Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The cardiac , mediastinal and hilar contours are within normal limits . Pulmonary vascularity is normal . Minimal streaky opacity in the retrocardiac region may reflect atelectasis though infection or aspiration can not be completely excluded . No focal consolidation , pleural effusion or pneumothorax is present . Punctate radiopaque density projecting over the midline upper chest is likely external to the patient and not seen on the lateral view . There are no acute osseous abnormalities .
    OUTPUT:
    
Minimal retrocardiac streaky opacity which could reflect atelectasis , but aspiration or infection can not be excluded .