Glutamate measurements using edited MRS

Purpose To demonstrate J‐difference coediting of glutamate using Hadamard encoding and reconstruction of Mescher‐Garwood‐edited spectroscopy (HERMES). Methods Density‐matrix simulations of HERMES (TE 80 ms) and 1D J‐resolved (TE 31–229 ms) of glutamate (Glu), glutamine (Gln), γ‐aminobutyric acid (GA...

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Published in:Magnetic resonance in medicine 2024-04, Vol.91 (4), p.1314-1322
Main Authors: Saleh, Muhammad G., Prescot, Andrew, Chang, Linda, Cloak, Christine, Cunningham, Eric, Subramaniam, Punitha, Renshaw, Perry F., Yurgelun‐Todd, Deborah, Zöllner, Helge J., Roberts, Timothy P. L., Edden, Richard A. E., Ernst, Thomas
Format: Article
Language:English
Subjects:
Coefficient of variation
Editing
Experiments
GABA
gamma-Aminobutyric Acid - chemistry
glutamate
Glutamic Acid
Glutamine
Glutathione
Glutathione - chemistry
HERMES
Humans
In vivo methods and tests
J‐difference
Magnetic Resonance Imaging
Magnetic Resonance Spectroscopy - methods
Simulation
Spectroscopy
γ-Aminobutyric acid
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Summary:Purpose To demonstrate J‐difference coediting of glutamate using Hadamard encoding and reconstruction of Mescher‐Garwood‐edited spectroscopy (HERMES). Methods Density‐matrix simulations of HERMES (TE 80 ms) and 1D J‐resolved (TE 31–229 ms) of glutamate (Glu), glutamine (Gln), γ‐aminobutyric acid (GABA), and glutathione (GSH) were performed. HERMES comprised four sub‐experiments with editing pulses applied as follows: (A) 1.9/4.56 ppm simultaneously (ONGABA/ONGSH); (B) 1.9 ppm only (ONGABA/OFFGSH); (C) 4.56 ppm only (OFFGABA/ONGSH); and (D) 7.5 ppm (OFFGABA/OFFGSH). Phantom HERMES and 1D J‐resolved experiments of Glu were performed. Finally, in vivo HERMES (20‐ms editing pulses) and 1D J‐resolved (TE 31–229 ms) experiments were performed on 137 participants using 3 T MRI scanners. LCModel was used for quantification. Results HERMES simulation and phantom experiments show a Glu‐edited signal at 2.34 ppm in the Hadamard sum combination A+B+C+D with no overlapping Gln signal. The J‐resolved simulations and phantom experiments show substantial TE modulation of the Glu and Gln signals across the TEs, whose average yields a well‐resolved Glu signal closely matching the Glu‐edited signal from the HERMES sum spectrum. In vivo quantification of Glu show that the two methods are highly correlated (p 
ISSN:0740-3194
1522-2594
DOI:10.1002/mrm.29929