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Abstract ID: 201 Code sharing of MC beam models for advanced radiotherapy.
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Abstracts / Physica Medica 42 (2017) 1–50
Significant variations in tumor control probability (TCP) have been reported according to differences found at dose calculations between treatment planning system (TPS) and Monte Carlo (MC) method [1]. Our purpose is to quantify dosimetric and radiobiological effects due to divergences between dose distributions calculated by Pinnacle3 TPS (version 9.8) and Geant4 toolkit (version 10.01.p01) [2,3] for lung cancer cases treated with photons. Three clinical cases with 6 MV photon beams and conventional fractionation were analysed. These cases are distinguished by their tumoral size and localization. From dose distributions calculated through Geant4 and TPS we have obtained conformity index (CI) and homogeneity index (HI) [4]. The TCP was achieved using LQ model [5] with an alpha–beta ratio of 10 Gy and a density of clonogenic cells of 107 cells/cm3. For each clinical case the TCP values according to Geant4 calculations against Pinnacle calculations were 93.77 vs 97.74, 92.95 vs 92.79 and 98.31 vs 99.03 respectively. These deviations achieve a maximum value close to 4% and they are in agreement with the CI and HI values obtained in every single treatment. We have verified lung cancer treatments through Geant4 toolkit and we have found more heterogeneous dose distributions and variations in TCP up to 4% with respect to TPS calculations. These discrepancies are due to incomplete modeling in the TPS algorithm of patient tissue heterogeneities and photon fluences used in modulated beam techniques. A further study including more sophisticated radiobiology models and hypofractionated radiotherapy schemes will be subject of further work.
References 1. Chetty IJ et al. Correlation of dose computed using different algorithms with local control following stereotactic ablative radiotherapy (SABR)-based treatment of non-small-cell lung cancer. Radiother Oncol 2013;109(3):498–504. 2. Agostinelli S et al. Geant4-a simulation toolkit. Nucl Instrum Meth A 2003;506(3):250–303. 3. Allison J et al. Recent developments in Geant4. Nucl Instrum Meth A 2016;835:186–225. 4. ICRU Report 83. Prescribing, recording, and reporting intensitymodulated photon- beam therapy (IMRT). 2010. . 5. Fowler JF. The linear-quadratic formula and progress in fractionated radiotherapy. Br J Radiol 1989;62(740):679–94. http://dx.doi.org/10.1016/j.ejmp.2017.09.107
Abstract ID: 201 Code sharing of MC beam models for advanced radiotherapy. Tony Price a,*, Andrea Gutierrez b, Costanza Panaino c, Martin Turner d, Hywel Owen e a University of Birmingham, School of Physics and Astronomy, Birmingham, United Kingdom b University College London, Department of Medical Physics and Biomedical Engineering, London, United Kingdom c University of Manchester, Division of Molecular and Clinical Cancer Sciences, Faculty of Biology, Medicine and Health, Manchester, United Kingdom d Scientific Computing Department, STFC, United Kingdom e University of Manchester, School of Physics and Astronomy, Manchester, United Kingdom ⇑ Presenting author.
The development and validation of a beam line MC model is an essential part of many projects, particularly those involving particle
therapy. This is often a very time consuming and sometimes costly computational process. However, many experiments use the same beam lines and the medical physics community would benefit greatly from a structured code and data sharing site. A new project [1], funded through the STFC Global Challenge Network+ in Advanced Radiotherapy [2], aims to collate, host, validate experimentally, and disseminate common Geant4 beam line models. We will present an overview of the aims of the project, and details of how to gain access to these structured models; a structured model includes both code and data with related information on use and best practice. To illustrate this, three validation results will be shown; the iThemba LABS proton therapy centre in Cape Town (South Africa), the medical beam line of the University of Birmingham MC40 Cyclotron (United Kingdom), and ongoing work with multiple models of the Clatterbridge Cancer Centre proton eye therapy beam line (United Kingdom). We aim to develop these models in TOPAS/GATE to facilitate their use for non Geant4/C++ experts, for example, medical physicists working in hospitals. A status report of this final step will be provided.
References 1. https://trello.com/b/paBx8sJZ/shared-data. . 2. https://www.advanced-radiotherapy.ac.uk. http://dx.doi.org/10.1016/j.ejmp.2017.09.108
Abstract ID: 203 Breast model validation for Monte Carlo evaluation of normalized glandular dose coefficients in mammography A. Sarno a,b,*, G. Mettivier a,b, F. Di Lillo a,b, K. Bliznakova c, I. Sechopoulos d,e, P. Russo a,b a Università di Napoli Federico II, Dipartimento di Fisica ‘‘Ettore Pancini”, Via Cintia, I-80126 Napoli, Italy b INFN Sezione di Napoli, Via Cintia, I-80126 Napoli, Italy c Department of Electronics, Technical University of Varna, 1 Studentska Str, Varna 9010, Bulgaria d Dutch reference centre for screening (LRCB), PO Box 6873, 6503 GJ Nijmegen, The Netherlands e Department of Radiology and Nuclear Medicine, Radboud University Medical Centre, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands ⇑ Presenting author.
In Monte Carlo simulations for estimation of normalized glandular dose coefficients (i.e. the ratio between the mean glandular dose (MGD) and incident air kerma at the breast upper surface), the radiosensitive breast tissue is modelled as a homogeneous mixture of adipose and glandular tissue. However, such an assumption has been shown to lead to an overestimation in MGD by an average of 30% [1,2]. This work aimed at comparing the homogeneous breast models proposed by different authors and in different quality assurance protocols to patient specific breast phantoms. To obtain these phantoms, uncompressed breast images were acquired with a CT scanner dedicated to the breast and segmented to classify each voxel into 4 categories: air, skin tissue, adipose tissue and glandular tissue. Then the compression which breasts undergo during a mammography exams was simulated via software in order to obtain 3D compressed patient specific breast phantoms which present an heterogeneous glandular distribution similar to that of the irradiated breast. The homogeneous breast phantom was simulated either with a 4-mm skin thickness (as adopted in the USA protocol), or with a 5mm adipose layer simulating the skin and the subcutaneous adipose layer (as adopted in the EU protocol) or with a skin thickness of 1.45 mm (i.e. the skin thickness estimated from 3D breast images).
Abstracts / Physica Medica 42 (2017) 1–50
Significant variations in tumor control probability (TCP) have been reported according to differences found at dose calculations between treatment planning system (TPS) and Monte Carlo (MC) method [1]. Our purpose is to quantify dosimetric and radiobiological effects due to divergences between dose distributions calculated by Pinnacle3 TPS (version 9.8) and Geant4 toolkit (version 10.01.p01) [2,3] for lung cancer cases treated with photons. Three clinical cases with 6 MV photon beams and conventional fractionation were analysed. These cases are distinguished by their tumoral size and localization. From dose distributions calculated through Geant4 and TPS we have obtained conformity index (CI) and homogeneity index (HI) [4]. The TCP was achieved using LQ model [5] with an alpha–beta ratio of 10 Gy and a density of clonogenic cells of 107 cells/cm3. For each clinical case the TCP values according to Geant4 calculations against Pinnacle calculations were 93.77 vs 97.74, 92.95 vs 92.79 and 98.31 vs 99.03 respectively. These deviations achieve a maximum value close to 4% and they are in agreement with the CI and HI values obtained in every single treatment. We have verified lung cancer treatments through Geant4 toolkit and we have found more heterogeneous dose distributions and variations in TCP up to 4% with respect to TPS calculations. These discrepancies are due to incomplete modeling in the TPS algorithm of patient tissue heterogeneities and photon fluences used in modulated beam techniques. A further study including more sophisticated radiobiology models and hypofractionated radiotherapy schemes will be subject of further work.
References 1. Chetty IJ et al. Correlation of dose computed using different algorithms with local control following stereotactic ablative radiotherapy (SABR)-based treatment of non-small-cell lung cancer. Radiother Oncol 2013;109(3):498–504. 2. Agostinelli S et al. Geant4-a simulation toolkit. Nucl Instrum Meth A 2003;506(3):250–303. 3. Allison J et al. Recent developments in Geant4. Nucl Instrum Meth A 2016;835:186–225. 4. ICRU Report 83. Prescribing, recording, and reporting intensitymodulated photon- beam therapy (IMRT). 2010. . 5. Fowler JF. The linear-quadratic formula and progress in fractionated radiotherapy. Br J Radiol 1989;62(740):679–94. http://dx.doi.org/10.1016/j.ejmp.2017.09.107
Abstract ID: 201 Code sharing of MC beam models for advanced radiotherapy. Tony Price a,*, Andrea Gutierrez b, Costanza Panaino c, Martin Turner d, Hywel Owen e a University of Birmingham, School of Physics and Astronomy, Birmingham, United Kingdom b University College London, Department of Medical Physics and Biomedical Engineering, London, United Kingdom c University of Manchester, Division of Molecular and Clinical Cancer Sciences, Faculty of Biology, Medicine and Health, Manchester, United Kingdom d Scientific Computing Department, STFC, United Kingdom e University of Manchester, School of Physics and Astronomy, Manchester, United Kingdom ⇑ Presenting author.
The development and validation of a beam line MC model is an essential part of many projects, particularly those involving particle
therapy. This is often a very time consuming and sometimes costly computational process. However, many experiments use the same beam lines and the medical physics community would benefit greatly from a structured code and data sharing site. A new project [1], funded through the STFC Global Challenge Network+ in Advanced Radiotherapy [2], aims to collate, host, validate experimentally, and disseminate common Geant4 beam line models. We will present an overview of the aims of the project, and details of how to gain access to these structured models; a structured model includes both code and data with related information on use and best practice. To illustrate this, three validation results will be shown; the iThemba LABS proton therapy centre in Cape Town (South Africa), the medical beam line of the University of Birmingham MC40 Cyclotron (United Kingdom), and ongoing work with multiple models of the Clatterbridge Cancer Centre proton eye therapy beam line (United Kingdom). We aim to develop these models in TOPAS/GATE to facilitate their use for non Geant4/C++ experts, for example, medical physicists working in hospitals. A status report of this final step will be provided.
References 1. https://trello.com/b/paBx8sJZ/shared-data. . 2. https://www.advanced-radiotherapy.ac.uk. http://dx.doi.org/10.1016/j.ejmp.2017.09.108
Abstract ID: 203 Breast model validation for Monte Carlo evaluation of normalized glandular dose coefficients in mammography A. Sarno a,b,*, G. Mettivier a,b, F. Di Lillo a,b, K. Bliznakova c, I. Sechopoulos d,e, P. Russo a,b a Università di Napoli Federico II, Dipartimento di Fisica ‘‘Ettore Pancini”, Via Cintia, I-80126 Napoli, Italy b INFN Sezione di Napoli, Via Cintia, I-80126 Napoli, Italy c Department of Electronics, Technical University of Varna, 1 Studentska Str, Varna 9010, Bulgaria d Dutch reference centre for screening (LRCB), PO Box 6873, 6503 GJ Nijmegen, The Netherlands e Department of Radiology and Nuclear Medicine, Radboud University Medical Centre, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands ⇑ Presenting author.
In Monte Carlo simulations for estimation of normalized glandular dose coefficients (i.e. the ratio between the mean glandular dose (MGD) and incident air kerma at the breast upper surface), the radiosensitive breast tissue is modelled as a homogeneous mixture of adipose and glandular tissue. However, such an assumption has been shown to lead to an overestimation in MGD by an average of 30% [1,2]. This work aimed at comparing the homogeneous breast models proposed by different authors and in different quality assurance protocols to patient specific breast phantoms. To obtain these phantoms, uncompressed breast images were acquired with a CT scanner dedicated to the breast and segmented to classify each voxel into 4 categories: air, skin tissue, adipose tissue and glandular tissue. Then the compression which breasts undergo during a mammography exams was simulated via software in order to obtain 3D compressed patient specific breast phantoms which present an heterogeneous glandular distribution similar to that of the irradiated breast. The homogeneous breast phantom was simulated either with a 4-mm skin thickness (as adopted in the USA protocol), or with a 5mm adipose layer simulating the skin and the subcutaneous adipose layer (as adopted in the EU protocol) or with a skin thickness of 1.45 mm (i.e. the skin thickness estimated from 3D breast images).