Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Heart size is normal . Mediastinal and hilar contours are unremarkable with mild calcification of the aortic arch . Pulmonary vasculature is normal . Minimal patchy left basilar opacity likely reflects atelectasis . No pleural effusion or pneumothorax is present . There are multilevel degenerative changes in the thoracic spine .
    OUTPUT:
    
Minimal patchy opacity in the left lung base , likely reflective of atelectasis .