Beam Orientation Optimization For Intensity-modulated Radiation Therapy

Objective: To develop a beam orientation optimization algorithm for intensity-modulated radiation therapy (IMRT), and to explore the influence of beam orientation resolution and starting orientation on the optimized beam configuration, plan quality and optimization time. Methods: The algorithm is based on mixed integer linear programming in which binary and positive float variables are employed to represent beam orientation candidates and beamlet weights in beam intensity maps respectively. Both beam orientations and beam intensity maps are simultaneously optimized in the algorithm with a deterministic method. Results: Both target coverage and critical structures sparing were significantly improved using this algorithm for tested cases, decreasing beam orientation resolution to 10°greatly reduced the optimization time without significant influence on plan quality, while selecting different starting orientations had large influence. The calculation time was about an hour for the cases with 36 binary variables on a PC with a PentiumⅣ2.66 GHz processor. Conclusions: This algorithm is potentially applicable in clinic, and better beam orientation configurations can be obtained. The optimization efficiency can be greatly improved through proper selection of beam orientation resolution and the starting beam orientation while guaranteeing the optimized beam configurations and plan quality.