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

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. 700 MHz) ESR spectrometer, an air-core electromagnet equipped with a field-scanning coil, three field-gradient coils, and a microcomputer.The rapid field scan (15 mT/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 150 s. 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.

Theory, Instrumentation, and Applications of Electron Paramagnetic Resonance Oximetry

“…Generally three types of magnets are utilized in the existing EPR imaging designs, namely, nonferrous electromagnets107, iron-core electromagnets108, and permanent magnets109. For low-field systems with static fields up to 500 Gauss, nonferrous electromagnets can be used.…”

A linear magnetic field scan driver

“…Other reports described ''rapid'' scan EPR spectra, but the scans were slower than would be needed for the spectra to be impacted by relaxation phenomena (29)(30)(31)(32)(33)(34)(35)(36)(37)(38). In some reported cases, there have been scan-rate-dependent field offsets or signal distortions (31,(34)(35)(36)(37), problems that do not occur with the system described here.…”

Dynamic electron spin resonance (ESR) imaging of the distribution of spin labeled dextran in a mouse

“…Data collection for two-dimensional (2D) and 3D image reconstruction was conducted on an ESR-CT system as described previously (16)(17)(18). The magnetic field gradient was 0.1 mT/m.…”