Comparison of EBT and EBT3 RadioChromic Film Usage in Parotid Cancer Radiotherapy

Background: EBT and EBT3 radioChromic flms have been used in radiotherapy dosimetry for years. Objective: The aim of the current study is to compare EBT and EBT3 radioChromic flms in dosimetry of radiotherapy felds for treatment of parotid cancer. Methods: Calibrations of EBT and EBT3 flms were performed with identical setups using a 6 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) felds by EBT and EBT3 flms on a RANDO phantom. Results: While dosimetry was performed with the same conditions for the two flm types for calibration and in phantom in parotid cancer radiotherapy, the measured net optical density (NOD) in EBT flm was found to be higher than that from EBT3 flm. The minimum difference between these two flms under calibration conditions was about 2.9% (for 0.2 Gy) with a maximum difference of 35.5% (for 0.5 Gy). In the therapeutic felds of parotid cancer radiotherapy at different points, the measured dose from EBT flm was higher than the EBT3 flm. In these felds the minimum and maximum measured dose differences were 16.0% and 25.5%, respectively. Conclusion: EBT flm demonstrates higher NOD than EBT3 flm. This effect may be related to the higher sensitivity of EBT flm over EBT3 flm. However, the obtained dose differences between these two flms in low dose range can be due to the differences in ftting functions applied following the calibration process.