-The effect of the crushing and additive dose procedures used in EPR dosimeuy of enamel was studied on the signals with g-factors of 2.0045 and gl = 2.0018, g, = 1.9975. Eight~tions,~g~g fi size from <75 micrometers to 2 mm, were prepared from one tooth. Two cases wem investigated: crushing of a non-irradiated sample and of a sample previously irradiated (6 Gy tinm Wo gamma ray source). In the non-imadiated study, the intensity of the native signal at 2.0045 inaeased by circa 1.75 times as the grain size &cmased from maximum to minimum. A small decrease in radiation sensitivity (< 8%) was also observed with decreasing grain size. In the irradiated samples, crushing resulted in slight variations of reconstructed doses from expecmd values, but the worst possible case (grain sizes c 75 pm) showed that additional errors were less than 10%.The radiation sensitivity of enamel measumd immediately atter exposure is underestimated. It increases by about 15% in the fmt month. Based on the decomposition of the observed specq a new interpretation of transient signals is proposed which explains the above phenomena. Recommendations about how to use this interpretation in retrospective EPR dosimetry are given.
Accurate assessments of doses received by individuals exposed to radiation from nuclear accidents and incidents such as those at Hiroshima and Nagasaki, the Nevada test site, Cheliabinsk and Mayak are required for epidemiological studies seeking to establish relationships between radiation dose and health effects. One method of retrospective dosimetry which allows for measurement of cumulative gamma ray doses received by exposed individuals is electron paramagnetic resonance spectroscopy (EPR) of tooth enamel. Tooth enamel stores and retains, indefinitely, information on absorbed radiation dose. And teeth are available in every population as a result of dental extraction for medical reasons including periodontal disease and impacted wisdom teeth. In the case of children, deciduous teeth, which are shed between the ages of 7 and 13, can be a very important dosimetric source if documented collection is implemented shortly following an accident. Current status EPR of tooth enamel is a relatively new technique for retrospective dosimetry but in the past two years increasing effort has been put into its development and evaluation. Efforts have centered on determining the accuracy which may be achieved with current measurement techniques as well as the minimum doses presently detectable. One study conducted through the joint European Union (EU)/Former Soviet Union (FSU) project, ECP-10, involved the blind measurement of doses delivered to enamel grains by a Cs-137 laboratory source. The intercomparison involved eight laboratories from the EU and FSU and one from the United States. Grains from 40 teeth were combined to form a homogenous sample. Five dose levels ranging from 0-1 Gy were applied prior to distribution of the grains to the participants. Each
-The f~st two signals correspond to the components of the radiation induced signal third signal corresponds to the native signal reported in dosimetry and datingThe remaining two signals were found to be stable and sensitive to both gamma and sunlight exposure. Their sensitivity response to light and radiation was considerably different which gives rise to the possibility that the g = 2.0052 and g = 2.0083 signals might be used as indicators of the dose resulting from light exposure.
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