Development of an electron spin resonance spectroscopy code for measuring carbonate radicals in tooth enamel and verification of its practicality using irradiated Japanese macaque teeth.

Purpose: We developed a new computer program for the application of electron spin resonance (ESR) to dosimetry of wild animals related to the Fukushima Daiichi Nuclear Power Plant accident.

Materials & methods: The ESR spectra of carbonate radicals and other inorganic radicals are calculated by the complete elliptic integral. A simulated annealing method is implemented for the parameter optimization. A cost function is designed to include the second derivative form of the microwave absorption spectrum to improve the fitting accuracy. As a testing ground for the developed code, we prepared tooth enamel samples from a Japanese macaque captured in a control area.

Results: The developed code well reproduced the measured ESR spectrum. With a test spectrum, we demonstrated that the cost function that includes the second derivative form of the microwave absorption spectrum is helpful for the precise analysis of the low-dose enamel samples. The smoothness of the ESR spectrum plays an important role in utilizing this feature.

Conclusion: The developed computer code can be used to analyze the ESR spectrum of tooth enamels of Japanese macaques. A precise analysis is essential to lower the detection limit and expand the applicability of ESR dosimetry. The code is independent of the computer operating system and is available publicly.