T₂ Measurements in Tooth Enamel Using Electron spin Resonance (ESR)

This study examines radiation-induced paramagnetic defects in the enamel layer of the human tooth using advanced pulse ESR methods, with the ultimate goal of applying these methods in retrospective biodosimetry to conduct large-scale triage after major radiological events. ^1,2

ESR is a well-known method which can be used to detect and measure radiation-induced defects—radicals—in the enamel layer of the teeth. The concentration of these defects in teeth is known to be linearly correlated with the dose in the applicable range.³ Despite its great potential, and its proven results when applied to extracted teeth, ESR is still struggling to provide accurate in-vivo readings.⁴

In this work, we use advanced pulse ESR techniques in order to measure the relaxation time, T₂, related to spin-spin interaction. This parameter was measured as a function of radiation dose to characterize the relation between the dose and T₂. Our hypothesis is that this type of ESR data can be correlated well with the concentration of defects, and thus enable the development of new markers for in-vivo estimation of dose amount without the need for quantitative measurements of both the ESR signal and enamel volume. In our initial experiments we worked with teeth irradiated with relatively high doses of 10-100Gy that were used to develop the approach, which will be subsequently applied to measure relaxation times for samples with lower doses. Our measurements show relaxation times in the range of hundreds of nanosec up to one microsec.

Reference

1 S. W. S. McKeever and S. Sholom, Radiat. Meas., 2016, 92, 8–18.

2 A. B. Flood,et al., Radiat. Prot. Dosimetry, 2016, 1–9.

3 P. Fattibene and F. Callens, Appl. Radiat. Isot., 2010, 68, 2033–2116.

4 H. Woflson, R. Ahmad, Y. Twig, B. Williams and A. Blank, Health Phys., 2015, 108, 326–335.