Surface electromyographic electrode assembly

• US 20030120329A1
• Filed: 11/07/2002
• Published: 06/26/2003
• Est. Priority Date: 11/07/2001
• Status: Active Grant

• Current Assignee: Kinesense, Inc.
• Original Assignee: Kinesense, Inc.
• Inventors: Getsla, Robert M., Simonyi, Victor F.
• Granted Patent: US 6,865,409 B2
• Time in Patent Office: Days
• US Class Current: 607/149
• CPC Class Codes: A61B 5/296 for electromyography [EMG]
• CPC Class Codes: A61N 1/0452 Specially adapted for transcutaneous muscle stimulation [TMS]
• CPC Class Codes: A61N 1/0492 Patch electrodes A61N1/0412, A61N1/0428 take precedence
• CPC Class Codes: Y10S 128/902 Biological signal amplifier

Abstract

An electrode assembly for use on a surface of biological tissue to measure bio-electric signals including an electrode apparatus having an electrode device adapted to directly contact the surface of the biological tissue. The electrode apparatus receives and transmits bio-electric signals measured across the biological tissue having a first voltage and a minute first current. A signal transmission line is included having a signal transmission conductor electrically coupled at one portion to the electrode device for transmission of the bio-electric signals. The transmission includes a second conductor electrically coupled to the amplifier apparatus and arranged to substantially shield the transmission conductor from ambient electric fields generated from sources external to the transmission line. A high impedance amplifier device is included having a signal input and a signal output. The signal input is electrically coupled to another portion of the signal transmission conductor for receipt of the transmitted bio-electric signals. The signal output is electrically coupled to the shield conductor, in a feedback loop, for receipt of at least a portion of the transmitted bio-electric signals, such that the voltage of the signals at the signal input of the high impedance amplifier device is maintained substantially equal to the voltage of the signals output from the signal output thereof.

Claims

1. A flexible, surface electromyographic electrode apparatus for use on a surface of biological tissue to measure bio-electric signals thereof, said electrode apparatus comprising:

a first conductive electrode device adapted to directly contact the surface of the biological tissue to receive and transmit bio-electric signals;

a first conductive guard device positioned substantially adjacent to and substantially over said electrode device such that the measured bio-electric signal passing therethrough is substantially shielded from ambient electric fields generated from sources external to said electrode apparatus; and

a substantially non-conductive, flexible, first sheet material positioned between said electrode device and said guard device to substantially prevent conductive contact therebetween.

2. The electrode apparatus according to claim 1, wherein

said conductive electrode device includes a contact portion adapted to directly contact the surface of the biological tissue, and a signal transmission portion carrying the bio-electric signal and electrically coupled to the contact portion.

3. The electrode apparatus according to claim 2, further including:

a substantially non-conductive, flexible, second sheet material positioned between said contact portion and said signal transmission portion to substantially prevent conductive contact therebetween; and

a conductive lead extending through said second sheet material to electrically couple the contact portion to the signal transmission portion.

4. The electrode apparatus according to claim 3, further including:

a substantially non-conductive, flexible, third sheet material positioned over said conductive guard device and mounted to said first sheet material in a manner enclosing said guard device therebetween, and said first sheet material being mounted to said second sheet material in a manner enclosing said signal transmission portion of the electrode device therebetween.

5. The electrode apparatus according to claim 2, wherein

said contact portion of said electrode device includes a contact footprint, and said signal transmission portion of said electrode device includes a signal transmission footprint, and

said guard device includes a guard conductor portion having a guard conductor footprint, and a shield conductor portion having a shield conductor footprint, said guard device being positioned and oriented such that when the electrode apparatus is operably mounted on the biological tissue, the guard conductor footprint of the guard conductor portion at least extends over the contact footprint of the electrode contact portion, and the shield conductor footprint of the shield conductor at least extends over the signal transmission footprint of said electrode signal transmission portion.

6. The electrode apparatus according to claim 5, wherein

said guard conductor footprint of said guard conductor portion extends beyond the contact footprint of said contact portion.

7. The electrode apparatus according to claim 6, further including:

a substantially non-conductive, flexible, second sheet material positioned between said contact portion and said signal portion to substantially prevent conductive contact therebetween; and

a conductive lead extending through said second sheet material to electrically couple the contact portion to the signal transmission portion.

8. The electrode apparatus according to claim 7, further including:

a substantially non-conductive, flexible, third sheet material positioned over said conductive guard device and mounted to said first sheet material in a manner enclosing said guard device therebetween, and said first sheet material being mounted to said second sheet material in a manner enclosing said signal portion of the electrode device therebetween.

9. The electrode apparatus according to claim 1, further including:

a second conductive electrode device adapted to directly contact the surface of the biological tissue, at a location spaced-apart from said first conductive electrode device, to receive and transmit a respective bio-electric signal;

a second conductive guard device positioned substantially adjacent and substantially over said second conductive electrode device such that the respective measured bio-electric signal passing therethrough is substantially shielded from ambient electric fields generated from said sources external to said electrode apparatus; and

said first sheet material further positioned between said second conductive electrode device and said second conductive guard device to substantially prevent conductive contact therebetween.

10. The electrode apparatus according to claim 9, wherein

said first conductive electrode device and said second conductive electrode device each having a respective contact portion adapted to directly contact the surface of the biological tissue, and a respective signal portion carrying the respective bio-electric signal and electrically coupled to the respective contact portion thereof.

11. The electrode apparatus according to claim 10, further including:

a substantially non-conductive, flexible, second sheet material positioned between the respective contact portion and the respective signal portion to substantially prevent conductive contact therebetween; and

a respective conductive lead extending through said second sheet material to electrically couple the respective contact portion to the respective signal portion.

12. The electrode apparatus according to claim 11, wherein

each said contact portion of the first and second electrode device includes a respective contact footprint, and each said signal transmission portion of the first and second electrode device includes a respective signal transmission footprint, and

each said guard device includes a respective guard conductor portion having a respective guard conductor footprint, and a respective shield conductor portion having a respective shield conductor footprint, each respective guard device being positioned and oriented such that when the electrode apparatus is operably mounted on the biological tissue, the respective guard conductor footprint of the respective guard conductor portion at least extends over the respective contact footprint of the respective electrode contact portion, and the respective shield conductor footprint of the respective shield conductor at least extends over the respective signal transmission footprint of the respective electrode signal transmission portion.

13. The electrode apparatus according to claim 12, wherein

each guard conductor footprint of the respective guard conductor portion extends beyond the respective contact footprint of the respective contact portion.

23. The electrode assembly according to claim 1, wherein

said conductive electrode device includes a contact portion adapted to directly contact the surface of the biological tissue, and a signal transmission portion carrying the bio-electric signals and having one end electrically coupled to the contact portion, and an opposite end electrically coupled to the inner conductor of the co-axial cable.

24. The electrode assembly according to claim 2, further including:

a substantially non-conductive, flexible, second sheet material positioned between said contact portion and said signal transmission portion to substantially prevent conductive contact therebetween; and

a conductive lead extending through said second sheet material to electrically couple the contact portion to the signal transmission portion.

25. The electrode assembly according to claim 3, further including:

a substantially non-conductive, flexible, third sheet material positioned over said conductive guard device and mounted to said first sheet material in a manner enclosing said guard device therebetween, and said first sheet material being mounted to said second sheet material in a manner enclosing said signal transmission portion of the electrode device therebetween.

26. The electrode assembly according to claim 2, wherein

said contact portion of said electrode device includes a contact footprint, and said signal transmission portion of said electrode device includes a signal transmission footprint, and

said guard device includes a guard conductor portion and a shield conductor portion having one end electrically coupled to the guard conductor portion, and an opposite end electrically coupled to the outer conductor of the co-axial cable, said guard conductor having a guard conductor footprint, and a shield conductor portion having a shield conductor footprint, said guard device being positioned and oriented such that when the electrode apparatus is operably mounted on the biological tissue, the guard conductor footprint of the guard conductor portion at least extends over the contact footprint of the electrode contact portion, and the shield conductor footprint of the shield conductor at least extends over the signal transmission footprint of said electrode signal transmission portion.

27. The electrode assembly according to claim 1, wherein

said electrode apparatus includes a number of conductive electrode devices each adapted to directly contact the surface of the biological tissue, at locations spaced-apart from one another, each electrode device being adapted to receive and transmit respective bio-electric signals;

a number of conductive guard devices each positioned substantially adjacent and substantially over a respective, corresponding conductive electrode device such that the respective measured bio-electric signals passing therethrough are substantially shielded from ambient electric fields generated from said sources external to said electrode apparatus; and

said first sheet material further positioned between said number of conductive electrode devices and said number of conductive guard devices to substantially prevent conductive contact therebetween.

28. The electrode assembly according to claim 6, wherein

each said conductive electrode device having a respective contact portion adapted to directly contact the surface of the biological tissue, and a respective signal transmission portion carrying the respective bio-electric signals and electrically coupled to the respective contact portion thereof.

29. The electrode assembly according to claim 7, further including:

a substantially non-conductive, flexible, second sheet material positioned between the respective contact portion and the respective signal transmission portion to substantially prevent conductive contact therebetween; and

a respective conductive lead extending through said second sheet material to electrically couple the respective contact portion to the respective signal transmission portion.

30. The electrode assembly according to claim 8, wherein

each respective contact portion of the respective electrode device includes a respective contact footprint, and each respective signal transmission portion of the respective electrode device includes a respective signal transmission footprint, and

each respective guard device includes a respective guard conductor portion having a respective guard conductor footprint, and a respective shield conductor portion having a respective shield conductor footprint, each respective guard device being positioned and oriented such that when the electrode apparatus is operably mounted on the biological tissue, the respective guard conductor footprint of the respective guard conductor portion at least extends over the respective contact footprint of the respective electrode contact portion, and the respective shield conductor footprint of the respective shield conductor at least extends over the respective signal transmission footprint of the respective electrode signal transmission portion.

31. The electrode assembly according to claim 9, wherein

each guard conductor footprint of the respective guard conductor portion extends beyond the respective contact footprint of the respective contact portion.

14. An electrode assembly for use on a surface of biological tissue to measure bio-electric signals thereof, said electrode assembly comprising:

an electrode apparatus having an electrode device adapted to directly contact the surface of the biological tissue to receive and transmit original bio-electric signals sensed from the biological tissue having an original first voltage and an original minute first current;

a shielded signal transmission line having a signal transmission conductor electrically coupled at one portion to the electrode device for transmission of said bio-electric signals, and a shield conductor electrically coupled to the electrode apparatus and arranged to substantially shield the transmission line from ambient electric fields generated from sources external to said transmission line;

a high impedance amplifier device having a signal input and a signal output, said signal input being electrically coupled to another portion of the signal transmission conductor for receipt of the transmitted bio-electric signals, said signal output being electrically coupled to the shield conductor, in a feedback loop, for receipt of at least a portion of the transmitted bio-electric signals, such that the voltage of the signals at said signal input of the high impedance amplifier device is maintained substantially equal to the voltage of the signals output from said signal output thereof.

15. The electrode assembly according to claim 14, wherein

said high impedance amplifier has a relatively high impedance in the range of about 10⁸ ohms to about 10¹⁰ ohms.

16. The electrode assembly according to claim 14, further including:

a low impedance amplifier device having a signal input and a signal output, said signal input being electrically coupled to the signal output of the high impedance amplifier device for receipt of substantially the remaining portion of the transmitted bio-electric signals.

17. The electrode assembly according to claim 16, wherein

said high impedance amplifier and said low impedance amplifier have relative high and low impedance, respectively, such that the bio-electric signals delivered from said output of said high impedance amplifier have a second current increased over said first minute current, and a second voltage substantially similar to the original first voltage of the original bio-electric signals.

18. The electrode assembly according to claim 17, wherein

said high impedance amplifier has a relatively high impedance in the range of at least about 10⁸ ohms to at least about 10¹⁰ ohms, and

said low impedance amplifier may have an impedance in the same range of about 10⁴ ohms to about 10⁶ ohms.

19. The electrode assembly according to claim 18, wherein

said first minute current of the original bio-electric signals is in the range of about 10⁻

14 amps to about 10<sup>−

12</sup> amps, while the second current is in the range of about 10<sup>−

9</sup> amps to about 10<sup>−

6</sup> amps, and

said first original voltage of the original bio-electric signals is in the range of about 10<sup>−

5</sup> volts to about 10<sup>−

3</sup> volts, while the second voltage current is in the range of about 10<sup>−

3</sup> volts to about 10<sup>−

1</sup> volts.

20. The electrode assembly according to claim 14, wherein

said shielded transmission line includes a shield cable wherein said signal transmission conductor is the central conductor, and said shield conductor is the outer conductor.

21. The electrode assembly according to claim 14, wherein

said electrode assembly includes a guard shield situated over said electrode device to substantially shield the electrode device from said ambient electric fields generated from sources external thereto.

22. An electromyographic surface electrode assembly for use on a surface of biological tissue to measure bio-electric signals thereof, said electrode assembly comprising:

a flexible, surface electromyographic electrode apparatus including

a conductive electrode device adapted to directly contact the surface of the biological tissue to receive and transmit bio-electric signals sensed from the biological tissue having an original first voltage and an original minute first current;

a conductive guard device positioned substantially adjacent and substantially over said electrode device such that the measured bio-electric signal passing therethrough is substantially shielded from ambient electric fields generated from sources external to said electrode apparatus; and

a substantially non-conductive, flexible, first sheet material positioned between said electrode device and said guard device to substantially prevent conductive contact therebetween;

a co-axial cable having an inner conductor and an outer conductor shielding the inner conductor, at one portion of said co-axial cable, said inner conductor being electrically coupled to the electrode device for transmission of said bio-electric signals, and said outer conductor being electrically coupled to the guard device to substantially shield the inner conductor from said ambient electric fields generated from sources external thereto; and

a buffer amplifier device having a signal input and a signal output, said signal input being electrically coupled to the inner conductor of the co-axial cable at another portion thereof for receipt of the transmitted bio-electric signals, said signal output being electrically coupled to the outer conductor of the co-axial cable, in a feedback loop, for receipt of at least a portion of the transmitted bio-electric signals, such that the voltage of the signals at said signal input of the high impedance amplifier device is maintained substantially equal to the voltage of the signals output from said signal output thereof.

32. The electrode assembly according to claim 22,further including:

a low impedance amplifier device having a signal input and a signal output, said signal input being electrically coupled to the signal output of the high impedance amplifier device for receipt of substantially the remaining portion of the transmitted bio-electric signals

33. The electrode assembly according to claim 32, wherein

said high impedance amplifier and said low impedance amplifier have relative high and low impedance, respectively, such that the bio-electric signals delivered from said output of said high impedance amplifier have a second current increased over said first minute current, and a second voltage substantially similar to the original first voltage of the original bio-electric signals.

34. The electrode assembly according to claim 33, wherein

said high impedance amplifier has a relatively high impedance in the range of at least about 10⁸ ohms to at least about 10¹⁰ ohms, and

said low impedance amplifier may have an impedance in the same range of about 10⁴ ohms to about 10⁶ ohms.

35. The electrode assembly according to claim 34, wherein

said first minute current of the original bio-electric signals is in the range of about 10⁻

14 amps to about 10<sup>−

12</sup> amps, while the second current is in the range of about 10<sup>−

9</sup> amps to about 10<sup>−

6</sup> amps, and

said first original voltage of the original bio-electric signals is in the range of about 10<sup>−

5</sup> volts to about 10<sup>−

3</sup> volts, while the second voltage current is in the range of about 10<sup>−

3</sup> volts to about 10⁻

volts.