If you want to know for SURE that it is CT, ask them to refer you for a flouroscopy. Sometimes a regular chest xray will show it, but sometimes not. A flouroscopy is an xray that shows the trachea on inspiration and expiration. At least then you would have a definitive answer. I believe it is relatively inexpensive (it has been a long time since I had one done and I don't remember)....not a lot more than a regular xray.... but you could call and ask.
What is Fluoroscopy?