Medical Physics Companding technique for high dynamic range measurements using gafchromic films.

We propose a methodology to perform dose measurements using gafchromic films which can span several decades of dose levels. The technique is based on a rescaling approach using different films irradiated at different dose levels. This is combined with a registration protocol correcting positioning and scaling factors for each film. The methodology is validated using TLDs for out–of–field doses. Furthermore, an example is provided using the technique to characterize a small 7.5 mm sized radiosurgery cone and compared to measurements made with a pinpoint chamber. 1 a