Electron paramagnetic resonance (EPR) in medical dosimetry

Abstract

This paper describes the fundamentals of electron paramagnetic resonance (EPR) and its application to retrospective measurements of clinically significant doses of ionizing radiation. X-band is the most widely used in EPR dosimetry because it represents a good compromise between sensitivity, sample size and water content in the sample. Higher frequency bands (e.g., W and Q) provide higher sensitivity, but they are also greatly influenced by water content. L and S bands can be used for EPR measurements in samples with high water content but they are less sensitive than X-band. Quality control for therapeutic radiation facilities using X-band EPR spectrometry of alanine is also presented.

The comparison of the proton dose distribution calculated with the treatment planning system and measured with alanine detectors in the eye phantom irradiated under therapeutic conditions

“…The most substantial advantages of the alanine detectors in contrast to different types of passive dosimeters are their non-destructive read-out and low fading (Schauer et al, 2007;Ahlers and Schneider, 1991), making them a type of "dose archive" that maintains the dose record for documentation.…”

Application of alanine dosimetry in dose assessment for ocular melanoma patients undergoing proton radiotherapy – preliminary results

“…The concentration of these free radicals can be measured quantitatively by electron paramagnetic resonance (EPR) [2,3]. In our study, pellet-shaped alanine detectors, of 3 mm thickness and 4.8 mm diameter purchased from Synergy Health (Radeberg, Germany), were used As given by the manufacturer, these detectors are composed of 96 wt% alanine and 4 wt% binding material (polyethylene and additives).…”

“…In the presently used treatment setup, during patient irradiation, dose delivery is controlled by a system based on transmission ion chambers only -therefore, an independent method of verifying the dose delivered to the patient's PTV is highly desirable. Alanine dosimetry appears to be a good candidate, as it is a passive dosimeter exhibiting a linear dose response dependence in the therapeutic dose range and a stable, re-readable ESR signal [2,3]. By successively reading out via ESR spectrometry (without destroying the free-radical signal) the dose accumulated in consecutive fractional exposures, both individual dose per fraction and its fi nal accumulated value, can be read out and recorded for each patient.…”

Electron Paramagnetic Resonance Retrospective Dosimetry

“…The other important advantage of Q-band is full resolution of the radiation-induced EPR signal from the native background signal. This signal separation makes dose response measurements much easier in comparison with conventional X-band measurements in which these signal overlap (see for details [2,10]). The small samples obtained demonstrated well-resolved EPR radiation-induced signals for doses of approximately 0.5 Gy.…”

“…Furthermore, there are numerous reviews and reports devoted to retrospective EPR dosimetry. Among them, references [2][3][4][5][6][7][8][9][10][11][12] can be mentioned. This paper does not aim to provide an overview of the most recent developments and/or applications of EPR retrospective dosimetry.…”