[Insight-users] Rigid registration testing and reproducibility

[Andriy Fedorov]

Hi,

I would like to do regression tests of rigid registration with real
images, and compare the result with the baseline transform. Here are
two related questions.

1) ITK registration experts, could you speculate on what is the normal
variability in the rigid registration results run with the same
parameters, metric initialized with the same seed, when run across
different platforms? What could be the sources of this variability,
given the same initialization and same parameters?

2) If I understand correctly, the current testing of registration that
comes with ITK generates a synthetic image with known transform
parameters, which are compared with the registration-derived
transforms.

The testing framework implemented in itkTestMain.h allows to compare
pixelwise two images, but this does not seem to be practical for
registration regression testing, because of the variability in the
registration results I mentioned earlier. Accounting for this
variability using tolerance values of just 1 pixel hugely increases
the test runtime, but in my experience, the comparison may still fail.

Would it not make sense to augment itkTestMain.h with the capability
to compare not only images, but transforms? Is this a valid feature
request, or am I missing something?

Thanks

Andriy Fedorov