Matching RTDose and CT coordinates

[Jothy]

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 look as in the attached figure.

Any hint

Thanks

Jothy