- MRI exclusions, including claustrophobia, cardiac pacemaker, metal fragments in eyes/skin/body (shrapnel), aortic/aneurysm clips, prosthesis, by-pass surgery/coronary artery clips, hearing aid, heart valve replacement, shunt (ventricular or spinal), electrodes, metal plates/pins/screws/wires, or neuro/bio-stimulators (TENS unit), persons who have ever been a metal worker/welder, history of eye surgery/eyes washed out because of metal, women who are or may be pregnant (determined by a positive pregnancy test), women using an intrauterine device, vision problems uncorrectable with lenses, claustrophobia, inability to lie still on one's back for 60 minutes; prior neurosurgery; older tattoos with metal dyes; unwillingness to remove nose, ear, tongue, or face rings.