[Insight-users] Question about RayCastInterpolateImageFunction for 3D/2Dregistration

[Chong Zhang]

Generator Microsoft Word 11 (filtered medium) Hello everyone!

I just start using ITK, this library is too big for me to get all the information by myself. 

I am trying to perform image registration between a 3D volume and a 2D image. The most common way of doing this I found is to use itkRayCastInterpolateImageFunction to project the 3D volume into 2D image. I made a few modifications to the code InsightApplications/IntensityBased2D3DRegistration, but I still have some doubts. The main components of my code now are: 

Transform type: itkBSplineDeformableTransform 
Metric type: itkMeanSquaresImageToImageMetric
Interpolator type: itkRayCastInterpolateImageFunction
Optimizer type: itkOnePlusOneEvolutionaryOptimizer
Registration type: itkImageRegistrationMethod (treat the 2D image as a 3D data with Z dimension to be 1)

I don' t have a clear idea of how itkRayCastInterpolateImageFunction works. Does anyone know where I can find an example for this class? I tried " itkRayCastInterpolateImageFunctionTest"  from Testing/Code/Algorithms, the " Integral"  value is always 0 for any " query"  point. It is because the variable " m_ValidRay"  is always " false" . Does anyone know if this is a problem of the test code, or the RayCastInterpolate class itself? Any suggestion is highly appreciated. Thanks!

Best,
Chong
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