SCALP POTENTIAL MEASURING METHOD AND APPARATUS

• US 20100145217A1
• Filed: 06/23/2008
• Published: 06/10/2010
• Est. Priority Date: 06/22/2007
• Status: Active Grant

• Current Assignee: Wenco International Mining Systems Ltd.
• Original Assignee: CMTE Development Limited
• Inventors: Bongers, Daniel R., Otto, Edward J.
• Granted Patent: US 8,862,218 B2
• Time in Patent Office: Days
• US Class Current: 600/544
• CPC Class Codes: A61B 5/30 Input circuits therefor
• CPC Class Codes: A61B 5/369 Electroencephalography [EEG] devices for psychotechnics A61B5/16
• CPC Class Codes: A61B 5/6814 Head
• CPC Class Codes: A61B 5/7225 Details of analog processing, e.g. isolation amplifier, gain or sensitivity adjustment, filtering, baseline or drift compensation A61B5/30, A61B5/316 take precedence; transformers for specific applications H01F38/00; amplifiers H03F

Abstract

An apparatus for measuring scalp potential is disclosed, which comprises a plurality of sensors and a pre-amplifier coupled to these sensors. The sensors are adapted to measure a raw scalp potential measurement though a hair and air interface, and may be considered as a difference, reference or common measurement. The interface presents a high and variable source impedance coupling to the scalp. The pre-amplifier is adapted to have an input impedance significantly higher than that presented by the source interface, and receives the raw scalp potential measurement to produce a pre-amplified scalp potential measurement.

Claims

1. An apparatus for scalp potential measuring comprising:

a plurality of sensors adapted to measure a raw scalp potential measurement though a hair and air interface;

said interface presenting a high and variable source impedance coupling to said scalp; and

a plurality of preamplifiers coupled to a respective one of said sensors;

wherein each said preamplifier is adapted to have an input impedance significantly higher than the impedance presented by said sensor source interface;

wherein said preamplifier receives said raw scalp potential measurement and produces a preamplified scalp potential measurement for producing a pre-amplified scalp potential measurement.

2. An apparatus according to claim 1 wherein said sensor source interface impedance is presented by any contact medium, scalp, and underlying tissues.

3. An apparatus according to any one of the preceding claims wherein said input impedance is active and increased by the application of feedback.

4. An apparatus according to any one of the preceding claims wherein said preamplifier includes a wideband high impedance input, and an active biasing network, adapted to present an input impedance of greater than 10 Peta-Ohms from 0.01 Hz to 400 Hz.

5. An apparatus according to any one of the preceding claims wherein said preamplifier includes a high-gain low-noise rail-to-rail FET input operational amplifier with an input impedance of 10 Tera Ohms and a shielded feedback and biasing network for presenting said input impedance.

6. An apparatus according to any one of the preceding claims, further comprising:

a common mode filter amplifier coupled to said pre-amplifier, wherein said common mode filter is adapted to cancel a substantial component of common mode signal and noise included in said pre-amplified scalp potential measurement thereby to produce a common mode cancelled scalp potential measurement; and

an RF suppression system for suppressing RF noise of said common mode cancelled scalp potential measurement to produce an RF suppressed scalp potential measurement.

7. An apparatus according to claim 6, wherein said common mode filter amplifier and said RF suppression system are adapted to preserve a substantially common gain, phase and delay across each scalp potential measurement signal path.

8. An apparatus according to claim 6 or claim 7, further comprising:

a differential amplifier system for amplifying said RF suppressed scalp potential measurement to produce an amplified scalp potential measurement; and

;

a band pass filter for filtering said amplified scalp potential measurement to substantially minimise aliasing effects during subsequent digitisation.

9. An apparatus according to claim 8, wherein said differential amplifier system and said band pass filter are adapted to preserve a substantially common gain, phase and delay across said each scalp potential measurement signal path.

10. An apparatus according to claim 8 or claim 9 wherein said band pass filter is in the form of a low frequency transient high pass filter and a high frequency anti-aliasing low pass filer.

11. An apparatus according to any one of claims 8 to 10 wherein said band pass filter is adapted to provide suitable low frequency transient suppression and further adapted to provide attenuation greater than half a quantisation level at a Nyquist frequency for a predetermined analog-to-digital converter.

12. An apparatus according to any one of claims 8 to 11 wherein said band pass filter is a sixth order symmetrical band pass filtering amplifier with a pass band of 1 Hz to 40 Hz.

13. An apparatus according to any one of claims 8 to 12, wherein an input to said differential amplifier is selectable from any one of a set of signals including a common reference signal, an averaged signal and a pre-amplified and buffered sensor signal.

14. An apparatus according to any one of the preceding claims further comprising:

a digitiser for digitising one or more scalp potential measurements; and

a first processor for performing signal processing on said one or more scalp potential measurements and producing an output signal.

15. An apparatus according to claim 14, wherein said output signal is transmitted wirelessly to a second processor.

16. An apparatus according to any one of the preceding claims further including a channel interconnection module adapted to suppress inter-channel RF interference between each scalp potential measurement signal path.

17. An apparatus according to claim 16 wherein said channel interconnection module is adapted to select a scalp potential measurement mode from the set comprising:

channel to reference-channel mode, channel to channel-average mode and channel to channel differential mode.

18. A method for scalp potential measuring comprising the steps of:

receiving raw scalp potential measurement at said sensor wherein said measurement is taken though hair and air; and

pre-amplifying said raw scalp potential measurement with a high input impedance amplifier to produce a pre-amplified scalp potential measurement.

19. A method according to claim 18 further comprising the steps of:

cancelling a substantial component common mode signal and noise of said pre-amplified scalp potential measurement to produce a common mode cancelled scalp potential measurement; and

suppressing RF noise of said common mode cancelled scalp potential measurement to produce an RF suppressed scalp potential measurement.

20. A method according to claim 18 or claim 19 further comprising the step of amplifying said RF suppressed scalp potential measurement to produce an amplified scalp potential measurement for digitisation.

21. A method according to claim 20 further comprising the steps of:

applying a band pass transient and anti-aliasing filtering of said amplified scalp potential measurement to produce an anti-aliased scalp potential measurement for digitisation;

digitising said anti-aliased scalp potential measurement to produce a sequence of digitised scalp potential values.

processing said sequence of digitised scalp potential values to produce a scalp potential waveform signal; and

producing a measurement waveform.

22. A method according to any one of claims 18 to 21 further comprising the step of transmitting an output signal over a wireless connection for receiving by a second processor.

23. A method according to any one of claims 18 to 22 wherein said receiving raw scalp potential measurement is measured though a hair and air interface;

said interface presenting a high and variable source impedance coupling to said scalp; and

said pre-amplifier is adapted to have an input impedance significantly higher than the presented said source interface.

24. A method according to claim 23 wherein said input impedance is active and increased by the step of applying feedback.

25. A method for scalp potential measuring comprising the steps of:

receiving an input raw scalp potential signal from a plurality of sensors for defining a respective plurality of channels;

selecting a measurement mode configuration from a set comprising;

channel to reference-channel mode, channel to channel-average mode and channel to channel differential mode;

biasing said input signal while maintaining high input impedance;

matching channel gain before differentially deriving a channel signal;

suppressing radio frequency interference of said channel signal while maintaining gain and phase matching as a further step in providing a processed channel signal;

suppressing common mode signal interference of said channel signal as a further step in providing said processed channel signal;

band pass filtering said channel signal as a further step in providing said processed channel signal; and

digitising said processed channel signal for providing a digital scalp potential measurement signal indicative of said input signal measured according to said selected measurement mode.

26. A method according to claim 25 wherein said high input impedance is provided by a pre-amplifier including a high input impedance amplifier for amplifying said raw scalp potential measurement to produce a pre-amplified scalp potential measurement.

27. A method according to claim 26 wherein said input impedance is significantly higher than the impedance associated with a source interface presented to said sensor.

28. An apparatus according to claim 27 wherein said source interface impedance is presented by any contact medium, scalp, and underlying tissues.

29. A method according to any one of claims 26 to 28, wherein said input impedance is active and increased by the application of feedback.

30. A method according to any one of claims 26 to 29, wherein said preamplifier includes a wideband high impedance input, and an active biasing network, adapted to present an input impedance of greater than 10 Peta-Ohms from 0.01 Hz to 400 Hz.