[ITK-users] image registration in MATALAB vs ITK.

[shrikant]

Hi,

I am new to ITK, i have working MATLAB registration as a below code. Please
note that here I am registering fixed image with high features and moving
image with very low signal.

[optimizer,metric]=imregconfig('multimodal');
tr1 = imregtform(movingImage, fixedImageResized, 'translation', optimizer,
metric);

I need to convert into ITK 4 code. I am using below ITK code 
  
  typedef itk::ImageRegistrationMethodv4<ITKImageType, ITKImageType,
TransformType> RegistrationType;
  RegistrationType::Pointer registration = RegistrationType::New();
  RegistrationType::ShrinkFactorsArrayType shrinkFactorsPerLevel;
  RegistrationType::SmoothingSigmasArrayType smoothingSigmasPerLevel;
  MetricType::Pointer metric = MetricType::New();

  metric->SetNumberOfHistogramBins(50);
  metric->SetUseMovingImageGradientFilter(true);
  metric->SetUseFixedImageGradientFilter(true);
  registration->SetMetric(metric);


  RSGDOptimizerType::Pointer smartOptimizer = RSGDOptimizerType::New();
  smartOptimizer->SetLearningRate(0.5);
  smartOptimizer->SetMaximumStepSizeInPhysicalUnits(0.001);
  smartOptimizer->SetMinimumStepLength(0.0001);
  smartOptimizer->SetNumberOfIterations(100);
  smartOptimizer->ReturnBestParametersAndValueOn();
  smartOptimizer->SetRelaxationFactor(0.5);
  registration->SetOptimizer(smartOptimizer);


  registration->SetNumberOfLevels(1);

  shrinkFactorsPerLevel.SetSize(1);
  shrinkFactorsPerLevel[0] = 1;
  registration->SetShrinkFactorsPerLevel(shrinkFactorsPerLevel);
  smoothingSigmasPerLevel.SetSize(1);
  smoothingSigmasPerLevel[0] = 0;
  registration->SetSmoothingSigmasPerLevel(smoothingSigmasPerLevel);


  registration->SetMetricSamplingStrategy(RegistrationType::REGULAR);
  registration->SetMetricSamplingPercentage(100);

  registration->Update();

  TransformType::ParametersType finalParameters =  
registration->GetOutput()->Get()->GetParameters();
  yTranslation = finalParameters[1];

Here I am getting huge differences like, -0.33 (ITK) vs -1.20(MATLAB) mm. If
I see visually then matlab results look more correct.

Any idea what is going wrong here?

Any help would be highly appreciated.




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