CONFORMAL RADIOTHERAPY COMPUTATION BY THE METHOD OF ALTERNATING PROJECTIONS ONTO CONVEX-SETS

Synthesis of beam profiles for a given dose prescription is a central problem in radiotherapy. Care must be taken in the beam design to expo se the tumour volume at a high level, to avoid significant irradiation of critical organs, and to minimize exposure of all other tissue. Use of the synthesis procedure known as alternating projections onto conv ex sets (POCS) is shown to be a viable approach to beam design. POCS i s a powerful tool for signal and image restoration and synthesis. Conv ex sets of signals obeying desired constraint sets are first specified . Then, by repeated projections onto these sets, convergence is to a s ignal obeying all desired constraints if the constraint sets have a fi nite intersection. In this paper we apply the method of POCS to confor mal radiotherapy dose computation. The performance of the method is sh own through three representative examples.