Figure 2. Flowchart of the automatic vessel extraction algorithm.

(top) Sample CT image, (2^nd row) lung, airway segmentation and the vessel enhancement filter response superimposed on the CT image, (3^rd row) vessel enhancement filter response restricted to the region of interest, (bottom row, left) connected centerlines, (bottom row, right) 3D rendering of the lung vessel centerlines. Inset shows the computation of distance metric (DM). The sum of distances along the 3D points of the vessel is divided by the length of the straight path between the two endpoints (first and last 3D point of the vessel segment).