Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Endotracheal tube still appears to low , coursing towards the mainstem bronchus and can be retracted approximately 3 .5 cm . There continues to be interval improvement in aeration of the left lung however , there is continued left lower lobe collapse . Mediastinal contour has now normalized . Cardiac silhouette is normal . Right lung remains clear .
    OUTPUT:
    
1 . Endotracheal tube coursing towards the mainstem bronchus and can be retracted approximately 3 .5 cm for more optimal positioning . 2 . Improvement of left lung aeration with continued lower lobe collapse . 3 . Mediastinal contour has normalized .