Simultaneous measurement of glutamate, glutamine, GABA, and glutathione by spectral editing without subtraction.

Abstract

To simultaneously measure glutamate, glutamine, γ-aminobutyric acid (GABA), and glutathione using spectral editing without subtraction at 7T. A novel spectral editing approach was proposed to simultaneously measure glutamate, glutamine, GABA, and glutathione using a TE of 56 ms at 7T. By numerical optimization of sequence timing in the presence of an editing pulse, the 4 metabolites all form relatively intense pseudo singlets with maximized peak amplitudes and minimized peak linewidths in 1 of the 3 interleaved spectra. For measuring glutamate, glutamine, and glutathione, the editing pulse targets the H3 protons of these metabolites near 2.12 parts per million. Both GABA H2 and H4 resonances are fully utilized in spectral fitting. Concentration levels (/[total creatine]) of glutamate, glutamine, GABA, and glutathione from an 8 mL voxel in the pregenual anterior cingulate cortex of 5 healthy volunteers were found to be 1.26 ± 0.13, 0.33 ± 0.06, 0.13 ± 0.03, and 0.27 ± 0.03, respectively, with within-subject coefficient of variation at 3.2%, 8.2%, 7.1%, and 10.2%, respectively. The total scan time was less than 4.5 min. The proposed new technique does not require data subtraction. The 3 major metabolites of the glutamatergic and GABAergic systems and the oxidative stress marker glutathione were all measured in 1 short scan with high precision.