Method and apparatus for reducing noise in brain signal measurements

• US 20100274153A1
• Filed: 06/25/2010
• Published: 10/28/2010
• Est. Priority Date: 06/25/2010
• Status: Active Grant

• Current Assignee: Magstim Group, Incorporated
• Original Assignee: Electrical Geodesics, Inc. (Koninklijke Philips N.V.)
• Inventors: Tucker, Don M. SR., Tucker, Don M.
• Granted Patent: US 8,494,624 B2
• Time in Patent Office: Days
• US Class Current: 600/544
• CPC Class Codes: A61B 2562/046 in a matrix array
• CPC Class Codes: A61B 5/369 Electroencephalography [EEG] devices for psychotechnics A61B5/16
• CPC Class Codes: A61B 5/6814 Head
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: A61B 5/7207 of noise induced by motion artifacts

Abstract

A method and apparatus for reducing noise in brain signal measurements. The method provides an array of sensors providing for spatial oversampling, and multiple samplings over time to produce measurement data. The measurement data have a variance common to the sensors, and a remaining variance that can be safely assumed to be sensor or channel specific noise and that is accounted for by a suitable modification of the measurement data. The apparatus provides clusters of the sensors positioned in correspondence to the vertices of substantially equilateral triangles that are defined by tensile elements connecting the clusters.

Claims

1. A method for reducing or eliminating noise in an electrical or magnetic signal produced by an organ in the body, the signal having a highest spatial frequency component of X cycles per unit measure of distance, the method comprising:

providing, on or outside the exterior surface of the body, an array of sensors, each of said sensors for independently measuring the signal, wherein the sensors are spaced apart from one another by at least a minimum spacing of ½

•

X<sup>−

1</sup>;

sampling the signal, by each sensor, at a plurality of different times, so as to produce, for each sensor, a set of time-dependent measurements of the signal;

identifying a first variance in the measurements corresponding to a selected sensor that is common to the measurements corresponding to all of the other sensors;

identifying a remaining variance in the measurements corresponding to the selected sensor; and

removing from the measurements corresponding to the selected sensor a second variance that is determined, at least in part, by said remaining variance, so as to reduce or eliminate noise that is unique to the measurements of the selected sensor.

2. The method of claim 1, wherein said step of providing includes providing at least 256 sensors in said array.

3. The method of claim 2, the method further comprising disposing said sensors on the head of the body, to measure a brain signal.

4. The method of claim 3, the method further comprising solving the inverse problem after performing said step of subtracting.

5. The method of claim 4, further comprising specifying said second variance to be substantially equal to said remaining variance.

6. The method of claim 1, further comprising specifying said second variance to be substantially equal to said remaining variance.

7. An apparatus for reducing or eliminating noise in an electrical or magnetic signal produced by an organ in the body, comprising:

an array of first sensors, each first sensor for independently measuring the signal, wherein, within a first predetermined set of three of said first sensors, the first sensors thereof are connected to each other by three separate tensile connecting elements defining a substantially equilateral “

geodesic”

triangle, with the first sensors of said first predetermined set corresponding to vertices of said geodesic triangle; and

an array of second sensors, each second sensor for independently measuring said signal, wherein a predetermined second set of said second sensors is associated with a respective one of the sensors of said first set, defining a cluster of first and second sensors, the sensors of said cluster being connected to each other by a common structure, wherein the second sensors of said cluster are all closer to the first sensor of said cluster than to either of the remaining sensors of said first set.

8. The apparatus of claim 7, wherein said cluster has exactly six of said second sensors.

9. The apparatus of claim 8, wherein the second sensors of said cluster are distributed about the first sensor of said cluster so as to define the vertices of a hexagon.

10. The apparatus of claim 7, wherein said cluster has exactly five of said second sensors.

11. The apparatus of claim 10, wherein the second sensors of said cluster are distributed about the first sensor of said cluster so as to define the vertices of a pentagon.

12. The apparatus of claim 7, wherein each of said tensile elements has a flexibility sufficient to allow for an elastically recoverable elongation of at least 20%.

13. The apparatus of claim 12, wherein said common structure has a rigidity sufficient to support the sensors of said cluster in fixed positions relative to each other during use of the apparatus.

14. The apparatus of claim 7, wherein said common structure has a rigidity sufficient to support the sensors of said cluster in fixed positions relative to each other during use of the apparatus.

15. The apparatus of claim 7, comprising sixteen geodesic triangles, defined by a corresponding fifteen of said first sensors.

16. The apparatus of claim 15, wherein each of said fifteen first sensors is part of an associated cluster of said second sensors.

17. The apparatus of claim 16, wherein each of said associated clusters includes at least five of said second sensors.

18. The apparatus of claim 7, comprising at least 256 of said first sensors, wherein each of said 256 first sensors is part of a cluster of sensors that includes 3 of said second sensors.

19. The apparatus of claim 7, comprising at least 256 of said first sensors, wherein each of said 256 first sensors is part of a cluster of sensors that includes 4 of said second sensors.

20. The apparatus of claim 7, comprising at least 256 of said first sensors, wherein each of said 256 first sensors is part of a cluster of sensors that includes 5 of said second sensors.

21. The apparatus of claim 7, comprising at least 256 of said first sensors, wherein each of said 256 first sensors is part of a cluster of sensors that includes 6 of said second sensors.