ELIMINATION OF SURFACE SIGNALS BY A SURFACE-SPOILING MAGNETIC-FIELD GRADIENT - THEORETICAL OPTIMIZATION AND APPLICATION TO HUMAN INVIVO NMR-SPECTROSCOPY

W. Chen and J. J. H. Ackerman (J. Magn. Reson. 82, 655, 1989; NMR Biomed. 2, 267, 1989) used a superficial magnetic field gradient to eliminate surface signals when observing rat liver in vivo. We have developed a method for computing the optimal gradient coil for a given in vivo application. An analytical solution for the magnetic field created by a planar array of antiparallel current elements was derived for the calculations. The surface-signal suppression obtained by gradient coils of various sizes is presented in a synthetic plot which directly provides the electrical and geometrical parameters of the optimal coil as well as the residual signal in the deep-lying region of interest. This approach was applied to in vivo 31P and 31C spectroscopy of the human liver. Hepatic glycogen was detected by natural-abundance 13C NMR without contamination from muscle glycogen, and physiological variation during starvation could be observed. © 1991.