Method and system for powering implantable devices
A ventricular assist device (VAD) system includes one or more external subsystems including an amplifier energizing a drive loop with alternating current, and a Tx resonator inductively coupled to the drive loop. An implanted subsystem includes a VAD, an Rx resonator that forms a magnetically coupled resonator with the Tx resonator, and a load loop for providing power to the VAD that is inductively coupled to the Rx resonator. A sensor monitors the drive loop and a controller uses the sensor data to adjust a system parameter to optimize energy transfer performance. Distributing a plurality of the external subsystems throughout a defined space provides a patient with freedom of movement within the defined space.
1. A system for powering an implantable medical device, comprising:
at least one external subsystem comprising a drive loop, an amplifier operably connected to selectively provide radio frequency energy to the drive loop, a transmitter resonator configured to be inductively coupled to the drive loop, and a sensor operable to monitor the drive loop;
an implantable subsystem configured to be implanted in a patient and comprising an implantable medical device, a load loop operably connected to the medical device, and a receiver resonator configured to be inductively coupled to the load loop;
wherein during operation the transmitter resonator and the receiver resonator comprise a magnetically coupled resonator (MCR) such that the medical device is energized from radio frequency energy from the amplifier that is inductively transmitted from the drive loop to the MCR and is inductively transmitted from the MCR to the load loop; and
a controller operable to receive data from the sensor, and to use the received data to actively control the system to optimize energy transfer efficiency in the MCR.
2. The system of claim 1 , wherein the MCR is effective to transfer energy between the transmitter resonator and the receiver resonator at distances exceeding one meter.
3. The system of claim 1 , wherein the MCR further comprises a relay resonator configured to be worn by the patient.
4. The system of claim 3 , wherein the relay resonator is disposed in a garment configured to position the relay resonator directly over the implanted receiver resonator.
5. The system of claim 3 , wherein the at least one external subsystem comprises a plurality of external subsystems, wherein the plurality of external subsystems are distributed within a defined space, and further wherein the receiver resonator is configured to selectively receive energy from one or more of the plurality of external subsystems disposed within the defined space.
6. The system of claim 5 , wherein the receiver resonator is configured to receive energy from a nearest one of the plurality of external subsystems.
7. The system of claim 5 , further comprising a plurality of additional relay resonators disposed within the defined space.
8. The system of claim 7 , wherein the plurality of external subsystems and the plurality of relay resonators are distributed such that during use the receiver resonator in the implantable subsystem will form an MCR with at least one of the transmitter resonators from anywhere within the defined space.
9. The system of claim 3 , further comprising a portable energy system comprising an energy source and a portable transmitter resonator, wherein the portable energy system is operable to selectively couple the portable transmitter resonator with the receiver resonator through the relay resonator to form an MCR such that the portable energy system provides power to the medical device.
10. The system of claim 1 , wherein the sensor comprises a directional coupler.
11. The system of claim 1 , wherein the controller controls an amplifier output frequency to optimize energy transfer efficiency.
12. The system of claim 1 , wherein the at least one external subsystem further comprises a matching network that is operably connected to the drive loop, and further wherein the controller controls the matching network to change the impedance of the system to optimize energy transfer efficiency in the MCR.
13. The system of claim 12 , wherein the matching network comprises at least one of the group consisting of a π-match network and an L-match network.
14. The system of claim 12 , wherein the implantable subsystem further comprises a second matching network that is operably connected to the load loop.
15. The system of claim 12 , wherein the matching network comprises a switchable bank of capacitors.
16. The system of claim 1 , wherein the transmitter resonator and the receiver resonator are high-Q coils.
17. A method of providing energy to a medical system implanted in a patient, the medical system including a medical device, a load loop operably connected to the medical device, and a receiver resonator inductively coupled to the load loop, the method comprising:
providing a garment having a relay resonator that is positioned in the garment such that the relay resonator overlies the receiver resonator when the garment is worn by the patient;
providing a plurality of external energy systems disposed throughout a defined space, wherein each of the plurality of external energy systems comprise a drive loop connected to an alternating current source and a transmitter resonator configured to form a magnetically coupled resonator (MCR) with the receiver resonator and the relay resonator, wherein the drive loop is inductively coupled to the transmitter resonator;
monitoring the drive loop with a sensor to generate data and using the data to actively adjust an impedance of the MCR.
18. The method of claim 17 , wherein the medical device comprises a ventricular assist device.
19. The method of claim 17 , wherein the garment comprises at least one of a vest, a sash, a shoulder belt, a chest strap, and a pendant.
20. The method of claim 17 , wherein the sensor comprises a directional coupler.