Fast 3D spatial EPR imaging using spiral magnetic field gradient

Abstract

Electron paramagnetic resonance imaging (EPRI) provides direct detection and mapping of free radicals. The continuous wave (CW) EPRI technique, in particular, has been widely used in a variety of applications in the fields of biology and medicine due to its high sensitivity and applicability to a wide range of free radicals and paramagnetic species. However, the technique requires long image acquisition periods, and this limits its use for many in vivo applications where relatively rapid changes occur in the magnitude and distribution of spins. Therefore, there has been a great need to develop fast EPRI techniques. We report the development of a fast 3D CW EPRI technique using spiral magnetic field gradient. By spiraling the magnetic field gradient and stepping the main magnetic field, this approach acquires a 3D image in one sweep of the main magnetic field, enabling significant reduction of the imaging time. A direct one-stage 3D image reconstruction algorithm, modified for reconstruction of the EPR images from the projections acquired with the spiral magnetic field gradient, was used. We demonstrated using a home-built L-band EPR system that the spiral magnetic field gradient technique enabled a 4 to 7-fold accelerated acquisition of projections. This technique has great potential for in vivo studies of free radicals and their metabolism.

Theory, Instrumentation, and Applications of Electron Paramagnetic Resonance Oximetry

“…The resulting data have lesser redundancy and generate better quality images. The performance of spinning gradient-based data acquisition has been explored for EPR by Deng et al 143. Usually, special low-inductance gradient coils are used to spin the gradients rapidly.…”

ESR Microscopy for Biological and Biomedical Applications

“…22,,25,26 De-oxygenated ~1 mM Trityl in 5 mM NaOH has a narrow single absorption peak of ~120 mG at 9 GHz, corresponding to a relatively long T 2 of ~4 μs at 15 GHz. Using this Trityl spin probe, relevant parameters, such as viscosity, molecular self diffusion, or partial oxygen pressure can be imaged in various biological samples.…”

Immuno-spin trapping of protein and DNA radicals: “Tagging” free radicals to locate and understand the redox process

“…EPRI often requires the use of narrow-line spin probes, such as trityl radicals [44]. These free radical nitroxide probes are often non-toxic and bio-compatible [45].…”