Figure 7.

An example to illustrate the challenge of tracing the lung arteries and veins. (a) the 3-D surface model of the lung vessels in a local region, (b) the local enlargement of the region as indicated by the box in (a), (c) the skeletons of the vessel branches in (a) and each skeleton indicates a vessel branch, and (d) the highlight of the two skeletons (i.e., A and B) associated with the challenge of vessel tracing. Arrow C illustrated a disconnected branch as the result of skeletonization. In (c), “1”–”6” indicated four different branches.