[Insight-users] question on transforming points

[John Jan Drozd]

Hi Luis,

It's nice to talk with you again.
I am using a Bspline deformable transform and I am initializing it  
with an affine transform. I am using a course bspline deformable  
transform followed by a finer resolution bspline deformable transform.  
This gives me greater accuracy and the code runs much faster using  
this multi-resolution approach. I used and modified code to work with  
3 dimensional dicom brain images from deformableregistration8.cxx and  
deformableregistration15.cxx.  In mapping my points, I now realize  
that I have to transform the fixed point twice, first with the course  
transformation and then with the finer transformation. I was only  
transforming the point with the finer transformation and that's one  
possibility why my transformation of a point from the brain ventricles  
in the fixed image did not map that accurately to within ventricles in  
the moving image. I use these as a way of automatically generating  
seed points for a region growing algorithm.

Thanks for clarifying that the bsplinetransform takes care of the  
origins.

Take care,
John

Sent from my iPhone

On 2010-04-17, at 6:57 PM, Luis Ibanez <luis.ibanez at kitware.com> wrote:

>
> Hi John,
>
>
> 1) What Transform are you using ?
> 2) How did you initialize it ?
>
>
> If you are following any of the BSplineDeformable
> Transform as shown in the examples in
>
>                Insight/Examples/Registration
>
> then the Transform will include the translation
> between the image origins.
>
>
>      Regards,
>
>
>             Luis
>
>
> --- 
> --- 
> --- 
> --------------------------------------------------------------------
> On Thu, Apr 15, 2010 at 5:30 PM, John Drozd <john.drozd at gmail.com>  
> wrote:
> Hello,
>
> I perform a multi-resolution deformable registration between 2 MRI  
> images from 2 different people using a multi-modal metric.
> Then I map points from the fixed image to the moving image using the  
> transform obtained from the registration using TransformPoint();
> Do I need to include the difference between the coordinates of the  
> origins of both or either images in my calculation, or does the  
> TransformPoint take care of this?
>
> Thank you,
> John
>
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