[Insight-users] Image to Spatial Object Metric

[Luis Ibanez]

Hi Antonio,

the ImageToSpatialObjectRegistrationMethod<> that is illustrated in the
examples

     Insight/Examples/Registration

                ModelToImageRegistration1.cxx
                ModelToImageRegistration2.cxx

should, in principle, work with any of the ITK Transforms.

It is likely that the problem that you faced when using an Affine 
transform are more related to:


         A) Poor choice of parameter scaling values (the array
            that is passed to the Optimizer in order to compensate
            for the difference in dynamic range between Translation
            and Rotation/Scale components.

         B) Poor choice of Optmizer parameters.


Of course, the option of writing your own Metric is always worth
considering, but that is independent of the need for solving (A)
and (B) properly.


In general, when you report that something "doesn't work", it is
very helpful to describe *exactly* what the result was, and how
do you arrive to the conclusion that "it doesn't work".

Please give us more detail on what you observed....


     Thanks


        Luis



---------------------------
Antonio Foncubierta wrote:
> Hello,
> 
> I am trying to develop a Model Based Registration Method, and I started 
> using the example mentioned by the Itk Software Guide and included in 
> the 3.6 version of Insight: ***ModelToImageRegistration1.cxx***. I have 
> been trying to adapt the example to work with my data: 3D Images. 
> Achieving that was not a big deal, but I started to struggle when I 
> wanted the Transform to be an itkAffineTransform, which includes a scale 
> change. The example explicitly says that the 
> SimpleImageToSpatialObjectMetric is designed considering no scale 
> changes, and it says it right, because the metric doesn't work as I 
> required. (It does work as expected, though).
> 
> So my main problem now is finding a way to define a metric that 
> maximizes both the ****number of Spatial Object Points inside the 
> Image**** and the ****Spatial Object Volume****. The first one is easy, 
> as it is exactly what the above mentioned example does, but I haven't 
> found a way to compute the Transformed SpatialObject Volume.
> 
> And that's why I ask you if any of you have found a similar problem and 
> how did you solve it. Also, if any of you know a not-as-simple metric 
> which I could use.
> 
> Thank you in advance,
> 
> PS: The explanation migh be very blurry, so if you don't undersrtand 
> anything of it, please, just ask. I'd rather repeat things in a 
> different way, or attach images to not having help at all ;)
> 
> Antonio Foncubierta
> 
> 
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