Figure 13b.

Example of a limitation of shape-based methods of lung segmentation. Because shape-based segmentation approaches assume a certain anatomic structure for the lungs, pathologic lungs with certain shape changes can be mis-segmented. In a severe case of scoliosis, although region- and thresholding-based methods performed well (b), a failure is observed with the shape-based method (a), with the boundary of the right lung (green contour) extending over the spine (arrow at left) and with the left lung boundary (green contour) spanning the medial left upper portion of the abdomen (arrow at right).