会議発表用資料 Radiophotoluminescent glass dosimeter application to the dose audit of flattening-filter-free linear accelerator, Tomotherapy and Cyberknife

水野, 秀之  ,  遠山, 尚紀  ,  福村, 明史  ,  福田, 茂一  ,  佐方, 周防  ,  山下, 航  ,  高瀬, 信宏

2016-12-11
内容記述
Purpose: In Japan, postal dose audits have been performed on radiation therapy units using a radiophotoluminescent glass dosimeter (RGD), since 2007. The purpose of this study was to obtain a set of correction factors of the RGD output for reference condition for flattening-filter-free linear accelerator (FFF), Tomotherapy (Tomo) and Cyberknife (CK).Methods: Special phantom was designed in order to place 3 RGD elements in a tiny uniform region (dose gradient < 0.2%) at a field center around 3 mm. RGDs were irradiated by using this phantom for 1 Gy. Ionization chamber measurements using an A1SL chamber (Exradin) were done for same reference condition and monitor units for each modality. The response of RGD were evaluated by calculating the ratio between RGD and IC outputs. For every modality, at least 3 different machines were used and the results were averaged to derive final response of the RGD.Results: The response of the RGD was -0.1% (6 MV) and -0.6% (10 MV) for FFF, -0.8% (6 MV) for Tomo, and -0.1% (6 MV) for CK. The RGD showed good responses of less than 1% for the beam from every modality. For FFF beam, the difference could be attributed to the decrease of kQ for IC measurement of FFF beam that was mentioned in some published papers.Conclusion: RGD was proved to be useful to the modern treatment units. We will expand our audit application to such new modalities.
International Conference on Medical Physics 2016

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