[Insight-users] [Gdcm2] Matching CT and RT dose coordinates

[Mark Roden]

Hi Jothy,

What are the direction cosines?

There is a problem where VTK reinterprets the direction cosines to
change the directions of images produced by the dicom reader.

DICOM specifies that the image patient position is always the upper
left pixel (if you look at the image as a 2D image on a plane like a
monitor).  VTK will take the direction cosine and potentially flip the
image along those cosines.

Mark

On Wed, Feb 23, 2011 at 9:38 AM, Jothy <jothybasu at gmail.com> wrote:
> Hi all,
>
> I am trying to overlay an dose shade on a CT slice.I am using
> vtkDICOMImageReader to read the CT and vtkGDCMImageReader to display the
> dose shade.But I am having problem with the coordinates.How to relate the
> coordinates? For e.g: I  get ImagePositionPatient of CT image for central
> slice as [-275,-524,-128.25] and ImagePositionPatient for dose as
> [-228.65,-419.25,-122.5] adn their spacings are [1.074,1.074,3] and
> [2.52.5.2.5] respectively for CT and Rt dose.
>
> The image looks as in the attached figure.
>
> Any hint
>
> Thanks
>
> Jothy
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