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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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Mikalsen LTG, Kvassheim M, Stokke C. Optimized SPECT Imaging of 224Ra α-Particle Therapy by 212Pb Photon Emissions. J Nucl Med 2023:jnumed.122.264455. [PMID: 37268424 DOI: 10.2967/jnumed.122.264455] [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: 10/07/2022] [Revised: 03/10/2023] [Indexed: 06/04/2023] Open
Abstract
In preparation for an α-particle therapy trial using 1-7 MBq of 224Ra, the feasibility of tomographic SPECT/CT imaging was of interest. The nuclide decays in 6 steps to stable 208Pb, with 212Pb as the principle photon-emitting nuclide. 212Bi and 208Tl emit high-energy photons up to 2,615 keV. A phantom study was conducted to determine the optimal acquisition and reconstruction protocol. Methods: The spheres of a body phantom were filled with a 224Ra-RaCl2 solution, and the background compartment was filled with water. Images were acquired on a SPECT/CT system. In addition, 30-min scans were acquired for 80- and 240-keV emissions, using triple-energy windows, with both medium-energy and high-energy collimators. Images were acquired at 90-95 and 29-30 kBq/mL, plus an explorative 3-min acquisition at 20 kBq/mL (using only the optimal protocol). Reconstructions were performed with attenuation correction only, attenuation plus scatter correction, 3 levels of postfiltering, and 24 levels of iterative updates. Acquisitions and reconstructions were compared using the maximum value and signal-to-scatter peak ratio for each sphere. Monte Carlo simulations were performed to examine the contributions of key emissions. Results: Secondary photons of the 2,615-keV 208Tl emission produced in the collimators make up most of the acquired energy spectrum, as revealed by Monte Carlo simulations, with only a small fraction (3%-6%) of photons in each window providing useful information for imaging. Still, decent image quality is possible at 30 kBq/mL, and nuclide concentrations are imageable down to approximately 2-5 kBq/mL. The overall best results were obtained with the 240-keV window, medium-energy collimator, attenuation and scatter correction, 30 iterations and 2 subsets, and a 12-mm gaussian postprocessing filter. However, all combinations of the applied collimators and energy windows were capable of producing adequate results, even though some failed to reconstruct the 2 smallest spheres. Conclusion: SPECT/CT imaging of 224Ra in equilibrium with daughters is possible, with sufficient image quality to provide clinical utility for the current trial of intraperitoneally administrated activity. A systematic scheme for optimization was designed to select acquisition and reconstruction settings.
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Affiliation(s)
- Lars Tore Gyland Mikalsen
- Division of Radiology and Nuclear Medicine, Oslo University Hospital, Oslo, Norway;
- Department of Life Sciences and Health, Oslo Metropolitan University, Oslo, Norway
| | - Monika Kvassheim
- Division of Radiology and Nuclear Medicine, Oslo University Hospital, Oslo, Norway
- Faculty of Medicine, University of Oslo, Oslo, Norway; and
| | - Caroline Stokke
- Division of Radiology and Nuclear Medicine, Oslo University Hospital, Oslo, Norway
- Department of Physics, University of Oslo, Oslo, Norway
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4
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Auer B, Könik A, Fromme TJ, De Beenhouwer J, Kalluri KS, Lindsay C, Furenlid LR, Kuo PH, King MA. Mesh modeling of system geometry and anatomy phantoms for realistic GATE simulations and their inclusion in SPECT reconstruction. Phys Med Biol 2023; 68:10.1088/1361-6560/acbde2. [PMID: 36808915 PMCID: PMC10073298 DOI: 10.1088/1361-6560/acbde2] [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: 06/07/2022] [Accepted: 02/21/2023] [Indexed: 02/23/2023]
Abstract
Objective.Monte-Carlo simulation studies have been essential for advancing various developments in single photon emission computed tomography (SPECT) imaging, such as system design and accurate image reconstruction. Among the simulation software available, Geant4 application for tomographic emission (GATE) is one of the most used simulation toolkits in nuclear medicine, which allows building systems and attenuation phantom geometries based on the combination of idealized volumes. However, these idealized volumes are inadequate for modeling free-form shape components of such geometries. Recent GATE versions alleviate these major limitations by allowing users to import triangulated surface meshes.Approach.In this study, we describe our mesh-based simulations of a next-generation multi-pinhole SPECT system dedicated to clinical brain imaging, called AdaptiSPECT-C. To simulate realistic imaging data, we incorporated in our simulation the XCAT phantom, which provides an advanced anatomical description of the human body. An additional challenge with the AdaptiSPECT-C geometry is that the default voxelized XCAT attenuation phantom was not usable in our simulation due to intersection of objects of dissimilar materials caused by overlap of the air containing regions of the XCAT beyond the surface of the phantom and the components of the imaging system.Main results.We validated our mesh-based modeling against the one constructed by idealized volumes for a simplified single vertex configuration of AdaptiSPECT-C through simulated projection data of123I-activity distributions. We resolved the overlap conflict by creating and incorporating a mesh-based attenuation phantom following a volume hierarchy. We then evaluated our reconstructions with attenuation and scatter correction for projections obtained from simulation consisting of mesh-based modeling of the system and the attenuation phantom for brain imaging. Our approach demonstrated similar performance as the reference scheme simulated in air for uniform and clinical-like123I-IMP brain perfusion source distributions.Significance.This work enables the simulation of complex SPECT acquisitions and reconstructions for emulating realistic imaging data close to those of actual patients.
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Affiliation(s)
- Benjamin Auer
- University of Massachusetts Chan Medical School, Department of Radiology, Worcester, MA, 01655, United States of America
- Brigham and Women's Hospital, Department of Radiology, Boston, MA, 02215, United States of America
| | - Arda Könik
- Dana-Farber Cancer Institute, Department of Imaging, Boston, MA, 02215, United States of America
| | - Timothy J Fromme
- Worcester Polytechnic Institute, Worcester, MA, 01609, United States of America
| | | | - Kesava S Kalluri
- University of Massachusetts Chan Medical School, Department of Radiology, Worcester, MA, 01655, United States of America
| | - Clifford Lindsay
- University of Massachusetts Chan Medical School, Department of Radiology, Worcester, MA, 01655, United States of America
| | - Lars R Furenlid
- James C. Wyant College of Optical Sciences, University of Arizona, Tucson, AZ 85721, , United States of America
| | - Philip H Kuo
- Department of Medical Imaging, University of Arizona, Tucson, AZ, 85724, United States of America
| | - Michael A King
- University of Massachusetts Chan Medical School, Department of Radiology, Worcester, MA, 01655, United States of America
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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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Generation of clinical 177Lu SPECT/CT images based on Monte Carlo simulation with GATE. Phys Med 2021; 85:24-31. [PMID: 33957577 DOI: 10.1016/j.ejmp.2021.04.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Revised: 03/04/2021] [Accepted: 04/06/2021] [Indexed: 12/11/2022] Open
Abstract
PURPOSE Patient-specific dosimetry in MRT relies on quantitative imaging, pharmacokinetic assessment and absorbed dose calculation. The DosiTest project was initiated to evaluate the uncertainties associated with each step of the clinical dosimetry workflow through a virtual multicentric clinical trial. This work presents the generation of simulated clinical SPECT datasets based on GATE Monte Carlo modelling with its corresponding experimental CT image, which can subsequently be processed by commercial image workstations. METHODS This study considers a therapy cycle of 6.85 GBq 177Lu-labelled DOTATATE derived from an IAEA-Coordinated Research Project (E23005) on "Dosimetry in Radiopharmaceutical therapy for personalised patient treatment". Patient images were acquired on a GE Infinia-Hawkeye 4 gamma camera using a medium energy (ME) collimator. Simulated SPECT projections were generated based on experimental time points and validated against experimental SPECT projections using flattened profiles and gamma index. The simulated projections were then incorporated into the patient SPECT/CT DICOM envelopes for processing and their reconstruction within a commercial image workstation. RESULTS Gamma index passing rate (2% - 1 pixel criteria) between 95 and 98% and average gamma between 0.28 and 0.35 among different time points revealed high similarity between simulated and experimental images. Image reconstruction of the simulated projections was successful on HERMES and Xeleris workstations, a major step forward for the initiation of a multicentric virtual clinical dosimetry trial based on simulated SPECT/CT images. CONCLUSIONS Realistic 177Lu patient SPECT projections were generated in GATE. These modelled datasets will be circulated to different clinical departments to perform dosimetry in order to assess the uncertainties in the entire dosimetric chain.
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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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8
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Morphis M, van Staden JA, du Raan H, Ljungberg M. Modelling of energy-dependent spectral resolution for SPECT Monte Carlo simulations using SIMIND. Heliyon 2021; 7:e06097. [PMID: 33659726 PMCID: PMC7892923 DOI: 10.1016/j.heliyon.2021.e06097] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2020] [Revised: 12/22/2020] [Accepted: 01/21/2021] [Indexed: 12/29/2022] Open
Abstract
PURPOSE Monte Carlo (MC) modelling techniques have been used extensively in Nuclear Medicine (NM). The theoretical energy resolution relationship ( ∝ 1 / E ), does not accurately predict the gamma camera detector response across all energies. This study aimed to validate the accuracy of an energy resolution model for the SIMIND MC simulation code emulating the Siemens Symbia T16 dual-head gamma camera. METHODS Measured intrinsic energy resolution data (full width half maximum (FWHM) values), for Ba-133, Lu-177, Am-241, Ga-67, Tc-99m, I-123, I-131 and F-18 sources in air, were used to create a fitted model of the energy response of the gamma camera. Both the fitted and theoretical models were used to simulate intrinsic and extrinsic energy spectra using three different scenarios (source in air; source in simple scatter phantom and a clinical voxel-based digital patient phantom). RESULTS The results showed the theoretical model underestimated the FWHM values at energies above 160.0 keV up to 23.5 keV. In contrast, the fitted model better predicted the measured FWHM values with differences less than 3.3 keV. The I-131 in-scatter energy spectrum simulated with the fitted model better matched the measured energy spectrum. Higher energy photopeaks, (I-123: 528.9 keV and I-131: 636.9 keV) simulated with the fitted model, more accurately resembled the measured photopeaks. The voxel-based digital patient phantom energy spectra, simulated with the fitted and theoretical models, showed the potential impact of an incorrect energy resolution model when simulating isotopes with multiple photopeaks. CONCLUSION Modelling of energy resolution with the proposed fitted model enables the SIMIND user to accurately simulate NM images. A great improvement was seen for high-energy photon emitting isotopes (e.g. I-131), as well as isotopes with multiple photopeaks (e.g. Lu-177, I-131 and Ga-67) in comparison to the theoretical model. This will result in accurate evaluation of radioactivity quantification, which is vital for dosimetric purposes.
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Affiliation(s)
- Michaella Morphis
- Department of Medical Physics, Faculty of Health Sciences, University of the Free State, Bloemfontein, South Africa
| | - Johan A. van Staden
- Department of Medical Physics, Faculty of Health Sciences, University of the Free State, Bloemfontein, South Africa
| | - Hanlie du Raan
- Department of Medical Physics, Faculty of Health Sciences, University of the Free State, Bloemfontein, South Africa
| | - Michael Ljungberg
- Department of Medical Radiation Physics, Lund University, Lund, Sweden
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Auer B, Zeraatkar N, Goding JC, Könik A, Fromme TJ, Kalluri KS, Furenlid LR, Kuo PH, King MA. Inclusion of quasi-vertex views in a brain-dedicated multi-pinhole SPECT system for improved imaging performance. Phys Med Biol 2021; 66:035007. [PMID: 33065564 PMCID: PMC9899040 DOI: 10.1088/1361-6560/abc22e] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
With brain-dedicated multi-detector systems employing pinhole apertures the usage of detectors facing the top of the patient's head (i.e. quasi-vertex (QV) views) can provide the advantage of additional viewing from close to the brain for improved detector coverage. In this paper, we report the results of simulation and reconstruction studies to investigate the impact of the QV views on the imaging performance of AdaptiSPECT-C, a brain-dedicated stationary SPECT system under development. In this design, both primary and scatter photons from regions located inferior to the brain can contribute to SPECT projections acquired by the QV views, and thus degrade AdaptiSPECT-C imaging performance. In this work, we determined the proportion, origin, and nature (i.e. primary, scatter, and multiple-scatter) of counts emitted from structures within the head and throughout the body contributing to projections from the different AdaptiSPECT-C detector rings, as well as from a true vertex view detector. We simulated phantoms used to assess different aspects of image quality (i.e. uniform activity concentration sphere, and Derenzo), as well as anthropomorphic phantoms with different count levels emulating clinical 123I activity distributions (i.e. DaTscan and perfusion). We determined that attenuation and scatter in the patient's body greatly diminish the probability of the photons emitted outside the volume of interest reaching to detectors and being recorded within the 15% photopeak energy window. In addition, we demonstrated that the inclusion of the residual of such counts in the system acquisition does not degrade visual interpretation or quantitative analysis. The addition of the QV detectors improves volumetric sensitivity, angular sampling, and spatial resolution leading to significant enhancement in image quality, especially in the striato-thalamic and superior regions of the brain. Besides, the use of QV detectors improves the recovery of clinically relevant metrics such as the striatal binding ratio and mean activity in selected cerebral structures. Our findings proving the usefulness of the QV ring for brain imaging with 123I agents can be generalized to other commonly used SPECT imaging agents labelled with isotopes, such as 99mTc and likely 111In.
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Affiliation(s)
- Benjamin Auer
- Department of Radiology, University of Massachusetts Medical School, Worcester, MA, USA, 01655
| | - Navid Zeraatkar
- Department of Radiology, University of Massachusetts Medical School, Worcester, MA, USA, 01655
| | - Justin C. Goding
- Department of Radiology, University of Massachusetts Medical School, Worcester, MA, USA, 01655
| | - Arda Könik
- Department of Imaging, Dana Farber Cancer Institute, Boston, MA, USA, 02215
| | | | - Kesava S. Kalluri
- Department of Radiology, University of Massachusetts Medical School, Worcester, MA, USA, 01655
| | - Lars R. Furenlid
- Wyant College of Optical Sciences, University of Arizona, Tucson, AZ, USA, 85721.,Department of Medical Imaging, University of Arizona, Tucson, AZ, USA, 85724
| | - Phillip H. Kuo
- Department of Medical Imaging, University of Arizona, Tucson, AZ, USA, 85724
| | - Michael A. King
- Department of Radiology, University of Massachusetts Medical School, Worcester, MA, USA, 01655
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Pastrana Orejuela CO, de Assis Coelho F, Oliveira SM, Souza SAL, Vasconcellos de Sá L, Xavier da Silva A, Torres Berdeguez MB. SPECT performance evaluation on image of Yttrium 90 - Bremsstrahlung using Monte Carlo simulation. Appl Radiat Isot 2020; 168:109456. [PMID: 33321371 DOI: 10.1016/j.apradiso.2020.109456] [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: 12/31/2019] [Revised: 09/16/2020] [Accepted: 09/30/2020] [Indexed: 11/15/2022]
Abstract
Yttrium-90 (90Y) is one of the most widely used radionuclides in Nuclear Medicine practice. However, characteristic energy of this beta emitter constitutes a difficulty for dose planning using SPECT imaging. This work aimed to study bremsstrahlung X-rays effects produced by 90Y beta particles during SPECT image acquisition using Monte Carlo code MCNPX. Several simulations were carried out to evaluate different aspects that could affect SPECT image quality, such as: collimator type, source-collimator distance and composition of each interacting material. Two configurations of 90Y sources were simulated: a point source in several spheres of different materials (soft tissue, water, articular cartilage, and bone) and dimensions with radius ranging from 1 to 20 mm; and a uniformly distributed source in a Lucite cylindrical phantom filled with water. It was evaluated the bremsstrahlung photon emission generated inside different materials; for this was considered the number photons that passing through every different sphere's surface for each radii and material. In case of cylindrical phantom filled with water, in order to obtain the energy deposited over NaI (Tl) crystal detector; there was considered Median Energy General Purpose (MEGP) and Low Energy High Resolution (LEHR) collimators. Moreover, using TMESH routine available in the MCNPX Monte Carlo code, energy distribution images according to the collimator type and the source-collimator distance were obtained. The simulation was validated by comparing with the spectral distribution of the 90Y bremsstrahlung X-rays obtained experimentally from an acrylic cylindrical phantom. Results corroborated the importance of Monte Carlo simulation method to evaluate a performance of SPECT image acquisition with 90Y. The best resolution was obtained with MEGP collimator independent of source-collimator distance.
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Affiliation(s)
| | - Francisco de Assis Coelho
- Department of Nuclear Medicine, Clementino Fraga Filho University Hospital, Federal University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
| | - Susie Medeiros Oliveira
- Department of Nuclear Medicine, Clementino Fraga Filho University Hospital, Federal University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
| | - Sergio A L Souza
- Department of Nuclear Medicine, Clementino Fraga Filho University Hospital, Federal University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
| | - Lidia Vasconcellos de Sá
- Institute of Radiation Protection and Dosimetry, Brazilian Nuclear Energy Commission, Rio de Janeiro, RJ, Brazil.
| | - Ademir Xavier da Silva
- Department of Nuclear Engineering, Federal University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
| | - Mirta B Torres Berdeguez
- Department of Nuclear Engineering, Federal University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
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Lukas M, Kluge A, Beindorff N, Brenner W. Multi-Isotope Capabilities of a Small-Animal Multi-Pinhole SPECT System. J Nucl Med 2020; 61:152-161. [PMID: 31896726 DOI: 10.2967/jnumed.119.226027] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2019] [Accepted: 06/12/2019] [Indexed: 11/16/2022] Open
Abstract
The quantitative accuracy and image quality of multi-isotope SPECT is affected by various hardware-related perturbations. The present study evaluates the simultaneous acquisition of multiple isotopes using a multiplexed multi-pinhole SPECT system, assesses the extent of different error sources, and proposes experimental procedures for its objective characterization. Methods: Phantom measurements with single-, dual- and triple-isotope combinations of 99mTc, 111In, 123I, 177Lu, and 201Tl were performed with the NanoSPECT/CTPLUS to evaluate system energy resolution, count rate performance, sensitivity, collimator penetration, hardware versus object scatter, spectral crosstalk, spatial resolution, spatial registration accuracy, image uniformity, image noise, and image quality. Results: The intrinsic detector properties were suitable for the simultaneous acquisition of up to 3 isotopes with limitations for count rates exceeding 104 kcps and γ-energies lower than 75 keV. Spectral crosstalk between isotopes was more likely mediated by hardware than by source scatter and was strongly dependent on the isotope combination. Simultaneous multi-isotope acquisitions slightly degraded spatial resolution and image uniformity for spatially superimposed but not for spatially separated activity distributions while the background noise level was increased for all multi-isotope studies. For particular isotopes, collimator penetration and x-ray fluorescence contributed a significant portion of error. Conclusion: The NanoSPECT/CTPLUS enables the simultaneous acquisition of 3 radioisotopes with high quantitative accuracy and only little loss of image quality when the activity ratio is adapted to isotope-specific count rate sensitivities and when the system calibration is performed with phantoms of appropriate size.
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Affiliation(s)
- Mathias Lukas
- Department of Nuclear Medicine, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Anne Kluge
- Department of Radiation Oncology and Radiotherapy, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Nicola Beindorff
- Berlin Experimental Radionuclide Imaging Center, Charité-Universitätsmedizin Berlin, Berlin, Germany; and
| | - Winfried Brenner
- Department of Nuclear Medicine, Charité-Universitätsmedizin Berlin, Berlin, Germany.,German Cancer Consortium, Charité Campus Berlin, Berlin, Germany
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Ramonaheng K, van Staden JA, du Raan H. Validation of a Monte Carlo modelled gamma camera for Lutetium-177 imaging. Appl Radiat Isot 2020; 163:109200. [PMID: 32561041 DOI: 10.1016/j.apradiso.2020.109200] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2019] [Revised: 02/11/2020] [Accepted: 04/08/2020] [Indexed: 10/24/2022]
Abstract
This study validated a model of the Siemens Symbia T16 dual-head SPECT/CT gamma camera created using the Monte Carlo program SIMIND for 177Lu. The validation was done by comparing experimental and simulated gamma camera performance criteria tests for the 177Lu 208 keV photopeak with a medium-energy collimator. Results showed good agreement between the experimental and simulated values. These results illustrated that SIMIND could emulate the Symbia T16 successfully and therefore, can be used with confidence to model 177Lu images.
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Affiliation(s)
- K Ramonaheng
- Department of Medical Physics, University of the Free State, PO Box 339, Bloemfontein, 9300, South Africa.
| | - J A van Staden
- Department of Medical Physics, University of the Free State, PO Box 339, Bloemfontein, 9300, South Africa
| | - H du Raan
- Department of Medical Physics, University of the Free State, PO Box 339, Bloemfontein, 9300, South Africa
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Könik A, Auer B, De Beenhouwer J, Kalluri K, Zeraatkar N, Furenlid LR, King MA. Primary, scatter, and penetration characterizations of parallel-hole and pinhole collimators for I-123 SPECT. Phys Med Biol 2019; 64:245001. [PMID: 31746783 DOI: 10.1088/1361-6560/ab58fe] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Multi-pinhole (MPH) collimators are known to provide better trade-off between sensitivity and resolution for preclinical, as well as for smaller regions in clinical SPECT imaging compared to conventional collimators. In addition to this geometric advantage, MPH plates typically offer better stopping power for penetration than the conventional collimators, which is especially relevant for I-123 imaging. The I-123 emits a series of high-energy (>300 keV, ~2.5% abundance) gamma photons in addition to the primary emission (159 keV, 83% abundance). Despite their low abundance, high-energy photons penetrate through a low-energy parallel-hole (LEHR) collimator much more readily than the 159 keV photons, resulting in large downscatter in the photopeak window. In this work, we investigate the primary, scatter, and penetration characteristics of a single pinhole collimator that is commonly used for I-123 thyroid imaging and our two MPH collimators designed for I-123 DaTscan imaging for Parkinson's Disease, in comparison to three different parallel-hole collimators through a series of experiments and Monte Carlo simulations. The simulations of a point source and a digital human phantom with DaTscan activity distribution showed that our MPH collimators provide superior count performance in terms of high primary counts, low penetration, and low scatter counts compared to the parallel-hole and single pinhole collimators. For example, total scatter, multiple scatter, and collimator penetration events for the LEHR were 2.5, 7.6 and 14 times more than that of MPH within the 15% photopeak window. The total scatter fraction for LEHR was 56% where the largest contribution came from the high-energy scatter from the back compartments (31%). For the same energy window, the total scatter for MPH was 21% with only 1% scatter from the back compartments. We therefore anticipate that using MPH collimators, higher quality reconstructions can be obtained in a substantially shorter acquisition time for I-123 DaTscan and thyroid imaging.
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Affiliation(s)
- Arda Könik
- Department of Imaging, Dana Farber Cancer Institute, Boston, MA 02215, United States of America
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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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Molecular imaging using the theranostic agent 197(m)Hg: phantom measurements and Monte Carlo simulations. EJNMMI Phys 2018; 5:15. [PMID: 30146662 PMCID: PMC6110306 DOI: 10.1186/s40658-018-0216-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2018] [Accepted: 05/04/2018] [Indexed: 12/05/2022] Open
Abstract
Background Radiomercury 197mHg and 197Hg, henceforth referred to as 197(m)Hg, is a promising theranostic radionuclide endowed with properties that allow diagnostic and therapeutic applications. The aim of this work was to investigate the capabilities of 197(m)Hg for nuclear medicine imaging. Therefore measurements were performed by using a Philips BrightView SPECT camera. Furthermore, Monte Carlo simulations using the GATE software were performed to theoretically explore the imaging contribution from the various gamma and X-ray emissions from 197(m)Hg for a commercial clinical camera with low-energy high-resolution (LEHR) and high-energy general-purpose (HEGP) collimators. We estimated the spatial resolution by using a four-quadrant bar phantom, and we evaluated the planar and tomographic images from an abdominal phantom containing three cylindrical sources of 197(m)Hg solution. Results A good accordance between measurements and simulations was found for planar and SPECT imaging. Simulations allowed the decomposition of the detected energy spectrum into photon origins. Measurements and simulations for the bar phantom revealed that for the LEHR collimator, the 6-mm pattern could be resolved, whereas for the HEGP collimator, the resolution is about 10 mm. Furthermore, we found that no significant image distortion results from high-energy photons when using the LEHR collimator. Conclusions We demonstrated the imaging capabilities of 197(m)Hg which is essential both for diagnostic applications and to determine the in vivo biodistribution for dose calculations in therapeutic applications.
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Pahlka RB, Kappadath SC, Mawlawi OR. A Monte Carlo simulation of coincidence detection and imaging of gamma-ray cascades with a scintillation camera. Biomed Phys Eng Express 2018. [DOI: 10.1088/2057-1976/aad572] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Fast GPU-based Monte Carlo code for SPECT/CT reconstructions generates improved 177Lu images. EJNMMI Phys 2018; 5:1. [PMID: 29302810 PMCID: PMC5754277 DOI: 10.1186/s40658-017-0201-8] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2017] [Accepted: 12/07/2017] [Indexed: 02/05/2023] Open
Abstract
Background Full Monte Carlo (MC)-based SPECT reconstructions have a strong potential for correcting for image degrading factors, but the reconstruction times are long. The objective of this study was to develop a highly parallel Monte Carlo code for fast, ordered subset expectation maximum (OSEM) reconstructions of SPECT/CT images. The MC code was written in the Compute Unified Device Architecture language for a computer with four graphics processing units (GPUs) (GeForce GTX Titan X, Nvidia, USA). This enabled simulations of parallel photon emissions from the voxels matrix (1283 or 2563). Each computed tomography (CT) number was converted to attenuation coefficients for photo absorption, coherent scattering, and incoherent scattering. For photon scattering, the deflection angle was determined by the differential scattering cross sections. An angular response function was developed and used to model the accepted angles for photon interaction with the crystal, and a detector scattering kernel was used for modeling the photon scattering in the detector. Predefined energy and spatial resolution kernels for the crystal were used. The MC code was implemented in the OSEM reconstruction of clinical and phantom 177Lu SPECT/CT images. The Jaszczak image quality phantom was used to evaluate the performance of the MC reconstruction in comparison with attenuated corrected (AC) OSEM reconstructions and attenuated corrected OSEM reconstructions with resolution recovery corrections (RRC). Result The performance of the MC code was 3200 million photons/s. The required number of photons emitted per voxel to obtain a sufficiently low noise level in the simulated image was 200 for a 1283 voxel matrix. With this number of emitted photons/voxel, the MC-based OSEM reconstruction with ten subsets was performed within 20 s/iteration. The images converged after around six iterations. Therefore, the reconstruction time was around 3 min. The activity recovery for the spheres in the Jaszczak phantom was clearly improved with MC-based OSEM reconstruction, e.g., the activity recovery was 88% for the largest sphere, while it was 66% for AC-OSEM and 79% for RRC-OSEM. Conclusion The GPU-based MC code generated an MC-based SPECT/CT reconstruction within a few minutes, and reconstructed patient images of 177Lu-DOTATATE treatments revealed clearly improved resolution and contrast.
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Barquero R, Garcia HP, Incio MG, Minguez P, Cardenas A, Martínez D, Lassmann M. 131I activity quantification of gamma camera planar images. Phys Med Biol 2017; 62:909-926. [PMID: 28072581 DOI: 10.1088/1361-6560/62/3/909] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
A procedure to estimate the activity in target tissues in patients during the therapeutic administration of 131I radiopharmaceutical treatment for thyroid conditions (hyperthyroidism and differentiated thyroid cancer) using a gamma camera (GC) with a high energy (HE) collimator, is proposed. Planar images are acquired for lesions of different sizes r, and at different distances d, in two HE GC systems. Defining a region of interest (ROI) on the image of size r, total counts n g are measured. Sensitivity S (cps MBq-1) in each acquisition is estimated as the product of the geometric G and the intrinsic efficiency η 0. The mean fluence of 364 keV photons arriving at the ROI per disintegration G, is calculated with the MCNPX code, simulating the entire GC and the HE collimator. Intrinsic efficiency η 0 is estimated from a calibration measurement of a plane reference source of 131I in air. Values of G and S for two GC systems-Philips Skylight and Siemens e-cam-are calculated. The total range of possible sensitivity values in thyroidal imaging in the e-cam and skylight GC measure from 7 cps MBq-1 to 35 cps MBq-1, and from 6 cps MBq-1 to 29 cps MBq-1, respectively. These sensitivity values have been verified with the SIMIND code, with good agreement between them. The results have been validated with experimental measurements in air, and in a medium with scatter and attenuation. The counts in the ROI can be produced by direct, scatter and penetration photons. The fluence value for direct photons is constant for any r and d values, but scatter and penetration photons show different values related to specific r and d values, resulting in the large sensitivity differences found. The sensitivity in thyroidal GC planar imaging is strongly dependent on uptake size, and distance from the GC. An individual value for the acquisition sensitivity of each lesion can significantly alleviate the level of uncertainty in the measurement of thyroid uptake activity for each patient.
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Affiliation(s)
- Raquel Barquero
- Medical Physics, Hospital Clínico Universitario de Valladolid, Avda. Ramón y Cajal 3, 47005 Valladolid, Spain
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Robinson AP, Tipping J, Cullen DM, Hamilton D. The influence of triple energy window scatter correction on activity quantification for1 7 7Lu molecular radiotherapy. Phys Med Biol 2016; 61:5107-27. [DOI: 10.1088/0031-9155/61/14/5107] [Citation(s) in RCA: 8] [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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20
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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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Momennezhad M, Sadeghi R, Nasseri S. Development of GATE Monte Carlo simulation for a dual-head gamma camera. Radiol Phys Technol 2012; 5:222-8. [PMID: 22588590 DOI: 10.1007/s12194-012-0157-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2011] [Revised: 04/21/2012] [Accepted: 04/25/2012] [Indexed: 11/25/2022]
Affiliation(s)
- Mehdi Momennezhad
- Nuclear Medicine Research Center, Faculty of Medicine, Imam Reza Hospital, Mashhad University of Medical Sciences, Mashhad, Iran
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Walrand S, Hesse M, Demonceau G, Pauwels S, Jamar F. Yttrium-90-labeled microsphere tracking during liver selective internal radiotherapy by bremsstrahlung pinhole SPECT: feasibility study and evaluation in an abdominal phantom. EJNMMI Res 2011; 1:32. [PMID: 22214246 PMCID: PMC3377914 DOI: 10.1186/2191-219x-1-32] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2011] [Accepted: 12/02/2011] [Indexed: 12/25/2022] Open
Abstract
BACKGROUND The purpose of the study is to evaluate whether a pinhole collimator is better adapted to bremsstrahlung single photon emission computed tomography [SPECT] than parallel-hole collimators and in the affirmative, to evaluate whether pinhole bremsstrahlung SPECT, including a simple model of the scatter inside the patient, could provide a fast dosimetry assessment in liver selective internal radiotherapy [SIRT]. MATERIALS AND METHODS Bremsstrahlung SPECT of an abdominal-shaped phantom including one cold and five hot spheres was performed using two long-bore parallel-hole collimators: a medium-energy general-purpose [MEGP] and a high-energy general-purpose [HEGP], and also using a medium-energy pinhole [MEPH] collimator. In addition, ten helical MEPH SPECTs (acquisition time 3.6 min) of a realistic liver-SIRT phantom were also acquired. RESULTS Without scatter correction for SPECT, MEPH SPECT provided a significantly better contrast recovery coefficient [CRC] than MEGP and HEGP SPECTs. The CRCs obtained with MEPH SPECT were still improved with the scatter correction and became comparable to those obtained with positron-emission tomography [PET] for the 36-, 30- (cold), 28-, and 24-mm-diameter spheres: CRC = 1.09, 0.59, 0.91, and 0.69, respectively, for SPECT and CRC = 1.07, 0.56, 0.84, and 0.63, respectively, for PET. However, MEPH SPECT gave the best CRC for the 19-mm-diameter sphere: CRC = 0.56 for SPECT and CRC = 0.01 for PET. The 3.6-min helical MEPH SPECT provided accurate and reproducible activity estimation for the liver-SIRT phantom: relative deviation = 10 ± 1%. CONCLUSION Bremsstrahlung SPECT using a pinhole collimator provided a better CRC than those obtained with parallel-hole collimators. The different designs and the better attenuating material used for the collimation (tungsten instead of lead) explain this result. Further, the addition of an analytical modeling of the scattering inside the phantom resulted in an almost fully recovered contrast. This fills the gap between the performance of90Y-PET and bremsstrahlung pinhole SPECT which is a more affordable technique and could even be used during the catheterization procedure in order to optimize the90Y activity to inject.
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Affiliation(s)
- Stephan Walrand
- Center of Nuclear Medicine, Université Catholique de Louvain, Avenue Hippocrate 10, Brussels, 1200, Belgium.
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Sohlberg AO, Kajaste MT. Fast Monte Carlo-simulator with full collimator and detector response modelling for SPECT. Ann Nucl Med 2011; 26:92-8. [PMID: 22033783 DOI: 10.1007/s12149-011-0550-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2011] [Accepted: 10/13/2011] [Indexed: 10/16/2022]
Abstract
OBJECTIVE Monte Carlo (MC)-simulations have proved to be a valuable tool in studying SPECT-reconstruction algorithms. Despite their popularity, the use of Monte Carlo-simulations is still often limited by their large computation demand. This is especially true in situations where full collimator and detector modelling with septal penetration, scatter and X-ray fluorescence needs to be included. This paper presents a rapid and simple MC-simulator, which can effectively reduce the computation times. METHODS The simulator was built on the convolution-based forced detection principle, which can markedly lower the number of simulated photons. Full collimator and detector response look-up tables are pre-simulated and then later used in the actual MC-simulations to model the system response. The developed simulator was validated by comparing it against (123)I point source measurements made with a clinical gamma camera system and against (99m)Tc software phantom simulations made with the SIMIND MC-package. RESULTS The results showed good agreement between the new simulator, measurements and the SIMIND-package. The new simulator provided near noise-free projection data in approximately 1.5 min per projection with (99m)Tc, which was less than one-tenth of SIMIND's time. CONCLUSION The developed MC-simulator can markedly decrease the simulation time without sacrificing image quality.
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Affiliation(s)
- Antti O Sohlberg
- Department of Clinical Physiology and Nuclear Medicine, Joint Authority for Päijät-Häme Social and Health Care, Lahti, Finland.
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