The Feasibility of In-Beam PET for Therapeutic Beams of He

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 by ³He has been studied for the first time at the Gesellschaft fur Schwerionenforschung with three mono-energetic ³He beams of 130.03 AMeV to 207.92 AMeV and mean intensities varying from 2.0middot10⁸ to 3.5middot10 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 ³He ion induced positron activity is presented and compared with data from ¹²C-irradiation. 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 are estimated from the experimental data