Having participated on the researcher end of fMRI stuff, I am impressed if they can get a lot of women to actually climax in there. You really need to be focused on what you're doing, because there are a multitude of distractions. fMRI is significantly louder than a typical MRI exam, for example.

On a side not. You can bring metal stuff into the MRI room. It just can't be ferromagnetic. It's fun to play with sheets of aluminum and coins in the high field area. The metal will resist movement due to eddy current effects.