Optimization of proton and heavy ion therapy using an adaptive inversion algorithm

Abstract

In order to fully utilize the dose distributional advantages of pions, protons and heavy ions it is important to cover the target volume as well as possible by Bragg peaks and avoid irradiating surrounding organs at risk. The most general way to achieve this goal is by modulation of the range of the beam so that its Bragg peak falls exclusively in the target volume. This could only be achieved using a threedimensional scanning technique where an elementary pencil beam is scanned not only transverse to the central axis of the beam, but also along the longitudinal or depth axis which is approximately parallel to the central axis (cf. Fig. 1). The transverse scanning could be performed by an electromagnetic or mechanical scanning system whereas the longitudinal scanning could be done using variable energy extraction from the accelerator. Alternatively a variable beam energy absorber could be used in the treat-