Method and Apparatus to Provide Safety Checks for Neural Stimulation

• US 20080177356A1
• Filed: 10/29/2007
• Published: 07/24/2008
• Est. Priority Date: 04/28/2006
• Status: Active Grant

• Current Assignee: Second Sight Medical Products, Inc.
• Original Assignee: Second Sight Medical Products, Inc.
• Inventors: Greenberg, Robert Jay, Roy, Arup, Zhou, Dao Min, Little, James Singleton, McClure, Kelly Hobart, Tang, Kea-Tiong, Reinhold, John, Yadav, Sumit, Zhou, Chunhong, Maksy, Pishoy, Castro, Richard Agustin, Dai, Rongqing
• Granted Patent: US 8,170,682 B2
• Time in Patent Office: Days
• US Class Current: 607/63
• CPC Class Codes: A61N 1/00 Electrotherapy; Circuits therefor A61N2/00 takes precedence; irradiation apparatus A61N5/00
• CPC Class Codes: A61N 1/0543 Retinal electrodes
• CPC Class Codes: A61N 1/0551 Spinal or peripheral nerve electrodes
• CPC Class Codes: A61N 1/08 Arrangements or circuits for monitoring, protecting, controlling or indicating for external stimulators A61N1/3603; for implantable neurostimulators A61N1/36128; for heart stimulators A61N1/37; for defibrillators A61N1/3925
• CPC Class Codes: A61N 1/3603 Control systems
• CPC Class Codes: A61N 1/36046 of the eye
• CPC Class Codes: A61N 1/36142 for improving safety
• CPC Class Codes: A61N 1/36185 Selection of the electrode configuration

Abstract

The present application deals generally with the stimulation of neural tissue by electronic means and specifically with controlling the level of electrical stimulation in order to prevent damage to the neural tissue. Methods presented in the disclosure include detecting current leakage via electrode impedance measurement, electrode capacitance measurement, and testing the electrode response to test current pulse. Apparatus presented in the disclosure include circuitry and systems capable of performing the methods disclosed.

Claims

1. An apparatus for controlling the stimulation of neural tissue comprising:

a neural stimulator;

at least one electrode driven by the neural stimulator and suitable to stimulate neural tissue;

a current pulse generator for stimulating neural tissue in accordance with external input;

a meter device for testing total power dissipation of said neural stimulator;

a calculating device for comparing said total power dissipation to a predetermined maximum power dissipation.

2. The apparatus according to claim 1, wherein the meter device is an RF power control loop.

3. The apparatus according to claim 1, wherein the meter device is a thermistor in the neural stimulator.

4. A method of controlling the stimulation of neural tissue comprising:

providing a neural stimulator driving at least one electrode suitable to stimulate neural tissue;

providing a test current pulse to an electrode of the at least one electrode;

taking at least one measurement of an IR drop voltage across said electrode;

calculating a pre-short maximum voltage from at least one IR drop voltage measurement; and

comparing the pre-short maximum voltage to a threshold leakage voltage value.

5. The method according to claim 4, further comprising

determining if the at least one electrode needs to be shut down based on the comparing and

shutting down the at least one electrode if the determining step determines that at the least one electrode needs to be shut down.

6. The method according to claim 4, further comprising

calculating resistances of the at least one electrode from at least the IR drop voltage measurements and the biphasic current pulses,

wherein the threshold leakage voltage value is calculate using the resistances of the at least one electrode.

7. The method according to claim 4, wherein the test current pulses are biphasic, comprising an anodic pulse and a cathodic pulse.

8. The method according to claim 7, wherein the test current pulses are configured such that the duration of the anodic pulse is equal to the duration of the cathodic pulse and equal to the duration between the anodic and cathodic pulses.

9. The method according to claim 8, further comprising:

providing at least one biphasic stimulating current pulse to stimulate neural tissue, wherein the test current pulses are of shorter pulse duration and lower maximum current than any biphasic stimulating current pulse.

10. A neural stimulator comprising:

a neural stimulation controller;

a current pulse generator;

at least one electrode driven by said neural stimulation controller and suitable to stimulate neural tissue;

a meter device for taking at least one measurement of an IR drop across each of the at least one electrode when subjected to a test current pulse.

11. The apparatus according to claim 10, further comprising a calculating device for calculating a resistance for each of the at least one electrode and for calculating a threshold leakage voltage value for each of the at least one electrode and for comparing the threshold leakage voltage values to a baseline voltage.

12. The apparatus according to claim 11, further comprising a data storage device for storing at least the threshold leakage voltage value.

13. The apparatus according to claim 12, wherein the data storage device is also capable of storing data related to the IR drop measurement that exceed the threshold leakage voltage value.

14. The apparatus according to claim 10, further comprising

one or more drivers controlled by the neural stimulation controller,

wherein the at least one electrode is driven by the one or more drivers.

15. The apparatus according to claim 14, wherein the neural stimulation controller is capable of shutting down the one or more drivers if the baseline voltage over an electrode exceeds the threshold leakage voltage value.