Reproducibility of Glutamate, Glutathione, and GABA Measurements in vivo by Single-Voxel STEAM Magnetic Resonance Spectroscopy at 7-Tesla in Healthy Individuals

Ofer M Gonen; Bradford A Moffat; Patrick Kwan; Terence J O'Brien; Patricia M Desmond; Elaine Lui

doi:10.3389/fnins.2020.566643

Reproducibility of Glutamate, Glutathione, and GABA Measurements in vivo by Single-Voxel STEAM Magnetic Resonance Spectroscopy at 7-Tesla in Healthy Individuals

Front Neurosci. 2020 Sep 15:14:566643. doi: 10.3389/fnins.2020.566643. eCollection 2020.

Authors

Ofer M Gonen^{1

2

3}, Bradford A Moffat², Patrick Kwan^{1

2

3

4}, Terence J O'Brien^{1

2

3

4}, Patricia M Desmond^{2

5}, Elaine Lui^{2

5}

Affiliations

¹ Department of Neurology, The Royal Melbourne Hospital, Parkville, VIC, Australia.
² Department of Medicine and Radiology, The University of Melbourne, Parkville, VIC, Australia.
³ Department of Neurology, The Alfred Hospital, Melbourne, VIC, Australia.
⁴ Department of Neuroscience, Central Clinical School, Monash University, Melbourne, VIC, Australia.
⁵ Department of Radiology, The Royal Melbourne Hospital, Parkville, VIC, Australia.

Abstract

Background and purpose: Derangements in brain glutamate, glutathione, and γ-amino butyric acid (GABA) are implicated in a range of neurological disorders. Reliable methods to measure these compounds non-invasively in vivo are needed. We evaluated the reproducibility of their measurements in brain regions involved in the default mode network using quantitative MRS at 7-Tesla in healthy individuals.

Methods: Ten right-handed healthy volunteers underwent 7-Tesla MRI scans on 2 separate days, not more than 2 weeks apart. On each day two scanning sessions took place, with a re-positioning break in between. High-resolution isotropic anatomical scans were acquired prior to each scan, followed by single-voxel ¹H-MRS using the STEAM pulse sequence on an 8 mL midline cubic voxel, positioned over the posterior cingulate and precuneus regions. Concentrations were corrected for partial-volume effects.

Results: Maximal Cramér-Rao lower bounds for glutamate, glutathione, and GABA were 2.0, 8.0, and 14.0%, respectively. Mean coefficients of variation within sessions were 5.9 ± 4.8%, 9.3 ± 7.6%, and 11.5 ± 8.8%, and between sessions were 4.6 ± 4.5%, 8.3 ± 5.7%, and 9.2 ± 8.7%, respectively. The mean (±SD) Dice's coefficient for voxel overlap was 90 ± 4% within sessions and 86 ± 7% between sessions.

Conclusion: Glutamate, glutathione, and GABA can be reliably quantified using STEAM MRS at 7-Tesla from the posterior cingulate and precuneus cortices of healthy human subjects. STEAM MRS at 7-Tesla may be used to study the metabolic behavior of this important resting-state hub in various disease states.

Keywords: STEAM; default mode network; magnetic resonance spectroscopy; posterior cingulate cortex; precuneus; reproducibility.