[Insight-users] Can a metric be negative in ITK?

[Christopher Kappe]

So it's absolutely normal that this metric returns negative values and it's 
okay when they get even "more negative" during the registration process. (?)

Paul Muetze

Am Freitag 02 März 2012, 12:04:01 schrieb Rick Frank:
> "High" negative  is what you want from this metric, as I understand it.
> 
> Rick
>
> 
> Hello everybody, 
> 
> I'm new to this list. 
> I'm trying to do registration with two 3D images. I basically used the
> ImageRegistration8.cxx example (using itk 4.0 btw) but with
> MattesMutualInformationMetric instead of MeanSquaresMetric. 
> And, well, I got output like this from the observer: 
> 
> 0   -0.00130253  
> 1   -0.000181399 
> 2   -0.00019049   
> 3   -5.82618e-06
> 4   -6.76423e-06 
> 5   -1.81517e-05  
> 6   -1.78196e-05   
> 7   -7.79246e-06  
> 8   -4.0121e-06
> 9   -3.87818e-06 
> 10   -1.20782e-05   
> 11   -2.655e-06   
> 12   -1.13154e-05  
> 13   -7.53967e-06  
> 14   -8.0584e-06  
> 15   -3.52788e-06 
> 16   -2.35729e-06
> 17   -5.10754e-06
> 18   -6.61478e-05
> 19   -0.000101335
> ...
> 49   -0.000806308 
> Optimizer stop condition: VersorRigid3DTransformOptimizer: Maximum
> number of iterations (50) exceeded.
>           Probe Tag    Starts    Stops             Time (s)
>         Registration           1            1           4509.42
> 
> The thing is, it's not even converging (at least not towards 0).
> And is it okay to get a negative metric as result in the first place?
> 
> Best
> Paul Muetze