Figure 6. Graph shows total number of screening subjects per year undergoing CT and chest radiography (CXR). Zero indicates baseline screening. As cancers are detected, patients are removed from the screening population. Because of the high sensitivity of CT, the screening population size decreases more rapidly after the baseline examination. In subsequent years, the screening population decreases at a similar rate for both CT and chest radiography. Because the available population is continually decreasing, steady-state behavior is demonstrated by looking at percentages.