Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The heart size is normal . Mediastinal and hilar contours are unremarkable . The pulmonary vasculature is normal . Linear opacities at the lung bases likely reflect atelectasis . No pleural effusion or focal consolidation is present . There is no pneumothorax . Mild multilevel degenerative changes are noted in the thoracic spine .
    OUTPUT:
    
Mild bibasilar atelectasis .