3-DIMENSIONAL OPTIMIZATION OF MULTIPLE ARCS FOR STEREOTAXIC RADIOSURGERY

Purpose: During linear accelerator-based radiosurgery, the physicians and physicists need to determine which combination of treatment arcs a re ''best'' with regard to target coverage and incidental dose to adja cent structures. This is a complex problem, especially when targets ar e geometrically close to critical structures. The purpose of this arti cle is to present a method to mathematically determine a set of arcs t o produce desired target and normal structure dose distributions in li near accelerator radiosurgery. Methods and Materials: Nonlinear least squares regression was used to determine the table angles and gantry a ngle arc ranges and their associated beam weights appropriate to linea r accelerator radiosurgery. Results: Three cases are presented: (a) cr itical structure close to target volume; (b) target volume too large f or the largest collimator to cover the volume with one isocenter and a standard plan; (c) target volume located within one critical structur e and close to another critical structure. The optimized treatment pla ns are all shown to be superior to a defined standard plan. Conclusion : The method successfully enables one to determine nonstandard arcs wh ich achieve the desired results. In particular, the method enables one to find clinical treatment solutions, even when the desired results c annot be a priori defined.