Registration based distortion correction for dMRI


I’ve been reading about the registration-based distortion correction methods (T1w-dMRI) and there is something that is not still clear to me:

You should rigid register your T1w to the B0 and the non rigid register the B0 to the rigidly registered T1. However some works restrict the non rigid registration to the phase encoding axis, and others don’t.

Any clue why this happens? Any advice on what’s the best way to do this. Due to the nature of my data I can not use the SyN-SDC implemented in QSIprep, so I’m looking for alternatives. Thanks in advance.

Best regards,