Stability of X-band EPR signals from fingernails under vacuum storage

Training of clinical triage of acute radiation casualties: a performance comparison ofon-siteversusonlinetraining due to the covid-19 pandemic

A collection of powerful diagnostic tools have been developed under the umbrellas of NATO for ionising radiation dose assessment (BAT, WinFRAT) and estimate of acute health effects in humans (WinFRAT, H-Module). We assembled a database of 191 ARS cases using the medical treatment protocols for radiation accident victims (n= 167) and the system for evaluation and archiving of radiation accidents based on case histories (n= 24) for training purposes of medical personnel. From 2016 to 2019, we trained 39 participants comprising MSc level radiobiology students in an on-site teaching class. Enforced by the covid-19 pandemic in 2020 for the first time, an online teaching of nine MSc radiobiology students replaced the on-site teaching. We found that: (a) limitations of correct diagnostic decision-making based on clinical signs and symptoms were experienced unrelated to the teaching format. (b) A significant performance decrease concerning online (first number in parenthesis) versus on-site teaching (reference and second number in parenthesis) was seen regarding the estimate time (31 vs 61 cases per hour, two-fold decrease,p= 0.005). Also, the accurate assessment of response categories (89.9% vs 96.9%,p= 0.001), ARS (92.4% vs 96.7%,p= 0.002) and hospitalisation (93.5% vs 97.0%,p= 0.002) decreased by around 3%-7%. The performances of the online attendees were mainly distributed within the lower quartile performance of on-site participants and the 25%-75% interquartile range increased 3-7-fold. (c) Comparison of dose estimates performed by training participants with hematologic acute radiation syndrome (HARS) severity mirrored the known limitations of dose alone as a surrogate parameter for HARS severity at doses less than 1.5 Gy, but demonstrated correct determination of HARS 2-4 and support for clinical decision making at dose estimates >1.5 Gy, regardless of teaching format. (d) Overall, one-third of the online participants showed substantial misapprehension and insecurities of elementary course content that did not occur after the on-site teaching.

Electron spin resonance signal of human nails: increase after irradiation

We report the phenomenon whereby the electron spin resonance signal of human nails intensify after irradiation. Forty nail samples from three donors were divided into three groups (X-ray irradiated, γ-ray irradiated, and control). The extent of signal intensified after irradiation was proportional to the given dose under 11% humidity at 20 °C. This result seemed to contradict previous studies, reporting signal fading. Based on literature and our experimental results, we constructed a model taking both the decay and increase into consideration. Our investigation revealed that rapid deterioration in the signal intensity obscured the increase at humidity levels exceeding 40%.

The design of X-band EPR cavity with narrow detection aperture for in vivo fingernail dosimetry after accidental exposure to ionizing radiation

For the purpose of assessing the radiation dose of the victims involved in the nuclear emergency or radiation accident, a new type of X-band EPR resonant cavity for in vivo fingernail EPR dosimetry was designed and a homemade EPR spectrometer for in vivo fingernail detection was constructed. The microwave resonant mode of the cavity was rectangular TE101, and there was a narrow aperture for fingernail detection opened on the cavity’s wall at the position of high detection sensitivity. The DPPH dot sample and the fingernail samples were measured based on the in vivo fingernail EPR spectrometer. The measurements of the DPPH dot sample verified the preliminary functional applicable of the EPR spectrometer and illustrated the microwave power and modulation response features. The fingernails after irradiation by gamma-ray were measured and the radiation-induced signal was acquired. The results indicated that the cavity and the in vivo EPR dosimeter instrument was able to detect the radiation-induced signal in irradiated fingernail, and preliminarily verified the basic function of the instrument and its potential for emergency dose estimate after a radiation accident.

AN ADVANCE IN EPR DOSIMETRY WITH NAILS

Olive oil is proposed as a medium for storage of nails in the time between nail harvesting and electron paramagnetic resonance (EPR) measurements to minimise the decay of the radiation-induced EPR signals (RIS). The behaviours of three main EPR signals, namely, RIS, mechanically induced and the background signals (MIS and BG, respectively), were studied for storage in olive oil. The properties of the MIS and BG signals were very similar to those previously observed for the storage in a vacuum. The RIS singlet slightly increased during the first day of storage and then remained practically unchanged at least for 6 days. Dose recovery test revealed that doses at the level 2 Gy may be reconstructed with an accuracy of about ±20%.

The effect of sunlight and UV lamps on EPR signal in nails

The effects of illumination of nail clippings by direct sunlight, UV lamps and fluorescent bulbs on native and radiation-induced electron paramagnetic resonance (EPR) signals in nails are presented. It is shown that a few minutes of exposure of the nail clippings to light including a UV component (sunlight and UV lamps) generates a strong EPR signal similar to the other EPR signals observable in nails: native background (BKG), mechanically induced (MIS) or radiation-induced (RIS). This effect was observed in clippings exposed and unexposed to ionizing radiation prior to the light illuminations. An exposure of the clippings to fluorescent light without a UV component generated, within the examined range of the light fluences (up to 240 kJ/m²), an EPR signal with considerably lower yield than UV light. The light-induced signal (LIS) decayed after 10 min of water treatment of the samples. In contrast, it was still observable 3 months after illumination in samples stored in air at room temperature, and 3 weeks in frozen samples, respectively. It is concluded that the LIS can considerably affect assessment of the dosimetric RIS components in irradiated nails, and of the background signals in unirradiated nails, thus contributing to errors in EPR dosimetry in nails.

Developments in Biodosimetry Methods for Triage With a Focus on X-band Electron Paramagnetic Resonance In Vivo Fingernail Dosimetry

Instrumentation and application methodologies for rapidly and accurately estimating individual ionizing radiation dose are needed for on-site triage in a radiological/nuclear event. One such methodology is an in vivo X-band, electron paramagnetic resonance, physically based dosimetry method to directly measure the radiation-induced signal in fingernails. The primary components under development are key instrument features, such as resonators with unique geometries that allow for large sampling volumes but limit radiation-induced signal measurements to the nail plate, and methodological approaches for addressing interfering signals in the nail and for calibrating dose from radiation-induced signal measurements. One resonator development highlighted here is a surface resonator array designed to reduce signal detection losses due to the soft tissues underlying the nail plate. Several surface resonator array geometries, along with ergonomic features to stabilize fingernail placement, have been tested in tissue-equivalent nail models and in vivo nail measurements of healthy volunteers using simulated radiation-induced signals in their fingernails. These studies demonstrated radiation-induced signal detection sensitivities and quantitation limits approaching the clinically relevant range of ≤ 10 Gy. Studies of the capabilities of the current instrument suggest that a reduction in the variability in radiation-induced signal measurements can be obtained with refinements to the surface resonator array and ergonomic features of the human interface to the instrument. Additional studies are required before the quantitative limits of the assay can be determined for triage decisions in a field application of dosimetry. These include expanded in vivo nail studies and associated ex vivo nail studies to provide informed approaches to accommodate for a potential interfering native signal in the nails when calculating the radiation-induced signal from the nail plate spectral measurements and to provide a method for calibrating dose estimates from the radiation-induced signal measurements based on quantifying experiments in patients undergoing total-body irradiation or total-skin electron therapy.