Simultaneous edited MRS of GABA, glutathione, and ethanol

Abstract

The aim of this work was to develop simultaneous edited MRS of γ‐aminobutyric acid (GABA), glutathione (GSH), and ethanol (EtOH) using Hadamard encoding and reconstruction of MEGA‐edited spectroscopy (HERMES) at 3T. Density‐matrix simulations of HERMES were carried out and compared with phantom experiments. In vivo experiments were performed in six healthy volunteers about 30 min after alcohol consumption. Simulations of HERMES showed GABA‐, GSH‐, and EtOH‐edited spectra with low levels of crosstalk and excellent agreement with phantom spectra. In vivo experiments showed well edited GABA signals at 3.0 ppm, GSH at 2.95 ppm, and EtOH at 1.18 ppm in the respective Hadamard combination spectra. Measured integral ratios were 0.082 ± 0.012 for GABA/Cr, 0.037 ± 0.006 for GSH/Cr, and 0.305 ± 0.129 for EtOH/Cr. Simulated, phantom, and in vivo measurements of HERMES show excellent separation of GABA‐, GSH‐, and EtOH‐edited signals with negligible levels of crosstalk. HERMES allows a threefold acceleration of editing while maintaining spectral quality compared with sequentially acquired MEGA‐PRESS measurements.

The trajectory of cortical GABA levels across the lifespan: An individual participant data meta-analysis of edited MRS studies

“…Future studies should provide concentration values across the lifespan. Recent developments in MRS of GABA methodology will allow for this, even when data is collected on multiple scanner platforms (Saleh et al, 2020). It should be noted that all datasets used for this meta-analysis were cross-sectional.…”

“…None of the data included were corrected for voxel tissue fractions (see Discussion). MEGA-PRESS sequences can vary between and within MRI vendors; these can impact editing efficiency and in turn absolute quantification (Harris et al, 2015;Saleh et al, 2020). However, the consequence of this will not impact the within-site relationship to age (the metric used in this review) as the consequences of such variation are stable within-site and function as a scaling factor (Mikkelsen et al, 2018).…”

Motion correction in magnetic resonance spectroscopy

“…Moreover, this method may not be applicable to edited MRSI data. Overall, as the multiplexed editing methods become more complex, 89,105 the multistep correction may require modification, or new methods may need to be developed. 106…”

“…A number of chemical compounds can be measured from a 1 H spectrum from the brain. These neurochemicals include glucose, glycerol, scyllo‐inositol, ethanol, 2‐hydroxyglutarate, phenylalanine, N‐acetylaspartate (NAA), choline‐containing compounds (Cho) such as glycerophosphocholine and phosphocholine, creatine‐containing compounds or total creatine, including phosphocreatine and creatine (Cr), myo‐inositol, N‐acetylaspartylglutamate, lactate, γ‐aminobutyric acid (GABA), ascorbate, aspartate, glutathione (GSH), glutamate, and glutamine 1,16‐19 …”

MR‐Nucleomics: The study of pathological cellular processes with multinuclear magnetic resonance spectroscopy and imaging in vivo

“…MRS or nuclear magnetic resonance (NMR) has been routinely used for ex vivo biochemical analysis, including the determination of protein structure and dynamics before the widespread introduction of cryo-electron microscopy. 10 With a long history in clinical practice, 11 proton-based MRS has made considerable advances in recent years in research on the detection of gamma amino butyric acid (GABA), glutathione, 12 glutamate, glutamine, 13 2-hydroxyglutarate, 14 and fumarate. 15 While a major limitation of proton-based MRS is the signals from water and lipid protons obscuring metabolite signals in vivo, MRS and MRSI can be used to detect many other biologically relevant nuclei in vivo, such as 2 H, 13 C, 15 N, 19 F, and 31 P, which do not suffer the same problem with background signals.…”