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

Metabolite signals with short T-1 or T-2 are difficult to localize with ful l sensitivity. This limitation was overcome with the development and implem entation of a single-shot, complete three-dimensional "non-echo" localizati on method with reduced sensitivity to spatial B-1 variation, which is suita ble for measuring signals with very short T-1 or T-2, e.g., the C-13 NMR si gnals of glycogen. The proposed method is based on a T-1-optimized outer vo lume suppression scheme using pulses of the hyperbolic secant type applied at different power levels, which is robust over a fivefold range of T-1. St rong lipid, muscle glycogen, and glucose signals originating outside the ra t brain were suppressed. Signals of glycogen, aspartate, glutathione, GABA C4, N-acetyl aspartate as well as the C3 and C4 signals of glutamate and gl utamine with resolved homonuclear C-13-C-13 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.