Photoneutron production in advanced techniques radiation therapy: A review

Neutron contamination in the application of modern techniques in radiotherapy raises an issue in radiation protection for both patients and radiation workers. A higher number of monitor units increases the equivalent neutron dose. However, the high energy applied to improve the effectiveness of treatment contributes to the production of neutron contamination. Neutron contamination with a considerable radiation weighting factor must be taken into account to minimise the stochastic effect. Good judgement in choosing the treatment modality is necessary to minimise the secondary radiation from neutrons. This literature review discusses the production of photoneutrons in three aspects, namely the linear accelerator (linac) intrinsic factor, the extrinsic factor originating from the shielding bunker and the operating mode of the linac or treatment planning technique.