PET monitoring of hadrontherapy

Imaging techniques for in-vivo verification of the ion beam range and treatment delivery are increasingly receiving a considerable attention, as they hold the promise to enable full clinical exploitation of the improved tumour-dose conformality offered by ion beams. Although promising novel techniques have recently been proposed and are being investigated in fundamental pre-clinical research, Positron-Emission-Tomography (PET) still offers the only technically feasible method for a volumetric non-invasive verification of the ion treatment during or shortly after daily dose delivery. This contribution discusses examples of clinical implementation of PET imaging, with special focus on the experience in in-beam and offline monitoring of carbon ion and proton therapy at the GSI Helmholtzzentrum fur Schwerionenforschung in Germany, the Massachusetts General Hospital in USA, and the Heidelberg Ion Beam Therapy Center in Germany. In particular, it highlights the encouraging clinical results but also the encountered major limitations. Finally, it addresses the most promising ongoing developments aiming to achieve optimal exploitation of the surrogate PET signal for in-vivo quality assurance of high precision ion beam therapy.