[Insight-users] Registration and transformation of images

[Luis Ibanez]

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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