RBE of a Thermal Neutron Beam and the ¹⁰B(n, α)⁷Li Reaction on Cultured B-16 Melanoma Cells

Summary

The RBE of a thermal neutron beam and the ¹⁰B(n, α)⁷Li reaction were determined in cultured B-16 melanoma cells. The Kyoto University Research Reactor (KUR) was used as a thermal neutron source which had a very low contamination of gamma-rays and fast neutrons. The cells were irradiated with the beam in the presence or absence of ¹⁰B-boric acid. The absorbed dose from the neutron capture reaction to the cells was calculated by a method of Kitao (1975). Survival curves in both conditions had no shoulder and D₀ values were 0·506 or 0·604 Gy in the presence or absence of 5 µg ¹⁰B/ml-medium, respectively. The D₀ value of the ¹⁰B(n, α)⁷Li reaction was also estimated at 0·466 Gy, assuming each component of radiation was additive. The RBEs of the KUR thermal neutron beam and the ¹⁰B(n, α)⁷Li reaction relative to ⁶⁰Co gamma-rays were estimated as 4·62 and 6·01 at 0·1 surviving fraction, respectively.

Using these results, we calculated the absorbed dose from the ¹⁰B-compound and estimated the specific accumulation in the cultured cells of ¹⁰B-compounds which we have previously reported but not quantified (Nakanishi et al. 1980, Ichihashi et al. 1982).

• thermal neutrons
• RBE
• ¹⁰B-compounds
• ¹⁰B(n, α) ⁷Li reaction