Difference between revisions of "NAMIC Wiki:DTI:ITK"

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== ITK Data Structure for DT Images ==
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=== DTITubeSpatialObject and DTITubeSpatialObjectPoint ===
  
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Since the itk::Image class is templated over pixel type and dimension, specifying a DT image is simply a matter of instantiating the image class over the appropriate tensor pixel type. However, there may be factors that we need to consider to make such an image practical.
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See [[NAMIC_Wiki:DTI:Fiber_format|Fiber format]] for a discussion of the DTITubeSpatialObject as a file format.
  
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If we are focusing on 3D symmetric tensors, then each pixel at a minimum needs to store 6 floating point values to describe the tensor. To avoid calculating eigenvalues and eigenvectors multiple times for a given tensor during the course of an algorithm or pipeline of algorithms, there is a temptation to cache the eigenvalue and eigenvectors associated with a tensor. Processing DTI could quickly exhaust physical memory.
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An itk::DTITubeSpatialObjectPoint represents DTI information at a physical coordinate. DTITubeSpatialObjectPoints are used to build itk::DTITubeSpatialObjects which can be connected into a tube network.
  
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Some ideas to consider:
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DTITubeSpatialObjectPoint stores the following information:
  
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* Does every pixel in an DT image need to be stored? Are there pixels in the DT image that are outside the anatomical region of interest?
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* Tensor.
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** If so, the DT pixel should have minimum storage, perhaps just an internal pointer to the tensor data. That pointer could be null if the tensor for that pixel is not needed.
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** Assumed to be a symmetric tensor of dimension 3.
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* Should the DT pixel be able to cache structure information (eigenvalues and eigenvectors)?
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** 6 floating point values.
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** The DT pixel could cache this information is the algorithm requested.
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* Eigenvalues
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** Tensor::ComputeEigenSystem(cache = true)
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** 3 floating point values
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** Could have methods to destroy cached data
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* Eigenvectors
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** Or should caching this type of information be left to the algorithm developer. An algorithm could separate data structures for caching eigenvalues and eigenvectors.
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** 3 vectors each with 3 floating point values
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* Should the DT pixel type store FA and ADC?
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* FA
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** float
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* GA
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** float
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* ADC
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** float
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* MRI.
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** 5 floating point values.
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* Interpolation flag
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** int
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* Number of dimensions
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** unsigned short

Revision as of 13:31, 18 December 2006

Home < NAMIC Wiki:DTI:ITK

DTITubeSpatialObject and DTITubeSpatialObjectPoint

See Fiber format for a discussion of the DTITubeSpatialObject as a file format.

An itk::DTITubeSpatialObjectPoint represents DTI information at a physical coordinate. DTITubeSpatialObjectPoints are used to build itk::DTITubeSpatialObjects which can be connected into a tube network.

DTITubeSpatialObjectPoint stores the following information:

  • Tensor.
    • Assumed to be a symmetric tensor of dimension 3.
    • 6 floating point values.
  • Eigenvalues
    • 3 floating point values
  • Eigenvectors
    • 3 vectors each with 3 floating point values
  • FA
    • float
  • GA
    • float
  • ADC
    • float
  • MRI.
    • 5 floating point values.
  • Interpolation flag
    • int
  • Number of dimensions
    • unsigned short
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