Rapid Field Scan L-Band Electron Spin Resonance Computed Tomography System Using an Air-Core Electromagnet

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Abstract
A rapid field scan L-band electron spin resonance computed tomography (ESR-CT) system has been developed in order to obtain three-dimensional images of the distribution of free radicals in a sample. The ESR system comprises an L-band (ca. 700MHz) ESR spectrometer, an air-core electromagnet equipped with a field-scanning coil, three field-gradient coils, and a microcomputer. The rapid field scan (15mT/s) causes a delay in the magnetic-field strength due to eddy-current losses. However, it was found that the magnetic field strength could be corrected by a simple mathematical equation related to a low-pass filter model. Using this system, the original ESR data used to obtain one three-dimensional ESR-CT image could be obtained in 150s. The time course of the ESR-CT images of the test sample containing the reaction of nitroxide radical with ascorbate ion has been shown as an example of a spatiotemporal measurement.