Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: AP and lateral views of the chest were performed with patient positioned upright . Linear density at the left lung base is most compatible with subsegmental atelectasis and scarring as seen on prior CT chest from ___ . Otherwise , the lungs are clear . No effusion or pneumothorax . The cardiomediastinal silhouette is normal . Bony structures are intact . No free air below the right hemidiaphragm .
    OUTPUT:
    
Linear density at the left lung base is most compatible with atelectasis / scarring as seen on prior CT chest from ___ . No convincing signs of pneumonia .