[Insight-users] mutual information registration

[Dill, John]

I have made some progress on my registrations between a portfilm image and a
drr.  Since the search algorithms weren't working well and didn't know how
to adjust them, I instead sampled the transformation space (which is always
small in all test cases available) and for each point in the [x tx, y tx,
rotation] for a small range [-10 10] pixels for translation and [-5 5]
degrees for rotation, and average the metric over 500 iterations.  From
this, I selected the maximum average value of the metric, and I was able to
get registrations within acceptable limits for the large majority of my test
cases.

Of course using this method, the calculation times are too long (with my
current algorithm iterations evaluating about 5000 different registration
parameter vectors with 500 avg of mi metric each, amount to approx 3 hours,
but I should be able reduce that time by using a multi-res sampling
approach, maybe reducing the avg iterations), and am trying to go back to
the search method.  Can someone list off what I can vary with respect to
mutual information 2D rigid registration (variance, scale parameters,
iterations, others)?  Right now I seem to be having problems with rotation
going haywire and don't know how to make its value less volatile than
translation.  Right now I am using CenteredRigid2DTransform.  Is there an
example program available which allows you to vary all the parameters of a
CenteredRigid2DTransform for testing different parameters?

Thanks for any advice.
John