Morphology-guided radiotherapy treatment planning and optimization

In gamma unit radiosurgery treatment planning, dose delivery is based on the unit 'shot,' a distribution of dose approximately spherical in shape. Multiple shots are used to cover different parts of a given target region. Effective 3D optimization for gamma unit treatment has not been previously reported. In this article, a novel optimization method is introduced based on medial axis transformation techniques. Given a defined target volume, the target's medial axis, which uniquely characterizes the target, is used to determine the optimal shot positions and sizes. In using the medial axis, the 3D optimization problem is reduced to a 1D optimization, with corresponding savings in computational time and mathematical complexity. In addition, optimization based on target shape replicates and automates manual treatment planning, which makes the process easily understandable. Results of optimal plans and the corresponding dose distributions are presented. The relationship between skeleton disks and the dose distributions they predict are also discussed.