05 - fmriprep

Step by step description of how to run fmriprep

1 Before running fmriprep

Before you start fmriprep, you have to make sure, that you:

1. have nifti files in BIDS format

2. defaced your anatomical scans

3. Optional: removed the noise scans from your functional data

4. Optional: adapted the “IntendedFor” section in the fmap’s .json file (if you want to use fmriprep 24.0.0 or newer)

2 Starting fmriprep

To start fmriprep, click on the bird symbol at the bottom left on neurodesk, hover neurodesk, then All applications and navigate to fmriprep. Select the version of fmriprep that you want to use

After selecting your version, a new bash window opens and fmriprep loads. This can take a few moments, be patient! When everything is ready, the bottom line should state fmriprep-"Version" (with “Version” being whatever version you selected, for example fmriprep-24.1.1)

3 Setting up necessary directories and defining “SUBJECTS_DIR”

First, you need to create some new directories that are necessary for fmriprep to run properly. For this, enter the following command (adapt the path(s) if necessary)

mkdir -p /home/jovyan/website/bids/derivatives/fmriprep/sourcedata/freesurfer/

By confirming your command with Enter, you´ll find the new directory structure within you derivatives directory

Then, we need to specify where fmriprep should store the resulting files with this command (again, adapt the path(s) if necessary):

SUBJECTS_DIR=/home/jovyan/website/bids/derivatives/fmriprep/sourcedata/freesurfer/

Set SUBJECTS_DIR

Hint: you can copy/paste both commands from above and execute them by pressing enter simultaneously, it doesn´t matter

4 fmriprep command

With the setup done, you can now run the command:

fmriprep /home/jovyan/website/bids /home/jovyan/website/bids/derivatives/fmriprep participant --bold2t1w-init header --force-bbr -w /home/jovyan/website/fmriprep_tmp --output-spaces T1w fsaverage fsnative --participant-label sub-999 --nprocs 8 --mem 10000 --skip_bids_validation --stop-on-first-crash -v --fs-license-file /home/jovyan/website/freesurferlicense/license.txt

Important: adapt the flag --participant-label sub-999 accordingly, so that you state the subject you want to preprocess

Hint: same as before, you could run this command with the two commands above for the setup as well. The only important thing is the order: first the command for making the directories, then defining SUBJECTS_DIRand finally the fmriprep command.

5 Waiting

When fmriprep started, now it´s probably time to get a coffee and do something else. This process will take quite some time (hours), you don´t have to stare at the output the whole time. You can also close the Tab where you opened neurodesk! Even if you close it, the program continues its work!

6 Troubleshooting

\(\to\) If there are any problems, please refer to the dedicated troubleshooting page

1. I ran fMRIprep but no distortion correction happened

   fMRIprep might be using an outdated BIDS specification. Here this is related to the fmap json file. See Information about BIDS uri, or the corresponding wiki entry.

   • If your fmap .json file is using the BIDS uri specification in the IntendedFor field and you are using an older fMRIprep version then this will need to be changed to the older path specification e.g.

   BIDS uri spec for fmriprep 24.0.0 or newer:

   "IntendedFor": [
       "bids::sub-1181001/ses-1/func/sub-1181001_ses-1_task-movie_run-1_bold.nii.gz",
       "bids::sub-1181001/ses-1/func/sub-1181001_ses-1_task-movie_run-2_bold.nii.gz", 
       etc
       ]

   Older fmap spec for fmriprep older than 24.0.0:

   "IntendedFor": [
       "ses-1/func/sub-1181001_ses-1_task-movie_run-1_bold.nii.gz",
       "ses-1/func/sub-1181001_ses-1_task-movie_run-2_bold.nii.gz",
       etc
       ]

 

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2. I ran fMRIprep and the distortion correction of the data is too extreme

An example of poor distortion correction

This is an issue with certain issues of fMRIprep. Using fMRIprep version 20.2.7 may be needed to avoid the extreme distortion correction (newer versions of fMRIprep haven’t been tested)

 

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3. If using already run FreeSurfer recon-all output and have specified an expert-opts file then fMRIprep shows multiple errors

   • In the directory that has the prerun recon-all there is a folder scripts that saves the expert-opts file. Removing this file allows fMRIprep to run

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4. If fmriprep fails silently (i.e. gives no error) on coregistering the functional to the structural scan, the solution is (if your structural and functional scans are from the same session) to add the following flag:

   --bold2t1w-init header

7 The next steps

Congratulations, you successfully preprocessed your data and you are one step closer to analyzing your data!

To continue in your journey to your Analysis, please return to the Overview-Page to check what to do next.

Alternatively, here is a list of potential next steps to continue with

1.Retinotopic Mapping

2. first-level GLM

3. second-level GLM