Computer simulations concerning influence of target motion on dose distribution delivered by the GSI raster scanner

Target motion is a very big problem in conformal radiotherapy (CRT), especiallly for a charged particle beam because of its less lateral scattering and sharp Bragg peak. In the pilot project of the heavy-ion cancer therapy at GSI, patients with head and neck tumors are treated with a magnetic raster scanner[1]. However, if the raster scanner is used to treat patients with body tumors, motion of tumors is present in the lung, breast, liver, kidney and other disease sites, e.g. due to respiration. Therefore, applying the static dose optimization schemes[2] to the moving target by the advanced beam scanning technique could lead to a inhomogeneous dose distribution. So computer simulations about target motion were performed and Gaussian beam profile and sinusoidal movement are assumed as follows,