I don't know if I have had a CAT scan before (possibly when I was younger), but I have had an MRI taken before because I have epilepsy and they had to do a brain scan. If you are claustrophobic, MRIs can be fairly unnerving since your entire body has to be inside the tube for a while. I had to stay in one for about 30 minutes. I wasn't too scared of the whole ordeal, but it is not fun having to lie still in the same position for that long inside of a tube.