Energy dependence of radiochromic dosimetry films for use in radiotherapy verification
Abstract
Aim
The purpose of the study was to examine the energy dependence of Gafchromic EBT radiochromic dosimetry films, in order to assess their potential use in intensity-modulated radiotherapy (IMRT) verifications.
Materials and methods
The film samples were irradiated with doses from 0.1 to 12[[ce:hsp sp="0.25"/]]Gy using photon beams from the energy range 1.25[[ce:hsp sp="0.25"/]]MeV to 25[[ce:hsp sp="0.25"/]]MV and the film response was measured using a flat-bed scanner. The samples were scanned and the film responses for different beam energies were compared.
Results
A high uncertainty in readout of the film response was observed for samples irradiated with doses lower than 1[[ce:hsp sp="0.25"/]]Gy. The relative difference exceeds 20% for doses lower than 1[[ce:hsp sp="0.25"/]]Gy while for doses over 1[[ce:hsp sp="0.25"/]]Gy the measured film response differs by less than 5% for the whole examined energy range. The achieved uncertainty of the experimental procedure does not reveal any energy dependence of Gafchromic EBT film response in the investigated energy range.
Conclusions
Gafchromic EBT film does not show any energy dependence in the conditions typical for IMRT but the doses measured for pre-treatment plan verifications should exceed 1[[ce:hsp sp="0.25"/]]Gy.
Keywords: Radiochromic filmsQuality assuranceFilm dosimetry