Evaluation of the dose rate and energy dependence of GafchromicTM EBT3 film for the application of total body irradiation and total skin electron therapy dosimetry

ABSTRACT Aim: Total body irradiation (TBI) and total skin electron therapy (TSET) are special radiotherapy techniques that differ from routine radiotherapy therapy. They are intended to deliver a uniform dose to the entire body or skin and involve complex treatment procedures. It is therefore mandatory to perform an in-vivo dosimetry check to ensure dose accuracy and dose homogeneity during treatment. This study aims to investigate the dosimetric characteristics of GafchromicTM EBT3 film aimed at the application of TBI and TSET dosimetry. Materials and Methods: GafchromicTM EBT3 film by Ashland is a more widely used and convenient in-vivo detector than other detectors. Though many studies have reported the dosimetric characteristics of EBT3 film, those based on the electron beam are very limited. In our hospital, we perform in-vivo dosimetry in TBI and TSET with EBT3 films. Since TSET is performed with a high dose rate, the calibration curves of the low, nominal and high dose rates of the 6 MeV electron beam were evaluated in this study. Additionally, the change in response of a 6 MV photon beam to a 6 MeV electron beam was compared. Furthermore the orientation and stabilization time of EBT3 film were analysed in this study. Results: This study confirms that EBT3 films are dose-rate independent, and the change in response of a 6 MV photon beam to a 6 MeV electron beam was negligible. Further, this study shows that the photon calibration curve can be used in the dosimetric evaluation of both TBI and TSET. Conclusions: Consequently, Gafchromic EBT3 films are shown to be reliable for TBI and TSET in-vivo dosimetry..