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

[Luis Ibanez]

Hi Sateesh,

The initialization is quite off, the center is
not the expected value and the translation is
also understimated.


-----


Your data sets are:

1) 512x512 pixels with spacing 0.97mm x 0.97mm

    that makes an extent of aprox.:

        496mm x 496mm

2) 128x128 pixels with spacing 3.9mm x 3.9mm

    that make an extent of aprox.:

         499mm x 499mm


IFF the origin of the image is in the (0,0) mm,
we should expect the center to be initialized
around

          250mm  x 250mm

However the CenteredTransformInitializer seems
to be starting the center at:

         70.94mm x 75.74mm

So,... something is wrong here...
and it is unrelated to the registration
process. There seems to be an inconsistency
in your input data.


------


Questions:

1) Is the content of the image centered
    in the  slice ?

    I'm assuming that you have something
    like a brain image and the anatomical
    structures are in the center of the image....
    Is this the case ?

2) Are you using the CentereTransformInitializer
    in Geometry mode or in Center of mass mode ?

3) What are the origin values of the images ?

    Please verify the value of the origin for your
    images. You can do this by printing out the
    values returned by the "GetOrigin()" method in
    the image.

    Look at the SoftwareGuide
    http://www.itk.org/ItkSoftwareGuide.pdf
    Section 4.1.4, pdf-page 30 for details on this.




It is not worth to start the registration
process until you have verified the correct
initialization of the transform....

Please let us know what you find.


Regards,


    Luis



============
cspl wrote:
> Hi Luis,
>    Thanks for ur mail.
>    As u said i am printing the initial transform paramters. I get the
> following values:-
>    [1, 0, 0, 1, 70.4192, 75.7447, -188.845, -146.701]
> 
>    I used "CenteredTransformInitializer" class for initializing the
> CenteredAffineTransform.
>    Even now i get the same error from itk. I tried with different values for
> the paremeters but the error doesn't get any affect.
> 
> Error is:-
>   itk::ExceptionObject (0012FD38)
> Location: "Unknown"
> File:
> G:\NEWITKFILES\NewVersionITK7_4_2003\itksrc\Code\Algorithms\itkMattesMutualI
> nformati
> onImageToImageMetric.txx
> Line: 546
> Description: itk::ERROR:
> MattesMutualInformationImageToImageMetric(00302740): Too many sam
> ples map outside moving image buffer: 52 / 1000
> 
>    Not even one iterations are generated this time also...
> 
>    What else i have to change the parameters...
>    Any estimate of suitable parameters...
> 
>    My data sets are 512x512x1 (0.976562/0.976562 spacing) and 128x128x1
> (3.906250/3.906250 spacing). Image type is short.
> 
>    Please suggest me...
> 
>    Thanks in advance.
> 
> -Regards,
>    Sateesh.
>