Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The lungs are well expanded . The retrocardiac opacity which was seen on ___ is improved but minimal residual opacity persists . The cardiomediastinal silhouette , hilar contours and pleural surfaces appear normal . There is no pleural effusion or pneumothorax .
    OUTPUT:
    
Minimal residual retrocardiac opacity , likely atelectasis although persistent infection can not be excluded .