Use of shape for automated, optimized 3D radiosurgical treatment planning

Abstract

Conformal treatment planning for radiosurgical dose delivery is challenging for irregularly shaped target volumes. Spheres of radiation dose, called “shots”, must be positioned within a target image to yield an acceptable cumulative dose distribution. An automated solution has been developed that uses target shape, as represented by the 3D medial axis transform, to determine optimal shot positions, sizes, and number. These parameters are determined from successive 3D skeletons of unplanned target volumes. Essentially, target shape is replicated by the arrangement of shots comprising the 3D skeleton, forcing a conformal solution. Optimization is determined by the ratio of uncovered to total target volume and the smallest number of shots. Use of the medial axis transform reduces a 3D optimization problem to 1D with corresponding savings in computation time. Clinical cases in 3D demonstrate this approach as a replacement for manual planning.