GABA MEGA-PRESS with macromolecule suppression

MRS Software Osprey
1

Hi, everyone,

Which option would you recommend in Osprey for fitting MM suppressed mega-press data for GABA?
opts.fit.fitMM = 0 or 1?
opts.fit.coMM3 =
‘3to2MM’ / ‘3to2MMsoft’ / ‘1to1GABA’ / ‘1to1GABAsoft’ / ‘freeGauss’ / ‘fixedGauss’ / ‘none’ ?

Best regards

2
  1. You’ll need a specific basis set, Osprey does not come with an MM-suppressed one
  2. You’ll want to include MMs (we know even the 3-ppm MMs are never perfectly nulled in the difference spectrum, and you’ll also still have MMs in the edit-off spectrum). However, none of the pre-available options will be really viable - they’ve all been derived from large datasets for the classic TE = 68 ms GABA+ experiment. You’ll need to come up with your own optimal parametrization, I’m afraid.
3

Thanks @admin, fits look better with a newly generated basis set for MM suppression.
I’ve tried freeGauss and things seem to be okay. Is the ‘none’ option going to fit the whole 3-ppm range peak as GABA and neglect any possible MM at all?

4

Yeah, none just doesn’t add any MM30 basis function whatsoever.
If the actual signal isn’t pure GABA (which it won’t be), you’ll likely get some unknown fit residual (and the baseline is likely to absorb at least some part of the signal).

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