[Insight-users] Speed of Mutual Information calculation

[Markus Weigert]

Dear insight users,

I currently try to register two 3D images (CT and MR)
by using mutual information as metric.
The images have a size of approx. 255 * 290 * 75 slices each (MR perhaps even more).
Although I use a very simple transformation (translation) and a graddescent
optimizer, one iteration of the optimizer takes more than 1.5h.

Is this a common time for images of this size???
The metric uses 60000 spatial samples.
I thougt about using BSpline transform in the next step of the registration
with MI metric too, but I think I can forget to do this, if I have to deal with 3000 Parameters
to be optimized!

Regards,
Markus
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