The feasibility of in-beam PET for therapeutic beams of /sup 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 has been clinically implemented at the Gesellschaft fur Schwerionenforschung (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 ³ He has been studied for the first time at the Gesellschaft fur Schwerionenforschung (GSI) with three mono-energetic ³He-beams of 130.03A MeV to 207.92A MeV and mean intensities varying from 2.0middot10⁸ to 3.5middot10⁸ 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 ion induced positron activity will be presented and compared with data from ¹²C-irradiation. The accuracy and resolution for determining the range of the He 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