[Insight-users] Control of deformation field generation via landmarks?

[Ruben Schilling]

Hi Luis,

I tested actually all 5 Kernel transforms in ITK for this and I  
discovered my problem actually is, that there are no landmarks on the  
border of the image. Thus the splines fold however they like to fold  
outside of the small landmarks regions. The interpolation near my  
landmark positions looks very good though.
I guess what I need is a more or less isotropic copy process (maybe  
with slight averaging) of the few displacement vectors I have to  
cover all of the image foreground. Is there a filter to do an  
isotropic masked extrapolation of a sparse deformation field? If not  
I probably need to write one myself.

Regards,
Ruben



Am 11.07.2007 um 18:44 schrieb Luis Ibanez:

> Hi Ruben,
>
> The KernelTransform used inside this filter *already* blends
> the deformation from one landmark to the next.
>
> You may want to play with replacing the reciprocal elastic body
> kernel with the elastic body one.
>
> If you want to see profiles of the different kernels you can
> use the application:
>
>         InsightApplications/ThinPlateSplines
>
>
> You should also play with the value of Stiffness. This parameter
> allows to modify the behavior of the KernelTransform from
> interpolation to approximation. The default behavior is to
> interpolate.
>
>
> When applying deformations it is wise to add landmarks on the
> outside of the image, and to have their homologous landmarks
> to be superimposed, so that they generates a constrain of
> zero deformation around the image.
>
>
>
> Regards,
>
>
>     Luis