[Insight-users] trouble using the bulktransform

[Luis Ibanez]

Hi Erik,


Why are you using a static_cast in ?:


  m_BSplineTransform->SetBulkTransform(
      static_cast<VersorRigid3DTransformType*> (initialTransform));


That static_cast should be necessary.

---

I suspect that the problem is mostly related to
the initialization of the BSpline Transform itself.

Particularly related to the image Direction.


You may want to use the following class:

   Insight/Code/Review/
       itkBSplineDeformableTransformInitializer.h
       itkBSplineDeformableTransformInitializer.txx


That is described in this Insight Journal paper:


"Helper class for initializing the grid parameters of a
 BSpline deformable transform by using an image as reference"
http://www.insight-journal.org/browse/publication/216
http://hdl.handle.net/1926/1338


Note that is simply a complement to the use of the
Bulk Transform, not a replacement for it.



      Regards,



            Luis



-----------------------------------------------------------------------
On Fri, Feb 26, 2010 at 10:42 AM, Erik Türke <tuerke at cbs.mpg.de> wrote:
> Hi!
>
> I am trying to use the SetBulkTransform method of the
> BSplineDeformableTransform.
>
> The two images which i want to register are totally shifted, so i want to
> use a simple translation as the bulk transform.
>
> So what  i am doing is:
>
> m_BSplineTransform->SetBulkTransform(static_cast<VersorRigid3DTransformType*>
> (initialTransform));
>
> If i print out the parameters of the initialTransform with:
>
> std::cout << static_cast<VersorRigid3DTransformType*>
> (initialTransform)->GetParameters() << std::endl;
>
> the output is: [0, 0, 0, 96.2941, 92.5804, 38.6559], what is totally right.
>
> Now i setup the BSplineTransform:
>
>               typedef typename BSplineTransformType::RegionType
> BSplineRegionType;
>               typedef typename BSplineTransformType::SpacingType
> BSplineSpacingType;
>               typedef typename BSplineTransformType::OriginType
> BSplineOriginType;
>               typedef typename BSplineTransformType::DirectionType
> BSplineDirectionType;
>
>               BSplineRegionType bsplineRegion;
>               typename BSplineRegionType::SizeType gridSizeOnImage;
>               typename BSplineRegionType::SizeType gridBorderSize;
>               typename BSplineRegionType::SizeType totalGridSize;
>
>               gridSizeOnImage.Fill(UserOptions.BSplineGridSize);
>               gridBorderSize.Fill(3); //Border for spline order = 3 (1
> lower, 2 upper)
>               totalGridSize = gridSizeOnImage + gridBorderSize;
>
>               bsplineRegion.SetSize(totalGridSize);
>               BSplineSpacingType bsplineSpacing =
> m_FixedImage->GetSpacing();
>
>               BSplineOriginType bsplineOrigin = m_FixedImage->GetOrigin();
>
>               typename FixedImageType::SizeType fixedImageSize =
> m_FixedImage->GetBufferedRegion().GetSize();
>
>               for (unsigned int r = 0; r < FixedImageDimension; r++) {
>                   bsplineSpacing[r] *= static_cast<double>
> (fixedImageSize[r] - 1) / static_cast<double> (gridSizeOnImage[r]
>                           - 1);
>               }
>
>               BSplineDirectionType bsplineDirection =
> m_FixedImage->GetDirection();
>               BSplineSpacingType gridOriginOffset = bsplineDirection *
> bsplineSpacing;
>
>               bsplineOrigin = bsplineOrigin - gridOriginOffset;
>
>               m_BSplineTransform->SetGridSpacing(bsplineSpacing);
>               m_BSplineTransform->SetGridOrigin(bsplineOrigin);
>               m_BSplineTransform->SetGridRegion(bsplineRegion);
>               m_BSplineTransform->SetGridDirection(bsplineDirection);
>
>               typedef typename BSplineTransformType::ParametersType
> BSplineParametersType;
>
>               m_NumberOfParameters =
> m_BSplineTransform->GetNumberOfParameters();
>
>               BSplineParametersType bsplineParameters(m_NumberOfParameters);
>               bsplineParameters.Fill(0.0);
>
> m_BSplineTransform->SetParameters(bsplineParameters);
>
> m_RegistrationObject->SetInitialTransformParameters(m_BSplineTransform->GetParameters());
>       If i now start the registration with 1 iteration, the result is
> totally shifted again.
> I am sure, the initial transform is right, because i got those values by
> using the itk initializer class and tested the values as the initial
> parameters of a VersorRigid3DTransform with iterations= 0 as well.
> With the VersorRigid3DTransform, the images are aligned.
> Why is the bulktransform not working here?
>
> I becoming a little desperate now :-( . Can somebody give me a hint?
>
> Thanks!
>
>
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