Hi @Guoyuan , actually the PEPOLAR method with SpinEcho EPI images with AP and PA should work best for susceptibility correction. But it is true that if the distorsion are too big, especially in the compressed area, SDC will be difficult. You can mitigate the distortion on the acquisition side by minimizing the echo spacing, reducing the FOV in the phase encoding direction and using parallel imaging for instance.
I don’t know how this would work with 7T data, but we recently tested this tool which is very good for SDC if you don’t have any fieldmap images to correct your bold images:
We discussed its implementation with fmriprep processing here: