Dr. Gordon D. Waiter wrote:
> Having processed a data set twice, once with slice timing before and
> once with slice timing after realignment and noticed different results
> at the results stage, is it best to do slice timing before or after
> realignment in a descending acquisition. If there is a preferred order
> could someone explain why.
Slice-timing correction is ONLY valid if it is applied before the actual
data is changed between slices in any way. Registration, smoothing,
realignment all move data from one slice to another. If SPM actually
modifies the data in these steps, there is no way to keep track of
which data was in which slice initially. One of the SPM gurus will
have to verify that.
I can't see any good reason to do slice timing correction AFTER your
first step. Now, deciding whether the slice-timing correction is
meaningful and helpful is an entire other story...
rich
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