1496 poster NEUTRON CONTAMINATION MEASUREMENTS AT ITHEMBA LABS PROTONTHERAPY FACILITY.

Purpose: Proton and ion beams provide the possibility of highly conformal dose distributions with the potential of dose escalation. In addition, the integral dose delivered with protons and ions is significantly lower than with photon beams, which would imply a lower risk for radiation-induced cancers when using protons. However, the risk associated with undesired neutron production is not well understood. The purpose of this work is to study this production in order to estimate the dose received by the patient in a specific facility, no previously evaluated. Materials: A set of experiments has been performed to characterize the neutron production in the medical proton facility at iThemba Labs in South Africa. The same procedure already applied to conventional photon radiotherapy [1] has been followed. We used a digital detector [2] to measure the neutron dose at a location inside the room (near room wall, figure 1) in different irradiations of an anthropomorphic phantom to study dependences on beam energy and target volume size and depth.