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

At present in-beam PET is the only possibility for an in-situ monitoring of the particle delivery in hadron tumor therapy and has been clinically implemented at the Gesellschaft fur Schwcrionenforschung (GSI) Darmstadt. Several heavy ion treatment facilities, which will provide a large variety of ions from protons to oxygen, are in planning or even under construction. The deduction of clinically relevant parameters from in-beam PET data requires a precise knowledge of the spatial distribution of beam induced positron emitters in the irradiated volume.. Therefore, the beta(+)-activity induced by He-3 has been studied for the, first time at the Geselischaft fur Schwerionenforschung (GSI) with three mono-energetic He-3-beams of 130.03 AMeV to 207.92 AMeV and mean intensities varying from 2.0 center dot 10(8) to 3.5 center dot 10(8) ions/s. The beams were stopped in homogeneous thick targets consisting of PMMA, graphite and water, which were placed in the center of the field of view of the PET-scanner at the experimental carbon ion therapy at GSI. Results on the production rate and the spatial distribution of He-3 ion induced positron activity will be presented and compared with data from C-12-irradiation. The accuracy and resolution for determining the range of the He-3 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.