Commissioning a compact, tabletop EPR spectrometer for alanine dosimetry

Abstract

Purpose:The large footprint and cost of the spectrometry equipment are often prohibitive for many institutions to start an alanine dosimetry program. However, compact spectrometers are gaining popularity as an alternative tool for quantitative chemical analysis and may be an attractive option for alanine dosimetry. Therefore, it was the goal of this work to characterize a novel compact EPR spectrometer and explore several spectral analysis methods that can be used for alanine dosimetry. Methods:The system stability, measurement variability, and dose response linearity was quantified for a MagnettechTM MiniScope MS 5000X tabletop spectrometer. In addition to conventional spectral analysis techniques, a novel post-processing algorithm was also developed to characterize the background spectrum signature and fit a quantum mechanical model to an alanine EPR spectrum to improve measurement repeatability. Following the system’s characterization, an uncertainty budget was developed to reflect the calibration accuracy and measurement precision. Results:A microwave power of 6.2mW was found to provide the highest spectrum sensitivity while avoiding the saturation of the alanine response, and a modulation width of 0.65mT provided the best noise minimization across the alanine signal while minimizing the degradation in the ruby’s EPR spectrum amplitude. The repeatability of the alanine dosimeters irradiated between 1Gy and 10Gy was improved using spectral fitting techniques. Conclusions:A novel tabletop EPR system was commissioned for alanine dosimetry. Following careful dosimetry protocols and analysis procedures, this work suggests that a k=1 combined uncertainty of 2.1% is obtainable for doses on the order of 10Gy. However, this uncertainty reflects the use of the dosimeter within a dose range specific to its calibration and may be clinically unacceptable for lower doses, less than 1Gy.