Hello
I am providing the same recipe I had provided for the fMRS.
I think I told this to @noeskera when we were developing the semi-laser sequence for the GE, too. I would suggest not to use the FASTMAP for second-order shims. FASTMAP should provide the best linewidths but does not necessarily result in the best/practical spectral quality. Start with GRESHIM and then update the first order shims with FASTMAP’s first-order procedure. I have also started to read that other studies are also following this procedure for difficult ROIs.
https://analyticalsciencejournals.onlinelibrary.wiley.com/doi/10.1002/nbm.4538
" B0 shimming was performed first on the whole brain volume with the standard “GRE Brain” option implemented in the scanner (Siemens) and then by manually adjusting the shim currents to a water linewidth below 30 Hz in magnitude mode. Next, the adjustment volume was changed to that of the VOI, and interactive shimming of the linear shim currents was performed to achieve a water linewidth below 20 Hz in magnitude mode. This sequential shimming volume approach (whole head, followed by VOI) allowed for satisfactory B0 homogeneity in the hippocampus and prevented the generation of spurious echoes from insufficient water suppression. A similar approach was used for hippocampal MRS at 7 T.
However, This is not the end of the story, your ROI is problematic for the default CMRR semi-laser RF pulse order. I would suggest you run the semi-laser with an orientation of coronal. The default CMRR semi-laser configuration is not working for this type of ROI. Again read my hints from the fMRS thread.