A SPHERICAL DOSE MODEL FOR RADIOSURGERY PLAN OPTIMIZATION

Conventional 3D dose calculations for stereotactic radiosurgery involv e integration of individual static beams comprising a set of arcs. For iterative optimization of multiple isocentre treatment, which require s repetitive dose calculations at a large number of sample points, the conventional method is too slow. To overcome this problem spherically symmetric dose distributions are assumed. The authors describe a sphe rical dose model derived from a parametrized convolution of the collim ator width and a dose spread kernel. The method is fast and easy to im plement requiring just a single empirically derived value. Furthermore , the model is differentiable with respect to the parameters to be opt imized. This property is useful when the optimization strategies rely on gradient information.