Simultaneous Editing of GABA and GSH with HERMES

The two most widely edited metabolites are GABA, the main inhibitory neurotransmitter, and Glutathione (GSH), the most abundant redox compound in the brain.  They give edited signals at 3 ppm and 2.95 ppm respectively, making them ideal candidates for simultaneous HERMES editing.

Building on Kim Chan's work, Muhammad Saleh has implemented a HERMES experiment that simultaneously and separably edits GABA and GSH.  HERMES uses a Hadamard editing scheme to encode the ON/OFF of J-difference orthogonally for GABA (at 1.9 ppm) and GSH (at 4.56 ppm). The inversion profiles of the four Experiments A-D look like:

Applying these pulses, evolution of couplings in the GABA molecule is refocused in the GABA-ON scans, and evolution of couplings in the GSH molecule is refocused in the GSH-ON scans, so that the combination A-B+C-D will give the GSH-edited spectrum, and A+B-C+D will give the GABA-edited spectrum.

Figure 3-01.png

In vivo, this allows single experiment to acquire data equivalent to two consecutive MEGA-PRESS acquisitions.