My dd is afraid of CTs and MRIs too. I was allowed to go in while they started her IV and calm her down. We sang a Neil Young song - Hey, Hey - and I told her to keep her eyes closed and visualize people around her that she would not want to be a chicken in front of.
That seemed to do the trick.
That's what I do when I don't want to feel afraid - just act like there's someone around and I have to be tough so I don't embarrass myself.
Good idea having you *tube shootin' suit* ready to go too. I hate having to gown up.