Radiation Chemical Yield of Hydroxyl Radicals for Accelerator-based Boron Neutron Capture Therapy: Dose Assessment of B-10(n,alpha)Li-7 Reaction Using Coumarin-3-Carboxilic Solution

摘要

Evaluation of the characteristics of accelerator-based thermal neutron fields is recognized as an important issue when discussing the effectiveness of boron neutron capture therapy (BNCT). In this study, we propose that the radiation chemical yield (G value) of hydroxyl radicals (G(OH)center dot) can be considered a universal parameter for the description of the accelerator-based thermal neutron field. The G(OH)center dot of the B-10(n,alpha)Li-7 reaction was quantitatively evaluated using an aqueous coumarin-3-carboxylic acid (3CCA) solution, and was discriminated from that of contaminations (i.e., gamma rays and fast neutrons). The G(OH)center dot of the B-10(n,alpha)Li-7 reaction was 0.107 +/- 0.004 OH center dot/100 eV, which is almost equivalent to that exposed to alpha particles with an energy of 6.0 MeV. Since the G(OH)center dot of gamma rays from a Co-60 source is 2.03 +/- 0.05 OH center dot/100 eV, this lower value suggests that indirect action by the B-10(n,alpha)Li-7 reaction is not dominant in BNCT. However, our results indicate that one can assess the Co-60 equivalent dose of the B-10(n,alpha)Li-7 reaction in water from the G(OH)center dot derived using aqueous 3CCA solution in the accelerator-based thermal neutron field. (C) 2019 by Radiation Research Society