Lung segmentation with LungCTSegmenter

Dear rbumm,

After testing with numerous dataSets, I found that the dataSet from slicer in built demoChest CT produce the best results:

However, if I tried to use my own datasets obtained from:
https://nbia.cancerimagingarchive.net/nbia-search/?MinNumberOfStudiesCriteria=1&CollectionCriteria=Lung-PET-CT-Dx
I cant clearly show the airway segmentations:


I have also used the grow from seeds function to try to obtain better results but the result is shown above,

I have tried 3 different samples :
and the results are more or less the same:
image

Do you think what are the possible problems?
Do I need to do a little bit of preprocessing like resampling on the DICOM data before segmentation?

Thank you.