[Insight-users] Inverting a Bsplines transform (or making a deformation field from a bsplines transform)

[brian avants]

One thing to keep in mind: there is no guarantee that a displacement field
is invertible.  If you want invertible (+ differentiable) maps, then  use
diffeomorphisms.  You should also check the accuracy of any inverse that
you estimate to see if it maps a point back to itself.  Bsplinesyn , in
Itk, resolves several of these issues by using bsplines to estimate
invertible maps and gives a good guarantee of the inverse's accuracy.


On Dec 10, 2013 3:07 PM, "Yago Diez" <yagodiezdonoso at gmail.com> wrote:
>
>
> Hi,
>
> In one application I am needing to deform points instead of images, so I
mainly have the opposites of all the deformations I need. So far, and
thanks to a lot of help received here, I managed to invert deformation
fields and several kinds of Rigid and Affine deformations, but so far I
have had no luck with
>
> typedef itk::BSplineDeformableTransform< double, 3, 3 >
DeformableTransformType;
>
>
> I have tried to use the GetInverseTransform() method (which worked for
rigid and affine transformations), I can compile it but I get a
segmentation fault whenever I try to use my inverted bsplines transform
(the output of the deformation is NULL). I assume this comes from the fact
that inverting a Bsplines transform is pretty difficult. My first question
is: Is there a "quick" way to invert a Bsplines transform?
>
> If the answer is no, I can also invert a deformation field if I can get
one from the bspline tranform, so the second question is: How can I
generate a deformation field from a Bsplines transform?
>
> Thank you all once more for all your help
> Yago
>
>
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