GABA quantitation using MEGA-PRESS: Regional and hemispheric differences

Abstract

Purpose To measure in vivo brain gamma-aminobutyric acid (GABA) concentrations, and assess regional and hemispheric differences, using MR spectroscopy (1H-MRS). Materials and Methods GABA concentrations were measured bilaterally in the frontal cortex (FC), parietal cortex (PC), and occipital cortex (OC) of 21 healthy young subjects (age range 20–29 years) using 3 Tesla Philips scanner. A univariate general linear model analysis was carried out to assess the effect of region and hemisphere as well as their interaction on GABA concentrations while controlling for sex and gray matter differences. Results Results indicated a significant regional dependence of GABA levels [F(2,89) =11.725, P < 0.001, ηp2=.209] with lower concentrations in the FC compared with both PC (P < 0.001) and OC (P < 0.001) regions. There was no significant hemispheric differences in GABA levels [F(1,89) =.172; P =0.679; ηp2=.002]. Conclusion This study reports the concentrations of GABA in the FC, PC, and OC brain regions of healthy young adults. GABA distribution exhibits hemispheric symmetry, but varies across regions; GABA levels in the FC are lower than those in the PC and OC.

Distinction of the GABA 2.29 ppm resonance using triple refocusing at 3 T in vivo

“…Discrepancy between our estimation and previous MEGA GABA measurements at 3 T are also seen in other brain regions. Frontal‐brain GABA was measured as 1.4 to 2.1 mM in previous studies at 3 T, which is higher than our estimate (0.87 mM). For PC, our estimate of 0.66 mM in a 7‐mL voxel is approximately 50% relative to a previous MEGA study in an 18‐mL voxel .…”

“…A recent study, which aimed to find regional differences of GABA at 3 T, reported 2.7 mM of GABA in the MO cortex. 30 Several other 3T studies using MEGA reported MO GABA/tCr of 0.15 to 0.2, 31-33 which corresponds to 1.2 to 1.6 mM when the tCr level is set to 8 mM. Discrepancy between our estimation and previous MEGA GABA measurements at 3 T are also seen in other brain regions.…”

“…Compared with these previous MEGA studies, our GABA estimate in MO brain (0.8 mM, ∼12 mL voxels) is notably lower. A recent study, which aimed to find regional differences of GABA at 3 T, reported 2.7 mM of GABA in the MO cortex . Several other 3T studies using MEGA reported MO GABA/tCr of 0.15 to 0.2, which corresponds to 1.2 to 1.6 mM when the tCr level is set to 8 mM.…”

Enhancing Value of MRI: A Call for Action

“…Recent advances in molecular MRI expand the capability of MRI even further. Molecular probes activated by an enzyme and localized by nanoparticles, molecular imaging biomarkers for metabolites of activated T cells for immunotherapy, hyperpolarized gas‐enhanced MRI, and quantitative analysis of MR spectroscopy of glutathione, gamma‐aminobutyric acid (GABA), glutamate, with high accuracy and reproducibility are just a few examples. MRI continues to contribute to the scientific discovery and understanding of many diseases that were never thought possible.…”

Inhibitory motor dysfunction in parkinson's disease subtypes

“…The low concentration of GABA and the presence of overlapping signals from more concentrated metabolites render GABA measurements ambiguous using conventional 1 H-MRS at 3.0 T (7). As a result, a spectral editing technique, MEscher-GArwood Point Resolved Spectroscopy (MEGA-PRESS (8)), is widely used to remove overlapping signals, allowing observations of GABA levels in healthy and diseased patients (9–11). …”