python vtk volume rendering dicom images

I try to write a python code with vtk to volume render dicom images but as i get no error in my code the window is only back can anyone pls give some guidelines on what to do? I am new with vtk!!

My code:
import vtk

path = “C:/Users/UserPC/Desktop/temp”

reader = vtk.vtkDICOMImageReader()
reader.SetDirectoryName(path)
reader.SetDataSpacing(1, 1, 1)
reader.Update()

volumeMapper = vtk.vtkFixedPointVolumeRayCastMapper()
volumeMapper.SetInputConnection(reader.GetOutputPort())
volumeMapper.SetBlendModeToMaximumIntensity()

volume = vtk.vtkVolume()
volume.SetMapper(volumeMapper)
ren = vtk.vtkRenderer()
ren.AddVolume(volume)

renWin = vtk.vtkRenderWindow()
renWin.AddRenderer(ren)
renWin.SetSize(900, 900)

interactor = vtk.vtkRenderWindowInteractor()
interactor.SetRenderWindow(renWin)

interactor.Initialize()
renWin.Render()
interactor.Start()

There are many medical image volume rendering examples in the VTK examples site. You can start from any of them and change input image and transfer functions step by step, testing the output after each change.

Since transfer functions can be best created based on visual feedback (adjust the functions until they look good), I would recommend to first use volume rendering GUI of 3D Slicer (for medical imaging) or ParaView (for general engineering applications). You can then use the same transfer functions in a standalone VTK script.

Thank you very much for the help