Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The lungs are well expanded . The right lung is clear , but the left lung demonstrates a subtle opacity in the mid lung field whioch was not present in the prior examination . Cardiomediastinal and hilar contours are unremarkable . There is no pleural effusion or pneumothorax .
    OUTPUT:
    
Subtle opacity in the left mid lung field suggests focus of infection / inflammation . Follow up to resolution 4 weeks after treatment is recommended . These findings were communicated to physician covering for Dr ___ on ___ at 5 :45 pm by Dr ___ ___ telephone .