Figure 19. Processing of spiral CT scan data of patient with esophageal cancer in preparation for virtual endoscopy. Upper right panel shows volume rendering of segmented objects, including skin (brown), lungs (blue), trachea (yellow), esophagus (green), stomach (orange), cancer (red) and location of four selected CT cross-sections shown at upper left. Lower panels show successive removal of anatomic structures to isolate the esophagus and cancer. Note that the cancer (red) severely constricts the esophagus, precluding segmentation of its connection to the stomach. (Scan data courtesy of Dr. Charlene Prather, Mayo Foundation.)