The Influence of Dose Grid Resolution on Beam Selection Strategies in Radiotherapy Treatment Design

The design of a radiotherapy treatment includes the selection of beam angles (geometry problem), the computation of a fluence pattern for each selected beam angle (intensity problem), and finding a sequence of configurations of a multilef collimator to deliver the treatment (realization problem). While many mathematical optimization models and algorithms have been proposed for the intensity problem and (to a lesser extent) the realization problem, this is not the case for the geometry problem. In clinical practice, beam directions are manually selected by a clinician and are typically based on the clinician’s experience. Solving the beam selection problem optimally is beyond capability of current optimization algorithms and software. However, heuristic methods have been proposed. In this paper we compare various heuristic approaches on a clinical case. In particular, we study the influence of dose point resolution on the performance of these heuristics. We also compare the solutions obtained by the heuristics with those achieved by a clinician using a commercial planning system.