Computer assisted film electron dosimetry: 3-D isodose curve

A method is presented which uses a hardware-software integrated system for the off-line acquisition, processing and restitution of radiographic images in order to obtain a complete set of 3-D isodose curves for high energy electron bearns. The image processing system is briefly illustrated and some examples of dose reconstruction are given. The system is automatic and operates in different stages; the most important of these stages are digital image acquisition, data preprocessing and image analysis and graphic and pictorial restitution. The system software structure mainly consists of interactive modules and procedures operating in interconnected environments. The equipment used to acquire the experimental data consists of a linear accelerator and a phantom composed of a number of polystyrene sheets. To detect the electron beams in the planes which are orthogonal with respect to the propagation direction, films were inserted between sheets of this phantom. The films were carefully aligned with respect to the central axis of the beam and were exposed singly. The X-ray films obtained have been digitized and processed. The results so far demonstrate that the method is accurate, quick and offers high resolution. It can thus be considered suitable for use both in the clinical routine and in the experimental testing of models obtained using conformation therapy.