Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Low lung volumes . There are bibasilar linear opacities , unchanged in comparison to the prior chest radiograph , which likely represent atelectasis . Heart size is top normal . The mediastinal and hilar contours are normal . The pulmonary vasculature is normal . No pleural effusion or pneumothorax is seen . The sternal fracture is visualized and appears unchanged in orientation in comparison to the prior radiograph . The rib fractures are not visualized on these images . There is lumbar fixation hardware , which is incompletely imaged .
    OUTPUT:
    
1 . Bibasilar linear opacities representing atelectasis , which is unchanged . 2 . Sternal fracture again visualized , which is unchanged .