Domain of rigid mask in Rigidity Penalty

[Hengjie Liu]

Hello all,

I have a question regarding the rigidity penalty described in the paper: M. Staring, S. Klein, and J.P.W. Pluim, "A Rigidity Penalty Term for Nonrigid Registration". 

If I understand correctly, the transformation in Elastix is defined on the fixed image domain. Therefore, the rigidity mask should also be applied to the fixed image domain. However, in the paper above, it said "The rigidity coefficient image only has to be defined on the moving image". I also found similar descriptions in https://elastix.lumc.nl/doxygen/classelastix_1_1TransformRigidityPenalty.html. I am very confused and not sure which part I missed.

Thank you in advance for any help!

Best,

Hengjie