Characteristics of BDE dependent on 10B concentration for accelerator-based BNCT using near-threshold 7Li(p,n)7Be direct neutrons

The characteristics boron-dose enhancer (BDE) was evaluated as to the dependence on the 10B concentration for BNCT using near-threshold 7Li(p,n)7Be direct neutrons. The treatable protocol depth (TPD) was utilized as an evaluation index. MCNP-4B calculations were performed for near-threshold 7Li(p,n)7Be at a proton energy of 1.900 MeV and for a polyethylene BDE. Consequently, the TPD was increased by increasing T/N ratio, i.e., the ratio of the 10B concentration in the tumor (10BTumor) to that in the normal tissue (10BNormal), and by increasing 10BTumor and 10BNormal for constant T/N ratio. It has been found that the BDE becomes unnecessary from the viewpoint of increasing the TPD, when 10BTumor is over a certain level.