Single-shot, three-dimensional 'non-echo' localization method for in vivo NMR spectroscopy

Metabolite signals with short T1 or T2 are difficult to localize with full sensitivity. This limitation was overcome with the development and implementation of a single-shot, complete three-dimensional 'non-echo' localization method with reduced sensitivity to spatial B1 variation, which is suitable for measuring signals with very short T1 or T2, e.g., the 13C NMR signals of glycogen. The proposed method is based on a T1-optimized outer volume suppression scheme using pulses of the hyperbolic secant type applied at different power levels, which is robust over a fivefold range of T1. Strong lipid, muscle glycogen, and glucose signals originating outside the rat brain were suppressed. Signals of glycogen, aspartate, glutathione, GABA C4, N-acetyl aspartate as well as the C3 and C4 signals of glutamate and glutamine with resolved homonuclear 13C-13C coupling were fully resolved in vivo at 9.4 Tesla using higher-order shimming. The method can be extended to other nuclei and to localized MRS of humans. (C) 2000 Wiley-Liss, Inc.