Dependence of Radiation-induced Signals on Geometry of Tooth Enamel Using a 1.15 GHz Electron Paramagnetic Resonance Spectrometer: Improvement of Dosimetric Accuracy

Abstract

We aim to improve the accuracy of electron paramagnetic resonance (EPR)-based in vivo tooth dosimetry using the relationship between tooth geometry and radiation-induced signals (RIS). A homebuilt EPR spectrometer at L-band frequency of 1.15 GHz originally designed for non-invasive and in vivo measurements of intact teeth was used to measure the RIS of extracted human teeth. Twenty human central incisors were scanned by microCT and irradiated by 220 kVp x-rays. The RISs of the samples were measured by the EPR spectrometer as well as simulated by using the finite element analysis of the electromagnetic field. A linear relationship between simulated RISs and tooth geometric dimensions, such as enamel area, enamel volume, and labial enamel volume, was confirmed. The dose sensitivity was quantified as a slope of the calibration curve (i.e., RIS vs. dose) for each tooth sample. The linear regression of these dose sensitivities was established for each of three tooth geometric dimensions. Based on these findings, a method for the geometry correction was developed by use of expected dose sensitivity of a certain tooth for one of the tooth geometric dimensions. Using upper incisors, the mean absolute deviation (MAD) without correction was 1.48 Gy from an estimated dose of 10 Gy; however, the MAD corrected by enamel area, volume, and labial volume was reduced to 1.04 Gy, 0.77 Gy, and 0.83 Gy, respectively. In general, the method corrected by enamel volume showed the best accuracy in this study. This homebuilt EPR spectrometer for the purpose of non-invasive and in vivo tooth dosimetry was successfully tested for achieving measurements in situ. We demonstrated that the developed correction method could reduce dosimetric uncertainties resulting from the variations in tooth geometric dimensions.

Enhanced Dosimetric Accuracy Using Quality Factor Compensation Method for In Vivo Electron Paramagnetic Resonance Tooth Dosimetry

“…The filling factor of the resonator is determined by the relative location of the resonator and sample tooth as well as the size of the sample. The inevitable difference in the size of the teeth was probed to be moderated with the geometric correction using the tooth enamel area, or volume of the teeth (Park et al 2021). The power incident to the resonator is not changed during the measurements.…”

“…A 1.15 GHz continuous wave EPR spectrometer developed in previous studies was used for the EPR measurements (Park et al 2021; Choi et al 2022). The EPR dose-response data were collected from the teeth with and without the pseudo-in-vivo phantom.…”

Reflections on the future developments of research in retrospective physical dosimetry

“…The in vivo EPR response is sample dependent [56] and requires procedures for dose response calibration [57].…”

Enhancing Precision in L-band Electron Paramagnetic Resonance Tooth Dosimetry: Incorporating Digital Image Processing and Radiation Therapy Plans for Geometric Correction

“…Experiments were performed using an in-house-built continuous-wave in vivo EPR spectrometer described in detail elsewhere (Park et al 2021). The overall design of the EPR spectrometer used was based on that designed at Dartmouth College (Hirata and Luo 2001;Walczak et al 2005;Williams et al 2011Williams et al , 2014.…”