Regional distributions of brain glutamate and glutamine in normal subjects

• Published in: NMR in biomedicine Vol. 29; no. 8; pp. 1108 - 1116
• Main Authors: Goryawala, Mohammed Z., Sheriff, Sulaiman, Maudsley, Andrew A.
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01.08.2016; Wiley Subscription Services, Inc
• Subjects: Adult; aging; Brain - metabolism; Female; glutamate; Glutamic Acid - metabolism; glutamine; Glutamine - metabolism; Humans; Image Enhancement - methods; Magnetic Resonance Imaging - methods; Magnetic Resonance Spectroscopy - methods; Male; Middle Aged; Molecular Imaging - methods; MRSI; Reference Values; Reproducibility of Results; Sensitivity and Specificity; Signal Processing, Computer-Assisted; spectroscopy; Tissue Distribution; aging; glutamine; spectroscopy; glutamate; MRSI
• ISSN: 0952-3480; 1099-1492; 1099-1492
• DOI: 10.1002/nbm.3575

Glutamate (Glu) and glutamine (Gln) play an important role in neuronal regulation and are of value as MRS‐observable diagnostic biomarkers. In this study the relative concentrations of these metabolites have been measured in multiple regions in the normal brain using a short‐TE whole‐brain MRSI measurement at 3 T combined with a modified data analysis approach that used spatial averaging to obtain high‐SNR spectra from atlas‐registered anatomic regions or interest. By spectral fitting of high‐SNR spectra this approach yielded reliable measurements across a wide volume of the brain. Spectral averaging also demonstrated increased SNR and improved fitting accuracy for the sum of Glu and Gln (Glx) compared with individual voxel fitting. Results in 26 healthy controls showed relatively constant Glu/Cr and Gln/Cr throughout the cerebrum, although with increased values in the anterior cingulum and paracentral lobule, and increased Gln/Cr in the superior motor area. The deep gray‐matter regions of thalamus, putamen, and pallidum show lower Glu/Cr compared with cortical white‐matter regions. Lobar measurements demonstrated reduced Glu/Cr and Gln/Cr in the cerebellum as compared with the cerebrum, where white‐matter regions show significantly lower Glu/Cr and Gln/Cr as compared with gray‐matter regions across multiple brain lobes. Regression analysis showed no significant effect of gender on Glu/Cr or Gln/Cr measurement; however, Glx/Cr ratio was found to be significantly negatively correlated with age in some lobar brain regions. In summary, this methodology provides the spectral quality necessary for reliable separation of Glu and Gln at 3 T from a single MRSI acquisition enabling generation of regional distributions of metabolites over a large volume of the brain, including cortical regions. Copyright © 2016 John Wiley & Sons, Ltd. This study reports relative concentrations of Glu and Gln over multiple regions in the normal brain using a single short‐TE whole‐brain MRSI measurement combined with a modified data analysis approach that uses atlas‐based spatial averaging to obtain high‐SNR spectra. The primary advantage of this methodology is that it provides the spectral quality necessary for reliable separation of Glu and Gln at 3 T from multiple brain regions using a single MRSI acquisition.