Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Heart size is top normal . The aorta is mildly tortuous . Hilar contours are normal . The pulmonary vascularity is not engorged . Linear opacity within the left lung base likely reflects subsegmental atelectasis . Right lung is clear . No pleural effusion , focal consolidation or pneumothorax is present . There are no acute osseous abnormalities .
    OUTPUT:
    
Subsegmental atelectasis in the left lung base .