Characterisation of gafchromic EBT2 film for use in radiation therapy dosimetry

This study characterised the dosimetric properties of a new Gafchromic film EBT2. The suitability of this film as an Intensity Modulated Radiation Therapy (IMRT) treatment plan verification dosimeter was also investigated. In accurately determining the absolute dose delivered to the film, both the film and scanner used to digitise the images needed to be characterised. Characterisation of the Gafchromic EBT2 film included investigating fundamental properties such as its energy dependence, uniformity, absorbance spectra and acquiring a sensitometric curve. The study also examined the effects of ambient room light, fractionating the dose and cutting the film. To ensure accurate readings of the film the scanner used, the Epson Expression 10000XL, needed to be properly characterised. The light-scattering effect, the heating effect of the lamp and the polarisation effect of the film were measured. The optimal resolution setting of the scanner was also investigated. To evaluate the films ability to verify IMRT treatments, properties such as dose rate dependence and fractionating the dose were investigated. An IMRT plan was also created and its dose distribution delivered to the film. The calculated dose distribution and the dose distribution delivered to the film were evaluated with Gamma Analysis using Radiological Imaging Technology (RIT, 2004) software.