IMRT beam angle optimization using differential evolution

Radiation therapy is one of the main treatments against cancer. Intensity Modulated Radiation Therapy (IMRT) is one type of radiation therapy that allows a high degree of conformity between the radiation intensities and the areas to treat. The planning of a radiation treatment for a given patient is crucial for obtaining the desired goals (being able to destroy cancer cells while preserving the healthy ones). In clinical practice, treatment planning is most of the times based on a lengthy trial-and-error procedure during which the planner interacts with a treatment planning system trying to find a treatment that complies with the medical prescription. One of the first decisions the planner has to make is on the angles to be used to deliver radiation. In clinical practice, most of the times, the number of angles to be used is defined a priori based on the experience of the planner with similar cases. Often, the solution that is used is the equidistant solution, where all angles are equally apart. In this paper we propose the use of Differential Evolution (DE) for determining in an automated way the set of angles that should be used in a given IMRT treatment. Solutions obtained after the DE optimization are then compared with the equidistant solution. Preliminary results considering ten already treated patients at the Portuguese Institute of Oncology of Coimbra IPOCFG are presented.