Fig. 5.

The field maps used here for unwarping, like any other field map, can be corrected as proposed through Eqs 11–13. A 1D profile as marked in inset is plotted here, for the corrected as well as the non-corrected field map. In this particular case, the manually-introduced shim was linear (Fig. 3b); for this reason and as seen here, the field error was simply proportional to the field itself, so that treated and untreated results appear here as straight lines intersecting at a zero field offset.