[elastix] penalty on registration

M.Staring at lumc.nl M.Staring at lumc.nl
Tue Mar 2 10:00:28 CET 2010

Hi Xi Liang,

> Currently I am using metric of 
> "MattesMutualInformationWithRigidityPenalty". I understand 
> that by using this metric, and area of mask has rigid 
> registration. Are there any penalty applied on the area 
> outside the mask? E.g. any kind of regularization?
> My understanding is that the metric value on the masked area 
> is MI + penalty, and other non-masked area in just MI. Am I 
> correct here?

Actually, it is a bit different, which is due to the B-spline transform.
When you move a B-spline control point, it not only has an effect at the
position of that control point, but also in its neighbourhood, due to
the (compact) support of the basis functions. The size of this
neighbourhood is related to the order of the B-spline, which is 3 in
your case, so the neighbourhood size in which the transformation is
different from MI without the penalty term is 4 * gridspacing. I mention
that in section II-C of the paper, and in the conclusion.

Hope that clarifies things,


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