- Email: [email protected]
34A Small field dosimetry for electron beams using four types of detectors
Abstracts / Physica Medica 56 (2018) 40–58
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Introduction. The size of Radiotherapy (RT) departments makes difficult to organize a complete in-house training for the therapists. In a French center there are often 40 to 50 therapists and treatment time slots are large so it is difficult to achieve a classic training. Moreover the training is mainly achieved by people who are poorly available (physicists, physicians, therapists . . .). Nevertheless the needs of training are very important. Indeed, RT therapists have a central role in the patient security chain and technologies evolve very quickly. New skills and knowledge are continuously asked (new devices, new treatment techniques or a simple software or hardware update). We present in this work the MYRE (MY Recordable E-Learning) database developed in our cancer center that is a full solution of e-learning of RT therapists. Methods. A Microsoft ACCESS database (BDD) was implemented. It contains all the information concerning the therapists and a link to approximately 200 micro-modules. It allows recording and requesting every training act (request can be done for a given therapist, a given module, a year. . .). These 200 micro-modules are separated in three types: 1. Simple written procedures from the institutional document database that the user must read. 2. Some particular techniques that the user must see. 3. SPOC (Small Private Online Classes): these videos that we made last generally 10 min and are associated to an online multiple-choice test (MCT). This MCT are autocorrected: the user obtains a score and explanations are given to understand the correct answers. The therapists can access to MYRE in complete autonomy (training, evaluation, and recording of the acquired micro-modules). Results. Between January and March 2018, approximately 600 training acts were recorded in MYRE. Special requests were implemented to allow the manager to edit some specific lists like ‘‘list of therapists with all the mandatory skills for a given medical device”. Some therapists are involved in the database maintenance and the making of videos and MCT. Conclusion. A database with a link to 200 documents (videos or written procedures) was developed and deployed in the department. It allows the therapists to train in full autonomy. In this study we made a lot of videos and observed that they are an effective tool to introduce technical concepts while written procedures are better for the description of tasks. MYRE is well accepted by therapists (results of an internal audit).
allel ion chamber Markus PTW 23343 and two solid detectors: PTW60017 unshielded diode, and PTW 60019 Micro-Diamond). Results. The PDDs showed an agreement of ±1% between values measured by the diode and the microdiamond detector. The two solid detectors are characterized by their small sensitive volume suitable for dosimetry in small fields. These results are similar when compared to those found by Laub et al. [1]. A discrepancy of 2.5% was found between the Markus chamber and the Micro-Diamond. This disagreement was most important in the region of high gradient dose and in the area near the surface where the detectors are partially in the air. The diamond detector and the diode provided the curve directly in dose while the depth-dependent corrections were necessary for the ionization chamber Markus [2]. The diode has the narrowest penumbra with a mean difference of 0.6 mm compared to the one measured by the diamond detector. PinPoint ionization chamber shows the lowest spatial resolution, with a widening of the penumbra compared to the one measured by the diode and the diamond. The difference found between the output factors OF between the Markus chamber and the diamond detector was less than 2% except for the field size of 2 2 cm2 and this for all energies and that because of the relatively large volume of the Markus ionization chamber. Finally, a good agreement between the two solid detectors was reported except for 6 MeV for the field size of 2 2 cm2. Conclusion. Dosimetric properties observed indicate that microdiamond and diode detectors are the most efficient for dosimetry of small electron field used in radiotherapy.
https://doi.org/10.1016/j.ejmp.2018.09.116
35 Calculation of organ doses for CT examination T. Julien, A. Al Masri, L. Guérin, S. Battini, F. Maaloul
References 1. Laub et al. Clinical radiation therapy measurements with a new commercial synthetic single crystal diamond detector. J Appl Clin Med Phys 2014;15(6):92–102. 2. IAEA. Technical Report Series No. 398 (Vienna, 2000). https://doi.org/10.1016/j.ejmp.2018.09.125
Diagnostic imaging
BIOMEDIQA, Villeneuve d’Ascq, France 34A Small field dosimetry for electron beams using four types of detectors I. Saidani a, L. Ben Salem a, M. Besbes a,b a
Institut Supérieur des Technologies Médicales de Tunis (ISTMT), Tunis, Tunisia b Institut Saleh Azaiz (ISA), Tunis, Tunisia Introduction. Accurate calculation of dose by Treatment Planning System (TPS) depends on the quality of the measured data used to configure the beam models. It is advisable to choose the most suitable detector for the experimental conditions and the need of precision required for the knowledge of the absorbed dose and its spatial distribution. Methods. The purpose of this work is to study the dosimetric characterization of the small electron fields ranging from 2 to 6 cm for energies of 6, 9, 12, 1 6 and 20 MeV generated by the linear accelerator ClinaciX (Varian). Percentage depth dose (PDD), OAR dose profile, and output factor (OF) were performed by the four different types of detectors manufactured by PTW-FreiburgÒ (Cylindrical chamber Micro-ion chamber PTW Pinpoint 3D 0.016 cm3, plane par-
Introduction. Ionising radiation needs to be precisely evaluated since CT scan is the main radiological examination today. Biological effects caused by radiation are estimated with computational methods as it’s not possible to measure the real doses delivered directly to a specific organ. The DOSITRACE software is a Dose Archiving and Communication System (DACS) based on a new calculation method which allows a more reliable estimation of organ doses. The aim of this study was to compare our results with the results given by the VIRTUALDOSE [1] software using the Monte-Carlo method. Methods. CTDIvol, current and rotation time for each acquisition were used to calculate organ doses (ICPR). Four CT protocols (abdomen-pelvis, chest-abdomen-pelvis, chest and thorax) were used with three different CT scans. Thirty patients were selected for each protocol. In total, CT scan exams were analysed and our results were compared with the ones obtained with the VIRTUALDOSE software. Results. There was only a 20% difference in the estimation of organ doses between the VIRTUALDOSE and DOSITRACE software’s results which is not statistically significant.
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Introduction. The size of Radiotherapy (RT) departments makes difficult to organize a complete in-house training for the therapists. In a French center there are often 40 to 50 therapists and treatment time slots are large so it is difficult to achieve a classic training. Moreover the training is mainly achieved by people who are poorly available (physicists, physicians, therapists . . .). Nevertheless the needs of training are very important. Indeed, RT therapists have a central role in the patient security chain and technologies evolve very quickly. New skills and knowledge are continuously asked (new devices, new treatment techniques or a simple software or hardware update). We present in this work the MYRE (MY Recordable E-Learning) database developed in our cancer center that is a full solution of e-learning of RT therapists. Methods. A Microsoft ACCESS database (BDD) was implemented. It contains all the information concerning the therapists and a link to approximately 200 micro-modules. It allows recording and requesting every training act (request can be done for a given therapist, a given module, a year. . .). These 200 micro-modules are separated in three types: 1. Simple written procedures from the institutional document database that the user must read. 2. Some particular techniques that the user must see. 3. SPOC (Small Private Online Classes): these videos that we made last generally 10 min and are associated to an online multiple-choice test (MCT). This MCT are autocorrected: the user obtains a score and explanations are given to understand the correct answers. The therapists can access to MYRE in complete autonomy (training, evaluation, and recording of the acquired micro-modules). Results. Between January and March 2018, approximately 600 training acts were recorded in MYRE. Special requests were implemented to allow the manager to edit some specific lists like ‘‘list of therapists with all the mandatory skills for a given medical device”. Some therapists are involved in the database maintenance and the making of videos and MCT. Conclusion. A database with a link to 200 documents (videos or written procedures) was developed and deployed in the department. It allows the therapists to train in full autonomy. In this study we made a lot of videos and observed that they are an effective tool to introduce technical concepts while written procedures are better for the description of tasks. MYRE is well accepted by therapists (results of an internal audit).
allel ion chamber Markus PTW 23343 and two solid detectors: PTW60017 unshielded diode, and PTW 60019 Micro-Diamond). Results. The PDDs showed an agreement of ±1% between values measured by the diode and the microdiamond detector. The two solid detectors are characterized by their small sensitive volume suitable for dosimetry in small fields. These results are similar when compared to those found by Laub et al. [1]. A discrepancy of 2.5% was found between the Markus chamber and the Micro-Diamond. This disagreement was most important in the region of high gradient dose and in the area near the surface where the detectors are partially in the air. The diamond detector and the diode provided the curve directly in dose while the depth-dependent corrections were necessary for the ionization chamber Markus [2]. The diode has the narrowest penumbra with a mean difference of 0.6 mm compared to the one measured by the diamond detector. PinPoint ionization chamber shows the lowest spatial resolution, with a widening of the penumbra compared to the one measured by the diode and the diamond. The difference found between the output factors OF between the Markus chamber and the diamond detector was less than 2% except for the field size of 2 2 cm2 and this for all energies and that because of the relatively large volume of the Markus ionization chamber. Finally, a good agreement between the two solid detectors was reported except for 6 MeV for the field size of 2 2 cm2. Conclusion. Dosimetric properties observed indicate that microdiamond and diode detectors are the most efficient for dosimetry of small electron field used in radiotherapy.
https://doi.org/10.1016/j.ejmp.2018.09.116
35 Calculation of organ doses for CT examination T. Julien, A. Al Masri, L. Guérin, S. Battini, F. Maaloul
References 1. Laub et al. Clinical radiation therapy measurements with a new commercial synthetic single crystal diamond detector. J Appl Clin Med Phys 2014;15(6):92–102. 2. IAEA. Technical Report Series No. 398 (Vienna, 2000). https://doi.org/10.1016/j.ejmp.2018.09.125
Diagnostic imaging
BIOMEDIQA, Villeneuve d’Ascq, France 34A Small field dosimetry for electron beams using four types of detectors I. Saidani a, L. Ben Salem a, M. Besbes a,b a
Institut Supérieur des Technologies Médicales de Tunis (ISTMT), Tunis, Tunisia b Institut Saleh Azaiz (ISA), Tunis, Tunisia Introduction. Accurate calculation of dose by Treatment Planning System (TPS) depends on the quality of the measured data used to configure the beam models. It is advisable to choose the most suitable detector for the experimental conditions and the need of precision required for the knowledge of the absorbed dose and its spatial distribution. Methods. The purpose of this work is to study the dosimetric characterization of the small electron fields ranging from 2 to 6 cm for energies of 6, 9, 12, 1 6 and 20 MeV generated by the linear accelerator ClinaciX (Varian). Percentage depth dose (PDD), OAR dose profile, and output factor (OF) were performed by the four different types of detectors manufactured by PTW-FreiburgÒ (Cylindrical chamber Micro-ion chamber PTW Pinpoint 3D 0.016 cm3, plane par-
Introduction. Ionising radiation needs to be precisely evaluated since CT scan is the main radiological examination today. Biological effects caused by radiation are estimated with computational methods as it’s not possible to measure the real doses delivered directly to a specific organ. The DOSITRACE software is a Dose Archiving and Communication System (DACS) based on a new calculation method which allows a more reliable estimation of organ doses. The aim of this study was to compare our results with the results given by the VIRTUALDOSE [1] software using the Monte-Carlo method. Methods. CTDIvol, current and rotation time for each acquisition were used to calculate organ doses (ICPR). Four CT protocols (abdomen-pelvis, chest-abdomen-pelvis, chest and thorax) were used with three different CT scans. Thirty patients were selected for each protocol. In total, CT scan exams were analysed and our results were compared with the ones obtained with the VIRTUALDOSE software. Results. There was only a 20% difference in the estimation of organ doses between the VIRTUALDOSE and DOSITRACE software’s results which is not statistically significant.