typedef itk::DisplacementFieldJacobianDeterminantFilter<VectorFieldType, OutputPixelType, ImageType> JacobianFilterType;
typename VectorFieldType::Pointer vfield = vfield_reader->GetOutput();
typedef itk::DisplacementFieldJacobianDeterminantFilter<VectorFieldType, OutputPixelType, ImageType> JacobianFilterType;
typename VectorFieldType::Pointer vfield = vfield_reader->GetOutput();