[ITK-users] How to use rotation matrix and translation to perform Rigid 3D transform?

[paniwani]

Hi,

I'm trying to transform a PET scan onto a CT scan based on an existing
rotation and translation matrix. I exported the PET and CT scan from a
Radiation Oncology treatment planning system. The system also exported a 
dicom spatial registration object file
<ftp://medical.nema.org/medical/dicom/final/sup73_ft4.pdf>   which contains
a transformation matrix that specifies exactly how to translate the PET onto
the CT scan. The registration is just a simple rigid registration. I'm now
trying to perform that same registration in ITK for use in my application. 

The transformation takes the following form (defines the rotation as M [9
parameters] and the translation as T [3 parameters]).

<http://itk-users.7.n7.nabble.com/file/n36114/matrix.png> 

>From what I've searched online, it seems that I can use ITK 
Rigid3DTransform
<http://www.itk.org/Doxygen/html/classitk_1_1Rigid3DTransform.html>  , which
also requires 12 parameters total. However, in the documentation, it says:

"The Rigid3DTransform is intended to be a base class that defines a
consistent family of transform types that respect rigid transformations.
Only classes that derive from Rigid3DTransform should be used."

Can I still use this transform? Is this the right use case? How do I go
about using it correctly? From the ITK software guide and the documentation,
I came across other transforms such as Versor, Euler, and Affine; however,
they seem to specify the rotation differently and require conversions which
I think may be unecessary.

Another hurdle is that up to this point I have been using SimpleITK in
python and I do not think the Rigid3DTransform class is available in
SimpleITK. Will I have to use original ITK to perform this transform?

Thanks in advance for the help! 




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