I am new to itk. I need to do vessel segmentation using itk. I didn't get why SetAplha1 and SetAlpha2 is used in itk Hessian3DToVesselnessMeasureImageFilter ? What is the role of this?
using HessianFilterType = itk::HessianRecursiveGaussianImageFilter<ImageType>;
HessianFilterType::Pointer hessianFilter = HessianFilterType::New();
hessianFilter->SetInput(filter_toitkimage->GetOutput());
hessianFilter->SetSigma(1.0);//does this will determine the spacing between each dicom image slices?
using VesselnessMeasureFilterType = itk::Hessian3DToVesselnessMeasureImageFilter<PixelType>;
VesselnessMeasureFilterType::Pointer vesselnessFilter = VesselnessMeasureFilterType::New();
vesselnessFilter->SetInput(hessianFilter->GetOutput());
vesselnessFilter->SetAlpha1(0.5);
vesselnessFilter->SetAlpha2(2.0);
Sigma determines the scale of features. For example, a sigma of 1.0 will work on vessels about 2-3 mm in diameter, whereas a sigma of 5.0 will work best on vessels 10-15 mm in diameter (think aorta, vena cava).
Regarding the Alpha parameters, the documentation says to see its description in the authors' paper.