CN115336996A - Electroencephalogram impedance measuring system and electroencephalogram impedance measuring method - Google Patents

Abstract

The invention relates to the technical field of electroencephalogram measurement and discloses an electroencephalogram impedance measuring system and an electroencephalogram impedance measuring method. Wherein, this brain electrical impedance measurement system includes: at least one electroencephalogram measurement channel, wherein an electrode of the electroencephalogram measurement channel is used for being in contact with the scalp; the constant current source is respectively connected with the at least one electroencephalogram measurement channel and is used for providing a current excitation signal for the at least one electroencephalogram measurement channel; the analog-to-digital conversion unit is respectively connected with at least one electroencephalogram measurement channel, and the signal frequency of the constant current source is a preset multiple of the sampling rate of the analog-to-digital conversion unit; and the impedance measuring unit is connected with the analog-to-digital conversion unit and used for calculating the electroencephalogram impedance based on the electrical signals of the electroencephalogram measuring channel. By implementing the invention, the complexity of the circuit is reduced, the cost is saved, the real-time detection of the electroencephalogram impedance is realized, and both the circuit simplification and the real-time detection of the electroencephalogram impedance are realized.

Description

Electroencephalogram impedance measuring system and electroencephalogram impedance measuring method

Technical Field

The invention relates to the technical field of electroencephalogram measurement, in particular to an electroencephalogram impedance measuring system and an electroencephalogram impedance measuring method.

Background

The electroencephalogram signals can be detected through a plurality of electrodes of the electroencephalogram measuring equipment, and because the electroencephalogram signals are very weak, the contact impedance of the electrodes and the scalp has a great influence on the electroencephalogram signals. Usually, the electroencephalogram measurement equipment has a function of detecting electrode contact impedance so as to reflect the electrode connection state of the current electroencephalogram measurement equipment. However, some electroencephalogram measurement devices can only detect contact impedance before electroencephalogram measurement, or can detect contact impedance only after normal measurement needs to be stopped; although individual electroencephalogram measuring equipment can perform real-time detection of contact impedance in the electroencephalogram signal measuring process, an independent impedance detection circuit needs to be arranged, so that the circuit of the electroencephalogram measuring equipment is complex.

Disclosure of Invention

In view of this, the embodiment of the present invention provides an electroencephalogram impedance measuring system and an electroencephalogram impedance measuring method, so as to solve the problem that circuit simplification and real-time contact impedance detection are difficult to be considered at the same time.

According to a first aspect, an embodiment of the present invention provides an electroencephalogram impedance measurement system, including: at least one electroencephalogram measurement channel, the electrodes of which are used to contact the scalp; the constant current source is respectively connected with the at least one electroencephalogram measurement channel and is used for providing a current excitation signal for the at least one electroencephalogram measurement channel; the analog-to-digital conversion unit is respectively connected with the at least one electroencephalogram measurement channel, and the signal frequency of the constant current source is a preset multiple of the sampling rate of the analog-to-digital conversion unit; and the impedance measuring unit is connected with the analog-to-digital conversion unit and used for calculating the electroencephalogram impedance based on the electrical signals of the electroencephalogram measuring channel.

The electroencephalogram impedance measuring system provided by the embodiment of the invention comprises at least one electroencephalogram measuring channel, a constant current source, an analog-to-digital conversion unit and an impedance measuring unit. The electrode of the electroencephalogram measurement channel is in contact with the scalp, the constant current source is connected with the at least one electroencephalogram measurement channel to provide a current excitation signal for the at least one electroencephalogram measurement channel, the analog-to-digital conversion unit is arranged in the at least one electroencephalogram measurement channel for connection, the frequency of the electroencephalogram signal is different from that of the impedance signal, the signal frequency of the constant current source is set to be a preset multiple of the sampling rate of the analog-to-digital conversion unit, so that the electroencephalogram signal and the impedance signal output by the electroencephalogram measurement channel are converted simultaneously, the electroencephalogram signal and the impedance signal are separated through frequency filtering, data do not need to be converted separately, the complexity of a circuit is reduced, and the cost is saved. The impedance measuring unit is connected with the analog-to-digital conversion unit, and can perform real-time detection on the electroencephalogram impedance based on the electrical signals of the electroencephalogram measuring channel, so that the electroencephalogram impedance measuring system has both circuit simplification and electroencephalogram impedance real-time detection.

With reference to the first aspect, in a first implementation manner of the first aspect, the impedance measuring unit includes: the frequency selection module is connected with the output end of the analog-to-digital conversion unit and is used for separating electroencephalogram signals and impedance signals of the electroencephalogram measurement signals; and the impedance calculation module is connected with the output end of the frequency selection module and used for calculating an impedance value corresponding to the impedance signal.

According to the electroencephalogram impedance measuring system provided by the embodiment of the invention, the impedance measuring unit comprises a frequency selecting module and an impedance calculating module. The frequency selection module is connected with the output end of the analog-to-digital conversion unit and used for separating electroencephalogram signals and impedance signals of the electroencephalogram measurement signals, and the impedance calculation module is connected with the output end of the frequency selection module and used for calculating impedance values corresponding to the electroencephalogram signals. Because the frequency of the electroencephalogram signal is different from that of the impedance signal, the electroencephalogram signal and the impedance signal are separated through the frequency selection module, and the electroencephalogram signal and the impedance signal do not need to be converted separately, so that the complexity of a circuit is reduced.

With reference to the first aspect, in a second implementation manner of the first aspect, the system further includes: the calibration unit is connected with the at least one electroencephalogram measurement channel through at least one calibration branch and used for determining a calibration coefficient of the at least one electroencephalogram measurement channel based on an electric signal of the at least one calibration branch.

With reference to the second implementation manner of the first aspect, in a third implementation manner of the first aspect, the system further includes: the at least one calibration branch is connected with the calibration unit.

The electroencephalogram impedance measuring system provided by the embodiment of the invention further comprises a calibration unit connected with the impedance measuring unit. The calibration unit is connected with at least one electroencephalogram measurement channel through at least one calibration branch and used for determining a calibration coefficient of the at least one electroencephalogram measurement channel based on an electric signal of the at least one calibration branch. The impedance value calculated by the impedance measuring unit is corrected through the calibration coefficient, so that the measurement accuracy of the impedance value is improved.

With reference to the second or third implementation manner of the first aspect, in a fourth implementation manner of the first aspect, the calibration branch includes: the two ends of each group of calibration branch are connected into the corresponding electroencephalogram measurement channel; and the calibration unit is used for controlling the action of the change-over switch so as to control the conducting state of the corresponding calibration branch.

According to the electroencephalogram impedance measuring system provided by the embodiment of the invention, the calibration branch comprises at least one group of calibration resistors and a selector switch. Wherein, the two ends of each group of calibration branches are connected into the corresponding electroencephalogram measurement channels; the change-over switch is connected with the calibration unit, and the calibration unit is used for controlling the action of the change-over switch so as to control the conducting state of the corresponding calibration branch. The calibration resistance and the switch are used for determining the calibration coefficient of the electroencephalogram measurement channel so as to correct the impedance value calculated by the impedance measurement unit, and the measurement accuracy of the impedance value is improved.

With reference to the fourth implementation manner of the first aspect, in a fifth implementation manner of the first aspect, the calibration branch further includes: and one end of the first protection circuit is connected with the change-over switch, and the other end of the first protection circuit is connected with the at least one group of calibration resistors.

In the electroencephalogram impedance measuring system provided by the embodiment of the invention, the calibration branch circuit further comprises a first protection circuit, one end of the first protection circuit is connected with the change-over switch, and the other end of the first protection circuit is connected with at least one group of calibration resistors. The device of the calibration branch circuit is protected through the first protection circuit, overvoltage damage of the calibration branch circuit is prevented, and interference of external high frequency to the calibration branch circuit is prevented.

With reference to the first aspect, in a sixth implementation manner of the first aspect, the system further includes: the second protection circuit is respectively connected with the at least one electroencephalogram measurement channel and is arranged in front of the constant current source, and the second protection circuit is used for protecting a circuit unit arranged behind the second protection circuit; and the filter circuit is respectively connected with the at least one electroencephalogram measurement channel and arranged between the second protection circuit and the constant current source, and the filter circuit is used for filtering high-frequency interference.

The electroencephalogram impedance measuring system provided by the embodiment of the invention further comprises a second protection circuit and a filter circuit. The second protection circuit is respectively connected with at least one electroencephalogram measurement channel and is arranged in front of the constant current source so as to protect the circuit unit arranged behind the second protection circuit; the filter circuit is respectively connected with at least one electroencephalogram measurement channel and arranged between the second protection circuit and the constant current source so as to filter high-frequency interference. The normal work of the electroencephalogram impedance measuring system is ensured through the second protection circuit and the filter circuit, and further the accurate measurement of the electroencephalogram impedance is ensured.

According to a second aspect, an embodiment of the present invention provides a method for measuring brain electrical impedance based on the brain electrical impedance measurement system according to the first aspect or any implementation manner of the first aspect, including the following steps: the constant current source injects a current excitation signal into at least one electroencephalogram measurement channel so as to superpose the impedance signal and the electroencephalogram signal into an electroencephalogram measurement signal; the analog-to-digital conversion unit is used for converting the electroencephalogram measurement signal into a digital signal, wherein the signal frequency of the constant current source is a preset multiple of the sampling rate of the analog-to-digital conversion unit; the impedance measuring unit is used for calculating an impedance value corresponding to the electroencephalogram measuring signal based on the digital signal.

According to the method for measuring the electroencephalogram impedance, the current excitation signal is injected into at least one electroencephalogram measurement channel through the constant current source, so that the impedance signal and the electroencephalogram signal are superposed to form the electroencephalogram measurement signal, the electroencephalogram measurement signal is converted into the digital signal through the analog-to-digital conversion unit, and then the impedance value corresponding to the electroencephalogram measurement signal is calculated through the impedance measurement unit based on the digital signal sent by the analog-to-digital conversion unit. In the process of converting the electroencephalogram measurement signal into the digital signal, the signal frequency of the constant current source is set to be a preset multiple of the sampling rate of the analog-to-digital conversion unit, the electroencephalogram signal and the impedance signal output by the electroencephalogram measurement channel can be converted simultaneously, the electroencephalogram signal and the impedance signal are separated through frequency filtering, data conversion does not need to be separated, the data processing speed is improved, the digital signal corresponding to the electroencephalogram measurement signal is used for calculating the corresponding impedance value of the electroencephalogram measurement signal in real time, and therefore real-time electroencephalogram impedance detection is achieved.

With reference to the second aspect, in a first implementation manner of the second aspect, the calculating, based on the digital signal, an impedance value corresponding to the electroencephalogram measurement signal includes: acquiring a calibration coefficient; and determining an impedance value corresponding to the electroencephalogram measurement signal based on the calibration coefficient and the impedance signal, wherein the impedance signal is separated from the digital signal.

With reference to the first implementation manner of the first aspect, in a second implementation manner of the first aspect, the obtaining the calibration coefficient includes: sending a control instruction to the selector switch to control the conduction of at least one calibration branch; receiving an electric signal output by at least one electroencephalogram measurement channel after the at least one calibration branch is conducted; determining the calibration coefficient based on the electrical signal output by the at least one electroencephalogram measurement channel.

According to the electroencephalogram impedance measuring method provided by the embodiment of the invention, the calibration coefficient of at least one electroencephalogram measuring channel is obtained, and the impedance value corresponding to the electroencephalogram signal is corrected based on the calibration coefficient, so that the measurement precision of the impedance value of the electroencephalogram signal is improved.

According to a third aspect, an embodiment of the present invention provides an electroencephalogram impedance measuring apparatus, including: a memory and a processor, wherein the memory and the processor are communicatively connected with each other, the memory stores computer instructions, and the processor executes the computer instructions to execute the method for measuring brain electrical impedance according to the second aspect or any embodiment of the second aspect.

According to a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium, which stores computer instructions for causing a computer to execute the method for measuring brain electrical impedance according to the first aspect or any of the embodiments of the first aspect.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.

FIG. 1 is a schematic structural diagram of a brain electrical impedance measurement system according to an embodiment of the present invention;

FIG. 2 is another structural schematic diagram of a brain electrical impedance measurement system according to an embodiment of the invention;

FIG. 3 is another structural schematic diagram of a brain electrical impedance measurement system according to an embodiment of the present invention;

FIG. 4 is another schematic structural diagram of a brain electrical impedance measurement system according to an embodiment of the present invention;

FIG. 5 is another schematic diagram of the structure of the brain electrical impedance measurement system according to the embodiment of the invention;

FIG. 6 is another schematic structural diagram of a brain electrical impedance measurement system according to an embodiment of the present invention;

FIG. 7 is another structural schematic diagram of a brain electrical impedance measurement system according to an embodiment of the present invention;

FIG. 8 is a flow chart of a method of measuring brain electrical impedance according to an embodiment of the present invention;

FIG. 9 is another flow chart of a method of measuring brain electrical impedance according to an embodiment of the present invention;

fig. 10 is a schematic structural diagram of a brain electrical impedance measuring device provided according to an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The embodiment of the invention provides an electroencephalogram impedance measuring system, which comprises at least one electroencephalogram measuring channel 1, a constant current source 2, an analog-to-digital conversion unit 3 and an impedance measuring unit 4, as shown in figure 1. Wherein, the electrode of at least one electroencephalogram measurement channel 1 is contacted with the scalp, the constant current source 2 is respectively connected with at least one electroencephalogram measurement channel 1, and the constant current source 2 is used for providing a current excitation signal for at least one electroencephalogram measurement channel 1; the analog-to-digital conversion unit 3 is respectively connected with at least one electroencephalogram measurement channel 1, and the signal frequency of the constant current source 2 is a preset multiple of the sampling rate of the analog-to-digital conversion unit 3; the impedance measuring unit 4 is connected with the analog-to-digital conversion unit 3, and the electroencephalogram impedance is calculated based on the electrical signal of the electroencephalogram measuring channel 1 output by the analog-to-digital conversion unit 3.

Specifically, each electroencephalogram measurement channel 1 comprises two electrodes, the lead wire of each electroencephalogram measurement channel is in contact with the scalp through the two electrodes, and the potential difference between the two electrodes and the scalp contact point is acquired. The electroencephalogram impedance measurement of one of the electroencephalogram measurement channels is explained in detail here, and the electroencephalogram impedance measurement methods of the other electroencephalogram measurement channels are the same. In the process of measuring the electroencephalogram impedance, the constant current source 2 provides a current excitation signal for the electroencephalogram measurement channel, an alternating current signal is injected into the electroencephalogram measurement channel, a normal-phase current source and a reverse-phase current source are respectively added to two ends of the electroencephalogram measurement channel, the current is converted into voltage information through the electrode of the electroencephalogram measurement channel 1 and is superposed with the electroencephalogram signal collected by the electrode; the analog-to-digital conversion unit 3 converts the acquired voltage signal into a digital signal, and the digital signal comprises a brain electrical signal and an impedance signal; the impedance measuring unit 4 is connected with the analog-to-digital conversion unit 3, the impedance measuring unit 4 can receive the digital signal of the analog-to-digital conversion unit 3, separate the impedance signal from the digital signal, and calculate the electroencephalogram impedance value corresponding to the electroencephalogram measuring channel based on the impedance signal.

The signal frequency of the constant current source 2 is a preset multiple of the sampling rate of the analog-to-digital conversion unit 3 so that the electroencephalogram signal and the impedance signal can be converted together. Specifically, the preset multiple may be set to be one fourth, taking the sampling rate of the analog-to-digital conversion unit 3 as 500Hz as an example, the signal frequency of the constant current source 2 is 125Hz, and the amplitude is 6nA, it should be noted that the noise of the constant current source 2 should be as small as possible, so as to avoid generating a large influence on the electroencephalogram signal, and the current signal of the constant current source 2 flows in from the positive phase end, flows through the scalp and the electrode, and flows back to the analog-to-digital conversion unit 3 from the negative phase end.

The electroencephalogram impedance measuring system provided by the embodiment comprises at least one electroencephalogram measuring channel, a constant current source, an analog-to-digital conversion unit and an impedance measuring unit. The electrode of the electroencephalogram measurement channel is in contact with the scalp, the constant current source is connected with the at least one electroencephalogram measurement channel to provide a current excitation signal for the at least one electroencephalogram measurement channel, the analog-to-digital conversion unit is arranged in the at least one electroencephalogram measurement channel for connection, the frequency of the electroencephalogram signal is different from that of the impedance signal, the signal frequency of the constant current source is set to be a preset multiple of the sampling rate of the analog-to-digital conversion unit, so that the electroencephalogram signal and the impedance signal output by the electroencephalogram measurement channel are converted simultaneously, the electroencephalogram signal and the impedance signal are separated through frequency filtering, data do not need to be converted separately, the complexity of a circuit is reduced, and the cost is saved. The impedance measuring unit is connected with the analog-to-digital conversion unit, and can perform real-time detection on the electroencephalogram impedance based on the electrical signals of the electroencephalogram measuring channel, so that the electroencephalogram impedance measuring system has the advantages of circuit simplification and electroencephalogram impedance real-time detection.

The embodiment of the present invention further provides an electroencephalogram impedance measuring system, as shown in fig. 2, the electroencephalogram impedance measuring system includes at least one electroencephalogram measuring channel 11, a constant current source 21, an analog-to-digital conversion unit 31, and an impedance measuring unit 41. The impedance measuring unit 41 includes a frequency selecting module 411 and an impedance calculating module 412.

Specifically, the frequency selection module 411 is connected to an output terminal of the analog-to-digital conversion unit 31, and the impedance calculation module 412 is connected to an output terminal of the frequency selection module 411. The frequency selection module 411 may be a frequency domain filter, and since the frequency of the electroencephalogram signal is different from that of the impedance signal, and the frequency of the electroencephalogram signal is usually about 0.5 to 30Hz, the electroencephalogram signal and the impedance signal can be separated through the frequency domain filter, so that the separate conversion of the electroencephalogram signal and the impedance signal is avoided, the complexity of the circuit is reduced, and the cost is saved.

By separating the impedance signal from the digital signal through the frequency selecting module 411 and sending the impedance signal to the impedance calculating module 412, the impedance calculating module 412 may calculate a corresponding impedance value according to the impedance signal.

The electroencephalogram measurement channel 11, the constant current source 21, the analog-to-digital conversion unit 31, the frequency selection module 411 and the impedance calculation module 412 form an electroencephalogram impedance measurement loop, and the relationship between the voltage and the impedance of the measurement loop can be expressed as follows: v =2 × I1 × (Rp + Z1), where V is the voltage peak-to-peak value of the measurement loop, I1 is the current amplitude of the constant current source, rp is the equivalent series resistance in the measurement loop, and Z1 is the scalp-electrode contact impedance. The current amplitude I1 of the constant current source and the equivalent series resistance Rp can be determined by measurement based on the voltage peak-to-peak value V, so that the scalp-electrode contact impedance Z1 can be determined.

In the electroencephalogram impedance measuring system provided by the embodiment, the impedance measuring unit comprises a frequency selecting module and an impedance calculating module. The frequency selection module is connected with the output end of the analog-to-digital conversion unit and used for separating electroencephalogram signals and impedance signals of the electroencephalogram measurement signals, and the impedance calculation module is connected with the output end of the frequency selection module and used for calculating impedance values corresponding to the electroencephalogram signals. Because the frequency of the electroencephalogram signal is different from that of the impedance signal, the electroencephalogram signal and the impedance signal are separated through the frequency selection module, and the electroencephalogram signal and the impedance signal do not need to be converted separately, so that the complexity of a circuit is reduced.

The embodiment of the present invention further provides an electroencephalogram impedance measuring system, as shown in fig. 3, the electroencephalogram impedance measuring system includes at least one electroencephalogram measuring channel 12, a constant current source 22, an analog-to-digital conversion unit 32, an impedance measuring unit 42, a calibration unit 52, and at least one calibration branch 62. The calibration unit 52 is connected to the impedance measurement unit 42, and the calibration unit 52 is connected to the at least one electroencephalogram measurement channel 12 via at least one calibration branch 62. When the electrodes are in the shedding state, the calibration unit 52 can determine calibration coefficients for the at least one brain electrical measurement channel 12 based on the electrical signals of the at least one calibration branch 62.

Specifically, the electroencephalogram impedance calibration method of each electroencephalogram measurement channel is the same, and here, the electroencephalogram impedance measurement of one of the electroencephalogram measurement channels is explained in detail. In the process of calibrating the electroencephalogram impedance, the calibration unit 52 may control the calibration branch 62 connected to the electroencephalogram measurement channel 12, and calculate a calibration coefficient after the calibration branch 62, and the impedance measurement unit 42 may correct the electroencephalogram impedance according to the calibration coefficient.

Before the electroencephalogram impedance measurement is carried out, whether the electrode is in a falling state or not is detected, and if the electrode is in the falling state, the electroencephalogram impedance is corrected. The constant current source 22 provides a current excitation signal for the electroencephalogram measurement channel, injects an alternating current signal into the electroencephalogram measurement channel, and adds a positive current source and a negative current source at two ends of the electroencephalogram measurement channel 12 respectively. The calibration branch 62 simulates the contact impedance between the electrodes of the electroencephalographic measurement channel 12 and the scalp. The current reversely flows into the analog-to-digital conversion unit 32 through the brain electricity measuring channel 12 and the calibration branch 62 connected to the brain electricity measuring channel 12. The analog-to-digital conversion unit 32 converts the analog voltage signal into a digital signal, the impedance measurement unit 42 is connected to the analog-to-digital conversion unit 32, and the impedance measurement unit 42 can receive the digital signal of the analog-to-digital conversion unit 32 and calculate a calibration electroencephalogram impedance value after the calibration branch 62 is connected based on the digital signal.

The calibration unit 52 may be provided with a controller 521 and a processor 522, when calibrating the electroencephalogram impedance, the controller 521 may control the calibration branch 62 connected to the electroencephalogram measurement channel 12, and the processor 522 calculates a calibration coefficient of the electroencephalogram impedance of the electroencephalogram measurement channel 12 connected to the calibration branch 62, and stores the calibration coefficient, so that the impedance measurement unit 42 may correct the electroencephalogram impedance value according to the calibration coefficient in the real-time electroencephalogram impedance detection process.

The electroencephalogram impedance measuring system provided by the embodiment further comprises a calibration unit connected with the impedance measuring unit, and the calibration unit is connected with at least one electroencephalogram measuring channel through at least one calibration branch and used for determining a calibration coefficient of the at least one electroencephalogram measuring channel based on an electric signal of the at least one calibration branch. The impedance value calculated by the impedance measuring unit is corrected through the calibration coefficient, so that the measurement accuracy of the impedance value is improved.

Optionally, as shown in fig. 4, the calibration branch 62 may include: at least one calibration resistor 621 and a switch 622. Wherein, two ends of at least one group of calibration resistors 621 are respectively connected to the electroencephalogram measurement channel 12; the switch is connected to the calibration unit 52, and the calibration unit 52 can control the action of the switch 622 to control the conducting state of the corresponding calibration branch 62.

Specifically, the calibration resistor 621 may be a fixed resistor, and one set of calibration resistors 621 may include two sets of precision fixed resistors R1 and R2 for simulating contact impedances Z1 and Z2 between the electrode and the scalp, and also for limiting current. In the calibration, Z1 and Z2 are in the off state. The switch may be an analog switch, or may be another control switch, which is not limited herein.

The controller 521 of the calibration unit 52 may control the switch 622 on the R1 loop to be closed, the switch 622 on the R2 loop to be opened, and the constant current source 22 flows through R1, where the relationship between the R1 loop and the voltage V1 may be obtained as follows: v1=2 × a × I1 × (Rp + R1+ b); the controller 521 of the calibration unit 52 may control the switch 622 on the R1 loop to be opened, the switch 622 on the R2 loop to be closed, and the constant current source 22 flows through R2, where the relationship between the R2 loop and the voltage V2 may be obtained as follows: v2=2 × a × I1 × (Rp + R2+ b); the calibration coefficients a and b are obtained by combining the two relations, and the calculated calibration coefficients a and b are stored in the processor of the calibration unit 52.

Optionally, as shown in fig. 5, the switch 622 may also be connected with the controller 521 of the calibration unit 52 through an external control unit 624. The external control unit 624 can be externally connected to the electroencephalogram impedance measuring system, and can be used as an independent tool to realize calibration. The calibration resistor 621 may be connected to the electroencephalogram measurement channel to measure electroencephalogram impedance. After the external control unit 624 establishes communication connection with the controller 521 of the calibration unit 52 through the digital communication interface, the controller 521 can indirectly control the on-off of the switch 622, so as to realize the switching between the R1 loop and the R2 loop.

The calculation process of the calibration coefficient may then comprise the following steps: the controller 521 and the external control unit 624 establish communication connection, and the external control unit 624 controls the switch 622; the external control unit 624 controls the switch 622 on the R1 loop to close, the switch 622 on the R2 loop to open, and the constant current source 22 flows through the R1 loop, at this time, the relationship between the R1 loop and the voltage V1 can be obtained as follows: v1=2 × a × I1 × (Rp + R1+ b); the external control unit 624 controls the switch 622 on the R1 loop to open, the switch 622 on the R2 loop to close, and the constant current source 22 flows through the R2 loop, so that the relationship between the R2 loop and the voltage V2 can be obtained as follows: v2=2 × a × I1 × (Rp + R2+ b); the calibration coefficients a and b can be obtained by combining the above two relations and saved in the processor of the calibration unit 52. After the calibration is completed, the connection between the calibration unit 52 and the electroencephalogram measurement channel is disconnected, so as to perform real-time detection on electroencephalogram impedance.

According to the electroencephalogram impedance measuring system provided by the embodiment of the invention, the calibration branch comprises at least one group of calibration resistors and a selector switch. Wherein, two ends of each group of calibration branches are connected into corresponding electroencephalogram measurement channels; the switch is connected with the calibration unit, and the calibration unit is used for controlling the action of the switch so as to control the conducting state of the corresponding calibration branch. The calibration coefficient of the electroencephalogram measurement channel is determined through the calibration resistor and the switch to correct the impedance value calculated by the impedance measurement unit, so that the complexity of the impedance detection circuit is simplified, the influence of the calibration circuit on the electroencephalogram measurement channel is avoided, and the measurement accuracy of the impedance value is improved.

Optionally, as shown in fig. 6, the calibration branch 62 may further include a first protection circuit 623. One end of the first protection circuit 623 is connected to the switch 622, and the other end is connected to at least one calibration resistor 621. The first protection circuit 623 is used to protect the components of the calibration branch 62, i.e., the switch 622 and the calibration resistor 621, from high-frequency interference such as electrosurgery and defibrillation, so as to prevent overvoltage damage.

In the electroencephalogram impedance measuring system provided by this embodiment, the calibration branch further includes a first protection circuit, one end of which is connected to the switch, and the other end of which is connected to at least one set of calibration resistors. The device of the calibration branch circuit is protected through the first protection circuit, overvoltage damage of the calibration branch circuit is prevented, and interference of external high frequency to the calibration branch circuit is prevented.

The embodiment of the present invention provides an electroencephalogram impedance measuring system, as shown in fig. 7, the electroencephalogram impedance measuring system includes at least one electroencephalogram measuring channel 13, a constant current source 23, an analog-to-digital conversion unit 33, a frequency selecting module 43, an impedance calculating module 53, a second protection circuit 63, a filter circuit 73, a calibration branch 83, and a calibration unit 93. Wherein, the electrode of at least one brain electricity measuring channel 13 is contacted with the scalp, the constant current source 23 is respectively connected with at least one brain electricity measuring channel 13, the constant current source 23 is used for providing current excitation signal for at least one brain electricity measuring channel 13; the analog-to-digital conversion unit 33 is respectively connected with at least one electroencephalogram measurement channel 13, and the signal frequency of the constant current source 23 is a preset multiple of the sampling rate of the analog-to-digital conversion unit 33; the frequency selecting module 43 is connected with the output end of the analog-to-digital conversion unit 33, an impedance signal is separated from the digital signal output by the analog-to-digital conversion unit 33, the impedance calculating module 53 is connected with the output end of the frequency selecting module 43, and the impedance calculating module 53 calculates the electroencephalogram impedance based on the impedance signal output by the frequency selecting module 43. The second protection circuit 63 is respectively connected with at least one electroencephalogram measurement channel 13, and the second protection circuit 63 is arranged in front of the constant current source 23 and used for protecting the circuit units arranged behind the constant current source; the filter circuit 73 is respectively connected with at least one electroencephalogram measurement channel 13, and the filter circuit 73 is arranged between the second protection circuit 63 and the constant current source 23, and is used for filtering high-frequency interference.

Specifically, the second protection circuit 63 includes only neon tubes, clamping diodes, and other devices, and the filter circuit 73 is a low-pass filter circuit. The protection resistor of the second protection circuit 63 may be equivalent to the equivalent series resistor Rp of the filter circuit 73. In the process of measuring the electroencephalogram impedance, the constant current source 23 provides a current excitation signal for the electroencephalogram measurement channel, an alternating current signal is injected into the electroencephalogram measurement channel, a normal-phase current source and a reverse-phase current source are respectively added at two ends of the electroencephalogram measurement channel, the current passes through the equivalent series resistor Rp of the filter circuit 73, the second protection circuit 63 and the electrode of the electroencephalogram measurement channel 13, the current is converted into voltage information, and the voltage information is superposed with the electroencephalogram signal collected by the electrode; the analog-to-digital conversion unit 33 converts the acquired voltage signal into a digital signal, and the data signal includes a brain electrical signal and an impedance signal; the frequency selection module 43 is connected to the analog-to-digital conversion unit 33, receives the digital signal of the analog-to-digital conversion unit 33, and separates an impedance signal from the digital signal, and the impedance calculation module can calculate the electroencephalogram impedance value corresponding to the electroencephalogram measurement channel based on the impedance signal.

The signal frequency of the constant current source 23 is a preset multiple of the sampling rate of the analog-to-digital conversion unit 33 so that the electroencephalogram signal and the impedance signal can be converted together. The current signal of the constant current source 23 flows in from the positive phase terminal, flows through the scalp and the electrodes, and flows back to the analog-to-digital conversion unit 33 from the negative phase terminal.

In the electroencephalogram impedance calibration process, the contact impedance between the electrode of the electroencephalogram measurement channel and the scalp is simulated through the calibration branch 83, and the electroencephalogram impedance calibration coefficient in the electroencephalogram measurement process is calculated through the calibration unit 93. In the electroencephalogram measurement process, the impedance calculation unit can acquire the calibration coefficient calculated by the calibration unit 93, and correct the impedance value of the electroencephalogram signal according to the calibration coefficient so as to ensure the measurement accuracy of the electroencephalogram impedance.

The electroencephalogram impedance measuring system provided by the embodiment further comprises a second protection circuit and a filter circuit. The second protection circuit is respectively connected with at least one electroencephalogram measurement channel and is arranged in front of the constant current source so as to protect the circuit unit arranged behind the second protection circuit; the filter circuit is respectively connected with at least one electroencephalogram measurement channel and arranged between the second protection circuit and the constant current source so as to filter high-frequency interference. The normal work of the electroencephalogram impedance measuring system is ensured through the second protection circuit and the filter circuit, and further the accurate measurement of the electroencephalogram impedance is ensured.

In accordance with an embodiment of the present invention, there is provided an embodiment of a method for measuring brain electrical impedance, it being noted that the steps illustrated in the flowchart of the drawings may be carried out in a computer system such as a set of computer-executable instructions, and that while a logical order is illustrated in the flowchart, in some cases, the steps illustrated or described may be carried out in an order different than here.

In this embodiment, a method for measuring brain electrical impedance is provided, which can be used in the brain electrical impedance measurement system, for example, a brain electrical impedance measurement system of a medical device, fig. 8 is a flowchart of a method for measuring brain electrical impedance according to an embodiment of the present invention, as shown in fig. 8, the flowchart includes the following steps:

s11, injecting a current excitation signal into at least one electroencephalogram measurement channel by the constant current source so as to enable the impedance signal and the electroencephalogram signal to be superposed into an electroencephalogram measurement signal.

At least one electroencephalogram impedance measurement channel in the electroencephalogram impedance measurement system is in contact with the scalp through an electrode, and the at least one electroencephalogram impedance measurement channel can form a lead system. Each electroencephalogram measurement channel in the lead system can comprise a measurement lead and a drive lead, one end of each lead is in contact with the scalp through an electrode to induce an electroencephalogram signal, and meanwhile, contact impedance between the electrode and the scalp is generated to form an impedance signal.

The constant current source provides a current excitation signal for at least one electroencephalogram measurement channel, an alternating current signal is injected into the electroencephalogram measurement channel, the impedance signal and the electroencephalogram signal collected by the electrode are superposed to form an electroencephalogram measurement signal, and the electroencephalogram measurement signal collected by the electrode is sent to the analog-to-digital conversion unit.

And S12, the analog-to-digital conversion unit is used for converting the electroencephalogram measurement signal into a digital signal, wherein the signal frequency of the constant current source is a preset multiple of the sampling rate of the analog-to-digital conversion unit.

The signal frequency of the constant current source is a preset multiple of the sampling rate of the analog-to-digital conversion unit, so that the analog-to-digital conversion unit can simultaneously convert the electroencephalogram signal and the impedance signal contained in the electroencephalogram measurement signal into a digital signal without separate conversion. The analog-to-digital conversion unit sends the electroencephalogram measurement signal converted into the digital signal to the impedance measurement unit.

And S13, the impedance measuring unit is used for calculating an impedance value corresponding to the electroencephalogram measuring signal based on the digital signal.

The impedance measuring unit of the electroencephalogram impedance measuring system can receive the digital signal sent by the analog-to-digital conversion unit, separate the electroencephalogram signal and the impedance signal contained in the digital signal, and calculate the impedance value corresponding to the separated impedance signal, wherein the impedance value is the impedance value corresponding to the electroencephalogram measuring signal.

According to the electroencephalogram impedance measuring method, in the process of converting the electroencephalogram measurement signal into the digital signal, the signal frequency of the constant current source is set to be the preset multiple of the sampling rate of the analog-to-digital conversion unit, the electroencephalogram signal and the impedance signal output by the electroencephalogram measurement channel can be converted simultaneously, the electroencephalogram signal and the impedance signal are separated through frequency filtering, data conversion is not needed separately, the data processing speed is increased, the impedance value of the electroencephalogram measurement signal is calculated in real time based on the digital signal corresponding to the electroencephalogram measurement signal, and therefore real-time detection of the electroencephalogram impedance is achieved.

In this embodiment, a method for measuring brain electrical impedance is provided, which can be used in the brain electrical impedance measuring system, for example, a brain electrical impedance measuring system of a medical device, and fig. 9 is a flowchart of the method for measuring brain electrical impedance according to the embodiment of the present invention, as shown in fig. 9, the flowchart includes the following steps:

and S21, injecting a current excitation signal into at least one electroencephalogram measurement channel by the constant current source so as to superpose the impedance signal and the electroencephalogram signal into an electroencephalogram measurement signal. For a detailed description, refer to the related description of step S11 corresponding to the above embodiment, which is not repeated herein.

And S22, the analog-to-digital conversion unit is used for converting the electroencephalogram measurement signal into a digital signal, wherein the signal frequency of the constant current source is a preset multiple of the sampling rate of the analog-to-digital conversion unit. For a detailed description, refer to the related description of step S12 corresponding to the above embodiment, which is not repeated herein.

And S23, the impedance measuring unit is used for calculating an impedance value corresponding to the electroencephalogram measuring signal based on the digital signal.

Specifically, the step S23 may include the following steps:

and S231, acquiring a calibration coefficient.

The calibration coefficient is a coefficient for correcting the electroencephalogram impedance, and is convenient for accurately detecting the real-time detection of the electroencephalogram impedance in the electroencephalogram measurement process. The calibration coefficient can be calculated by a processor of the calibration unit, and the impedance measurement unit of the electroencephalogram impedance measurement system can receive the calibration coefficient calculated by the calibration unit.

Specifically, the step S231 may include the following steps:

(1) And sending a control command to the selector switch to control the conduction of the at least one calibration branch.

Before the impedance calibration is started, the impedance of each electroencephalogram measurement channel is measured, and at the moment, the falling state between the electrodes and the scalp is required to be met. The switch-on or switch-off of the switch is controlled to control the calibration branch accessed to the electroencephalogram measurement channel, and the relationship between the impedance and the voltage of the current loop is determined according to the accessed calibration branch.

(2) And receiving the electric signal output by the at least one electroencephalogram measurement channel after the at least one calibration branch is conducted.

The electric signal is a signal relation between the loop voltage and the loop impedance of the electroencephalogram measurement channel. Different calibration branches are connected to obtain different signal relations between the loop voltage and the loop impedance, and the calibration unit of the electroencephalogram impedance measurement system can receive the electrical signals output by the electroencephalogram measurement channel after the conduction of the different calibration branches.

(3) Determining a calibration coefficient based on the electrical signal output by the at least one electroencephalogram measurement channel.

The calibration coefficients in the signal relational expression can be obtained through calculation by combining different groups of signal relational expressions, and the calibration coefficients are stored in a calibration unit of the electroencephalogram impedance measurement system, so that the electroencephalogram impedance measurement system can correct electroencephalogram impedance in the process of detecting electroencephalogram impedance in real time, and the electroencephalogram impedance can be accurately detected.

S232, determining an impedance value corresponding to the electroencephalogram measurement signal based on the calibration coefficient and the impedance signal.

The impedance signal is separated from the digital signal corresponding to the electroencephalogram measurement signal. The electroencephalogram impedance measurement system can determine an impedance value in the electroencephalogram measurement signal based on the impedance signal, and receive the calibration coefficient calculated by the calibration unit to correct the impedance value corresponding to the electroencephalogram measurement signal.

According to the electroencephalogram impedance measuring method provided by the embodiment, the calibration coefficient of at least one electroencephalogram measurement channel is obtained, and the impedance value corresponding to the electroencephalogram signal is corrected based on the calibration coefficient, so that the measurement accuracy of the impedance value of the electroencephalogram signal is improved.

An embodiment of the present invention further provides an electroencephalogram impedance measuring device, please refer to fig. 10, fig. 10 is a schematic structural diagram of an electroencephalogram impedance measuring device provided in an alternative embodiment of the present invention, and as shown in fig. 10, the electroencephalogram impedance measuring device may include: at least one processor 401, such as a CPU (Central Processing Unit), at least one communication interface 403, memory 404, and at least one communication bus 402. Wherein a communication bus 402 is used to enable connective communication between these components. The communication interface 403 may include a Display (Display) and a Keyboard (Keyboard), and the optional communication interface 403 may also include a standard wired interface and a standard wireless interface. The Memory 404 may be a high-speed RAM Memory (volatile Random Access Memory) or a non-volatile Memory (non-volatile Memory), such as at least one disk Memory. The memory 404 may optionally be at least one memory device located remotely from the processor 401. Wherein the processor 401 may be combined with the system described in fig. 1 to 7, the memory 404 stores an application program, and the processor 401 calls the program code stored in the memory 404 for performing any of the above method steps.

The communication bus 402 may be a Peripheral Component Interconnect (PCI) bus, an Extended Industry Standard Architecture (EISA) bus, or the like. The communication bus 402 may be divided into an address bus, a data bus, a control bus, and the like. For ease of illustration, only one thick line is shown in FIG. 10, but this is not intended to represent only one bus or type of bus.

The memory 404 may include a volatile memory (RAM), such as a random-access memory (RAM); the memory may also include a non-volatile memory (english: flash memory), such as a Hard Disk Drive (HDD) or a solid-state drive (SSD); the memory 404 may also comprise a combination of the above types of memory.

The processor 401 may be a Central Processing Unit (CPU), a Network Processor (NP), or a combination of a CPU and an NP.

The processor 401 may further include a hardware chip. The hardware chip may be an application-specific integrated circuit (ASIC), a Programmable Logic Device (PLD), or a combination thereof. The PLD may be a Complex Programmable Logic Device (CPLD), a field-programmable gate array (FPGA), a General Array Logic (GAL), or any combination thereof.

Optionally, the memory 404 is also used to store program instructions. The processor 401 may call program instructions to implement the electroencephalogram impedance measuring method as shown in the embodiments of fig. 8 and fig. 9 of the present application.

The embodiment of the invention also provides a non-transitory computer storage medium, wherein the computer storage medium stores computer executable instructions, and the computer executable instructions can execute the processing method of the electroencephalogram impedance measuring method in any method embodiment. The storage medium may be a magnetic Disk, an optical Disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a Flash Memory (Flash Memory), a Hard Disk (Hard Disk Drive, abbreviated as HDD), a Solid State Drive (SSD), or the like; the storage medium may also comprise a combination of memories of the kind described above.

Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations fall within the scope defined by the appended claims.

Claims (12)

1. An electroencephalogram impedance measurement system, comprising:

at least one electroencephalogram measurement channel, the electrodes of which are used to contact the scalp;

the constant current source is respectively connected with the at least one electroencephalogram measurement channel and is used for providing a current excitation signal for the at least one electroencephalogram measurement channel;

the analog-to-digital conversion unit is respectively connected with the at least one electroencephalogram measurement channel, and the signal frequency of the constant current source is a preset multiple of the sampling rate of the analog-to-digital conversion unit;

and the impedance measuring unit is connected with the analog-to-digital conversion unit and used for calculating the electroencephalogram impedance based on the electrical signals of the electroencephalogram measuring channel.

2. The system of claim 1, wherein the impedance measurement unit comprises:

the frequency selection module is connected with the output end of the analog-to-digital conversion unit and is used for separating electroencephalogram signals and impedance signals of the electroencephalogram measurement signals;

and the impedance calculation module is connected with the output end of the frequency selection module and used for calculating an impedance value corresponding to the impedance signal.

3. The system of claim 1, further comprising:

the calibration unit is connected with the at least one electroencephalogram measurement channel through at least one calibration branch and used for determining a calibration coefficient of the at least one electroencephalogram measurement channel based on an electric signal of the at least one calibration branch.

4. The system of claim 3, further comprising:

the at least one calibration branch is connected with the calibration unit.

5. The system according to claim 3 or 4, characterized in that said calibration branch comprises:

the two ends of each group of calibration branch are connected into the corresponding electroencephalogram measurement channel;

and the calibration unit is used for controlling the action of the selector switch so as to control the conduction state of the corresponding calibration branch.

6. The system of claim 5, wherein the calibration branch further comprises:

and one end of the first protection circuit is connected with the change-over switch, and the other end of the first protection circuit is connected with the at least one group of calibration resistors.

7. The system of claim 1, further comprising:

the second protection circuit is respectively connected with the at least one electroencephalogram measurement channel and is arranged in front of the constant current source, and the second protection circuit is used for protecting a circuit unit arranged behind the second protection circuit;

and the filter circuit is respectively connected with the at least one electroencephalogram measurement channel and arranged between the second protection circuit and the constant current source, and the filter circuit is used for filtering high-frequency interference.

8. The electroencephalogram impedance measuring method based on the electroencephalogram impedance measuring system of any one of claims 1 to 7, characterized by comprising the following steps:

the constant current source injects a current excitation signal into at least one electroencephalogram measurement channel so as to superpose the impedance signal and the electroencephalogram signal into an electroencephalogram measurement signal;

the analog-to-digital conversion unit is used for converting the electroencephalogram measurement signal into a digital signal, wherein the signal frequency of the constant current source is a preset multiple of the sampling rate of the analog-to-digital conversion unit;

the impedance measuring unit is used for calculating an impedance value corresponding to the electroencephalogram measuring signal based on the digital signal.

9. The method of claim 8, wherein said calculating an impedance value corresponding to said brain electrical measurement signal based on said digital signal comprises:

acquiring a calibration coefficient;

and determining an impedance value corresponding to the electroencephalogram measurement signal based on the calibration coefficient and the impedance signal, wherein the impedance signal is separated from the digital signal.

10. The method of claim 9, wherein obtaining the calibration coefficients comprises:

sending a control instruction to the selector switch to control the conduction of at least one calibration branch;

receiving an electric signal output by at least one electroencephalogram measurement channel after the at least one calibration branch is conducted;

determining the calibration coefficient based on the electrical signal output by the at least one electroencephalogram measurement channel.

11. An electroencephalogram impedance measuring apparatus, comprising:

a memory and a processor, the memory and the processor being communicatively connected to each other, the memory having stored therein computer instructions, the processor executing the computer instructions to perform the method of measuring brain electrical impedance of any one of claims 8-10.

12. A computer-readable storage medium characterized in that it stores computer instructions for causing the computer to execute the method of measuring brain electrical impedance of any one of claims 8-10.

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