Hi Lucy,
The SBFT is a very common diagnostic test for Crohn's. It gives a very clear picture of the small intestine, particularly the Terminal Ilium, which can't be reached by conlonoscopy or endoscopy.
There is a prep that you have to go through beforehand. Also, sometimes they have to imput air to get a clearer picture.
It's relatively painless, just mildy uncomfortable at times. I'm not an expert, and hopefully you'll get a few more replies.
You've come to the right place. This is an excellent forum. There truly is some very caring/compassionate individuals here.