- (1) Have ferromagnetic objects in their bodies which might be adversely affected by MRI including implanted pacemakers, medication pumps, aneurysm clips; metallic prostheses (including metal pins and rods, heart valves or cochlear implants, shrapnel fragments, permanent eye liner or small metal fragments in the eye that welders and other metal works may have- any doubt about presence of these objects will result in exclusion from this study), or if candidates are uncomfortable in small closed spaces (have claustrophobia), or cannot lie comfortably on their back for up to one hour;