[Insight-users] Re: Registration ....still a mystry

[Luis Ibanez]

Hi Soumen,

There is not much that we could tell you
about the registration process that is not
already described in the Software Guide.


Here are some issues
you may want to look at:


1) You don't need to have the same origin
    nor spacing between the two images that
    your are registering.  You just need to
    make sure that the values of spacing for
    each image really correspond to their
    physical values.

2) According to your previous email you haven't
    still succed to load the image data into
    an ITK image. There is no hope in attempting
    a registration if the image data is not loaded
    correctly. Please make sure that you can read
    the images first.

3) I will strongly recommend you to try first
    experimenting with resampling the PET image
    using a VersorRigid3DTransorm using as output
    the region, orign and pixel size of the CT
    image.  Use the ResampleImageFilter examples
    as a guide. You will find them in

          Insight/Examples/Filtering

    This is equivalent to "manually" try to
    register both images.  Once you are familiar
    with the parameters of the transform you will
    be in a better position to interpret the result
    of the registration and to steer its evolution.

4) Make sure that you fully understand the
    resampling chapter before you attempt any
    registration. Most confusions with registration
    are the consequence of lack of familiarity with
    the way resampling is performed in ITK.

5) Before attempting registration with your own
    data, make sure that you succed first registering
    some of the standard dataset that we made available
    on the FTP site. For example the brainweb images.

    You should actually start with the 2D images in
    Insight/Examples/Data and running all the registration
    examples in Insight/Examples/Registration.

6) You may find useful too to look at the nice tutorial
    material in Registration that Dr. Lydia Ng prepared
    for the ITK Course presented at IEEE Viz and SPIE
    Medical Imaging.

   http://www.itk.org/CourseWare/Training/RegistrationMethodsOverview.pdf




Regards,



     Luis



---------------------------------
soumend at magnum.barc.ernet.in wrote:

> hi!!!!!
> 
> As I told u before I am trying to register two dicom serieses(one CT and one 
> PET). What I want to do is register one CT slice with one PET slice by 
> considering all the PET slices in the process. But the problem is I am not 
> clear about the registartion process. I have read the software guide a 
> lot....but still. Will u help me out by explaing the registratioin process in 
> pixel level that is how it all works with pixels. what I need is an example. 
> 
> Another qs....it may be due to lack of my knowledge.....
> 
> My CT and PET images have different origin and pixel spacing and slice 
> thickness...is it necessary to make these things same for the two images 
> before registration. If yes then how to do that?
> 
> I have registered a CT slice with a PET slice but the I could not interprate 
> the resulted image. May be a clear understanding of the registration process 
> wil bail me out.Specially how Image origin and spacing taken in physical 
> copordinate comes into play.  
> 
> I appreciate ur help.
>     
> 
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> 
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