Figure 2. 63-year-old man with lung cancer. (a) Current CT image shows several pulmonary nodules in the left upper lung. (b) Temporal subtraction image shows new appearance of mucoid impaction in a bronchus (arrow) of the left upper lung, which is depicted as a bright area. (c) Warped previous CT image (the extrapulmonary compartment is excluded). (d) Original previous CT image.