An implantable antenna for communication with implantable medical devices

Abstract

Numerous medical devices are implanted in the body for medical use. These include pacemakers and defibrillators, hormone pumps, nerve stimulators, and more. With the advancement and miniaturization of bio-electronics it is likely that the array of implantable medical devices will continue to expand in the years to come. Medical implants are intended to stay in the body for many years or decades, and it is often necessary to communicate with the device to download data about the health of the device or its batteries or the health of the patient, or to upload changes in settings or new procedures specified by the doctor. The design of antennas that can communicate with implantable devices is an interesting and challenging problem. The antenna must be small and long-term biocompatible, preferably able to be mounted on existing implant hardware or to utilize part of the hardware itself. The antenna must be electrically insulated from the body so as not to short out and be ineffective, and it must be efficient so as not to excessively drain the batteries. This paper describes the design and optimization of a spiral-shaped microstrip antenna attached to the 2x2x1/2 titanium battery pack of an implantable device imbedded in the body. The battery pack acts as the ground plane for the microstrip antenna and is in direct contact with the body. Two methods were used to optimize this antenna. The first was to simply try several designs in order to find the one that provided the best performance. This resulted in the antenna. The second method was to interface the XFDTD software (from Remcom, Inc.) which was used to simulate the antenna performance with iSIGHT (from Engineous, Inc.), an integration and optimization design program. Both antennas were prototyped and tested. The performance of both antennas is virtually identical. The use of optimization software saved significant man-hours in the optimization of this design.