[Vv] Using vv/CLITK and elastix to compute target registration error

[S. Klein]

Hi Bilal,
I would do it like this:
1) ask your radiologists to click corresponding points in the ORIGINAL fixed and moving images. This gives you two files: fixedpoints.txt and movingpoints.txt.
2) Run elastix: elastix -f fixed -m moving -p parameterfile -out outdir
3) Run transformix to transform the FIXED points: transformix -def fixedpoints.txt -tp outdir/TransformParameters.0.txt -out outdir
4) now compare the transformed fixed points (which are stored in outdir/outputpoints.txt) to the original moving points.

Instead of using the custom elastix input and output point formats (see elastix manual, section on transformix), you could also use .vtk (in legacy asci vtk format).

Since the transformation is defined as a mapping from the fixed image domain to the moving image domain, you can only directly transform points from fixed to moving image.

Kind regards,
Stefan

On 20/03/2013 19:06, Bilal Tahir wrote:
Dear VV community,

We are planning to get a radiologist to define corresponding landmarks on fixed/moving inspiration/expiration CT lung images using VV. We use elastix for image registration. Once the registration is performed, is it possible to use VV/CLITK to compute the target registration error (TRE) between the fixed image landmarks and the registered moving image landmarks?

Furthermore, we would like the landmarks to be defined on the moving image prior to registration so that we can try different parameters to assess which gives the best TRE. Perhaps this is outside the scope of the mailbase, but has anyone done something similar using Elastix, where the coordinates of the expert landmarks are defined prior to registration using VV and new coordinates computed depending on the registration algorithm?

Best wishes,

Bilal Tahir,
James Morrison Researcher in Radiotherapy Imaging



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