Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Patient is status post median sternotomy . The cardiomediastinal and hilar contours are within normal limits . As compared to prior chest radiograph from ___ , there has been interval improvement of bibasilar opacities . However , subtle basilar opacities persist and may be due to aspiration , underlying emphysema , underlying infectious process is not entirely excluded . There is no pneumothorax or large pleural effusion .
    OUTPUT:
    
Improved bibasilar opacities , however subtle basilar opacities persists and these could be due to aspiration , underlying emphysema , underlying infectious process not excluded . Dedicated PA and lateral views would be helpful for further evaluation . If concern for a pulmonary lesion , a non urgent chest CT would be more sensitive .