Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Lung volumes are very low and the film is somewhat underpenetrated . Faint bibasilar opacities are similar to yesterday 's study and may reflect mild atelectasis ; however , pneumonia or aspiration can not be completely excluded . The heart is mildly enlarged . The mediastinal and hilar contours are unremarkable . There is calcification of the aortic arch . There is no large pleural effusion or pneumothorax .
    OUTPUT:
    
Faint bibasilar opacities in the setting of low lung volumes may reflect atelectasis , although pneumonia or aspiration in the right clinical setting can not be completely excluded .