[Insight-users] Problems with SetFixedImageMask, MattesMI, BSpline Transfo. and RegularStepGradientDescentOptimizer

[sere f]

Hi All,
I am registering CT and MRI of the brain with Bspline Transformation,
Mattes-MI, RegularStepGradientDescentOptimizer.
The registration works fine.

But when I set:

spatialObjectMask->SetImage( maskReader->GetOutput() );

metric->SetFixedImageMask( spatialObjectMask);

The Registration ends with 0 iteration and I get this message:

Optimizer stop condition = RegularStepGradientDescentOptimizer: Gradient
magnitude tolerance met after 0 iterations. Gradient magnitude (0) is less
than gradient magnitude tolerance (0.001).

My mask is a binary image (0,255). Is it wrong?
How can I register using a mask for Fixed Image?
any idea?

Thank you very much.

Serena.
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