Problem with VMTK for vessel segmentation

Hi, I am new to VMTK and I tried to follow the tutorial on https://na-mic.org/w/images/archive/4/40/20100107165806!TutorialVMTKCoronariesCenterlinesMRI_Winter2010AHM.pdf, but the version they were using was too old and I could not get it work.

Here is what I did:
image
I was using the sample data provided on Slicer

image
Here is where the problem comes from. No matter how I change the parameters, I cant get the picture shown in the tutorial.


I was still using what I got from step 2. But it usually tuned out to be a random shape or nothing.

Any idea?