[Insight-users] registering images from thumbnails

[Kevin H. Hobbs]

If you used ITK to sub-sample the images, and sub-sampled and registered
the images in the same application, or used a file type that knows about
image spacing.... you should be able to use finalParameters as is.

These parameters do not know anything about pixel spacing.

I added all those caveats because if the pixel spacing and image origin
are not preserved when the thumbnails were made then the translation and
rotation would not be useful.

On Fri, 2009-05-22 at 20:09 +1000, Mauro Maiorca wrote:
> Hi all,
> 
>  I'm registering 2 CT volumes (rigid transformation). In order to
> speed up the process I'm subsampling the original images prior to
> registration. I'm using ImageRegistration8.cxx on the two thumbnails
> (fixed and moving image) and it's working fine: the two thumbnails are
> pretty much aligned. Now, how to apply the transformation to the
> original moving volume?
> 
> I guess, prior to "transform->SetParameters( finalParameters );" I
> have to retrieve the registration parameters:
> 
>  OptimizerType::ParametersType finalParameters =
> registration->GetLastTransformParameters();
> 
> and modify parameters according to the subsampling ratio, but I'm not
> sure about how the parameters are actually stored in
> OptimizerType::ParametersType, there are mm? rotation is in radiants?
> In which order are stored? There is any ITK function to automatically
> calculate the actual parameters, or should I calculate them manually?
> 
> thanks,
> Mauro
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