Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Lung volumes are low . The cardiac , mediastinal and hilar contours are unremarkable . Atherosclerotic calcifications are again noted at the aortic knob . There is no pulmonary edema . There is slightly improved aeration at the left lung base with residual patchy bibasilar opacities possibly reflecting atelectasis . No pleural effusion , new focal consolidation or pneumothorax is present .
    OUTPUT:
    
Interval improvement in aeration of the left lung base with residual patchy bibasilar opacities , possibly atelectasis but infection or aspiration can not be excluded .