Issues with Edit-Off Spectra Modeling Fit Quality in 3T Siemens rda Data

Analysis / Modeling
1

Hello everyone,

I am currently analyzing MEGA-PRESS sequence data (rda format) acquired from a 3T Siemens MRI system. I’m using LCModel for modeling, applying only water scaling without prior processing or eddy current correction (default settings).

In the edit-off spectra, I’ve noticed dips at 2.3 ppm and 3.5 ppm, whereas the difference spectra model fit appears normal. I am wondering if this behavior in the edit-off spectra is typical, and I would appreciate insights on what might be causing these dips.

Could anyone kindly review my model fit results and offer any suggestions on how I might improve my results? I would greatly appreciate your expert advice. Thank you!

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MMZHU

2

Can you clarify what you mean by ‘dips’? This doesn’t look too bad at all.

4

Thank your for your reply. The ‘dips’ I am referring to, highlighted in the green square. Is it normal?
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5

Yes - completely normal. The phases of coupled signals (like Glu, Gln, GSH etc.) change with TE. This is being accounted for during basis set simulation.

6

Thank you very much for the clarification!

MMZHU