I think the better question is, what's the damn point?  The scan quality is garbage because of all the fat the radiation/magnetic waves have to travel through. I'm in Maryland, and the world famous hospital here has MRI tables that hold 450 (there is allegedly one of the newer machines that holds more, I think 600 and their satellite locations are expanding so they keep buying the latest and greatest machines).  However I've been told you hear the table whining and grinding attempting to move the massive weight.  Worse is when they go to get up and grab at the technicians in an attempt to pull at them to get up since they can't move their own lard.