- Any contra-indications for MRI. Participants are to be screened by a CMRTO (The College of Medical Radiation Technologists of Ontario) certified MRI Technologist in order to determine the MRI compatibility or exclusion of implantable/external devices according to the manufacturer's safety guidelines. The devises include cerebral aneurysm clips, neuro-stimulator, mechanical heart valves, cardiac stents, IUDs(intrauterine device), vena cava filters, shunts, embolization coils, cochlear implants, non-removable prosthesis/artificial limbs. Contraindications are pacemaker of defibrillator, shrapnel/metallic fragments, previous brain surgery, seizure, severe claustrophobia, weight or body index that will prevent a successful MRI study