Rigid transformation parameters not equal

[jeremysong1106]

Hi, I used torchio to generate some moved 3d image ,which by applying the translation(pixelwise) and rotation(degree) to the still image(without motion), and use the network RigidIRNet to estimate this translation and rotation parameter.

Then I found that although the NCC loss are decreased and the warped image is acceptable, the estimated parameter have a big different compared with the one that I appied beforehand.

May I ask why is the issue for this weird situation ?