Parametric biostimulation

This paper reports how through computer-assisted field shaping a method can be developed which may lead to a practical, non-invasive and non-galvanic stimulation system. In this new concept, the major portion of the required stimulus energy will be supplied by an eddy current, produced inside the biological conductor by means of an induced EMF. The magnetic field is shaped in such a way that the electrical field strength within the specimen nowhere exceeds the stimulus threshold. A small additional amount of energy, e.g., ultrasonic radiation, is focused into a small volume containing the tissue to be stimulated. This, partly by mechanical excitation, partly by rectification of a sine component in the EMF, will result in exceeding the stimulus threshold only within the focal volume. This concept can be expected to be superior to galvanic methods where field densities in unwanted areas always far exceed those in the tissue to be stimulated. Results of magnetic field calculations produced optimization criteria and show how system requirements can be met by field shaping, resulting from a suitable arrangement of independently excited coil elements on a spheroidal ferromagnetic core structure.