NMR Microscopy by Radiofrequency Field Gradients

Abstract

This paper reports a method of NMR microimaging which employs exclusively radiofrequency field gradients, one in the transverse direction created by a single-turn coil and the other along the longitudinal direction generated by the saddle coil of the conventional probe used with vertical superconducting magnets. The basic experiment involves slice selection by means of the longitudinal gradient followed by the acquisition of the NMR signal in the presence of the transverse gradient. By rotating the object around the vertical axis in a stepped manner, a series of profiles is obtained whose analysis, including inter alia the filtered back-projection algorithm, provides a two-dimensional image. The experiment can be run routinely with a slightly modified conventional NMR spectrometer; emphasis is put on its relative immunity to B0 inhomogeneities and/or magnetic susceptibility variations across the object under investigation.