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Validation of the GATE Monte-Carlo simulation platform for modelling a new semi-conductor gamma-camera dedicated to nuclear cardiology
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TOPIC: NUCLEAR MEDICINE REFRESHER COURSE 12 PET high-resolution imaging and impact on quantification M. Soret HIA Val de Grace, Paris, France Abstract not available.
TOPIC: IMAGING PROFERRED PAPERS 13 Patient exposure in TEP-CT: a national survey in France in 2011 C. Etard, D. Ce ´lier, P. Roch and B. Aubert IRSN, PRP-HOM/SER/UEM, Fontenay-aux-Roses, France As PET-CT has become a major tool in the medical care of numerous pathologies, its contribution to the medical exposure of the population has become of interest. A survey of patient doses from whole body PET-CT examinations has been conducted in France in 2011. One questionnaire was e-mailed to all the nuclear medicine departments, asking for information related both to FDG activity injected and to CT parameters. Data was received from 56 PET-CT units out of the 90 operating in France in 2011 (62%). Average injected FDG activity and specific activity were respectively equal to 300 MBq and 4.3 MBq/kg, in agreement with national DRL and European recommendations. New “time of flight” technology enabled to decrease the specific activity down to 3.5 MBq/kg. In France, CT combined to PET are “low dose CT”, only used for attenuation correction and localisation, and not for a diagnostic purpose. Consequently, the 75th percentile of the distribution of CTDIvol determined in this survey (close to 8 mGy) was by far lower than the DRL for diagnostic trunk CT (20 mGy). The 75th percentile of the distribution of PDL was close to 750 mGy.cm. Despite wide variations between PET-CT units (4-fold factor in CTDIvol), 8 mGy and 750 mGy.cm could be proposed as national DRLs respectively in terms of CTDIvol and DLP for attenuation correction whole body CT. The average effective dose related to whole body PET-CT examination in France has been assessed to about 14 mSv. Keywords: PET-CT, patient dose, DRL
14 Validation of the GATE Monte-Carlo simulation platform for modelling a new semi-conductor gammacamera dedicated to nuclear cardiology L. Imbert1,2,3,4, E. Galbrun1, S. Poussier3, D. Wolf1, G. Karcher3,4 and A. Noel1,2 1 CRAN - UMR 7039 Universite´ de Lorraine - CNRS, France, 2 Centre Alexis Vautrin, avenue de Bourgogne, Nancy, France, 3 Plateforme d’imagerie expe´rimentale Nancyclotep, France, 4 CHU de Nancy, Service de Me´decine Nucle´aire, France Introduction: Recently, significant improvements have been proposed for cameras dedicated to myocardial perfusion imaging including the use of the new cadmium-zinc-telluride (CZT) detectors and/or collimation systems. Monte-Carlo simulations are widely used in scintigraphic imaging to model imaging systems, to develop acquisition process and to assess tomographic reconstruction algorithms. GATE is the most common tool of Monte-Carlo simulations used for medical imaging in both
SFPM Annual Meeting 2012 SPECT and PET. It includes the description of the detector design, the modelling of the detector response and the physical interactions. The objective of this work is to develop a new simulation platform for modelling the first CZT gamma-camera in order to optimize the acquisition and reconstruction clinical protocols. Material and Methods: The DSPECT gamma-camera involved 9 mobile blocks of pixelated Cadmium Zinc Telluride detectors with a wide-angle square-hole tungsten collimator system. Placements and movements of each detector were simulated. The simulation model includes the detector response in terms of intrinsic spatial resolution and energy resolution. This simulation platform was evaluated by comparing simulated Tc99m point source, detection sensitivity, energy resolution and spatial resolution with the corresponding experimental measurements. Results: Results showed an excellent agreement between simulated and experimental data: detection sensitivity determined with a Tc99m point source located in air was predicted with an error less than 1%. The difference between experimental and simulated spatial resolution expressed as FWHM with a Tc99m linear source was inferior to 4% in the two directions. Finally, simulated and experimental energy resolutions were within 0,5%. These results validate this new simulation platform. Conclusions: The modelling of the DSPECT gamma-camera has been performed with the GATE code. The simulation platform was validated by comparing the simulated and experimental results. It is now possible to use this simulator to optimize acquisition and reconstruction protocols (including dual-isotope studies) and to develop the use of the DSPECT camera for other clinical applications (neurology or endocrinology). Keywords: Monte-Carlo simulations, CZT camera, Tc99m
15 Prone versus supine positioning influence on differential attenuation: Clinical impact and artifacts generation on myocardial perfusion images using a dedicated CZT semiconductor camera N. Mikail, J. Godefroy, E. Durand, P. Choquet and C. Goetz Service de biophysique et me´decine nucle´aire - UF 2061, HUS, Imagerie pre´clinique - UF 6237, HUS, Strasbourg, France Myocardial perfusion imaging (MPI) is a non invasive imaging technique routinely used both for diagnosis and follow-up of coronary artery disease (CAD). Two imaging series, are successively acquired ; the first one after a stress test, the second one at rest. Interpretation and quantification of myocardial mass at risk is based on the comparison of the radioactive tracers’ distribution. Patient positioning is a crucial issue in MPI. Positioning has to be strictly reproducible for both imaging acquisitions, as attenuation and Compton scattering related artifacts may occur, differing one from the other depending on the patient’s position, prone or supine, thus influencing interpretation. Position related artifacts have been widely described in tomoscintigraphic acquisitions with sodium iodine (NaI) detector-based cameras and parallel collimators. Two new cardiac-dedicated cameras using semiconductor technology build around cadmiumzinc-telluride (CZT) crystals have lately been available for clinical use. The first one uses multi-pinhole collimation, the second one a multi-vertical slit system. These detectors are known to be more sensitive and have a higher energy resolution, thus should help overcoming some of these artifacts. The goal of this work was to establish the relation between patient’s positioning and the occurring of physical artifacts on a dedicated CZT camera. We evaluated whether these artifacts are likely to affect the clinical interpretation of the images. In this prospective study, we included 60 patients scheduled in our unit for MPI. All of which underwent both prone and supine acquisitions, after stress test as well as at rest, with a cardiac-dedicated semiconductor camera (Discovery NM 530c, GEMS, Milwaukee, USA).
TOPIC: NUCLEAR MEDICINE REFRESHER COURSE 12 PET high-resolution imaging and impact on quantification M. Soret HIA Val de Grace, Paris, France Abstract not available.
TOPIC: IMAGING PROFERRED PAPERS 13 Patient exposure in TEP-CT: a national survey in France in 2011 C. Etard, D. Ce ´lier, P. Roch and B. Aubert IRSN, PRP-HOM/SER/UEM, Fontenay-aux-Roses, France As PET-CT has become a major tool in the medical care of numerous pathologies, its contribution to the medical exposure of the population has become of interest. A survey of patient doses from whole body PET-CT examinations has been conducted in France in 2011. One questionnaire was e-mailed to all the nuclear medicine departments, asking for information related both to FDG activity injected and to CT parameters. Data was received from 56 PET-CT units out of the 90 operating in France in 2011 (62%). Average injected FDG activity and specific activity were respectively equal to 300 MBq and 4.3 MBq/kg, in agreement with national DRL and European recommendations. New “time of flight” technology enabled to decrease the specific activity down to 3.5 MBq/kg. In France, CT combined to PET are “low dose CT”, only used for attenuation correction and localisation, and not for a diagnostic purpose. Consequently, the 75th percentile of the distribution of CTDIvol determined in this survey (close to 8 mGy) was by far lower than the DRL for diagnostic trunk CT (20 mGy). The 75th percentile of the distribution of PDL was close to 750 mGy.cm. Despite wide variations between PET-CT units (4-fold factor in CTDIvol), 8 mGy and 750 mGy.cm could be proposed as national DRLs respectively in terms of CTDIvol and DLP for attenuation correction whole body CT. The average effective dose related to whole body PET-CT examination in France has been assessed to about 14 mSv. Keywords: PET-CT, patient dose, DRL
14 Validation of the GATE Monte-Carlo simulation platform for modelling a new semi-conductor gammacamera dedicated to nuclear cardiology L. Imbert1,2,3,4, E. Galbrun1, S. Poussier3, D. Wolf1, G. Karcher3,4 and A. Noel1,2 1 CRAN - UMR 7039 Universite´ de Lorraine - CNRS, France, 2 Centre Alexis Vautrin, avenue de Bourgogne, Nancy, France, 3 Plateforme d’imagerie expe´rimentale Nancyclotep, France, 4 CHU de Nancy, Service de Me´decine Nucle´aire, France Introduction: Recently, significant improvements have been proposed for cameras dedicated to myocardial perfusion imaging including the use of the new cadmium-zinc-telluride (CZT) detectors and/or collimation systems. Monte-Carlo simulations are widely used in scintigraphic imaging to model imaging systems, to develop acquisition process and to assess tomographic reconstruction algorithms. GATE is the most common tool of Monte-Carlo simulations used for medical imaging in both
SFPM Annual Meeting 2012 SPECT and PET. It includes the description of the detector design, the modelling of the detector response and the physical interactions. The objective of this work is to develop a new simulation platform for modelling the first CZT gamma-camera in order to optimize the acquisition and reconstruction clinical protocols. Material and Methods: The DSPECT gamma-camera involved 9 mobile blocks of pixelated Cadmium Zinc Telluride detectors with a wide-angle square-hole tungsten collimator system. Placements and movements of each detector were simulated. The simulation model includes the detector response in terms of intrinsic spatial resolution and energy resolution. This simulation platform was evaluated by comparing simulated Tc99m point source, detection sensitivity, energy resolution and spatial resolution with the corresponding experimental measurements. Results: Results showed an excellent agreement between simulated and experimental data: detection sensitivity determined with a Tc99m point source located in air was predicted with an error less than 1%. The difference between experimental and simulated spatial resolution expressed as FWHM with a Tc99m linear source was inferior to 4% in the two directions. Finally, simulated and experimental energy resolutions were within 0,5%. These results validate this new simulation platform. Conclusions: The modelling of the DSPECT gamma-camera has been performed with the GATE code. The simulation platform was validated by comparing the simulated and experimental results. It is now possible to use this simulator to optimize acquisition and reconstruction protocols (including dual-isotope studies) and to develop the use of the DSPECT camera for other clinical applications (neurology or endocrinology). Keywords: Monte-Carlo simulations, CZT camera, Tc99m
15 Prone versus supine positioning influence on differential attenuation: Clinical impact and artifacts generation on myocardial perfusion images using a dedicated CZT semiconductor camera N. Mikail, J. Godefroy, E. Durand, P. Choquet and C. Goetz Service de biophysique et me´decine nucle´aire - UF 2061, HUS, Imagerie pre´clinique - UF 6237, HUS, Strasbourg, France Myocardial perfusion imaging (MPI) is a non invasive imaging technique routinely used both for diagnosis and follow-up of coronary artery disease (CAD). Two imaging series, are successively acquired ; the first one after a stress test, the second one at rest. Interpretation and quantification of myocardial mass at risk is based on the comparison of the radioactive tracers’ distribution. Patient positioning is a crucial issue in MPI. Positioning has to be strictly reproducible for both imaging acquisitions, as attenuation and Compton scattering related artifacts may occur, differing one from the other depending on the patient’s position, prone or supine, thus influencing interpretation. Position related artifacts have been widely described in tomoscintigraphic acquisitions with sodium iodine (NaI) detector-based cameras and parallel collimators. Two new cardiac-dedicated cameras using semiconductor technology build around cadmiumzinc-telluride (CZT) crystals have lately been available for clinical use. The first one uses multi-pinhole collimation, the second one a multi-vertical slit system. These detectors are known to be more sensitive and have a higher energy resolution, thus should help overcoming some of these artifacts. The goal of this work was to establish the relation between patient’s positioning and the occurring of physical artifacts on a dedicated CZT camera. We evaluated whether these artifacts are likely to affect the clinical interpretation of the images. In this prospective study, we included 60 patients scheduled in our unit for MPI. All of which underwent both prone and supine acquisitions, after stress test as well as at rest, with a cardiac-dedicated semiconductor camera (Discovery NM 530c, GEMS, Milwaukee, USA).