Hi Cherif,
> Just for education purposes, when would you use 12 dof vs.
> nonlinear (IRTK, FNIRT...) registration?
> I'd be tempted to say that nonlinear reg is best when registering
> across both subjects and acquisition types, or when there are
> inconsistencies between subjects ( e.g. tracts that don't fall in
> the same spot if you "only" use 12dof)... Is that too simplified?
I think it is fair to say that the "true" mapping from one subject A
to another subject B will always be non-linear (if we assume that
there actually is a "true" mapping).
Then the question of appropriate becomes a question of "do we have
good enough information to estimate the non-linear mapping from A to
B?". When we have a high quality scan of A and a high quality scan of
B with the same acquisition type the answer to that question is often
yes, and a non-linear registration will be the better choice.
If on the other hand we have a e.g. high resolution T1 structural
scan of subject A and a low resolution EPI scan of subject B the
answer might be "No, the information we have does not allow us to
estimate non-linear mapping from A to B", and an affine mapping will
be the better choice.
Hope that helps.
Jesper
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