The Feasibility of In-Beam PET for Therapeutic Beams of³He

At the experimental carbon ion treatment facility at the Gesellschaft fur Schwerionenforschung (GSI) Darmstadt the clinical benefit of the in-beam PET method has been proven. It led to a significant improvement of the quality of patient treatment. Several heavy ion treatment facilities, which will provide in the near future a large variety of ions, 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 by3He has been studied for the first time at the Gesellschaft fur Schwerionenforschung with three mono-energetic3He beams of 130.03 AMeV to 207.92 AMeV and mean intensities varying from 2.0middot108to 3.5middot108ions/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 of3He ion induced positron activity is presented and compared with data from12C-irradiation. The accuracy and resolution for determining the range of the3He primary beams is deduced. Furthermore, energy dependent thick target cross sections for different reaction channels leading to positron emitters are estimated from the experimental data