Hi Matt,
> What about the case of non-liner registration of a 2x2x2mm FA map to a
> 1x1x1mm T1 image of the same subject? In humans, we have done extensive
> testing with rigid body and affine images to try to get a good
> registration,
> however the registrations always seem to be a bit off at the genu of the
> corpus callosum (though this varies subject to subject) because of EPI
> distortion of the FA image in the orbital region. We are most interested
> in
> transforming ROIs from the structural image into native diffusion space to
> do FA measurements. We may end up correcting this distortion before
> registration, but if this is not possible, will we be able to use
> non-liner
> registration to get a correct registration?
FNIRT will not be well suited for that. It is partly because it has a "too
permissive" displacement model, permitting displacements in all three
directions rather than just in the phase-encode direction. And partly
because the information content in the two images (FA and T1) is so
different that FNIRT will struggle.
As soon as we have the FNIRT release out of the way (see below) we will
start working on distortions though.
> Is this something that FNIRT will be able to do? Also, I heard FNIRT
> would
> be out this autumn, but it's getting pretty cold where I live now. Any
> news
> on when it will be ready? :)
I blame global warming.
Slightly more seriously, we have an internal beta running and hope to
release our first internal "proper" version this week. And depending on
how that turns out we'll get the public release out asap.
We have to be a little careful because the new code also includes lots of
changes to existing code/libraries. So if we release too early it means
that not only will you have a broken FNIRT, but also lots of other broken
applications that you have come to love and rely on.
Jesper
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