I am working on some data with field maps included. The data has fairly high distortion as we placed a TMS coil inside the MRI. The field maps can be quite useful in this case.

The SPM12 manual suggests a pipeline of 1) Realign: Estimate, 2) FieldMap to create VDM, 3) Apply VDM.

However I could alternately use Realign and Unwarp. As this second option incorporates the distortion correction into the realignment, correcting for both motion distortion and static distortion simultaneously, I assume it is the preferred approach. But it may be I have an incomplete understanding of how this first pipeline would work.

However as I have yet to work on fieldmaps, I thought I might solicit the advice of the community.

Colin