[Insight-users] Problems with example ImageRegistration8

[Luis Ibanez]

Hi Aneta,

Thanks for confirming that the feature of the output image
that makes you consider it to be incorrect are the gray
areas resulting from mapping pixels of the fixed image
that fall outside of the moving image.

As we explained in the previous email, these gray areas
are normal. The pixel value of these areas is defined by
calling the SetDefaultPixelValue() method in the image
resampling filter. In the cased of ImageRegistration8,
this value is set to 100, on purpose, because we wanted
to make those regions clearly visible, with the intention
of pointing out that some regions of the fixed image will
be mapped outside of the moving image.

What we usually recommend is that you first resample the
image using a value like the one in the example, so you
clearly see where the image is being mapped.  Once you
are aware of the mapping, then you may want to change
the value and rerun the program. This time, the value that
you may want to select is one close to the background of
your image.  In this way, the image will present a more
normal appearance.

The selection of this value is particularly important if
you plan to do analysis in the resampled image.

For example,

If you plan to run a segmentation method, or an edge
detection method. Then the choice of that default
pixel value is quite important.

If you are visualizing the image using volume rendering,
it is also a good idea to use a default pixel value
close to the values of the background.


Please let us know if you have other questions,



     Thanks



        Luis


---------------------
Markova Aneta wrote:
> Hello Luis,
> 
> Thank you very much for the explanation.
> 
> 
>>About the output volume not being generated correctly:
> 
> 
>>Could you describe more precisely what do you see in
>>the resampled volume that make you think it is computed
>>incorrectly ?
> 
> 
>>By looking at the resampled volume that I get here,
>>the only thing that may look like a problem to you
>>is the fact that there are gray areas around the image.
>>This is normal, and is caused by the projection of the
>>fixed image grid to fall outside of the moving image
>>grid in some sections.
> 
> 
> I am using VTK to visualize the output volume. What bother me are those
> gray areas. As it seems from your explanation I don't do the
> visualization correctly. Could you please give me a hint if there is a
> way how to visualize the volumes without those gray areas? 
> 
> Below is the part of the code for visualization of the volumes. 
> 
> 
> Thank you very much,
> Aneta
> 
> __________________________________________________________
> m_readerOutput->SetFileName( "D:\\Data\\Output.mhd" );
> m_connectorOutput->SetInput( m_readerOutput->GetOutput() );		
> 	
> vtkImageViewer *viewer = vtkImageViewer::New();	
> vtkRenderWindowInteractor *renderWindowInteractor =
> vtkRenderWindowInteractor::New();	
> 
> viewer->SetupInteractor ( renderWindowInteractor );			
> viewer->SetInput ( m_connectorOutput->GetOutput() );			
> viewer->Render();
> 
> viewer->SetColorWindow( 255 );						
> viewer->SetColorLevel ( 128 );						
> viewer->GetRenderWindow()->SetWindowName("Output Image");
> renderWindowInteractor->Start();
> 
> 
> 
> 
> 
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