[Insight-users] LevelsetMotionRegistrationImageFilter

[Kishore Mosaliganti]

To add to the below problem, I initialized the filter with a 0 vector
deformation field. Now, the filter executes with ImageSpacingOn().
However, the metric values with iterations are not influenced by the
ImageSpacingOn option.

This makes me believe the underlying implementation is not using the
image spacings.

Kishore

On Tue, Oct 13, 2009 at 7:13 PM, Kishore Mosaliganti
<kishoreraom at gmail.com> wrote:
> Hi all,
>
> I was using the LevelsetMotionRegistrationImageFilter to register two
> 3D image datasets whose voxels have anisotropic spacing:
>
>  RegistrationFilterType::Pointer filter = RegistrationFilterType::New();
>  CommandIterationUpdate::Pointer observer = CommandIterationUpdate::New();
>  filter->AddObserver( itk::IterationEvent(), observer );
>  filter->SetFixedImage( fixedImage );
>  filter->SetMovingImage( movingImage );
>  filter->SetNumberOfIterations( 50 );
>  filter->SetGradientSmoothingStandardDeviations( 0.1 );
>  filter->UseImageSpacingOn();
>  filter->Update();
>
> The problem is I get a Segmentation fault when I turn on
> UseImageSpacingOn(). Otherwise, the filter executes normally.
>
> I used the debugger and went into the code.
> LevelsetMotionRegistrationImageFilter is a sub-class of
> PDEDeformableRegistrationImageFilter which is a subclass of
> FiniteDifferenceImageFilter. The code failed in the
> FiniteDifferenceImageFilter::GenerateData() method in the following
> lines:
>
> ....
>
> if (this->GetState() == UNINITIALIZED)
>    {
>    // Set the coefficients for the deriviatives
>    double coeffs[TInputImage::ImageDimension];
>    if (m_UseImageSpacing)
>      {
>      for (unsigned int i = 0; i < TInputImage::ImageDimension; i++)
>        {
>        coeffs[i] = 1.0 / this->GetInput()->GetSpacing()[i];
>        }
>      }
>    else
>      {
>      for (unsigned int i = 0; i < TInputImage::ImageDimension; i++)
>        {
>        coeffs[i] = 1.0;
>        }
>      }
>
> .....
>
> When I went to see the state of the input pointer, this->m_Input, it
> is a vector of 3 image pointers. Basically, this->m_Input[1] refers to
> the fixed image and this->m_Input[2] refers to the moving image.
> this->m_Input[0] is NULL. this->m_Input[0] is supposed to contain the
> initial deformation field which is not a prerequisite for running the
> code.
>
> The code in itkPDEDeformableRegistrationImageFilter::SetFixedImage()
> and itkPDEDeformableRegistrationImageFilter::SetMovingImage() call
> this->ProcessObject::SetNthInput( 1, const_cast< FixedImageType * >(
> ptr ) ) and this->ProcessObject::SetNthInput( 2, const_cast<
> FixedImageType * >( ptr ) ) respectively.
>
> This filter derives from
> ImageToImageFilter<TDeformationField,TDeformationField> but the vector
> of inputs have been set as scalar-valued fixed and moving image
> pointers. Also, for the case when the initial deformation field is
> unknown, the FiniteDifferenceFilter is checking for the first input
> which doesn't exist.
>
> I have filed a bug report:
> http://public.kitware.com/Bug/view.php?id=9709
>
>
>
> Thanks,
> Kishore
>