A wireless batteryless deep-seated implantable ultrasonic pulser-receiver powered by magnetic coupling

This study tests a deep-seated implantable ultrasonic pulser-receiver powered wirelessly by magnetic coupling. The energy-transmitting coil, which wraps around the body, is driven at 5.7 MHz using 1.2A to generate a magnetic field. A 2 cm receiving coil is positioned at the center of the primary coil for powering the implantable device. A capacitor-diode voltage multiplier is used to step-up the receiving coil voltage from 12.5V to 50V to operate an ultrasonic pulser. FEA magnetic field simulations, bench top and ex-vivo rabbit measurements showed that the magnetic energy absorption in body tissue is negligible, and that the magnetic coupling has low sensitivity to receiving coil placement. The receiving coil and the implantable circuit do not contain ferromagnetic material so an MR-compatible device can be achieved. A 5-MHz ultrasound transducer operating in pulse-echo mode is used to test the circuit. Received echoes are amplified, envelope-detected, frequency-modulated, and transmitted out of the body by radio wave. The modulated echo envelope was received by an external receiver located approximately 10cm away from the primary coil. The study establishes the feasibility of a deep-seated implantable ultrasonic pulser-receiver powered by coplanar magnetic coupling.