Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Lung volumes remain low , but slightly improved compared to the prior exam . The cardiac , mediastinal and hilar contours are unchanged , with the heart size remaining top normal . Pulmonary vascularity is normal . Minimal bibasilar atelectasis is noted , without focal consolidation . No pleural effusion or pneumothorax is seen . No acute osseous abnormalities are demonstrated .
    OUTPUT:
    
Slightly improved aeration of the lung bases with mild bibasilar atelectasis .