Heterogeneous head phantom for validating treatment planning system in boron neutron capture therapy

Area of Science:

• Medical Physics
• Radiation Oncology
• Nuclear Engineering

Background:

• Clinical boron neutron capture therapy (BNCT) relies on accurate dose calculations by treatment planning systems (TPS).
• Experimental validation of TPS dose predictions in heterogeneous media, like the human head, is crucial for patient safety and treatment efficacy.
• Existing validation methods may not fully capture the complexities of dose distribution within biological tissues.

Purpose of the Study:

• To develop and demonstrate a novel heterogeneous head phantom for experimental validation of BNCT dose predictions.
• To compare measured reaction rates within the phantom against TPS predictions and Monte Carlo simulations.
• To establish a reference standard for testing and verifying BNCT dosimetry calculations.

Main Methods:

• Construction of a cylindrical head phantom with distinct regions simulating skin, skull, brain, and a tumor using polymethyl methacrylate, calcium phosphate, air, and boric acid.
• In-phantom measurement of 197Au(n,γ)198Au reaction rates using gold activation wires at various depths and interfaces.
• Irradiation of the phantom at the Tsing Hua Open-pool Reactor BNCT facility.
• Comparison of experimental results with TPS predictions (voxel-based geometry from CT images) and Monte Carlo simulations (analytical geometry).

Main Results:

• The heterogeneous head phantom successfully simulated relevant anatomical structures and tissue compositions for BNCT dosimetry.
• Measured gold reaction rates provided direct experimental data on dose distribution within the phantom.
• Comparisons showed discrepancies between experimental data, TPS predictions, and Monte Carlo simulations, highlighting areas for TPS improvement.
• The experimental data served as a benchmark for evaluating the accuracy of different computational methods.

Conclusions:

• The developed head phantom is a valuable tool for experimentally validating BNCT treatment planning systems.
• The study provides critical data for refining computational models and improving the accuracy of BNCT dosimetry.
• This phantom and its associated data can serve as a reference for future BNCT research and quality assurance.