[Insight-users] Mattes Information Metric

[Karthik Krishnan]

As Cory says, use the identity transform. Also set the interpolator,
and the fixed image region and finally call Initialize or the metric
will throw an error.

something like:

   MetricType::Pointer metric = MetricType::New();
   metric->SetFixedImage( image1 );
   metric->SetMovingImage( image2 );

   typedef itk::IdentityTransform< double, Dimension >  TransformType;
   TransformType::Pointer transform = TransformType::New();
   metric->SetTransform( transform );

  typedef itk::LinearInterpolateImageFunction<
           ImageType, double > InterpolatorType;
  InterpolatorType::Pointer interpolator  = InterpolatorType::New();
  metric->SetInterpolator( interpolator );

 metric->SetFixedImageRegion( image1->GetBufferedRegion() );
 metric->Initialize();
 const double metricValue = metric->GetValue( transform->GetParameters()
);


 --
 karthik

On 10/29/10, Cory Quammen <cquammen at cs.unc.edu> wrote:
> Ken,
>
> When you call GetValue(), the argument you give it is passed to the
> transform, and the metric is computed over the transformed moving
> image. If you don't want a transformation on your un-moving image,
> simply set the transform for the metric to an IdentityTransform. Then
> simply pass GetValue() a variable of type
> IdentityTransform::ParametersType. You shouldn't need to initialize
> the ParametersType variable (it should be a zero-length vector).
>
> The code should look something like
>
> typedef MattesMutualInformationImageToImageMetric< TFixedImageType,
> TMovingImageType > MetricType;
>
> MetricType::Pointer metric = MetricType::New();
>
> typedef IdentityTransform<..., ...> IdentityTransformType;
> IdentityTransformType::Pointer transform = IdentityTransformType::New();
> metric->SetTransform(transform);
>
> MetricType::ParametersType params;
> double value = metric->GetValue(params);
>
> For what it's worth, there is (I think) an effort underway to separate
> the transforms from the metrics in ITK v4, which should let you call a
> parameter-less GetValue() method and avoid this complication
> altogether.
>
> Hope that helps,
> Cory
>
> On Thu, Oct 28, 2010 at 5:56 PM, Ken Urish <ken.urish at gmail.com> wrote:
>> Simple question but Im getting lost in the code
>>
>> Given two images I want to calculate the Mattes Mutual Information
>> Metric outside of the registration framework. This is easy during
>> registration as you just need "optimizer->GetValue()". However, I dont
>> want any transforms or optimizers involved and simply want to call the
>> metric value directly from:
>> itkMattesMutualInformationImageToImageMetric given two images. The
>> GetValue in MattessMutualInformationMetric macro needs a ParameterType
>> and Im stuck looking through the code what this is?
>>
>> Thanks
>> --Ken--
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>
>
>
> --
> Cory Quammen
> Computer Integrated Systems for Microscopy and Manipulation (CISMM)
> Department of Computer Science
> University of North Carolina at Chapel Hill
> http://www.cs.unc.edu/~cquammen
> _____________________________________
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> Visit other Kitware open-source projects at
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>
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> http://www.kitware.com/products/protraining.html
>
> Please keep messages on-topic and check the ITK FAQ at:
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