Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The cardiac silhouette size is normal . Atherosclerotic calcifications are noted at the aortic knob . Mediastinal and hilar contours are unremarkable . Pulmonary vasculature is normal . Patchy opacities are noted in the lung bases , most suggestive of atelectasis given the linear appearance . No pleural effusion or pneumothorax is seen . No acute osseous abnormalities identified .
    OUTPUT:
    
Patchy bibasilar airspace opacities most likely reflect areas of atelectasis though infection is not completely excluded .