Pulmonary opacity Abnormal subpleural morphology Subpleural curvilinear line 2021-03-12T12:28:43Z This finding is a thin curvilinear opacity, 1-3 mm in thickness, lying less than 1 cm from and parallel to the pleural surface. It corresponds to atelectasis of normal lung if seen in the dependent posteroinferior portion of lung of a patient in the supine position and is subsequently shown to disappear on CT sections acquired with the patient prone. It may also be encountered in patients with pulmonary edema or fibrosis (other signs are usually present). Though described in the context of asbestosis, subpleural curvilinear line is not specific for asbestosis. See Figure 68 of Hansell DM, et al., Fleischner Society: glossary of terms for thoracic imaging. Radiology. 2008;246:697-722.