More madness with controls.
So, important things to keep in mind as a control for a study. If you're going to do MRI, you can't have metal on your body, and especially not in your body. If you have a metal plate in your head, we need to know.
The MRI is a giant magnet. Metal objects can and do get sucked into the magnet, and will bounce around inside the bore. If there's a person in there? Not good. Part of MRI safety (actually, the most important part of MRI safety) is not to bring any sort of metal into the magnet. Not only is it dangerous, but it can damage the machine.
The best MRI story ever, passed from researcher to researcher:
A cop comes in to the lab to serve as a control in a study. The lab techs explain to him again and again the importance of not bringing in metal. He agrees, passes the medical screening, and answers the MRI screening questionairre honestly. He removes all the obvious metal he has and goes in to the room.
As soon as he gets close (the magnetic field gets stronger the closer you get), the gun that's strapped to his ankle flies into the magnet.