In vivo GABA detection by single-pulse editing with one shot

Two-shot γ-aminobutyric acid (GABA) difference editing techniques have been used widely to detect the GABA H4 resonance at 3.01 ppm. Here, we introduce a single-shot method for detecting the full GABA H2 resonance signal, which avoids contamination from the coedited M_3.00 macromolecules.

Density matrix simulation was conducted to optimize the pulse-sequence timing, aiming to reduce the interfering glutamate H4 signal and minimize the correlation between glutamate and GABA arising from spectral overlap. The optimized sequence was used to acquire MR spectroscopy data from a 14-mL voxel in the anterior cingulate cortex of 6 healthy participants. ¹H-MRS experiments following the oral administration of [U-¹³C]glucose were also conducted.

The GABA H2 peak was consistently observed in all participants. The GABA/creatine ratios in the participants were determined to be 0.07 ± 0.01 with Cramer-Rao lower bounds of 8.0% ± 2.2%. Spectra acquired following [U-¹³C]glucose intake demonstrated the feasibility of using GABA H2 as a highly sensitive reporter for GABA C2.

The proposed single-shot GABA editing method effectively minimizes interference from the glutamate H4 signal in the detection of the full GABA H2 signal, which resonates at a spectral region with much reduced macromolecule contamination.