I'm cheering because it's over. I spent a week with my stomach in turmoil anticipating going to get an MRI on my neck - to see what has been causing pain over the years. I had previously had an X-Ray, at least I think that's what it was, and found that I could be claustrophobic when a large box camera is over my head, for a fairly long time, about 3" from my nose. I had never suffered from claustrophobia before then. But something about the feeling of a kind of wall almost pressing against me, while I was not able to escape it, caused feelings of panic and shortness of breath. I manged to get through it, but just barely. Therefore I was afraid that I would not be able to complete the MRI and I really did want to find out what was bothering my neck. I couldn't help thinking of those mysteries in film and print where somebody is accidentally trapped in a coffin-like box and buried alive, to be rescued at the last moment. The horror of that idea struck me. I'm not sure I could ever write that into a story - my poor protagonist might go insane, or maybe I would.
What I did to get through the MRI was to go to-----the Internet! Of course, there were people writing about it. Needless to say, there were horror stories of people who would never do it again. But there were also good tips from people who became proactive and got through it. So when I arrived at the doctor's office, I informed the attendant that I suffered from claustrophobia to some extent and he gave me a blindfold, one of the Internet tips. I must note that the MRI machine was one of those open on all sides and it didn't actually look all that bad. But I took no chances and placed the blindfold over my eyes and didn't even peek to see how close the machine was to me. The only thing then was to get through the loud noises produced by the MRI. That I could handle. Also, I realized that focusing my mind on something else helped a lot. I didn't let myself even think about being trapped and breathed evenly.
This may all seem silly to some people, but phobias are real to the people they affect. This particular one is dealt with by feeling in control. And trying to compose the next chapter of your book.