Electron paramagnetic resonance retrospective dosimetry concepts for radiation accidents

Electron paramagnetic resonance (EPR) dosimetry is one of the most important tools for dose assessment after unexpected radiological accidents. Its use for triage after an incident in which a large number of people were exposed to potentially clinically significant levels of radiation has attracted attention. The EPR technique allows to determine the absorbed dose by measuring the signals arising from radicals formed under the influence of ionising radiation. These radicals interact with their environment, so the relationship between the intensity of the EPR signal and the radiation dose must be analysed for each material. The material could be the biological tissues of the victim: hair, nails, tooth enamel, and bones. The extensive use of tooth enamel for this technique has been published as an IAEA technical report. In our studies detailed here, we have performed experiments on the widely used X-band spectrometer (9.4 GHz), but examples of studies demonstrating the advantages of Q band (34 GHz) instruments and the suitability of L-band (1.1 GHz) for in-vivo dosimetry are also reported here. The results obtained using established protocols associated with different sample including nail and hair sample performed in our laboratory are given, the recommendations about protocols from sample collection to dose reporting are proposed, and finally the future of EPR dosimetry is discussed.