Radiotherapy dose enhancement using {BNCT} in conventional {LINACs} high-energy treatment: Simulation and experiment

摘要

AbstractAim To employ the thermal neutron background that affects the patient during a traditional high-energy radiotherapy treatment for {BNCT} (Boron Neutron Capture Therapy) in order to enhance radiotherapy effectiveness. Background Conventional high-energy (15–25 MV) linear accelerators (LINACs) for radiotherapy produce fast secondary neutrons in the gantry with a mean energy of about 1 MeV due to (γ, n) reaction. This neutron flux, isotropically distributed, is considered as an unavoidable undesired dose during the treatment. Considering the moderating effect of human body, a thermal neutron fluence is localized in the tumour area: this neutron background could be employed for {BNCT} by previously administering 10B-Phenyl-Alanine (10BPA) to the patient. Materials and methods Monte Carlo simulations (MCNP4B-GN code) were performed to estimate the total amount of neutrons outside and inside human body during a traditional X-ray radiotherapy treatment. Moreover, a simplified tissue equivalent anthropomorphic phantom was used together with bubble detectors for thermal and fast neutron to evaluate the moderation effect of human body. Results Simulation and experimental results confirm the thermal neutron background during radiotherapy of 1.55E07 cm−2 Gy−1. The {BNCT} equivalent dose delivered at 4 cm depth in phantom is 1.5 mGy-eq/Gy, that is about 3 Gy-eq (4 of X-rays dose) for a 70 Gy {IMRT} treatment. Conclusions The thermal neutron component during a traditional high-energy radiotherapy treatment could produce a localized {BNCT} effect, with a localized therapeutic dose enhancement, corresponding to 4 or more of photon dose, following tumour characteristics. This {BNCT} additional dose could thus improve radiotherapy, acting as a localized radio-sensitizer.