Patent Application
20220054032
The present invention relates to a method for enhancing local EEG signals and an EEG electrode device, and more particularly to an EEG electrode device having at least one central electrode and peripheral electrodes around the central electrode to obtain local EEG signals and background EEG signals and further to amplify and remove a common-mode background EEG signal generated by the background EEG signals through filtering, so as to enhance the local EEG signals.
EEG is an electrophysiological monitoring method to record electrical activity of the brain of a patient, and it has been widely used in clinical practice. In clinical practice, electrically conductive gel is usually used with conventional Ag/Ag or Au electrodes to measure EEG signals. However, the use of electrically conductive gel for long-term EEG measurement will encounter the drying and hardening problems.
Therefore, many dry electrodes have been developed to improve the above problems. Dry electrodes based on microelectromechanical systems (MEMS) adopt a semi-invasive method, and the manufacturing cost is relatively expensive. Some different electrically conductive materials, such as electrically conductive rubber, fabric, polymer foam, and the like may be applied to dry electrodes. However, the skin-electrode impedance of these electrodes is still higher than that of traditional electrodes using electrically conductive gel. In addition, it is still difficult to use these electrodes to measure EEG signals on the hair area. Unless the hair is separated, these dry electrodes are not in close contact with the skin.
In order to solve the problem that it is difficult to measure EEG signals on the hair area, some comb-shaped dry electrodes are developed on the market. Although these special dry electrodes can increase the contact area between the skin and the electrode on the hair area, the skin-electrode impedance is still much higher than that of traditional electrodes using electrically conductive gel. Besides, the EEG signals are extremely weak and easily interfered by other background EEG signals or physiological electrical signals.
In order to improve EEG signals measured by dry electrodes for interpretation, the present invention provides an EEG electrode device for enhancing local EEG signals. The EEG electrode device comprises an EEG signal receiving electrode assembly and an EEG signal enhancement circuit.
The EEG signal receiving electrode assembly includes an electrode substrate, at least one central electrode, and a plurality of peripheral electrodes. The central electrode and the peripheral electrodes are disposed on the electrode substrate. The peripheral electrodes are arranged around the central electrode. The EEG signal enhancement circuit includes an active dry electrode circuit and a common-mode EEG signal suppression filter circuit. The active dry electrode circuit includes at least one first amplifier connected with the central electrode and a plurality of second amplifiers connected with the respective peripheral electrodes. The common-mode EEG signal suppression filter circuit includes an amplifier and a common-mode signal circuit. The first amplifier is connected to a positive terminal of the amplifier. The second amplifiers are connected to the common-mode signal circuit. The common-mode signal circuit is connected to a negative terminal of the amplifier.
Preferably, the common-mode signal circuit is an averaging circuit.
Preferably, the EEG signal receiving electrode assembly is a comb-shaped electrode assembly.
Preferably, the electrode substrate has a circular shape, the central electrode is located on a center of the electrode substrate, and the peripheral electrodes are located on a periphery of the electrode substrate.
Preferably, the central electrode and the peripheral electrodes each include an electrically conductive sleeve, an electrically conductive elastic member, and a pin electrode. The electrically conductive sleeve is welded to the electrode substrate. The electrically conductive elastic member is inserted into the electrically conductive sleeve. One end of the pin electrode is inserted into the electrically conductive sleeve and pressed against the electrically conductive elastic member, and another end of the pin electrode extends out of the electrically conductive sleeve, so that the pin electrode is stretchable relative to the electrically conductive sleeve.
The present invention also provides a method for enhancing local EEG signals, comprising:
providing at least one central electrode for receiving a local EEG signal and a plurality of peripheral electrodes arranged around the central electrode for receiving a background EEG signal; the local EEG signal being input to at least one first amplifier of an active dry electrode circuit; the background EEG signal being input to second amplifiers of the active dry electrode circuit; thereby reducing input signal attenuation and amplifying the local EEG signal and the background EEG signal; the amplified local EEG signal being input to a positive terminal of an amplifier of a common-mode EEG signal suppression filter circuit; the amplified background EEG signal being input to a common-mode signal circuit of the common-mode EEG signal suppression filter circuit to generate a common-mode background EEG signal, the common-mode background EEG signal being input to a negative terminal of the amplifier; thereby removing the common-mode background EEG signal and enhancing the local EEG signal.
Preferably, the common-mode signal circuit is an averaging circuit to generate the common-mode background EEG signal by using an averaging method.
Preferably, the central electrode and the peripheral electrodes are stretchable to fit a patient's head shape.
The following effects can be achieved through the above technical features:
1. The electrodes provided by the present invention are dry electrodes, which can obtain EEG signals with sufficient strength for interpretation without using electrically conductive gel.
2. The EEG signal receiving electrode assembly of the present invention is a comb-shaped dry electrode assembly, and the central electrode and the peripheral electrodes are stretchable to be in close contact with the scalp so as to fit the patient's head shape in a good contact state.
3. The invention utilizes an active dry electrode circuit to amplify local EEG signals and background EEG signals, so as to increase the strength of the received EEG signals and to avoid signal attenuation and phase distortion and to reduce a common-mode rejection ratio. Then, the common-mode signal circuit is used to obtain the common-mode background EEG signal from the background EEG signal to remove the common-mode signal of the local EEG signal and increase the strength of the local EEG signal.
Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings.
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The EEG signal receiving electrode assembly 1 includes an electrode substrate 11, at least one central electrode 12, and a plurality of peripheral electrodes 13. The central electrode 12 and the peripheral electrodes 13 are disposed on the electrode substrate 11. The peripheral electrodes 13 are arranged around the central electrode 12. Preferably, the EEG signal receiving electrode assembly 1 is a comb-shaped dry electrode assembly. The electrode substrate 11 has a circular shape. The central electrode 12 is located on the center of the electrode substrate 11, and the peripheral electrodes 13 are located on the periphery of the electrode substrate 11.
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Although particular embodiments of the present invention have been described in detail for purposes of illustration, various modifications and enhancements may be made without departing from the spirit and scope of the present invention. Accordingly, the present invention is not to be limited except as by the appended claims.
