The present invention reduces patient risks associated with RF-induced thermogenic tissue damage and with pulsed gradient-field-induced arrhythmias by using a defibrillator lead having a self-healing dielectric material that prevents induced voltages from MRI equipment from damaging an ICD or causing unintended defibrillation shocks to a patient. The rhenium content is at least 2. A user-actuated articulated sheath surrounds a portion of the medical ultrasonic blade. The light emitting face includes a lateral face extending upwardly from an outer periphery of the connecting face and a top face located above the light incident face. Means are further included for sealing the inverted structure, preferably in the form of a flap and associated adhesive. A method for treating keratinous substances with the compositions and delivery systems is also disclosed.