When in college, I had to do a CAT Scan for a sinus problem. Was in the tube for almost 2 hours while the mapped out my sinuses so they could determine how to "fix" me. I had to lay on my stomache, with my arms at my side and my head pushed back as far as it would go. This was back when the machines were very small and cramped. The machines now are much larger, and often of the "open" type. Plus, the MRI often yeilds much better results than the CT scan. Good luck, you will get through this with no problems.