Experimental dosimetry and beam evaluation in a phantom for near lithium threshold accelerator based BNCT

Current accelerator-based neutron source concepts for boron neutron capture therapy (BNCT) are centered on the lithium (p,n) reaction. The near lithium threshold source concept uses proton energies < or approx. 100 keV above the reaction threshold energy (1.88 MeV). For deeply seated brain tumors, epithermal (1 eV to 10 keV) neutrons are needed to penetrate the skull cap and subsequently thermalize at the tumor location. All BNCT neutron sources inherently have thermal, fast neutron and gamma-ray contamination. In order to quantify the thermal neutron component, a cylindrical acrylic head phantom has been constructed to simulate the patient's head and neck. BF3 proportional counters have been used to determine the thermal neutron flux (boron dose). The thermal neutron flux component has been compared with Monte Carlo N-Particle (MCNP) code calculations. Our results indicate a good comparison between the MCNP code calculations and the benchmark experiments performed. The results also indicate that the near threshold neutron concept is competitive with other BNCT neutron sources