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.