[ITK] [ITK-users] 3D/2D registration with itkRayCastInterpolateImageFunction

[Siavash Khallaghi]

Hi Charles,

For the record, I do not think that you have a software bug per say. I think
your problem is a bit more fundamental, i.e. the combination of
optimizer/metric might not have sufficient capture range to guide the
registration to the true solution.

In order to investigate this, I would suggest trying the following:

1. If you generate your projection from identity (which I assume is the true
solution), and start your registration from identity, would the registration
converge to identity as well? This tells you how stable your metric is.

2. At this point, I would definitely start plotting the metric value against
transformation parameters. See /Section 3.10.1 Mean Squares Metric:
Exploring a Metric/ of the  Software Guide
<http://se.csie.dyu.edu.tw/canseco/PDF/InsightSoftwareGuide-Book2-4.6.0.pdf> 
. Since your registration does not converge to the correct solution for
rotations, I suspect that it is getting stuck in a local minima for these
parameters.

Siavash



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