[Insight-users] Registration convergence

[Godley, Andrew]

Hello,

I am using Demons to register CT scans.  I print out filter->GetMetric()
and filter->GetRMSChange() through the observer.  I assumed that it is
the Metric that should be minimised, but I read that it is the RMS.

Is the RMS what is being minimised?

Does the metric represent something like the summed intensity difference
between pixels in the image?  Why wouldn't I want this minimised?

I run registrations where the Metric reaches a minimum and then starts
to rise, whilst the RMS continues to decline. 

I have been very happy with ITK and have been using it for 3 months.  I
had been able to avoid asking questions until now, as I can't get my
current test images, one with a much larger rectum, registered.

Thank you,
Andrew