Clinical evaluation of performance, stability, and longevity of an accelerator system designed for boron neutron capture therapy utilising a beryllium target

Boron neutron capture therapy for recurrent head and neck cancer has been approved as an insurance covered treatment in Japan since June 2020. The Kansai BNCT Medical Center has installed the NeuCure (R) BNCT system developed by Sumitomo Heavy Industries. This system utilises a beryllium target with a 30 MeV proton beam to generate neutrons. To date, the center has treated over 300 patients and the system is also used for quality control and fundamental research experiments. Information on the stability and longevity of the system is important for facilities and hospitals considering installation of a BNCT system in the future, particularly after an exchange of a major component, such as the target. The beam output (neutron and gamma ray) was measured before and after the exchange of the target. The thermal neutron, fast neutron and gamma ray distribution inside a water phantom was evaluated and the results showed no significant change in the beam quality after the exchange of the target. Furthermore, no significant change in the neutron flux as a function of increasing number of accumulated protons on the target was observed up to a value of just under 400 mAh. The NeuCure (R) BNCT system has been shown to be highly stable and the frequency of target replacement was much less than lithium target-based accelerators.