RAD7- Seventh International Coference on Radiation in various fields of research, Herceg Novi, Montenegro, 10 - 14 June 2019, vol.135, pp.136
Radiochromic film dosimetry has been commonly used for determination of dose measurement in radiotherapy for many years because of their high spatial resolution, low energy dependence and its approximate tissue equivalent. Additionally it has other advantages, e.g. a water resistance material and a relatively insensitive to visible light. Hence they are very useful and practical for clinical applications such as brachytherapy, electron therapy and skin dose measurements. Among them, the dynamic dose range of EBT3 radiochromic films are generally recommended for the dose range of 0.1 to 20 Gy. However, in this study, it is aimed to observe the behavior of EBT3 films in high dose range of up to 90 Gy under the irradiations. For this aim, the net optical outputs were obtained with increasing dose values under photon and electron beams by employing three colors scanning channels (red-green-blue). Thus, for making calibration curves, it was decided which color channel for EBT3 radiochromic film would be the most suitable one in different dose ranges.
In the setup, the reference conditions were first established and dose calibration procedure was carried out in RW3 phantom. Then the irradiated films were cut into 2x2.5 cm2 pieces and they were grouped into 2 as irradiation and control groups. The control group wasn’t irradiated. Before the irradiation, two groups of films have been scanned in flatbed scanner. After that, the irradiation group films were placed to align the exact place of effective point of ionization chamber under the reference condition. Later, they were irradiated one by one to up to 90 Gy with using 6 MV and 6 MeV beam qualities, respectively. Subsequently, both of film groups were again scanned in flatbed scanner.
Optical densities and their standard deviations corresponding to the chosen dose values were obtained from the scanned films. Thus calibration curves were plotted for all three colors channels according to two different beam conditions. The results obtained for 6 MV beam quality showed that if red color channel is selected for the dose range of 0.8 Gy-7.3 Gy, and green color channel is selected for 7.3 Gy-42 Gy, and blue color channel is selected for 42 Gy-90 Gy the percentage errors in the obtained results are minimal.
In conclusion, the percentage errors for the obtained results were evaluated for 6 MV photon and 6 MeV electron energies by using different scanning channels of EBT3 radiochromic film. It has been found that measurements having low percentage error values can be achieved by using the scanning channels of their proper combinations with increasing doses for both energies. The study also shows that EBT3 radiochromic films can be used at lower error values at doses higher than the recommended dose range values.