No subject

simple first step described above. If the optimizer appears to be
moving away from the expected parameter values, it could be that it is
minimizing instead of maximizing (or vice versa).
RegularStepGradientDescentOptimizer has the function SetMaximize(bool)
which controls which direction it operates.

If you haven't already, I would really recommend you read the ITK
Software Guide (chapter 8)
    http://www.itk.org/ItkSoftwareGuide.pdf
and look at the registration examples
    Examples\Registration

Hope this helps.

Regards, Dan

2009/6/23 Fischer, Sven <Sven.Fischer at medizin.uni-leipzig.de>:
> Dear all,
>
> I want to do an registration between CT and MRI images. I use RegularStep=
GradientDescentOptimizer with MutualInformationImageToImageMetric for that =
task. I begin with loading the DICOM images with vtk and transform it to an=
 ITKImage with VTKImageToImage filter, I register the images and transform =
them with ResampleImageFilter and  AffineTransform and transform them back =
to VTK to display them.
> Now when I display the images I find that they aren=B4t registered. I tri=
ed different settings on the optimizer and metric but nothing worked. I eve=
n found that two images that are already registered will be misregistered a=
fterwards. When I display the MI value during the iterations I find that it=
 is geting worse sometimes and the final is not always the best that was fo=
und in an earlier iteration step. Shouldn't it go back into direction of th=
e best value if it finds a worse? Is that a mistake in the Optimizer? Could=
 you give me an advice which Optimizer to use and how to set the settings f=
or Optimizer and Metric?
> Could it be up to transforming the images between VTK and ITK? Is it impo=
rtant which ImageTypes/PixelTypes I use for Transforming, registration and =
transform between VTK/ITK?
>
> Regards
> Sven