An MRI wouldn't be a good idea, since guns tend to be made of magnetic metals.
But in general, no, there are very few places (if any) that I'd consider 'not a good idea' to have a gun, because in saying "it's bad to have a gun here", you're implying one of two things:
A) that the place will imbue the gun with a malicious will of its own and it will proceed to kill people by itself - and you'd have to be stupid to mean that - or
B) that the combination of the gun and the place will magically turn the gun owner into a bloodthirsty killer, and merely by virtue of the fact that he's there and has a gun, he will murder people. Which is nearly as stupid as (A).