[Insight-users] Problem on PET-CT Registration - Help Needed!!!

[Luis Ibanez]

Hi Cspl,

1) Did you plug an Observer to your registration ?

    Are you printing out values of the transform
    parameters as the registration progesses ?

    Tracking the evolution of the transform will
    give you the indications you need for tunning
    parameters.

2) Whenever you get the exception regarding the
    low number of samples, it simply means that
    the overlap between the two images is too small.

    In other words, that the transform parameters
    diverged and the current transform is mapping the
    image too far from the expected position.

    The action to take in this case is to track how
    long it took for the transfrom to diverge. For
    this you need to solve (1) [add an observer and
    print out the transform parameters].


3) There is no point in using multiresolution if you
    dont set the shrinking parameters. You could in
    that case simply use a normal registration with
    more iterations.


Please add an observer to the registration and track
the evolution of the transform. You may want to take
a look at the examples in

      Insight/Examples/Registration/


Note that there are also Tcl versions for some of them.


   Regards,


     Luis


----------------------
cspl wrote:
> Hi Luis and all,
>    Well back with the registration problem again.
>    Let me explain my problem.
>    I am using PET and CT images as input to registration. PET as fixed and
> CT as moving images. Total number of images are 35 in each set. So my data
> sets are 128x128x35 for PET and 512x512x35 for CT.
> Pixel spacing for CT images are 0.976562\0.976562 and for PET images are
> 3.906250\3.906250.
> Now the parameters for registration are
>   No. of iterations: 150
>   Translate Scale : 10000
>   Optimizer Scale : 1
>   Max Step Length : 4
>   Min Step Length : 0.01
>   Spatial Samples : 1000
>   Bins : 50
>   No. of levels : 5
>   I am not using any shrinking factors in the registration. SetMinimize()
> method is used in registration process.
> 
>   The above setting are working for other data sets like mri-mri
> registration.
>   These parameters are working for single slice of above data set i.e. if i
> give 1 PET as fixed and 1 CT as moving image with the above parameters and
> perform registration it is working good with out any itk error.
> 
>   But if i give 35 slices it is giving the following error message:-
>          itk::ERROR:MattesMutualInformationImageToImageMetic(01A93ED0): Two
> many samples map outside moving image buffer: 0/1000.
> 
>   I have tried with different values for the above parameters but still this
> error is generated.
> 
>   If u have any idea of parameters for these data sets please suggest me.
> 
>   Please help me in this regard.
> 
>   Thanks in advance.
> 
> -Regards,
>     Sateesh.
> 
> 
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