[vtkusers] how to display the segmentation result

[xujf]

Hello,vtkusers:
    I use itkimagefastmarchingfilter to implement the segmentation of 3D vloumn.then I passed the itk\'s output to vtk,in my code
I use :ConnectVTKITK.(itkimageexport.GetPointer(),vtkimageimport).
       data=vtkimageimport.GetOutput()
so,I can get the data which is the type of vtkImageData.in order to display the segmentation image,I write my code as follow:
      viewer=vtkImageViewer()
      viewer.SetInput(data)
      viewer.SetColorWindow(255)
      viewer.SetColorLevel(127.5)
      viewer.Render()
however,nothing appear.I don\'t know wheather it is correct to use vtkImageViewer to display the segmentation result.if it is correct,why 
nothing appear?

Best Regards!
xujf