Comparative study on the impact of storage conditions on ESR signals in fingernail dosimetry

Abstract

Human fingernails in combination with electron spin/paramagnetic resonance (ESR/EPR; hereafter “ESR”) spectroscopy have high potential as an individual dosimetry tool in radiological accidents. For the practical realization of this technique, it is necessary to reduce the uncertainty due to the instability of ESR signals affected by both individual and environmental factors. In the present study, we examined the effects of different storage conditions (in a laboratory room, refrigerator, freezer, and vacuum) and prior sample treatment on the intensity and stability of ESR signals from the fingernails of a child, which has not been investigated in previous studies, in comparison with those of an adult. Fingernail samples collected from a 10 y/o female child and a 37 y/o male adult were irradiated with 160 kV X-rays at 10 Gy, and the time changes of radiation-induced ESR signal (RIS) and background signal (BKG) under different conditions were measured for up to 30 days. As results, the ESR signal intensities (peak-to-peak amplitudes) of both child and adult fingernails were the most stable under freezing conditions, while the intensities of both RIS and BKG of fingernails were notably higher and more stable in the child samples than in the adult samples. In addition, the child samples showed a better response to the prior treatment using ethanol and water; BKG faded significantly after treatment despite the original higher background. Further investigations with more samples from donors of different ages are needed to clarify and reduce inter- and intra-individual variability in the dosimetric properties of human fingernails.