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An analytical image reconstruction algorithm to compensate for scattering angle broadening in Compton cameras

PHYSICS IN MEDICINE AND BIOLOGY 2003年第8期48卷 1009-1026页

作者： Hirasawa, M Tomitani, T Natl Inst Radiol Sci Dept Med Imaging Inage Ku Chiba 2638555 Japan

Compton cameras have been developed for use in gamma-ray astronomy and nuclear medicine. Their defining merit is that they do not need collimators;however, on the demerit side, they need inversion procedures for image reconstruction, since a measured datum is proportional to the integration of incident gamma rays along a cone surface with the same Compton scattering angle. First, an iteration method was adopted for this task. Later, analytical methods were found under restricted conditions. Parra (2000 IEEE Trans. Nucl. Sci. 47 1543-50) deduced a purely analytical reconstruction algorithm for a complete set of scattering-projection data that include data at all the scattering angles. Tomitani and Hirasawa (2002 Phys. Med. Biol. 47 2129-45) found that by making a slight modification, Parra's algorithm could be extended to the scattering-projection data in limited scattering angles. However, their algorithm neglected the effects of practical problems that cause the degradation of spatial resolution. Sources of degradation were identified as noise in the energy signal of their front detector and the Doppler effect in the scattering process. In this paper, we first analyse the effects of these sources on the angular resolution of the scattering-projection data and then present a revised reconstruction algorithm in which these two factors are incorporated. Simulation studies on digital phantoms reveal that the algorithm can reconstruct images even when these two factors are included.

关键词： Cameras energy signal Scattering image reconstruction Nuclear Medicine reconstruction algorithm collimators GAMMA RAY ASTRONOMY ANGULAR RESOLUTION Angle algorithms Doppler effect cone surface broadcasting Gamma Rays

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SIGNAL PROCESSING 2014年 95卷 101-110页

作者： Liu, Jing Mallick, Mahendra Han, ChongZhao Yao, XiangHua Lian, Feng Xi An Jiao Tong Univ Sch Elect & Informat Engn Xian 710049 Peoples R China

Deterministic sensing matrices are useful, because in practice, the sampler has to be a deterministic matrix. It is quite challenging to design a deterministic sensing matrix with low coherence. In this paper, we consider a more general condition, when the deterministic sensing matrix has high coherence and does not satisfy the restricted isometry property (RIP). A novel algorithm, called the similar sensing matrix pursuit (SSMP), is proposed to reconstruct a K-sparse signal, based on the original deterministic sensing matrix. The proposed algorithm consists of off-line and online processing. The goal of the off-line processing is to construct a similar compact sensing matrix containing as much information as possible from the original sensing matrix. The similar compact sensing matrix has low coherence, which guarantees a perfect reconstruction of the sparse vector with high probability. The online processing begins when measurements arrive, and consists of rough and refined estimation processes. Results from our simulation show that the proposed algorithm obtains much better performance while coping with a deterministic sensing matrix with high coherence compared with the subspace pursuit (SP) and basis pursuit (BP) algorithms. (C) 2013 Elsevier B.V. All rights reserved.

关键词： Compressed sensing Deterministic sensing matrix reconstruction algorithm Similar sensing matrix pursuit algorithm

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An efficient and accurate reconstruction algorithm for the formulation of cell-centered diffusion schemes

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JOURNAL OF COMPUTATIONAL PHYSICS 2012年第20期231卷 6935-6952页

作者： Chang, Lina Yuan, Guangwei Inst Appl Phys & Computat Math Natl Key Lab Sci & Technol Computat Phys Beijing 100088 Peoples R China

A new reconstruction algorithm is proposed for constructing cell-centered diffusion schemes on distorted meshes. Its main feature is that edge unknowns are defined at certain balance points, the locations of which depend on the diffusion coefficient and the skewness of grid cells, so as to obtain a two-point reconstruction stencil. Implementing the new algorithm for the approximation of gradients, we extend the IDC (improved deferred correction) scheme, which was proposed by Traore et al. [P. Traore, Y. Ahipo, C. Louste, A robust and efficient finite volume scheme for the discretization of diffusive flux on extremely skewed meshes in complex geometries, J. Comput. Phys. 228 (2009) 5148-5159], to handle diffusion problems with discontinuous coefficients. Numerical results demonstrate the accuracy and efficiency of the extended scheme. (C) 2012 Elsevier Inc. All rights reserved.

关键词： Diffusion equation reconstruction algorithm Discontinuous coefficient Skewed meshes

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Three-dimensional finite-element-based photoacoustic tomography: reconstruction algorithm and simulations

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MEDICAL PHYSICS 2007年第2期34卷 538-546页

作者： Yuan, Zhen Jiang, Huabei Univ Florida Dept Biomed Engn Gainesville FL 32611 USA

In this paper, a finite element reconstruction algorithm for three-dimensional photoacoustic tomography is described. The algorithm is based on rigorous iterative solution to the Helmholtz photoacoustic wave equation coupled with regularization techniques and is able to recover both the images of absorbed optical energy density and acoustic speed simultaneously. The algorithm is tested using various numerical examples that mimic cancer detection and joint imaging. The results show that the algorithm is able to reconstruct photoacoustic images quantitatively in terms of the location, size, optical and acoustic properties of the target, and background media for various examples examined. (c) 2007 American Association of Physicists in Medicine.

关键词： reconstruction algorithm three-dimensional photoacoustic tomography imaging

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A modified reconstruction algorithm for Fresnel volume tomography

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COMPUTERS & GEOSCIENCES 2009年第12期35卷 2365-2367页

作者： Zhang, Jianzhong Xiamen Univ Sch Informat Sci & Technol Xiamen 361005 Peoples R China

Fresnel volume tomography has advantages of reducing the dimension of the null space of the Frechet matrix, and improving the inversion solution. However, there is an error in the reconstruction algorithm of Grandjean and Sage (2004) for traveltime tomography using Fresnel wavepath. Our modified reconstruction algorithm based on Fresnel weights at grid nodes has shown to be valid from a synthetic test.

关键词： Valid Tomography Travel time reconstruction algorithm

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Iterative reconstruction algorithm for half-cover dual helical cone-beam computed tomography

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INSIGHT 2013年第5期55卷 232-236页

作者： Zhao, Yunsong Zou, Xiaobing Yu, Wei Capital Normal Univ Sch Math CT Lab Beijing Peoples R China Chongqing Univ Educ Dept Math & Informat Engn Chongqing Peoples R China Chongqing Univ Coll Optoelect Engn Chongqing 630044 Peoples R China

Cone-beam computed tomography (CT) can be used for rapid volumetric imaging with high longitudinal resolution and is used extensively in a variety of non-destructive testing (NDT) and non-destructive evaluation (NDE) applications. But the field of view (FOV) of cone-beam CT is limited because of the limited size of the panel detector. In order to enlarge the FOV of cone-beam CT several scan modes are proposed, one of which is the half-cover dual helical scan mode. In half-cover dual helical cone-beam CT, the inspected object is scanned by two transversely truncated helical scans and two sets of truncated projections, which are complementary to each other, are acquired. Dual helical cone-beanz CT can not only enlarge the FOV longitudinally, but also transversely. One author of this paper has proposed extended FDK and Katsevich-type algorithms for dual helical cone-beam CT. But both of the two algorithms are approximate algorithms. So, inevitably, there are slight artifacts (including drifting of the CT values) appearing in the reconstructed images, which may affect the subsequent interpretation of the reconstructed images. In order to improve the image quality further, we propose a modified SART iterative algorithm for dual helical cone-beam CT. Generally speaking, iterative reconstruction algorithms are applicable to any scan mode, however, direct SART reconstruction may introduce artifacts in the images because of data truncation in the projections. So, we make some modifications to the SART method to avoid artifacts in the images. Numerical experiments verify the proposed algorithm and the reconstruction results show that the images reconstructed by the modified SART algorithm are superior to those reconstructed by the extended FDK and Katsevich-type algorithms. Another advantage of the proposed algorithm is that it can make full use of the obtained projections rather than only parts of the projections.

关键词： reconstruction algorithm Nondestructive Testing Cone-Beam Computed Tomography algorithms Dual Spiral Cone-Beam Computed Tomography images helical scanning

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Squamous cell carcinoma of lip: Clinical feature analysis and suggestion of reconstruction algorithm

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JOURNAL OF DERMATOLOGY 2024年第6期51卷 799-806页

作者： Park, Jung Won Kim, Taehee Chung, Kee Yang Roh, Mi Ryung Yonsei Univ Coll Med Cutaneous Biol Res Inst Dept DermatolSeverance Hosp Seoul South Korea Yonsei Univ Gangnam Severance Hosp Cutaneous Biol Res Inst Dept DermatolColl Med Seoul South Korea Gangnam Severance Hosp Dept Dermatol Cutaneous Biol Res Inst 20 Eonjuro 63 Gil Seoul 06229 South Korea

reconstruction of lips after squamous cell carcinoma (SCC) removal should restore functional and aesthetic roles;however, it remains a challenge. In this study we describe the clinical features of lip SCC and suggest a reconstruction algorithm. We retrospectively analyzed 34 patients with lip SCC who underwent reconstruction after Mohs micrographic surgery between January 2006 and March 2022. The mean age of the patients was 70.2 years. Seven tumors were on the upper lip and 27 tumors were on the lower lip. Twenty-five defects were located on the mucosal lip, eight defects involved both the mucosal and cutaneous lips, and one defect was confined to the cutaneous lip. Eighteen defects were smaller than 50% of the total lip size, and 16 were larger than 50%. Primary closure was mostly performed for defects smaller than 50% of the lip size (9/18 cases), and local flap, according to the location and size of the defects, was performed for larger defects. Thirteen patients experienced postoperative complications but improved within 1 year after surgery, except for one patient. We suggest a reconstruction algorithm with a 50% cut-off value. Defects smaller than 50% of the lip size could be reconstructed by primary closure. Even larger defects could be reconstructed by creation of a local flap from the remaining adjacent tissue with minimal postoperative complications.

关键词： clinical feature lip reconstruction Mohs micrographic surgery reconstruction algorithm squamous cell carcinoma

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A novel iterative reconstruction algorithm allows reduced dose multidetector-row CT imaging of mechanical prosthetic heart valves

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INTERNATIONAL JOURNAL OF CARDIOVASCULAR IMAGING 2012年第6期28卷 1567-1575页

作者： Habets, Jesse Symersky, Petr de Mol, Bas A. J. M. Mali, Willem P. Th. M. Leiner, Tim Budde, Ricardo P. J. Univ Med Ctr Utrecht Dept Radiol NL-3508 GA Utrecht Netherlands Univ Amsterdam Acad Med Ctr Dept Cardiothorac Surg NL-1105 AZ Amsterdam Netherlands

Multidetector-row CT is promising for prosthetic heart valve (PHV) assessment but retrospectively ECG-gated scanning has a considerable radiation dose. Recently introduced iterative reconstruction (IR) algorithms may enable radiation dose reduction with retained image quality. Furthermore, PHV image quality on the CT scan mainly depends on extent of PHV artifacts. IR may decrease streak artifacts. We compared image noise and artifact volumes in scans of mechanical PHVs reconstructed with conventional filtered back projection (FBP) to lower dose scans reconstructed with IR. Four different PHVs (St. Jude, Carbomedics, ON-X and Medtronic Hall) were scanned in a pulsatile in vitro model. Ten retrospectively ECG-gated CT scans were performed of each PHV at 120 kV, 600 mAs (high-dose CTDIvol 35.3 mGy) and 120 kV, 300 mAs (low-dose CTDIvol 17.7 mGy) on a 64 detector-row scanner. Diastolic and systolic images were reconstructed with FBP (high and low-dose) and the IR algorithm (low-dose only). Hypo- and hyperdense artifact volumes were determined using two threshold filters. Image noise was measured. Mean hypo- and hyperdense artifact volumes (mm(3)) were 1,235/5,346 (high-dose FBP);2,405/6,877 (low-dose FBP) and 1,218/5,333 (low-dose IR). Low-dose IR reconstructions had similar image noise compared to high-dose FBP (16.5 +/- A 1.7 vs. 16.3 +/- A 1.6, mean +/- A SD, respectively, P = 1.0). IR allows ECG-gated PHV imaging with similar image noise and PHV artifacts at 50% less dose compared to conventional FBP in an pulsatile in vitro model.

关键词： Prosthetic heart valve Computed tomography Iterative reconstruction Artifacts Image noise reconstruction algorithm

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The design and testing of a solid phantom for the verification of a commercial 3D seed reconstruction algorithm

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RADIOTHERAPY AND ONCOLOGY 2005年第2期74卷 169-175页

作者： Siebert, FA Kohr, P Kovács, G Univ Hosp Schleswig Holstein Interdisciplinary Brachytherapy Ctr D-24105 Kiel Germany

Background and purpose: To test the implementation of a new solid phantom and to study the accuracy and the reliability of 3D seed reconstruction algorithms in prostate seed implants. Patients and methods: A solid phantom, the Kiel-phantom, to simulate prostate implants was designed. Several measurements were performed with this phantom to test the three-film seed reconstruction using a commercial planning system. Results: Precision of better than 0.1 mm (SD) were found for seed combinations when source projections do not overlap. If seeds overlapped from two or more gantry angles, the software showed serious miscomputations with seed displacements of more than 30.0 mm. Conclusions: Systematic measurements were carried out which demonstrated that the solid phantom can be an advantageous tool to increase the quality assessment for seed planning systems. (c) 2004 Elsevier Ireland Ltd. All rights reserved.

关键词： seed localization prostate brachytherapy reconstruction algorithm solid phantom

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TEMPERATURE-FIELD ESTIMATION USING ELECTRICAL-IMPEDANCE PROFILING METHODS .1. reconstruction algorithm AND SIMULATED RESULTS

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INTERNATIONAL JOURNAL OF HYPERTHERMIA 1994年第2期10卷 209-228页

作者： PAULSEN, KD MOSKOWITZ, MJ RYAN, TP DARTMOUTH COLL SCH MED LEBANON NH USA NORRIS COTTON CANC CTR LEBANON NH USA

algorithmic methods for estimating complete temperature fields during hyperthermia treatments based on surface and internal electrical measurements are presented. The techniques utilized draw upon impedance imaging concepts, but rather than limit the measurements to positions on the body surface, internal impedance recording sites are allowed. Theoretical simulations show that this strategy improves the reconstructed image in the target region when either internal measurement locations are added to a given number of external recording sites or some external measurement locations are replaced by internal recording positions. The algorithms developed are tested on a set of problems with increasing levels of complexity. The culmination of these investigations is a complete simulation of a hyperthermia treatment and reconstruction of a thermal image for a body cross-section of an actual cancer patient. The results of this work suggest that the surface plus internal measurement approach holds some promise as a method for estimating temperature distributions during hyperthermia treatments. However, the simulations while promising are idealizations in that they are two-dimensional with modest levels of additive noise. In a companion paper, we explore the viability of this approach in several laboratory phantom experiments which include both static and heat-induced transient electrical property profiles.

关键词： TEMPERATURE ESTIMATION IMPEDANCE IMAGING reconstruction algorithm INVERSE PROFILING FINITE ELEMENTS

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