Treatment Planning and Optimization for Internal Boron Neutron Capture Therapy for Glioblastoma
Abstract
Purpose
To develop and evaluate a treatment planning and optimization framework for internal boron neutron capture therapy (internal BNCT) using a miniaturized neutron tube for the treatment of glioblastoma, and to quantify its dosimetric performance relative to photon-based volumetric modulated arc therapy (VMAT).
Methods
A patient-specific internal BNCT planning framework was developed using Monte Carlo-based dose modeling of a miniaturized neutron tube positioned within the glioblastoma resection cavity, combined with inverse optimization of multiple source dwell positions. Dose distributions were converted to biologically weighted dose (Gy-Eq) using established relative biological effectiveness (RBE) factors. Infiltrative glioblastoma spread was modeled using concentric target subregions with spatially varying boron concentrations extending beyond the resection margin. Multi-dwell source configurations were optimized to satisfy dose-volume constraints on the planned target volume (PTV) and surrounding organs at risk (OARs), including the left hippocampus and optic nerve.
Results
Optimized multi-dwell internal BNCT plans using the miniaturized neutron tube achieved conformal target coverage across the PTV and infiltrative tumor regions while maintaining OAR doses within clinically acceptable limits. Compared to VMAT, internal BNCT demonstrated a steeper dose falloff beyond the target region,with a ~60% reduction in normal brain median dose (D50 = 14% vs. 36% of prescription). Tumor dose coverage was preserved across all modeled infiltration regions despite heterogeneity in boron concentration. DVH analysis confirmed improved tumor-to-normal dose ratios for internal BNCT relative to VMAT.
Conclusion
Patient-specific optimization of multi-dwell internal BNCT enabled tumor-specific dose delivery to infiltrative glioblastoma regions extending beyond the resection cavity while limiting dose to surrounding normal brain. Compared with VMAT, internal BNCT achieved improved tumor-to-normal dose ratios. These results indicate that internal BNCT may provide a viable treatment planning strategy for targeting infiltrative cancer cells that are challenging for external beam-based BNCT and photon-based radiotherapy relying on a clearly defined target.