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Galve P, Arias-Valcayo F, Villa-Abaunza A, Ibáñez P, Udías JM. UMC-PET: a fast and flexible Monte Carlo PET simulator. Phys Med Biol 2024; 69:035018. [PMID: 38198727 DOI: 10.1088/1361-6560/ad1cf9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2023] [Accepted: 01/10/2024] [Indexed: 01/12/2024]
Abstract
Objective.The GPU-based Ultra-fast Monte Carlo positron emission tomography simulator (UMC-PET) incorporates the physics of the emission, transport and detection of radiation in PET scanners. It includes positron range, non-colinearity, scatter and attenuation, as well as detector response. The objective of this work is to present and validate UMC-PET as a a multi-purpose, accurate, fast and flexible PET simulator.Approach.We compared UMC-PET against PeneloPET, a well-validated MC PET simulator, both in preclinical and clinical scenarios. Different phantoms for scatter fraction (SF) assessment following NEMA protocols were simulated in a 6R-SuperArgus and a Biograph mMR scanner, comparing energy histograms, NEMA SF, and sensitivity for different energy windows. A comparison with real data reported in the literature on the Biograph scanner is also shown.Main results.NEMA SF and sensitivity estimated by UMC-PET where within few percent of PeneloPET predictions. The discrepancies can be attributed to small differences in the physics modeling. Running in a 11 GB GeForce RTX 2080 Ti GPU, UMC-PET is ∼1500 to ∼2000 times faster than PeneloPET executing in a single core Intel(R) Xeon(R) CPU W-2155 @ 3.30 GHz.Significance.UMC-PET employs a voxelized scheme for the scanner, patient adjacent objects (such as shieldings or the patient bed), and the activity distribution. This makes UMC-PET extremely flexible. Its high simulation speed allows applications such as MC scatter correction, faster SRM estimation for complex scanners, or even MC iterative image reconstruction.
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Affiliation(s)
- Pablo Galve
- Grupo de Física Nuclear, EMFTEL & IPARCOS, Universidad Complutense de Madrid, CEI Moncloa, 28040 Madrid, Spain
- Université Paris Cité, Inserm, PARCC, F-75015 Paris, France
- Health Research Institute of the Hospital Clínico San Carlos (IdISSC), Madrid, Spain
| | - Fernando Arias-Valcayo
- Grupo de Física Nuclear, EMFTEL & IPARCOS, Universidad Complutense de Madrid, CEI Moncloa, 28040 Madrid, Spain
- Health Research Institute of the Hospital Clínico San Carlos (IdISSC), Madrid, Spain
| | - Amaia Villa-Abaunza
- Grupo de Física Nuclear, EMFTEL & IPARCOS, Universidad Complutense de Madrid, CEI Moncloa, 28040 Madrid, Spain
| | - Paula Ibáñez
- Grupo de Física Nuclear, EMFTEL & IPARCOS, Universidad Complutense de Madrid, CEI Moncloa, 28040 Madrid, Spain
- Health Research Institute of the Hospital Clínico San Carlos (IdISSC), Madrid, Spain
| | - José Manuel Udías
- Grupo de Física Nuclear, EMFTEL & IPARCOS, Universidad Complutense de Madrid, CEI Moncloa, 28040 Madrid, Spain
- Health Research Institute of the Hospital Clínico San Carlos (IdISSC), Madrid, Spain
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Study of 99mTc absorption on micro-sized ion exchange resins to achieve high activity for SPECT. Appl Radiat Isot 2022; 186:110256. [DOI: 10.1016/j.apradiso.2022.110256] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2021] [Revised: 04/20/2022] [Accepted: 04/21/2022] [Indexed: 11/30/2022]
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3
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Auditore L, Pistone D, Amato E, Italiano A. Monte Carlo methods in nuclear medicine. Nucl Med Mol Imaging 2022. [DOI: 10.1016/b978-0-12-822960-6.00136-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
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Lukas M, Kluge A, Beindorff N, Brenner W. Accurate Monte Carlo Modeling of Small-Animal Multi-Pinhole SPECT for Non-Standard Multi-Isotope Applications. IEEE TRANSACTIONS ON MEDICAL IMAGING 2021; 40:2208-2220. [PMID: 33861700 DOI: 10.1109/tmi.2021.3073749] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Recent advances in preclinical SPECT instrumentation enable non-standard multi-isotope acquisitions at the edge of physical feasibility to improve efficiency of pharmaceutical research. Due to the variety of applications, optimization of imaging hardware, acquisition protocols and reconstruction algorithms is a central and recurring task. For this purpose, we developed a Monte Carlo simulation model of a preclinical state-of-the-art multi-pinhole SPECT system, the NanoSPECT/CTPLUS, with emphasis on high accuracy for multi-isotope experiments operating near the system range limits. The GATE/ GEANT4 model included an accurate description of multi-pinhole collimators and all substructures of the detector back compartment. The readout electronics was modeled with a variety of signal processors partially extended to incorporate non-simplified measured response functions. The final model was able to predict energy spectra, planar images and tomographic reconstructions with high accuracy for both standard and non-standard multi-isotope experiments. Complex activity distributions could be reproduced for a wide range of noise levels and different modes of angular undersampling. Using the example of a dual-isotope triple-tracer experiment, the model has proven to be a powerful tool for protocol optimization and quantitative image correction at the performance range limits of multi-isotope multi-pinhole SPECT.
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Meng F, Shi Y, Li C, Li L, Qin W, Zhu S. Hybrid model of photon propagation based on the analytical and Monte Carlo methods for a dual-head PET system. Phys Med Biol 2021; 66. [PMID: 34330106 DOI: 10.1088/1361-6560/ac195b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2020] [Accepted: 07/30/2021] [Indexed: 11/12/2022]
Abstract
The construction of photon propagation has a close relationship with the quality of reconstructed images. The classical Monte Carlo (MC) based method can model the photon propagation precisely, but it is time-consuming. The analytical method can often quickly construct a model, but its precision is a problem. How to fully exploit the advantages of the MC simulation and analytical model is an open problem. Inspired by the characteristics of the depth of interaction (DOI) detectors, which can help confirm the deposited position of a photon with DOI-encoding technology, we virtually discretize each crystal into several subcrystals to obtain the statistical distribution by MC-based simulation. Then, the statistical distribution is combined with a spatially variant solid-angle model. This combination strategy provides a hybrid model to describe photon propagation with relatively high accuracy and low computational cost. Three discretization schemes are compared to optimize the constructed photon propagation model. Several experiments are carried out to evaluate the performance of the proposed hybrid method. The metrics of full width at half maximum (FWHM), contrast recovery (CR), and coefficient of variation (COV) are adopted to quantitate the imaging results. The classical MC-based method is compared as a gold-standard reference. When a crystal is divided into two discretized positions, the convergent tendencies of CRs and COVs are consistent with that based on MC simulation method, respectively. In terms of FWHMs, the resolutions of using the MC-based model and the proposed hybrid model are 0.71 mm and 0.68 mm in the direction parallel to the detector head, respectively. This indicates the potential of the proposed method in positron emission tomography imaging.
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Affiliation(s)
- Fanzhen Meng
- Engineering Research Center of Molecular and Neuro Imaging, Ministry of Education, School of Life Science and Technology, Xidian University, Xi'an, Shaanxi 710071, People's Republic of China
| | - Yu Shi
- Engineering Research Center of Molecular and Neuro Imaging, Ministry of Education, School of Life Science and Technology, Xidian University, Xi'an, Shaanxi 710071, People's Republic of China
| | - Chenfeng Li
- Engineering Research Center of Molecular and Neuro Imaging, Ministry of Education, School of Life Science and Technology, Xidian University, Xi'an, Shaanxi 710071, People's Republic of China
| | - Lei Li
- Engineering Research Center of Molecular and Neuro Imaging, Ministry of Education, School of Life Science and Technology, Xidian University, Xi'an, Shaanxi 710071, People's Republic of China
| | - Wei Qin
- Engineering Research Center of Molecular and Neuro Imaging, Ministry of Education, School of Life Science and Technology, Xidian University, Xi'an, Shaanxi 710071, People's Republic of China
| | - Shouping Zhu
- Engineering Research Center of Molecular and Neuro Imaging, Ministry of Education, School of Life Science and Technology, Xidian University, Xi'an, Shaanxi 710071, People's Republic of China
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Hoff G, Streck EE, Lai A, Fanti V, Golosio B, Nascimento CD, Souza EG. Using Geant4 Monte Carlo toolkit to evaluate a low power X-ray tube generator configuration. Appl Radiat Isot 2020; 168:109487. [PMID: 33339703 DOI: 10.1016/j.apradiso.2020.109487] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2019] [Revised: 10/14/2020] [Accepted: 10/15/2020] [Indexed: 10/23/2022]
Abstract
Monte Carlo technique has been widely used as an important tool to develop new irradiation equipment, prototype medical equipment parts, and test methodologies for dosimetry. In this manuscript, we present a methodology to design a low power X-ray tube generator using the Geant4 Monte Carlo toolkit. The simulations were performed considering a large number of variables, namely, the material composition of the target track, the window thickness, and the air pressure of the X-ray tube. The X-ray production was simulated considering monoenergetic electron beams impinging on targets of tungsten and copper with incident kinetic energies ranging from 20 keV to 60 keV and initial divergences from 5° to 30°. For the polyenergetic emission, a conservative approach with Gaussian energy distribution was adopted. The analysis indicates that among the evaluated parameters, the incident kinetic energy, and the target material produced the most notable changes in the spectra shape and conversion efficiency (CE), significantly impacting the X-ray tube design. The studies provide a reliable methodology to explore general configurations for X-ray tube generators, defining the best geometry, material compositions, and thicknesses to be used on spectroscopy applications.
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Affiliation(s)
- G Hoff
- Physics Department, University of Cagliari, Monserrato, Italy; Department of Cagliary, National Institute of Nuclear Physics, Monserrato, Italy; Medical Physics and Radioprotection Service, Hospital de Clínicas de Porto Alegre, Porto Alegre, Brazil.
| | - E E Streck
- Physics College at Pontifical Catholic University of Rio Grande do Sul (retired professor), Porto Alegre, Brazil
| | - A Lai
- Physics Department, University of Cagliari, Monserrato, Italy; Department of Cagliary, National Institute of Nuclear Physics, Monserrato, Italy
| | - V Fanti
- Physics Department, University of Cagliari, Monserrato, Italy; Department of Cagliary, National Institute of Nuclear Physics, Monserrato, Italy
| | - B Golosio
- Physics Department, University of Cagliari, Monserrato, Italy; Department of Cagliary, National Institute of Nuclear Physics, Monserrato, Italy
| | - C D Nascimento
- Graduate Program in Computer and Electronic Engineering at Catholic University of Pelotas, Pelotas, Brazil
| | - E G Souza
- Graduate Program in Computer and Electronic Engineering at Catholic University of Pelotas, Pelotas, Brazil
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Nguyen MP, Goorden MC, Beekman FJ. EXIRAD-HE: multi-pinhole high-resolution ex vivo imaging of high-energy isotopes. ACTA ACUST UNITED AC 2020; 65:225029. [DOI: 10.1088/1361-6560/abbb77] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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Nguyen MP, Goorden MC, Kamphuis C, Beekman FJ. Evaluation of pinhole collimator materials for micron-resolution ex vivo SPECT. ACTA ACUST UNITED AC 2019; 64:105017. [DOI: 10.1088/1361-6560/ab1618] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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9
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Wiyaporn K, Tocharoenchai C, Pusuwan P, Higuchi T, Fung GS, Feng T, Park MJ, Tsui BM. Optimization of imaging protocols for myocardial blood flow (MBF) quantification with 18 F-flurpiridaz PET. Phys Med 2017; 42:127-134. [DOI: 10.1016/j.ejmp.2017.08.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/29/2016] [Revised: 07/27/2017] [Accepted: 08/03/2017] [Indexed: 01/24/2023] Open
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Takahashi A, Miwa K, Sasaki M, Baba S. A Monte Carlo study on (223)Ra imaging for unsealed radionuclide therapy. Med Phys 2017; 43:2965-2974. [PMID: 27277045 DOI: 10.1118/1.4948682] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE Radium-223 ((223)Ra), an α-emitting radionuclide, is used in unsealed radionuclide therapy for metastatic bone tumors. The demand for qualitative (223)Ra imaging is growing to optimize dosimetry. The authors simulated (223)Ra imaging using an in-house Monte Carlo simulation code and investigated the feasibility and utility of (223)Ra imaging. METHODS The Monte Carlo code comprises two modules, hexagon and nai. The hexagon code simulates the photon and electron interactions in the tissues and collimator, and the nai code simulates the response of the NaI detector system. A 3D numeric phantom created using computed tomography images of a chest phantom was installed in the hexagon code. (223)Ra accumulated in a part of the spine, and three x-rays and 19 γ rays between 80 and 450 keV were selected as the emitted photons. To evaluate the quality of the (223)Ra imaging, the authors also simulated technetium-99m ((99m)Tc) imaging under the same conditions and compared the results. RESULTS The sensitivities of the three photopeaks were 147 counts per unit of source activity (cps MBq(-1); photopeak: 84 keV, full width of energy window: 20%), 166 cps MBq(-1) (154 keV, 15%), and 158 cps MBq(-1) (270 keV, 10%) for a low-energy general-purpose (LEGP) collimator, and those for the medium-energy general-purpose (MEGP) collimator were 33, 13, and 8.0 cps MBq(-1), respectively. In the case of (99m)Tc, the sensitivity was 55 cps MBq(-1) (141 keV, 20%) for LEGP and 52 cps MBq(-1) for MEGP. The fractions of unscattered photons of the total photons reflecting the image quality were 0.09 (84 keV), 0.03 (154 keV), and 0.02 (270 keV) for the LEGP collimator and 0.41, 0.25, and 0.50 for the MEGP collimator, respectively. Conversely, this fraction was approximately 0.65 for the simulated (99m)Tc imaging. The sensitivity with the LEGP collimator appeared very high. However, almost all of the counts were because of photons that penetrated or were scattered in the collimator; therefore, the proportions of unscattered photons were small. CONCLUSIONS Their simulation study revealed that the most promising scheme for (223)Ra imaging is an 84-keV window using an MEGP collimator. The sensitivity of the photopeaks above 100 keV is too low for (223)Ra imaging. A comparison of the fractions of unscattered photons reveals that the sensitivity and image quality are approximately two-thirds of those for (99m)Tc imaging.
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Affiliation(s)
- Akihiko Takahashi
- Faculty of Medical Sciences, Department of Health Sciences, Kyushu University, 3-1-1, Maidashi, Higashi-ku, Fukuoka 812-8582, Japan
| | - Kenta Miwa
- Faculty of Medical Sciences, Department of Health Sciences, Kyushu University, 3-1-1, Maidashi, Higashi-ku, Fukuoka 812-8582, Japan
| | - Masayuki Sasaki
- Faculty of Medical Sciences, Department of Health Sciences, Kyushu University, 3-1-1, Maidashi, Higashi-ku, Fukuoka 812-8582, Japan
| | - Shingo Baba
- Department of Clinical Radiology, Kyushu University Hospital, 3-1-1, Maidashi, Higashi-ku, Fukuoka 812-8582, Japan
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Xie T, Zaidi H. Development of computational small animal models and their applications in preclinical imaging and therapy research. Med Phys 2016; 43:111. [PMID: 26745904 DOI: 10.1118/1.4937598] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The development of multimodality preclinical imaging techniques and the rapid growth of realistic computer simulation tools have promoted the construction and application of computational laboratory animal models in preclinical research. Since the early 1990s, over 120 realistic computational animal models have been reported in the literature and used as surrogates to characterize the anatomy of actual animals for the simulation of preclinical studies involving the use of bioluminescence tomography, fluorescence molecular tomography, positron emission tomography, single-photon emission computed tomography, microcomputed tomography, magnetic resonance imaging, and optical imaging. Other applications include electromagnetic field simulation, ionizing and nonionizing radiation dosimetry, and the development and evaluation of new methodologies for multimodality image coregistration, segmentation, and reconstruction of small animal images. This paper provides a comprehensive review of the history and fundamental technologies used for the development of computational small animal models with a particular focus on their application in preclinical imaging as well as nonionizing and ionizing radiation dosimetry calculations. An overview of the overall process involved in the design of these models, including the fundamental elements used for the construction of different types of computational models, the identification of original anatomical data, the simulation tools used for solving various computational problems, and the applications of computational animal models in preclinical research. The authors also analyze the characteristics of categories of computational models (stylized, voxel-based, and boundary representation) and discuss the technical challenges faced at the present time as well as research needs in the future.
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Affiliation(s)
- Tianwu Xie
- Division of Nuclear Medicine and Molecular Imaging, Geneva University Hospital, Geneva 4 CH-1211, Switzerland
| | - Habib Zaidi
- Division of Nuclear Medicine and Molecular Imaging, Geneva University Hospital, Geneva 4 CH-1211, Switzerland; Geneva Neuroscience Center, Geneva University, Geneva CH-1205, Switzerland; and Department of Nuclear Medicine and Molecular Imaging, University of Groningen, University Medical Center Groningen, Groningen 9700 RB, The Netherlands
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Feng T, Wang J, Fung G, Tsui B. Non-rigid dual respiratory and cardiac motion correction methods after, during, and before image reconstruction for 4D cardiac PET. Phys Med Biol 2015; 61:151-68. [DOI: 10.1088/0031-9155/61/1/151] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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Lin HH, Chuang KS, Lin YH, Ni YC, Wu J, Jan ML. Efficient simulation of voxelized phantom in GATE with embedded SimSET multiple photon history generator. Phys Med Biol 2014; 59:6231-50. [DOI: 10.1088/0031-9155/59/20/6231] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Park MJ, Chen S, Lee TS, Fung GSK, Lodge M, Tsui BMW. Generation and Evaluation of a Simultaneous Cardiac and Respiratory Gated Rb-82 PET Simulation. IEEE NUCLEAR SCIENCE SYMPOSIUM CONFERENCE RECORD. NUCLEAR SCIENCE SYMPOSIUM 2011; 2011:3327-3330. [PMID: 26535756 PMCID: PMC4603832 DOI: 10.1109/nssmic.2011.6152601] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The goal is to generate and evaluate a simulated 4D Rb-82 PET dataset that realistically models simultaneous respiratory and cardiac motions for use to study the effects of the motions and their compensation using various gating schemes. Normal cardiac and respiratory (C&R) motions were simulated separately using the realistic 4D XCAT phantoms. The C&R motion cycles were divided into 24 and 48 equally-spaced time points, respectively. The simultaneous dual motions were modeled by 24 × 48 phantoms with different combinations of C&R motion phases. Almost noise-free projections of the heart, blood pool, lungs, liver, stomach, spleen, and the remaining body were simulated separately using the combined SimSET and GATE Monte Carlo simulation program which is 12 times faster than GATE alone. The projections were scaled and combined to simulate a typical Rb-82 myocardial perfusion (MP) PET patient study. The no gating, 6-frame respiratory gating only, 8-frame cardiac gating only, and simultaneous 6-frame respiratory and 8-frame cardiac gating schemes were applied. Each gated projection dataset was reconstructed using a 2D OS-EM without and with attenuation correction (AC) using an averaged and gated attenuation maps. The reconstructed images were evaluated in terms of artifactual non-uniformity in the MP polar map. Significant artifactual non-uniformity was found in the MP polar map over all gating scheme without AC. With AC, the artifactual decreases in both the anterior and inferior regions were reduced with respiratory gating. Cardiac motion alone did not cause significant artifactual non-uniformity. In addition, the combination of dual gating and AC using the gated attenuation map provided the most uniform MP polar map. We demonstrated the flexibility and utility of the 4D XCAT phantom set with simultaneous C&R motions. It is a powerful tool to study motion effects on MP PET studies and to evaluate C&R gating schemes, AC and quantitative 4D PET image reconstruction methods.
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Affiliation(s)
- Min Jae Park
- Division of Medical Imaging Physics, Department of Radiology, Johns Hopkins University, Baltimore, MD 21287 USA
| | - Si Chen
- Division of Medical Imaging Physics, Department of Radiology, Johns Hopkins University, Baltimore, MD 21287 USA
| | - Taek-Soo Lee
- Division of Medical Imaging Physics, Department of Radiology, Johns Hopkins University, Baltimore, MD 21287 USA
| | - George S. K. Fung
- Division of Medical Imaging Physics, Department of Radiology, Johns Hopkins University, Baltimore, MD 21287 USA
| | - Martin Lodge
- Department of Radiology, Johns Hopkins University, Baltimore, MD 21287 USA
| | - Benjamin M. W. Tsui
- Division of Medical Imaging Physics, Department of Radiology, Johns Hopkins University, Baltimore, MD 21287 USA
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Descourt P, Carlier T, Du Y, Song X, Buvat I, Frey EC, Bardies M, Tsui BMW, Visvikis D. Implementation of angular response function modeling in SPECT simulations with GATE. Phys Med Biol 2010; 55:N253-66. [PMID: 20393239 DOI: 10.1088/0031-9155/55/9/n04] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Among Monte Carlo simulation codes in medical imaging, the GATE simulation platform is widely used today given its flexibility and accuracy, despite long run times, which in SPECT simulations are mostly spent in tracking photons through the collimators. In this work, a tabulated model of the collimator/detector response was implemented within the GATE framework to significantly reduce the simulation times in SPECT. This implementation uses the angular response function (ARF) model. The performance of the implemented ARF approach has been compared to standard SPECT GATE simulations in terms of the ARF tables' accuracy, overall SPECT system performance and run times. Considering the simulation of the Siemens Symbia T SPECT system using high-energy collimators, differences of less than 1% were measured between the ARF-based and the standard GATE-based simulations, while considering the same noise level in the projections, acceleration factors of up to 180 were obtained when simulating a planar 364 keV source seen with the same SPECT system. The ARF-based and the standard GATE simulation results also agreed very well when considering a four-head SPECT simulation of a realistic Jaszczak phantom filled with iodine-131, with a resulting acceleration factor of 100. In conclusion, the implementation of an ARF-based model of collimator/detector response for SPECT simulations within GATE significantly reduces the simulation run times without compromising accuracy.
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Affiliation(s)
- P Descourt
- INSERM, U650, LaTIM, IFR SclnBioS, Université de Brest, CHU Brest, Brest, F-29200, France
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Abstract
The development of patient-specific treatment planning systems is of outmost importance in the development of radionuclide dosimetry, taking into account that quantitative three-dimensional nuclear medical imaging can be used in this regard. At present, the established method for dosimetry is based on the measurement of the biokinetics by serial gamma-camera scans, followed by calculations of the administered activity and the residence times, resulting in the radiation-absorbed doses of critical organs. However, the quantification of the activity in different organs from planar data is hampered by inaccurate attenuation and scatter correction as well as because of background and organ overlay. In contrast, dosimetry based on quantitative three-dimensional data can be more accurate and allows an individualized approach, provided that all effects that degrade the quantitative content of the images have been corrected for. In addition, inhomogeneous organ accumulation of the radionuclide can be detected and possibly taken into account. The aim of this work is to provide adequate information on internal emitter dosimetry and a state-of-the-art review of the current methodology and future trends.
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Development and validation of a Monte Carlo simulation tool for multi-pinhole SPECT. Mol Imaging Biol 2009; 12:295-304. [PMID: 19779896 DOI: 10.1007/s11307-009-0263-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2008] [Revised: 02/15/2009] [Accepted: 05/04/2009] [Indexed: 10/20/2022]
Abstract
PURPOSE In this work, we developed and validated a Monte Carlo simulation (MCS) tool for investigation and evaluation of multi-pinhole (MPH) SPECT imaging. PROCEDURES This tool was based on a combination of the SimSET and MCNP codes. Photon attenuation and scatter in the object, as well as penetration and scatter through the collimator detector, are modeled in this tool. It allows accurate and efficient simulation of MPH SPECT with focused pinhole apertures and user-specified photon energy, aperture material, and imaging geometry. The MCS method was validated by comparing the point response function (PRF), detection efficiency (DE), and image profiles obtained from point sources and phantom experiments. A prototype single-pinhole collimator and focused four- and five-pinhole collimators fitted on a small animal imager were used for the experimental validations. We have also compared computational speed among various simulation tools for MPH SPECT, including SimSET-MCNP, MCNP, SimSET-GATE, and GATE for simulating projections of a hot sphere phantom. RESULTS We found good agreement between the MCS and experimental results for PRF, DE, and image profiles, indicating the validity of the simulation method. The relative computational speeds for SimSET-MCNP, MCNP, SimSET-GATE, and GATE are 1: 2.73: 3.54: 7.34, respectively, for 120-view simulations. We also demonstrated the application of this MCS tool in small animal imaging by generating a set of low-noise MPH projection data of a 3D digital mouse whole body phantom. CONCLUSIONS The new method is useful for studying MPH collimator designs, data acquisition protocols, image reconstructions, and compensation techniques. It also has great potential to be applied for modeling the collimator-detector response with penetration and scatter effects for MPH in the quantitative reconstruction method.
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Chen CL, Wang Y, Lee JJS, Tsui BMW. Toward quantitative small animal pinhole SPECT: assessment of quantitation accuracy prior to image compensations. Mol Imaging Biol 2009; 11:195-203. [PMID: 19048346 PMCID: PMC3085830 DOI: 10.1007/s11307-008-0181-0] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2008] [Revised: 06/29/2008] [Accepted: 07/22/2008] [Indexed: 01/03/2023]
Abstract
PURPOSE We assessed the quantitation accuracy of small animal pinhole single photon emission computed tomography (SPECT) under the current preclinical settings, where image compensations are not routinely applied. PROCEDURES The effects of several common image-degrading factors and imaging parameters on quantitation accuracy were evaluated using Monte-Carlo simulation methods. Typical preclinical imaging configurations were modeled, and quantitative analyses were performed based on image reconstructions without compensating for attenuation, scatter, and limited system resolution. RESULTS Using mouse-sized phantom studies as examples, attenuation effects alone degraded quantitation accuracy by up to -18% (Tc-99m or In-111) or -41% (I-125). The inclusion of scatter effects changed the above numbers to -12% (Tc-99m or In-111) and -21% (I-125), respectively, indicating the significance of scatter in quantitative I-125 imaging. Region-of-interest (ROI) definitions have greater impacts on regional quantitation accuracy for small sphere sources as compared to attenuation and scatter effects. For the same ROI, SPECT acquisitions using pinhole apertures of different sizes could significantly affect the outcome, whereas the use of different radii-of-rotation yielded negligible differences in quantitation accuracy for the imaging configurations simulated. CONCLUSIONS We have systematically quantified the influence of several factors affecting the quantitation accuracy of small animal pinhole SPECT. In order to consistently achieve accurate quantitation within 5% of the truth, comprehensive image compensation methods are needed.
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Affiliation(s)
- Chia-Lin Chen
- Department of Medical Imaging and Radiological Sciences, Chung Shan Medical University, Taichung 402, Taiwan, Republic of China
| | - Yuchuan Wang
- Division of Medical Imaging Physics, The Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA
| | - Jason J. S. Lee
- Department of Biomedical Imaging & Radiological Sciences, National Yang-Ming University, Taipei 102, Taiwan, Republic of China
| | - Benjamin M. W. Tsui
- Division of Medical Imaging Physics, The Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA
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