MEGA-PRESS -Glutathione

Study & Experiment Design
1

Hi, Can I take a standard MEGA‑PRESS GABA sequence and modify it to edit Glutathione instead of using a dedicated GSH sequence? Specifically, would it work if I simply change the editing‑pulse frequencies to 4.56 ppm (ON) and 7.50 ppm (OFF) with a bandwidth of 70 Hz? If this modification is valid, can I also use Gannet for the post‑processing?

Thanks

2

Hi Rajakumar,

  1. Yes, you can simply move the edit-ON editing pulse frequency to 4.56 ppm and leave the bandwidth as it is.
  2. Some papers recommend longer echo times for optimal GSH editing, but TE = 68 ms works pretty well too (Dikoma Shungu’s group has published multiple papers doing GSH editing at this echo time)
  3. The answer whether you can use Gannet out of the box will depend on the choice of echo time, because the simplified Gannet model of the co-edited aspartyl does not generalize well to changes in echo time. If you want to use any kind of linear-combination model instead (LCModel, Osprey, FSL etc.), generating a TE-appropriate basis set will be pretty straightforward.

Cheers,
Georg

3

Thanks, Georg for your suggestion.

4

I would like to acquire muscle MRS using a TR of 3000ms and TE of 120 ms with 128 averages. I plan to focus on a single muscle to minimize B₀ inhomogeneity and reduce intramuscular heterogeneity. Do you have recommendations on the optimal muscle choice, voxel placement, or acquisition strategy for this setup?