[Insight-users] MattesMIMetric with different optimizers

[Xavier Kite]

Hi, 

I'm reducing the radius of the 1+1Optimizer but nothing changes. I have the same exception as before.
For example, the initial parameters for the optimizer are :
Initial Radius    0.1
Growth Fractor    1.01
Shrink Fractor    0.997516
Epsilon   0.0001 

With the RegularStepGradientOptimizer, the initial parameter (steplength) was 0.3.

So I really don't understand why I've always this exception.

It could come from an other point? 
I don't see on wich other parameter I could play.

     Xavier

-----------------------

Hi Xavier,

You are probably using a radius that is too large
for the OnePlusOneOptimizer.

The exception that you are getting, is thrown when
the transform is so far off that the fixed image and
the mapped moving image don't have any overlap.

This means that you are moving too far too fast in
the parametric space of the transform.

Simply reduce the size of the InitialRadius in the
Optimizer. You may also have to tune the GrowthFactor,
to make sure that the radius doesn't grow too much
during the iterations.



    Regards,


       Luis



-----------------------
Xavier Kite wrote:

> Hi,
> 
> I'm working on registration of 3D medical images.
> I'm using the AffineTransform with the metric MI Mattes.
> And I'm trying some different optimizers... but I have got a problem 
> using the OnePlusOneOptimizer.
> When I use the RegularStepGradientDescentOptimizer,  all is working 
> without exception. But when I replace this optimizer by the OnePlusOne 
> I've the exception about the samples :
> 
> itk::ExceptionObject (0x8363f80)
> Location: "Unknown"
> File: 
> /home/xwantier/ITK/InsightToolkit-2.0.1/Code/Algorithms/itkMattesMutualInformationImageToImageMetric.txx
> Line: 623
> Description: itk::ERROR: 
> MattesMutualInformationImageToImageMetric(0x8360ba8): Too many samples 
> map outside moving image buffer: 0 / 10000
> 
> Could you say me why and what I should do.
> My implementation is exactely the same as the example ImageRegistration11.
> 
> Thanks a lot.
> 
>     Xavier

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