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Dosimetric impact of multileaf collimator position errors during prostatic treatment by dynamic arctherapy
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Abstracts of the SFPM Annual Meeting 2013 / Physica Medica 29 (2013) e1–e46
64 DOSIMETRIC IMPACT OF MULTILEAF COLLIMATOR POSITION ERRORS DURING PROSTATIC TREATMENT BY DYNAMIC ARCTHERAPY J. Molinier 1,2, P. Martinez 1, V. Bodez 1, C. Khamphan 1, E. Jaegle 1, A. Badey 1, M.E. Alayrach 1, R. Garcia 1, L. Vieillevigne 2, T. Brun 2, R. Ferrand 2. 1 Institut Sainte Catherine, Avignon, France, 2 Institut Claudius Regaud, Toulouse, France Introduction: The quality of a treatment performed by intensity modulation is based on the positioning accuracy of the multileaf collimator leaves (MLC, 120 leaves). The dosimetric impact achieved by the introduction of systematic errors on the leaves positioning has been studied to assess the generated effects. Materials and methods: The study was performed on 8 patients treated for prostate localization with 80 Gy prescribed dose in dynamic arc therapy. Original treatment plans clinically approved were exported in DICOM RT to be processed using MatlabÒ software. Systematic errors of magnitude between 0.5 mm and 5 mm were introduced by opening the MLC leaves, or by closing and shifting. The 128 revised plans were then introduced into the treatment planning system (TPS). They were recalculated keeping the same optimization constraints than the original plan. Geometric and dosimetric index (SFRO and ICRU used index) were calculated using the ArtiviewÒ software, Aquilab. Results: Changes introduced to the original plans are significantly impacting dosimetric treatment planning validation index. Among these index, the near maximum dose D_2%(Gy) received by the target volume (PTV) differs from 12%, 15% and 20% to the original treatment plan for maximum openings, shifts and closures respectively. For the same index and amplitude errors of up to 2 mm, an offset MLC error is less penalizing (<3%) rather than an opening or closing (>5%) systematic error. Other dosimetric and geometric index complete the analysis as the Dice similarity coefficient (DSC), which is more sensitive to errors introduction in treatment plans. Conclusion: Dosimetric validation is based on calculated and measured doses distributions comparison, thanks to tolerances (generally 3%/3 mm). This study allows us to understand the impact of potential MLC positioning errors on planned treatment and to discuss about the validity of quality assurance tolerance values.
sugar/EPR system showed an interesting dosimetric properties of this material in the field of radiotherapy [3]. To deepen the analysis of dosimetric properties of table sugar, in this work we present the results of the study carried out by EPR on table sugar irradiated by: Beams of photons X maximum energy 6 MeV and 18 MeV electrons from the braking of 6 MeV and 18 MeV in a linear accelerator installed in CHU of Casablanca, MAROCCO. Radiation emitted by a source gamma Cs-137 installed at Paul Strauss cancer center in Strasbourg, FRANCE. Neutron energy delivered by the cyclotron of Louvain-la-Neuve in BELGIUM. After irradiation of the sugar samples by these particles, with doses ranging from 0–20 Gy, EPR measurements carried out have revealed a complex spectrum due to the contribution of different free radicals produced by irradiation. the Analyze of the EPR measurements by peak to peak and double integration methods revealed that, in the case of different irradiating particles, calibration curves obtained as a function of radiation dose are quite linear. Good accuracy (error less than 5%) is observed for the various measures undertaken by RPE. The analysis results also show that sugar is more sensitive to X rays and gamma rays than neutrons. In conclusion, this study shows that table sugar presents the interesting dosimetric properties for its use in the field of radiotherapy. References [1] Lin M, Garcia T, Lourenço V, Cui Y, Chen YZ, Wang F. Bilateral comparison of an alanine/ESR dosimetry system at radiotherapy dose levels. Rad. Measur. 2010;45:789–96. [2] Mikou M, Benzina S, Bischoff P, Denis JM, Gueulette J. EPR analysis of the effects of accelerated carbon ion and fast neutron irradiations on table sugar. Appl. Radiat. Isot. 2009;67– 69:1738–41. [3] Ghosne N, Mikou M, Fahli A, Moussetad M, Bougteb M, Aboulfatah M, Kuntz F. Study by electron paramagnetic resonance of dosimetric properties of sugar irradiated by photon X18MV beam issued by linear accelerator CLINAC2100C. Phys. Chem. News 2011;62:19–25. http://dx.doi.org/10.1016/j.ejmp.2013.08.071
http://dx.doi.org/10.1016/j.ejmp.2013.08.070 POSTERS 65 ANALYSIS BY EPR OF THE DOSIMETRIC PROPERTIES OF TABLE SUGAR IRRADIATED BY X-RAYS, GAMMA RAYS AND NEUTRONS M. Mikou 1, N. Ghosne 2, Z. Zirari 1, P. Bischoff 3, F. Kuntz 4, M. Bougteb 1. 1 Laboratoire d’Analyse des Systèmes et de Traitement de l’Information Université Hassan Ier, FST, Settat, Morocco, 2 CHU de Casablanca, Service d’Oncologie, Casablanca, Morocco, 3 Laboratoire de Radiobiologie, Université de Strasbourg, France, Centre Paul Strauss, Strassbourg, France, 4 Centre de Ressources Technologiques Aérial, Illkirch, France Currently, a particular attention is paid to the development of dosimeters whose reading system is based on the physical principle of electron paramagnetic resonance ‘‘EPR”. This method has the advantage of being accurate and non-destructive. Dosimetric systems based on EPR can be used for monitoring and evaluation of the absorbed dose in ionizing radiation in the field of radiotherapy or radioprotection [1,2]. Preliminary studies realised on table
66 IMAGING AND RADIATION THERAPY: GATE MONTE CARLO SIMULATION OF A MV-CBCT FLAT PANEL WITH SPECIFIC APPLICATION IN HEAD AND NECK CANCER S. Benhalouchen 1, J. Bert 1,2, D. Visvikis 1,2, O. Pradier 1,2, N. Boussion 1,2. 1 LaTIM, UMR INSERM 1101, Brest, France, 2 CHRU Morvan, Service de Radiothérapie, Brest, France Purpose: In radiotherapy treatment, it is necessary to position the patient before each session to ensure that the beams target the tumor while sparing the surrounding healthy tissue. This step is made possible via different imaging techniques like the ‘‘electronic portal imaging device” (EPID) which is the most common approach. In this configuration, the imaging source is the same as the treatment source, while a flat panel detector is automatically placed under the patient via an articulated arm. In this context, our study
Abstracts of the SFPM Annual Meeting 2013 / Physica Medica 29 (2013) e1–e46
64 DOSIMETRIC IMPACT OF MULTILEAF COLLIMATOR POSITION ERRORS DURING PROSTATIC TREATMENT BY DYNAMIC ARCTHERAPY J. Molinier 1,2, P. Martinez 1, V. Bodez 1, C. Khamphan 1, E. Jaegle 1, A. Badey 1, M.E. Alayrach 1, R. Garcia 1, L. Vieillevigne 2, T. Brun 2, R. Ferrand 2. 1 Institut Sainte Catherine, Avignon, France, 2 Institut Claudius Regaud, Toulouse, France Introduction: The quality of a treatment performed by intensity modulation is based on the positioning accuracy of the multileaf collimator leaves (MLC, 120 leaves). The dosimetric impact achieved by the introduction of systematic errors on the leaves positioning has been studied to assess the generated effects. Materials and methods: The study was performed on 8 patients treated for prostate localization with 80 Gy prescribed dose in dynamic arc therapy. Original treatment plans clinically approved were exported in DICOM RT to be processed using MatlabÒ software. Systematic errors of magnitude between 0.5 mm and 5 mm were introduced by opening the MLC leaves, or by closing and shifting. The 128 revised plans were then introduced into the treatment planning system (TPS). They were recalculated keeping the same optimization constraints than the original plan. Geometric and dosimetric index (SFRO and ICRU used index) were calculated using the ArtiviewÒ software, Aquilab. Results: Changes introduced to the original plans are significantly impacting dosimetric treatment planning validation index. Among these index, the near maximum dose D_2%(Gy) received by the target volume (PTV) differs from 12%, 15% and 20% to the original treatment plan for maximum openings, shifts and closures respectively. For the same index and amplitude errors of up to 2 mm, an offset MLC error is less penalizing (<3%) rather than an opening or closing (>5%) systematic error. Other dosimetric and geometric index complete the analysis as the Dice similarity coefficient (DSC), which is more sensitive to errors introduction in treatment plans. Conclusion: Dosimetric validation is based on calculated and measured doses distributions comparison, thanks to tolerances (generally 3%/3 mm). This study allows us to understand the impact of potential MLC positioning errors on planned treatment and to discuss about the validity of quality assurance tolerance values.
sugar/EPR system showed an interesting dosimetric properties of this material in the field of radiotherapy [3]. To deepen the analysis of dosimetric properties of table sugar, in this work we present the results of the study carried out by EPR on table sugar irradiated by: Beams of photons X maximum energy 6 MeV and 18 MeV electrons from the braking of 6 MeV and 18 MeV in a linear accelerator installed in CHU of Casablanca, MAROCCO. Radiation emitted by a source gamma Cs-137 installed at Paul Strauss cancer center in Strasbourg, FRANCE. Neutron energy delivered by the cyclotron of Louvain-la-Neuve in BELGIUM. After irradiation of the sugar samples by these particles, with doses ranging from 0–20 Gy, EPR measurements carried out have revealed a complex spectrum due to the contribution of different free radicals produced by irradiation. the Analyze of the EPR measurements by peak to peak and double integration methods revealed that, in the case of different irradiating particles, calibration curves obtained as a function of radiation dose are quite linear. Good accuracy (error less than 5%) is observed for the various measures undertaken by RPE. The analysis results also show that sugar is more sensitive to X rays and gamma rays than neutrons. In conclusion, this study shows that table sugar presents the interesting dosimetric properties for its use in the field of radiotherapy. References [1] Lin M, Garcia T, Lourenço V, Cui Y, Chen YZ, Wang F. Bilateral comparison of an alanine/ESR dosimetry system at radiotherapy dose levels. Rad. Measur. 2010;45:789–96. [2] Mikou M, Benzina S, Bischoff P, Denis JM, Gueulette J. EPR analysis of the effects of accelerated carbon ion and fast neutron irradiations on table sugar. Appl. Radiat. Isot. 2009;67– 69:1738–41. [3] Ghosne N, Mikou M, Fahli A, Moussetad M, Bougteb M, Aboulfatah M, Kuntz F. Study by electron paramagnetic resonance of dosimetric properties of sugar irradiated by photon X18MV beam issued by linear accelerator CLINAC2100C. Phys. Chem. News 2011;62:19–25. http://dx.doi.org/10.1016/j.ejmp.2013.08.071
http://dx.doi.org/10.1016/j.ejmp.2013.08.070 POSTERS 65 ANALYSIS BY EPR OF THE DOSIMETRIC PROPERTIES OF TABLE SUGAR IRRADIATED BY X-RAYS, GAMMA RAYS AND NEUTRONS M. Mikou 1, N. Ghosne 2, Z. Zirari 1, P. Bischoff 3, F. Kuntz 4, M. Bougteb 1. 1 Laboratoire d’Analyse des Systèmes et de Traitement de l’Information Université Hassan Ier, FST, Settat, Morocco, 2 CHU de Casablanca, Service d’Oncologie, Casablanca, Morocco, 3 Laboratoire de Radiobiologie, Université de Strasbourg, France, Centre Paul Strauss, Strassbourg, France, 4 Centre de Ressources Technologiques Aérial, Illkirch, France Currently, a particular attention is paid to the development of dosimeters whose reading system is based on the physical principle of electron paramagnetic resonance ‘‘EPR”. This method has the advantage of being accurate and non-destructive. Dosimetric systems based on EPR can be used for monitoring and evaluation of the absorbed dose in ionizing radiation in the field of radiotherapy or radioprotection [1,2]. Preliminary studies realised on table
66 IMAGING AND RADIATION THERAPY: GATE MONTE CARLO SIMULATION OF A MV-CBCT FLAT PANEL WITH SPECIFIC APPLICATION IN HEAD AND NECK CANCER S. Benhalouchen 1, J. Bert 1,2, D. Visvikis 1,2, O. Pradier 1,2, N. Boussion 1,2. 1 LaTIM, UMR INSERM 1101, Brest, France, 2 CHRU Morvan, Service de Radiothérapie, Brest, France Purpose: In radiotherapy treatment, it is necessary to position the patient before each session to ensure that the beams target the tumor while sparing the surrounding healthy tissue. This step is made possible via different imaging techniques like the ‘‘electronic portal imaging device” (EPID) which is the most common approach. In this configuration, the imaging source is the same as the treatment source, while a flat panel detector is automatically placed under the patient via an articulated arm. In this context, our study