Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The heart size , mediastinal , and hilar contours are normal . There is a linear opacity identified at the right lung base medially . The lungs are otherwise clear without pleural effusion , focal consolidation , or pneumothorax . No evidence of free subdiaphragmatic air .
    OUTPUT:
    
No evidence of free subdiaphragmatic air . Right lung base opacity medially potentially atelectasis noting that infection can not be excluded .