[Insight-users] Getting overlap region

Andreas Schuh andreas.schuh.84 at googlemail.com
Tue Feb 17 06:24:00 EST 2009 

Hi!

Well, that's more or less the same issue, when I was thinking about  
this overlap thing. Well, I got a solver from a fellow that computed  
an overlap cube of two other cubes that has minimal extent/volume,  
where the direction of this cube is the one of the coordinate system  
(this solver is based on a simplex approach I think). I've implemented  
an ITK filter that uses this solver to get an ImageRegion and  
Direction matrix (orientation of the overlap cube), where I set the  
direction to the direction of the fixed image. These can then be  
passes to ResampleImageFilter to resample both images, fixed and  
moving, within the overlap. Unfortunately, my current implementation  
doesn't work. However, I didn't focus on this any more as for me, it  
was enough to just resample both images on a grid with the same  
direction and extent as the fixed image. This is because non- 
parametric registratration requires non-rigid pre-registration in most  
cases. So the misalignment of the image regions themselves isn't that  
much (and the borders seldomly contain something of interest). After  
pre-registration you could also just resample the images on a grid  
with the direction of the fixed image but the extent large enough to  
cover at least both fixed and moving images.

I think I just have an idea how you can get the mask you want.

Resample the moving image on a grid that has the same direction and  
size as the fixed image. So, use ResampleImageFilter and set the fixed  
image as reference image. Set the outside value appropriately to  
reflect the "masked out meaning".
Depending on the mask format your metric assumes, you may just use the  
resulting image as mask or apply a threshold to get a binary mask image.

--
regards
Andreas

Am 17.02.2009 um 09:43 schrieb Erik Türke <erik_tuerke at hotmail.com>:

> Hi!
>
> Thanks for the response.
>
> I´ll try to explain yout the issue.
> It is all about a regsitration problem.
> I have two images, a fixed and a moving image. Lets consider the  
> fixed image is of dimension [192 130 192] and the moving image is of  
> dimension [192 7 192].
> The metric will give you a sample exception error because too many  
> samples are outside the moving image.
> Now, what i want to do is to define a mask, which contains the  
> overlap of the two images and pass it to the metric- 
> >SetFixedImageMask() method, which expects a ImageMaskSpatialObject.
>
> So now my problem is how to compute an overlap(image, spatialobject)  
> containing the fixed and the moving images, or the fixed and the  
> moving spatial objects, respectively.
> And i assume, i am capable of creating an ImageMaskSpatialObject  
> with the help of the obtained overlap image or object and pass it to  
> the metric.
>
>
> thanks and best regards!
>
>
> > From: andreas.schuh.84 at googlemail.com
> > To: luis.ibanez at kitware.com
> > Subject: Re: [Insight-users] Getting overlap region
> > Date: Mon, 16 Feb 2009 12:11:05 +0100
> > CC: erik_tuerke at hotmail.com; insight-users at itk.org
> >
> > Hi,
> >
> > the difference of determining the overlap region of two single
> > ImageRegions and of getting the overlap of two oriented images or
> > spatial objects is, that in the former case the regions are not
> > oriented (considered having the same orientation) whereas in the
> > latter cases you may have to be corncerned with the orientation of
> > your regions, too. In this case ImageRegion::Crop won't help if you
> > would like to have the oriented overlap region of minimal volume.
> > That's a more difficult task, where you will have to solve some
> > optimization problem probably by some kind of simplex algorithm.
> >
> > Otherwise, as you Erik are interested in spatial objects and I  
> assume
> > that the bounding boxes of these (SpatialObjects::GetBoundingBox)  
> are
> > all oriented along the axes of the coordinate system, you have a
> > simpler task which can be solved by using ImageRegion::Crop.
> >
> > --
> > regards
> > Andreas
> >
> > Am 15.02.2009 um 22:52 schrieb Luis Ibanez  
> <luis.ibanez at kitware.com>:
> >
> > >
> > > Hi Erik,
> > >
> > > The easiest method is among ImageRegions.
> > >
> > > In that case, simply use:
> > >
> > > itk::ImageRegion::Crop()
> > >
> > > If you have two image regions
> > >
> > > itk::ImageRegion regionA;
> > > itk::ImageRegion regionB;
> > >
> > > Then you can find the overlap by doing
> > >
> > > regionA.Crop( regionB )
> > >
> > > The common region will be stored in the
> > > variable regionA.
> > >
> > >
> > > Regards,
> > >
> > >
> > > Luis
> > >
> > > ------------------
> > > Erik Türke wrote:
> > >> Hi!
> > >> Thanks for your response.
> > >> Actually it doesnt matter, if i am doing this with an image, an
> > >> image region, or spatial object, since you can convert these  
> types
> > >> amoung themselves. I guess ;-)
> > >> I think, i would prefere the easiest method.
> > >> But if there is no difference between the effort of these  
> methods,
> > >> i would take the SpatialObject method.
> > >> Thanks!
> > >> best regards!
> > >> > Date: Thu, 12 Feb 2009 11:16:21 -0500
> > >> > From: luis.ibanez at kitware.com
> > >> > To: erik_tuerke at hotmail.com
> > >> > CC: insight-users at itk.org
> > >> > Subject: Re: [Insight-users] Getting overlap region
> > >> >
> > >> >
> > >> > Hi Erik,
> > >> >
> > >> > You question is too general.
> > >> >
> > >> > Could you elaborate on it please ?
> > >> >
> > >> > Do you :
> > >> >
> > >> > a) Have two images and want to create a third
> > >> > image containing the overlap of the two images ?
> > >> >
> > >> > OR
> > >> >
> > >> > b) Have two itkImageRegions and want to compute
> > >> > the itkImageRegion that represents the overlap
> > >> > of the two ?
> > >> >
> > >> > OF
> > >> >
> > >> > c) Have two itkSpatialObjects and you are trying to
> > >> > compute the itkSpatialObject representing their
> > >> > overlap ?
> > >> >
> > >> >
> > >> >
> > >> > Thanks
> > >> >
> > >> >
> > >> > Luis
> > >> >
> > >> >
> > >> > ------------------
> > >> > Erik Türke wrote:
> > >> > > Hi!
> > >> > >
> > >> > > I am asking myself if there is any possibility to get the
> > >> region of an
> > >> > > overlap of 2 images or a new object containing the overlap  
> of 2
> > >> other
> > >> > > objects, respectively.
> > >> > >
> > >> > > Thanks fr your help!
> > >> > >
> > >> > > Best regards!
> > >> > >
> > >> > >
> > >> > >
> > >> > >
> > >> ---
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