the number of required examinations is constantly growing. In this setting, it is now essential that medical and technical staff receive specific training in the use of CBCT and that technical guidelines for CBCT examinations are established. This clearly structured book on CBCT will be an ideal aid in daily clinical practice. It clearly explains basic CBCT anatomy, examination technique, and the use of 3D reformatting software. A wide range of cases are presented, covering the most frequent and relevant conditions and pathologies, including dental anomalies, inflammatory and degenerative disease, tumors, and implants.

Optimizing Cone Beam Computed Tomography (CBCT) System for Image Guided Radiation Therapy

Author : Chun Joo Park
Publisher :
ISBN 13 : 9781303194627
Total Pages : 160 pages
Book Rating : 4.1/5 (946 download)

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Book Synopsis Optimizing Cone Beam Computed Tomography (CBCT) System for Image Guided Radiation Therapy by : Chun Joo Park

Download or read book Optimizing Cone Beam Computed Tomography (CBCT) System for Image Guided Radiation Therapy written by Chun Joo Park and published by . This book was released on 2013 with total page 160 pages. Available in PDF, EPUB and Kindle. Book excerpt: Cone Beam Computed Tomography (CBCT) system is the most widely used imaging device in image guided radiation therapy (IGRT), where set of 3D volumetric image of patient can be reconstructed to identify and correct position setup errors prior to the radiation treatment. This CBCT system can significantly improve precision of on-line setup errors of patient position and tumor target localization prior to the treatment. However, there are still a number of issues that needs to be investigated with CBCT system such as 1) progressively increasing defective pixels in imaging detectors by its frequent usage, 2) hazardous radiation exposure to patients during the CBCT imaging, 3) degradation of image quality due to patients' respiratory motion when CBCT is acquired and 4) unknown knowledge of certain anatomical features such as liver, due to lack of soft-tissue contrast which makes tumor motion verification challenging. In this dissertation, we explore on optimizing the use of cone beam computed tomography (CBCT) system under such circumstances. We begin by introducing general concept of IGRT. We then present the development of automated defective pixel detection algorithm for X-ray imagers that is used for CBCT imaging using wavelet analysis. We next investigate on developing fast and efficient low-dose volumetric reconstruction techniques which includes 1) fast digital tomosynthesis reconstruction using general-purpose graphics processing unit (GPGPU) programming and 2) fast low-dose CBCT image reconstruction based on the Gradient-Projection-Barzilai-Borwein formulation (GP-BB). We further developed two efficient approaches that could reduce the degradation of CBCT images from respiratory motion. First, we propose reconstructing four dimensional (4D) CBCT and DTS using respiratory signal extracted from fiducial markers implanted in liver. Second, novel motion-map constrained image reconstruction (MCIR) is proposed that allows reconstruction of high quality and high phase resolution 4DCBCT images with no more than the imaging dose used in a standard Free Breathing 3DCBCT (FB-3DCBCT) scan. Finally, we demonstrate a method to analyze motion characteristics of liver that are particularly important for image guided stereotactic body radiation therapy (IG-SBRT). It is anticipated that all the approaches proposed in this study, which are both technically and clinically feasible, will allow much improvement in IGRT process.

Novel Methods for Scatter Correction and Dual Energy Imaging in Cone-beam CT

Author : Xue Dong
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (893 download)

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Book Synopsis Novel Methods for Scatter Correction and Dual Energy Imaging in Cone-beam CT by : Xue Dong

Download or read book Novel Methods for Scatter Correction and Dual Energy Imaging in Cone-beam CT written by Xue Dong and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Excessive imaging doses from repeated scans and poor image quality mainly due to scatter contamination are the two bottlenecks of cone-beam CT (CBCT) imaging. This study investigates a method that combines measurement-based scatter correction and a compressed sensing (CS)-based iterative reconstruction algorithm to generate scatter-free images from low-dose data. Scatter distribution is estimated by interpolating/extrapolating measured scatter samples inside blocked areas. CS-based iterative reconstruction is finally carried out on the under-sampled data to obtain scatter-free and low-dose CBCT images. In the tabletop phantom studies, with only 25% dose of a conventional CBCT scan, our method reduces the overall CT number error from over 220 HU to less than 25 HU, and increases the image contrast by a factor of 2.1 in the selected ROIs. Dual-energy CT (DECT) is another important application of CBCT. DECT shows promise in differentiating materials that are indistinguishable in single-energy CT and facilitates accurate diagnosis. A general problem of DECT is that decomposition is sensitive to noise in the two sets of projection data, resulting in severely degraded qualities of decomposed images. The first study of DECT is focused on the linear decomposition method. In this study, a combined method of iterative reconstruction and decomposition is proposed. The noise on the two initial CT images from separate scans becomes well correlated, which avoids noise accumulation during the decomposition process. To fully explore the benefits of DECT on beam-hardening correction and to reduce the computation cost, the second study is focused on an iterative decomposition method with a non-linear decomposition model for noise suppression in DECT. Phantom results show that our methods achieve superior performance on DECT imaging, with respect to noise reduction and spatial resolution.

Scatter Correction of 4D Cone Beam Computed Tomography Images for Respiratory Phase-dependent Proton Dose Calculation

Author : Henning Peter Schmitz
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (14 download)

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Book Synopsis Scatter Correction of 4D Cone Beam Computed Tomography Images for Respiratory Phase-dependent Proton Dose Calculation by : Henning Peter Schmitz

Download or read book Scatter Correction of 4D Cone Beam Computed Tomography Images for Respiratory Phase-dependent Proton Dose Calculation written by Henning Peter Schmitz and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

World Congress on Medical Physics and Biomedical Engineering May 26-31, 2012, Beijing, China

Author : Mian Long
Publisher : Springer Science & Business Media
ISBN 13 : 3642293050
Total Pages : 2385 pages
Book Rating : 4.6/5 (422 download)

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Book Synopsis World Congress on Medical Physics and Biomedical Engineering May 26-31, 2012, Beijing, China by : Mian Long

Download or read book World Congress on Medical Physics and Biomedical Engineering May 26-31, 2012, Beijing, China written by Mian Long and published by Springer Science & Business Media. This book was released on 2013-02-11 with total page 2385 pages. Available in PDF, EPUB and Kindle. Book excerpt: The congress’s unique structure represents the two dimensions of technology and medicine: 13 themes on science and medical technologies intersect with five challenging main topics of medicine to create a maximum of synergy and integration of aspects on research, development and application. Each of the congress themes was chaired by two leading experts. The themes address specific topics of medicine and technology that provide multiple and excellent opportunities for exchanges.

Artifacts Reduction Techniques in X-ray Cone-beam Computed Tomography Reconstruction

Author : Bowen Meng
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (876 download)

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Book Synopsis Artifacts Reduction Techniques in X-ray Cone-beam Computed Tomography Reconstruction by : Bowen Meng

Download or read book Artifacts Reduction Techniques in X-ray Cone-beam Computed Tomography Reconstruction written by Bowen Meng and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: CBCT is an important tool in image guided radiation therapy. With the existing reconstruction methods, however, various artifacts arise in the image, which are caused by under-sampled projection data, large-area detector, and/or presence of metal implants in patients. This dissertation addresses issues for improved CBCT image quality and clinical decision making. In practical CBCT systems, a circular trajectory is commonly used to acquire projections and reconstruct the volume. However, incomplete data might be collected in a short scan either because of mechanical constraint or dose reduction consideration. In such situation, FDK algorithm cannot provide an accurate image due to the theoretical limitation. In this dissertation, an iterative optimization using prior knowledge and rigid image registration is proposed to handle the limited angle reconstruction problem. The algorithm is derived based on the prior image constrained compressed sensing (PICCS) framework. The proposed algorithm is experimentally validated and compared with PICCS algorithm and demonstrates superior reconstruction accuracy. Large-area flat panel detector induces more scatter, which results in cupping and shading artifacts in the images. Various scatter correction methods have been proposed to reduce the artifacts from both hardware and software sides, but still suffer clinical applicability. In this dissertation, a single-scan scatter correction method using periphery scatter detection and compressed sensing technique is proposed and tested. The algorithm integrates the scatter measurement/reconstruction and projection acquisition into one scan with simple design of boundary lead blockers. It shows effective scatter artifacts reduction ability as well as promising practical usage for the existing CBCT systems. The presence of metals in patients may cause streaking artifacts in x-ray CT, which has long been recognized as a problem that not only limits the quality of CT images, but also makes dose calculation in radiation therapy planning problematic. In this dissertation, a method for binary reconstruction of metal objects is proposed to serve as the first step of metal artifacts reduction. The boundaries of metallic objects are obtained by using a penalized weighted least-squares algorithm with the adequate intensity gradient-controlled. A series of experimental studies are performed to evaluate the proposed approach, and show that when the projection data are sparse, a non-linear manipulation of projection data can greatly facilitate the binary reconstruction process to achieve accurate binary CT images.

Motion-induced Artifact Mitigation and Image Enhancement Strategies for Four-dimensional Fan-beam and Cone-beam Computed Tomography

Download Motion-induced Artifact Mitigation and Image Enhancement Strategies for Four-dimensional Fan-beam and Cone-beam Computed Tomography PDF Online Free

Author : Matthew J. Riblett
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (15 download)

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Book Synopsis Motion-induced Artifact Mitigation and Image Enhancement Strategies for Four-dimensional Fan-beam and Cone-beam Computed Tomography by : Matthew J. Riblett

Download or read book Motion-induced Artifact Mitigation and Image Enhancement Strategies for Four-dimensional Fan-beam and Cone-beam Computed Tomography written by Matthew J. Riblett and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Four dimensional imaging has become part of the standard of care for diagnosing and treating non-small cell lung cancer. In radiotherapy applications 4D fan-beam computed tomography (4D-CT) and 4D cone-beam computed tomography (4D-CBCT) are two advanced imaging modalities that afford clinical practitioners knowledge of the underlying kinematics and structural dynamics of diseased tissues and provide insight into the effects of regular organ motion and the nature of tissue deformation over time. While these imaging techniques can facilitate the use of more targeted radiotherapies, issues surrounding image quality and accuracy currently limit the utility of these images clinically. The purpose of this project is to develop methods that retrospectively compensate for anatomical motion in 4D-CBCT and correct motion artifacts present in 4D-CT to improve the image quality of reconstructed volume and assist in localizing respiration-influenced, diseased tissue and mobile structures of interest. In the first half of the project, a series of motion compensation (MoCo) workflow methods incorporating groupwise deformable image registration and projection-warped reconstruction were developed for use with 4D-CBCT imaging. In the latter half of the project, novel motion artifact observation and artifact- weighted groupwise registration-based image correction algorithms were designed and tested. Both deliverable components of this project were evaluated for their ability to enhance image quality when applied to clinical patient datasets and demonstrated qualitative and quantitative improvements over current state-of-the-art.