Round atelectasis

  Courtesy of Omar Giyab MD
 

• Rounded density at lung base
• Contiguous to pleura
• Comet tail on CT: vessels and bronchi converge upon and appear to swirl around mass
• Crow’s feet — linear bands radiating from mass into lung parenchyma
• Linear densities radiate back toward hilum
• May have air bronchogram

mild dilatation of peripheral bronchi

Not pleural fluid according to the mean density

intralesional linear hypodensity (pleural origin)