The "ring-around-the-artery" sign in pneumomediastinum.
Following subclavian vein catheterization, a small pneumomediastinum resulted in the collection of a thin layer of gas around the right pulmonary artery (RPA), which, on the lateral chest radiography, produced a distinctive oval shadow at the right hilum.
D000328:Adult; D002404:Catheterization / Q000009:adverse effects; D005260:Female; D006801:Humans; D008478:Mediastinal Emphysema / Q000000981:diagnostic imaging* / Q000209:etiology; D011651:Pulmonary Artery / Q000000981:diagnostic imaging*; D011859:Radiography; D013350:Subclavian Vein