Achievable precision and accuracy in EPR dosimetry of tooth enamel

The utility of combining various methodologies is examined to remove systematically or correct for the major instrumental effects which introduce uncertainties in EPR dosimetry of tooth enamel. The result is a relatively high precision method that can be successfully transferred between laboratories. Only an ideal case was considered in this study whereby the actual native signal prior to irradiation was used as the empirical zero in each individual dose response. To prove its general value, the overall methodology was applied to seven teeth of differing quality, prepared using different methodologies, and measured in three laboratories using different EPR spectrometers. Using this approach to characterise the utility of both the methodology and instrumentation resulted in 5 +/- 5 mGy (1 sigma) spectral intensity reproducibility at the 100 mGy dose level for the seven samples analysed. Similarly, at the 1100 mGy level, spectral intensity reproducibility was found to be equivalent to 13 +/- 5 mGy (1 sigma) for the same seven samples. Assuming linearity of dose response in the 0-1100 mGy dose range and using dose responses at 100 mGy and 1100 mGy levels, gave an overall extrapolated x intercept (dose estimate) offset of -13 +/- 19 mGy (1 sigma).