Exposure of fingernails and toenails to ionizing radiation creates radicals that are stable over a relatively long period (days to weeks) and characterized by an isotropic EPR signal at g = 2.003 (so-called radiation-induced signal, RIS). This signal in readily obtained fingernail parings has the potential to be used in screening a population for exposure to radiation and determining individual dose to guide medical treatment. However, the mechanical harvesting of fingernail parings also creates radicals, and their EPR signals (so-called mechanically-induced signals, MIS) overlap the g approximately 2.0 region, interfering with efforts to quantify the RIS and, therefore, the radiation dose. Careful analysis of the time evolution and power-dependence of the EPR spectra of freshly cut fingernail parings has now resolved the MIS into three major components, including one that is described for the first time. It dominates the MIS soon after cutting, but decays within the first hour and consists of a unique doublet that can be resolved from the RIS. The MIS obtained within the first few minutes after cutting is consistent among fingernail samples and provides an opportunity to achieve the two important dosimetry objectives. First, perturbation of the initial MIS by the presence of RIS in fingernails that have received a threshold dose of radiation leads to spectral signatures that can be used for rapid screening. Second, decomposition of the EPR spectra from irradiated fingernails into MIS and RIS components can be used to isolate and thus quantify the RIS for determining individual exposure dose.
"Based on extensive research investigating the sensitivity of the physical response of nails to ionizing radiation, using electron paramagnetic resonance (EPR) spectroscopy to measure dose in fingernails and toenails has been proposed as a physically-based biodosimetry method to use in initial triage. More specifically, allowing for proper collection and storage of samples, and accounting for water content, mechanical stress and signal fading, EPR-based dosimetry in nails could in the foreseeable future provide a reliable dose assessment for an individual with a detection limit of the order 1e2 Gy (Reyes et al., 2008; Wilcox et al., 2010; He et al., 2014). However, to correctly interpret the doses absorbed in nails and to measure the individual dose for purposes of treatment triage, it is also necessary to have prior knowledge of the ratio between the dose absorbed in fingernails and effective whole body or organ dose for a broad photon energy range and standard irradiation geometries. "
[Show abstract][Hide abstract] ABSTRACT: Absorbed doses to fingernails and organs were calculated for a set of homogenous external gamma-ray irradiation geometries in air. The doses were obtained by stochastic modeling of the ionizing particle transport (Monte Carlo method) for a mathematical human phantom with arms and hands placed loosely along the sides of the body. The resulting dose conversion factors for absorbed doses in fingernails can be used to assess the dose distribution and magnitude in practical dose reconstruction problems. For purposes of estimating dose in a large population exposed to radiation in order to triage people for treatment of acute radiation syndrome, the calculated data for a range of energies having a width of from 0.05 to 3.5 MeV were used to convert absorbed doses in fingernails to corresponding doses in organs and the whole body as well as the effective dose. Doses were assessed based on assumed rates of radioactive fallout at different time periods following a nuclear explosion.
"We showed the limitations of EPR on hair as a method for an accident dosimetry, but we provided more systematic information on radiation-induced radicals in hair than has previously been available. A protocol for hair sample can also be written including the sample collection, storage conditions and EPR measurements in emergency situations as an accident dosimetry as done for fingernail samples (Trompier et al., 2007; Wilcox et al., 2010; Alexander et al., 2007). To prepare a biological dosimetry protocol, a number of studies need to be performed on the same kind of samples; thus the generalized findings could be obtained for each individual. "
[Show abstract][Hide abstract] ABSTRACT: The potential use of human hair samples as biologic dosimeter was investigated by electron spin
resonance (ESR) spectroscopy. The hair samples were obtained from female volunteers and classified
according to the color, age and whether they are natural or dyed. Natural black, brown, red, blonde and
dyed black hair samples were irradiated at low doses (5–50 Gy) and high doses (75–750 Gy) by gamma
source giving the dose rate of 0.25 Gy/s in The Sarayköy Establishment of Turkish Atomic Energy
Authority. While the peak heights and g-values (2.0021–2.0023) determined from recorded spectra of
hair were color dependent, the peak-to-peak line widths were varied according to natural or dyed hair
(ΔHpp: 0.522–0.744 mT). In all samples, the linear dose–response curves at low doses saturated after
300 Gy. In black hair samples taken from different individuals, differences in the structure of the
spectrum and signal intensities were not observed. The EPR signal intensities of samples stored at room
temperature for 22 days fell to their half-values in 44 h in black hair, 41 h in blonde and brown hairs,
35 h in dyed black hair and in 17 h in red hair. The activation energies of samples annealed at high
temperatures for different periods of time were correlated well with those obtained in the literature. In
conclusion, hair samples can be used as a biological dosimeter considering the limitations showed in
"In vitro measurements of fingernail clippings in the X-band (Trompier et al. 2007, 2009; Romanyukha et al. 2007, 2010; Reyes et al. 2008, 2009, 2012; Black and Swarts 2010; Wilcox et al. 2010); In vitro measurements of fingernail clippings in the Q-band (Romanyukha et al. 2011; Trompier et al. 2014a); In vivo measurements of fingernails in the X-band (He et al. 2011). "
[Show abstract][Hide abstract] ABSTRACT: In this paper, we report results of radiation dose measurements in fingernails of a worker who sustained a radiation injury to his right thumb while using 130 kVp X-ray for nondestructive testing. Clinically estimated absorbed dose was about 20-25 Gy. Electron paramagnetic resonance (EPR) dose assessment was independently carried out by two laboratories, the Naval Dosimetry Center (NDC) and French Institut de Radioprotection et de Sûreté Nucléaire (IRSN). The laboratories used different equipments and protocols to estimate doses in the same fingernail samples. NDC used an X-band transportable EPR spectrometer, e-scan produced by Bruker BioSpin, and a universal dose calibration curve. In contrast, IRSN used a more sensitive Q-band stationary spectrometer (EMXplus) with a new approach for the dose assessment (dose saturation method), derived by additional dose irradiation to known doses. The protocol used by NDC is significantly faster than that used by IRSN, nondestructive, and could be done in field conditions, but it is probably less accurate and requires more sample for the measurements. The IRSN protocol, on the other hand, potentially is more accurate and requires very small amount of sample but requires more time and labor. In both EPR laboratories, the intense radiation-induced signal was measured in the accidentally irradiated fingernails and the resulting dose assessments were different. The dose on the fingernails from the right thumb was estimated as 14 ± 3 Gy at NDC and as 19 ± 6 Gy at IRSN. Both EPR dose assessments are given in terms of tissue kerma. This paper discusses the experience gained by using EPR for dose assessment in fingernails with a stationary spectrometer versus a portable one, the reasons for the observed discrepancies in dose, and potential advantages and disadvantages of each approach for EPR measurements in fingernails.
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