Two things, need to confirm. (1) Terri has a metal shunt or electrode in her head from previous treatments and (2) unless the metallic object is non-ferrous, wouldn't MRI be dangerous to perform?
Yes, they would have to go in and take that out. Or perhaps they can get similar results with a PET scan, which does not rely on magnetism.
The question is, if it's a shunt, why is it there? Did she have bleeding in her brain at one time? Oxygen deprivation from a heart attack isn't going to cause that. Trauma would cause that.