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Monte carlo simulation of a 6 MV varian LINAC photon beam using GEANT4-GATE code
Abstracts / Physica Medica 32 (2016) 284–339
A RETROSPECTIVE STUDY FOR OCCUPATIONAL EFFECTIVE DOSES AMONGST AND WITHIN EMPLOYEES OF A NUCLEAR MEDICINE DEPARTMENT Psarouli Efthymia Medical Physics Dept., Ippokratio General Hospital of Thessaloniki, Greece Routine monitoring of occupational radiation exposure is done primarily to demonstrate compliance with dose limits. Analysis of past and present dose records provides a useful tool in the management of institutional radiation safety programs. In this study, an analysis of annual dose records from 1995 to 2015 is performed with the data from a nuclear medicine department where both radionuclide treatment and diagnostic imaging are done at a large scale. All radiation employees in the department were educated on their own subjects and experienced in their duties. They have been receiving periodic trainings about radiation protection. In this way, the annual effective dose values are limited to the minimum. Large variation in the mean annual dose exists among the different occupational groups. Among the workers, technologists received the largest annual effective dose. The study evaluates differences in occupational exposure within this group of workers performing the same procedure, and the efficacy of safety protocols. Continuing education and optimization of working technics can help minimize the radiation exposure of the workers. Limits can be assured to remain well below the acceptable values by incorporating the mechanism of job rotations. http://dx.doi.org/10.1016/j.ejmp.2016.07.243
PATIENT SPECIFIC PLAN VERIFICATION OF A VMAT PLAN USING 3D POLYMER GEL DOSIMETER IN A PHANTOM REPRODUCING PATIENT ANATOMY P. Karaiskos a,*, G. Kollias a, E. Koutsouveli a, C. Paraskevopoulou a, T.G. Maris b, T. Boursianis b, E. Pappas c a
Medical Physics Department, Hygeia Hospital, Athens, Greece Medical Physics Department, University of Crete, Heraklion, Greece c Medical Radiologic Technology Department, Technological Educational Institute of Athens, Greece ⇑ Corresponding author. b
Introduction. Patient specific plan verification becomes necessary in the advent of complex treatment delivery options with current linear accelerator technology. Purpose. To use a patient-specific end-to-end quality assurance approach for plan verification and overall accuracy evaluation of a Volumetric Modulated Arc Therapy (VMAT) irradiation. Materials and methods. Patient CT-scans were used to construct a phantom reproducing the patient anatomy in terms of external surface and bone structures using 3D-printing technology. The phantom was filled with a polymer-gel dosimeter and utilized to accurately reproduce every link in the treatment chain and irradiated using a 6 MV flattening filter free (fff) Elekta Versa linear accelerator. Upon irradiation, the phantom was MRI-scanned using a specially designed T2 pulse sequence and T2-maps were converted to 3D relative dose measurements. MR-images were imported to Monaco-TPS and co-registered to patient CT-images. TPS dose calculations were exported and used for dose comparison with measurements in an independent software. Results. Radiation-induced polymerization area was clearly evident in the T2-images and found to coincide to the high-dose target area while organs at risk (OARs) were adequately spared in
333
agreement with the TPS dose distribution. In addition, a quantitative evaluation was performed by comparing measured and TPScalculated 3D dose-maps in terms of dose distributions, gamma index maps and Dose Volume Histogram (DVH) indices clinically used for plan evaluation and acceptance. Conclusion. A patient-specific plan verification method offering the unique characteristic of providing 3D-dose distribution measurements in patient anatomy, including DVHs was implemented and revealed accurate delivery of the VMAT plan. http://dx.doi.org/10.1016/j.ejmp.2016.07.244
MONTE CARLO SIMULATION OF A 6 MV VARIAN LINAC PHOTON BEAM USING GEANT4-GATE CODE P. Gonias a,*, P. Zaverdinos b, G. Loudos c, C. Kappas a, K. Theodorou a a
Medical Physics Department, Medical School, University of Thessaly, Biopolis 41110 Larissa, Greece b Medical Physics Department, Metropolitan Hospital, Athens, Greece c Department of Medical Instruments Technology, Technological Educational Institute of Athens, Athens 12210, Greece ⇑ Corresponding author. Introduction. Monte Carlo simulation of radiation transport is considered to be one of the most accurate methods of radiation therapy dose calculation. Various codes have been used during the years and have been validated for clinical photon beams. GEANT4 Monte Carlo simulation code is originally created for high energy physics and GATE package for the simulation of SPECT/PET systems. New platform of GATE incorporate simulation processes for clinical photon beams by linear accelerators. Purpose. The aim of this work is the validation of a GEANT4-based GATE Monte Carlo (MC) 6 MV photon beam delivered by a medical linear accelerator. Materials and methods. The head of the medical linear accelerator (VARIAN CLINAC 23 EX) of the Metropolitan Hospital was simulated based on the manufacturer’s detailed information using the Gate v.7.0 GEANT4 MC code. Two-phase simulation process has been followed: calculation of the phase space (PH) from the linac head and PH transport to a water phantom. The results were compared with measured PDD and OAR data for different field sizes and the simulated model was validated. Results. The simulated and measured dose distributions were in good agreement, in the order of 1%. The statistical relative uncertainty was below of 0.6% for a 10 10 cm2 field in all dosels. Gamma index comparisons were performed: more than 90% simulated points passed the clinical 3%/3 mm gamma criterion. Discussion and Conclusion. The GATE v.7.0 Monte Carlo simulation code has been validated for 6 MV photon beam of a VARIAN medical linear accelerator. http://dx.doi.org/10.1016/j.ejmp.2016.07.245
FRACTAL DIMENSION AND LACUNARITY OF TRACTOGRAPHY IMAGES OF THE HUMAN BRAIN A. Provata a, P. Katsaloulis a, J. Hizanidi a, D.A. Verganelakis b,* a
Institute of Physical Chemistry, NCSR Demokritos, Athens, Greece Encephalos-Euromedica Medical Diagnostic Center, Athens, Greece ⇑ Corresponding author. b
Introduction. Diffusion Tensor Imaging (DTI) is a novel technique that mirrors the complex architecture of the neuron axons fiber networks in the human brain.
A RETROSPECTIVE STUDY FOR OCCUPATIONAL EFFECTIVE DOSES AMONGST AND WITHIN EMPLOYEES OF A NUCLEAR MEDICINE DEPARTMENT Psarouli Efthymia Medical Physics Dept., Ippokratio General Hospital of Thessaloniki, Greece Routine monitoring of occupational radiation exposure is done primarily to demonstrate compliance with dose limits. Analysis of past and present dose records provides a useful tool in the management of institutional radiation safety programs. In this study, an analysis of annual dose records from 1995 to 2015 is performed with the data from a nuclear medicine department where both radionuclide treatment and diagnostic imaging are done at a large scale. All radiation employees in the department were educated on their own subjects and experienced in their duties. They have been receiving periodic trainings about radiation protection. In this way, the annual effective dose values are limited to the minimum. Large variation in the mean annual dose exists among the different occupational groups. Among the workers, technologists received the largest annual effective dose. The study evaluates differences in occupational exposure within this group of workers performing the same procedure, and the efficacy of safety protocols. Continuing education and optimization of working technics can help minimize the radiation exposure of the workers. Limits can be assured to remain well below the acceptable values by incorporating the mechanism of job rotations. http://dx.doi.org/10.1016/j.ejmp.2016.07.243
PATIENT SPECIFIC PLAN VERIFICATION OF A VMAT PLAN USING 3D POLYMER GEL DOSIMETER IN A PHANTOM REPRODUCING PATIENT ANATOMY P. Karaiskos a,*, G. Kollias a, E. Koutsouveli a, C. Paraskevopoulou a, T.G. Maris b, T. Boursianis b, E. Pappas c a
Medical Physics Department, Hygeia Hospital, Athens, Greece Medical Physics Department, University of Crete, Heraklion, Greece c Medical Radiologic Technology Department, Technological Educational Institute of Athens, Greece ⇑ Corresponding author. b
Introduction. Patient specific plan verification becomes necessary in the advent of complex treatment delivery options with current linear accelerator technology. Purpose. To use a patient-specific end-to-end quality assurance approach for plan verification and overall accuracy evaluation of a Volumetric Modulated Arc Therapy (VMAT) irradiation. Materials and methods. Patient CT-scans were used to construct a phantom reproducing the patient anatomy in terms of external surface and bone structures using 3D-printing technology. The phantom was filled with a polymer-gel dosimeter and utilized to accurately reproduce every link in the treatment chain and irradiated using a 6 MV flattening filter free (fff) Elekta Versa linear accelerator. Upon irradiation, the phantom was MRI-scanned using a specially designed T2 pulse sequence and T2-maps were converted to 3D relative dose measurements. MR-images were imported to Monaco-TPS and co-registered to patient CT-images. TPS dose calculations were exported and used for dose comparison with measurements in an independent software. Results. Radiation-induced polymerization area was clearly evident in the T2-images and found to coincide to the high-dose target area while organs at risk (OARs) were adequately spared in
333
agreement with the TPS dose distribution. In addition, a quantitative evaluation was performed by comparing measured and TPScalculated 3D dose-maps in terms of dose distributions, gamma index maps and Dose Volume Histogram (DVH) indices clinically used for plan evaluation and acceptance. Conclusion. A patient-specific plan verification method offering the unique characteristic of providing 3D-dose distribution measurements in patient anatomy, including DVHs was implemented and revealed accurate delivery of the VMAT plan. http://dx.doi.org/10.1016/j.ejmp.2016.07.244
MONTE CARLO SIMULATION OF A 6 MV VARIAN LINAC PHOTON BEAM USING GEANT4-GATE CODE P. Gonias a,*, P. Zaverdinos b, G. Loudos c, C. Kappas a, K. Theodorou a a
Medical Physics Department, Medical School, University of Thessaly, Biopolis 41110 Larissa, Greece b Medical Physics Department, Metropolitan Hospital, Athens, Greece c Department of Medical Instruments Technology, Technological Educational Institute of Athens, Athens 12210, Greece ⇑ Corresponding author. Introduction. Monte Carlo simulation of radiation transport is considered to be one of the most accurate methods of radiation therapy dose calculation. Various codes have been used during the years and have been validated for clinical photon beams. GEANT4 Monte Carlo simulation code is originally created for high energy physics and GATE package for the simulation of SPECT/PET systems. New platform of GATE incorporate simulation processes for clinical photon beams by linear accelerators. Purpose. The aim of this work is the validation of a GEANT4-based GATE Monte Carlo (MC) 6 MV photon beam delivered by a medical linear accelerator. Materials and methods. The head of the medical linear accelerator (VARIAN CLINAC 23 EX) of the Metropolitan Hospital was simulated based on the manufacturer’s detailed information using the Gate v.7.0 GEANT4 MC code. Two-phase simulation process has been followed: calculation of the phase space (PH) from the linac head and PH transport to a water phantom. The results were compared with measured PDD and OAR data for different field sizes and the simulated model was validated. Results. The simulated and measured dose distributions were in good agreement, in the order of 1%. The statistical relative uncertainty was below of 0.6% for a 10 10 cm2 field in all dosels. Gamma index comparisons were performed: more than 90% simulated points passed the clinical 3%/3 mm gamma criterion. Discussion and Conclusion. The GATE v.7.0 Monte Carlo simulation code has been validated for 6 MV photon beam of a VARIAN medical linear accelerator. http://dx.doi.org/10.1016/j.ejmp.2016.07.245
FRACTAL DIMENSION AND LACUNARITY OF TRACTOGRAPHY IMAGES OF THE HUMAN BRAIN A. Provata a, P. Katsaloulis a, J. Hizanidi a, D.A. Verganelakis b,* a
Institute of Physical Chemistry, NCSR Demokritos, Athens, Greece Encephalos-Euromedica Medical Diagnostic Center, Athens, Greece ⇑ Corresponding author. b
Introduction. Diffusion Tensor Imaging (DTI) is a novel technique that mirrors the complex architecture of the neuron axons fiber networks in the human brain.