A practical guide to robust detection of GABA in human brain by J-difference spectroscopy at 3 T using a standard volume coil

Abstract

Abstractγ-Aminobutyric acid (GABA) is the major inhibitory neurotransmitter in human brain and has been implicated in several neuropsychiatric disorders. In-vivo human brain GABA concentrations are near the detection limit for magnetic resonance spectroscopy (∼1 mM) and because of overlap with more abundant compounds, spectral editing is generally necessary to detect GABA. In previous reports, GABA spectra edited by J-difference spectroscopy vary considerably in appearance. We have evaluated the factors that affect GABA spectra and the conditions necessary for robust acquisition of J-difference spectra from arbitrary brain regions. In particular, we demonstrate that variations in spectral quality can be explained in part by the incoherent addition of transients that results from shot to shot frequency and phase variations. An automated time-domain spectral alignment strategy is presented that enables reproducible acquisition of high-quality GABA spectra at 3 Tesla with a standard 30 cm T/R volume coil. Representative GABA spectra from human frontal lobe, an area where susceptibility-induced frequency and phase variations are especially troublesome, are presented that demonstrate the robustness of the acquisition and data handling strategy used in this study.

Individual Differences in the Balance of GABA to Glutamate in pFC Predict the Ability to Select among Competing Options

“…No attempts were made to correct for possible coedited macromolecular resonances, and as such, we henceforth refer to the GABA signals as GABA + . Although some have argued for using the creatine resonance as a frequency reference (Waddell, Avison, Joers, & Gore, 2007), we found the internal water referencing used here worked well for this purpose.…”

“…We assumed Gaussian line shapes, with frequency, line width, and amplitude as the fitted parameters. Because the “true” line shape of the edited GABA + has been characterized as a “pseudo doublet” (Waddell et al, 2007) with fine structure from three lines we fit GABA + signals at ~3.02 ppm in the spectrum using three Gaussians. Mullins et al (2012) recommend using a single Gaussian for these fits; however, we have found that the three Gaussian approach results in lower chi-square values and better fits visually.…”

The role of inhibition in human motor cortical plasticity

“…A disadvantage of this approach, as with all editing methods, is its reliance upon the subtraction of signals to remove strong overlapping frequencies from the spectrum in order to reveal GABA (Puts and Edden, 2012). This subtraction approach can be sensitive to any experimental noise such as subject movement or instrumental factors, which can then obscure the edited GABA signal (Waddell et al, 2007). Furthermore, some protein-containing macromolecules (Behar et al, 1994) resonate at a frequency coupled to a resonance near the GABA peak.…”

Vitamin D3Supplemental Treatment for Mania in Youth with Bipolar Spectrum Disorders

“…For diagnostic and localization purposes, T1-weighted anatomical MRI (magnetization-prepared rapid acquisition with gradient echo [MPRAGE] sequence) was collected; 1 H MRS data were acquired using the single voxel point-resolved spectroscopy sequence (PRESS) (TE, 28 msec; TR, 2000 msec; 128 averages; voxel, 20 mm · 20 mm · 20 mm) to quantify brain glutamate and Mescher-Garwood point-resolved spectroscopy sequence (MEGA-PRESS) (TE, 68 msec; TR, 2000 msec; 16 averages · 20 dynamic scans; voxel, 30 mm · 30 mm · 20 mm) to quantify brain GABA (Mescher et al 1998;Waddell et al 2007). Voxels were placed in the ACC by a trained spectroscopist (E.M.S.)…”