Hello, we are using both fmriprep amd tedana in out lab. I noticed that the _desc-preproc_bold output by fmriprep and the _desc-optcom_bold output by tedana, both, supposedly containing tedana optimally combined echoes, are not equal, especially where SNR is low. See attachemnt: top right tedana, bottom right fmriprep, top left ratio, bottom left difference.
Admittedly, the tSNR is almost identical (overlay on the right), but series are not, also in good SNR areas.
Is there any explanation for that (ie different steps etc) ?
Best reagrds and thank you in advance, federico
Hi @Federico_G,
In our data, we also observed some differences if we used the same echoes as input to tedana. However, these differences were minor and we considered them as related to numerical precision. For instance, it is possible that the voxelwise estimates of the weights for the T2*-weighted combination are slightly different between TEDANA abd fMRIprep. Yet, as I said they were minor for our data. Considering that you are using AFNI to present the results, would you mind plotting the timecourses on top of each other using the Dataset [N] option in AFNI with different colors? Such a plot would allows us to see the degree of these differences.
Thanks very much
So it seems that the estimates are actually very similar for the majority of voxels, corroborating our observations. Even in those voxels where the timeseries have different mean, the trend of the fluctuations seem very similar. What if you did a simple detrending, Opt → Detrend → 0 or 1?
To me, mean differences are probably related to minor differentes in the weights for echo combination.
