Quantification of low dose signal in EPR tooth dosimetry--a novel approach.

For radiation exposures below 100 mGy, the dosimetric signal in tooth enamel is too small to be measured by using the traditional dose reconstruction procedure. This is because low amplitude zero-added-dose signal can not be identified in an EPR spectrometer. A technique is presented wherein, zero-added-dose signal. when amplified by a proper known dose, can be measured in the EPR spectrometer. Mathematically, the accidental dose x is modified by a known amount of exposure, y (large enough so that the signal is now visible), and total exposure becomes x' = x + y, which is the modified-zero-added dose. The exposure x' is then quantified using the conventional backward extrapolation method and the accidental dose can be measured. In a laboratory controlled experiment, the feasibility of dose reconstruction in the 100 mGy range has been demonstrated. This may enable measurements of dose even due to suspected low exposure in tooth enamel.