An Attempt to Reduce the Background Free Radicals in Fingernails for Monitoring Accidental Hand Exposure of Medical Workers

Abstract

While it is recognized that some medical workers could receive significantly higher radiation doses to their hands than the routinely monitored personal doses, accurate retrospective dosimetry of their hand exposure is still challenging. To solve this issue, a combination of electron spin resonance (ESR) measurement and fingernails is worth to be investigated. However, the application of fingernail ESR dosimetry requires establishing an effective protocol to eliminate the background signal (BKG) which changes due to mechanical stress and other unclear factors, so that the radiation doses would be precisely evaluated from the radiation-induced signals (RIS) only. Thus, the authors investigated possible applications of antioxidants to remove or reduce the BKG in fingernails. In the present study, the effectiveness of chemical treatment using the dithiothreitol (DTT) reducing reagent was examined in irradiated and unirradiated fingernails. Chemically and non-chemically treated fingernails were subsequently exposed to 20 Gy of 137Cs γ-rays and the time changes of the BKG and RIS were confirmed in two different storage conditions: vacuum chamber and freezer. The results show that the non-chemically treated fingernails displayed significant intra-individual variations in the peak-to-peak intensities of both BKG and RIS. RIS from chemically and non-chemically treated samples showed correlations after freezer storage; signals were more stable than the samples stored in the vacuum chamber. Moreover, while the BKG of non-chemically treated samples demonstrated higher levels than those chemically treated, the intra-individual variations were further reduced by the DTT treatment. Our results imply that the use of an antioxidant for hand washing of medical workers prior to starting their work could be effective in reducing the pre-existing free radicals in their fingernails. This also suggests a practical application of hand exposure monitoring using fingernails as a part of radiological emergency preparedness in occupations where radiation or radionuclides are used. Research for finding safer and easier-to-handle antioxidants is to be focused on in future studies.

EPR Dosimetry in Human Fingernails: Investigation of the Origin of the Endogenous Signal and Implications for Estimating Dose from Nail Signals

“…The BKS was found to decrease by a factor of 3.2 but was not entirely removed. Similar results were seen by Gonzales et al (2020) in non-irradiated fingernails treated with 0.1 M DTT for 30 min [59]. These results suggest that those o-semiquinone radicals accessible to the reducing treatment were likely reduced to the diamagnetic dihydroquinone.…”

“…The radicals associated with the BKS and RIS 5 may not lend themselves to differences in distribution or localization of the two groups of radicals within the nail, although this remains to be investigated further. It has been suggested that BKS could be reduced through the use of an antioxidant during hand washing prior to starting work within an environment where exposure to radiation may occur as a part of radiological emergency preparedness in occupations such as first responders or medical workers [59]. However, this approach may not be amenable in situations where the radiation exposure has already occurred.…”

Applications of Medical Physics

“…Lastly, under the main topic of dosimetry, the Special Issue includes the study by Gonzales et al [20] which contribute to the development of a practical protocol for fingernail electron spin resonance (ESR) dosimetry useful for the routine monitoring of the extremity exposures of medical workers handling radiation sources. The authors investigate the effects of chemical treatment using dithiothreitol (DTT) on the changes of the ESR spectra in irradiated and unirradiated fingernails after a long storage time.…”

L-Band Electron Paramagnetic Resonance Tooth Dosimetry Applied to Affected Cattle Teeth in Fukushima

“…Most EPR measurements are performed in the X-band and some aim to detect signals in small amount of samples with the higher-frequency Q-band measurements [3]. Although EPR has a long history, its application to dosimetry is a novel application technique [4]. Attempts have also been made to measure the internal exposure of environmental organisms using radiation-induced signals in the sample [5].…”