Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The lungs are clear with the exception of minimal left base atlectasis . The cardiomediastinal silhouette and hilar contours are unremarkable . There is no pleural effusion or pneumothorax . Degenerative changes of the thoracic spine are again noted .
    OUTPUT:
    
No evidence of acute pulmonary process .