[ITK] Calculate Normalized Mutual Information between images outside registration scope

[Eriksson, Mikael]

Hello,

I'm having trouble trying to calculate the normalized mutual information of two images. I would like to do this without performing any registration, just calculate the value. This is the relevant part of my implementation:


                typedef itk::NormalizedMutualInformationHistogramImageToImageMetric<ImageType, ImageType >    NormalizedMetricType;

NormalizedMetricType::Pointer metric = NormalizedMetricType::New();

       unsigned int numberOfHistogramBins = 32;
       NormalizedMetricType::HistogramType::SizeType histogramSize;
       histogramSize.SetSize(2);
       histogramSize[0] = numberOfHistogramBins;
       histogramSize[1] = numberOfHistogramBins;
       metric->SetHistogramSize( histogramSize );

       metric->SetTransform(transform);

       metric->SetFixedImage(fixedImage);
       metric->SetMovingImage(movingImage);
       metric->SetFixedImageRegion(fixedImage->GetLargestPossibleRegion());

       metric->SetInterpolator(interpolator);

       TranslationTransformType::ParametersType parameters;
       parameters.SetSize(2);
       parameters.Fill(0);

       MetricType::MeasureType value = metric->GetValue(parameters);
       std::cout << "Value: " << value << std::endl;

With this code, the program crashes at the penultimate line, when I call GetValue. I have tried different workarounds (like connecting to a registration object and calling GetValue), but nothing I've tried has resulted in any success. I looked at the MutualInformationImageToImage-example (http://www.itk.org/Wiki/ITK/Examples/Broken/ImageProcessing/MutualInformationImageToImageFilter), and tried it out myself and it worked, my problems arise when I use the Normalized Mutual information.

Can somebody shed some light on these issues?

Cheers,
Mikael

.......................................................................................................
Mikael Eriksson
R&D Physicist Trainee
Philips Medical Systems MR Finland, Feasibility studies
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