[Insight-users] jumps in MSE for multiresolution registration

[Ramón Casero Cañas]

Ramón Casero Cañas wrote:
> 
> Hi,
> 
> I have implemented a basic registration algorithm following the ITK 
> Guide examples, I get "jumps" in the MSE metric when changing scales, 
> and I'm not sure whether this behaviour is to be expected.

Hi,

I have further studied this problem with some modifications to
Examples/Registration/MultiResImageRegistration1.cxx, and the same 
"jumps" when changing scales are observed.

Basically, I have changed the metric of 
Examples/Registration/MultiResImageRegistration1.cxx to 
itkMeanSquaresImageToImageMetric.h, the data Dimension to 3, and reduced 
the step lengths accordingly to the image size. (See attached diff for 
details, and attached .cxx for full code).

I have attached also the graph with the Mean Square Error (MSE) over 
iterations of the optimizer. The dashed vertical lines show iteration 0 
at each new level in the multiresolution algorithm.

Why the jumps in the MSE? If we have 2 images at a coarse scale with a 
certain MSE, and then we just refine the scale, shouldn't the MSE be 
very similar (but for some interpolation differences)?

Best regards,

Ramon.

-- 
Ramón Casero Cañas, DPhil

Computational Biology, Computing Laboratory
University of Oxford
Wolfson Building, Parks Rd
Oxford OX1 3QD

tlf     +44 (0) 1865 610807
web     http://web.comlab.ox.ac.uk/people/Ramon.CaseroCanas
photos  http://www.flickr.com/photos/rcasero/
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