Wanted to use vtkImageData type data input, in place of vtkMRMLScalarVolumeNode/vtkMRMLSegmentationNode type input in lungCt analyzer code

recently I was going through the code

and i wanted to know how will i use vtkImageData type data input, in place of vtkMRMLScalarVolumeNode/vtkMRMLSegmentationNode type input in lungCt analyzer code while inputting input CT volume and segmentation volume. Please help