Controlling radio frequency interference from neurological prostheses

The simplest kind of radio frequency (RF) coupled neurological prosthesis, in which a burst of RF, generated by the external equipment, provides the stimulus energy via a passive implanted receiver, is the most troublesome in respect of RF interference (RFI). Because the low ratio of pulse duration to interpulse interval is usually the case, the peak power transmitted is necessarily high, of the order of watts. This paper outlines a series of measurements by which the mode of RFI generation by a typical external equipment was precisely identified, enabling rational and appropriate countermeasures to be taken.