It is NOT childish and don't beat yourself up for it. It happens to a lot of us with or without be claustrophobic.

I experienced that once. I wanted to be "tough" and decided "heck, since I have MS I am going to be doing these all the time so, suck it up." No, it didn't happen that way. I was in the "tube" for maybe a minute or 2 and they had to get me out. We tried it again, same thing happened. They ended up giving me Xanax under my tongue and within 10 minutes I was relaxed enough to do it.

I now go to MRI's sedated. No more sucking it up.