Study of stability of radiation-induced EPR signals in sorbitol.

Purpose: The aim of this study is to investigate the stability of radiation-induced electron paramagnetic resonance (EPR) signals in sorbitol and to determine the spectroscopic characteristics of the radiation-induced radicals in sorbitol.

Materials and methods: Sorbitol samples were irradiated at 10 Gy using a 6 MV X-ray beam of medical linear accelerator (LINAC). EPR measurements were carried out using X-band (Bruker ESR5000X, and EMX-131) and Q-band (Bruker EMXplus) spectrometers. Isochronal and isothermal annealing experiments, as well as fading experiments, were carried out to assess the stability of radiation-induced signals. EasySpin simulation software was used to determine the spectroscopic and structural parameters of the radiation-induced radicals.

Results: The EPR spectrum of irradiated sorbitol consists of several overlapping components produced by stable and unstable radicals. X- and Q-band measurements revealed significant changes in the signal patterns during time fading and thermal annealing experiments. High-temperature annealing caused rapid decay of the unstable radicals, leaving behind a stable radical. Simulation calculations indicated that at least three components were required to reproduce the observed EPR spectra. Spectroscopic parameters derived from simulations showed consistent agreement across the different experimental conditions.

Conclusion: Sorbitol shows promising characteristics as an EPR dosimeter, with radiation-induced radicals exhibiting distinct thermal and time stability. High-temperature annealing can eliminate unstable radicals, enabling reliable dosimetric application shortly after irradiation. The identified stable radical is a promising marker for dose quantification. These findings support the feasibility of using sorbitol for retrospective and accidental dosimetry.