Apical opacity: a normal finding on posteroanterior chest radiographs

Of 423 posteroanterior chest radiographs in patients aged 21-66 years, 12.8% showed a homogeneous oval opacity with unsharp margins at the right apex and 16.8% at the left apex. Anatomy of the vessel, observations in patients with pneumothorax or atherosclerotic calcification, and fluoroscopic and computed tomographic evidence lead to the conclusion that the apical opacity is produced by the subclavian artery.