SPM Coregistration generates a large file in nipype

Hello guys,

When I try to apply SPM coregisteration (native fMRI to the native T1) in nipype, (jobtype = ‘estwrite’) the output coregistered file has a very large volume. For example, my functional file originally is ~50 MB. But after coregisteration it becomes ~4GB. Anyone knows why this happens? How can I solve this problem? (When I perform coregistration separately inside the SPM12, there is no such a problem)

Ahoi hoi @s.mortaheb,

thank you very much for your post.
Hm, this indeed sounds strange. Could you maybe provide us
with more information like resolution of your images and nipype code snippets?
It could be related to resampling but I’m not sure as your T1w would need to have very small voxel dimensions for that to be the case.

Cheers, Peer

Hello @PeerHerholz

Actually it was the problem of resampling. Functional data have a dimension of 64 * 64 * 32 while structural data have a dimension of 208 * 256 * 192 which is almost 80 times more voxels. This makes sense because 50 MB * 80 ~ 4 GB. I removed resampling at this stage because it is not necessary and then I will resample the data when I normalize them to the MNI space.