[Insight-developers] affine MI registration - update

[Lydia Ng]

I was able to successfully test some dilation
by modifying the test image pattern.

The original test was a gaussian.
The new test image now has a gaussian in the middle
and some directional pattern in the background.

A coordinate transform is applied to the reference:
new_coord[i] = scale[i] * coord[i] + displacement[i]

The registration tries to estimate the inverse transform:
1/scale[i] and  -displacement[i]/scale[i]

I was able to recover up to 30% anisotropic scaling
(eg. scale = {0.7, 1.0, 1.0}) 
without making any modification to any registration code.

It starts to fail after 30%. I think this is reasonable - 
at 30% the images start the look significantly different.
And we are more likely to get trapped into a local
minimum.

I have tested the new pattern on the single resolution
version as well. It has the same performance -
I will check in the new test after the alpha lock down.

----
Lydia
  

> -----Original Message-----
> From: insight-developers-admin@public.kitware.com
> [mailto:insight-developers-admin@public.kitware.com]On Behalf Of Paul
> Hughett
> Sent: Thursday, July 26, 2001 10:41 AM
> To: lorensen@crd.ge.com
> Cc: Insight-developers@public.kitware.com
> Subject: Re: [Insight-developers] Dashboard
> 
> 
> 
> > Please fix your compile errors ASAP ...
> 
> This is not a compile error, but we might want to discuss it at the
> telcon.  It appears to me that affine registration--certainly mutual
> information but possibly other metrics--is broken; this wasn't caught
> before because the existing test programs test only pure translation.
> However, I've recently added a multiresolution test with anisotropic
> scaling that fails, and I can reproduce the failure on the single-
> resolution test by adding anisotropic scaling to it.
> 
> 
> Paul Hughett
> 
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