[Rtk-users] Error Result by using FDK algorithm to Reconstruction 2D X- ray Scan projection images into 2D CT Slice image

[Simon Rit]

Hi,
I'm not sure I have enough information to answer... What I can say is:
- that the origin is not set to center your volume, for centering, you
should use (size-1)*0.5*spacing
- if you're doing 2D reconstruction, be careful that your projections
should not be 1D because the backprojection uses a 2D interpolation. It
should have at least 2 lines.
I hope it helps,
Simon

On Thu, Jan 12, 2023 at 8:46 AM 何明哲 <m10512067 at yuntech.org.tw> wrote:

>
> HI Everyone ,
>
> I have a question
> that When I was refer to the official example
> "Firstcudareconstruction.cpp",
> then I tried to  modify the code and reconstruction 2D x ray projection
> image to 2D ct slice,
> the code is worked but I got the wrong result too,
> I don't understand what the problem I'm have ?
>  it's possible that the setting of reconstruction output image size or
> origin is wrong?
>
> here is my code and result (I was tried to only reconstruction just a
> slice NO.100 of the whole volume)
>
>  --------------------------------------------------------------------------------------------
>  using GeometryType = rtk::ThreeDCircularProjectionGeometry;
>   GeometryType::Pointer geometry = GeometryType::New();
>   unsigned int          numberOfProjections = 280;
>   double                firstAngle = 0;
>   double                angularArc = 280;
>   unsigned int          sid = 510;
>   unsigned int          sdd = 690;
>
>   for (unsigned int noProj = 0; noProj < numberOfProjections; noProj++)
>   {
>     double angle = firstAngle + noProj * angularArc / numberOfProjections;
>     geometry->AddProjection(sid, sdd, angle);
>   }
>
>   rtk::ThreeDCircularProjectionGeometryXMLFileWriter::Pointer xmlWriter;
>   xmlWriter = rtk::ThreeDCircularProjectionGeometryXMLFileWriter::New();
>   xmlWriter->SetFilename(".\\RTK_Geometry.xml");
>   xmlWriter->SetObject(geometry);
>   xmlWriter->WriteFile();
>
>   using NameGeneratorType = itk::NumericSeriesFileNames;
>   NameGeneratorType::Pointer nameGenerator = NameGeneratorType::New();
>
>   nameGenerator->SetSeriesFormat(ProjectionInage +"\\%d.tif");
>   nameGenerator->SetStartIndex(1);
>   nameGenerator->SetEndIndex(280);
>   nameGenerator->SetIncrementIndex(1);
>
>   using IutputImageType = itk::CudaImage<float, 3>;
>   using ReaderType = rtk::ProjectionsReader<IutputImageType>;
>   ReaderType::Pointer reader = ReaderType::New();
>   reader->SetFileNames(nameGenerator->GetFileNames());
>   reader->Update();
>
>   using ConstantImageSourceType =
> rtk::ConstantImageSource<OutputImageType>;
>   ConstantImageSourceType::PointType   origin;
>   ConstantImageSourceType::SpacingType spacing;
>   ConstantImageSourceType::SizeType    sizeOutput;
>   ConstantImageSourceType::Pointer     recoVolume =
> ConstantImageSourceType::New();
>
>   sizeOutput[0] = Imagewidth;
>   sizeOutput[1] = Imageheigh;
>   sizeOutput[2] = numofproj;
>   spacing[0] = 0.25;
>   spacing[1] = 0.25;
>   spacing[2] = 0.25;
>   origin[0] = Imagewidth*spacing[0]*0.5*-1;
>   origin[1] = Imageheigh*spacing[0]*0.5*-1;
>   origin[2] = spacing[2]*SliceN*-1;
>
>   recoVolume->SetSize(sizeOutput);
>   recoVolume->SetSpacing(spacing);
>   recoVolume->SetOrigin(origin);
>   recoVolume->SetConstant(0);
>
>   using FDKGPUType = rtk::CudaFDKConeBeamReconstructionFilter;
>   FDKGPUType::Pointer feldkamp = FDKGPUType::New();
>
>   feldkamp->SetInput(0, recoVolume->GetOutput());
>   feldkamp->SetInput(1, reader->GetOutput());
>   feldkamp->SetGeometry(geometry);
>   feldkamp->SetNumberOfThreads(7);
>   feldkamp->Update();
>
>   using WriterType = itk::ImageFileWriter<OutputImageType>;
>   WriterType::Pointer writer = WriterType::New();
>   writer->SetFileName("C:\\RTK.mhd");
>   writer->SetInput(feldkamp->GetOutput());
>   writer->Update();
>
> [image: 20230112_100.PNG]
>
> it should be look like this
> [image: 20230109.PNG]
>
> thanks for your reply
>
> BR,
>
>
>
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