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Abstract
High-resolution proton NMR spectra of normal human brain in vivo have been obtained from selected 27- and 64-ml volumes-of-interest (VOI) localized in the insular area, the occipital area, the thalamus, and the cerebellum of normal volunteers. Localization was achieved by stimulated echo (STEAM) sequences using a conventional 1.5-T whole-body MRI system (Siemens Magnetom). The proton NMR spectra show resonances from lipids, lactate, acetate, N-acetylaspartate (NAA), gamma-aminobutyrate, glutamine, glutamate, aspartate, creatine and phosphocreatine, choline-containing compounds, taurine, and inositols. While T1 relaxation times of most of these metabolites were about 1100-1700 ms without significant regional differences, their T2 relaxation times varied between 100 and 500 ms. The longest T2 values of about (500 +/- 50) ms were observed for the methyl protons of NAA in the white matter of the occipital lobe compared to (320 +/- 30) ms in the other parts of the brain. No significant regional T2 differences were found for choline and creatine methyl resonances. The relative concentrations of NAA in gray and white matter were found to be 35% higher than those in the thalamus and cerebellum. Assuming a concentration of 10 mM for total creatine the resulting NAA concentrations of 13-18 mM are by a factor of 2-3 higher than previously reported using analytical techniques. Cerebral lactate reached a maximum concentration of about 1.0 mM.
Highlights
Complementary to anatomical and functional studies by magnetic resonance imaging (MRI), localized in vivo NMR spectroscopy opens the way to a biochemical characterization of tissues and their diseased states
In preceding papers [2,3,4] we have demonstrated that stimulated echo (STEAM) spectroscopy provides a simple solution that is suited to proton NMR
The 4 X 4-cm2squares in the axial and coronal images (Figs. 1a and 1b) define a 64-ml VOI in the occipital area which has been selected for spectroscopy of predominantly white matter
Summary
Complementary to anatomical and functional studies by magnetic resonance imaging (MRI), localized in vivo NMR spectroscopy opens the way to a biochemical characterization of tissues and their diseased states. Noninvasive insights may be gained into the metabolism of a variety of compounds within the whole living organism. Many biochemical and physiological questions may be investigated in human subjects rather than in animals, avoiding the need of anesthesia and associated physiological complications as well as the uncertainties in establishing a correlation between animal studies and human applications. Proton NMR spectroscopyis expected to broaden our understanding of metabolic processes in viva The abundant representation of protons in molecules. A11 Wts of reproduction in any form resrrved.
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