I do not work in this field, but for the last year I've been working in a lab that does a lot of brain imaging work, and I wound up spending a fair amount of time in the MRI facility. During that time, I asked one of the techs about the training.
He says it's mostly anatomy. If you can handle cramming that stuff into your brain, you'll probably be ok. I don't know what the stats on employment, etc. are, but I do know that EVERYONE in research these days wants to do MRI/fMRI.
When my friend did his training, years ago, it was specifically radiography. There was no dedicated course about MRI. That training occurred on the job. I bet most courses do devote some time to it these days, though, and if you have the option, I'd say you should probably do it.
I may be able to answer specific questions, or I may not. PM me if you'd like.