Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Frontal and lateral radiographs of the chest demonstrate normal heart size . The mediastinal silhouette and hilar contours are normal . Bibasilar opacities likely reflect atelectasis ; although , an underlying infectious process is possible . No pleural effusion or pneumothorax .
    OUTPUT:
    
Bibasilar opacities likely reflecting chronic atelectasis ; although , an underlying infection or aspiration is possible .