I had one annually for a number of years for an acoustic neuroma and had a contrast medium each time. It’s just an injection in your arm so that the images are clearer. I always worried that I would sneeze or my nose would itch, neither ever happened but the scanner staff were so reassuring and said it doesn’t matter, if that happens and we need to, we’ll do the scan again. As others have said upthread, it does clank and bang but really, truly, honestly, like most experiences, it’s never, ever as bad as you fear. Nothing we say will really convince, but you will be OK and the staff will be so sympathetic and helpful. We’re all cheering you on!