Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Heart size is top normal . The aorta is tortuous . The mediastinal and hilar contours are unremarkable . The pulmonary vascularity is normal . Linear opacities in the lung bases likely reflect atelectasis . There is no focal consolidation , pleural effusion or pneumothorax is identified . Multilevel mild degenerative changes are seen within the thoracic spine .
    OUTPUT:
    
Mild bibasilar atelectasis . No evidence of pulmonary vascular congestion .