Revolver bullets are made from a lead alloy and cannot be magnetized. The steel frame of a revolver may be possible to magnetize, but it is doubtful that the magnetization would stay as long as depicted.
If the magnetic field of the MRI is strong enough to magnetize a steel revolver as depicted, the revolver should have made violent movements. However, no such problem is depicted.
When the Dr's body is discovered in the alley, they check her back and state that she was shot in the back, and report no exit wound, yet the hole in the Dr's jacket was obviously made from the inside out - therefore indicating it was an EXIT wound so she would've had to have been shot from the front.