Background: EBT and EBT3 radioChromic films have been used in radiotherapy
dosimetry for years.
Objective: The aim of the current study is to compare EBT and EBT3 radioChromic
films in dosimetry of radiotherapy fields for treatment of parotid cancer.
Methods: Calibrations of EBT and EBT3 films 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)
fields by EBT and EBT3 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 EBT3
film. The minimum difference between these two films 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 fields of parotid cancer radiotherapy at different points, the measured
dose from EBT film was higher than the EBT3 film. In these fields the minimum and
maximum measured dose differences were 16.0% and 25.5%, respectively.
Conclusion: EBT film demonstrates higher NOD than EBT3 film. This effect may
be related to the higher sensitivity of EBT film over EBT3 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