Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Frontal and lateral views of the chest were obtained . The heart is of normal size with normal cardiomediastinal contours . A left lung base focal opacity is more conspicuous than on prior exams . The pulmonary vasculature is unremarkable . No pleural effusion or pneumothorax . Osseous structures are unremarkable . No radiopaque foreign bodies .
    OUTPUT:
    
Left lung base focal opacity , more conspicuous than on prior exams , which may potentially represent atelectasis , although infection is not excluded .