Elsevier

Radiation Measurements

Volume 42, Issues 6–7, July–August 2007, Pages 1085-1088
Radiation Measurements

Protocol for emergency EPR dosimetry in fingernails

https://doi.org/10.1016/j.radmeas.2007.05.024Get rights and content

Abstract

There is an increased need for after-the-fact dosimetry because of the high risk of radiation exposures due to terrorism or accidents. In case of such an event, a method is needed to make measurements of dose in a large number of individuals rapidly and with sufficient accuracy to facilitate effective medical triage. Dosimetry based on EPR measurements of fingernails potentially could be an effective tool for this purpose. This paper presents the first operational protocols for EPR fingernail dosimetry, including guidelines for collection and storage of samples, parameters for EPR measurements, and the method of dose assessment. In a blinded test of this protocol application was carried out on nails freshly sampled and irradiated to 4 and 20 Gy; this protocol gave dose estimates with an error of less than 30%.

Section snippets

Introduction and background

After-the-fact dosimetry in isolated teeth and biological dosimetry have been proven to be very useful methods for dose reconstruction and investigation of incidents in which there may be significant exposure to radiation (Clairand et al., 2006). However, for the fast triage of a large number of casualties that is needed immediately after an exposure event, most existing dosimetric techniques require a significant delay before final results are available, while the one existing method that can

Protocol for dosimetry

The protocol for fingernail dosimetry includes the following steps:

  • Sample collection and storage,

  • EPR measurements including sample preparation,

  • Dose assessment.

Three main spectral components can be identified in the EPR spectra of fingernails, i.e. a radiation induced signal (RIS), an intrinsic background signal (BKS), and a mechanically induced signal (MIS) (Symons et al., 1995). The structure of the RIS has not yet been fully elucidated, but there are some indications it has at least two

Sample collection and storage

Separate collection of nails (left/right, hand and foot) is highly desirable because this can give information on the dose distribution of the exposure. The samples should be as large as possible and obtained with the minimum possible number of cuts. There is no need for any special treatment of the sample. Because contact with water can have a significant effect on the RIS (Romanyukha et al., 2007), it is important to note at the time of sample collection any hand washing or excessive hand

Sample preparation

Samples should be obtained in a way to minimize the intensity of the MIS. Since its intensity directly depends on the amount of cut edges, samples should be as large as possible obtained with a minimum amount of cutting. Because the MIS decays much faster than the RIS, it is essential to record the time that the sample was obtained and, if feasible, it may be beneficial to wait to perform the EPR measurements for several hours after the samples are obtained. The decay rate of the MIS is

EPR measurements

As an example, the following parameters were used for spectra acquisition with a Bruker EMX spectrometer equipped with a high Q cavity: (incident microwave power 0.5 mW, modulation amplitude 0.2 mT, and time constant of 163.8 ms). The number of repeated acquisitions and the number of scans for each acquisition should be optimized according to the intensity of the measured signals, the number of samples, as well as a compromise between the accuracy of the measurements and the urgency to have the

Dose estimation

Under emergency conditions, an initial rapid estimate of dose in nails can be carried out using Eqs. (1) and (2) with average values of H, D, and BKS intensity determined from previous measurements of nails taken from the largest possible sample of donors. This preliminary rough dose estimate can be performed in less than 10 min, including the time of measurement. Variations in these average values due to age, ethnic origin, gender, dietary factors and season of the year have not been yet

Limits of applicability

One of the main limiting factors is the delay between the irradiation and the collection of the sample. In real conditions, this delay could range from 1–2 h to days. Because the increase of temperature or humidity accelerates the decay of the signal, it might be difficult to estimate accurately the fading correction factor because of difficulty in estimating these conditions before sample collection.

The ability to implement this technique in the field depends on developments which, while quite

Conclusion

Using our current knowledge of nail dosimetry, it was possible to write a protocol for collection, storage, and measurement by EPR of fingernails or toenails in emergency situations. Rapid estimation of dose in the range of a few Gy to several tens of Gy can be made quickly and for a large number of samples, with an estimated accuracy of 30% if samples are properly collected in a delay of a few hours after irradiation. If the exposure is asymmetric it can provide data on some critical aspects

Acknowledgement

This study was partially supported in part by NIH Grant U19 AI067733, and by a Department of Defence Grant, DA905-02-011 (DTRA).

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