Advances towards using finger/toenail dosimetry to triage a large population after potential exposure to ionizing radiation

Abstract

Rapid and accurate retrospective dosimetry is of critical importance and strategic value for the emergency medical response to a large-scale radiological/nuclear event. One technique that has the potential for rapid and accurate dosimetry measurements is electron paramagnetic resonance (EPR) spectroscopy of relatively stable radiation-induced signals (RIS) in fingernails and toenails. Two approaches are being developed for EPR nail dosimetry. In the approach using ex vivo measurements on nail clippings, accurate estimation of the dose-dependent amplitude of the RIS is complicated by the presence of mechanically-induced signals (MIS) that are generated during the nail clipping. Recent developments in ex vivo nail dosimetry, including a thorough characterization of the MIS and an appreciation of the role of hydration and the development of effective analytic techniques, have led to improvements in the accuracy and precision of this approach. An in vivo nail dosimetry approach is also very promising, as it eliminates the problems of MIS from the clipping and it has the potential to be an effective and efficient approach for field deployment. Two types of EPR resonators are being developed for in vivo measurements of fingernails and toenails.

Figure 1

MIS singlet, MIS broad component, and MIS doublet component spectra that are used in spectral decomposition.

Figure 2

Dose-response from Set A: 20 sets of 5 clipped fingernails irradiated at different dose levels. The RIS was estimated based on the correlation between the MIS singlet and the MIS broad component, shown in Figure 1. The signal intensities were normalized to sample mass. Error bars represent the standard error of the mean (SEM). SEP is the standard error of prediction.

Figure 3

Dose-response from Set B (10 sets), where the value of C from Set A (20 sets) was used to relate the MIS singlet and the MIS broad component. The signal intensities were normalized to sample mass. Error bars represent SEM.

Figure 4

Aperture geometry for the A) hole (left) and B) sub-wavelength surface coils (right).

Figure 5

Sample EPR spectrum taken using the aperture resonator, developed from a TE102 Bruker cavity with a hole diameter of 4.5 mm. The spectrum was acquired with a modulation amplitude of 5 G, a scan width of 150 G, a time constant of 16 ms, an incident RF power of 23.4 mW, and a total scan time of 90 s.

Figure 6

Design of surface resonator array showing coupling and mode suppression bridges.