[vtkusers] Matching CT and RT dose coordinates

[Scott Johnson]

If the FrameOfReferenceUIDs of the CT and the RT dose are the same, they
both exist in the same coordinate system, if they don't, you will have
to register the dose to the CT somehow.

 

Because the resolution of the dose will generally be different than the
CT a reasonable strategy is to loop through your CT voxels and use the
position at the center of that voxel to sample into the RT Dose grid.
When you sample into the RT Dose you may need to interpolate the actual
dose value.  That dose value determines your shading.

 

The other issue to be aware of is that the dose grid may not completely
cover the CT image data.  This is probably why the origins are different
for your data.

 

                                -- Scott

 

From: vtkusers-bounces at vtk.org [mailto:vtkusers-bounces at vtk.org] On
Behalf Of Jothy
Sent: Wednesday, February 23, 2011 11:38 AM
To: gdcm-developers; VTK Mailing List; itk;
python-medphys at googlegroups.com
Subject: [vtkusers] Matching CT and RT dose coordinates

 

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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