Feasibility of Prompt Gamma-Ray Imaging in BNCT: SPECT-Based MCNP Simulations of Boron and Hydrogen Capture Events

Background: Boron neutron capture therapy (BNCT) is a targeted radiotherapy that selectively destroys cancer cells by delivering compounds enriched in boron-10 ( 10 B) that preferentially accumulate in tumors.When exposed to low-energy neutrons, 10 B undergoes a nuclear reaction that produces high-linear energy transfer particles that kill adjacent tumor cells while sparing healthy tissues.Real-time monitoring of boron distribution and the neutron irradiation is critical to optimize treatment efficacy and minimize collateral damage. Materials and Methods:We evaluated a single-photon emission computed tomography (SPECT) configuration for simultaneous monitoring of boron spatial distribution and neutron irradiation patterns.Monte Carlo simulations were performed with the Monte Carlo N-Particle version 6.2 (MCNP6.2) using a male Oak Ridge National Laboratory stylized phantom.The simulations modeled prompt gamma emissions at 0.478 MeV (from 10 B neutron capture) and 2.2 MeV (from hydrogen neutron capture) and the detection response of a four-head cadmium zinc telluride (CZT) SPECT system. Results and Discussion:The SPECT system localized regions of boron uptake in the phantom using 0.478 MeV emissions with good spatial localization.Although the system detected 2.2 MeV gamma rays from hydrogen neutron capture, reconstructed images from this energy showed diffuse distributions and did not provide clear directional information about the neutron source.These findings indicate strong performance for boron mapping but limited capability for precise neutron-source directionality using 2.2 MeV gamma emissions in the present configuration. Conclusion:SPECT-based imaging with a CZT detector shows feasibility for real-time boron mapping in BNCT.However, further work on detector geometry, collimation, and reconstruction algorithms is needed to improve sensitivity at clinically relevant boron concentrations and to enhance directional sensitivity for neutron-field assessment.