NMR MICROSCOPY BY RADIOFREQUENCY FIELD GRADIENTS

This paper reports a method of NMR microimaging which employs exclusiv ely radiofrequency field gradients, one in the transverse direction cr eated by a single-turn coil and the other along the longitudinal direc tion 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 acquis ition of the NMR signal in the presence of the transverse gradient. By rotating the object around the vertical axis in a stepped manner, a s eries 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 conventi onal NMR spectrometer; emphasis is put on its relative immunity to B-0 inhomogeneities and/or magnetic susceptibility variations across the object under investigation. (C) 1994 Academic Press, Inc.