[Insight-users] Registration: X translation is always wrong

[Luis Ibanez]

Hi itkvtk123

Can you post to the list (or to a public web site)
a screenshot of the images that you are trying
to register ?

It is likely that the behavior of the Optimizer can
be better understood by looking at the internal
content of the image.


      Thanks


              Luis


--------------------------------------------------------
On Thu, Sep 10, 2009 at 5:20 AM,  <itkvtk123 at gmx.net> wrote:
> I'm trying to register two 256px images with 1mm spacing and I expect +- 0.175 radian in rotation and +- 10 mm in translation.
> So I set the scales to
>
> rotationScale = 1.0
> translationScale = 0.00175
>
> I set the initial search radius of OnePlusOne optimizer to 0.175, so we should be searching for values in a rotation interval of +- 0.175 radian and a translation interval of +-100 mm.
>
> In my test case the real offset is 25mm in X, 25mm in Y and 0.087 radian in rotation.
>
>
> The OnePlusOneOptimizer (initial search radius 0.175, epsilon 1.0) results in:
>
> -0.579999 for X (should be -25.0)
> -31.3951 for Y (should be -25.0)
> 0.0869 for Rotation (should be 0.087)
>
> So Rotation is right, Y is quite right and X is totally wrong.
>
>
>
> When I do the same scenario with Gradient Descent (Max step length = 0.175 (is 100mm) Min step length = 0.00175 (is 1mm)) I get the following results:
>
> -10.8652 for X (should be -25.0)
> -26.6043 for Y (should be -25.0)
> 0.0872 for Rotation (should be 0.087)
>
> Again, Y is quite right, Rotation is correct and X is wrong.
>
>
> In the Optimizer History you can see that values for Y rise always faster than values for X (regardless which optimizer).
> But why? They have the same scale! Pixel spacing is also the same for X and Y in the image.
>
> Thank you.
> --
> GRATIS für alle GMX-Mitglieder: Die maxdome Movie-FLAT!
> Jetzt freischalten unter http://portal.gmx.net/de/go/maxdome01
> _____________________________________
> Powered by www.kitware.com
>
> Visit other Kitware open-source projects at
> http://www.kitware.com/opensource/opensource.html
>
> Please keep messages on-topic and check the ITK FAQ at: http://www.itk.org/Wiki/ITK_FAQ
>
> Follow this link to subscribe/unsubscribe:
> http://www.itk.org/mailman/listinfo/insight-users
>