Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The heart size is normal . The mediastinal and hilar contours are unchanged . The pulmonary vasculature is not engorged . Persistent crescentic focal opacity is noted within the left lower lobe , which could reflect an area of infection or atelectasis . Minimal streaky opacities elsewhere in both lung bases are compatible with areas of atelectasis . No pleural effusion or pneumothorax is seen . Mild paraseptal emphysematous changes are noted in the lung apices . There are no acute osseous abnormalities .
    OUTPUT:
    
Persistent crescentic area of opacification within the left lower lobe which may reflect an area of infection or atelectasis .