Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: The lungs are moderately well inflated . There has been partial resolution of the retrocardiac opacity seen on prior . A region of linear opacity remains in the retrocardiac space , similar as compared to CT chest dated ___ , likely representing atelectasis or scar . The heart size is normal . There is no pleural effusion or pneumothorax .
    OUTPUT:
    
There has been partial resolution of the retrocardiac density seen on prior . The residual linear density , present since at least ___ , is scar or persistent atelectasis .