The feasibility of in-beam PET for therapeutic beams of 3 He

At present in-beam PET is the only possibility for an in-situ monitoring of the particle delivery in hadron tumor therapy and there is a unique clinical implementation at the Gesellschaft fuer Schwerionenforschung (GSI) Darmstadt.
Several heavy ion treatment facilities are under construction, which will provide a large variety of ions from protons to oxygen. This requires a precise knowledge of the spatial distribution of beam induced positron emitters in the irradiated volume. For the 3He-case experiments at GSI with three mono-energetic 3He-beams of 130.03 AMeV to 207.92 AMeV have been carried out. The beams were stopped in homogeneous thick targets consisting of PMMA, graphite and water. Results on the production rate and the spatial distribution of 3He ion induced beta+-activity will be presented and compared with data from 12C-irradiation. From these, the accuracy and resolution for determining the range of the 3He primary beams is deduced. Furthermore, energy dependent thick target cross sections for different reaction channels leading to positron emitters will be estimated from the experimental data.