Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Compared to prior , there is improved appearance of left basal atelectasis , though small left pleural effusion persists . The right basal atelectasis is stable . Heart size is unchanged . Mediastinal and hilar contours are unchanged . Aortic knob calcification is again seen , unchanged .
    OUTPUT:
    
Improving left basal atelectasis and small left pleural effusion .