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Description
Proton Therapy techniques are recommended to treat tumours in paediatric patients because they can deliver high dose levels to the target volume while sparing dose to surrounding healthy tissues and growing organs, reducing the probability of unwanted secondary effects. However, during proton therapy treatments secondary neutrons are generated in the patient and in the room components, resulting in a whole-body dose exposure and raising concerns about potentially secondary effects due to those neutrons, especially in children. Even with pencil beam scanning, which minimizes neutron production compared to passive scattering, these risks remain non-negligible and assessing the secondary stray doses is essential. As it is not possible to conduct in vivo organ dose measurements, Monte Carlo simulations using computational phantoms become a useful tool to assess the affection to healthy organs and tissues.
In this work, Monte Carlo simulations with MCNP are performed using meshed geometries throughout to assess the organ dose exposure in an ICRP 10-year-old paediatric phantom during a pencil beam scanning proton therapy treatment. The study employs +F6 tally registers to quantify particle fluence and convert it into organ-equivalent doses, enabling a detailed analysis of the three-dimensional dose distribution. This combines a mesh-based Monte Carlo model of a real proton therapy treatment room—including all components and scattering surfaces affecting neutron transport—with a positioned paediatric phantom, enabling realistic estimation at multiple organ sites.
In this study a computational tool has been developed to identify, in the clinical setting, the organs most affected by unwanted neutron doses. This tool also enables medium- and long-term epidemiological studies on the probability of secondary cancer induction in paediatric patients.