Improved proton spectroscopic U-FLARE imaging for the detection of coupled resonances in the rat brain in vivo.

Modifications of the pulse sequence for spectroscopic U-FLARE imaging are discussed to detect not only the predominant singlet signals of N-acetylaspartate, total creatine, and choline containing compounds or the doublet signal of lactate, but also the coupled resonances of glutamate, glutamine, taurine and myo-inositol. Effective homonuclear decoupling is achieved by use of constant time chemical shift encoding. A maximum signal-to-noise ratio (SNR) can be obtained for a certain coupled resonance of interest by optimizing the evolution period t(c) of the J modulated spin echo. Good reproducibility and a high SNR were achieved by combining several methods for water suppression and by using the displaced variant of U-FLARE. Measurements of a 3 mm slice of the rat brain were performed in vivo within 4 min, giving a nominal voxel size of 1.5 x 1.5 x 3.0 mm3 or 1.5 x 0.75 x 3.0 mm3. Thus, optimized spectroscopic U-FLARE is a powerful tool for proton spectroscopic imaging with high spectral, spatial and temporal resolution.