[Insight-users] Registration - Mutual Information Metric - Sampling from Moving Image

[Luis Ibanez]

Hi Sharath,

You are right in that it is not a good idea to take samples
from the entire 2000 x 2000 pixels image if we expect that
only a regions of 640 x 480 is going to match the Moving
image.

The solution is to simply call

            registration->SetFixedImageRegion( region )

 and set "region" to the region of interest from the
2000 x 2000 image, where you anticipate to find matches
for the moving image.


You will find examples on the use of

       SetFixedImageRegion()

in the ITK software Guide

       http://www.itk.org/ItkSoftwareGuide.pdf

and most (if not all) the corresponding Image Registration
examples in

            Insight/Examples/Registration




   Regards,


         Luis



---------------------------------------------------------------
On Fri, Jul 10, 2009 at 9:15 PM, Sharath Venkatesha
<sharath20284 at yahoo.com>wrote:

>
> Hi,
>
> I am working with images where the Fixed image is 2000*2000 pixels and the
> moving image is 640*480 (sub region of the fixed image). In all the Mutual
> Information metrics, the sampling is done on the Fixed image, and the
> transformed points are mapped on the moving image.
>
> I figured out that it is incorrect to sample the points randomly in the
> full fixed image ( as in my case, the moving image is a sub-part of the
> fixed image, and only 30-40% points were mapped), I used an approximate
> region of the fixed image from which sampling should be done. This has not
> improved the performance/accuracy of registration.
>
> I am thinking of sampling pixels from the moving image, and do a backward
> mapping to pixels in the fixed image. In this case, I think that almost all
> the points will be mapped, and hence the metric will be better.
>
> Do I need to change the functions in the respective files, or is there a
> simpler way to do this, or is already implemented?
>
> Thanks,
>
> Sharath Venkatesha
>
>
>
>
>
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