Illustration of the developed computational geometry solution for identifying intrapulmonary vessels. (a) a CT scan, (b) the 3-D surface model of the local region as indicated by the box in (a), (c) the local enlargement of the surface model in (b), (d) the surface model after the application of the Laplacian smoothing, (e) the local enlargement of the surface model in (d), (f) the surface model after filtering the triangles based on the principal curvature analyses, (g) the filtered surface model, (h) the surface model after picking up the small patches from (g), and (i) the final filtered surface model after the pick-up operation.