EPR-dosimetry with tooth enamel for low doses.

Results are presented for electron paramagnetic resonance (EPR) dosimetry with tooth enamel that focus on the dose region below 100 mGy. Three uncontaminated molars were gamma-irradiated in steps of 10–100 mGy and then in larger steps to 400 mGy. The spectra were evaluated using a deconvolution method including a simulated powder spectrum for extracting the dose related EPR signal of tooth enamel. The dose related signal intensity and the variability between samples were evaluated to investigate the feasibility to reconstruct irradiation doses below 100 mGy. Averaged signal amplitudes as well as the signal amplitudes for single sample were analysed. The performance parameters, critical dose and limit of detection, were calculated and compared with the averaged signal amplitudes of sets of five samples of a pool of mixed tooth samples originating from the same source but irradiated from 100 to 1500 mGy. The values of performance parameters were found to depend on the number and type of samples included in assessment. The evaluated critical dose varied between 131 and 50 mGy for measurements of single sample, and 73 and 33 mGy for average amplitudes of three and five samples, respectively. For exposures below 100 mGy the dose related EPR-signal amplitude was found to correlate with the applied dose only for one of three samples for which the evaluated critical dose was 50 mGy