Use of defaced T1w in fMRIprep: how to organise data?

Dear all,

I have acquired data, and I obtain this kind of BIDS folder using dcm2bids:

  • anat = T1w
  • fmap = SE A>>P and P
  • func = 4D images

I am running fMRIprep on it, and everything is just fine.

I have just learned about defacing. From my understanding, one should deface anatomical images before running fMRIprep. My question in this regard is: how to organise and name data?

dcm2bids:

anat
|_ sub-01_T1w.json
|_ sub-01_T1w.nii.gz

dcm2bids + defacing: (e.g., using PyDeface)

anat
|_ sub-01_T1w.json
|_ sub-01_T1w.nii.gz
|_ sub-01_T1w_defaced.nii.gz

Will fMRIprep accept his structure & naming, and will *_defaced.nii.gz be recognized as the image to use? Or should I replace the original file with the defaced one to have only *.nii.gz, obtaining something like

dcm2bids + defacing + renaming & reorganizing:

anat
|_ sub-01_T1w.json
|_ sub-01_T1w.nii.gz

Hope I’m clear, thanks in advance to all of you folks!

Matthieu

Hi @MatthieuGG,

You can use a rec-defaced label, sub-x_rec-defaced_T1w.nii.gz. You should do this before fmriprep. Also you’ll want to either delete or filter out the original non-defaced images (e.g., with bids filter file).

Best,
Steven

1 Like

Hi @Steven , thank you very much for your reply! Quick and clear, as usual.

So fMRIprep will recognise a /anat/sub-x_rec-defaced_T1w.nii.gz automatically? Should the JSON be renamed also (/anat/sub-x_rec-defaced_T1w.json)?

Regarding the second point “Also you’ll want to either delete or filter out the original non-defaced images (e.g., with bids filter file).”, are you mentioning the .bidsignore file, with something like

  • sub-*/anat/*_T1w.nii.gz to ignore original T1
  • !sub-*/anat/*_rec-defaced_T1w.nii.gz to keep the defaced T1

All in, if I am never interested in reusing the original T1 but only the defaced, maybe keeping this structure is simpler?

anat
|_ sub-01_T1w.json
|_ sub-01_T1w.nii.gz

Best,
Matthieu

Hi @MatthieuGG

Yes, rename the json to include the rec-<> label. By filtering I was referring to a bids filter file. FAQ - Frequently Asked Questions — fmriprep version documentation

Best,
Steven

1 Like