Acceleration study of a BNCT dose calculation engine based on NECP-MCX

Boron Neutron Capture Therapy (BNCT) is an emerging cancer treatment modality where the Treatment Planning System (TPS) plays a critical role in optimizing neutron beam and boron compound dose distribution to target cancer cells while sparing healthy tissues. This paper presents the development of NECP-MCX-RT (radiation therapy), an accelerated Monte Carlo dose engine for BNCT TPS, adapted from the nuclear reactor simulation code NECP-MCX. Key innovations include a fast voxel geometry tracking algorithm that accelerates particle propagation by efficiently determining surface-crossing steps and entry directions, alongside a direct tally mechanism during transport to streamline dose calculations using voxel-specific track lengths. Additionally, a batch-based MPI parallel algorithm minimizes the inter-CPU communication overhead by deferring result summation. Validation against PHITS using a CT-based model demonstrated excellent agreement in dose distributions across tissues, with biases under 3%, while achieving a 21.91 times speedup over PHITS and an 11.97 times improvement over the original NECP-MCX in computational efficiency.