Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The lungs are clear . Linear opacity is seen in the right lung base , likely atelectasis , however a developing pneumonia can not be excluded . The heart size is unchanged . Incidental note is made of an azygous fissure . No pneumothorax , pleural effusion , or pulmonary edema . Moderate degenerative changes are seen in the thoracic spine . No compression fractures are seen .
    OUTPUT:
    
Linear opacity in the right lung base is likely atelectasis . However , in the appropriate clinical setting , a developing pneumonia can not be excluded .