I have done several MRIs and first time I freaked and felt extremely claustrophobic. Later on I got used and as everyone mentioned have yellow earfoam plugs, don't open your eyes etc., and you will be fine. If the MRI is open bore (not open MRI which is useless for brain) you don't feel that claustrophobic.

If you really want to take this MRI thing one step further you can look for clinical trials (http://clinicaltrials.gov) for 7T (most of the facilities has only 1.5T or 3T). I have a friend who is a post doc at University of Philadelphia and he has been involved in this MRI magnets for about a decade.

He swears the images are amazing what it shows. He told he has been on that machine several time and can stay there for 3 hours easily. This machine is longer tunnel than regular machine. Wow! Seriously

He wants to look at my brain and I have to travel to Philly and all that. Even NIH at Bethesda doing it and I might do that at at some point. Just my 2 cents.