Radioprotection aspects of protontherapy

Proton radiation therapy is increasingly used in cancer treatment because its capacity to spare normal tissues from unnecessary radiation is better than external-beam photon radiation therapy. From the radioprotection point of view a proton accelerator produces stray radiation and in particular secondary neutrons which must be shielded with thick bunker walls and ceiling but which produce also activation of materials. The activation concerns materials along the beam line but also air and water interacting with secondary neutrons. In particular the material's activation and the stray radiation in the therapy bunkers need to be estimated for risk evaluation of patients and operators. The aim of this paper is to report some radioprotection aspects concerning protontherapy in order to fulfil the requirements of Italian Regulatory Authorities in particular those regarding disposals in the environment.