Speaker
Description
The generation of secondary neutron fields in proton therapy treatments is a major concern because of the exposure of patients and staff to incidental dose. Even if current Pencil Beam Scanning techniques minimize neutron production compared to passive scattering, the risk of secondary cancers due to stray neutron dose—especially in paediatrics’—remains non-negligible. Many studies have investigated stray neutron radiation in proton therapy environments by performing Monte Carlo simulations, showing that a reliable assessment of potential neutron doses can be achieved when accounting for all the factors that affect the generation of neutrons and their interactions with the treatment facility.
This work evaluates four independent methodologies based on Monte Carlo simulations with MCNP to estimate the ambient dose equivalent H(10) due to secondary neutrons in a proton therapy treatment room. The first approach captures the neutron fluence spectrum and calculates H(10) via fluence-to-ambient-dose conversion coefficients. The second approach estimates H(10) by computing the absorbed dose and converting it to ambient dose equivalent. The third and fourth approaches incorporate mesh-based realistic designs of an extended-range Bonner Sphere Spectrometer (ERBSS) and a WENDI-II detector in order to replicate, through simulations and relying on the detector responses, the experimental measuring process and estimate H(10).
The methodologies were compared at different relevant positions in a mesh-based Monte Carlo model of a real proton therapy treatment room that includes all the main scattering surfaces influencing the secondary neutron field. The results contribute to a better understanding of secondary neutron production and distribution in proton therapy environments.