[ITK] [ITK-users] Demons Registration on a Region of Interest

[Loic Le Folgoc]

 From the previous mails I'd assume you tried this as a starting point 
but just in case: you did try to pass a smaller region as requested 
region for the output 
(filter->GetOutput()->SetRequestedRegion(my_region) before calling 
filter->Update()), didn't you? From a quick glance at the cascade of 
filters which the DemonsImageFilter inherits from, it's not obvious that 
the filter does not respect the requested region set by the user for the 
output.

Otherwise, assuming your images are already affinely registered, it 
should be fairly safe to only run the algorithm on cropped images as 
suggested, yes, especially if you expect the motion at the boundary of 
your smaller domain to be roughly null.

Another silly question/comment in case none of the above helps, and 
before you decide to invest time adapting the code: is the runtime of 
the demons algorithm an annoying bottleneck to you? I'd imagine it's one 
of the fastest algorithms out there. If it's fast enough, maybe you can 
just run it on the full images regardless.

Le 31/10/2015 17:07, Nhung Pham a écrit :
> Normally with Python, I can register one template( e.g: a center 
> region of reference image) to the target image to find the 
> corresponding position of the template in the target image. In this 
> Demon Registration algorithm, we of course do not know the position of 
> the template in the fixed image, so my goal is not to register two 
> smaller images but to find the best match of the small region in the 
> fixed image, or do you mean I should do registration with small 
> regions of fixed image iteratively? (Sorry, my English is not so good)
>
> Best regards,
> ===============================
> Phạm Hồng Nhung,
> ICT Department,
> University of Science and Technology of Hanoi.
> Mobile: +84979093732
> Gmail: phnhung98 at gmail.com <mailto:phnhung98 at gmail.com>
> Skype: phnhung98
>
> On Sat, Oct 31, 2015 at 4:51 PM, Dženan Zukić <dzenanz at gmail.com 
> <mailto:dzenanz at gmail.com>> wrote:
>
>     Have you tried extracting only the regions of interest using RoI
>     <http://www.itk.org/Doxygen/html/classitk_1_1RegionOfInterestImageFilter.html>
>     filter and registering these two smaller images? That is the usual
>     workaround if some filter does not respect requested region.
>
>     HTH
>
>     On Thu, Oct 29, 2015 at 9:49 AM, HONG NHUNG PHAM
>     <hong.nhung.pham at univ-poitiers.fr
>     <mailto:hong.nhung.pham at univ-poitiers.fr>> wrote:
>
>         Hello everyone,
>
>         I want to apply Demons Registration to register two medical
>         images, the image information is strong at the center,
>         therefore I want to apply registration method on only the
>         center region of the images. For example, take a center region
>         of moving image, and find the corresponding positions of each
>         pixel of the region in the fixed image. However, I can not
>         find a method that allows processing on a region like that in
>         itkDemonsRegistrationFilter.h. I tried passing the full fixed
>         image as SetFixedImage, and only the center region of moving
>         image as SetMovingImage. However, it crashes because it
>         requires same size of fixed image and moving image.
>
>         Does anyone have any idea of how to pass a region to demons
>         registration filter?
>
>         Thank you in advance!
>
>
>
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