[Insight-developers] DCMTK ImageIO Questions

[Williams, Norman K]

I started testing the itk DCMTKImageIO for reading DICOM images this week,
by using it in DWIConvert, which is my re-write of the Slicer
DicomToNrrdConverter program. It works fine, and passes all the DWIConvert
regression tests except for one.

That one test starts from a DICOM data set from MIDAS -- the GeSignaHDx
data set here http://midas.kitware.com/item/view/542

The issue is scaling of the Pixel data. Due to some obscure decisions
about scaling data, GDCM produces pixels in the range 0..23819, DCMTK
produces voxels in the range -32768..-8949 as reported by Slicer4.  By
stepping through the DCMTK library, it looks as though it applies this
data shift on the basis of the image modality.

The question is this: does GDCM does it right -- not shifting pixel
values, or does DCMTZK do it right?

Question #2:

There was some discussion on the mailing list some months back about
exposing the DICOM tags by copying them out to the MetaDataDictionary when
reading a DICOM series.  Right now nothing is done -- only the Image data,
directions, origin, and spacing are recovered from the DICOM series on
reading.

What should happen?  There was some discussion of exposing an interface
for extracting Dicom metadata in a consistent manner across both readers,
but I don't remember anyone deciding anything or beginning a design.
--
Kent Williams norman-k-williams at uiowa.edu






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