Radiation Dose Measurement by ESR of Teeth

  • Summary


Bones and teeth consist of microcrystalline hydroxyapatite Ca10(PO4)6(OH)2, and organic protein,collagen.   The enamel covering the surface of teeth consists mainly of hydroxyapatite and is very resistant to metabolic change, therefore can be used as a very sensitive dosimeter in measuring radiation exposure.
In general, the radiation dose is obtained using the signal intensity of the CO2- radical generated by irradiation of the carbonate ion CO32-, which is contained in the enamel as an impurity. It is claimed that measurement as low as 30 mGy is possible (1).
However, for doses less than 5 Gy, as the signal of organic radicals (g=2.0046) is superimposed on the signal of the CO2- radical, this contribution must be subtracted (2) (3). If a sample is heated, the ESR signal of the organic radical which is generated by the decomposition of collagen protein increases (4). The reason why only enamel is generally used as the sample for the ESR method is because the g-value of the organic radical is almost the same as that of the CO2- radical. Therefore, when the evaluation of low dose samples is calculated, it is necessary to separate spectra and subtract the signal of the organic radical, otherwise it could lead to an overestimate. Also, it is necessary to check if there is a contribution to radiation exposure by dental x-rays. There are many studies on the ESR Dose Measurement Using Enamel of Teeth at several institutes (5),(6),(7). Please refer to “Application Note ER-080001” on how to calculate the exposed dose.

Fig.1. Change of Tooth’ ESR Signal by Microwave Power
(Using 60Co radiation source of JAERI Takasaki Laboratory, and irradiate g rays for about 2.5kGy)
Sample courtesy of Dr. Shitaoka of Nara University of Education


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