Whether to perform ECC when fitting 'diff' spectra using LCModel and Why?

Hi everyone,

I’m not sure whether to perform ECC (Eddy Current Correction) when fitting the ‘diff’ spectrum using LCModel in the analysis of MEGA-PRESS or MEGA-sLASER. Can anyone provide me with some advice?

Thank you!


That depends. How did you create the difference spectrum? I would lean towards ECC-ing the edit-ON and edit-OFF before aligning (and subtracting) them.

Thank you Georg!

My previous approach was to skip ECC during the preprocessing stage, load the difference spectrum into LCModel, and then apply ECC. Would skipping ECC introduce greater uncertainty for alignment and frequency and phase correction?

I don’t have a lot of evidence to back that feeling up, but my instinct would be yes.

Side note: I don’t know which sequence implementation you have, but make sure you are using a water reference that actually has a water signal. The old Siemens implementations would return three .RDA files (which you shouldn’t use anyway!), one for the edit-ON, one for the edit-OFF, and one for the DIFF spectrum. For water reference data, the DIFF spectrum was obviously flat (water subtracted from water), and one needed to use one of the two halves for ECC and water referencing (with disastrous disagreement over whether a correction factor of 2 was needed, but that’s another story…).

Hi Georg,
In fact, I work with data in Siemens .dat or .IMA formats. Nevertheless, I greatly appreciate your prompt reply and kind reminder. I will keep your advice in mind.