Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Cardiac silhouette size is normal . The aortic knob is calcified and the aorta is mildly tortuous , as seen previously . Mediastinal and hilar contours are unchanged . Pulmonary vasculature is not engorged . Patchy opacities are noted in both lung bases , which may reflect atelectasis , but infection is not excluded . No pleural effusion or pneumothorax is seen . There are no acute osseous abnormalities .
    OUTPUT:
    
Patchy opacities in lung bases could reflect atelectasis but infection can not be excluded in the correct clinical setting .