[Insight-users] Re: i am puzzled, please help me! : Mutual Information and Image Registration

Luis Ibanez luis.ibanez at kitware.com
Sat Sep 4 12:11:08 EDT 2004

Hi Carole,

ITK provides three different implementations of the Mutual Information
metric.  For a full account of the Image Metrics available in ITK
please look at


For a detailed explanation of the Image Registration framework in ITK,
including the Image Metrics, please read the ITK Software Guide


Chapter 8, pdf-pages 241 to 340.

Read also the tutorials on Image Registration methods
that are available at


in particular




You will also find useful the online book on Medical Image Registration
by Joseph Hajnal, D. J. Hawkes, Derek Hill.


A forum for discussions in Image Registration is available in the
ITK Wiki pages


more specifically at


Is your interest in "innovation" motivated by the need of publishing
a paper in order to include it in your CV ?

If so, you may want to explore the intricate mathematical issues related
to the estimation of joint entropy in Mutual Information. That will
generate enough equations for making your paper look involved. It may
be relatively useless for real applications, but that doesn't really
matter if your goal is to publish.

If instead of just publishing, you are interested in further developing
techniques that may actually be useful for processing images for medical
applications, then you probably may want to take a look at more
sophisticated Image Metrics that may simultaneously combine Mutual
Information with Edge information. This has been proposed in the past,
but we don't have an implementation in ITK yet. As you will notice from
reading the documents above, Mutual Information focuses in matching
large regions on the images. It doesn't particularly consider the edges
of structures in the images. It is therefore interesting to introduce
some edge-related factors in order to obtain a more powerful metric.

Please let us know if you have further questions.



张 卡璐 wrote:
>    hi, i am a new user of ITK, and i am engaged in research in medical 
> image processing, especially image registration. As far as I know, 
> mutual information is used to image registration and is quite effective.
>    I want to combine ITK with mutual information to apply to the medical 
> image registration. But I am puzzled how to innovate.    Please give 
> directions to me.
>    Thanks for your advice!
>  carole

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