Conformal irradiation for moving targets in heavy ion radiotherapy with raster-scanning beam delivery system (I) simulations

Within the framework of the pilot heavy-ion therapy facility at GSI equipping an active beam delivery system of advanced raster scanning technique, the investigation of actively conformal irradiation to moving tumors using heavy ions is underway. The influences of target motion on dose homogeneity and conformity degree were theoretically studied under the condition of the active raster-scanning beam delivery system. The relationship between the target motion with different patterns and the uniformities of doses delivered by the raster scanner to different iso-energy slices of the moving target were simulated with an experimentally measured beam spill. Several strategies improving the dose homogeneity in the moving target volume were derived from these simulation results. The simulations presented in this paper provide an effective means for evaluating the dose distribution for a moving target, and the results and implications of this theoretical work establish a substantial basis for feasibility experiments of the compensation for target motion with the active raster scanner at GSI. (authors)