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Saikouk H, El Khayati N, Matrane A. Monte Carlo simulation of SPECT characterization for 223 Ra post-injection scintigraphy. Nucl Med Commun 2023; 44:959-967. [PMID: 37615528 DOI: 10.1097/mnm.0000000000001750] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/25/2023]
Abstract
OBJECTIVES 223 Ra is a promising α-emitting radionuclide for prostate cancer metastasis palliative treatment. Post-injection scintigraphy is of major importance to verify the concentration of the radiopharmaceutical in the targeted sites. Given the low activity administered to patients, the choice of acquisition parameters, including the collimator type, the energy window's width and the photopeak energy to be used, is primordial for the image quality. The purpose of our work was to select the SPECT configuration suitable for 223 Ra post-injection scintigraphy. METHODS We conducted simulation studies with a Symbia T6 Siemens SPECT-CT, available in our department. 223 Ra photons energy spectra were assessed for low energy high resolution (LEHR), medium energy (ME) and high energy (HE) collimators. Then, depending on the energy window, we calculated the scatter fraction, the sensitivity and the spatial resolution. RESULTS Scatter fraction was low for all collimators; however, the contribution of photons that scattered more than twice under the low energy photopeaks was important in the case of LEHR. Sensitivity's best values were obtained in the case of the LEHR collimator; nevertheless, the spatial resolution was very low for this collimator. The latter was best for ME and HE collimators. CONCLUSION A combination between a good sensitivity, a high spatial resolution and a low scatter fraction has been determined in the case of the ME collimator, followed by HE collimator as an alternative. To increase the image acquisition statistics with ME collimator, we recommend to use simultaneous energy windows: 20% centered at 82 keV, 20% centered at 154 keV and 20% centered at 270 keV.
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Affiliation(s)
- Hind Saikouk
- Faculty of Science, Mohammed V University in Rabat, Rabat
- Nuclear Medicine Department, Oncology and Hematology Hospital, Mohammed VI University Hospital, Marrakesh, Morocco
| | | | - Aboubakr Matrane
- Nuclear Medicine Department, Oncology and Hematology Hospital, Mohammed VI University Hospital, Marrakesh, Morocco
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Pells S, Cullen DM, Deidda D, Denis-Bacelar AM, Fenwick A, Ferreira KM, Hamilton D, Heetun W, Julyan P, Needham G, Pietras B, Price E, Scuffham J, Tipping J, Robinson AP. Quantitative validation of Monte Carlo SPECT simulation: application to a Mediso AnyScan GATE simulation. EJNMMI Phys 2023; 10:60. [PMID: 37777689 PMCID: PMC10542438 DOI: 10.1186/s40658-023-00581-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2023] [Accepted: 09/15/2023] [Indexed: 10/02/2023] Open
Abstract
BACKGROUND Monte Carlo (MC) simulations are used in nuclear medicine imaging as they provide unparalleled insight into processes that are not directly experimentally measurable, such as scatter and attenuation in an acquisition. Whilst MC is often used to provide a 'ground-truth', this is only the case if the simulation is fully validated against experimental data. This work presents a quantitative validation for a MC simulation of a single-photon emission computed tomography (SPECT) system. METHODS An MC simulation model of the Mediso AnyScan SCP SPECT system installed at the UK National Physical Laboratory was developed in the GATE (Geant4 Application for Tomographic Emission) toolkit. Components of the detector head and two collimator configurations were modelled according to technical specifications and physical measurements. Experimental detection efficiency measurements were collected for a range of energies, permitting an energy-dependent intrinsic camera efficiency correction function to be determined and applied to the simulation on an event-by-event basis. Experimental data were collected in a range of geometries with [Formula: see text]Tc for comparison to simulation. The procedure was then repeated with [Formula: see text]Lu to determine how the validation extended to another isotope and set of collimators. RESULTS The simulation's spatial resolution, sensitivity, energy spectra and the projection images were compared with experimental measurements. The simulation and experimental uncertainties were determined and propagated to all calculations, permitting the quantitative agreement between simulated and experimental SPECT acquisitions to be determined. Statistical agreement was seen in sinograms and projection images of both [Formula: see text]Tc and [Formula: see text]Lu data. Average simulated and experimental sensitivity ratios of ([Formula: see text]) were seen for emission and scatter windows of [Formula: see text]Tc, and ([Formula: see text]) and ([Formula: see text]) for the 113 and 208 keV emissions of [Formula: see text]Lu, respectively. CONCLUSIONS MC simulations will always be an approximation of a physical system and the level of agreement should be assessed. A validation method is presented to quantify the level of agreement between a simulation model and a physical SPECT system.
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Affiliation(s)
- Sophia Pells
- Department of Physics and Astronomy, The University of Manchester, Manchester, UK.
- National Physical Laboratory, Teddington, UK.
- Department of Radiology, UMass Chan Medical School, Worcester, MA, USA.
| | - David M Cullen
- Department of Physics and Astronomy, The University of Manchester, Manchester, UK
| | | | | | | | | | | | | | - Peter Julyan
- The Christie NHS Foundation Trust, Manchester, UK
| | - George Needham
- Department of Physics and Astronomy, The University of Manchester, Manchester, UK
- The Christie NHS Foundation Trust, Manchester, UK
| | - Ben Pietras
- Department of Physics and Astronomy, The University of Manchester, Manchester, UK
| | - Emlyn Price
- Department of Physics and Astronomy, The University of Manchester, Manchester, UK
| | - James Scuffham
- National Physical Laboratory, Teddington, UK
- Royal Surrey County Hospital, Guildford, UK
| | - Jill Tipping
- The Christie NHS Foundation Trust, Manchester, UK
| | - Andrew P Robinson
- Department of Physics and Astronomy, The University of Manchester, Manchester, UK
- National Physical Laboratory, Teddington, UK
- The Christie NHS Foundation Trust, Manchester, UK
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Huh Y, Yang J, Dim OU, Cui Y, Tao W, Huang Q, Gullberg GT, Seo Y. Evaluation of a variable-aperture full-ring SPECT system using large-area pixelated CZT modules: A simulation study for brain SPECT applications. Med Phys 2021; 48:2301-2314. [PMID: 33704793 DOI: 10.1002/mp.14836] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2020] [Revised: 01/28/2021] [Accepted: 03/03/2021] [Indexed: 11/09/2022] Open
Abstract
PURPOSE Single photon emission computed tomography (SPECT) scanners using cadmium zinc telluride (CZT) offer compact, lightweight, and improved imaging capability over conventional NaI(Tl)-based SPECT scanners. The main purpose in this study is to propose a full-ring SPECT system design with eight large-area CZT detectors that can be used for a broad spectrum of SPECT radiopharmaceuticals and demonstrate the performance of our system in comparison to the reference conventional NaI(Tl)-based two-head Anger cameras. METHODS A newly designed full-ring SPECT system is composed of eight large-area CZT cameras (128 mm × 179.2 mm effective area) that can be independently swiveled around their own axes of rotation independently and can have radial motion for varying aperture sizes that can be adapted to different sizes of imaging volume. Extended projection data were generated by conjoining projections of two adjacent detectors to overcome the limited field-of-view (FOV) by each CZT camera. Using Monte Carlo simulations, we evaluated this new system design with digital phantoms including a Derenzo hot rod phantom and a Zubal brain phantom. Comparison of performance metrics such as spatial resolution, sensitivity, contrast-to-noise ratio (CNR), and contrast-recovery ratio was made between our design and conventional SPECT scanners having different pixel sizes and radii of rotation (one clinically well-known type and two arbitrary types matched to our proposed CZT-SPECT geometries). RESULTS The proposed scanner could result in up to about three times faster in acquisition time over conventional scan time at same acquisition time per step. The spatial resolution improvement, or deterioration, of our proposed scanner compared to the clinical-type scanner was dependent upon the location of the point source. However, there were overall performance improvements over the three different setups of the conventional scanner particularly in volume sensitivity (approximately up to 1.7 times). Overall, we successfully reconstructed the phantom image for both 99m Tc-based perfusion and 123 I-based dopamine transporter (DaT) brain studies simulated for our new design. In particular, the striatal/background contrast-recovery ratio in 3-to-1 reference ratio was over 0.8 for the 123 I-based DaT study. CONCLUSIONS We proposed a variable-aperture full-ring SPECT system using combined pixelated CZT and energy-optimized parallel-hole collimator modules and evaluated the performance of this scanner using relevant digital phantoms and MC simulations. Our studies demonstrated the potential of our new full-ring CZT-SPECT design, showing reduced acquisition time and improved sensitivity with acceptable CNR and spatial resolution.
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Affiliation(s)
- Yoonsuk Huh
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA
| | - Jaewon Yang
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA
| | - Odera U Dim
- Department of Nonproliferation and National Security, Brookhaven National Laboratory, Upton, NY, USA
| | - Yonggang Cui
- Department of Nonproliferation and National Security, Brookhaven National Laboratory, Upton, NY, USA
| | - Weijie Tao
- Department of Nuclear Medicine, Ruijin Hospital, School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China
| | - Qiu Huang
- Department of Nuclear Medicine, Ruijin Hospital, School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China
| | - Grant T Gullberg
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA.,Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Youngho Seo
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA.,Department of Radiation Oncology, University of California, San Francisco, CA, USA.,Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.,Joint Graduate Group in Bioengineering, University of California, San Francisco, CA, USA.,Department of Nuclear Engineering, University of California, Berkeley, CA, USA
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Sarrut D, Etxebeste A, Krah N, Létang JM. Modeling complex particles phase space with GAN for Monte Carlo SPECT simulations: a proof of concept. Phys Med Biol 2021; 66:055014. [PMID: 33477121 DOI: 10.1088/1361-6560/abde9a] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
A method is proposed to model by a generative adversarial network the distribution of particles exiting a patient during Monte Carlo simulation of emission tomography imaging devices. The resulting compact neural network is then able to generate particles exiting the patient, going towards the detectors, avoiding costly particle tracking within the patient. As a proof of concept, the method is evaluated for single photon emission computed tomography (SPECT) imaging and combined with another neural network modeling the detector response function (ARF-nn). A complete rotating SPECT acquisition can be simulated with reduced computation time compared to conventional Monte Carlo simulation. It also allows the user to perform simulations with several imaging systems or parameters, which is useful for imaging system design.
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Affiliation(s)
- D Sarrut
- Université de Lyon, CREATIS, CNRS UMR5220, Inserm U1044, INSA-Lyon, Université Lyon 1, Centre Léon Bérard 69373, France
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A comparison between GATE and MCNPX for photon dose calculations in radiation protection using a male voxel phantom. Radiat Phys Chem Oxf Engl 1993 2019. [DOI: 10.1016/j.radphyschem.2018.12.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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6
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Development and validation of a full model of a four-headed neuroimaging single-photon emission computed tomography scanner. Nucl Med Commun 2019; 40:14-21. [PMID: 30371606 PMCID: PMC6282668 DOI: 10.1097/mnm.0000000000000939] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Objective The Nucline X-Ring 4R is a four-headed gamma camera dedicated to neuroimaging. In this paper, we describe and validate a GATE (Geant4 Application for Tomographic Emission) model of the Nucline X-Ring 4R. Materials and methods Images produced during model simulations were compared with those acquired experimentally to confirm the model was an accurate representation of the scanner. The most commonly reported measurements used to validate a GATE model include energy resolution, spatial resolution and sensitivity. In addition to the commonly reported static imaging measures, single-photon emission computed tomography (SPECT) spatial resolution was investigated to confirm that the model produces similar SPECT images to the experimental output. Results The experimental full-width at half-maximum was calculated to be 12.3 keV, which corresponds to an energy resolution of 8.8%. The simulated full-width at half-maximum was measured to be 12 keV, giving an energy resolution of 8.6%. The average spatial resolutions were found to be well matched (5.69 mm – simulated and 5.64 mm – experimental). However, the sensitivity was overestimated using the GATE model (47.8 and 54.3 cps/MBq) compared with the values obtained experimentally (42.7 and 44.3 cps/MBq). Finally, the simulated SPECT spatial resolution images were found to produce qualitatively comparable results. Conclusion The model developed has been shown to produce similar results and images to those obtained experimentally. This model has the potential to simulate patient scans with the aim of improving patient care by optimizing scanner protocols.
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Sarrut D, Krah N, Badel JN, Létang JM. Learning SPECT detector angular response function with neural network for accelerating Monte-Carlo simulations. ACTA ACUST UNITED AC 2018; 63:205013. [DOI: 10.1088/1361-6560/aae331] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Parach AA, Rajabi H. A comparison between GATE4 results and MCNP4B published data for internal radiation dosimetry. Nuklearmedizin 2017; 50:122-33. [DOI: 10.3413/nukmed-0363-10-10] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2010] [Accepted: 01/13/2011] [Indexed: 11/20/2022]
Abstract
SummaryAim: GATE, has been designed as upper layer of the GEANT4 toolkit for nuclear medicine application including internal dosimetry. However, its results have not been fully compared to the well-developed codes and anthropomorphic voxel phantoms have never been used with GATE/GEANT for internal dosimetry. The aim of present study was to compare the internal dose calculated by GATE/GEANT with the MCNP4B published data. Methods: The Zubal phantom was used to model a typical adult male. Activity was assumed uniformly distributed in liver, kidneys, lungs, spleen, pancreas and adrenals. GATE/ GEANT Monte Carlo package was used for estimation of doses in the phantom. Simulations were performed for photon energy of 0.01–1 MeV and mono-energetic electrons of 935 keV. Specific absorbed fractions for photons and S-factors for electrons were calculated. Results: On average, GATE/GEANT produces higher photon SAF (Specific Absorbed Fraction) values (+2.7%) for self-absorption and lower values (-2.9%) for cross-absorption. The difference was higher for paired organs particularly lungs. Moreover the photon SAF values for lungs as source organ at the energy of 200 and 500 keV was considerably higher with MCNP4B compared to GATE. Conclusion: Despite of differences between the GATE4 and MCNP4B, the results can be considered ensuring. This may be considered as validation of GATE/GEANT as a proprietary code in nuclear medicine for radionuclide dosimetry applications.
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Matsutomo N, Matsumoto S, Yamamoto T, Sato E. Validation of a calibration method using the cross-calibration factor and system planar sensitivity in quantitative single-photon emission computed tomography imaging. Radiol Phys Technol 2017; 10:439-445. [PMID: 28822095 DOI: 10.1007/s12194-017-0416-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2017] [Revised: 08/14/2017] [Accepted: 08/15/2017] [Indexed: 11/28/2022]
Abstract
The present study aimed to validate the absolute quantitative accuracy of a calibration method for single-photon emission computed tomography (SPECT) using cross-calibration factor (CCF)- and system sensitivity-based calibration methods. The CCF obtained with different reconstruction parameters was evaluated using a cylindrical phantom (diameter 20 cm, height 20 cm). SPECT images were acquired with a positron emission tomography/computed tomography (CT) phantom. Subsequently, they were reconstructed by using ordered subset expectation maximization with resolution recovery, scatter, and CT-based attenuation correction. All reconstructed SPECT counts were converted to activity concentrations based on the CCF and system planar sensitivity. We placed 12 circular regions of interest, 37 mm in diameter, on the phantom background, and the converted activity concentration and relative measurement error were assessed. The CCF obtained using a cylindrical phantom was affected by the iterative update number and post-smoothing filter function. The activity concentration calibrated using the CCF showed over- and underestimation. However, the activity concentration obtained from the system planar sensitivity was similar to that gained using the phantom. The values obtained using the system planar sensitivity were within 10% of the activity concentrations obtained with the phantom. These findings demonstrated that the calibration method using system planar sensitivity provides accurate quantification within 10% of the true activity concentration. Further clinical examination is required to validate the present results.
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Affiliation(s)
- Norikazu Matsutomo
- Department of Medical Radiological Technology, Faculty of Health Sciences, Kyorin University, 5-4-1 Shimorenjaku, Mitaka-shi, Tokyo, 181-8612, Japan.
| | - Saki Matsumoto
- Department of Radiology, Kyorin University Hospital, 6-20-2 Shinkawa, Mitaka-shi, Tokyo, 181-8611, Japan
| | - Tomoaki Yamamoto
- Department of Medical Radiological Technology, Faculty of Health Sciences, Kyorin University, 5-4-1 Shimorenjaku, Mitaka-shi, Tokyo, 181-8612, Japan
| | - Eisuke Sato
- Department of Medical Radiological Technology, Faculty of Health Sciences, Kyorin University, 5-4-1 Shimorenjaku, Mitaka-shi, Tokyo, 181-8612, Japan
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Wang B, van Roosmalen J, Piët L, van Schie MA, Beekman FJ, Goorden MC. Voxelized ray-tracing simulation dedicated to multi-pinhole molecular breast tomosynthesis. Biomed Phys Eng Express 2017. [DOI: 10.1088/2057-1976/aa8012] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
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Villoing D, Marcatili S, Garcia MP, Bardiès M. Internal dosimetry with the Monte Carlo code GATE: validation using the ICRP/ICRU female reference computational model. Phys Med Biol 2017; 62:1885-1904. [DOI: 10.1088/1361-6560/62/5/1885] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Asl RG, Parach AA, Nasseri S, Momennezhad M, Zakavi SR, Sadoughi HR. Specific Absorbed Fractions of Internal Photon and Electron Emitters in a Human Voxel-based Phantom: A Monte Carlo Study. World J Nucl Med 2017; 16:114-121. [PMID: 28553177 PMCID: PMC5436316 DOI: 10.4103/1450-1147.203065] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
The specific absorbed fraction (SAF) of energy is an essential element of internal dose assessment. Here reported a set of SAFs calculated for selected organs of a human voxel-based phantom. The Monte Carlo transport code GATE version 6.1 was used to simulate monoenergetic photons and electrons with energies ranging from 10 keV to 2 MeV. The particles were emitted from three source organs: kidneys, liver, and spleen. SAFs were calculated for three target regions in the body (kidneys, liver, and spleen) and compared with the results obtained using the MCNP4B and GATE/GEANT4 Monte Carlo codes. For most photon energies, the self-irradiation is higher, and the cross-irradiation is lower in the GATE results compared to the MCNP4B. The results show generally good agreement for photons and high-energy electrons with discrepancies within − 2% ±3%. Nevertheless, significant differences were found for cross-irradiation of photons of lower energy and electrons of higher energy due to statistical uncertainties larger than 10%. The comparisons of the SAF values for the human voxel phantom do not show significant differences, and the results also demonstrated the usefulness and applicability of GATE Monte Carlo package for voxel level dose calculations in nonuniform media. The present SAFs calculation for the Zubal voxel phantom is validated by the intercomparison of the results obtained by other Monte Carlo codes.
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Affiliation(s)
- Ruhollah Ghahraman Asl
- Bioinformatics Research Centre, Department of Nutrition and Biochemistry, Faculty of Medicine, Sabzevar University of Medical Sciences, Sabzevar, Iran
| | - Ali Asghar Parach
- Department of Medical Physics, Faculty of Medicine, Shahid Sadoughi University of Medical Sciences, Yazd, Iran
| | - Shahrokh Nasseri
- Department of Medical Physics, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Mehdi Momennezhad
- Department of Medical Physics, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Seyed Rasoul Zakavi
- Nuclear Medicine Research Center, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Hamid Reza Sadoughi
- Department of Biotechnology and Molecular Sciences, Faculty of Medicine, North Khorasan University of Medical Sciences, Bojnurd, Iran
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Karamat MI, Farncombe TH. A Comparison Between GATE and Accelerated Convolution-Based Forced Detection SIMIND for Low- and Medium-Energy Collimators: A Simulation Study. IEEE TRANSACTIONS ON RADIATION AND PLASMA MEDICAL SCIENCES 2017. [DOI: 10.1109/tns.2016.2634419] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Hou X, Tanguay J, Vuckovic M, Buckley K, Schaffer P, Bénard F, Ruth TJ, Celler A. Imaging study of using radiopharmaceuticals labeled with cyclotron-produced 99mTc. Phys Med Biol 2016; 61:8199-8213. [PMID: 27804919 DOI: 10.1088/0031-9155/61/23/8199] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Cyclotron-produced 99mTc (CPTc) has been recognized as an attractive and practical substitution of reactor/generator based 99mTc. However, the small amount of 92-98Mo in the irradiation of enriched 100Mo could lead to the production of other radioactive technetium isotopes (Tc-impurities) which cannot be chemically separated. Thus, these impurities could contribute to patient dose and affect image quality. The potential radiation dose caused by these Tc-impurities produced using different targets, irradiation conditions, and corresponding to different injection times have been investigated, leading us to create dose-based limits of these parameters for producing clinically acceptable CPTc. However, image quality has been not considered. The aim of the present work is to provide a comprehensive and quantitative analysis of image quality for CPTc. The impact of Tc-impurities in CPTc on image resolution, background noise, and contrast is investigated by performing both Monte-Carlo simulations and phantom experiments. Various targets, irradiation, and acquisition conditions are employed for investigating the image-based limits of CPTc production parameters. Additionally, the relationship between patient dose and image quality of CPTc samples is studied. Only those samples which meet both dose- and image-based limits should be accepted in future clinical studies.
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Affiliation(s)
- X Hou
- University of British Columbia, Vancouver, BC, Canada
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Garcia MP, Bert J, Benoit D, Bardiès M, Visvikis D. Accelerated GPU based SPECT Monte Carlo simulations. Phys Med Biol 2016; 61:4001-18. [DOI: 10.1088/0031-9155/61/11/4001] [Citation(s) in RCA: 13] [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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Uribe CF, Esquinas PL, Gonzalez M, Celler A. Characteristics of Bremsstrahlung emissions of (177)Lu, (188)Re, and (90)Y for SPECT/CT quantification in radionuclide therapy. Phys Med 2016; 32:691-700. [PMID: 27157626 DOI: 10.1016/j.ejmp.2016.04.014] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/19/2015] [Revised: 04/27/2016] [Accepted: 04/28/2016] [Indexed: 11/29/2022] Open
Abstract
PURPOSE Beta particles emitted by radioisotopes used in targeted radionuclide therapies (TRT) create Bremsstrahlung (BRS) which may affect SPECT quantification when imaging these isotopes. The purpose of the current study was to investigate the characteristics of Bremsstrahlung produced in tissue by three β-emitting radioisotopes used in TRT. METHODS Monte Carlo simulations of (177)Lu, (188)Re, and (90)Y sources placed in water filled cylinders were performed. BRS yields, mean energies and energy spectra for (a) all photons generated in the decays, (b) photons that were not absorbed and leave the cylinder, and (c) photons detected by the camera were analyzed. Next, the results of simulations were compared with those from experiments performed on a clinical SPECT camera using same acquisition conditions and phantom configurations as in simulations. RESULTS Simulations reproduced relatively well the shapes of the measured spectra, except for (90)Y which showed an overestimation in the low energy range. Detailed analysis of the results allowed us to suggest best collimators and imaging conditions for each of the investigated isotopes. Finally, our simulations confirmed that the BRS contribution to the energy spectra in quantitative imaging of (177)Lu and (188)Re could be ignored. CONCLUSIONS For (177)Lu and (188)Re, BRS contributes only marginally to the total spectra recorded by the camera. Our analysis shows that MELP and HE collimators are the best for imaging these two isotopes. For (90)Y, HE collimator should be used.
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Affiliation(s)
- Carlos F Uribe
- Medical Imaging Research Group, University of British Columbia, Vancouver, British Columbia, Canada; Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia, Canada.
| | - Pedro L Esquinas
- Medical Imaging Research Group, University of British Columbia, Vancouver, British Columbia, Canada; Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia, Canada
| | - Marjorie Gonzalez
- Vancouver Coastal Health Authority, Vancouver, British Columbia, Canada
| | - Anna Celler
- Medical Imaging Research Group, University of British Columbia, Vancouver, British Columbia, Canada
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Garcia MP, Villoing D, McKay E, Ferrer L, Cremonesi M, Botta F, Ferrari M, Bardiès M. TestDose: A nuclear medicine software based on Monte Carlo modeling for generating gamma camera acquisitions and dosimetry. Med Phys 2015; 42:6885-94. [DOI: 10.1118/1.4934828] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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18
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Imbert L, Galbrun E, Odille F, Poussier S, Noel A, Wolf D, Karcher G, Marie PY. Assessment of a Monte-Carlo simulation of SPECT recordings from a new-generation heart-centric semiconductor camera: from point sources to human images. Phys Med Biol 2015; 60:1007-18. [PMID: 25574814 DOI: 10.1088/0031-9155/60/3/1007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Geant4 application for tomographic emission (GATE), a Monte-Carlo simulation platform, has previously been used for optimizing tomoscintigraphic images recorded with scintillation Anger cameras but not with the new-generation heart-centric cadmium-zinc-telluride (CZT) cameras. Using the GATE platform, this study aimed at simulating the SPECT recordings from one of these new CZT cameras and to assess this simulation by direct comparison between simulated and actual recorded data, ranging from point sources to human images. Geometry and movement of detectors, as well as their respective energy responses, were modeled for the CZT 'D.SPECT' camera in the GATE platform. Both simulated and actual recorded data were obtained from: (1) point and linear sources of (99m)Tc for compared assessments of detection sensitivity and spatial resolution, (2) a cardiac insert filled with a (99m)Tc solution for compared assessments of contrast-to-noise ratio and sharpness of myocardial borders and (3) in a patient with myocardial infarction using segmented cardiac magnetic resonance imaging images. Most of the data from the simulated images exhibited high concordance with the results of actual images with relative differences of only: (1) 0.5% for detection sensitivity, (2) 6.7% for spatial resolution, (3) 2.6% for contrast-to-noise ratio and 5.0% for sharpness index on the cardiac insert placed in a diffusing environment. There was also good concordance between actual and simulated gated-SPECT patient images for the delineation of the myocardial infarction area, although the quality of the simulated images was clearly superior with increases around 50% for both contrast-to-noise ratio and sharpness index. SPECT recordings from a new heart-centric CZT camera can be simulated with the GATE software with high concordance relative to the actual physical properties of this camera. These simulations may be conducted up to the stage of human SPECT-images even if further refinement is needed in this setting.
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Affiliation(s)
- Laetitia Imbert
- CRAN, UMR 7039, Université de Lorraine-CNRS, Vandoeuvre, F-54500, France. Institut de Cancérologie de Lorraine, Department of Radiotherapy, Vandoeuvre, F-54500, France. Nancyclotep Experimental Imaging Platform, Nancy, F-54000, France. CHU Nancy, Department of Nuclear Medicine, Nancy, F-54000, France
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Popota FD, Aguiar P, España S, Lois C, Udias JM, Ros D, Pavia J, Gispert JD. Monte Carlo simulations versus experimental measurements in a small animal PET system. A comparison in the NEMA NU 4-2008 framework. Phys Med Biol 2015; 60:151-62. [PMID: 25479341 DOI: 10.1088/0031-9155/60/1/151] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
In this work a comparison between experimental and simulated data using GATE and PeneloPET Monte Carlo simulation packages is presented. All simulated setups, as well as the experimental measurements, followed exactly the guidelines of the NEMA NU 4-2008 standards using the microPET R4 scanner. The comparison was focused on spatial resolution, sensitivity, scatter fraction and counting rates performance. Both GATE and PeneloPET showed reasonable agreement for the spatial resolution when compared to experimental measurements, although they lead to slight underestimations for the points close to the edge. High accuracy was obtained between experiments and simulations of the system's sensitivity and scatter fraction for an energy window of 350-650 keV, as well as for the counting rate simulations. The latter was the most complicated test to perform since each code demands different specifications for the characterization of the system's dead time. Although simulated and experimental results were in excellent agreement for both simulation codes, PeneloPET demanded more information about the behavior of the real data acquisition system. To our knowledge, this constitutes the first validation of these Monte Carlo codes for the full NEMA NU 4-2008 standards for small animal PET imaging systems.
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Affiliation(s)
- F D Popota
- Unitat de Biofisica i Bioenginyeria, Universitat de Barcelona, Barcelona, Spain. Universidad de Pompeu Fabra, Barcelona, Spain
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Chun SY, Fessler JA, Dewaraja YK. Correction for collimator-detector response in SPECT using point spread function template. IEEE TRANSACTIONS ON MEDICAL IMAGING 2013; 32:295-305. [PMID: 23086521 PMCID: PMC3619230 DOI: 10.1109/tmi.2012.2225441] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Compensating for the collimator-detector response (CDR) in SPECT is important for accurate quantification. The CDR consists of both a geometric response and a septal penetration and collimator scatter response. The geometric response can be modeled analytically and is often used for modeling the whole CDR if the geometric response dominates. However, for radionuclides that emit medium or high-energy photons such as I-131, the septal penetration and collimator scatter response is significant and its modeling in the CDR correction is important for accurate quantification. There are two main methods for modeling the depth-dependent CDR so as to include both the geometric response and the septal penetration and collimator scatter response. One is to fit a Gaussian plus exponential function that is rotationally invariant to the measured point source response at several source-detector distances. However, a rotationally-invariant exponential function cannot represent the star-shaped septal penetration tails in detail. Another is to perform Monte-Carlo (MC) simulations to generate the depth-dependent point spread functions (PSFs) for all necessary distances. However, MC simulations, which require careful modeling of the SPECT detector components, can be challenging and accurate results may not be available for all of the different SPECT scanners in clinics. In this paper, we propose an alternative approach to CDR modeling. We use a Gaussian function plus a 2-D B-spline PSF template and fit the model to measurements of an I-131 point source at several distances. The proposed PSF-template-based approach is nearly non-parametric, captures the characteristics of the septal penetration tails, and minimizes the difference between the fitted and measured CDR at the distances of interest. The new model is applied to I-131 SPECT reconstructions of experimental phantom measurements, a patient study, and a MC patient simulation study employing the XCAT phantom. The proposed model yields up to a 16.5 and 10.8% higher recovery coefficient compared to the results with the conventional Gaussian model and the Gaussian plus exponential model, respectively.
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Affiliation(s)
- Se Young Chun
- Department of Electrical Engineering and Computer Science and Radiology, University of Michigan, Ann Arbor, MI 48109 USA
| | - Jeffrey A. Fessler
- Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI 48109 USA
| | - Yuni K. Dewaraja
- Department of Radiology, University of Michigan, Ann Arbor, MI 48109 USA
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Benhalouche S, Visvikis D, Le Maitre A, Pradier O, Boussion N. Evaluation of clinical IMRT treatment planning using the GATE Monte Carlo simulation platform for absolute and relative dose calculations. Med Phys 2013; 40:021711. [DOI: 10.1118/1.4774358] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
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Jan S, Benoit D, Becheva E, Carlier T, Cassol F, Descourt P, Frisson T, Grevillot L, Guigues L, Maigne L, Morel C, Perrot Y, Rehfeld N, Sarrut D, Schaart DR, Stute S, Pietrzyk U, Visvikis D, Zahra N, Buvat I. GATE V6: a major enhancement of the GATE simulation platform enabling modelling of CT and radiotherapy. Phys Med Biol 2011; 56:881-901. [DOI: 10.1088/0031-9155/56/4/001] [Citation(s) in RCA: 548] [Impact Index Per Article: 42.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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23
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Rault E, Staelens S, Van Holen R, De Beenhouwer J, Vandenberghe S. Accurate Monte Carlo modelling of the back compartments of SPECT cameras. Phys Med Biol 2010; 56:87-104. [DOI: 10.1088/0031-9155/56/1/006] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Alzimami KS, Sassi SA, Alkhorayef MA, Spyrou NM. Preliminary Monte Carlo study of (18)F-FDG SPECT imaging with LaBr(3):Ce Crystal-based Gamma Cameras. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2010; 2010:3089-92. [PMID: 21095741 DOI: 10.1109/iembs.2010.5626109] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The utility of (18)F-deoxyglucose ((18)F-FDG) in oncology, cardiology, and neurology has generated great interest in a more economical ways of imaging (18)F-FDG than conventional PET scanners. The main thrust of this work is to investigate the potential use of LaBr(3):Ce materials in a low-cost FDG-SPECT system compared to NaI(Tl) using GATE Monte Carlo simulation. System performance at 140 keV and 511 keV was assessed using energy spectra, system sensitivity and count rate performance. Comparison of the LaBr(3):Ce and NaI(Tl) crystal-based systems showed 4.5% and 8.9% higher system sensitivity for the LaBr(3):Ce at 140 keV and 511 keV, respectively. The LaBr(3):Ce scintillator significantly improves intrinsic count rate performance due to its fast decay time with respect to NaI(Tl). In conclusion, because LaBr(3):Ce crystal combines excellent intrinsic count rate performance with slightly increased system sensitivity, it has the potential to be used for (18)F-FDG -SPECT systems.
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Paul Segars W, Tsui BMW. MCAT to XCAT: The Evolution of 4-D Computerized Phantoms for Imaging Research: Computer models that take account of body movements promise to provide evaluation and improvement of medical imaging devices and technology. PROCEEDINGS OF THE IEEE. INSTITUTE OF ELECTRICAL AND ELECTRONICS ENGINEERS 2009; 97:1954-1968. [PMID: 26472880 PMCID: PMC4603876 DOI: 10.1109/jproc.2009.2022417] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Recent work in the development of computerized phantoms has focused on the creation of ideal "hybrid" models that seek to combine the realism of a patient-based voxelized phantom with the flexibility of a mathematical or stylized phantom. We have been leading the development of such computerized phantoms for use in medical imaging research. This paper will summarize our developments dating from the original four-dimensional (4-D) Mathematical Cardiac-Torso (MCAT) phantom, a stylized model based on geometric primitives, to the current 4-D extended Cardiac-Torso (XCAT) and Mouse Whole-Body (MOBY) phantoms, hybrid models of the human and laboratory mouse based on state-of-the-art computer graphics techniques. This paper illustrates the evolution of computerized phantoms toward more accurate models of anatomy and physiology. This evolution was catalyzed through the introduction of nonuniform rational b-spline (NURBS) and subdivision (SD) surfaces, tools widely used in computer graphics, as modeling primitives to define a more ideal hybrid phantom. With NURBS and SD surfaces as a basis, we progressed from a simple geometrically based model of the male torso (MCAT) containing only a handful of structures to detailed, whole-body models of the male and female (XCAT) anatomies (at different ages from newborn to adult), each containing more than 9000 structures. The techniques we applied for modeling the human body were similarly used in the creation of the 4-D MOBY phantom, a whole-body model for the mouse designed for small animal imaging research. From our work, we have found the NURBS and SD surface modeling techniques to be an efficient and flexible way to describe the anatomy and physiology for realistic phantoms. Based on imaging data, the surfaces can accurately model the complex organs and structures in the body, providing a level of realism comparable to that of a voxelized phantom. In addition, they are very flexible. Like stylized models, they can easily be manipulated to model anatomical variations and patient motion. With the vast improvement in realism, the phantoms developed in our lab can be combined with accurate models of the imaging process (SPECT, PET, CT, magnetic resonance imaging, and ultrasound) to generate simulated imaging data close to that from actual human or animal subjects. As such, they can provide vital tools to generate predictive imaging data from many different subjects under various scanning parameters from which to quantitatively evaluate and improve imaging devices and techniques. From the MCAT to XCAT, we will demonstrate how NURBS and SD surface modeling have resulted in a major evolutionary advance in the development of computerized phantoms for imaging research.
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Affiliation(s)
- W Paul Segars
- Carl E. Ravin Advanced Imaging Laboratories, Department of Radiology, Duke University Medical Center, Durham, NC 27706 USA ( )
| | - Benjamin M W Tsui
- Division of Medical Imaging Physics, The Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins Medical Institutions, Baltimore, MD 21287 USA ( )
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Alzimami K, Abuelhia E, Podolyak Z, Ioannou A, Spyrou NM. Characterization of LaBr3: Ce and LaCl3: Ce scintillators for gamma-ray spectroscopy. J Radioanal Nucl Chem 2008. [DOI: 10.1007/s10967-008-1606-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Chen CL, Wang Y, Lee JJS, Tsui BMW. Integration of SimSET photon history generator in GATE for efficient Monte Carlo simulations of pinhole SPECT. Med Phys 2008; 35:3278-84. [PMID: 18697552 DOI: 10.1118/1.2940159] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The authors developed and validated an efficient Monte Carlo simulation (MCS) workflow to facilitate small animal pinhole SPECT imaging research. This workflow seamlessly integrates two existing MCS tools: simulation system for emission tomography (SimSET) and GEANT4 application for emission tomography (GATE). Specifically, we retained the strength of GATE in describing complex collimator/detector configurations to meet the anticipated needs for studying advanced pinhole collimation (e.g., multipinhole) geometry, while inserting the fast SimSET photon history generator (PHG) to circumvent the relatively slow GEANT4 MCS code used by GATE in simulating photon interactions inside voxelized phantoms. For validation, data generated from this new SimSET-GATE workflow were compared with those from GATE-only simulations as well as experimental measurements obtained using a commercial small animal pinhole SPECT system. Our results showed excellent agreement (e.g., in system point response functions and energy spectra) between SimSET-GATE and GATE-only simulations, and, more importantly, a significant computational speedup (up to approximately 10-fold) provided by the new workflow. Satisfactory agreement between MCS results and experimental data were also observed. In conclusion, the authors have successfully integrated SimSET photon history generator in GATE for fast and realistic pinhole SPECT simulations, which can facilitate research in, for example, the development and application of quantitative pinhole and multipinhole SPECT for small animal imaging. This integrated simulation tool can also be adapted for studying other preclinical and clinical SPECT techniques.
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Affiliation(s)
- Chia-Lin Chen
- Department of Biomedical Imaging and Radiological Sciences, National Yang-Ming University, Taipei 102, Taiwan
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Shcherbinin S, Celler A, Belhocine T, Vanderwerf R, Driedger A. Accuracy of quantitative reconstructions in SPECT/CT imaging. Phys Med Biol 2008; 53:4595-604. [PMID: 18678930 DOI: 10.1088/0031-9155/53/17/009] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The goal of this study was to determine the quantitative accuracy of our OSEM-APDI reconstruction method based on SPECT/CT imaging for Tc-99m, In-111, I-123, and I-131 isotopes. Phantom studies were performed on a SPECT/low-dose multislice CT system (Infinia-Hawkeye-4 slice, GE Healthcare) using clinical acquisition protocols. Two radioactive sources were centrally and peripherally placed inside an anthropometric Thorax phantom filled with non-radioactive water. Corrections for attenuation, scatter, collimator blurring and collimator septal penetration were applied and their contribution to the overall accuracy of the reconstruction was evaluated. Reconstruction with the most comprehensive set of corrections resulted in activity estimation with error levels of 3-5% for all the isotopes.
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Affiliation(s)
- S Shcherbinin
- Department of Radiology, University of British Columbia, 366-828 West 10th Avenue, Vancouver BC, V5Z 1L8, Canada.
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Thiam CO, Breton V, Donnarieix D, Habib B, Maigne L. Validation of a dose deposited by low-energy photons using GATE/GEANT4. Phys Med Biol 2008; 53:3039-55. [DOI: 10.1088/0031-9155/53/11/019] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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30
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Staelens SG, de Wit TC, Lemahieu IA, Beekman FJ. Degradation of myocardial perfusion SPECT images caused by contaminants in thallous (201Tl) chloride. Eur J Nucl Med Mol Imaging 2008; 35:922-32. [DOI: 10.1007/s00259-008-0719-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2007] [Accepted: 01/04/2008] [Indexed: 11/24/2022]
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Tanaka M, Uehara S, Kojima A, Matsumoto M. Monte Carlo simulation of energy spectra for123I imaging. Phys Med Biol 2007; 52:4409-25. [PMID: 17634641 DOI: 10.1088/0031-9155/52/15/004] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
(123)I is a radionuclide frequently used in nuclear medicine imaging. The image formed by the 159 keV photopeak includes a considerable scatter component due to high energy gamma-ray emission. In order to evaluate the fraction of scattered photons, a Monte Carlo simulation of a scintillation camera used for (123)I imaging was undertaken. The Monte Carlo code consists of two modules, the HEXAGON code modelled the collimator with a complex hexagonal geometry and the NAI code modelled the NaI detector system including the back compartment. The simulation was carried out for various types of collimators under two separate conditions of the source locations in air and in water. Energy spectra of (123)I for every pixel (matrix size = 256 x 256) were obtained by separating the unscattered from the scattered and the penetrated photons. The calculated energy spectra (cps MBq(-1) keV(-1)) agreed with the measured spectra with approximately 20% deviations for three different collimators. The difference of the sensitivities (cps MBq(-1)) for the window of 143-175 keV was less than 10% between the simulation and the experiment. The partial sensitivities for the scattered and the unscattered components were obtained. The simulated fraction of the unscattered photons to the total photons were 0.46 for LEHR, 0.54 for LEGP and 0.90 for MEGP for the 'in air' set-up, and 0.35, 0.40 and 0.68 for the 'in water' set-up, respectively. The Monte Carlo simulation presented in this work enabled us to investigate the design of a new collimator optimum for (123)I scintigraphy.
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Affiliation(s)
- Minoru Tanaka
- Fukuoka University Hospital, Nanakuma 7-45-1, Jonan-ku, Fukuoka 814-0180, Japan
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Staelens S, de Wit T, Beekman F. Fast hybrid SPECT simulation including efficient septal penetration modelling (SP-PSF). Phys Med Biol 2007; 52:3027-43. [PMID: 17505087 DOI: 10.1088/0031-9155/52/11/007] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Single photon emission computed tomography (SPECT) images are degraded by the detection of scattered photons and photons that penetrate the collimator septa. In this paper, a previously proposed Monte Carlo software that employs fast object scatter simulation using convolution-based forced detection (CFD) is extended towards a wide range of medium and high energy isotopes measured using various collimators. To this end, a fast method was developed for incorporating effects of septal penetrating (SP) photons. The SP contributions are obtained by calculating the object attenuation along the path from primary emission to detection followed by sampling a pre-simulated and scalable septal penetration point spread function (SP-PSF). We found that with only a very slight reduction in accuracy, we could accelerate the SP simulation by four orders of magnitude. To achieve this, we combined: (i) coarse sampling of the activity and attenuation distribution; (ii) simulation of the penetration only for a coarse grid of detector pixels followed by interpolation and (iii) neglection of SP-PSF elements below a certain threshold. By inclusion of this SP-PSF-based simulation it became possible to model both primary and septal penetrated photons while only 10% extra computation time was added to the CFD-based Monte Carlo simulator. As a result, a SPECT simulation of a patient-like distribution including SP now takes less than 5 s per projection angle on a dual processor PC. Therefore, the simulator is well-suited as an efficient projector for fully 3D model-based reconstruction or as a fast data-set generator for applications such as image processing optimization or observer studies.
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Affiliation(s)
- Steven Staelens
- Department of Nuclear Medicine, Image Sciences Institute, University Medical Center Utrecht, Utrecht, The Netherlands.
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Després P, Funk T, Shah KS, Hasegawa BH. Monte Carlo simulations of compact gamma cameras based on avalanche photodiodes. Phys Med Biol 2007; 52:3057-74. [PMID: 17505089 DOI: 10.1088/0031-9155/52/11/009] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Avalanche photodiodes (APDs), and in particular position-sensitive avalanche photodiodes (PSAPDs), are an attractive alternative to photomultiplier tubes (PMTs) for reading out scintillators for PET and SPECT. These solid-state devices offer high gain and quantum efficiency, and can potentially lead to more compact and robust imaging systems with improved spatial and energy resolution. In order to evaluate this performance improvement, we have conducted Monte Carlo simulations of gamma cameras based on avalanche photodiodes. Specifically, we investigated the relative merit of discrete and PSAPDs in a simple continuous crystal gamma camera. The simulated camera was composed of either a 4 x 4 array of four channels 8 x 8 mm2 PSAPDs or an 8 x 8 array of 4 x 4 mm2 discrete APDs. These configurations, requiring 64 channels readout each, were used to read the scintillation light from a 6 mm thick continuous CsI:Tl crystal covering the entire 3.6 x 3.6 cm2 photodiode array. The simulations, conducted with GEANT4, accounted for the optical properties of the materials, the noise characteristics of the photodiodes and the nonlinear charge division in PSAPDs. The performance of the simulated camera was evaluated in terms of spatial resolution, energy resolution and spatial uniformity at 99mTc (140 keV) and 125I ( approximately 30 keV) energies. Intrinsic spatial resolutions of 1.0 and 0.9 mm were obtained for the APD- and PSAPD-based cameras respectively for 99mTc, and corresponding values of 1.2 and 1.3 mm FWHM for 125I. The simulations yielded maximal energy resolutions of 7% and 23% for 99mTc and 125I, respectively. PSAPDs also provided better spatial uniformity than APDs in the simple system studied. These results suggest that APDs constitute an attractive technology especially suitable to build compact, small field of view gamma cameras dedicated, for example, to small animal or organ imaging.
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Affiliation(s)
- Philippe Després
- Physics Research Laboratory, University of California, San Francisco, 185 Berry St. suite 350, San Franciso, CA 94107, USA.
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Morel C. La simulation Monte Carlo en médecine nucléaire. MEDECINE NUCLEAIRE-IMAGERIE FONCTIONNELLE ET METABOLIQUE 2007. [DOI: 10.1016/j.mednuc.2007.02.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Lazaro D, El Bitar Z, Breton V, Hill D, Buvat I. Fully 3D Monte Carlo reconstruction in SPECT: a feasibility study. Phys Med Biol 2005; 50:3739-54. [PMID: 16077224 DOI: 10.1088/0031-9155/50/16/006] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
In single photon emission computed tomography (SPECT) with parallel hole collimation, image reconstruction is usually performed as a set of bidimensional (2D) analytical or iterative reconstructions. This approach ignores the tridimensional (3D) nature of scatter and detector response function that affects the detected signal. To deal with the 3D nature of the image formation process, iterative reconstruction can be used by considering a 3D projector modelling the 3D spread of photons. In this paper, we investigate the value of using accurate Monte Carlo simulations to determine the 3D projector used in a fully 3D Monte Carlo (F3DMC) reconstruction approach. Given the 3D projector modelling all physical effects affecting the imaging process, the reconstruction problem is solved using the maximum likelihood expectation maximization (MLEM) algorithm. To validate the concept, three data sets were simulated and F3DMC was compared with two other 3D reconstruction strategies using analytical corrections for attenuation, scatter and camera point spread function. Results suggest that F3DMC improves spatial resolution, relative and absolute quantitation and signal-to-noise ratio. The practical feasibility of the approach on real data sets is discussed.
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Affiliation(s)
- D Lazaro
- UMR 678 INSERM, UPMR, CHU Pitié-Salpêtrière, 91 Boulevard de l'Hôpital, 75634 Paris Cedex 13, France
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