Evaluation of Dose Rate and Photon Energy Dependence of Gafchromic EBT3 Film Irradiating with 6 MV and Co 60 Photon Beams
Gafchromic films are utilized for two dimensional dose distribution measurements, especially in radiotherapy. In this study, we investigated a close connection between energy and dose rate of Gafchromic EBT3 films irradiating with 6 MV and Co 60 photon beams over a broad dose range. EBT3 films were exposed to 6 MV and Co 60 photon beams using 4 and 2 Gy/min dose rates over a 10 400 cGy dose range. The films were scanned in red, green, and blue channels to obtain the optical density (OD) dose curves. The OD dose curves resulted from three color scans for different photon energies and dose rates were compared by statistical independent t test. For the radiations of Co 60 and 6 MV photon beams, the highest correlation was obtained between the 2 and 4 Gy/min dose rates with red and green channels, respectively. Moreover, the red channel had a greater OD response per dose value, following the green and blue channels. There was no significant difference between different photon energies' (Co 60 and 6 MV) and dose rates' (2 and 4 Gy/min) dependence on OD dose response of EBT3 films over a broad domain of radiation dose, except for different photon energies in the blue channel. Our results revealed that the OD dose response of EBT3 films is independent on photon energies (Co 60 and 6 MV) and dose rate (2 and 4 Gy/min) in the evaluated dose range (10 400 cGy) Therefore, the EBT3 films are suitable, consistent, and reliable instruments for dose measurements in radiotherapy.
Journal of medical signals and sensors