[Insight-users] Registration and transformation of images
Luis Ibanez
luis.ibanez at kitware.com
Tue Jul 12 13:19:47 EDT 2005
Hi Julian,
This topic discussed in great length in the ITK Software Guide
http://www.itk.org/ItkSoftwareGuide.pdf
in Section 8.3 "Features of the Registration Framework",
pdf-page 348-352.
Regards,
Luis
-------------------------
Julian Tam wrote:
> Hello,
>
> I am hoping that someone can confirm my understanding of the
> registration and transformation processes in ITK. I've included
> snippets of code from DeformableRegistration4.cxx with my own comments
> for clarity.
>
> Ultimately, the goal is to transform the moving image to the fixed
> image. However, from reading the Software guide, I understand that
> the registration will produce transformation parameters that map the
> fixed image to the moving image.
>
> registration->StartRegistration();
> OptimizerType::ParametersType finalParameters =
> registration->GetLastTransformParameters();
>
> We use these parameters to set up the TransformType instance:
>
> transform->SetParameters( finalParameters );
>
> And supply it with the moving image, and the information about the
> fixed image's coordinate system to the ResampleImageFilter instance:
>
> resample->SetTransform( transform );
> resample->SetInput( movingImageReader->GetOutput() );
> resample->SetSize( fixedImage->GetLargestPossibleRegion().GetSize() );
> resample->SetOutputOrigin( fixedImage->GetOrigin() );
> resample->SetOutputSpacing( fixedImage->GetSpacing() );
>
> The filter applies the transformation to the coordinate system of the
> fixed image, on which the moving image is then placed. Corresponding
> points on the transformed coordinate system with the moving image on
> it are then matched up with those of the undeformed coordinate system
> of the fixed image, allowing the fixed image's coordinate space to
> contain the (deformed) moving image.
>
> resample->GetOutput() // produces the moving image that is
> transformed to match the fixed image
>
> In this way, by supplying the moving image and the transformation that
> maps fixed to moving to ResampleImageFilter, we can actually transform
> the moving image to match the fixed image.
>
> I am particularly unsure about the last part, and would greatly
> appreciate any advice or corrections.
>
> Thank you,
> Julian Tam
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