(1) Is there a way to get rid of epi distortion post-processing without
a field map
It would be nice if there was a method for doing this in SPM, but I'm
afraid there isn't.
(2) Am I stuck with spatially normalizing the epi images to the epi
template
using some masking of distorted regions?
No, but I would suggest you check out one of the emails I sent to the
list yesterday.
(2) Should I co-register structural and epi images to each other even
though
there is epi distortion in the OFC and spatially normalize:
(a) the structural to the structural template
or
(b) gray matter template to gray matter template
I would expect (b) to work much better than (a), but if you are using
SPM5, then the Segment button should do a reasonable job. You could
also try spatial normalization via segmentation of your EPI data. I
don't know how well this is likely to work though.
(3) Is there a way to mask out distorted areas in coregistration (if I
were to coregister structural and functional images) and then do #2))
I'm afraid not.
Best regards,
-John
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