Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: There is slightly increased retrocardiac opacification which is likely due to atelectasis . The lungs are otherwise clear . There is no pneumothorax . Aortic arch calcifications are incidentally noted . Regional bones are osteopenic . An IVC filter is partially imaged .
    OUTPUT:
    
Increased retrocardiac airspace opacification is likely due to atelectasis .