message: BUG: Fix attenuation correction in zengBackProjectionImageFilter
  There was a mismatch between the slice of the backprojected volume and
  the slice of the attenuation map used for the attenuation correction.
diff: @@ -386,21 +386,22 @@ ZengBackProjectionImageFilter<TInputImage, TOutputImage>::GenerateData()
  currentVolume = m_PasteImageFilter->GetOutput();
  currentVolume->DisconnectPipeline();
  m_PasteImageFilter->SetDestinationImage(currentVolume);
  +
  + int index = 0;
  + for (index = startSlice; index > 0; index--)
  + {
  if (!this->GetInput(2))
  {
  m_DiscreteGaussianFilter->SetInput(currentSlice);
  }
  else
  {
  - desiredRegion.SetIndex(Dimension - 1, startSlice - 1);
  + desiredRegion.SetIndex(Dimension - 1, index - 1);
  m_AttenuationMapRegionOfInterest->SetRegionOfInterest(desiredRegion);
  m_AttenuationMapRegionOfInterest->UpdateOutputInformation();
  m_AttenuationMapMultiplyImageFilter->SetInput1(currentSlice);
  m_DiscreteGaussianFilter->SetInput(m_AttenuationMapMultiplyImageFilter->GetOutput());
  }
  - int index = 0;
  - for (index = startSlice; index > 0; index--)
  - {
  // Compute the distance between the current slice and the detector
  indexSlice[Dimension - 1] = index - 1;
  dist += m_ConstantVolumeSource->GetSpacing()[2];
  @@ -420,18 +421,6 @@ ZengBackProjectionImageFilter<TInputImage, TOutputImage>::GenerateData()
  currentVolume = m_PasteImageFilter->GetOutput();
  currentVolume->DisconnectPipeline();
  m_PasteImageFilter->SetDestinationImage(currentVolume);
  - if (!this->GetInput(2))
  - {
  - m_DiscreteGaussianFilter->SetInput(currentSlice);
  - }
  - else
  - {
  - desiredRegion.SetIndex(Dimension - 1, index - 1);
  - m_AttenuationMapRegionOfInterest->SetRegionOfInterest(desiredRegion);
  - m_AttenuationMapRegionOfInterest->UpdateOutputInformation();
  - m_AttenuationMapMultiplyImageFilter->SetInput1(currentSlice);
  - m_DiscreteGaussianFilter->SetInput(m_AttenuationMapMultiplyImageFilter->GetOutput());
  - }
  }
  // Rotate the volume
  m_ResampleImageFilter->SetInput(currentVolume);
  