Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: As compared to prior chest radiograph from ___ , there is improved aeration of the left perihilar region ; however , atelectasis at the left lower lung base persists . Left pneumothorax is improving . Right lung is clear . The cardiomediastinal contours are normal . ET tube is in standard position . Left IJ catheter tip terminates in the mid SVC . NG tube remains coiled in the stomach . A left chest tube remains in unchanged position .
    OUTPUT:
    
Improving left pneumothorax and aeration of left perihilar region , with persistent left lower lobe atelectasis .