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Study of the secondary neutral radiation in proton therapy: Toward an indirect in vivo dosimetry
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Abstracts of the SFPM Annual Meeting 2013 / Physica Medica 29 (2013) e1–e46
Matrix dose in tissues are exported to Dicom matrix (RT dose) in water dose, recognized by the commercial TPS for easier comparison. Conclusion: Software based on this study was created and was called AVOQA (Application for Voxelization by Optimized Quadtree Algorithm). Compared to alternative applications, AVOQA creates a voxelization for MCNPX directly from CT-scan without using the organs contours; in addition it applies the CT-can calibrations. Thus AVOQA is a great MCNPX voxelization tool for CT-scan images, and it is the most accurate and faithful. http://dx.doi.org/10.1016/j.ejmp.2013.08.057
52 STUDY OF THE SECONDARY NEUTRAL RADIATION IN PROTON THERAPY: TOWARD AN INDIRECT IN VIVO DOSIMETRY A. Carnicer, V. Letellier, G. Rucka, G. Angellier, W. Sauerwein, J. Herault. Centre Antoine Lacassagne/Institut Curie, Centre de Protonthérapie, Centre Universitaire d’Orsay, Orsay, France, Hôpital de la Croix Rouge, Centre de Radiothérapie Saint Louis, Toulon, France, Universität Duisburg-Essen, Universitätsklinikum Essen, Strahlenklinik, Essen, Germany Introduction: The proton therapy facility at Centre Antoine Lacassagne in Nice uses the 65 MeV isochronous cyclotron MEDICYC to treat eye tumors. The passive scattering allows to deliver a ‘‘plateau” percentage depth dose (or Spread-Out-Bragg-Peak), in order to cover the target volume in depth. This modulation is given by a range shifter and a range modulator wheel, which are adapted to each patient treatment. At the end of the beam line, the patient collimator reduces the beam laterally to protect healthy tissues. Secondary particles are produced in the collision of protons with beam line elements: photons and neutrons, which are able to escape from the patient and can be used, in theory, for in vivo dosimetry and quality assurance measurements. The secondary particles production is closely linked through the modulation accessories. Materials and methods: The aim of this study is to investigate the relationship between proton dose and secondary particle production. Monte Carlo calculations, using MCNPX code, and measurements were extended to 100 clinical Spread-Out-Bragg-Peak covering the whole range of therapeutic dose rates (D/MU). The measurements were performed for validation of Monte Carlo calculations. Results: This work highlights the existence of a correlation function between proton dose and secondary particle production. Knowing this relation in one point of the tratment room, it is possible to develop a quality assurance system which controls the effective proton dose rate delivered to the patient. Conclusion: This system has been installed and is now used routinely. It allows the delivered dose to be monitored independently of the beam monitor reading and offers a new approach to the conventional in vivo dosimetry in protontherapy. http://dx.doi.org/10.1016/j.ejmp.2013.08.058
POSTERS
53 STUDY OF SECONDARY RADIATION PARTICULES FOR EYES PROTONTHERAPY, TOWARD IN VIVO DOSIMETRY H. Morin, M. Galland, E. Constant, V. Letellier, N. Fournier-Bidoz. Centre de Protonthérapie d’Orsay, Campus Universitaire d’Orsay, Orsay, France
Introduction: As part of the continuous process of improving the eye treatment at the proton therapy center of Orsay, the purpose of this study is to approve the model of the treatment line and treatment room by studying the distribution of the secondary particles at different points of interest in the room. Computer simulations will be performed by Monte Carlo codes. The aim is also to develop a method of in vivo dosimetry for proton therapy using the doses due to secondary particles, which could be proved by Monte Carlo simulations. Material and methods: The Monte Carlo calculations were performed using the code MCNPX 2.6e of the Los Alamos National Laboratory (LANL), particularly its mesh tallies were used in order to realize a map dose of the room. The modelling of the medical facility (optical bench, beam line, room, etc.) are improved from existing codes and relying on the plans of the installation. For the experimental measurements of secondary particles, a neutron detector Berthold LB6411 and photon detector APVL AT1123 were used. Finally ROTEM neutron detector LAP-10H could also be used. Results: Fluences and doses induced by secondary particles during the protontherapy treatments at various points of interest of the room are estimated by the code MCNPX and validated by experimental measurements. Moreover the latter allow us to characterize variations due to the ballistic configuration of each patient (modulators, reducing travel, collimator, etc.). Finally in vivo dosimetry will be based on automatic measurements of prompt gammas, which could provide ballistic conditions of the treatment via a mathematic algorithm. Conclusion: This study validates the previously acquired knowledge about secondary radiation, especially about doses received by the patient and the medical staff. A real-time radiation protection tool analysing the measurements of the control detectors in the treatment room could be achieved and included in a clinical workflow. This tool for in vivo dosimetry, which confirms the first treatment of the patient (in case of an error inferior to 5%) like in radiotherapy, seems to be a future reality in proton therapy workflow. http://dx.doi.org/10.1016/j.ejmp.2013.08.059
54 MODELIZATION OF THE OPHTHALMIC TREATMENT SET UP BEAM LINE OF THE INSTITUT CURIE – CENTRE DE PROTONTHÉRAPIE D’ORSAY M. Galland, H. Morin, C. Nauraye. Centre de Protonthérapie de l’Institut Curie d’Orsay, Campus Universitaire d’Orsay, Orsay, France Introduction: In order to simulate the dose measurement of ophthalmic treatments by Monte Carlo at the ICCPO, the modeling of the geometrical elements of the set up beam line was achieved. However, a problem has been identified about the position and the characterisation of the virtual proton beam source. Until now, we could only model a divergent source after the modulator preventing the creation of spread-out Bragg peaks (SOBP). Thus, it was necessary to modelize a convergence source to validate the beam line. Material and methods: Monte Carlo calculations are performed using the code MCNPX 2.6e Los Alamos National Laboratory (LANL). To create our source we used a spherical volume source delimited by a plane. For the experimental measurements, we used a water tank, an ionization chamber IBA PPC05 for the acquisition of Bragg peaks, radiochromic films and a 2D detector Lynx Fimel for transverse dose profiles. The code was then compared to the measurments for validation. Results: According to EBT2 films, we observed the convergence of the source after the modulator wheel. Therefore, we have succeeded in modeling of the MCNPX source respecting the actual parameters and having the ability to create SOBP. With this source we were able to validate all the elements of the optical bench. The comparison
Abstracts of the SFPM Annual Meeting 2013 / Physica Medica 29 (2013) e1–e46
Matrix dose in tissues are exported to Dicom matrix (RT dose) in water dose, recognized by the commercial TPS for easier comparison. Conclusion: Software based on this study was created and was called AVOQA (Application for Voxelization by Optimized Quadtree Algorithm). Compared to alternative applications, AVOQA creates a voxelization for MCNPX directly from CT-scan without using the organs contours; in addition it applies the CT-can calibrations. Thus AVOQA is a great MCNPX voxelization tool for CT-scan images, and it is the most accurate and faithful. http://dx.doi.org/10.1016/j.ejmp.2013.08.057
52 STUDY OF THE SECONDARY NEUTRAL RADIATION IN PROTON THERAPY: TOWARD AN INDIRECT IN VIVO DOSIMETRY A. Carnicer, V. Letellier, G. Rucka, G. Angellier, W. Sauerwein, J. Herault. Centre Antoine Lacassagne/Institut Curie, Centre de Protonthérapie, Centre Universitaire d’Orsay, Orsay, France, Hôpital de la Croix Rouge, Centre de Radiothérapie Saint Louis, Toulon, France, Universität Duisburg-Essen, Universitätsklinikum Essen, Strahlenklinik, Essen, Germany Introduction: The proton therapy facility at Centre Antoine Lacassagne in Nice uses the 65 MeV isochronous cyclotron MEDICYC to treat eye tumors. The passive scattering allows to deliver a ‘‘plateau” percentage depth dose (or Spread-Out-Bragg-Peak), in order to cover the target volume in depth. This modulation is given by a range shifter and a range modulator wheel, which are adapted to each patient treatment. At the end of the beam line, the patient collimator reduces the beam laterally to protect healthy tissues. Secondary particles are produced in the collision of protons with beam line elements: photons and neutrons, which are able to escape from the patient and can be used, in theory, for in vivo dosimetry and quality assurance measurements. The secondary particles production is closely linked through the modulation accessories. Materials and methods: The aim of this study is to investigate the relationship between proton dose and secondary particle production. Monte Carlo calculations, using MCNPX code, and measurements were extended to 100 clinical Spread-Out-Bragg-Peak covering the whole range of therapeutic dose rates (D/MU). The measurements were performed for validation of Monte Carlo calculations. Results: This work highlights the existence of a correlation function between proton dose and secondary particle production. Knowing this relation in one point of the tratment room, it is possible to develop a quality assurance system which controls the effective proton dose rate delivered to the patient. Conclusion: This system has been installed and is now used routinely. It allows the delivered dose to be monitored independently of the beam monitor reading and offers a new approach to the conventional in vivo dosimetry in protontherapy. http://dx.doi.org/10.1016/j.ejmp.2013.08.058
POSTERS
53 STUDY OF SECONDARY RADIATION PARTICULES FOR EYES PROTONTHERAPY, TOWARD IN VIVO DOSIMETRY H. Morin, M. Galland, E. Constant, V. Letellier, N. Fournier-Bidoz. Centre de Protonthérapie d’Orsay, Campus Universitaire d’Orsay, Orsay, France
Introduction: As part of the continuous process of improving the eye treatment at the proton therapy center of Orsay, the purpose of this study is to approve the model of the treatment line and treatment room by studying the distribution of the secondary particles at different points of interest in the room. Computer simulations will be performed by Monte Carlo codes. The aim is also to develop a method of in vivo dosimetry for proton therapy using the doses due to secondary particles, which could be proved by Monte Carlo simulations. Material and methods: The Monte Carlo calculations were performed using the code MCNPX 2.6e of the Los Alamos National Laboratory (LANL), particularly its mesh tallies were used in order to realize a map dose of the room. The modelling of the medical facility (optical bench, beam line, room, etc.) are improved from existing codes and relying on the plans of the installation. For the experimental measurements of secondary particles, a neutron detector Berthold LB6411 and photon detector APVL AT1123 were used. Finally ROTEM neutron detector LAP-10H could also be used. Results: Fluences and doses induced by secondary particles during the protontherapy treatments at various points of interest of the room are estimated by the code MCNPX and validated by experimental measurements. Moreover the latter allow us to characterize variations due to the ballistic configuration of each patient (modulators, reducing travel, collimator, etc.). Finally in vivo dosimetry will be based on automatic measurements of prompt gammas, which could provide ballistic conditions of the treatment via a mathematic algorithm. Conclusion: This study validates the previously acquired knowledge about secondary radiation, especially about doses received by the patient and the medical staff. A real-time radiation protection tool analysing the measurements of the control detectors in the treatment room could be achieved and included in a clinical workflow. This tool for in vivo dosimetry, which confirms the first treatment of the patient (in case of an error inferior to 5%) like in radiotherapy, seems to be a future reality in proton therapy workflow. http://dx.doi.org/10.1016/j.ejmp.2013.08.059
54 MODELIZATION OF THE OPHTHALMIC TREATMENT SET UP BEAM LINE OF THE INSTITUT CURIE – CENTRE DE PROTONTHÉRAPIE D’ORSAY M. Galland, H. Morin, C. Nauraye. Centre de Protonthérapie de l’Institut Curie d’Orsay, Campus Universitaire d’Orsay, Orsay, France Introduction: In order to simulate the dose measurement of ophthalmic treatments by Monte Carlo at the ICCPO, the modeling of the geometrical elements of the set up beam line was achieved. However, a problem has been identified about the position and the characterisation of the virtual proton beam source. Until now, we could only model a divergent source after the modulator preventing the creation of spread-out Bragg peaks (SOBP). Thus, it was necessary to modelize a convergence source to validate the beam line. Material and methods: Monte Carlo calculations are performed using the code MCNPX 2.6e Los Alamos National Laboratory (LANL). To create our source we used a spherical volume source delimited by a plane. For the experimental measurements, we used a water tank, an ionization chamber IBA PPC05 for the acquisition of Bragg peaks, radiochromic films and a 2D detector Lynx Fimel for transverse dose profiles. The code was then compared to the measurments for validation. Results: According to EBT2 films, we observed the convergence of the source after the modulator wheel. Therefore, we have succeeded in modeling of the MCNPX source respecting the actual parameters and having the ability to create SOBP. With this source we were able to validate all the elements of the optical bench. The comparison