Discrimination of hydroxyl radical yields due to thermal neutrons, fast neutrons, and gamma rays in accelerator-based neutron fields

We proposed a depth-intensity curve discrimination (DCD) method for assessing absorbed dose contributions of hydroxyl radicals (HO·) due to thermal neutrons, fast neutrons, and gamma rays in accelerator-based mixed radiation fields, that are relevant to boron neutron capture therapy (BNCT). The HO· yields of thermal neutrons, fast neutrons, and gamma-rays measured by coumarin-3-carboxylic acid solutions were discriminately evaluated using depth-intensity curves of their radiations and maximum likelihood-expectation maximization algorithm. The discrimination accuracies of the three types of radiation were 2.8%, 4.2%, and 1.0%, respectively. We demonstrated that the DCD method is appropriate to determine absorbed dose contributions of HO· in complex accelerator-based neutron fields for BNCT.