WO2018102855A1 - Bioamplificateur et système de mesure d'impédance - Google Patents

Bioamplificateur et système de mesure d'impédance Download PDF

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Publication number
WO2018102855A1
WO2018102855A1 PCT/AU2017/000263 AU2017000263W WO2018102855A1 WO 2018102855 A1 WO2018102855 A1 WO 2018102855A1 AU 2017000263 W AU2017000263 W AU 2017000263W WO 2018102855 A1 WO2018102855 A1 WO 2018102855A1
Authority
WO
WIPO (PCT)
Prior art keywords
electrodes
amplifier
biological
contact impedance
sensor
Prior art date
Application number
PCT/AU2017/000263
Other languages
English (en)
Inventor
Boris SHARFF
John Paul Mckeown
Aaron Russell
Original Assignee
Visionsearch Pty Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from AU2016905027A external-priority patent/AU2016905027A0/en
Application filed by Visionsearch Pty Limited filed Critical Visionsearch Pty Limited
Publication of WO2018102855A1 publication Critical patent/WO2018102855A1/fr

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Classifications

    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/68—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient
    • A61B5/6801—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient specially adapted to be attached to or worn on the body surface
    • A61B5/6843—Monitoring or controlling sensor contact pressure
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/24—Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/24—Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
    • A61B5/25—Bioelectric electrodes therefor
    • A61B5/276—Protection against electrode failure
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/05—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves 
    • A61B5/053—Measuring electrical impedance or conductance of a portion of the body
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/24—Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
    • A61B5/30—Input circuits therefor

Definitions

  • the present invention relates to apparatus and methods for the continuous and concurrent, or real-time, measurement of the contact impedance between the skin of a subject and skin contacting electrodes for a biological amplifier used to detect, amplify and measure electrical activity of nerve cells of a physiological function, such as the subject's heart activity, general brain activity or optic nerve activity.
  • Electrodes are placed on the skin in the region of the heart; for general brain activity, electrodes are placed at various locations on the scalp; for somatosensory activity, electrodes are placed on the limbs or head or over the spine; and for optic nerve activity, electrodes are placed on the scalp above the visual cortex.
  • the contact impedance As the electrical signals generated by the nerve cells of each of the heart, brain and optic nerve are very small, it is vital that, in all situations, as efficient a contact as possible is achieved between the electrodes and the skin to obtain the best electrical signal which will provide the most accurate readings of electrical activity for the operator.
  • the measurement of the efficiency of this contact is a measurement of what is called the contact impedance.
  • operators measure the contact impedance when an electrode is initially placed in position on the skin above the nerve cells of interest. If the contact impedance is too high, then the electrode is reapplied as necessary with appropriate skin cleaning and conductive gel until the contact impedance is acceptably low.
  • the contact of the electrode to the skin subsequently deteriorates during the taking of the readings (the measurement)
  • the readings from the time of the deterioration are compromised because they do not take into account the change in the contact impedance.
  • the operator may not be aware of this until the taking of the readings has ended, at which point the readings are usually discarded, the electrode is reapplied so that contact impedance is acceptably low, and fresh readings are taken. Or, worse still, the operator may not become aware of the deterioration of the contact even after the taking of the readings has ended, and so the operator subsequently relies upon those readings.
  • a biological amplifier for measuring an electrical activity of nerve cells of a physiological function in a subject comprising:
  • a plurality of electrodes at least one of which is a sensor electrode for measuring the electrical activity, the or each sensor electrode adapted to be placed on the skin of the subject above the nerve cells, and
  • the contact impedance measuring means comprises a differential amplifier and the plurality of electrodes are connected to input terminals of the differential amplifier.
  • the plurality of electrodes comprise a sensor electrode and a reference electrode.
  • the plurality of electrodes may comprise a pair of sensor electrodes connected to the input terminals of the differential amplifier, and a reference electrode connected to the ground of the differential amplifier.
  • the plurality of electrodes comprise a plurality of sensor electrodes and a reference electrode connected to the input terminals of a plurality of differential amplifiers.
  • the plurality of electrodes comprise a plurality of pairs of sensor electrodes connected to the input terminals of a plurality of differential amplifiers, and a reference electrode connected to the ground of the differential amplifiers.
  • the biological amplifier further comprises an impedance voltage generator.
  • the output of the differential amplifier is connected to two different electronic circuits.
  • One circuit uses the signal for the biological or physiological measurement of interest, the other circuit uses the signal to take the contact impedance measurement.
  • Fig. 1 is a schematic representation of a biological amplifier in accordance with a first preferred embodiment of the invention, and which is being used to measure the electrical activity of the nerve cells of the brain of a subject, and in which a sensor electrode placed on the scalp of the subject and a reference electrode are used to measure the contact impedance between the scalp and the sensor electrode.
  • Fig. 2 is a schematic representation of a biological amplifier in accordance with a second preferred embodiment of the invention, and which is being used for a similar purpose to the biological amplifier of Fig. 1 , and in which a pair of sensor electrodes are used to measure contact impedance.
  • Fig. 3 is a schematic representation of a biological amplifier in accordance with a third preferred embodiment of the invention, and which is being used for a similar purpose to the biological amplifier of Fig. 1 , and in which a plurality of sensor electrodes and a reference electrode and a plurality of differential amplifiers are used to measure contact impedances of each of the sensor electrodes.
  • Fig. 4 is a schematic representation of a biological amplifier in accordance with a fourth preferred embodiment of the invention, and which is being used for a similar purpose to the biological amplifier of Fig. 2, and in which a plurality of pairs of sensor electrodes are used to measure contact impedance.
  • Each of the biological amplifiers 10, 12, 14, 16 shown in Figs. 1 to 4 receives signal inputs from electrodes attached to the skin of a subject 18, and has a contact impedance measuring means that operates to measure each electrode's contact impedance continuously and concurrently with the amplifier's function of detection, amplification and measurement of electrical activity of nerve cells of a physiological function.
  • Zs an impedance 22
  • a sensor electrode 24 also termed a unipolar electrode
  • the sensors 24, 26 are connected to inputs of a differential amplifier 28 of the contact impedance measuring means.
  • the sensor electrode 24 is placed on the skin of the subject's scalp above the nerve cells of interest, and the reference electrode 26 is placed in contact with the subject's ear lobe.
  • the differential amplifier 28 amplifies the difference between two voltages. By connecting the voltage signal from sensor electrode 24 onto one input terminal 30 of the differential amplifier and connecting the voltage signal from reference electrode 26 onto the other input terminal 32 of the differential amplifier, the resultant output voltage will be proportional to the difference between the two input voltage signals.
  • the differential amplifier 28 is provided with power by connection of its own ground 34 to the reference ground of the biological amplifier 10 and by connection of its supply voltage through supply terminal 36 to the internal power of the biological amplifier 10. This
  • a unipolar measurement is termed a unipolar measurement.
  • the resultant voltage between the sensor electrode 24 and the reference electrode 26 is measured to provide the unipolar measurement.
  • the amplitude of this resultant voltage is a measurement that is proportional to the sum of the contact impedance of the sensor electrode 24 (herein termed Ze) plus the contact impedance of its associated reference electrode 26 (herein termed Zr) plus the impedance through the subject's body between the two electrodes 24, 26 (herein termed Zb).
  • the impedance Zs in series with the total impedance Ze+Zr+Zb act as a voltage divider through which the measuring current flows.
  • the impedance Zb is small in comparison to other impedances and can be neglected for the purposes of this invention.
  • the biological amplifier 14 shown in Fig. 3 has a plurality of sensor electrodes 24, 38 and a reference electrode 26 and a plurality of differential amplifiers 28, 40 which are used to measure contact impedances of each of the sensor electrodes.
  • the resultant voltage between each sensor electrode 24, 38 and the reference electrode 26 is measured to provide a plurality of unipolar measurements.
  • a second sensor electrode 42 may be connected to the differential amplifier 28 when a differential measurement (i.e. bipolar measurement) is being taken.
  • the reference electrode 26 in this case is connected to the reference ground 48 of the differential amplifier 28. This is termed a single bipolar measurement.
  • the biological amplifier 16 shown in Fig. 4 has a plurality of pairs of sensor electrodes 24, 42 and 50, 44 and a reference electrode 26 and a plurality of differential amplifiers 28, 52 which are used to measure contact impedances of each of the sensor electrodes. This is termed a plurality of bipolar measurements.
  • the output of the or each differential amplifier is connected to two different electronic circuits 54, 56.
  • Circuit 56 uses the signal for the biological or physiological
  • circuit 54 uses the signal to take the contact impedance measurement.
  • the impedance voltage is separated from the biological signal voltage by frequency.
  • Biological signals of interest typically have frequencies below 100Hz, and a useful impedance signal has a frequency of many multiples of typical biological signal frequencies, and so the two measurements (of impedance and of nerve cell electrical activity) can be separated by frequency filters 58.
  • the or each impedance voltage generator 20 provides a voltage that is at a frequency significantly above the biological signal frequency of interest, typically several octaves above that frequency, and is several tenths of a volt in amplitude.
  • This voltage source is joined to the sensor electrode of interest through an impedance Zs 22 that is of a value between one and several times the maximum acceptable contact impedance that is to be measured, typically from 5 kQ to 30kQ.
  • each sensor electrode is referenced to a single common negative reference electrode 26 (see Fig. 3). This negative reference electrode 26 is typically placed on the forehead or on the ear lobe (via an ear clip) for measurements on the head.
  • the reference electrode can be a set of electrodes that are meant to represent "zero potential" on the body below the head.
  • the reference point could be derived by summing voltages from electrodes on limbs (the arms or legs) and the central terminal ("CT") on the sternum. These are typically connected by 5 ⁇ resistors to provide the summing. This also provides a reference point to which other electrodes are referred.
  • the resultant voltage in a unipolar measurement between the sensor electrode and the reference electrode is proportional to the total contact impedance of these two electrodes to the skin.
  • the resultant voltage at the frequency of the impedance voltage generator between two sensor electrodes is a direct measurement of the total contact impedance of these two electrodes to the skin.
  • the reference electrode For unipolar measurements, the reference electrode has a large area and is attached to a clean, dry and exposed area of skin so that its contact impedance Zr is low, and the impedance Zb of the body is known to be small, and so the major component of the measured contact impedance is taken to be the contact impedance Ze between the unipolar sensor electrode and the skin.
  • the impedance that is measured is the sum of the contact impedance of both of the two electrodes. If an unacceptably high impedance is measured, then both electrodes will require attention as it is not known which one has, or if both have, a faulty contact.
  • the contact impedance of many sensor electrodes may be any contact impedance.
  • the biological amplifier of the present invention applies a contact impedance measuring signal to each bipolar connected pair of sensor electrodes in quick succession (i.e. multiplexed between each bipolar connected pair of sensor electrodes by means of a multiplexer frequency generator 64 and a multiplexer 66) and the contact impedance is correspondingly measured for each pair in turn.
  • the multiplexing ideally occurs at a frequency significantly above that of the contact impedance measurement frequency, such as from 10 to 20 times above, but not at a frequency that is an integer multiple above that of the contact impedance measurement in order to avoid aliasing.
  • This multiplexing provides a contact impedance measurement of a plurality of pairs of sensor electrodes in the same time as it takes to provide a contact impedance measurement on non-multiplexed sensor electrodes (e.g. a single pair of sensor electrodes connected as a bipolar pair or a single sensor electrode connected as unipolar).
  • the contact impedance measuring means may be functionally activated or deactivated by external controls from, for instance, an associated computer.
  • An immediate visual indication of an unacceptable level of contact impedance can be provided by an indicator light 66 for the or each sensor electrode, or by the software within the associated computer, or by both.
  • Use of indicator lights does not require the operator to request the software to take an impedance reading, and nor does it require that the operator even look at a control screen of the associated computer, as the indicator lights can be conveniently placed adjacent to the sensor electrodes themselves.
  • the present inventors have also developed an improved method of identifying a faulty electrode of a bipolar connected pair of sensor electrodes which are being used to measure the combined contact impedance of the bipolar connected pair. If the contact impedance of one sensor electrode of the bipolar connected pair is too high, it has previously been impossible to identify which one of the pair was responsible for the high measurement and was thus faulty.
  • the improved method involves applying a contact impedance
  • the three measurements of contact impedance obtained by the above method enable the operator to identify which sensor electrode of the bipolar connected pair is faulty, and yet still know the combined contact impedance of the bipolar connected pair of sensor electrodes.
  • the present invention has industrial application in the field of biological amplifiers for detecting, amplifying and measuring the electrical activity of nerve cells involved in the functioning of a physiological activity.

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  • Life Sciences & Earth Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Medical Informatics (AREA)
  • Biophysics (AREA)
  • Pathology (AREA)
  • Engineering & Computer Science (AREA)
  • Biomedical Technology (AREA)
  • Heart & Thoracic Surgery (AREA)
  • Physics & Mathematics (AREA)
  • Molecular Biology (AREA)
  • Surgery (AREA)
  • Animal Behavior & Ethology (AREA)
  • General Health & Medical Sciences (AREA)
  • Public Health (AREA)
  • Veterinary Medicine (AREA)
  • Measurement And Recording Of Electrical Phenomena And Electrical Characteristics Of The Living Body (AREA)

Abstract

L'invention concerne un amplificateur biologique (10) pour mesurer une activité électrique de cellules nerveuses d'une fonction physiologique chez un sujet (18), qui présente une pluralité d'électrodes (24, 26) dont au moins l'une est une électrode de capteur (24), pour mesurer l'activité électrique. L'électrode de capteur (24) est conçue pour être placée sur la peau du sujet au-dessus des cellules nerveuses. L'amplificateur biologique comprend également des moyens (20, 28, 56) pour mesurer l'impédance de contact entre la peau du sujet et l'électrode de capteur (24) due à une tension appliquée entre la pluralité d'électrodes. Le moyen de mesure d'impédance de contact fonctionne en continu et simultanément avec la mesure de l'activité électrique des cellules nerveuses de la fonction physiologique par l'amplificateur biologique.
PCT/AU2017/000263 2016-12-06 2017-12-06 Bioamplificateur et système de mesure d'impédance WO2018102855A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
AU2016905027 2016-12-06
AU2016905027A AU2016905027A0 (en) 2016-12-06 Bioamplifier and impedance measurement system

Publications (1)

Publication Number Publication Date
WO2018102855A1 true WO2018102855A1 (fr) 2018-06-14

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111728612A (zh) * 2020-06-05 2020-10-02 武汉励石医疗科技有限责任公司 生物电阻抗测量方法、接触阻抗测量方法及其装置

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20060224077A1 (en) * 2002-10-08 2006-10-05 Gilles Pauly Analysis of a skin reactivity and hypersensitivity
WO2009033181A1 (fr) * 2007-09-07 2009-03-12 Emsense Corporation Casque d'écoute à capteurs intégrés
US20100191305A1 (en) * 2009-01-26 2010-07-29 Mir Imran Method and apparatus for the detection of aberrant neural-electric activity
US20110295096A1 (en) * 2010-05-25 2011-12-01 Neurowave Systems Inc. Method and system for electrode impedance measurement
US20130338529A1 (en) * 2011-02-28 2013-12-19 Nihon Kohden Corporation Bioelectric signal measurement apparatus

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20060224077A1 (en) * 2002-10-08 2006-10-05 Gilles Pauly Analysis of a skin reactivity and hypersensitivity
WO2009033181A1 (fr) * 2007-09-07 2009-03-12 Emsense Corporation Casque d'écoute à capteurs intégrés
US20100191305A1 (en) * 2009-01-26 2010-07-29 Mir Imran Method and apparatus for the detection of aberrant neural-electric activity
US20110295096A1 (en) * 2010-05-25 2011-12-01 Neurowave Systems Inc. Method and system for electrode impedance measurement
US20130338529A1 (en) * 2011-02-28 2013-12-19 Nihon Kohden Corporation Bioelectric signal measurement apparatus

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111728612A (zh) * 2020-06-05 2020-10-02 武汉励石医疗科技有限责任公司 生物电阻抗测量方法、接触阻抗测量方法及其装置
CN111728612B (zh) * 2020-06-05 2022-05-03 武汉励石医疗科技有限责任公司 生物电阻抗测量方法、接触阻抗测量方法及其装置

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