Özet:

For many years, the number of ESR studies on nails have increased as a mean of rapid and accurate biodosimetry. The most important outcome of these studies is the identification of a stable radiation-induced signal (RIS5) component in nails by the French Radioprotection and Nuclear Safety Institute (IRSN). The other protocol was proposed by Sholom and McKeever funding from Dartmouth ESR center, with American National Institute of Health (NIH) funding. In this study, the results of three approaches on nail dosimetry were presented: two were based on the described protocols of IRSN and Dartmouth and the other used the classical added dose method. Nail samples were collected from a donor irradiated with 137Cs gamma rays (0.5 kGy/h). EPR measurements were carried out using a Bruker e-scan X-band EPR spectrometer. Samples irradiated up to doses of 25, 30, 85 and 168 Gy were used to construct the added dose-response curves in steps of 5 and 10 Gy. The reported intensities of RIS5 and center field signal (near g=2.004) were derived from peak-to-peak distance of the EPR signal (Figures 1 and 4). To test last protocol published in 2016, nail samples were irradiated by Co-60 gamma rays at 2 and 5 Gy as accident doses. The ESR signal intensities were recorded to use in formula given in proposed protocol.In the first protocol, differences between dose saturation points of exposed and unexposed samples which determine the accident doses were found as 15 Gy for the first group and 10 Gy for the second group (Figures 2 and 3). On the other hand, in the second protocol, the EPR signal intensity increased with increasing added doses. The experimentally measured EPR signal intensity values (y) fitted well by polynomial function and the extrapolated doses were calculated to be 13.89 and 22.19 Gy for 10 and 15 Gy accident doses, repectively (Figures 5 and 6). Lastly, according to Dartmouth center protocol, the mean accident doses were calculated as 2.18 and 4.5 Gy for 2 and 5 Gy accident doses, respectively. IRSN protocol using the RIS5 component and Dartmouth protocol were found to be successful methods for the evaluation of dose to fingernails exposed high-doses. However, classical approach using center field EPR signal given extrapolated doses in error of 38.9 and 47.9 percent was found to be unsuccessful. Further studies should be planned to test the IRSN and Dartmouth approaches for lower accident doses on more samples from different individuals.

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