[Insight-users] Crash when using multi-grid BSpline transform in the framework of multi-resolution image registration

[lien lee]

Hi all,

I am trying to do BSpline transform with multi-resolution image
registration, but I got some trouble on how to configure the itk::
BSplineDeformableTransform<double,3,3> object when moving from one
resolution level to the next.  Through google-search, I can not find any
clear solution for this. ITK does have an example with multi-grid BSpline
transform, but it is not in the framework of multi-resolution image
registration.

I tried the stuff of GridScheduleComputer and
UpsampleBSplineParametersFilter found in ITK-journal based on ITK's
multi-resolution image registration example.  Unfortunately, I got a crash
when proceeding from resolution level 0 to level 1.  What I did is
something like this:

//===================================================================================
void
RegistrationInterfaceCommand::Execute(itk::Object * object,
    const itk::EventObject & event)
{
....

    if (Registration->GetCurrentLevel() != 0)
    {
        Optimizer->SetMaximumStepLength( Optimizer->GetMaximumStepLength()
/ 4.0 );
        Optimizer->SetMinimumStepLength( Optimizer->GetMinimumStepLength()
/ 10.0 );
        Optimizer->SetNumberOfIterations( 100 );
        Optimizer->SetRelaxationFactor( 0.7 );


        typedef
itk::UpsampleBSplineParametersFilter<TransformType::ParametersType,
TransformType::ImageType>
            GridUpsamplerType;

        GridUpsamplerType::Pointer Upsampler = GridUpsamplerType::New();
        Upsampler->SetCurrentGridOrigin(Transform->GetGridOrigin());
        Upsampler->SetCurrentGridSpacing(Transform->GetGridSpacing());
        Upsampler->SetCurrentGridRegion(Transform->GetGridRegion());

        TransformType::OriginType    NewOrigin;
        TransformType::SpacingType    NewSpacing;
        TransformType::RegionType    NewRegion;
        mGridScheduleComputer->GetBSplineGrid(vLevel, NewRegion,
NewSpacing, NewOrigin);

        Upsampler->SetRequiredGridOrigin(NewOrigin);
        Upsampler->SetRequiredGridSpacing(NewSpacing);
        Upsampler->SetRequiredGridRegion(NewRegion);

        TransformType::ParametersType Parameters =
Registration->GetLastTransformParameters();
        TransformType::ParametersType NewParameters;
        Upsampler->UpsampleParameters(Parameters, NewParameters);

        Transform->SetGridOrigin(NewOrigin);
        Transform->SetGridSpacing(NewSpacing);
        Transform->SetGridRegion(NewRegion);
        Transform->SetParameters(NewParameters);

        {
            std::cout << "Parameters: " <<
Transform->GetNumberOfParameters() << std::endl;
            std::cout << "Full transform description ";
            Transform->Print( std::cout );
        }


Registration->SetInitialTransformParameters(Transform->GetParameters());

Registration->SetInitialTransformParametersOfNextLevel(NewParameters);
        unsigned int NumberOfParameters =
Transform->GetNumberOfParameters();

        const unsigned long NumberOfSamples =
            static_cast<unsigned long>(
            vcl_sqrt( static_cast<double>( NumberOfParameters ) *
            static_cast<double>(
Registration->GetFixedImage()->GetLargestPossibleRegion().GetNumberOfPixels()
) ) );
        Metric->SetNumberOfSpatialSamples( NumberOfSamples );

        OptimizerType::ScalesType OptimizerScales =
OptimizerType::ScalesType( NumberOfParameters );
        OptimizerScales.Fill( 1.0 );
        Optimizer->SetScales( OptimizerScales );
    }
....
}
//===================================================================================

I debugged into the code.  I found that when proceeding from level 0 to
level 1, an exception was caught as:


"
ExceptionObject caught!

itk::ExceptionObject (000000000000B6D6A0)
location: "void __cdecl itkLLBSplineBaseTransform<double, 3,
3>::SetParameters(const calss itk::OptimizerParameters<double> &)"
File: d\projects\itk\insighttoolkit-4.1.0\modules\core\transform\include
itkBSplineBaseTransform.hxx
Line 92
Description: itk::ERROR: BSplineDeformableTransform (00000000004595520):
Mismatch between parameters size 3435973826 and expected number of
parameters 5070
"

Am I wrong somewhere? I am working with ITK4.1 in Visual Studio 2010.  Or,
could you please point me any direction?  Any comments will be appreciated
by the ITK newbie, me. Thanks!
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