[Insight-users] Initialization of BSpline transformation with deformation vector field

[Jochen Cammin]

I now realize that I probably need to use the
BSplineInterpolateImageFunction for this purpose (instead of
BSplineDecompositionImageFilter).

However, I'm having trouble putting a pipeline together since I can't
seem to find a way to access the BSpline coefficients from the
BSplineInterpolateImageFunction.

How can I get the coefficients?

Thanks,
Jochen


Jochen Cammin wrote:
> I want to register two 3D images using the BSplineDeformableTransform. I
> have an estimate for the transformation which I want to use to
> initialize the BSpline transformation. As far as I can see from the
> documentation, the transform can only be initialized with BSpline
> coefficients.
> 
> However, my initial estimate is in the form of a deformation vector
> field. Therefore, I need to transform the initial deformation vector
> field into BSpline coefficients.
> 
> I thought that I could use the BSplineDecompositionImageFilter for this
> purpose. Is the following way a good approach?
> 
>       1. create three 3D images from the initial deformation vector field
>          (one for each component of the vectors).
> 
>       2. use the BSplineDecompositionImageFilter on each of the three
>          images to calculate the BSpline coefficients for each dimension
> 
>       3. initialize the transformation with these parameter images
> 
> 
> Is this approach correct? When I looked at two examples that use the
> BSplineDecompositionImageFilter (DeformableRegistration6.cxx and
> DeformableRegistration15.cxx) it looks like
> BSplineDecompositionImageFilter works directly on the coefficient images
> of the coarser transformation, never on the actual deformation vector
> field. That's why I'm not sure if my approach will give the correct results.
> 
> Thanks for any feedback,
> Jochen
> 
> 
> 
>