[Screening CT of the lungs: image quality compared with conventional CT]

More sensitive imaging methods may be required in the screening of early peripheral lung cancer. Among new radiologic techniques, helical volumetric computed tomography (CT) seems to be attractive. The image quality of helical CT with single breath-hold and low-dose technique (screening CT) was compared with conventional sequential CT in 12 patients to detect the pulmonary metastases. The screening CT protocol consisted of a 20 mm/sec table feed during a 20-second breath-hold at 40 mA, with reconstruction of images at 10 mm intervals. Conventional CT was performed with a 1-second scan time, 200 mA, and contiguous 10 mm-thick sections. In the evaluation of mediastinal vessels, bronchi and pulmonary nodules, screening CT showed high detectability images comparable to conventional CT. But subsegmental bronchi or small nodules overlapping pulmonary vessels were more difficult to visualize by screening CT because of image noise. The authors conclude that although further improvement is necessary, screening CT of the lung is an attractive new application of CT.