Analysis of film response to electron beams using a laser scanner system developed in the laboratory

An optical scanner system, which incorporates a He–Ne laser, photodiode detectors, and a platform for placing film, was built in the laboratory. The laser system operates at the green wavelength of 543.5 nm and functions as a scanning densitometer for measurement of optical changes in a film resulting from irradiation .The central axis electron depth dose of selected electron energies 10,12 and 14 MeV were analysed using Kodak X-Omat and Kodak Extended Dose Range (EDR2) films. The Kodak X-Omat film is routinely used for high-energy electron dose distributions in radiation therapy. The electron depth–dose measured with X-Omat film was found to agree well with standard depth–dose curves in water, obtained using an ion chamber. Conversely, the recently introduced Kodak EDR2 showed an energy dependence for electron beams, the percentage depth–dose curve shifting towards the surface for 12 and 14 MeV electron beams compared to that in water.