[Insight-users] 3D rigid registration

[Karthik Krishnan]

Grace Chen wrote:

>Hi,
>
>If I center just one image and shift another image....
>
What do you imply when you say :
"If I center just one image and shift another image" ?

  A minimal example might help

>The result is quite
>different (slice shift 2 slices forward) from if I don't center any input
>images....
>
>Can some ITK people please tell me if I should center input images at all??
>  
>
If you have datasets of the same anotomical region, acquired in the same 
manner, it is sometimes useful them via their geometrical centers:
http://www.itk.org/Insight/Doxygen/html/classitk_1_1CenteredTransformInitializer.html

You will need to look at the datasets to see if aligning them via their 
geometrical centers makes sense. There is no hard and fast rule here.

There are several examples that you can refer to on using this class:

./Registration/ImageRegistration12.cxx
./Registration/ImageRegistration13.cxx
./Registration/ImageRegistration14.cxx
./Registration/ImageRegistration6o.cxx
./Registration/ImageRegistration7o.cxx
./Registration/ImageRegistration6.cxx
./Registration/ImageRegistration7.cxx
./Registration/ImageRegistration8.cxx
./Registration/ImageRegistration9.cxx

>  
>
>>Hi there,
>>
>>To use VersorRigid3DTransform for 3D rigid registration, should we center
>>both of the input imgaes?  It seems wrong to center both images.....If we
>>need to center just one image, which one, the fixed image or the moving
>>image??
>>    
>>
To clarify:  When you "center images", you are computing the transform, 
which when applied to the moving image would align the two images via 
their geometric centers. It is one way of starting the registration from 
an initial transform.  I suppose, you have a different notion of "center 
images prior to registration".

>>Please help!  This part of using ITK can't seem to be found anywhere....
>>Thanx!
>>
>>Grace
>>
>>    
>>
>
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>