Processed fMRI data is not in the specified MNI152NLin6Asym space

Hi fmriprep experts,

I recently used the fmriprep to process the resting-state fMRI data. Here is the code:

singularity run -B “${myproject}”:"${myproject}" --cleanenv “${myproject}/fmriprep-1.5.9.simg” “${myproject}/Data/${SUBJECT}/bids_dir” “${myproject}/DataProcessed” --nthreads 32 --omp-nthreads 32 --mem_mb 20000 participant --participant-label “${SUBJECT}” --fs-license-file “${myproject}/license.txt” --output-spaces MNI152NLin6Asym -w /tmp/

The output space is specified as MNI152NLin6Asym and I expect the preprocessed (registered) BOLD data to be in the MNI space of dimension 91 x 109 x 91 (voxel size: 2 x 2 x 2 mm). The voxel size of my original BOLD data is 2mm isotropic.

However, the final BOLD data is in a dimension of 92 x 110 x 92 (voxel size: 2 x 2 x 2 mm), as shown in the attached screenshot. I’m very confused by the registered space, which is certainly neither the MNI152NLin6Asym nor the default MNI152NLin2009cAsym (97 x 115 x 97, voxel size: 2 x 2 x 2 mm).

How should I fix it?

Any ideas would be much appreciated.