Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Heart size is normal . The mediastinal and hilar contours are normal . The pulmonary vasculature is normal . A linear opacity at the base of the left lung is most consistent with atelectasis . No pleural effusion or pneumothorax is seen .
    OUTPUT:
    
Left basal linear atelectasis or scar . No focal consolidation to suggest pneumonia .