A 3T MR scanner (Siemens) was used with a 32-channel head matrix coil in the Brown University MRI Research Facility. A high-resolution T1-weighted anatomical brain structure images were obtained using a magnetization-prepared rapid gradient echo (MPRAGE; 256 slices, voxel size = 1×1×1 mm3, 0 mm slice gap, TR=2530 ms, TE=1.64 ms, flip angle=7 degrees, FoV=256 mm, matrix size =256×256, bandwidth=651 Hz/pixel) sequence. The GABA scans were conducted using a MEGA-PRESS sequence55 (link)-57 (link) (TR=1500 ms, TE=68 ms, number of average=256, scan time=774 sec) with double-banded pulses which were used to simultaneously suppress water signal and edit the γ-CH2 resonance of GABA at 3 ppm. We obtained the final spectra by subtracting the signals from alternate scans with the selective double-banded pulse applied at 4.7 and 7.5 ppm (‘Edit Off’) and the selective double-banded pulse applied at 1.9 and 4.7 ppm (‘Edit On’).
The glutamate scans were conducted using the PRESS sequence58 (link),59 (link) (TR=3000 ms, TE=30 ms, number of average=128, scan time=384 sec). A variable pulse power and optimized relaxation delays (VAPOR) technique60 (link) was used in both sequences to achieve water suppression.
The glutamate scans were conducted using the PRESS sequence58 (link),59 (link) (TR=3000 ms, TE=30 ms, number of average=128, scan time=384 sec). A variable pulse power and optimized relaxation delays (VAPOR) technique60 (link) was used in both sequences to achieve water suppression.
