The Dose Spiking Technique for Measuring Low Doses in Deciduous Teeth Enamel Using EPR Spectroscopy for Retrospective and Accident Dosimetry

Abstract

Dose estimation by electron paramagnetic resonance (EPR) has been accomplished using the standard EPR dosimetry technique (ISO protocol 13304-1 for EPR retrospective dosimetry). However, different studies showed that these techniques have high measurement errors in measuring the low doses (10–100 mGy) in enamel. This work proposes a new method to make a dosimetric signal visible and measurable at low doses. The sample was purified using both chemical and mechanical processes. The pure sample mass and position and the EPR acquisition parameters were optimized to enhance the spectrometer's sensitivity for the quantitative low dose measurements. At the same time to reduce errors from the sample and spectrum anisotropy, the total doses (low plus spike) and the spike dose (4 Gy) were measured by rotating 0 to 360 degrees (i.e., 40 degrees at a time) relative to constant magnetic field direction using a goniometer. Subsequently, the spectra were averaged after their g-factor normalization. However, at low doses (<30 mGy), the radiation induced signal (RIS) was obscured by the background signal (BGS). So, the dose spiking technique was used as an alternative method. Ten low-dose deciduous molar tooth enamel (10–100 mGy) samples were spiked to the higher doses by delivering 4 Gy and measured using the X-band continuous wave (CW) EPR (Bruker EMXmicro) spectrometer. The total dose EPR signal was distinctly visible, and the peak-to-peak (P2P) amplitude height was measured. Then, the total dose was subtracted with the spike, often called a reference sample, to determine the initial low doses. The measurement errors using this method were lower than the previous methods. These results demonstrated that this method could be promising for solving low dose measurement problems in EPR dosimetry with deciduous and permanent tooth enamel.

A Perspective from Ontario Tech University Industrial Research Chairs on 20 Years of Capacity Building in Health Physics and Radiation Science

“…The equipment used is a Bruker EMXmicro X-Band EPR spectrometer. The technique has been used to measure physical doses near CANDU NPPs using tooth samples obtained from local dentists (Ghimire and Waller 2023a) and also yielded numerous approaches to improve sensitivity and decrease the lower limit of detection (Ghimire and Waller 2023b, c, d). Low dose non-human biota studies have been conducted on a variety of shelled aquatic species near and of interest to nuclear facilities in Canada (Gough et al 2022).…”