[Insight-developers] Problems with affine MI registration

[Paul Hughett]

I'm gearing up to try the ITK image registration algorithms on real
data.  I took the test program for affine/mutual information/gradient
descent registration from the repository and modified it to try some
variations in the actual transformation and optimization parameters.
Discovered that the algorithm seems to work reasonably well for
translations, as long as they aren't too large, but I can't get it to
work at all for either isotropic or anisotropic scaling; an expansion
of even a few percent causes the algorithm to fail.  Neither
increasing the learning rate nor increasing the number of samples up
to 500 seems to help.

Any suggestions?

Paul Hughett