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

At the clinical heavy ion treatment facility, which is under construction in Heidelberg, beams of He will also be used for tumour irradiation. These will be moni- tored by means of in-beam PET for quality assurance. This requires a precise knowledge of the spatial distribu- tion of beam induced positron emitters in the irradiated volume. For this an experiment at the Gesellschaft fur Schwerionenforschung (GSI) with pencil-like 3 He-beams of 130:03 AMeV to 207:92 AMeV and mean intensities vary- ing from 2:0 10 8 to 3:5 10 8 ions/s has been carried out. The data were taken in list-mode, the PET-measurement was performed over 10 min of irradiation and 20 min of decay. The beams were stopped in homogeneous thick tar- gets consisting of PMMA (C5H8O2, 9 9 20 cm 3 , = 1:18 g cm 3 ), graphite (9 9 15 cm 3 , = 1:795 g cm 3 ) and solid water targets (9 9 20(30) cm 3 , = 1:0 g cm 3 ). These consist of water with gelatine resulting in a stoichio- metric composition of H66:2O33:1C0:7. The spatial distribu- tions of the imaged + -activity are displayed in Fig. 1.