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

[cspl]

Hi Lius,
   Thanks for ur reply.
   As u said i added an Observer and tested the registration code. This time
i started with a 2d images. My inputs are one CT (512x512x1) as fixed and
one PET (128x128x1) to the registrations application. Both pixel type is of
short. Pixel spacing of CT is 0.976562\0.976562 and of PET image is
3.906250\3.906250.

   When i run the application, it is not performing atleast one iteration
and it generates a itk error same as before.

itk::ExceptionObject (0012FC2C)
Location: "Unknown"
File:
G:\NEWITKFILES\NewVersionITK7_4_2003\itksrc\Code\Algorithms\itkMattesMutualI
nformati
onImageToImageMetric.txx
Line: 546
Description: itk::ERROR:
MattesMutualInformationImageToImageMetric(00302050): Too many sam
ples map outside moving image buffer: 0 / 1000

   I used the following settings:-
   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 using "CenteredAffineTransform" for transformation. For this i am
shifting the origin to the image center for both the images.

   I added shrinking factor of 4 for both the images but no change in the
output.

   What could be the problem???  Is this because of the great change in the
image dimensions?? But when we find the image dimensions in terms of
millimeters we get almost same dimensions of both of images  (image
dimensions x pixel spacing). In this case both are of same size. Then what
could be the problem.

   I could not able to find a proper values for registration parameters.

   Please suggest some settings for it.

   Thanks in advance.

-Regards,
   Sateesh.

----- Original Message -----
From: "Luis Ibanez" <luis.ibanez@kitware.com>
To: "cspl" <affable@hd2.dot.net.in>
Cc: <insight-users@public.kitware.com>
Sent: Thursday, April 17, 2003 08:45 PM
Subject: Re: [Insight-users] Problem on PET-CT Registration - Help Needed!!!


> 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.
> >
> >
> > _______________________________________________
> > Insight-users mailing list
> > Insight-users@public.kitware.com
> > http://public.kitware.com/mailman/listinfo/insight-users
> >
>
>
>
>