WO2019168500A1 - Évaluation de qualité de connexion pour réseaux d'électrodes d'eeg - Google Patents

Évaluation de qualité de connexion pour réseaux d'électrodes d'eeg Download PDF

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Publication number
WO2019168500A1
WO2019168500A1 PCT/US2018/019902 US2018019902W WO2019168500A1 WO 2019168500 A1 WO2019168500 A1 WO 2019168500A1 US 2018019902 W US2018019902 W US 2018019902W WO 2019168500 A1 WO2019168500 A1 WO 2019168500A1
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WIPO (PCT)
Prior art keywords
electrode
electrodes
signal
subject
impedance
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Application number
PCT/US2018/019902
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English (en)
Inventor
Alexander M. GRANT
Jianchun Yi
Bradley G. BACHELDER
Raymond Woo
Josef Parvizi
Xingjuan CHAO
Original Assignee
CeriBell, Inc.
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.)
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Application filed by CeriBell, Inc. filed Critical CeriBell, Inc.
Priority to PCT/US2018/019902 priority Critical patent/WO2019168500A1/fr
Publication of WO2019168500A1 publication Critical patent/WO2019168500A1/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
    • A61B5/24—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
    • A61B5/24—Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
    • A61B5/316—Modalities, i.e. specific diagnostic methods
    • A61B5/369—Electroencephalography [EEG]
    • 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
    • A61B5/6846—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient specially adapted to be brought in contact with an internal body part, i.e. invasive
    • A61B5/6886—Monitoring or controlling distance between sensor and tissue
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
    • A61N1/00—Electrotherapy; Circuits therefor
    • A61N1/02—Details
    • A61N1/08—Arrangements or circuits for monitoring, protecting, controlling or indicating
    • A61N2001/083—Monitoring integrity of contacts, e.g. by impedance measurement

Definitions

  • the present disclosure relates generally to the field of measuring electrical signals from living subjects (e.g., electrical signals indicative of brain activity and/or heart activity) and providing electrical signals to living subjects (e.g., for neurostimulation or muscle stimulation).
  • the present disclosure relates to systems, devices, and methods for calibrating the connection between the electrode(s) of such measurement and/or stimulation devices and the tissue of the living subject, typically skin.
  • EEG electroencephalography
  • Electrocardiography ECG or EKG signals
  • ECG electrocardiography
  • skeletal muscles i.e., electromyography (EMG) signals
  • EMG electromyography
  • Electrical signals may be delivered to the heart to pace the rate and rhythm of heart beats, and in some cases, for defibrillation of the heart. Electrical signals may be applied to various parts of the nervous system to upregulate and/or downregulate various nerve and nerve-related functions.
  • the spinal cord may be stimulated to treat pain, facilitate injury rehabilitation, restore cardiac function, and lower blood pressure, among other indications.
  • the peripheral nerves may also be stimulated to treat pain, facilitate injury rehabilitation, treat incontinence, and lower blood pressure, among other indications.
  • Electrical signals may be delivered to the skeletal muscles to diagnose responsiveness, facilitate injury rehabilitation, accelerate muscle recovery, improve metabolism, tone skeletal muscle tissue, and as an alternative to weight-bearing exercise, among other purposes.
  • the electrical signals delivered may be varied in accordance with other electrical signals measured to provide a form of feedback therapy.
  • connection(s) between measurement and/or stimulation electrode(s) and tissue of a patient In many cases, the connection will be between the skin and the electrode(s).
  • EEG headsets contact EEG electrodes with the scalp of the subject
  • ECG electrodes are typically contacted to skin on the chest of a subject
  • EMG electrodes are typically contacted to skin over the target skeletal muscles, and, in some cases, nerves and muscles may be stimulated externally from external electrode(s) contacting skin adjacent the target nerves and/or muscles.
  • connection between the electrode(s) and skin may not always be ideal for many reasons—such as skin moisture and quality not being ideal for electrode contact, the presence of hair, the presence of regions of thickened and/or hardened skin, the presence of dirt, undesired fluids, or other residue, to name a few examples.
  • the electrode-to-skin connection may often need to be assessed so that, if appropriate, a medical professional may re-position the electrode, clean the skin and/or electrode, or otherwise re-adjust the connection as needed to have a more ideal electrode connection for the intended measurement and/or diagnosis. In other cases, the connection will be between the electrode(s) and other tissue.
  • connection may be between dura mater in the epidural space and the electrode lead(s) for spinal cord simulators, between the pacing lead(s) and cardiac tissue for pacing devices, the electrode(s) and skeletal muscle tissue for skeletal muscle stimulators, etc.
  • Connection quality between the electrode(s) and the tissue may again be important to obtain high quality measurements and/or provide the stimulation at the desired levels.
  • connection between measurement or stimulation electrode(s) and tissue of the subject is assessed before measurement and/or stimulation.
  • Measurement and/or stimulation in some cases, however, may be long-term and continuous. For example, measurements and/or stimulation may be undertaken for at least 30 minutes, at least an hour, at least a day, or at least a week or more in many applications. And, connection quality may deteriorate or at least vary over the long measurement and/or stimulation time period.
  • Many currently used connection quality assessment methods cannot determine connection quality while measurement and/or stimulation are occurring. For example, many connection quality assessment methods depend on the use of a further reference electrode and/or reference current, which in many cases cannot be present when measurement and/or stimulation are undertaken.
  • connection quality assessments methods that are usable concurrently with measurement and/or stimulation, so that electrode connections can be re-adjusted as necessary throughout the desired measurement and/or stimulation time period, the measurement and/or stimulation can be dynamically adjusted based on the current connection quality, the measurement and/or stimulation signal can be recorded along with connection quality assessment to provide signal recordings with more data points for later analysis, to name a few desirable purposes.
  • the present disclosure relates generally to the field of measuring electrical signals detected from living subjects (e.g., electrical signals indicative of brain activity and/or heart activity) and providing electrical signals to living subjects (e.g., for neurostimulation or muscle stimulation).
  • the present disclosure relates to systems, devices, and methods for calibrating the connection between electrode(s) of such measurement and/or stimulation devices and the tissue of the living subject, typically skin.
  • An exemplary measurement and/or stimulation apparatus may comprise a plurality of electrodes configured to contact the skin of a subject to measure and/or convey one or more electrical signals.
  • Voltage differentials between the different electrodes may be used, according to
  • the apparatus may notify the subject or other user and may record connection quality data points in parallel with measured electrical signals. Hence, the subject or other user may be prompted to improve connection quality and the reliability of the measured electrical signals, and medical professionals may take into account the record of connection quality while later analyzing the electrical signals that are measured and recorded.
  • An electrical sensor or stimulator may be provided (step (a)).
  • the electrical sensor or stimulator may comprise a plurality of electrodes, not including a common ground or reference electrode.
  • the plurality of electrodes may be contacted to tissue of a subject (step (b)).
  • a test signal may be provided to the tissue of the subject through a first electrode of the plurality of electrodes (step (c)).
  • At least one voltage difference between the first electrode and a second electrode may be determined in response to the test signal (step (d)).
  • An impedance of the first electrode may be determined in response to the at least one voltage difference (step (e)).
  • One or more of the subject or a user may be notified that connection quality of the first electrode is poor if the determined impedance of the first electrode is above a first predetermined impedance threshold (step (f)).
  • the first and second electrodes may be adjacent one another.
  • the electrical sensor or stimulator may comprise one or more of a wearable headset, an electrode patch, or an electrode lead advanceable through the tissue, a body cavity, or a body lumen.
  • the wearable sensor may comprise a wearable headset.
  • the plurality of electrodes may comprise a first set of electrodes on one side of the electrical sensor or stimulator and a second set of electrodes on a second side of the electrical sensor or stimulator opposite the first side.
  • the electrical sensor or stimulator may comprise a wearable headset comprising a first hemisphere and a second hemisphere.
  • the plurality of electrodes may comprise a first set of electrodes on the first hemisphere and a second set of electrodes on the second hemisphere.
  • the tissue of the subject may comprise a skin of the subject, muscle tissue of the subject, or neural tissue of the subject.
  • the tissue of the subject comprises a skin of the subject.
  • the skin of the subject may comprise a scalp of the subject.
  • the test signal may have a predetermined frequency, and the impedance may be determined in response to the predetermined frequency.
  • the predetermined frequency may be in a range of 1 to 150 Hz.
  • the test signal may be provided through the first electrode with a first predetermined current.
  • a first voltage difference between the first electrode and the second electrode may be determined and a second voltage difference between the first electrode and a third electrode may be determined.
  • a first impedance between the first electrode and the second electrode may be determined in response to the first voltage difference
  • a second impedance between the first electrode and the third electrode in response to the second voltage difference may be determined
  • a lesser of the first and second impedances may be determined, and the lesser of the first and second impedances may be assigned as the determined impedance of the first electrode.
  • the predetermined acceptable impedance threshold may be in a range of 0 to 100 kQ.
  • Steps (c) to (e) may be repeated for at least one additional electrode of the plurality of electrodes to determine a plurality of impedances for the plurality of electrodes.
  • the one or more of the subject or the user may be notified by providing one or more of an audio or visual signal or alarm.
  • An electrical stimulation signal may further be provided with the electrical sensor or stimulator.
  • the electrical stimulation signal may provide stimulation of one or more of a nerve, a spinal cord nerve, a peripheral nerve, a skeletal muscle, a smooth muscle, or cardiac tissue.
  • a bioelectrical signal may be measured from the subject as the impedance of the first electrode is determined.
  • the bioelectrical signal may comprise one or more of an EEG signal, an ENG signal, an ECG signal, an EKG signal, or an EMG signal.
  • the bioelectrical signal may further be recorded to generate a signal recording, and the signal recoding pay be provided with connection quality data points in response to the determined impedance.
  • the plurality of electrodes may be coupled to a processor, and the processor may be configured to one or more of generate the test signal, determine the at least one voltage difference, or determine the impedance of the first electrode.
  • the first and second electrodes may be adjacent one another.
  • the test signal may have a predetermined frequency, and the impedance may be determined in response to the predetermined frequency.
  • the predetermined frequency may be in a range of 1 to 150 Hz.
  • the test signal may be provided through the first electrode with a first predetermined current.
  • a first voltage difference between the first electrode and the second electrode may be determined and a second voltage difference between the first electrode and a third electrode may be determined.
  • a first impedance between the first electrode and the second electrode may be determined in response to the first voltage difference
  • a second impedance between the first electrode and the third electrode in response to the second voltage difference may be determined
  • a lesser of the first and second impedances may be determined, and the lesser of the first and second impedances may be assigned as the determined impedance of the first electrode.
  • the plurality of electrodes may be configured to measure a bioelectrical signal from the subject as the impedance of the first electrode is determined.
  • the bioelectrical signal may comprise one or more of an EEG signal, an ENG signal, an ECG signal, an EKG signal, or an EMG signal.
  • aspects of the present disclosure also provide methods of providing an electrode connection quality assessment to a user.
  • An impedance measurement of an electrode coupled to a subject may be scaled to be within a predetermined value range (step (a)).
  • the scaled impedance measurement may be sorted into a selected qualitative connection quality category of a plurality of qualitative connection quality categories (step (b)).
  • One or more of the scaled impedance measurement or the selected qualitative connection quality category for the electrode coupled to the subject may be visually displayed (step (c)).
  • the electrode coupled to the subject may comprise an EEG electrode, an ENG electrode, an ECG electrode, an EKG electrode, or an EMG electrode.
  • FIG. 1A illustrates a side view of a patient with an electrode carrier system configured as a headband for EEG, in accordance with some embodiments.
  • FIG. 1B illustrates a view of an electrode system for ECG on a patient chest, in accordance with some embodiments.
  • FIG. 1C illustrates a view of an electrode system for EMG on a muscle group of a patient’s leg, in accordance with some embodiments.
  • FIG. 1E illustrates a view of an electrode system for stimulation on a muscle group of a patient arm, accordance with some embodiments.
  • FIG. 2 is a schematic diagram illustrating a body interface system for acquiring and processing signals from a living subject, in accordance with some embodiments.
  • FIG. 3A is a block diagram illustrating a digital processor used for processing signals representing bodily functions, in accordance with some embodiments.
  • FIG. 3B is a schematic diagram of circuitry in a portable, pocket-sized handheld device for sonifying electrical signals, in accordance with some embodiments of the invention.
  • FIG. 4 is an illustration of a wearable device for sonifying electrical signals obtained from a subject, in accordance with some embodiments of the invention.
  • FIG. 5 is a schematic of front-end electrode connections for a signal processor that can be used to assess electrode connection quality, in accordance with some embodiments of the invention.
  • FIG. 6 is a flow chart showing a method of assessing connection quality between the electrodes of a wearable device for measuring electrical signals from the subject and/or providing electrical signals to the subject, in accordance with some embodiments of the invention.
  • FIG. 7A shows an exemplary user interface displaying connection quality of various electrodes, in accordance with embodiments of the invention.
  • FIG. 7B is a flow chart showing a method of correlating impedance measurements with connection quality assessments for display to a user, in accordance with embodiments of the invention.
  • FIG. 8 shows an exemplary user interface displaying bioelectrical signal readings including one or more tags to indicate electrode connection quality at the time of the measurement of the bioelectrical signal, in accordance with embodiments of the invention.
  • the present disclosure relates to systems, devices, and methods for calibrating the connection between the electrode(s) of such measurement and/or stimulation devices and the tissue of the living subject, typically skin.
  • aspects of the present disclosure include methods and mechanisms for assessing electrode connection quality that may be applicable for bioelectrical signal measurement such as EEG, ECG, and EMG as well for providing electrical stimulation signals to the heart, nerves, muscles, skin, and other tissue.
  • bioelectrical signal measurement such as EEG, ECG, and EMG
  • Many embodiments herein for assessing electrode connection quality are described with reference to EEG measurement, but are applicable to other bioelectrical measurement and electro stimulation modalities.
  • EEG and ECG signals are typically visually displayed to a medical professional or analytical algorithm for diagnostic or scientific purposes.
  • the measured bioelectrical signal may be sonified or converted to audio form.
  • subtle features and attributes— and subtle changes in features and attributes— of the electrical signals may not always be easily discernible.
  • sonified or converted to auditory form these subtle features and attributes can become more apparent to a medical professional.
  • sonification methodologies that transform the signals acquired from the living subject into vocal patterns and vocal parameters— and changes in vocal patterns and vocal parameters— that resemble a human voice cam make it easier to discern, upon auditory inspection, subtleties in the underlying electrical signals that correspond to bodily function.
  • Many embodiments herein may further include the sonification of measured bioelectrical signals, in addition to assessing electrode quality.
  • the method can transform signals acquired from the living subject into vocal patterns and vocal parameters that can be used for applications in entertainment as well as user interfaces for electronic devices.
  • Such methods are described further in U.S. Patent Applications Nos. 13/905,377 (filed 30- May-20l3), 14/557,240 (filed 01 -Dec-2014), 15/159,759 (filed l9-May-20l6), 15/387,381 (filed 2l-Dec-20l6), and 15/783,346 (filed l3-Oct-20l7), the contents of which are incorporated herein by reference. [0061] Reference will now be made in detail to various embodiments, examples of which are illustrated in the accompanying drawings.
  • first means “first,” “second,” etc.
  • first sensor could be termed a second sensor
  • second sensor could be termed a first sensor, without changing the meaning of the description, so long as all occurrences of the "first sensor” are renamed consistently and all occurrences of the second sensor are renamed consistently.
  • the first sensor and the second sensor are both sensors, but they are not the same sensor.
  • the term “if” is optionally construed to mean “when” or “upon” or “in response to determining” or “in accordance with a determination” or “in response to detecting,” that a stated condition precedent is true, depending on the context.
  • the phrase “if it is determined [that a stated condition precedent is true]” or “if [a stated condition precedent is true]” or “when [a stated condition precedent is true]” is optionally construed to mean “upon determining” or “in response to determining” or “in accordance with a determination” or “upon detecting” or “in response to detecting” that the stated condition precedent is true, depending on the context.
  • signals representing brain activity e.g., electroencephalography (EEG) signals
  • EEG electrocardiography
  • ECG electrocardiography
  • signals representing other bodily functions e.g., an electromyography (EMG) signal, or an electro nystagmography (ENG) signal, a pulse oximetry signal, a capnography signal, and/or a photoplethysmography signal
  • EMG electromyography
  • ENG electro nystagmography
  • a pulse oximetry signal e.g., a capnography signal
  • photoplethysmography signal e.g., a photoplethysmography
  • an exemplary electrode carrier system 100 for measuring bioelectrical signals may generally comprise a backing 112 shown in the side view of FIG.
  • the electrodes assemblies 114 may be positioned upon the backing 112 to quickly enable conductive contact with the underlying skin while allowing for patient comfort such as when the patient P is reclined, as shown, with the back or side of their head H resting upon a surface without discomfort from the electrodes 114.
  • FIG. 1B illustrates a view of an electrode system 120 for ECG on a chest CH of the patient P, in accordance with some embodiments.
  • the chest CH is shown with a view of the heart HT and ribs RI in order to show an exemplary placement of the electrode system 120 on the patient skin over the anatomy.
  • the electrode system 120 may comprise a carrier system incorporated into a platform or positioning mechanism, such as a carrier system integrated into a shirt. Additionally or alternatively, each of the individual electrode assemblies 124 may be attached individually to the skin S of the patient.
  • Each of the individual electrode assemblies 124 may be spaced by a skilled operator (e.g., a medical professional) or within the positioning mechanism such that they are aligned optimally on the patient chest to measure ECG signals. As shown in FIG. 1B, individual electrode assemblies 124 may be placed at approximately the six standard locations for the precordial leads in an ECG; however, individual electrode assemblies may be placed on the patient in any locations appropriate to receive ECG signals. Individual electrode assemblies may additionally or alternatively be placed on the limbs of the patient P, for example.
  • the system 120 may have each of the electrode assemblies 124 electrically coupled via corresponding conductive wires 126 to a controller and/or output device 128. Although in other variations, the electrode assemblies 124 may be coupled to the controller and/or output device 128 wirelessly.
  • FIG. 1C illustrates a view of an electrode system 130 for EMG on a muscle group MG1 of a leg LG of the patient P, in accordance with some embodiments.
  • the electrode system 130 may comprise a carrier system incorporated into a platform or positioning mechanism, such as a carrier system integrated into a sock or leg band. Additionally or alternatively, each of the individual electrode assemblies 134 may be attached individually to the skin S of the leg LG. In other cases, each of the individual electrode assemblies may be placed intramuscularly, such as with monopolar needle electrode(s). Each of the individual electrode assemblies 134 may be spaced by a skilled operator (e.g., a medical professional) or within the positioning mechanism such that they are aligned optimally on the patient leg to receive the desired EMG signals.
  • the system 130 may have each of the electrode assemblies 134 electrically coupled via corresponding conductive wires 136 to a controller and/or output device 138. Although in other variations, the electrode assemblies 134 may be coupled to the controller and/or output device 138 wirelessly.
  • the controller and/or output device 138 may generally comprise any number of devices for receiving the electrical signals such as electrophysio logical monitoring devices and may also be used in combination with any number of musculoskeletal imaging devices, e.g., MRI, ultrasound imaging, etc.
  • the electrode assemblies 134 may be used in combination with devices such as those which are configured to receive and process electrical signals, such as with various filters or feature identification algorithms.
  • FIG. 1D illustrates a view of an electrode system 140 for stimulation on a spine SP of a patient P, in accordance with some embodiments.
  • the back of the patient P is shown with an internal view of the patient spinal vertebrae and major nerves in order to show an exemplary placement of the electrode system 140 on the skin S of the patient P, such as used during transcutaneous electrical nerve stimulation.
  • the electrode system 140 may comprise a carrier system incorporated into a platform or positioning mechanism, such as a carrier system integrated into a shirt. Additionally or alternatively, each of the individual electrode assemblies 144 may be attached individually to the skin S of the patient P’s back.
  • the controller and/or output device 158 may generally comprise any number of devices for outputting the electrical signals such as electrophysio logical stimulation devices and may also be used in combination with any number of musculoskeletal imaging devices, e.g., MRI, ultrasound imaging, etc.
  • the electrode assemblies 154 may be used in combination with devices such as those which are configured to receive and process electrical signals, such as with various filters or feature identification algorithms.
  • digital processor system 260 is embedded in the wearable device, for example, in a "headband housing" that also holds dry or wet electrodes that contact both sides (left and right sides) of the subject's head.
  • the digital processor system 260 is not embedded in a headband housing, and is instead coupled to electrodes in (or held in position by) a headband by one or more electrical wires or connectors.
  • digital processor system 260 has a separate housing that includes a clip for attachment to the headband.
  • sensors 210 are provided to interface with a living subject's brain to obtain e.g., sense and/or acquire) sensor time-domain signals corresponding to brain electrical activity.
  • sensors 210 are a component of a handheld device for sonifying electrical signals (such as the head-worn electrical carrier system 100 in FIG. 1, similar electrode systems illustrated in FIG. 1B-1E, and the wearable device 400 in FIG. 4).
  • the wearable device is configured to interface with the sensors 210 (e.g., the sensors 210 are disposable and plug into the wearable device).
  • the sensors 210 include one or more electrodes.
  • extra-cranial sensor 210-1 may include an electrode (e.g., electroencephalography (EEG) electrode) or a plurality of electrodes (e.g., electroencephalography (EEG) electrodes) affixed externally to the scalp (e.g., glued to the skin via conductive gel), or more generally positioned at respective positions external to the scalp.
  • EEG electroencephalography
  • EEG electroencephalography
  • dry electrodes can be used in some implementations (e.g., conductive sensors that are mechanically placed against a living subject's body rather than planted within the living subject's body or held in place with a conductive gel).
  • An example of a dry-electrode is a headband with one or more metallic sensors (e.g., electrodes) that is worn by the living subject during use (FIG. 4).
  • the signals obtained from an extra-cranial sensor 210-1 are sometimes herein called EEG signals or time- domain EEG signals.
  • signals corresponding to heart electrical activity may be obtained from a human heart and correspond to electrical signals obtained from a single cardiomyocyte or from a plurality of cardiomyocytes (e.g., a sinoatrial (SA) node of a human subject).
  • the heartbeat pulse sensors include one or more sensing elements affixed (e.g., taped, attached, glued) externally to a human body (e.g., a human subject's chest, abdomen, arm, or leg).
  • dry electrodes can be used in some implementation (e.g., conductive sensors that are mechanically placed against a human body rather than being implanted within the human body or held in place with a conductive gel).
  • An example of a dry-electrode is a chest strap with one or more metallic sensors (e.g., electrodes) that is worn by the living subject during use.
  • Another example of a dry- electrode is a thumb apparatus or a hand apparatus with one or more metallic sensing elements (e.g., electrodes) that is touched (e.g., with the living subject's thumbs) and/or held onto (e.g., with the living subject's hands) by the living subject during use.
  • the signals obtained from heartbeat pulse sensors are sometimes herein called ECG signals or time-domain ECG signals.
  • sensors 210 are sensors of electrical potential produced by skeletal muscles.
  • sensors 210 can be used both as EEG sensors and as EMG sensors (e.g. by placing sensors 210 on the patient’s skin near a skeletal muscle group).
  • the electrical potential sensors are provided to interface with a living subject’s muscles to obtain (e.g. sense and/or acquire) sensor time-domain signals corresponding to muscle electrical activity.
  • signals corresponding to muscle electrical activity may be obtained from a human quadriceps and correspond to electrical signals obtained from contraction of said quadriceps.
  • the electrical potential sensors may include an electrode or a plurality of electrodes affixed externally to the human body (e.g.
  • EMG electrowetting-on-semiconductor
  • conductive sensors that are mechanically placed against a human body rather than being implanted within the human body or held in place with a conductive gel.
  • electrodes may be implanted in the patient (e.g. into the quadriceps), such as in intramuscular EMG.
  • the signals obtained from the electrical potential sensors are sometimes herein called EMG signals or time-domain EMG signals.
  • arrays of sensors are designed to record intracranial EEG and produce a plurality of sensor time-domain signals.
  • sensor time-domain signals include wideband features including high-gamma bursts in the range of 80— 150 Hz.
  • sensor time-domain signals include frequencies (sometimes called frequency components) below (e.g., lower than or in the lowest ranges of) the human audible frequency-range.
  • the nerve stimulators include one or more stimulating elements affixed (e.g., taped, attached, glued) externally to a human body (e.g., a human subject's chest, abdomen, arm, or leg).
  • the nerve stimulators may include an electrode or a plurality of electrodes affixed externally to the human body (e.g., glued to the skin via conductive gel), or more generally positioned at respective positions external to the human body.
  • dry electrodes can be used in some implementation (e.g., conductive sensors that are mechanically placed against a human body rather than being implanted within the human body or held in place with a conductive gel).
  • the nerve stimulators include one or more stimulating elements implanted subcutaneously (e.g., in proximity to a patient spinal cord), such as in a Dorsal Column Stimulator.
  • nerve stimulators output voltages to effect nerve electrical activity.
  • nerve stimulators output electrical currents to effect nerve electrical activity.
  • nerve stimulators output multiple voltages on different electrodes in order to produce differential voltages (e.g., differences in voltage values) between two stimulation locations (e.g., between two stimulation elements). For example, when a respective nerve stimulator includes two or more stimulating elements (e.g., electrodes) positioned at respective positions external to the human body, the respective nerve stimulator may apply differential voltages (e.g., bipolar voltages) between the two or more stimulating elements located at the respective positions.
  • the signals output from the nerve stimulators are sometimes herein called nerve stimulation signals or time-domain nerve stimulation signals.
  • muscle stimulators output voltages to effect muscular electrical activity.
  • muscle stimulators output electrical currents to effect muscular electrical activity.
  • muscle stimulators output multiple voltages on different electrodes in order to produce differential voltages (e.g., differences in voltage values) between two stimulation locations (e.g., between two stimulation elements).
  • differential voltages e.g., differences in voltage values
  • the respective nerve stimulator may apply differential voltages (e.g., bipolar voltages) between the two or more stimulating elements located at the respective positions.
  • the signals output from the muscle stimulators are sometimes herein called muscle stimulation signals or time-domain muscle stimulation signals.
  • analog front end 220 outputs time-domain signals from sensors or stimulators 210 and optionally pre-processes the time-domain signals.
  • a separate (e.g., independent) analog front end is provided for interfacing with each of a set of sensors or stimulators 210.
  • a fourth analog front end is provided for interfacing with a set of nerve stimulators 210.
  • a fifth analog front end is provided for interfacing with a set of muscle stimulators 210.
  • body interface system 200 comprises a plurality of analog front end modules (e.g., analog front end 220-a, analog front end 220-b, though analog front end 220-n) for interfacing with a plurality of sensors or stimulators 210.
  • body interface system 200 may include digital processor system 260 for processor signals obtained from the living subject (e.g., signals corresponding to electric activity and/or stimulation of the brain or heart or musculature), optionally after the signals are pre-processed by analog front end 220.
  • Digital processor 260 may include signal conditioning modules 230, signal modulators 240, and synthesizer modules 550.
  • signal modulator(s) 240 receive(s) the digitized time-domain signals output by signal conditioning module(s) 230, and concurrently generate a set of acoustic parameters, including a plurality of time-varying acoustic parameters from (e.g., using) the digitized time-domain signals.
  • One or more of the plurality of time-varying acoustic parameters is modulated in accordance with at least the signal value of the time- domain signal.
  • a synthesizer module e.g., synthesizer module(s) 250
  • a plurality of representations of acoustic signals is combined to produce a combined acoustic signal.
  • a combined acoustic signal is generated by combining acoustic signals corresponding to the plurality of representations of acoustic signals produced by digital processor system 260Signal processing and sonification for the body interface system 200 is further described in U.S. Patent Applications Nos. 13/905,377 (filed 30- May-20l3), 14/557,240 (filed 0l-Dec-20l4), and 15/159,759 (filed l9- May-20l6), the contents of which are incorporated herein by reference.
  • FIG. 3A is a block diagram illustrating digital processor system 260 in accordance with some embodiments, and FIG. 3B depicts an example of a set of components on a printed circuit board (PCB) that implement digital processor system 260.
  • Digital processor system 260 typically includes one or more processing units (CPUs) 302 for executing modules, programs and/or instructions stored in memory 310 and thereby performing processing operations; one or more network or other communications interfaces 304 (e.g., a wired communication interface such as a USB port, micro-USB port, or the like, and/or a wireless communication interface); memory 310; and one or more communication buses 309 for interconnecting these components.
  • CPUs processing units
  • network or other communications interfaces 304 e.g., a wired communication interface such as a USB port, micro-USB port, or the like, and/or a wireless communication interface
  • memory 310 e.g., a wired communication interface such as a USB port, micro-USB port, or the like
  • the communication buses 309 optionally include circuitry (sometimes called a chipset) that interconnects and controls communications between system components.
  • Digital processor system 260 optionally includes a user interface 305 comprising a display 306, one or more input devices 307 (e.g., one or more buttons, and, optionally, one or more of a microphone, keypad, and touch screen, etc.), and one or more speakers 308 (e.g., for audio playback of acoustic signals corresponding to brain and/or heart activity).
  • Display 306 optionally includes one or more LEDs, for example, one or more LEDs for indicating a status of digital processor system 260 (e.g., a steady blinking LED to indicate that EEG signals are being received and/or to indicate that accelerometer signals corresponding to mechanical movement of the subject are sufficiently low-amplitude to allow DSP 260 to produce valid sonification of EEG signals) and, in another example, an LED to indicate battery status (e.g., a red LED that is turned on when battery power is low, and/or a green LED that is turned on when an internal battery is charged and that blinks on and off in a predefined pattern when battery power is low).
  • a status of digital processor system 260 e.g., a steady blinking LED to indicate that EEG signals are being received and/or to indicate that accelerometer signals corresponding to mechanical movement of the subject are sufficiently low-amplitude to allow DSP 260 to produce valid sonification of EEG signals
  • an LED to indicate battery status e.g., a red LED that is turned on when battery
  • input devices 307 may include a power on/off button for powering digital processor system 260 on and off, a reset button for resetting digital processor system 260 to a predefined initial state, and a record button for starting and stopping recording of EEG data corresponding to a subject's brain activity.
  • input devices 307 include a microphone for receiving and recording a user's spoken comments made just prior to, or while, DSP 260 records EEG data corresponding to a subject's pressing of the "record" button shown in FIG. 3B.
  • Digital processor system 260 may record any spoken comments by the user for a predefined period (e.g., 5 to 10 seconds following the button press), and also records EEG data corresponding to the subject's brain activity or other digitized time domain data until the user presses the record button a second time, or until a predefined period of time elapses (e.g., 5 minutes), or until a predefined period of time (e.g., 5 minutes) elapses during which the device (digital processor system 260) does not receive electrical signals corresponding to abnormal brain activity or other abnormal electrical activity or other cue to stop collection.
  • a predefined period e.g., 5 to 10 seconds following the button press
  • EEG data corresponding to the subject's brain activity or other digitized time domain data until the user presses the record button a second time, or until a predefined period of time elapses (e.g., 5 minutes), or until a predefined period of time (e.g., 5 minutes) elapses during which the device
  • Digital processor system 260 optionally includes sensor interfaces 370 for interfacing with sensors or stimulators 210 (FIG. 2) and/or analog front end 220 (FIG. 2) and synthesizer module 374 for combining concurrently generated acoustic parameters to produce a representation of an acoustic signal corresponding to one or more time-domain signals.
  • sensors 210 are located, at least in part, within the same housing that holds digital processor system 260, while in some other embodiments, sensors or stimulators 210 are located external to that housing and are coupled to digital processor system 260 via one or more electrical connectors and sensor interface(s) 370.
  • Digital processor system 260 optionally (and typically) includes a battery 382 (e.g., a rechargeable battery) and charger 380, to provide power to digital processor system 260 and enable operation of digital processor system 260 without connection to an external power source (except to charge battery 382).
  • battery 382 is charged via charger 380, when an external power source is connected to system 260 via a USB port or micro-USB port of the device.
  • Memory 310 may include high-speed random access memory, such as DRAM, SRAM, DDR RAM or other random access solid state memory devices; and optionally includes non-volatile memory, such as one or more magnetic disk storage devices, optical disk storage devices, flash memory devices, or other non-volatile solid state storage devices.
  • Memory 310 optionally includes one or more storage devices remotely located from the CPUs 302, memory 310, or alternately the non-volatile memory devices within memory 310, comprises a non-transitory computer readable storage medium.
  • memory 310, or the computer readable storage medium of memory 310 stores the following programs, modules and data structures, or a subset thereof:
  • Operating system 312 may include procedures for handling various basic system services and for performing hardware dependent tasks
  • Optional local data storage 270 that may store data corresponding to the one or more electrical signals (e.g., data storage 270 stores raw EEG or other data and/or audio data so that the data can be reviewed later by, e.g., a specialist).
  • data storage 270 stores raw EEG or other data and/or audio data so that the data can be reviewed later by, e.g., a specialist).
  • data storage 270 includes a removable non-volatile memory card, such as a micro SD flash memory card (see “pSD” in FIG. 3B, which represents a micro-SD card“reader” for receiving and interfacing a micro SD flash memory card to a microcontroller).
  • digital processor system 260 may communicate with cloud-based storage (e.g., storage that is remote from the device) to store data corresponding to the one or more electrical signals.
  • cloud-based storage e.g., storage that is remote from the device
  • memory 310 optionally stores a subset of the modules and data structures identified above.
  • FIG. 4 is an illustration of a wearable device 400 for sonifying electrical signals obtained from subject 402, in accordance with some embodiments.
  • a wearable device for sonifying electrical signals may have the form of a shirt, sock, glove etc. for sonifying signals from EMG or ECG or for sonifying signals for stimulating a patient nerve or muscle.
  • Device 400 may include a plurality of electrodes 452 (e.g., 452a, 452b). These electrodes can be dry or wet electrodes. Electrodes 452 may be configured to be placed at respective locations on the subject's body. For example, in some embodiments, electrode 452a and electrode 452b are positioned (placed) substantially at predefined locations when subject 402 wears device 400.
  • wearable housing 404 is a headband, a helmet, a hat, a sock, a glove, a shirt, pants, etc.
  • wearable housing 404 includes a headband that includes an adjustable strap or housing that is configured to fully wrap around the subject's head to stably hold the wearable housing on the subject's head.
  • device 400 interfaces with a chest strap having one or more electrodes to measure a heartbeat signal concurrently with the brain signals.
  • device 400 may be worn by epileptics and/or patients with other types of diagnosed conditions to alert them of an on-coming episode.
  • an epileptic patient may wear device 400 while driving.
  • Device 400 may continuously monitor the epileptic patient for indicia of a pre-ictal state, which signifies that the patient is likely to start seizing.
  • the device detects indicia of an ictal state, the device can alert the patient using speaker 408, stating, e.g., "Pull Over! Pull Over! Seizure detected!”
  • FIG. 5 shows a schematic 500 of front-end electrode connections for a signal processor that can be used to assess connection quality between the electrodes 210 of the wearable device 100 or 400 and the subject.
  • the digital processor 260 of the wearable device 100 or 400 may comprise an electrode impedance check function, which can allow digital processor 260 to assess the connection quality of the EEG electrodes to the scalp of the patient and provide the assessment to the user and/or subject.
  • a current on the order of a few nanoamps up to a few microamps would work well with minimal effect on and/or sensation felt by the subject.
  • the analog front-end chip 510 of the digital processor 260 that is, the integrated circuit (IC) containing the amplifiers and ADCs for the EEG readout, can allow a known current to be injected at a particular frequency into any of the electrodes 210.
  • the digital processor system 260 does not have a dedicated reference electrode to measure each electrode against. Instead, each electrode 2l0-n can be referenced to its adjacent electrode(s). Since the ADC channels on a given hemisphere of the wearable device 100 or 400 may all be interconnected through shared electrodes 2l0-n (i.e., some of the electrodes 2l0-n may be connected to the inputs of two adjacent ADCs), the relationship between the electrodes can be used to find the voltage difference, and therefore the impedance, between any combination of two electrodes 2l0-n on a hemisphere.
  • FIG. 5 shows analog front-end electrode connections for the digital signal processor 260.
  • the electrodes 210-1 to 210-10 can be divided into two sides covering the left and right hemispheres, with 5 electrodes on each side forming 4 differential data channels: ADC channel 501 (connected to electrodes 210-1 and 210-2), ADC channel 502 (connected to electrodes 210-2 and 210-3), ADC channel 503 (connected to electrodes 210-3 and 210-4), ADC channel 504 (connected to electrodes 210-4 and 210-5) for the left or right side, and likewise ADC channel 505 (connected to electrodes 210-6 and 210-7), ADC channel 506 (connected to electrodes 210-7 and 210-8), ADC channel 507 (connected to electrodes 210-8 and 210-9), and ADC channel 508 (connected to electrodes 210-9 and 210- 10) for the opposite side, for eight
  • Each electrode 210-1 to 210-10 may be connected to either one or two differential amplifier inputs.
  • the relationship between the electrodes can be used to find the voltage difference, and therefore the impedance, between any combination of two electrodes 2l0-n on a hemisphere as follows:
  • electrode 210-2 - electrode 210-1 ADC channel 501
  • electrode 210-3 - electrode 210-2 ADC channel 502
  • electrode 210-3 - electrode 210-1 ADC channel 502 + ADC channel 501
  • electrode 210-3 - electrode 210-2 ADC channel 502
  • electrode 210-4 - electrode 210-3 ADC channel 503 + ADC channel 502;
  • electrode 210-3 - electrode 210-2 ADC channel 502
  • electrode 210-4 - electrode 210-3 ADC channel 503
  • electrode 210-5 - electrode 210-4
  • electrode 210-2 - electrode 210-1 ADC channel 501
  • electrode 210-3 - electrode 210-2 ADC channel 502
  • electrode 210-4 - electrode 210-3 ADC channel 502
  • electrode 210-7 - electrode 210-6 ADC channel 505
  • electrode 210-8 - electrode 210-7 ADC channel 506
  • electrode 210-9 - electrode 210-8 ADC channel 506
  • electrode 210-7 - electrode 210-6 ADC channel 505
  • electrode 210-8 - electrode 210-7 ADC channel 506
  • electrode 210-9 - electrode 210-8 ADC channel 506
  • FIG. 6 is a flow chart showing a method 600 of assessing connection quality of the electrodes of a wearable device 100 or 400 for sonifying electrical signals that is coupled to the scalp of the subject in a step 605. While FIG. 6 shows an exemplary method of assessing connection quality associated with an EEG measurement, in other embodiments, a method 600 may be used to assess the connection quality associated with sensing or applying another type of electrical signal, such as those disclosed herein. Additionally or alternatively, at a step 605, the wearable device may be coupled to a patient body in the manners disclosed herein to sense or stimulate a patient. The number of electrodes tested may be at the discretion of the user. A minimum of two electrodes, without a common ground or reference electrode required, may be assessed for connection quality. Impedance values are assigned to the electrodes 2l0-n and presented to the user as an indicator for connection quality, either through a summary of the values or each of the impedance values themselves, for example.
  • an impedance of less than or equal to 5 kQ would indicate good connection quality. In some embodiments, an impedance of less than or equal to 100 kQ would signify acceptable connection quality. In some embodiments, the acceptable range of impedances is further divided into tiered ranges, for example, a good connection quality impedance range, a marginal connection quality impendence range, and a bad connection quality impedance range. In some embodiments, the upper range of the acceptable range of the impedance values may be used as a threshold above which connection quality is identified as poor and the user notified of such. To assign an impedance value to any particular one of the ten electrodes:
  • a test signal (e.g., a periodic current output such as a sinusoidal, square, or triangle wave, etc.) may be turned on in the particular electrode at a certain frequency (step 610);
  • Voltage samples from all ADC channels may be collected on the hemisphere (e.g., with four channels) where the particular electrode is located (step 615); 3) The voltage difference between the particular electrode and all other electrodes on that side may be calculated and the calculated value may be stored in buffers (step 620);
  • a frequency decomposition e.g. FFT (Fast Fourier Transform), Goertzel Algorithm, etc.
  • FFT Fast Fourier Transform
  • Goertzel Algorithm etc.
  • the impedance between the particular electrode and each other electrode on that side may be calculated using Ohm's Law, with the voltage being calculated for each electrode pair and the current of the test signal being known (step 630); and
  • the measured impedance and/or a threshold-based electrode connection status can be presented to the user (step 645), or can trigger a“poor connection” warning during recording (step (650).
  • the test signal frequency and the time between impedance measurements may be changed depending on whether a recording is in progress and/or the user has paused an active recording to check the impedance (step 655):
  • impedance test signal may be set to a frequency that is within the normal EEG band (for example, between 1 Hz to 150 Hz, such as 31 Hz); measurements may be acquired in near real time, e.g. every ⁇ 2 seconds.
  • This mode may allow the user to get immediate connection quality feedback when setting up the device or fixing a poor connection during a (paused) recording.
  • the test signal frequency may be within the EEG band, making the raw EEG unusable during the measurement period, but may give an impedance measurement at a frequency that is relevant to EEG. 2.
  • impedance test signal may be set to a frequency that is outside the normal EEG band (e.g., 125 Hz); measurements may be acquired less frequently, e.g. every minute.
  • This mode may allow the device to monitor electrode connection quality and may automatically alert the user to problems, without interfering with the recording.
  • the test signal frequency may be outside the EEG band which may allow it to be filtered from the raw EEG data.
  • steps show method 600 of assessing connection quality in accordance with many embodiments
  • a person of ordinary skill in the art will recognize many variations based on the present disclosure.
  • the steps may be completed in different order. Steps may be added or deleted. Some of the steps may comprise sub-steps. Many of the steps may be repeated as often as beneficial to assessing connection quality.
  • One or more of the steps of the method 600 may be performed with the circuitry as described herein, for example, one or more of the processor or logic circuitry such as those of the digital processor system 260.
  • the circuitry may be programmed to provide one or more of the steps of the method 600, and the program may comprise program instructions stored on a computer readable memory or programmed steps of the logic circuitry such as the programmable array logic or the field programmable gate array, for example.
  • FIG. 7A shows an exemplary electrode check screen user interface 700 displaying connection quality of various electrodes.
  • the user may find it difficult to intuitively understand the difference between impedance measurements themselves (e.g., 5 kG vs. 10 kG electrode impedances), and often, the dynamic range of the measurement corresponding to a poor connection (e.g., both 101 kG and 900 kG may correspond to a poor connection, and the user’s action is likely the same in either case).
  • the impedance calculated by method 600 described above may be correlated to scale which may be simpler and more useful to a user.
  • the impedance measurements may then be presented in a more intuitive manner as shown in user interface 700 such that the user can quickly assess the state of each electrode, and whether the impedance is changing due to their efforts to improve the connection.
  • the impedance measurements may be mapped to a nonlinear numerical scale and presented to the user with a color-coded or otherwise patterned electrode status indicators that are visually perceptible in user interface 700.
  • the user interface 700 may include a legend 705 to indicate which color or pattern indicates a good electrode connection 705-1, a marginal electrode connection 705-2, and a bad electrode connection 705-3.
  • the user interface 700 includes a graphical representation 710 of electrode positions on the patient’s head, including graphical representations 7l5-n of the electrodes themselves and their respective connection quality (i.e., electrode representations 715-1, 715-2, 715-3, 715-4, 715- 5, 715-6, 715-7, 715-8, 715-9, 715-10).
  • a number indicating connection quality is displayed next to each electrode or electrode representation 7l5-n.
  • this number can range from 0 to 99, and may be scaled nonlinearly from the measured impedance. For example:
  • the displayed scaled value may compress the upper range of the measured impedance (poor connection) and expand the lower range (good connection), which can give the user continuous feedback in the form of a smoothly decreasing number as the connection quality improves while the skin is prepped, or the electrodes are adjusted, etc.
  • the graphical representation of the electrode 7l5-n then changes colors or patterns based on the scaled impedance value, which can indicate in an immediately recognizable way whether all electrodes have acceptable connection quality, or whether some need to be adjusted. For example:
  • electrodes or electrode representations 715-1, 715-2, 715-3, 715- 5, 715-6, 715-7 in user interface 700 (FIG. 7)
  • electrodes or electrode representations 715-9, 715-10 in user interface 700 (FIG. 7)
  • the scaled numerical values may not be shown, and only the color-coded electrodes may be displayed. This can allow the user to determine at a glance whether any electrodes need to be adjusted, and whether they should pause the recording to adjust electrodes using the increased feedback granularity afforded by the scaled numerical values.
  • the thresholds at which the electrode graphics 7l5-n will change colors or patterns can be user-adjustable depending on the application, and the user’s needs or preferences.
  • FIG. 7B is a flow chart showing a method 750 of correlating impedance
  • connection quality assessments measurements with connection quality assessments and displaying the connection quality assessment to the user.
  • the impedance(s) of the electrode(s) may be determined, such as in accordance with method 600 described above.
  • the impedance(s) of the electrode(s) may be scaled, such as in the manner described above.
  • the impedance(s) may be nonlinearly scaled to within a predefined range of values such as between 0 and 99.
  • the scaled impedance measurement(s) may be sorted into qualitative categories, such as (i) good connection quality, (ii) marginal connection quality, and (iii) poor connection quality as described above.
  • the scaled impedance measurement(s) may be sorted based on their value ranges such as (i) values between 1-10 being sorted into the good connection quality category, (ii) values between 11-30 being sorted into the marginal connection quality category, and (iii) values between 31-99 being sorted into the poor quality connection category.
  • the value ranges for each of the qualitative categories may be preset or predetermined, or they may be user defined in a sub-step 786.
  • a step 790 the visual representation(s) of the electrode(s) and their connection quality may be displayed visually such as with user interface 700 shown in FIG. 7B.
  • the user interface 700 may further include a representation of the patient’s head as displayed by a step 793 and a connection quality legend as displayed by a step 796.
  • steps 750 show method 750 of providing electrode connection quality assessments to a user in accordance with many embodiments
  • the steps may be completed in different order. Steps may be added or deleted. Some of the steps may comprise sub-steps. Many of the steps may be repeated as often as beneficial to assessing connection quality.
  • One or more of the steps of the method 750 may be performed with the circuitry as described herein, for example, one or more of the processor or logic circuitry such as those of the digital processor system 260.
  • the circuitry may be programmed to provide one or more of the steps of the method 750, and the program may comprise program instructions stored on a computer readable memory or programmed steps of the logic circuitry such as the programmable array logic or the field programmable gate array, for example.
  • Measurements and displays of electrode connection quality may not only assist with the user in optimizing electrode connection prior to measuring the bioelectrical signals of interest or applying electrostimulation, but may also be useful with the user in analyzing the bioelectrical signal(s) measured.
  • the user may choose to discount the bioelectrical signal(s) that are taken with electrode(s) of poor or marginal electrode connection quality and/or may choose to particularly note the bioelectrical signal(s) that are taken with electrode(s) of good connection quality.
  • the user may do this in real-time as a displayed user interface concurrently show the bioelectrical signal(s) and connection quality assessments.
  • the bioelectrical signal(s) may be recorded and stored along with their connection quality assessments for subsequent analysis.
  • bioelectrical signal readings 820 may include one or more tags 830 to indicate electrode connection quality at the time of the measurement of the bioelectrical signal.

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Abstract

L'invention concerne des systèmes, des dispositifs et des procédés pour évaluer une qualité de connexion entre les électrodes d'un dispositif de mesure de signal bioélectrique et/ou de stimulation électrique et le tissu, typiquement la peau, du sujet. Un signal de test est fourni à une première électrode, des différences de tension entre la première électrode et des électrodes supplémentaires sont déterminées, une impédance de la première électrode est déterminée sur la base des différences de tension, et l'impédance déterminée indique la qualité de connexion. Ce processus est typiquement répété pour toutes les électrodes pour déterminer la qualité de connexion. L'utilisateur ou le sujet peut être alerté si la qualité de connexion est faible, et le signal bioélectrique qui est enregistré peut être associé à des points de données indiquant la qualité de connexion pendant l'enregistrement de signal.
PCT/US2018/019902 2018-02-27 2018-02-27 Évaluation de qualité de connexion pour réseaux d'électrodes d'eeg WO2019168500A1 (fr)

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