As above image, I used B0 map to correct B0 inhomogeneities. I heared it can help me to avoid the signal loss from PFC.
So, how can I get this information from fmriprep report ?
Red means signal enhancement and blue means signal decrease？
As this understand, signal from PFC seems be enhancemented after correction, but signal from temperal lobe(blue areas in second row) seems drop after correction.
There are two susceptibility artifacts to consider: signal loss (drop-out) and spatial mismapping (spread / pile-up). There’s nothing that can be done about signal loss once the data are acquired; attenuated signals are just gone. SDC aims to counteract mismapping and restore the anatomical correspondence of BOLD data.
To counteract the mismapping, you create a “voxel displacement map” (VDM) that estimates where the signal from a voxel is expected to appear in a distorted image (a weighted sum of nearby voxels). What you’re seeing there is the estimated fieldmap in Hz, which can be used to calculate a VDM based on some parameters of the BOLD acquisition. For more details, you can see Methods and implementation - sdcflows 2.0.10 documentation.
Roughly, the red will correspond to signals that need to be shifted in the phase-encoding direction, and blue in the opposite direction. (It’s possible I have this backwards; I haven’t checked since nothing I’ve said is really contingent on this.)