Comparison of radiation effects of gadolinium and boron neutron capture reactions

Purpose: Cell survival assays were performed to evaluate the effects of rad iations released during neutron capture reactions by gadolinium-157, boron- 10 and by the combination of both. Materials and Methods: Single cell suspensions with or without Gd-157 and/o r B-10 were ex-posed to thermal neutrons produced by the Kyoto University r eactor, and standard cell survival curves were obtained. Results: Under the same molarity, cytocidal effects were 1.5 times greater for Gd-157 than for boron when compared at 10% survival levels. The presenc e of B-10 enhanced the radiation effect of Gd-157 neutron capture by 1.2-fo ld, suggesting that cells were not sufficiently irradiated as a result of n eutron fluency attenuation by the presence of excess neutron capture agents in the medium. Conclusions: When an equal number of atoms were present, Gd-157 was effecti ve as B-10 when exposed to an equal number of thermal neutrons. However, th ere was no benefit observed in the combination of Gd-157 and B-10 for neutr on capture therapy. Further studies are needed to determine optimal Gd-157 and B-10 concentrations as a function of tumor dimension.