Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The lungs are low in volume , but improved ; previous left basal atelectasis has resolved , but a band persists in the superior segment . The cardiomediastinal silhouette , hilar contours , and pleural surfaces are normal . No pleural effusion or pneumothorax is present . A aortic valve replacement is noted . Sternal wires are intact .
    OUTPUT:
    
No acute intrathoracic process .