[Insight-users] Registration (itk Plugin for volview)

[Atwood, Robert C]

I have tried the registration (ITK) 'plugin' for Volview, and there is
something I don't quite understand ... Since my lack of understanding
extends to the underlying ITK algorithm perhaps I can ask on this list
...


First, I tried rotating a sample volume (with my own code) and then
registering with the original. That worked perfectly. 

Then, I tried an 'erosion' on one of the images and tried registering
again. In this case, of course it was not quite as good, but the puzzle
is that it appears that one of the voumes is magnified , instead of only
rotated and translated. 

Since my aim is to measure the difference in size between the same
object imaged before and after some experments, I would rather not  use
the image size as one of the variable parameters. 

I read over the ITK: Quaternion Rigid Transform section of Registration
in the ITK software guide, the final paragraph of 8.7.9 implies that the
transformation is renormalized to avoid scaling, and I was under the
impression from the dialog box that this is the transform used by the
plug in. 

Is the scaling behaviour in the volview plugin intentional? 



If I implement a (3-d) registration using ITK  will the rigid quaternion
transform avoid any changing of scale ? Or, should Versor Rigid 3d
transform be used? 

Robert