Comparison of Different Strategies for Arc Therapy Optimization

Abstract

Radiotherapy (RT) has seen considerable changes in the last decades, offering an increased range of treatment modalities to cancer patients. Volumetric Modulated Arc Therapy (VMAT), one of the most efficient RT arc techniques, particularly with respect to dose delivery time, has recently considered noncoplanar arc trajectories while irradiating the patient, thanks to technological advances in the most recent generation of RT systems. In a preliminary work we have proposed a two step optimization approach for noncoplanar arc trajectory optimization (ATO). In this paper, treatment plans considering 5-, 7-, 9-, 11- and 21-beam ensembles in the first step (optimal selection of noncoplanar irradiation directions) of the proposed approach are compared to assess the trade-o s between treatment quality and computational time required to obtain a noncoplanar VMAT plan. The different strategies were tested resorting to a head-and-neck tumor case already treated at the Portuguese Institute of Oncology of Coimbra (IPOC). Results obtained presented similar treatment quality for the different strategies. However, strategies that consider a reduced number of beams in the first step clearly outperform the other strategies in terms of computational times. Results show that for a similar tumor coverage, treatment plans with optimal beam irradiation directions obtained an enhanced organ sparing.