[Insight-users] Sub-volumes registration

[Luis Ibanez]

Hi Nic,

How are you extracting the subvolumes from the large volumes ?

If you use the RegionOfInterestImageFilter, the final transform
obtained from the registration of the subvolumes should be *directly*
applicable to the larger volumes.

This is because the origin of the subvolumes would be correctly computed
so that they are placed in the correct location in physical space
with respect to the original larger volume.

If you compute the origin of your subvolumes correctly, then you are
still performing registration in physical coordinates, and no further
modification of the transform should be needed once you complete the
registration of the subvolumes.

That's the most consistent way of performing your registration.


   Regards,


       Luis


-------------
Nic wrote:
> Hi all,
>     I'm a in trouble for the very last step of my registration program 
> when merging stacks, help would be greatly appreciated, deadline is 
> coming ! :)
> My registration process is actually successful, I get a correct 
> registration result which can perhaps be refined with a finer 
> interpolator, but that's another story.
> Result is here: http://itk.tiboufroulou.com/final.png (slice 
> view), http://itk.tiboufroulou.com/final3D.png (3D view)
>  
> Actually I registrate two sub-volumes resulting from two big stacks. 
> Because doing the registration process with the full stacks loaded is 
> impossible (avaible memory and time consuming problem), I only load the 
> two subvolumes for the registration. The problem now is to "translate" 
> my final transformation for the two subvolumes in a transform for the 
> two full stacks, I tried to set the rotation center and add translation 
> to the final parameters, but I don't think it is the good way and if it 
> is even possible to reach a solution..
> On the other hand, back to itk manual, I'm wondering if there is a 
> possibility to force registration only on subvolume regions (thinking 
> about set fixedimageregion, setfixedimagemask, setmovingimagemask), thus 
> loading the full stacks but only doing registration with subvolume data, 
> final transformation taking into account the whole stacks..
> Kind regards, nic
>  
>  
> Supplementary informations:
>  
> At the beginning, two big volumes of images (2048 x 2048 x min120 
> images), those volumes have a common volume present in each stack, 
> always near the top of each stack because the images stacks result from 
> a two-side scan of a sample, from outside until a little farther than 
> the middle. The idea is to registrate the stacks on the two subvolumes: 
> http://itk.tiboufroulou.com/schema.png. Identification of position of 
> subvolumes is made through a GUI (browsing both images stacks). For 
> initialisation, a 180° rotation around oy-axis then a rotation around z 
> identified through superposition view in GUI is made (Superposition 
> view: http://itk.tiboufroulou.com/superposition.png). Finally, centers 
> of subvolumes are calculated geometrically, center of moving image have 
> an (x,y) offset added, offset resulting from a translation visually made 
> on GUI (same view as above); the offset observed in GUI is transformed 
> by the intial transformation(the two successive rotations)  and then 
> added to the moving center. Initial transformation is thus initialized 
> with the two successive rotation and the 
> translation(movingCenter-fixedCenter calculated above)
> 
> 
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