Monte Carlo-Based Feasibility Study of Large-Area 2D Micromegas Detector for Real-Time Beam Monitoring In Boron Neutron Capture Therapy
Abstract
Purpose
Boron Neutron Capture Therapy (BNCT) centers are rapidly increasing worldwide due to recent clinical trials and accelerator-based neutron irradiation systems. However, unlike external photon irradiations, BNCT lacks real-time neutron beam monitoring for quality assurance. We propose a large-area (radius >6 cm), high-resolution (2 mm) 2D neutron imaging method with high neutron counting rates (94 kHz/channel) and report results from a Monte Carlo (MC)-based virtual clinical trial (VCT) of the proposed system. BNCT, the imaging system, and a 3D patient phantom are evaluated to assess the feasibility of the proposed real-time BNCT beam monitoring system.
Methods
We establish a VCT simulation platform based on Geant4 v11.4.0, modeling a beam shaping assembly (BSA) that emits neutrons and photons according to IAEA parameters. The neutron monitoring system consists of a Micromegas detector mounted at the BSA beam port. Simulations evaluate neutron fluence rates, energy spectra, and photon doses in target regions of a 3D patient phantom and organs at risk (OARs). Potential neutron beam attenuation caused by the detector is assessed by tracking neutron activation in the BSA, detector, and patient body, including secondary radionuclides, decay products, and resulting doses to patients and staff.
Results
DVH analysis demonstrates minimal neutron beam perturbation, with a slight increase in treatment time but unchanged gross tumor volume (GTV) and organ-at-risk doses, indicating adequate beam transparency. Imaging materials are optimized to improve system performance. Patient and staff radiation safety complies with IAEA and ICRP recommendations. Five-year radiation damage to the imaging detector is simulated to assess system durability.
Conclusion
This study follows the VCT concept recently recommended by the U.S. FDA. The results provide essential data for real-time BNCT beam monitoring prior to and during treatment, addressing neutron beam transparency and activation effects, and form the basis for manufacturing real-time 2D beam monitoring systems for BNCT.