Protocol for emergency EPR dosimetry in fingernails
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.
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 , , 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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