Neutron spectrometry and determination of neutron ambient doses in radiotherapy treatments under different exposure conditions

摘要

A project has been set up to study the effect on a radiotherapy patient of the neutrons produced around the L1NAC accelerator head by photonuclear reactions induced by the gamma radiation above ~8 MeV. These neutrons may reach directly the patient, or they may interact with the surrounding materials until they become thermalised, scattering all over the treatment room and affecting the patient as well, contributing to the peripherical dose. Spectrometry was performed with a set of Bonner spheres at 50 cm from the isocen-ter and at the place where a digital device for measuring neutrons will be located the treatment room. Exposures have taken place in six linac accelerators with different energies (from 6 to 23 MV). A summary of the spectrometry results and of the neutron doses received by the patient is presented.