Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Compared to the prior chest radiograph , there is improvement in bibasilar opacities , which was likely atelectasis . Retrocardiac opacity persists and most likely represents atelectasis . Heart size and mediastinal contours are stable . Endotracheal tube tip remains 4 cm ) . No pleural effusion or pneumothorax .
    OUTPUT:
    
Interval improvement in bibasilar atelectasis with continued retrocardiac opacification , likely atelectasis .