All radiographic examinations were performed using digital radiographic equipment (TDR4600-F80; Gold Mountain Medical System, Seoul, Korea) and a standardized technique (110 kV, 2 mAs, and a 180-cm film-focus distance for the posteroanterior views). Thin-section CTs of the thorax were performed using a 16 channel CT scanner (BrightSpeed; GE Medical Systems, WI), with the following parameters: 1.25 mm slice thickness with a 2.5 mm gap, supine position, scanning during inspiration, 6 seconds scan time, 120kV, auto mA.