Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The lungs are well expanded and clear . There is no pneumothorax or pleural effusion . Cardiomediastinal silhouette is unremarkable . Slight calcification of the aortic knob is incidentally noted .
    OUTPUT:
    
Essentially normal chest radiograph with no evidence of pneumonia or other acute pulmonary or cardiac pathology .