Selective Resonance Suppression H-1-[C-13] NMR Spectroscopy With Asymmetric Adiabatic RF Pulses

Despite obvious improvements in spectral resolution at high magnetic field, the detection of C-13 labeling by H-1-[C-13] NMR spectroscopy remains hampered by spectral overlap, such as in the spectral region of H-1 resonances bound to C3 of glutamate (Glu) and glutamine (Gin), and C6 of N-acetylaspartate (NAA). The aim of this study was to develop, implement, and apply a novel H-1-[C-13] NMR spectroscopic editing scheme, dubbed "selective Resonance suppression by Adiabatic Carbon Editing and Decoupling single-voxel STimulated Echo Acquisition Mode" (RACED-STEAM). The sequence is based on the application of two asymmetric narrow-transition-band adiabatic RF inversion pulses at the resonance frequency of the C-13 coupled to the protons that need to be suppressed during the mixing time (TM) period, alternating the inversion band downfield and upfield from the C-13 resonance on odd and even scans, respectively, thus suppressing the detection of H-1 resonances bound to C-13 within the transition band of the inversion pulse. The results demonstrate the efficient suppression of H-1 resonances bound to C3 of Glu and Gin, and C4 of Glu, which allows the H-1 resonances bound to C6 of NAA and C4 of Gin to be revealed. The measured time course of the resolved labeling into NAA C6 with the new scheme was consistent with the slow turnover of NAA. Magn Reson Med 61:260-266, 2009. (c) 2009 Wiley-Liss, Inc.