- Pregnant subjects;Subjects unable to undergo MRI (e.g. pacemaker; neurostimulator; implantable cardioverter-defibrillator (ICD) or leads; Foley bladder catheter; medication pump; cochlear or hearing implant; tattoos or other items that cannot be removed and include metal parts (for instance from operations in the past); metal splinter in the eye; vascular clips; denture, which contains magnets);