Dear Anna,

 vmtk doesn't natively take into account image orientation yet. It has been in 
the wishlist for some time now, but it would require quite some work, 
hopefully I'll be able to get it done if there's enough interest in it.

For the time being, you can recover the original orientation by transforming 
the segmented surfaces to their respective patient's coordinate space:

vmtkimagereader -ifile 0001_0001.dcm --pipe vmtksurfacetransformtoras -ifile 
segmented_surface.vtp -ofile transformed_segmented_surface.vtp

Note that you have to start from your original dicom series in the 
vmtkimagereader, since the transform matrix is taken from there.

You should do this for both surfaces, and they should align at the end *if* the 
two patient reference frames where the same (which doesn't depend
on vmtk, of course).

If they aren't (you can load the images up in, say, Osirix, and check if the 
two series overlap), then you'll have to perform image registration first.
To this end you could use 3DSlicer, it incorporates quite a few registration 
algorithms.

Hope this helps.


Luca




On Jul 12, 2012, at 9:34 PM, Hoppe, Anna L wrote:

> Hi VMTK users,
> 
> I have two volumetric image sets taken at the same time point with slightly 
> different patient locations (according to the dicom header files). One is a 
> bone scan and the other is a contrast-enhanced vessel scan. When loading 
> these two data sets using vmtkimageviewer, vmtk assumes that they share the 
> same patient position and therefore share the same origin. Consequently when 
> the vessel and bone scans are segmented, they are clearly misaligned.  Does 
> vmtk assume the same patient position when overlaying any two image sets (the 
> sets share the same number of pixel rows and columns and number of images 
> (512x512x512); additionally, they have the same pixel spacing)? Is there a 
> way to explicitly give vmtkimagereader the patient position of each image 
> set, so that the corresponding segmentations will be aligned?
> 
> Thank you for your help,
> Anna
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