Implementation of a real-time neutron monitor system for use in routine quality assurance of an accelerator-based neutron system for clinical boron neutron capture therapy.

BACKGROUND

Currently, the metal foil activation method is routinely used to measure the neutron output of an accelerator-based neutron source designed for clinical Boron neutron capture therapy (BNCT). Although this method is well established and has been primarily utilized since the nuclear reactor BNCT era, the process is labour-intensive and not well-suited for a busy hospital environment performing routine patient treatment. A replacement neutron detector system that is simple to use and can measure the neutron output in real-time is necessary.

PURPOSE

Investigation and implementation of an Eu doped LiCaAlF scintillator detector for use in routine quality assurance tests of an accelerator-based neutron source designed for clinical BNCT.

METHODS

The response of the scintillator detector was evaluated using the NeuCure BNCT system installed at the Kansai BNCT Medical Center. The measurement repeatability, neutron fluence linearity, and neutron flux dependency of the detector system were evaluated. The beam central axis and off-axis thermal neutron distribution inside a water phantom were measured and compared with the Monte Carlo treatment planning system (TPS).

RESULTS

The scintillator detector system showed high measurement repeatability with a coefficient of variation of less than 0.4%. The detector system showed linear response up to a proton charge of 3.6 C, and the response was stable between a proton current of 0.1 and 1 mA. Both the central axis and off-axis thermal neutron flux inside a water phantom matched closely with both the metal foil activation method and the Monte Carlo simulation results. The time it took to perform a routine quality assurance test was drastically reduced from 1.5 h down to a few minutes.

CONCLUSION

Implementation of this detector system in the clinic would significantly reduce the time required for routine QA, acceptance, and commissioning, and be a stepping stone to assist expansion of accelerator-based BNCT systems worldwide.