PLEURAL EFFUSION Occasionally,pleural fluid collections in the major or minor fissures may appear as a pulmonary mass(肺部团块) and are referred to as pseudotumors ()A lateral Decubitus(侧卧位)chest radiograph can be obtained to determine whether fluid is free flowing or loculated 的). Chest CT provides better characterization of pleural and parenchymal abnormalities by better defining loculated effusions,distinguishing between atelectasis (and effusion,and distinguishing loculated effusion from lung abscess(肺脓肿) 第 一 部 分 Occasionally, pleural fluid collections in the major or minor fissures may appear as a pulmonary mass（肺部团块） and are referred to as pseudotumors（假瘤）. A lateral Decubitus（侧卧位） chest radiograph can be obtained to determine whether fluid is free flowing or loculated（包裹 的）. Chest CT provides better characterization of pleural and parenchymal abnormalities by better defining loculated effusions, distinguishing between atelectasis（不张） and effusion, and distinguishing loculated effusion from lung abscess（肺脓肿） PLEURAL EFFUSION