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Salvadori J, Merlet A, Presles B, Cabello J, Su KH, Cochet A, Etxebeste A, Vrigneaud JM, Sarrut D. PET digitization chain for Monte Carlo simulation in GATE. Phys Med Biol 2024; 69:165013. [PMID: 39009009 DOI: 10.1088/1361-6560/ad638c] [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: 04/22/2024] [Accepted: 07/15/2024] [Indexed: 07/17/2024]
Abstract
Objective. We introduce a versatile methodology for the accurate modelling of PET imaging systems via Monte Carlo simulations, using the Geant4 application for tomographic emission (GATE) platform. Accurate Monte Carlo modelling involves the incorporation of a complete analytical signal processing chain, called the digitizer in GATE, to emulate the different count rates encountered in actual positron emission tomography (PET) systems.Approach. The proposed approach consists of two steps: (1) modelling the digitizer to replicate the detection chain of real systems, covering all available parameters, whether publicly accessible or supplied by manufacturers; (2) estimating the remaining parameters, i.e. background noise level, detection efficiency, and pile-up, using optimisation techniques based on experimental single and prompt event rates. We show that this two-step optimisation reproduces the other experimental count rates (true, scatter, and random), without the need for additional adjustments. This method has been applied and validated with experimental data derived from the NEMA count losses test for three state-of-the-art SiPM-based time-of-flight (TOF)-PET systems: Philips Vereos, Siemens Biograph Vision 600 and GE Discovery MI 4-ring.Main results. The results show good agreement between experiments and simulations for the three PET systems, with absolute relative discrepancies below 3%, 6%, 6%, 7% and 12% for prompt, random, true, scatter and noise equivalent count rates, respectively, within the 0-10 kBq·ml-1activity concentration range typically observed in whole-body18F scans.Significance. Overall, the proposed digitizer optimisation method was shown to be effective in reproducing count rates and NECR for three of the latest generation SiPM-based TOF-PET imaging systems. The proposed methodology could be applied to other PET scanners.
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Affiliation(s)
- Julien Salvadori
- Groupement de Coopération Sanitaire, Institut de Cancérologie Strasbourg Europe (ICANS), Nuclear medicine, Strasbourg, France
| | - Antoine Merlet
- Institut de Chimie Moléculaire de l'Université de Bourgogne (ICMUB), UMR CNRS 6302, University of Burgundy, Dijon, France
| | - Benoit Presles
- Institut de Chimie Moléculaire de l'Université de Bourgogne (ICMUB), UMR CNRS 6302, University of Burgundy, Dijon, France
| | - Jorge Cabello
- Siemens Medical Solutions, USA, Inc., Knoxville, TN, United States of America
| | - Kuan-Hao Su
- GE Healthcare, Waukesha, WI, United States of America
| | - Alexandre Cochet
- Institut de Chimie Moléculaire de l'Université de Bourgogne (ICMUB), UMR CNRS 6302, University of Burgundy, Dijon, France
- Department of Nuclear Medicine, Georges-François Leclerc Cancer Centre, Dijon, France
| | - Ane Etxebeste
- Université de Lyon, CREATIS; CNRS UMR5220, Inserm U1044, INSA-Lyon; Université Lyon 1, Centre Léon Bérard, France
| | - Jean-Marc Vrigneaud
- Institut de Chimie Moléculaire de l'Université de Bourgogne (ICMUB), UMR CNRS 6302, University of Burgundy, Dijon, France
- Department of Nuclear Medicine, Georges-François Leclerc Cancer Centre, Dijon, France
| | - David Sarrut
- Université de Lyon, CREATIS; CNRS UMR5220, Inserm U1044, INSA-Lyon; Université Lyon 1, Centre Léon Bérard, France
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Merlet A, Presles B, Su KH, Salvadori J, Sayah F, Jozi H, Cochet A, Vrigneaud JM. Validation of a discovery MI 4-ring model according to the NEMA NU 2-2018 standards: from Monte Carlo simulations to clinical-like reconstructions. EJNMMI Phys 2024; 11:13. [PMID: 38294624 PMCID: PMC11266333 DOI: 10.1186/s40658-024-00616-4] [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: 05/15/2023] [Accepted: 01/15/2024] [Indexed: 02/01/2024] Open
Abstract
BACKGROUND We propose a comprehensive evaluation of a Discovery MI 4-ring (DMI) model, using a Monte Carlo simulator (GATE) and a clinical reconstruction software package (PET toolbox). The following performance characteristics were compared with actual measurements according to NEMA NU 2-2018 guidelines: system sensitivity, count losses and scatter fraction (SF), coincidence time resolution (CTR), spatial resolution (SR), and image quality (IQ). For SR and IQ tests, reconstruction of time-of-flight (TOF) simulated data was performed using the manufacturer's reconstruction software. RESULTS Simulated prompt, random, true, scatter and noise equivalent count rates closely matched the experimental rates with maximum relative differences of 1.6%, 5.3%, 7.8%, 6.6%, and 16.5%, respectively, in a clinical range of less than 10 kBq/mL. A 3.6% maximum relative difference was found between experimental and simulated sensitivities. The simulated spatial resolution was better than the experimental one. Simulated image quality metrics were relatively close to the experimental results. CONCLUSIONS The current model is able to reproduce the behaviour of the DMI count rates in the clinical range and generate clinical-like images with a reasonable match in terms of contrast and noise.
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Affiliation(s)
- Antoine Merlet
- Imagerie et Vision artificielle, ImViA EA 7535, University of Burgundy, Dijon, France
| | - Benoît Presles
- Institut de Chimie Moléculaire de l'Université de Bourgogne (ICMUB), UMR CNRS 6302, University of Burgundy, Dijon, France
| | | | - Julien Salvadori
- ICANS, Institut de cancérologie Strasbourg Europe, Strasbourg, France
| | - Farzam Sayah
- Department of Nuclear Medicine, Georges-François Leclerc Cancer Centre, Dijon, France
| | - Hanieh Jozi
- Department of Nuclear Medicine, Georges-François Leclerc Cancer Centre, Dijon, France
| | - Alexandre Cochet
- Institut de Chimie Moléculaire de l'Université de Bourgogne (ICMUB), UMR CNRS 6302, University of Burgundy, Dijon, France
- Department of Nuclear Medicine, Georges-François Leclerc Cancer Centre, Dijon, France
| | - Jean-Marc Vrigneaud
- Institut de Chimie Moléculaire de l'Université de Bourgogne (ICMUB), UMR CNRS 6302, University of Burgundy, Dijon, France.
- Department of Nuclear Medicine, Georges-François Leclerc Cancer Centre, Dijon, France.
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Rezaei H, Sheikhzadeh P, Ghafarian P, Zaidi H, Ay MR. Accurate modeling and performance evaluation of a total-body pet scanner using Monte Carlo simulations. Med Phys 2023; 50:6815-6827. [PMID: 37665768 DOI: 10.1002/mp.16707] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Revised: 08/22/2023] [Accepted: 08/22/2023] [Indexed: 09/06/2023] Open
Abstract
BACKGROUND The limited axial field-of-view (FOV) of conventional clinical positron emission tomography (PET) scanners (∼15 to 26 cm) allows detecting only 1% of all coincidence photons, hence limiting significantly their sensitivity. To overcome this limitation, the EXPLORER consortium developed the world's first total-body PET/CT scanner that significantly increased the sensitivity, thus enabling to decrease the scan duration or injected dose. PURPOSE The purpose of this study is to perform and validate Monte Carlo simulations of the uEXPLORER PET scanner, which can be used to devise novel conceptual designs and geometrical configurations through obtaining features that are difficult to obtain experimentally. METHODS The total-body uEXPLORER PET scanner was modeled using GATE Monte Carlo (MC) platform. The model was validated through comparison with experimental measurements of various performance parameters, including spatial resolution, sensitivity, count rate performance, and image quality, according to NEMA-NU2 2018 standards. Furthermore, the effects of the time coincidence window and maximum ring difference on the count rate and noise equivalent count rate (NECR) were evaluated. RESULTS Overall, the validation study showed that there was a good agreement between the simulation and experimental results. The differences between the simulated and experimental total sensitivity for the NEMA and extended phantoms at the center of the FOV were 2.3% and 0.0%, respectively. The difference in peak NECR was 9.9% for the NEMA phantom and 1.0% for the extended phantom. The average bias between the simulated and experimental results of the full-width-at-half maximum (FWHM) for six different positions and three directions was 0.12 mm. The simulations showed that using a variable coincidence time window based on the maximum ring difference can reduce the effect of random coincidences and improve the NECR compared to a constant time coincidence window. The NECR corresponding to 252-ring difference was 2.11 Mcps, which is larger than the NECR corresponding to 336-ring difference (2.04 Mcps). CONCLUSION The developed MC model of the uEXPLORER PET scanner was validated against experimental measurements and can be used for further assessment and design optimization of the scanner.
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Affiliation(s)
- Hadi Rezaei
- Department of Medical Physics and Biomedical Engineering, Tehran University of Medical Science, Tehran, Iran
- Research Center for Molecular and Cellular Imaging (RCMCI), Advanced Medical Technologies and Equipment Institute (AMTEI), Tehran University of Medical Sciences (TUMS), Tehran, Iran
| | - Peyman Sheikhzadeh
- Department of Medical Physics and Biomedical Engineering, Tehran University of Medical Science, Tehran, Iran
- Department of Nuclear Medicine, Imam Khomeini Hospital Complex, Tehran University of Medical Sciences, Tehran, Iran
| | - Pardis Ghafarian
- Chronic Respiratory Diseases Research Center, National Research Institute of Tuberculosis and Lung Diseases (NRITLD), Shahid Beheshti University of Medical Sciences, Tehran, Iran
- PET/CT and Cyclotron Center, Masih Daneshvari Hospital, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Habib Zaidi
- Division of Nuclear Medicine and Molecular Imaging, Geneva University Hospital, Geneva, Switzerland
- Geneva University Neurocenter, Geneva University, Geneva, Switzerland
- Department of Nuclear Medicine and Molecular Imaging, University of Groningen, University, Medical Center Groningen, Groningen, Netherlands
- Department of Nuclear Medicine, University of Southern Denmark, Odense, Denmark
| | - Mohammad Reza Ay
- Department of Medical Physics and Biomedical Engineering, Tehran University of Medical Science, Tehran, Iran
- Research Center for Molecular and Cellular Imaging (RCMCI), Advanced Medical Technologies and Equipment Institute (AMTEI), Tehran University of Medical Sciences (TUMS), Tehran, Iran
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Herald M, Nicuşan A, Wheldon TK, Seville J, Windows-Yule C. Autonomous digitizer calibration of a Monte Carlo detector model through evolutionary simulation. Sci Rep 2022; 12:19535. [PMID: 36376375 PMCID: PMC9663564 DOI: 10.1038/s41598-022-24022-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Accepted: 11/08/2022] [Indexed: 11/16/2022] Open
Abstract
Simulating the response of a radiation detector is a modelling challenge due to the stochastic nature of radiation, often complex geometries, and multi-stage signal processing. While sophisticated tools for Monte Carlo simulation have been developed for radiation transport, emulating signal processing and data loss must be accomplished using a simplified model of the electronics called the digitizer. Due to a large number of free parameters, calibrating a digitizer quickly becomes an optimisation problem. To address this, we propose a novel technique by which evolutionary algorithms calibrate a digitizer autonomously. We demonstrate this by calibrating six free parameters in a digitizer model for the ADAC Forte. The accuracy of solutions is quantified via a cost function measuring the absolute percent difference between simulated and experimental coincidence count rates across a robust characterisation data set, including three detector configurations and a range of source activities. Ultimately, this calibration produces a count rate response with 5.8% mean difference to the experiment, improving from 18.3% difference when manually calibrated. Using evolutionary algorithms for model calibration is a notable advancement because this method is novel, autonomous, fault-tolerant, and achieved through a direct comparison of simulation to reality. The software used in this work has been made freely available through a GitHub repository.
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Affiliation(s)
- Matthew Herald
- School of Chemical Engineering, University of Birmingham, Birmingham, UK.
| | - Andrei Nicuşan
- School of Chemical Engineering, University of Birmingham, Birmingham, UK
| | - Tzany Kokalova Wheldon
- School of Physics and Astronomy, University of Birmingham, Birmingham, UK
- Positron Imaging Centre, University of Birmingham, Birmingham, UK
| | - Jonathan Seville
- School of Chemical Engineering, University of Birmingham, Birmingham, UK
- Positron Imaging Centre, University of Birmingham, Birmingham, UK
| | - Christopher Windows-Yule
- School of Chemical Engineering, University of Birmingham, Birmingham, UK
- Positron Imaging Centre, University of Birmingham, Birmingham, UK
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