Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: There is subtle opacification overlying the spine that is only definitively seen on the lateral view , which is new compared to the radiograph dated ___ . Otherwise , the lungs are clear . No pulmonary edema . Heart size is normal . The thoracic aorta is markedly tortuous , unchanged compared to prior . No pleural effusion or pneumothorax is seen .
    OUTPUT:
    
Opacification overlying the spine that is only definitively seen on the lateral view without correlate on the frontal . This could represent atelectasis however early infection or aspiration are difficult to exclude .