Electron paramagnetic resonance radiation dosimetry
Congress title :International Congress of Radiation Research
Congress location :San Francisco
Congress date :08/07/2007
Over the past decade, the threat of malevolent uses of radioactive materials has grown and some of the scenarios could lead to the exposure to ionizing radiation of a larger number of people than in classical situation encountered for past radiation accidents. In this case, dose estimations should be carried out in individuals rapidly and with sufficient accuracy to enable effective medical triage. In addition of existing triage methods (haematology, clinical and biological dosimetry), there are recent developments in emerging biodosimetric technologies for acute external exposure, such as Electron Paramagnetic Resonance spectrometry (EPR), that can enhance triage and dose assessment strategies. The use of EPR for dosimetry is based on the capability of the technique specifically and sensitively to measure unpaired electron species and the fact that ionizing radiation creates such species in exact proportion to dose. While the lifetimes of these species are very short in aqueous systems (nanoseconds life times), the radiation-induced signals can be extremely stable in non-aqueous media, including teeth and bone, and also sugars, fingernails, and hair for example.
EPR measurements of tooth enamel or bone biopsies, although currently used in classical radiation accident situation, are obviously out of scope for medical triage, because an invasive sampling is needed. In order to overcome this difficulty there are two approaches using EPR that seems to be suitable for emergency purposes: in vivo measurements of teeth and ex vivo measurements of fingernail or toenail clippings, which are non-invasive or minimally invasive.
This presentation will give an overview of the last developments in EPR methodology as triage tools. Even if a large and intensive work remains to perform to fully establish this method, recent developments are promising. Thus, it could be, in addition of established methods, a tool of choice in the medical management of victims of a large-scale radiation accident. This technique of retrospective dosimetry could at the end allow fast dose estimation without any delay. The dose sensitivity, according to the most recent works, should be sufficient for most of the scenarios of accidents.