Implantable wireless accoustic stimulators with high energy conversion efficiencies
A controller-transmitter transmits acoustic energy through the body to an implanted acoustic receiver-stimulator. The receiver-stimulator converts the acoustic energy into electrical energy and delivers the electrical energy to tissue using an electrode assembly. The receiver-stimulator limits the output voltage delivered to the tissue to a predetermined maximum output voltage. In the presence of interfering acoustic energy sources output voltages are thereby limited prior to being delivered to the tissue. Furthermore, the controller-transmitter estimates the output voltage that is delivered to the tissue by the implanted receiver-stimulator. The controller-transmitter measures a query spike voltage resulting from the electrical energy delivered to the tissue by the receiver-stimulator, and computes a ratio of the predetermined maximum output voltage and a maximum query spike voltage. The maximum query spike voltage is computed by detecting a query spike voltage plateau. Based on this ratio, the controller-transmitter uses a measured query spike voltage to estimate the output voltage delivered by the receiver-stimulator to tissue.
1. An implantable medical device system for delivering electrical stimulation pulses to a patient, comprising:
a controller-transmitter defining a first implantable device having an output transducer assembly and control circuitry, wherein the control circuitry is configured to control the output transducer assembly to transmit a first acoustic energy at an electrical pulse rate configured to electrically pace/stimulate cardiac tissue; and
a receiver-stimulator defining a second implantable device having a piezoelectric receiving transducer configured to receive the first acoustic energy from the controller-transmitter and a second acoustic energy from a diagnostic ultrasound source and convert it to an electrical output, a circuit coupled to the piezoelectric receiving transducer to receive the electrical output and produce an output energy, and electrodes electrically coupled to the circuit and configured to deliver the output energy to pace/stimulate the cardiac tissue, wherein the circuit is configured to produce the output energy by —
(a) delivering to the electrodes a first portion of the electrical output produced by the piezoelectric receiving transducer in response to the first acoustic energy transmitted by the controller-transmitter, and
(b) filtering out a second portion of the electrical output produced by the piezoelectric receiving transducer in response to the second acoustic energy produced by the diagnostic ultrasound source.
2. The system of claim 1 wherein the output transducer assembly comprises multiple phased array transducers configured to steer and focus the first acoustic energy.
3. The system of claim 1 wherein the circuit of the receiver-stimulator comprises a low pass filter configured to eliminate voltage associated with the second acoustic energy produced by the diagnostic ultrasound source.
4. The system of claim 1 wherein the circuit of the receiver-stimulator comprises a low pass filter configured to provide electrical energy to the electrodes associated with the first acoustic energy in the range of 800 kHz to 1,3 MHz while filtering out electrical energy associated with the second acoustic energy in the range of 2 MHz to 10 MHz.
5. An implantable medical device system for delivering electrical stimulation pulses to a patient, comprising:
a controller-transmitter defining a first implantable device having an output transducer assembly and control circuitry, wherein the control circuitry is configured to control the output transducer assembly to transmit a first acoustic energy configured to electrically pace/stimulate cardiac tissue; and
a receiver-stimulator defining a second implantable device having a piezoelectric receiving transducer configured to receive the first acoustic energy from the controller-transmitter and a second acoustic energy from a diagnostic ultrasound source and convert it to an electrical output, a circuit coupled to the piezoelectric receiving transducer to receive the electrical output and produce an output energy, and electrodes electrically coupled to the circuit and configured to deliver the output energy to pace/stimulate the cardiac tissue, wherein the circuit is configured to produce the output energy by —
(a) delivering to the electrodes a first portion of the electrical output produced by the piezoelectric receiving transducer in response to the first acoustic energy transmitted by the controller-transmitter, and
(b) preventing a second portion of the electrical output produced by the piezoelectric receiving transducer in response to the second acoustic energy produced by the diagnostic ultrasound source from being delivered to the electrodes.
6. The system of claim 5 wherein the output transducer assembly comprises multiple phased array transducers configured to steer and focus the first acoustic energy.
7. The system of claim 5 wherein the circuit of the receiver-stimulator comprises a low pass filter configured to eliminate voltage associated with the second acoustic energy produced by the diagnostic ultrasound source.
8. The system of claim 5 wherein the circuit of the receiver-stimulator comprises a low pass filter configured to provide electrical energy to the electrodes associated with the first acoustic energy in the range of 800 kHz to 1.3 MHz while filtering out electrical energy associated with the second acoustic energy in the range of 2 MHz to 10 MHz.