[elastix] Anisotropic Rigidity

Stefan Klein s.klein at erasmusmc.nl
Tue Jun 21 16:47:21 CEST 2011


Hi Kannan,
What do you exactly mean with "make the Z dimension" more rigid?

There are some options which might do what you want.

1) (perhaps superfluous explanation, but just to be sure:) In principle, 
elastix does already take into account the voxel spacing of your images.

2) If you want to avoid any deformations in the Z-dimension, you can add 
the following option to the parameter file:

(MovingImageDerivativeScales 1 1 0)

Then you will only have deformation in plane. But note: also no rigid 
deformation out of plane! You could do a registration in 2 stages, first 
a rigid without the movingimagederivative scales option, and then a 
bspline with the option.

3) The bspline grid spacing can be given a different value for each 
dimension. Intuitively, you may want to set the spacing higher in the 
z-dimension, to achieve a more rigid behaviour in that direction. But 
probably that's not what you want, since that will also result in a 
stronger coupling of the in-plane deformations between the consecutive 
planes. But maybe this is appropriate for your application.

4) You could experiment with using an anistropic ImagePyramidSchedule.

(ImagePyramidSchedule 8 8 1 4 4 1 2 2 1 1 1 1)

for example. This causes less blur in the Z-dimension in the initial 
resolutions, and thus may decrease the capture range in that direction 
(and thus hopefully avoiding large displacements in that direction).

Kind regards,
Stefan



On 17/06/2011 16:21, Kannan U V wrote:
> Hi,
> I am working with anisotrophic images with a ratio of 2:2:5. I want to
> make the Z dimension to be more rigid when finding the elastic
> transformation. Is it possible to set such a thing in elastix?
>
> Thanks,
> Kannan
> _______________________________________________
> elastix mailing list
> elastix at bigr.nl
> http://lists.bigr.nl/mailman/listinfo/elastix

-- 
Stefan Klein
+31 10 7043049
http://www.bigr.nl/people/StefanKlein



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