An Optimization Framework for Conformal Radiation Treatment Planning

An optimization framework for three-dimensional conformal radiation therapy is presented. In this type of therapy, beams of radiation are applied to a patient from different directions, where the aperture through which the beam is delivered from each direction is chosen to match the shape of the tumor, as viewed from that direction. Given a set of equispaced beam angles, a mixed-integer linear program can be solved to determine the most effective angles to be used in a treatment plan, and the weight (exposure time) to be used for each beam. This model can be enhanced to account for the use of wedge filters, which may be placed in front of a beam to produce a gradient in beam intensity across the aperture. Several techniques for strengthening the formulation (and therefore reducing the solution time) are described, and methods to control the dose-volume histogram implicitly for various parts of the treatment region using hotand cold-spot control parameters are presented. The paper concludes with computational results that show the effectiveness of the proposed approach on two practical data sets.