[Insight-users] Minimum size of image in image registration?

[motes motes]

I am playing around with the BSplineDeformableTransform example.

I run it for 300 iterations on a 2D image of Lena. When I run it with
512*512 versions I get a reasonable result, metric value = 218.566.

I also have a 256*256 version of the images. If I use those instead
(still 300 iterations) I get a very poor result (actually the
registered image is just a salt and peber image) metric value =
1.56493e+007.

It seems that using the BSplineDeformableTransform only makes sense on
images with at least 512*512 pixels or am I missing some other
parameters that can be tuned for smaller images?