[Insight-users] Mattes Information Metric

[Cory Quammen]

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