[Insight-users] Fitting BSplines to Deformation Fields?

[Jochen Cammin]

Hi Constantine,

You can use the BSplineDecompositionImageFilter filter for this: from
your 3D VDF create three separate 3D scalar images, one for each vector
component. Then run the b-spline decomposition filter on each of the
three scalar images to get the coefficients. You can then use the
obtained coefficient images directly to set the parameters for a
b-spline transformation, or you can extract the coefficients and fill
them in an array in order to initialize the b-spline transformation.
Examples are given in Examples/Registration/DeformableRegistration6.cxx
and in Examples/Registration/DeformableRegistration15.cxx.

The class definition is available at
http://www.itk.org/Doxygen316/html/classitk_1_1BSplineDecompositionImageFilter.html

I hope this helps,
Jochen

Constantine Zakkaroff wrote:
> Hello All.
> 
> I'm wondering if there's an easy way of fitting a BSpline (calculating 
> the node coefficients) to a dense vector deformation field? For example, 
> I have a 3D VDF and I want to represent the transformation it as a 3D 
> BSpline?
> 
> Or even better, say I have a 4D VDF (3D + time) and I want to represent 
> the transformation between time=0 and time=N as a 3D BSpline?
> 
> Thanks,
> Constantine
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