M T Bahreyni Toossi - Medical Physics Research Center, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran
F Khorshidi - Medical Physics Research Center, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran
M Ghorbani - Medical Physics Research Center, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran
N Mohamadian - Medical Physics Research Center, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran
D Davenport - Comprehensive Cancer Centers of Nevada, Las Vegas, Nevada, USA

Background: EBT and EBT۳ radioChromic films have been used in radiotherapy dosimetry for years.Objective: The aim of the current study is to compare EBT and EBT۳ radioChromic films in dosimetry of radiotherapy fields for treatment of parotid cancer.Methods: Calibrations of EBT and EBT۳ films were performed with identical setups using a ۶ MV photon beam of a Siemens Primus linac. Skin dose was measured at different points in the right anterior oblique (RAO) and right posterior oblique (RPO) fields by EBT and EBT۳ films on a RANDO phantom.Results: While dosimetry was performed with the same conditions for the two film types for calibration and in phantom in parotid cancer radiotherapy, the measured net optical density (NOD) in EBT film was found to be higher than that from EBT۳ film. The minimum difference between these two films under calibration conditions was about ۲.۹% (for ۰.۲ Gy) with a maximum difference of ۳۵.۵% (for ۰.۵ Gy). In the therapeutic fields of parotid cancer radiotherapy at different points, the measured dose from EBT film was higher than the EBT۳ film. In these fields the minimum and maximum measured dose differences were ۱۶.۰% and ۲۵.۵%, respectively.Conclusion: EBT film demonstrates higher NOD than EBT۳ film. This effect may be related to the higher sensitivity of EBT film over EBT۳ film. However, the obtained dose differences between these two films in low dose range can be due to the differences in fitting functions applied following the calibration process.Â

RadioChromic film, EBT, EBT۳, Radiotherapy, Parotid cancer