Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Heart size is normal . Mediastinal and hilar contours are within normal limits . The pulmonary vasculature is normal . Linear opacities in left lower lobe likely reflect areas of subsegmental atelectasis . No focal consolidation , pleural effusion or pneumothorax is identified . There are no acute osseous abnormalities .
    OUTPUT:
    
Left lower lobe subsegmental atelectasis .