Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Lung volumes are low . Bibasilar linear and subsegmental atelectasis has increased . There is a retrocardiac airspace opacity which is most likely due to atelectasis , but infection can not be excluded . There is no pneumothorax . The heart and mediastinum are magnified by the projection . Regional bones and soft tissues are unremarkable .
    OUTPUT:
    
New retrocardiac opacification is most likely due to atelectasis , but infection can not be excluded in the appropriate clinical context .