Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Heart size is normal with mild tortuosity of the thoracic aorta . Hilar contours are normal . Subtle nodular opacity in the left mid lung is at the intersection between an anterior and posterior rib and likely represents overlap of bony structures and vasculature . Lungs are clear . There is no pleural effusion or pneumothorax .
    OUTPUT:
    
Normal chest radiograph ; specifically , no evidence of pneumonia .