A Study On Optimization Of Beam Orientations And Beam Weights For Conformal Radiotherapy

Objective: The goal of radiotherapy is to deliver a required dose to the planning target volume (PTV) while minimizing the doses to adjacent organs at risk (OARs) and other normal tissues. During the planning procedure of conformal radiotherapy, one important step is to select appropriate beam orientations and the number of beam orientations. In current clinical practice, this step is manually finished by a planner according to his (her) experiences. Working in this way may take much time and result in an acceptable, but not necessarily optimal configuration of beam orientations, especially when multiple non-coplanar beams are considered. An algorithm for optimizing beam orientations and beam weights for conformal radiotherapy has been developed to solve this problem, and then this new algorithm is employed to answer the question which is the most suitable number of beam orientation in noncoplanar radiation therapy for brain tumors. Methods: In the first part of this study, the algorithm models the optimization of beam orientations and beam weights as a problem of mixed integer linear programming (MILP), and optimizes the beam orientations and beam weights simultaneously. The application procedure of the algorithm has four steps: a. prepare a pool of beam orientation candidates with consideration of avoiding any patient-gantry collision and avoiding direct irradiation of OARs with quite low tolerances (e.g., eyes); b. represent each beam orientation candidate with...