[Insight-users] DTI data.. can't read

[Torsten Rohlfing]

Hi Gordon --

I have a question regarding that DTI data you are making available 
through the server at Utah.

It seems that the NRRD reader currently in ITK cannot actually read this 
file. More precisely, it seems that the spatial dimensions are not 
correctly separated from the matrix element dimension. Here's a printout 
of the resulting image object that may clarify the issue:

Image (0x910ca40)
  RTTI typeinfo:   itk::Image<itk::DiffusionTensor3D<float>, 3u>
  Reference Count: 2
  Modified Time: 121
  Debug: Off
  Observers:
    none
  Source: (0x910c948)
  Source output index: 0
  Release Data: Off
  Data Released: False
  Global Release Data: Off
  PipelineMTime: 10
  UpdateMTime: 122
  LargestPossibleRegion:
    Dimension: 3
    Index: [0, 0, 0]
    Size: [7, 148, 190]
  BufferedRegion:
    Dimension: 3
    Index: [0, 0, 0]
    Size: [7, 148, 190]
  RequestedRegion:
    Dimension: 3
    Index: [0, 0, 0]
    Size: [7, 148, 190]
  Spacing: [0, 1, 1]
  Origin: [0, 0, 0]
  Direction:
1 0 0
0 1 0
0 0 1

  PixelContainer:
    ImportImageContainer (0x910cb58)
      RTTI typeinfo:   itk::ImportImageContainer<unsigned long, 
itk::DiffusionTensor3D<float> >
      Reference Count: 1
      Modified Time: 119
      Debug: Off
      Observers:
        none
      Pointer: 0x910cb74
      Container manages memory: true
      Size: 196840
      Capacity: 196840

The code for reading that I use is as follows:

  typedef float TensorDataType;
  typedef itk::DiffusionTensor3D<TensorDataType> TensorPixelType;
  typedef itk::Image<TensorPixelType,3> TensorImageType;

  typedef itk::ImageFileReader<TensorImageType> ImageReaderType;
  ImageReaderType::Pointer reader = ImageReaderType::New();
  reader->SetFileName( argv[1] );
  reader->Update();

Interestingly, when I create a tensor image within ITK and write it to a 
NRRD0004 file, I can read everything fine, so maybe all that's needed to 
fix the issue practically would be if you could come up with a header 
for the file that can be read correctly by what's in ITK?

Thanks for your help!
  Torsten

-- 
Torsten Rohlfing, PhD          SRI International, Neuroscience Program
 Research Scientist             333 Ravenswood Ave, Menlo Park, CA 94025
  Phone: ++1 (650) 859-3379      Fax: ++1 (650) 859-2743
   torsten at synapse.sri.com        http://www.stanford.edu/~rohlfing/

     "Though this be madness, yet there is a method in't"

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