State of the art in nail dosimetry: free radicals identification and reaction mechanisms

Abstract

Until very recently, analysis of bone biopsies by means of the method of electron paramagnetic resonance (EPR) collected after surgery or amputation has been considered as the sole reliable method for radiation dose assessment in hands and feet. EPR measurements in finger- and toenail have been considered for accident dosimetry for a long time. Human nails are very attractive biophysical materials because they are easy to collect and pertinent to whole body irradiation. Information on the existence of a radiation-induced signal in human nails has been reported almost 25 years ago. However, no practical application of EPR dosimetry on nails is known to date because, from an EPR perspective, nails represent a very complex material. In addition to the radiation-induced signal (RIS), parasitic and intense signals are induced by the mechanical stress caused when collecting nail samples (mechanically induced signals—MIS). Moreover, it has been demonstrated that the RIS stability is strongly influenced not only by temperature but also by humidity. Most studies of human nails were carried out using conventional X-band microwave band (9 GHz). Higher frequency Q-band (37 GHz) provides higher spectral resolution which allows obtaining more detailed information on the nature of different radicals in human nails. Here, we present for the first time a complete description of the different EPR signals identified in nails including parasitic, intrinsic and RIS. EPR in both X- and Q-bands was used. Four different MIS signals and five different signals specific to irradiation with ionizing radiation have been identified. The most important outcome of this work is the identification of a stable RIS component. In contrast with other identified (unstable) RIS components, this component is thermally and time stable and not affected by the physical contact of fingernails with water. A detailed description of this signal is provided here. The discovery of stable radiation-induced radical(s) associated with the RIS component mentioned opens a way for broad application of EPR dosimetry in human nails. Consequently, several recent dosimetry assessments of real accident cases have been performed based on the described measurements and analyses of this component.

Comparison of Continuous Wave and Rapid Scan X-band Electron Paramagnetic Resonance of Irradiated Clipped Fingernails

“…The EPR spectrum in fingernails has a very complex structure. According to reference (10) , it consists of several radiation-induced spectral components, along with several of non-radiation origin. These signals have very similar paramagnetic parameters and are difficult to distinguish when the EPR signal is measured at X-band.…”

“…There is renewed interest in quantitation of these electron paramagnetic resonance (EPR) signals because of their potential utility for measuring radiation dose, especially for medical triage in situations where there is a need to determine whether large numbers of people were exposed to medically significant doses of radiation (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13) . Fingernail dosimetry has been applied to three cases of accidental radiation exposure (14) .…”

“…The state of the art was reviewed recently (10,15) . In addition, there are recent studies that seek to determine the optimum EPR frequency (e.g.…”

Dielectric-Backed Aperture Resonators for X-Bandin vivoEPR Nail Dosimetry

“…Three experimental models are used to evaluate the performance of the fabricated resonators. The first is to create an in vitro fingernail model made of films with singlet EPR signals backed by a tissue equivalent polyacrylamide gel block (PAA) (26) (27) and corrected for the background signal. The signal intensity is largely driven by the RIS2 intensity in 137-Cs gamma-irradiated nail samples used to test the in vivo nail resonators and calibrate the RIS dose equivalency of the Kapton film signal intensities.…”

EPRBioDose 2013: EPR applications and biological dosimetry

“…Nails are less radiation sensitive than teeth, but nevertheless have some potential for use in dosimetry. The state of the art in nail dosimetry was presented by Trompier et al (2014). Alternatively to the tissues of the human body, materials present in ubiquitous personal items and their dosimetric properties are currently being widely investigated.…”