ABSTRACT
The impetus for low-frequency electron paramagnetic resonance (EPR) spectroscopy derives from the deeper penetration of lossy samples by the corresponding longer wavelengths. Low-frequency measurements in living animals have been attempted by a few groups. Low-frequency operation simplifies design of the spectrometer magnets enormously. Low-frequency EPR-spectroscopic imaging has the potential to provide information complementary to that provided by localized nuclear magnetic resonance (NMR) spectroscopy. The use of low frequency for EPR studies dates back to the discovery of EPR by Zavoisky. The motivation for in vivo EPR-spectroscopic imaging is based on the unique information it can provide. The generic kinds of information obtainable from NMR and EPR in vivo are likely to be complementary. Loop-gap resonators have made high filling-factor commonplace in EPR spectroscopy. In vivo imaging at low frequency should include, at some level, a spectral dimension. The generic kinds of information obtainable from NMR and EPR in vivo are likely to be complementary.
