[Insight-users] Registration of zero contours in two level set images

[Haiyong Xu]

Hi List,

I have two level set images with zero contour representing an object
boundary. These two images have different origin/spacing/size. The
zero contours in both images are similar with certain degree of
deformation and transformation. I want to register these two zero
contours such that, for any point on image_A's zero contour, the
corresponding point on image_B's zero contour can be calculated.

After reading the Registration chapter in itkSoftwareGuild.pdf, I
think there are two approaches. The first approach is to use the
Deformable Registration or Demons Deformable Registration to register
two images. The deformation fields generated from either registration
method can be used to compute the corresponding points. The second
approach is to use Point Set Registration, e.g., ICP algorithm. In
this approach, points on zero contours of both image_A and image_B are
extracted, then these two point sets are registered using ICP
algorithm with deformable transformation.

My questions are:
1. For the first approach (deformable registration), since I am only
interested in registration of two zero contours rather than two
images, could those two methods be configured to only focus on zero
contour pixels rather than the whole image pixels? Probably
itk::ImageMaskSpatialObject will help, but I'm not sure how to do it.

2. For the second approach (ICP algorithm), does it work for two point
sets with different number of points and the correspondence in those
two point sets is not known?

3. Is there any other methods to complete such registration task?

Thanks for your time.

Regards,
Haiyong Xu