[Insight-users] Registering Low Contrast Images

[Luis Ibanez]

Hi Vikren,


1) Yes, it is possible with ITK to compute the rigid transform that
    will map the coordinate system of your fixed image into the
    coordinate system of the moving image.


2) Could you post screeshots of your low contract images in a public
    web site ?

    Being able to see the images will help us a lot for recommending
    you an image metric to use.


    In the absence of being able to see your image, here are two
    suggestions that come to mind:

           A) Normalized Correlation metric

           B) Passing your images through edge detection filters
              and then using the results as the actual images to
              register. (you will find several edge-detection
              filters in ITK, you probably want to start with
              a simple gradient magnitude filter).


           C) Mutual information is still an option that you
              could reconsider, and for which you may have to
              adjust the parameters of number of bins and
              number of samples.



In general, you should be careful discarding a particular technique
based on having tried it once, with only a reduced set of parameters.

It is not uncommon that for a fine-tunning exercise to be required
before you get acceptable results with a given technique.



     Regards,


        Luis


---------------------
Vikren Sarkar wrote:
>     Greetings,
> 
>      
> 
>     I am new to ITK and am trying to use the registration algorithms to
>     register two 3D x-ray image datasets. The problem is that all the
>     images have very low contrast and the intensity-based algorithms
>     fail when used with the mean square metric (I also tried mutual
>     information with no success). I need to perform a rigid registration
>     and am hoping someone with more experience could suggest a metric
>     which would be appropriate for use with low contrast images.
> 
>      
> 
>     Alternatively, I am open to the idea of using control points which
>     the user would input. I am most interested in the actual values of
>     translation, rotation and scaling required for the registration than
>     in the final registered datasets themselves. The reason is that we
>     are investigating the use of those images in patient positioning
>     prior to radiation delivery. Can someone please point me in the
>     right direction as to whether this is possible using ITK? It is
>     probably obvious that I am very new at this and I would appreciate
>     any help and/or pointers. Thank you.
> 
>      
> 
>     Vik
> 
>      
> 
> 
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