[Insight-users] Inverse BSplineDeformableTransform

[Vincent A. Magnotta]

Lars,

The coefficient image contains the parameters for the BSpline transform
and is not the deformation field. You will need to create a deformation
field by iterating over the fixed image space and computing the change
in position to generate a deformation field. You can then use this
deformation field in the inverse calculation.

Vince


On Tue, 2007-12-18 at 07:44 -0800, Lars Nygard wrote:
> Hi vincent,
> Thanks for your mail. Im trying your first suggestion by using
> the InverseDeformationFieldImageFilter and by studying example
> DeformableRegistration6.cxx. However Im getting an error:
> 
> ------------------------------------------------------------------------------------------------------
> C:\Insight\myPrograms\MultiResolutionReg\liImageRegistrationConsoleBase.cxx:407:   instantiated from
>  here
> C:/Insight/myPrograms/MultiResolutionReg/itkInverseDeformationFieldImageFilter.h:105: error: `double
> ' is not a class, struct, or union type
> -----------------------------------------------------------------------------------------------------
> 
> I think this has something to do with the fact that Im feeding the InverseFilter with a 
> scalar image but Im not sure. 
> My code is below. Do you know how to get the vector deformation
> image from the BSplineTransform?? Thanks for any advice.
>  
> ---------------------------------
>   unsigned int counter = 0;
> 
>     for ( unsigned int k = 0; k < 3; k++ )
>     {
>     typedef BSplineTransformType::ImageType ParametersImageType;
>     const typedef itk::ResampleImageFilter<ParametersImageType,ParametersImageType> ResamplerType;
>     ResamplerType::Pointer inversesampler = ResamplerType::New();
> 
>     typedef itk::BSplineResampleImageFunction<ParametersImageType,double> FunctionType;
>     FunctionType::Pointer function = FunctionType::New();
> 
>     typedef itk::IdentityTransform<double,3> IdentityTransformType;
>     IdentityTransformType::Pointer identity = IdentityTransformType::New();
> 
> 
>     typedef itk::InverseDeformationFieldImageFilter<ParametersImageType,ParametersImageType> InverseDeformationFieldFilterType;
>     InverseDeformationFieldFilterType::Pointer inversedeformfilter = InverseDeformationFieldFilterType::New();
> 
>     
>     inversesampler->SetInput( m_BSplineTransform->GetCoefficientImage()[k] );
>     inversesampler->SetInterpolator( function );
>     inversesampler->SetTransform( identity );
>     inversesampler->SetSize( m_BSplineTransform->GetGridRegion().GetSize() );
>     inversesampler->SetOutputSpacing( m_BSplineTransform->GetGridSpacing() );
>     inversesampler->SetOutputOrigin( m_BSplineTransform->GetGridOrigin() );
> 
>     typedef itk::BSplineDecompositionImageFilter<ParametersImageType,ParametersImageType>
>       DecompositionType;
>     DecompositionType::Pointer decomposition = DecompositionType::New();
> 
>     decomposition->SetSplineOrder( 3 );
>     decomposition->SetInput( inversesampler->GetOutput() );
>     inversedeformfilter->SetInput(decomposition->GetOutput());
>     inversedeformfilter->Update();
> 
>     ParametersImageType::Pointer newCoefficients = inversedeformfilter->GetOutput();
> 
>     // copy the coefficients into the parameter array
>     typedef itk::ImageRegionIterator<ParametersImageType> Iterator;
>     Iterator it( newCoefficients, m_InverseBSplineTransform->GetGridRegion() );
>     while ( !it.IsAtEnd() )
>       {
>       parametersInverse[ counter++ ] = it.Get();
>       ++it;
>       }
> 
>     }
>   
>   m_InverseBSplineTransform->SetParameters( parametersInverse );
> 
> ----- Original Message ----
> From: Vincent A. Magnotta <vincent-magnotta at uiowa.edu>
> To: Lars Nygard <lnygard at yahoo.com>
> Cc: insight-users at itk.org
> Sent: Tuesday, December 18, 2007 6:14:22 AM
> Subject: Re: [Insight-users] Inverse BSplineDeformableTransform
> 
> Lars,
> 
> The GetInverse Method is not implemented for the BSpline transform.
> There are two solutions for generating the inverse. The first is to get
> the deformation field from the transform and then invert the
>  deformation
> field using the InverseDeformationFieldImageFilter. Another solution is
> to generate a regular sampling of points in the fixed image space and
> map these back to the moving image space using the BSpline transform.
> These points can then be used to create a Thin plate spline transform
> that is an approximation to the inverse of the BSpline transform.
> 
> Vince
> 
> 
> On Sun, 2007-12-16 at 15:09 -0800, Lars Nygard wrote:
> > hi everybody,
> > 
> > Im trying to get the inverse transformation of a BSpline
> > transform to map points from the fixed atlas to an 
> > image. Im trying the GetInverse metdod but this doesnt
> > work. The point doesnt change. 
> > Anybody can help me with this.
> > thanks,
> > lars
> > 
> > 
> > 
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-- 
Assistant Professor
Department of Radiology
0453-D JCP
200 Hawkins Drive
Iowa City, IA 52242
E-mail: vincent-magnotta at uiowa.edu
Phone: 319-356-8255
Fax: 319-353-6275
Website: http://www.radiology.uiowa.edu