Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Heart size is normal . Mediastinal and hilar contours are unremarkable . Pulmonary vascularity is normal . Linear opacity within the left lower lobe likely reflects subsegmental atelectasis . Right lung is clear . No pleural effusion or pneumothorax is identified . Surgical clips from prior cholecystectomy are noted within the upper abdomen . No acute osseous abnormality is seen .
    OUTPUT:
    
Subsegmental atelectasis in the left lung base . Otherwise no acute cardiopulmonary abnormality .