I work in EMS. I routinely take patients into the MRI @ Suburban. I have metal in my pockets, belt, boots, etc.... I bring patients in on a METAL stretcher, I help move them over to the non-magnetic stretcher they use; then they secure the room, conduct a safety check BEFORE energizing the equipment..... Anything else is the problem of the operator not the cop or other personnel with the metal object.There are plenty of videos of guns going off in and/or around MRI machines on the internet.
You only need to be in the room when they are on, for Mr. Murphy to make an appearance. Some guns even get ripped right out of their holster.