Problem with VMTK for vessel segmentation

Hi, I am new to VMTK and I tried to follow the tutorial on!TutorialVMTKCoronariesCenterlinesMRI_Winter2010AHM.pdf, but the version they were using was too old and I could not get it work.

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

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?