Apparatus, systems, and methods for current monitoring in ultrasound powered neurostimulation

Patent metadata

Field	Value
Publication number	US-10022566-B2
Application number	US-201113819922-A
Country	US
Kind code	B2
Filing date	Aug 31, 2011
Priority date	Aug 31, 2010
Publication date	Jul 17, 2018
Grant date	Jul 17, 2018

Abstract

Apparatus, systems, and methods for current monitoring in ultrasound powered neurostimulation. The apparatus may include an ultrasound transmitter configured to emit an ultrasound output directed at a piezoelectric device implanted in biological tissue. The apparatus may also include a detector configured to detect an induced current in response to the ultrasound output in the biological tissue. The piezoelectric device may include a piezoelectric material and a diode. The apparatus may include a feedback mechanism to control the amount of induced current in the biological tissue.

First claim

What is claimed is:

1. An apparatus for providing neurostimulation comprising:
a piezoelectric neurostimulation device configured to be implanted in biological tissue;
an ultrasound transmitter configured to emit a ramped ultrasound output directed at the piezoelectric neurostimulation, where the ramped ultrasound output has an amplitude that increases linearly over a period of time;
where the piezoelectric neurostimulation device comprises a piezoelectric material and a semiconductor diode connected in parallel with the piezoelectric material and the neurostimulation device is configured to generate an induced current in biological tissue in response to the ramped ultrasound output, wherein the induced current provides neurostimulation to the biological tissue;
a non-invasive electrical detector configured to detect the induced current over the period of time and determine a transition in the induced current caused by the semiconductor diode reaching its threshold voltage; and
a feedback controller that is configured to calibrate the ultrasound transmitter in response to the transition in induced current detected by the electrical detector.

2. The apparatus of claim 1 , where the electrical detector configured to measure electrical currents at the surface of a body.

3. The apparatus of claim 1 , where the electrical detector is a radio frequency detector configured to measure a radio frequency signal emitted by the piezoelectric neurostimulation device.

4. The apparatus of claim 3 , where the radio frequency signal emitted by the piezoelectric neurostimulation device is a harmonic of a pulse of the ramped ultrasound output.

5. The apparatus of claim 3 , where the radio frequency detector is tuned to the radio frequency signal or one of its harmonics.

6. The apparatus of claim 1 , where the electrical detector is configured to send a signal that represents the intensity of the induced current to a display.

7. The apparatus of claim 1 , where the feedback controller is further configured to average the first plurality of current signals and/or the second plurality of current signals multiple measurements of detected current.

8. The apparatus of claim 1 , where the biological tissue comprises brain tissue, muscle tissue, or nervous system tissue.

9. The apparatus of claim 1 , where the piezoelectric neurostimulation device is connected to at least one extended conductor that is configured to be in direct contact with the biological tissue.

10. The apparatus of claim 1 , where the ultrasound transmitter is configured to emit ultrasound waves at a frequency between 20 kHz to 100 MHz.

11. The apparatus of claim 10 where the ultrasound transmitter is configured to emit ultrasound waves at a frequency between 100 KHz to 1 MHz.

12. The apparatus of claim 1 where the amplitude of the ultrasound output is pulsed for a duration between 1 microsecond and 20 milliseconds.

13. A method of measuring neurostimulation comprising:
providing an ultrasound transmitter proximal to a body surface overlaying a piezoelectric neurostimulation device implanted in biological tissue, where the ultrasound transmitter is configured to emit a ramped ultrasound output and where the piezoelectric neurostimulation device comprises at least a piezoelectric material and a semiconductor diode connected to parallel with the piezoelectric material;
emitting a ramped ultrasound output from the ultrasound transmitter, where the ultrasound output has an amplitude;
creating a current flow from the piezoelectric neurostimulation device in response to the amplitude of ultrasound output;
detecting an induced current in the biological tissue in response to the ramped ultrasound output, wherein the detection may be invasive or non-invasive, and wherein the induced current provides neurostimulation to the biological tissue;
non-invasively detecting the induced current over the period of time and determining a rate of increase of the induced current and a transition in the induced current caused by the semiconductor diode reaching its threshold voltage: and
calibrating the ultrasound output from the ultrasound transmitter in response to the transition in the induced current detected.

14. The method of claim 13 , where a frequency of the ultrasound output is adjusted in response to the rate of increase of the induced current.

15. The method of claim 13 , where the piezoelectric neurostimulation device comprises a piezoelectric material and at least one semiconductor diode or diode array.

16. The method of claim 13 , further comprising:
emitting with the ultrasound transmitter a first pulse of the ramped ultrasound output having a duration in the range of 1 to 10 microseconds;
detecting a second induced current in response to the first pulse in the biological tissue; and
using the detected second induced current from the first pulse as feedback to control an amplitude and/or duration of a second pulse having a duration in the range of 0.1 to 20 milliseconds sufficient to stimulate the biological tissue.

17. The method of claim 13 , wherein detecting the induced current in the biological tissue comprises:
detecting a first current on a skin surface corresponding to a first applied voltage in the piezoelectric neurostimulation device, where the first applied voltage is less than a threshold voltage of a voltage-limiting device; and
detecting a second current on the skin surface, where the second current corresponds to a second applied voltage in the piezoelectric neurostimulation device and where the second applied voltage is greater than the threshold voltage of the voltage-limiting device.

Assignees

• Towe Bruce C
• Univ Arizona State

Inventors

• Towe Bruce C

Classifications

• A61N1/36139 Primary

  with automatic adjustment · CPC title

• A61N1/37217

  characterised by the communication link, e.g. acoustic or tactile · CPC title

• A61N1/3787

  from an external energy source · CPC title

• A61N2007/0026

  Stimulation of nerve tissue · CPC title

• A61N7/00 Primary

  Ultrasound therapy (lithotripsy A61B17/22, A61B17/225; massage using supersonic vibration A61H23/00 {; using ultrasound for introducing media into the body A61M37/0092}) · CPC title