Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Linear opacities at the lung bases bilaterally reflect a combination of scarring and atelectasis as seen on a prior cross - sectional study of the chest . There is no new focal consolidation , pleural effusion , or pneumothorax . Heart size and mediastinal contours are stable . Osseous structures appear intact .
    OUTPUT:
    
Mild bibasilar scarring / atelectasis , but no evidence of pneumonia .