Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The lung volumes are low which causes crowding of the bronchovascular structures . Bilateral lower lobe opacities most likely represent atelectasis . The heart size is normal . There is calcification of the aortic knob . There is no pleural effusion or pneumothorax . There is an old right rib fracture .
    OUTPUT:
    
No focal opacity concerning for pneumonia .