How to add first echo of dual-echo data as regressor to GLM

Hi all,

I successfully preprocessed my dual echo data with fmriprep and I read in another thread that fmriprep follows the suggestion for dual echo data to use the first echo as nuisance regressor in the GLM (Fmriprep does not combine multi-echo timeseries).

I would like to try this approach with my data and was wondering if someone could provide some help on how exactly I incorporate my first echo in the GLM. Which data do I use for this?

Thanks a lot for your help!

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I don’t have any experience with dual-echo data, but my understanding of the Bright paper is that you would include the preprocessed TE1 data as voxelwise regressors for the preprocessed TE2 data in the GLM. The files I would use (assuming you used fMRIPrep) would just be the preprocessed data in whichever space you want to do your analysis (e.g., *_echo-1_space-T1w_desc-preproc_bold.nii.gz). I also believe that FEAT supports voxelwise confound regressors.

Does that help?

Hi Tsalo,

Thanks a lot for your reply! I’ll have a look at this option in FEAT and try it. I wasn’t aware of this since I’ve been doing most of my analyses in SPM so far. Do you happen to know if this option exists in SPM?

To be honest, I haven’t used voxel-wise regressors in any package, but I can’t find any information on doing it in SPM or AFNI.

Edit: AFNI’s 3dTProject has the -dsort argument that allows you to specify voxel-wise confounds. I still can’t find anything for SPM.