Effect of mechanically induced background signal on EPR dosimetry of tooth enamel

Abstract

The effect of the mechanically induced background ESR signal whose Lande factor is g = 2.0038, width = 0.791 mT, on absorbed dose estimation using the additive method was studied. The intensity and width of this signal increases with decreasing grain size. It was found to be thermally stable and sensitive to 90Sr radiation. The latter phenomenon should lead to its increasing contribution to the radiation-induced hydroxyapatite signal at g ⊥ = 2.0018 at irradiation with higher doses. However, it was found that the interference between mechanically induced and the hydroxyapatite signals may be interpreted as either ‘negative’ for larger grain size or ‘positive’ for finer grain size. This feature in turn leads to under and overestimation of the hydroxyapatite signal, respectively, and is apparently caused by the inverse relationship between the signal width and grain size. Enamel samples were irradiated with 44, 88, 220, 440, 660 and 880 mGy from a 137Cs gamma ray source. It was determined that 220 mGy was the lowest absorbed dose that could be reliably detected, while doses as low as 44 mGy could tentatively be identified.