A brain electrical impedance measurement system and a method of measuring brain electrical impedance

Abstract

The application relates to the technical field of electroencephalogram measurement, and discloses an electroencephalogram impedance measurement system and an electroencephalogram impedance measurement method. The electroencephalogram impedance measurement system comprises at least one electroencephalogram measurement channel, electrodes of the electroencephalogram measurement channel are used for being in contact with the scalp, a constant current source is connected with the at least one electroencephalogram measurement channel, the constant current source is used for providing a current excitation signal to the at least one electroencephalogram measurement channel, an analog-to-digital conversion unit is connected with the at least one electroencephalogram measurement channel, a signal frequency of the constant current source is a preset multiple of a sampling rate of the analog-to-digital conversion unit, and an impedance measurement unit is connected with the analog-to-digital conversion unit and is used for calculating electroencephalogram impedance based on an electric signal of the electroencephalogram measurement channel. Through implementation of the application, the complexity of a circuit is reduced, cost is saved, real-time detection of electroencephalogram impedance is realized, and both circuit simplification and real-time detection of electroencephalogram impedance are considered.

Description

Technical Field

[0001] This invention relates to the field of electroencephalography (EEG) measurement technology, specifically to a brain electrical impedance measurement system and a method for measuring brain electrical impedance. Background Technology

[0002] Electroencephalogram (EEG) signals can be detected using multiple electrodes on an EEG measuring device. Because EEG signals are very weak, the contact impedance between the electrodes and the scalp has a significant impact on the signal. Typically, EEG measuring devices have an electrode contact impedance detection function to reflect the current electrode connection status. However, some EEG measuring devices can only detect contact impedance before EEG signal measurement, or require stopping normal measurement before detection. Although some EEG measuring devices can perform real-time contact impedance detection during EEG signal measurement, this requires a separate impedance detection circuit, making the circuitry of the EEG measuring device relatively complex. Summary of the Invention

[0003] In view of this, embodiments of the present invention provide a brain electrical impedance measurement system and a method for measuring brain electrical impedance, in order to solve the problem of the difficulty in simultaneously achieving circuit simplification and real-time detection of contact impedance.

[0004] According to a first aspect, embodiments of the present invention provide a brain electrical impedance measurement system, comprising: at least one electroencephalogram (EEG) measurement channel, wherein electrodes of the EEG measurement channel are used to contact the scalp; a constant current source connected to the at least one EEG measurement channel, the constant current source being used to provide a current excitation signal to the at least one EEG measurement channel; an analog-to-digital converter (ADC) unit connected to the at least one EEG measurement channel, wherein the signal frequency of the constant current source is a preset multiple of the sampling rate of the ADC unit; and an impedance measurement unit connected to the ADC unit, used to calculate brain electrical impedance based on the electrical signals of the EEG measurement channels.

[0005] The brain electrical impedance measurement system provided in this invention includes at least one EEG measurement channel, a constant current source, an analog-to-digital converter (ADC), and an impedance measurement unit. The electrodes of the EEG measurement channel are in contact with the scalp. The constant current source is connected to at least one EEG measurement channel to provide a current excitation signal. The ADC is connected to at least one EEG measurement channel. Since the frequencies of the EEG signal and the impedance signal are different, the signal frequency of the constant current source is set to a preset multiple of the sampling rate of the ADC, so that the EEG signal and impedance signal output from the EEG measurement channel can be converted simultaneously. Then, the two signals are separated by frequency filtering, eliminating the need for separate data conversion, reducing circuit complexity, and saving costs. The impedance measurement unit is connected to the ADC, enabling real-time detection of brain electrical impedance based on the electrical signals from the EEG measurement channel. Therefore, this brain electrical impedance measurement system combines circuit simplification with real-time brain electrical impedance detection.

[0006] In conjunction with the first aspect, in the first embodiment of the first aspect, the impedance measurement unit includes: a frequency selection module connected to the output terminal of the analog-to-digital conversion unit, used to separate the EEG signal and impedance signal of the EEG measurement signal; and an impedance calculation module connected to the output terminal of the frequency selection module, used to calculate the impedance value corresponding to the impedance signal.

[0007] The brain electrical impedance measurement system provided in this invention includes an impedance measurement unit comprising a frequency selection module and an impedance calculation module. The frequency selection module is connected to the output of the analog-to-digital converter and is used to separate the electroencephalogram (EEG) signal and the impedance signal from the EEG measurement signal. The impedance calculation module is connected to the output of the frequency selection module and is used to calculate the impedance value corresponding to the EEG signal. Since the EEG signal and the impedance signal have different frequencies, separating the EEG signal and the impedance signal through the frequency selection module eliminates the need for separate conversion between the EEG signal and the impedance signal, thereby reducing circuit complexity.

[0008] In conjunction with the first aspect, in a second embodiment of the first aspect, the system further includes: a calibration unit connected to the impedance measurement unit, the calibration unit being connected to the at least one EEG measurement channel via at least one calibration branch, for determining the calibration coefficient of the at least one EEG measurement channel based on the electrical signal of the at least one calibration branch.

[0009] In conjunction with the second embodiment of the first aspect, in the third embodiment of the first aspect, the system further includes: the at least one calibration branch, the at least one calibration branch being connected to the calibration unit.

[0010] The brain electrical impedance measurement system provided in this embodiment of the invention further includes a calibration unit connected to the impedance measurement unit. This calibration unit is connected to at least one EEG measurement channel via at least one calibration branch, and is used to determine the calibration coefficient of at least one EEG measurement channel based on the electrical signal of the at least one calibration branch. The impedance value calculated by the impedance measurement unit is corrected using this calibration coefficient, thereby improving the measurement accuracy of the impedance value.

[0011] In conjunction with the second or third embodiment of the first aspect, in the fourth embodiment of the first aspect, the calibration branch includes: at least one set of calibration resistors, with both ends of each set of calibration branches connected to the corresponding EEG measurement channel; and a switching switch connected to the calibration unit, wherein the calibration unit is used to control the action of the switching switch to control the conduction state of the corresponding calibration branch.

[0012] The brain electrical impedance measurement system provided in this invention includes a calibration branch comprising at least one set of calibration resistors and a switching switch. Each calibration branch has its two ends connected to a corresponding EEG measurement channel. The switching switch is connected to a calibration unit, which controls the operation of the switching switch to control the conduction state of the corresponding calibration branch. By determining the calibration coefficient of the EEG measurement channel through the calibration resistors and the switching switch, the impedance value calculated by the impedance measurement unit is corrected, thereby improving the measurement accuracy of the impedance value.

[0013] In conjunction with the fourth embodiment of the first aspect, in the fifth embodiment of the first aspect, the calibration branch further includes: a first protection circuit, one end of which is connected to the switching switch and the other end of which is connected to the at least one set of calibration resistors.

[0014] The brain electrical impedance measurement system provided in this embodiment of the invention further includes a first protection circuit in its calibration branch. One end of the first protection circuit is connected to a switch, and the other end is connected to at least one set of calibration resistors. The first protection circuit protects the devices in the calibration branch from overvoltage damage and also prevents external high-frequency interference to the calibration branch.

[0015] In conjunction with the first aspect, in the sixth embodiment of the first aspect, the system further includes: a second protection circuit, connected to the at least one EEG measurement channel and disposed before the constant current source, the second protection circuit being used to protect the circuit unit disposed thereafter; and a filter circuit, connected to the at least one EEG measurement channel and disposed between the second protection circuit and the constant current source, the filter circuit being used to filter out high-frequency interference.

[0016] The brain electrical impedance measurement system provided in this embodiment of the invention further includes a second protection circuit and a filtering circuit. The second protection circuit is connected to at least one EEG measurement channel and is positioned before the constant current source to protect the subsequent circuit units. The filtering circuit is connected to at least one EEG measurement channel and is positioned between the second protection circuit and the constant current source to filter out high-frequency interference. The second protection circuit and the filtering circuit ensure the normal operation of the brain electrical impedance measurement system, thereby guaranteeing accurate measurement of brain electrical impedance.

[0017] According to a second aspect, embodiments of the present invention provide a method for measuring brain electrical impedance based on the brain electrical impedance measurement system described in the first aspect or any embodiment of the first aspect, comprising the following steps: a constant current source injects a current excitation signal into at least one brain electrical measurement channel to superimpose an impedance signal and a brain electrical signal to form a brain electrical measurement signal; an analog-to-digital conversion unit is used to convert the brain electrical 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; and an impedance measurement unit is used to calculate the impedance value corresponding to the brain electrical measurement signal based on the digital signal.

[0018] The brain impedance measurement method provided in this invention injects a current excitation signal into at least one EEG measurement channel using a constant current source, causing the impedance signal and the EEG signal to be superimposed to form an EEG measurement signal. An analog-to-digital converter (ADC) then converts the EEG measurement signal into a digital signal. Finally, an impedance measurement unit calculates the impedance value corresponding to the EEG measurement signal based on the digital signal sent by the ADC. During the conversion of the EEG measurement signal into a digital signal, by setting the signal frequency of the constant current source to a preset multiple of the sampling rate of the ADC, both the EEG signal and the impedance signal output from the EEG measurement channel can be converted simultaneously. The two signals are then separated by frequency filtering, eliminating the need for separate data conversion and improving data processing speed. Real-time calculation of the impedance value corresponding to the EEG measurement signal based on the digital signal enables real-time detection of brain impedance.

[0019] In conjunction with the second aspect, in the first embodiment of the second aspect, the step of calculating the impedance value corresponding to the EEG measurement signal based on the digital signal includes: obtaining a calibration coefficient; and determining the impedance value corresponding to the EEG measurement signal based on the calibration coefficient and the impedance signal, wherein the impedance signal is separated from the digital signal.

[0020] In conjunction with the first embodiment of the first aspect, in the second embodiment of the first aspect, obtaining the calibration coefficient includes: sending a control command to a switching switch to control the conduction of at least one calibration branch; receiving an electrical signal output from at least one EEG measurement channel after the at least one calibration branch is conducted; and determining the calibration coefficient based on the electrical signal output from the at least one EEG measurement channel.

[0021] The brain impedance measurement method provided in this embodiment of the invention improves the measurement accuracy of the brain signal impedance value by obtaining the calibration coefficient of at least one brain measurement channel and correcting the impedance value corresponding to the brain signal based on the calibration coefficient.

[0022] According to a third aspect, an embodiment of the present invention provides a brain electrical impedance measurement device, comprising: a memory and a processor, wherein the memory and the processor are communicatively connected to each other, the memory stores computer instructions, and the processor executes the computer instructions to perform the brain electrical impedance measurement method described in the second aspect or any embodiment of the second aspect.

[0023] According to a fourth aspect, embodiments of the present invention provide a computer-readable storage medium storing computer instructions for causing the computer to perform the brain electrical impedance measurement method described in the first aspect or any embodiment of the first aspect. Attached Figure Description

[0024] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of the brain electrical impedance measurement system according to an embodiment of the present invention;

[0026] Figure 2 This is another schematic diagram of the brain electrical impedance measurement system according to an embodiment of the present invention;

[0027] Figure 3 This is another schematic diagram of the brain electrical impedance measurement system according to an embodiment of the present invention;

[0028] Figure 4 This is another schematic diagram of the brain electrical impedance measurement system according to an embodiment of the present invention;

[0029] Figure 5This is another schematic diagram of the brain electrical impedance measurement system according to an embodiment of the present invention;

[0030] Figure 6 This is another schematic diagram of the brain electrical impedance measurement system according to an embodiment of the present invention;

[0031] Figure 7 This is another schematic diagram of the brain electrical impedance measurement system according to an embodiment of the present invention;

[0032] Figure 8 This is a flowchart of a method for measuring brain electrical impedance according to an embodiment of the present invention;

[0033] Figure 9 This is another flowchart of a method for measuring brain electrical impedance according to an embodiment of the present invention;

[0034] Figure 10 This is a schematic diagram of the structure of a brain electrical impedance measuring device provided in an embodiment of the present invention. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] This invention provides a brain electrical impedance measurement system, such as... Figure 1 As shown, the brain electrical impedance measurement system includes at least one EEG measurement channel 1, a constant current source 2, an analog-to-digital converter (ADC) unit 3, and an impedance measurement unit 4. The electrodes of at least one EEG measurement channel 1 are in contact with the scalp. The constant current source 2 is connected to at least one EEG measurement channel 1 and provides a current excitation signal to it. The ADC unit 3 is connected to at least one EEG measurement channel 1, and the signal frequency of the constant current source 2 is a preset multiple of the sampling rate of the ADC unit 3. The impedance measurement unit 4 is connected to the ADC unit 3 and calculates the brain electrical impedance based on the electrical signal from the EEG measurement channel 1 output by the ADC unit 3.

[0037] Specifically, each EEG measurement channel 1 includes two electrodes. The lead wire of each EEG measurement channel contacts the scalp through the two electrodes, and the potential difference between the two electrodes and the scalp contact points is collected. The EEG impedance measurement of one EEG measurement channel is described in detail here; the EEG impedance measurement method for other EEG measurement channels is the same. During the EEG impedance measurement process, a constant current source 2 provides a current excitation signal to the EEG measurement channel, injecting an alternating current signal into the EEG measurement channel. A positive-phase current source and a negative-phase current source are added to both ends of the EEG measurement channel, respectively. The current is converted into voltage information through the electrodes of EEG measurement channel 1 and superimposed on the EEG signal collected by the electrodes. The analog-to-digital converter 3 converts the collected voltage signal into a digital signal, which contains both the EEG signal and an impedance signal. The impedance measurement unit 4 is connected to the analog-to-digital converter 3. The impedance measurement unit 4 can receive the digital signal from the analog-to-digital converter 3 and separate the impedance signal from the digital signal. Based on this impedance signal, the EEG impedance value corresponding to that EEG measurement channel is calculated.

[0038] The signal frequency of constant current source 2 is a preset multiple of the sampling rate of analog-to-digital converter unit 3, so that the EEG signal and impedance signal can be converted together. Specifically, this preset multiple can be set to one-quarter. Taking a sampling rate of 500Hz for analog-to-digital converter unit 3 as an example, the signal frequency of constant current source 2 is 125Hz, and the amplitude is 6nA. It should be noted that the noise of constant current source 2 should be as low as possible to avoid having a significant impact on the EEG signal. The current signal of constant current source 2 flows in from the positive terminal, flows through the scalp and electrodes, and flows back to analog-to-digital converter unit 3 from the negative terminal.

[0039] The brain electrical impedance measurement system provided in this embodiment includes at least one EEG measurement channel, a constant current source, an analog-to-digital converter (ADC), and an impedance measurement unit. The electrodes of the EEG measurement channel are in contact with the scalp. The constant current source is connected to at least one EEG measurement channel to provide a current excitation signal. The ADC is connected to at least one EEG measurement channel. Since the frequencies of the EEG signal and the impedance signal are different, the signal frequency of the constant current source is set to a preset multiple of the sampling rate of the ADC. This allows for simultaneous conversion of the EEG signal and the impedance signal output from the EEG measurement channel. The two signals are then separated by frequency filtering, eliminating the need for separate data conversion, reducing circuit complexity, and saving costs. The impedance measurement unit is connected to the ADC, enabling real-time detection of brain electrical impedance based on the electrical signals from the EEG measurement channel. Thus, this brain electrical impedance measurement system combines circuit simplification with real-time brain electrical impedance detection.

[0040] This invention also provides a brain electrical impedance measurement system, such as... Figure 2As shown, the brain electrical impedance measurement system includes at least one EEG measurement channel 11, a constant current source 21, an analog-to-digital converter 31, and an impedance measurement unit 41. The impedance measurement unit 41 includes a frequency selection module 411 and an impedance calculation module 412.

[0041] Specifically, the frequency selection module 411 is connected to the output terminal of the analog-to-digital conversion unit 31, and the impedance calculation module 412 is connected to the output terminal of the frequency selection module 411. The frequency selection module 411 can be a frequency domain filter. Since the frequencies of the EEG signal and the impedance signal are different, and the frequency of the EEG signal is typically around 0.5–30 Hz, the EEG signal and the impedance signal can be separated by the frequency domain filter, thus avoiding separate conversion between the EEG signal and the impedance signal, thereby reducing circuit complexity and saving costs.

[0042] The impedance signal is separated from the digital signal by the frequency selection module 411 and sent to the impedance calculation module 412. The impedance calculation module 412 can calculate the corresponding impedance value based on the impedance signal.

[0043] The EEG measurement channel 11, constant current source 21, analog-to-digital conversion unit 31, frequency selection module 411, and impedance calculation module 412 constitute the EEG impedance measurement circuit. The voltage and impedance relationship of this measurement circuit can be expressed as: V = 2 × I1 × (Rp + Z1), where V is the peak-to-peak voltage of the measurement circuit, I1 is the current amplitude of the constant current source, Rp is the equivalent series resistance in the measurement circuit, and Z1 is the contact impedance of the scalp-electrode. Based on the peak-to-peak voltage V, the current amplitude I1 of the constant current source, and the equivalent series resistance Rp, the scalp-electrode contact impedance Z1 can be determined through measurement.

[0044] The brain electrical impedance measurement system provided in this embodiment includes an impedance measurement unit comprising a frequency selection module and an impedance calculation module. The frequency selection module is connected to the output of the analog-to-digital converter and is used to separate the EEG signal and impedance signal from the EEG measurement signal. The impedance calculation module is connected to the output of the frequency selection module and is used to calculate the impedance value corresponding to the EEG signal. Since the EEG signal and impedance signal have different frequencies, separating them via the frequency selection module eliminates the need for separate conversion between the EEG and impedance signals, thereby reducing circuit complexity.

[0045] This invention also provides a brain electrical impedance measurement system, such as... Figure 3As shown, the brain electrical impedance measurement system includes at least one EEG measurement channel 12, a constant current source 22, an analog-to-digital converter 32, an impedance measurement 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 at least one EEG measurement channel 12 via at least one calibration branch 62. When the electrodes are detached, the calibration unit 52 can determine the calibration coefficient of at least one EEG measurement channel 12 based on the electrical signal from at least one calibration branch 62.

[0046] Specifically, the brain impedance calibration method is the same for each EEG measurement channel. Here, the brain impedance measurement of one of the EEG measurement channels is described in detail. During the brain impedance calibration process, the calibration unit 52 can control the calibration branch 62 connected to the EEG measurement channel 12 and calculate the calibration coefficient after the calibration branch 62. The impedance measurement unit 42 can then correct the brain impedance based on the calibration coefficient.

[0047] Before performing brain electrical impedance tomography (BEE) measurements, the electrodes are first checked for detachment. If detachment is detected, the BEE is corrected. A constant current source 22 provides a current excitation signal to the BEE measurement channel, injecting an alternating current signal into it. A positive-phase current source and a negative-phase current source are applied to both ends of the BEE measurement channel 12. A calibration branch 62 simulates the contact impedance between the electrodes of the BEE measurement channel 12 and the scalp. Current flows in reverse through the BEE measurement channel 12 and the calibration branch 62 connected to it into the analog-to-digital converter (ADC) unit 32. The ADC unit 32 converts the simulated voltage signal into a digital signal. An impedance measurement unit 42 is connected to the ADC unit 32. The impedance measurement unit 42 receives the digital signal from the ADC unit 32 and calculates the calibrated BEE value after connecting to the calibration branch 62 based on this digital signal.

[0048] The calibration unit 52 may include a controller 521 and a processor 522. When calibrating brain impedance, the controller 521 can control the calibration branch 62 connected to the EEG measurement channel 12. The processor 522 calculates the calibration coefficient of the brain impedance after the EEG measurement channel 12 is connected to the calibration branch 62 and saves the calibration coefficient. Then, during the real-time detection of brain impedance, the impedance measurement unit 42 can correct the brain impedance value according to the calibration coefficient.

[0049] The brain electrical impedance measurement system provided in this embodiment further includes a calibration unit connected to the impedance measurement unit. This calibration unit is connected to at least one EEG measurement channel via at least one calibration branch, and is used to determine the calibration coefficient of at least one EEG measurement channel based on the electrical signal of the at least one calibration branch. The impedance value calculated by the impedance measurement unit is corrected using this calibration coefficient, thereby improving the measurement accuracy of the impedance value.

[0050] Optionally, such as Figure 4 As shown, the calibration branch 62 may include at least one set of calibration resistors 621 and a switching switch 622. The two ends of the at least one set of calibration resistors 621 are respectively connected to the EEG measurement channel 12; the switching switch is connected to the calibration unit 52, and the calibration unit 52 can control the action of the switching switch 622 to control the conduction state of the corresponding calibration branch 62.

[0051] Specifically, the calibration resistor 621 can be a fixed resistor. A set of calibration resistors 621 can include two sets of precision fixed resistors R1 and R2, used to simulate the contact impedances Z1 and Z2 between the electrode and the scalp, and also to limit current. It should be noted that Z1 and Z2 are in a disengaged state during calibration. The switch can be an analog switch or other control switches; no specific limitation is made here.

[0052] The controller 521 of the calibration unit 52 can control the switching switch 622 on the R1 circuit to close and the switching switch 622 on the R2 circuit to open, so that the constant current source 22 flows through R1. At this time, the relationship between the R1 circuit and the voltage V1 can be obtained as: V1=2×a×I1×(Rp+R1+b); The controller 521 of the calibration unit 52 can control the switching switch 622 on the R1 circuit to open and the switching switch 622 on the R2 circuit to close, so that the constant current source 22 flows through R2. At this time, the relationship between the R2 circuit and the voltage V2 can be obtained as: V2=2×a×I1×(Rp+R2+b); Combining the above two relationships, the calibration coefficients a and b can be obtained, and the calculated calibration coefficients a and b can be saved to the processor of the calibration unit 52.

[0053] Optionally, such as Figure 5 As shown, the switch 622 can also be connected to the controller 521 of the calibration unit 52 via an external control unit 624. The external control unit 624 can be externally connected to the brain impedance measurement system as an independent tooling for calibration. The calibration resistor 621 can be connected to the EEG measurement channel to measure brain impedance. After the external control unit 624 establishes a communication connection with the controller 521 of the calibration unit 52 through a digital communication interface, the controller 521 can indirectly control the switch 622 to switch between the R1 and R2 circuits.

[0054] The calculation process of the calibration coefficients can include the following steps: The controller 521 and the external control unit 624 establish a communication connection, and the external control unit 624 controls the switch 622; the external control unit 624 controls the switch 622 on the R1 circuit to close and the switch 622 on the R2 circuit to open, and the constant current source 22 flows through the R1 circuit. At this time, the relationship between the R1 circuit and the voltage V1 can be obtained as: V1 = 2 × a × I1 × (Rp + R1 + b); the external control unit 624 controls the switch 622 on the R1 circuit to open and the switch 622 on the R2 circuit to close, and the constant current source 22 flows through the R2 circuit. At this time, the relationship between the R2 circuit and the voltage V2 can be obtained as: V2 = 2 × a × I1 × (Rp + R2 + b); combining the above two relationships, the calibration coefficients a and b can be obtained and saved to the processor of the calibration unit 52. After calibration, the connection between the calibration unit 52 and the EEG measurement channel is disconnected to perform real-time detection of brain impedance.

[0055] The brain electrical impedance measurement system provided in this invention includes a calibration branch comprising at least one set of calibration resistors and a switching switch. Each calibration branch has its two ends connected to a corresponding EEG measurement channel. The switching switch is connected to a calibration unit, which controls the operation of the switching switch to control the conduction state of the corresponding calibration branch. By determining the calibration coefficient of the EEG measurement channel using the calibration resistors and the switching switch to correct the impedance value calculated by the impedance measurement unit, the complexity of the impedance detection circuit is simplified, the influence of the calibration circuit on the EEG measurement channel is avoided, and the measurement accuracy of the impedance value is improved.

[0056] Optionally, such as Figure 6 As shown, 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 set of calibration resistors 621. The first protection circuit 623 is used to prevent high-frequency interference from electrosurgical equipment, defibrillators, etc., and to protect the devices in the calibration branch 62, namely the switch 622 and the calibration resistors 621, to prevent overvoltage damage.

[0057] The brain electrical impedance measurement system provided in this embodiment further includes a first protection circuit in its calibration branch. One end of the first protection circuit is connected to a switch, and the other end is connected to at least one set of calibration resistors. The first protection circuit protects the devices in the calibration branch from overvoltage damage and also prevents external high-frequency interference to the calibration branch.

[0058] This invention provides a brain electrical impedance measurement system, such as... Figure 7As shown, the brain electrical impedance measurement system includes at least one EEG measurement channel 13, a constant current source 23, an analog-to-digital converter (ADC) unit 33, a frequency selection module 43, an impedance calculation module 53, a second protection circuit 63, a filter circuit 73, a calibration branch 83, and a calibration unit 93. The electrodes of at least one EEG measurement channel 13 are in contact with the scalp. The constant current source 23 is connected to at least one EEG measurement channel 13 and provides a current excitation signal to it. The ADC unit 33 is connected to at least one EEG measurement channel 13, and the signal frequency of the constant current source 23 is a preset multiple of the sampling rate of the ADC unit 33. The frequency selection module 43 is connected to the output of the ADC unit 33 and separates the impedance signal from the digital signal output by the ADC unit 33. The impedance calculation module 53 is connected to the output of the frequency selection module 43 and calculates the brain electrical impedance based on the impedance signal output by the frequency selection module 43. The second protection circuit 63 is connected to at least one EEG measurement channel 13, and the second protection circuit 63 is disposed before the constant current source 23 to protect the circuit unit disposed thereafter; the filter circuit 73 is connected to at least one EEG measurement channel 13, and the filter circuit 73 is disposed between the second protection circuit 63 and the constant current source 23 to filter out high-frequency interference.

[0059] Specifically, the second protection circuit 63 only includes devices such as a neon tube and a clamping diode, and the filter circuit 73 is a low-pass filter circuit. The protection resistor of the second protection circuit 63 can be equivalently represented in the equivalent series resistance Rp of the filter circuit 73. During the EEG impedance measurement, the constant current source 23 provides a current excitation signal to the EEG measurement channel, injecting an AC current signal into the channel. A positive-phase current source and a negative-phase current source are added to both ends of the EEG measurement channel. The current passes through the equivalent series resistance Rp of the filter circuit 73, the second protection circuit 63, and the electrodes of the EEG measurement channel 13, converting the current into voltage information, which is then superimposed on the EEG signal acquired by the electrodes. The analog-to-digital converter 33 converts the acquired voltage signal into a digital signal, which contains both the EEG signal and the impedance signal. The frequency selection module 43 is connected to the analog-to-digital converter 33, receives the digital signal from the converter, and separates the impedance signal from the digital signal. The impedance calculation module can then calculate the EEG impedance value corresponding to the EEG measurement channel based on the impedance signal.

[0060] The signal frequency of the constant current source 23 is a preset multiple of the sampling rate of the analog-to-digital converter 33, so that the EEG signal and impedance signal can be converted together. The current signal of the constant current source 23 flows in from the positive terminal, through the scalp and electrodes, and flows back to the analog-to-digital converter 33 from the inverting terminal.

[0061] During the brain electrical impedance calibration process, the contact impedance between the electrodes of the EEG measurement channel and the scalp is simulated through calibration branch 83, and the brain electrical impedance calibration coefficient during the EEG measurement process is calculated by calibration unit 93. During the EEG measurement process, the impedance calculation unit can obtain the calibration coefficient calculated by calibration unit 93 and correct the impedance value of the EEG signal according to the calibration coefficient to ensure the measurement accuracy of brain electrical impedance.

[0062] The brain electrical impedance measurement system provided in this embodiment further includes a second protection circuit and a filtering circuit. The second protection circuit is connected to at least one EEG measurement channel and is positioned before the constant current source to protect the subsequent circuit units. The filtering circuit is connected to at least one EEG measurement channel and is positioned between the second protection circuit and the constant current source to filter out high-frequency interference. The second protection circuit and the filtering circuit ensure the normal operation of the brain electrical impedance measurement system, thereby guaranteeing accurate measurement of brain electrical impedance.

[0063] According to an embodiment of the present invention, an embodiment of a method for measuring brain electrical impedance is provided. It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions. Furthermore, although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0064] This embodiment provides a method for measuring brain electrical impedance, which can be used in the aforementioned brain electrical impedance measurement system, such as a brain electrical impedance measurement system for medical devices. Figure 8 This is a flowchart of a method for measuring brain electrical impedance according to an embodiment of the present invention, such as... Figure 8 As shown, the process includes the following steps:

[0065] S11, a constant current source injects a current excitation signal into at least one EEG measurement channel so that the impedance signal and the EEG signal are superimposed to form an EEG measurement signal.

[0066] In a brain electrical impedance measurement system, at least one brain electrical impedance measurement channel contacts the scalp via an electrode, and at least one brain electrical measurement channel can form a lead system. Each brain electrical measurement channel in the lead system can include a measurement lead and a drive lead. One end of the lead wire contacts the scalp via an electrode, inducing brain electrical signals and simultaneously generating contact impedance between the electrode and the scalp, forming an impedance signal.

[0067] A constant current source provides a current excitation signal to at least one EEG measurement channel, injects an alternating current signal into the EEG measurement channel, so that the impedance signal and the EEG signal collected by the electrodes are superimposed to form an EEG measurement signal, and the collected EEG measurement signal is sent to the analog-to-digital conversion unit.

[0068] S12, the analog-to-digital conversion unit is used to convert the EEG 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.

[0069] The constant current source's signal frequency is a preset multiple of the analog-to-digital converter's sampling rate, enabling the converter to simultaneously convert the EEG signal and impedance signal contained in the EEG measurement signal into digital signals without separate conversion. The converter then sends the converted digital EEG measurement signal to the impedance measurement unit.

[0070] S13, the impedance measurement unit is used to calculate the impedance value corresponding to the EEG measurement signal based on the digital signal.

[0071] The impedance measurement unit of the brain electrical impedance measurement system can receive the digital signal sent by the analog-to-digital conversion unit, separate the EEG signal and impedance signal contained in the digital signal, and calculate the impedance value corresponding to the separated impedance signal. This impedance value is the impedance value corresponding to the EEG measurement signal.

[0072] The brain impedance measurement method provided in this embodiment, in the process of converting the EEG measurement signal into a digital signal, by setting the signal frequency of the constant current source to a preset multiple of the sampling rate of the analog-to-digital conversion unit, can simultaneously convert the EEG signal and impedance signal output from the EEG measurement channel. Then, the two are separated by frequency filtering, eliminating the need for separate data conversion, thus improving the data processing speed. Based on the digital signal corresponding to the EEG measurement signal, the impedance value of the EEG measurement signal is calculated in real time, thereby realizing real-time detection of brain impedance.

[0073] This embodiment provides a method for measuring brain electrical impedance, which can be used in the aforementioned brain electrical impedance measurement system, such as a brain electrical impedance measurement system for medical devices. Figure 9 This is a flowchart of a method for measuring brain electrical impedance according to an embodiment of the present invention, such as... Figure 9 As shown, the process includes the following steps:

[0074] S21, a constant current source injects a current excitation signal into at least one EEG measurement channel, so that the impedance signal and the EEG signal are superimposed to form an EEG measurement signal. For detailed explanation, please refer to the relevant description of step S11 in the above embodiment, which will not be repeated here.

[0075] S22, the analog-to-digital conversion unit is used to convert the EEG 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 detailed explanation, please refer to the relevant description of step S12 in the above embodiment, which will not be repeated here.

[0076] S23, the impedance measurement unit is used to calculate the impedance value corresponding to the EEG measurement signal based on the digital signal.

[0077] Specifically, step S23 above may include the following steps:

[0078] S231, obtain the calibration coefficient.

[0079] The calibration coefficient is a factor used to correct for brain impedance, facilitating accurate real-time detection of brain impedance during EEG measurements. The calibration coefficient can be calculated by the processor of the calibration unit, and the impedance measurement unit of the brain impedance measurement system can receive the calibration coefficient calculated by the calibration unit.

[0080] Specifically, step S231 above may include the following steps:

[0081] (1) Send a control command to the switching switch to control the conduction of at least one calibration branch.

[0082] Before impedance calibration begins, the impedance of each EEG measurement channel is measured, requiring the electrodes to be in a detached state from the scalp. By controlling the switching on or off of a switch, the calibration branch connected to the EEG measurement channel is controlled, and the relationship between the impedance and voltage of the current circuit is determined based on the connected calibration branch.

[0083] (2) Receive electrical signals output from at least one EEG measurement channel after at least one calibration branch is activated.

[0084] The electrical signal is the signal relationship between the loop voltage and loop impedance of the EEG measurement channel. Connecting different calibration branches can yield different signal relationships between the loop voltage and loop impedance. The calibration unit of the EEG impedance measurement system can receive the electrical signals output from the EEG measurement channel after different calibration branches are activated.

[0085] (3) Determine the calibration coefficient based on the electrical signal output from at least one EEG measurement channel.

[0086] By combining the signal relationships of different groups, the calibration coefficients in the signal relationships can be calculated and saved to the calibration unit of the brain electrical impedance measurement system. This allows the brain electrical impedance measurement system to perform brain electrical impedance correction during real-time brain electrical impedance detection, thereby enabling accurate detection of brain electrical impedance.

[0087] S232, based on the calibration coefficient and impedance signal, determines the impedance value corresponding to the EEG measurement signal.

[0088] The impedance signal is separated from the digital signal corresponding to the EEG measurement signal. The EEG impedance measurement system can determine the impedance value in the EEG 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 EEG measurement signal.

[0089] The brain impedance measurement method provided in this embodiment improves the measurement accuracy of the brain signal impedance value by obtaining the calibration coefficient of at least one brain measurement channel and correcting the impedance value corresponding to the brain signal based on the calibration coefficient.

[0090] This invention also provides a brain electrical impedance measurement device; please refer to [link to relevant documentation]. Figure 10 , Figure 10 This is a schematic diagram of the structure of a brain electrical impedance measurement device provided in an optional embodiment of the present invention, as shown below. Figure 10 As shown, the brain electrical impedance measurement device may include: at least one processor 401, such as a CPU (Central Processing Unit), at least one communication interface 403, a memory 404, and at least one communication bus 402. The communication bus 402 is used to establish communication between these components. The communication interface 403 may include a display screen or a keyboard; optionally, the communication interface 403 may also include a standard wired interface or a wireless interface. The memory 404 may be high-speed RAM (Random Access Memory) or non-volatile memory, such as at least one disk storage device. Optionally, the memory 404 may also be at least one storage device located remotely from the aforementioned processor 401. The processor 401 may be combined with... Figures 1 to 7 The system described herein stores an application program in memory 404, and processor 401 calls the program code stored in memory 404 to perform any of the above method steps.

[0091] The communication bus 402 can be a peripheral component interconnect (PCI) bus or an extended industry standard architecture (EISA) bus, etc. The communication bus 402 can be divided into an address bus, a data bus, and a control bus, etc. For ease of representation, Figure 10 The bus is represented by a single thick line, but this does not mean that there is only one bus or one type of bus.

[0092] The memory 404 may include volatile memory, such as random-access memory (RAM); the memory may also include non-volatile memory, such as flash memory, hard disk drive (HDD) or solid-state drive (SSD); the memory 404 may also include a combination of the above types of memory.

[0093] The processor 401 can be a central processing unit (CPU), a network processor (NP), or a combination of CPU and NP.

[0094] The processor 401 may further include a hardware chip. This 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 generic array logic (GAL), or any combination thereof.

[0095] Optionally, memory 404 is also used to store program instructions. Processor 401 can call the program instructions to implement the functions described in this application. Figure 8 and Figure 9 The brain electrical impedance measurement method shown in the embodiment.

[0096] This invention also provides a non-transitory computer storage medium storing computer-executable instructions that can execute the processing method of the brain electrical impedance measurement method in any of the above method embodiments. The storage medium can be a magnetic disk, optical disk, read-only memory (ROM), random access memory (RAM), flash memory, hard disk drive (HDD), or solid-state drive (SSD), etc.; the storage medium may also include combinations of the above types of memory.

[0097] Although embodiments of the 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 all fall within the scope defined by the appended claims.

Claims

1. A brain electrical impedance measurement system, characterized in that, include: At least one electroencephalogram (EEG) measurement channel, wherein the electrodes of the EEG measurement channel are used to contact the scalp; A constant current source is connected to each of the at least one EEG measurement channels, and the constant current source is used to provide a current excitation signal to the at least one EEG measurement channel. An analog-to-digital conversion unit is connected to at least one EEG 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. An impedance measurement unit, connected to the analog-to-digital conversion unit, is used to calculate brain electrical impedance based on the electrical signals from the EEG measurement channel; A calibration unit is connected to the impedance measurement unit. The calibration unit is connected to the at least one EEG measurement channel through at least one calibration branch. It is used to determine the calibration coefficient of the at least one EEG measurement channel based on the electrical signal of the at least one calibration branch when the electrode is in a detached state. The impedance measurement unit includes: a frequency selection module connected to the output of the analog-to-digital conversion unit, used to separate the EEG signal and impedance signal from the EEG measurement signal; and an impedance calculation module connected to the output of the frequency selection module, used to calculate the impedance value corresponding to the impedance signal. The EEG measurement channel, the constant current source, the analog-to-digital converter, the frequency selection module, and the impedance calculation module constitute the measurement circuit for brain electrical impedance.

2. The system according to claim 1, characterized in that, Also includes: The at least one calibration branch is connected to the calibration unit.

3. The system according to claim 1 or 2, characterized in that, The calibration branch includes: At least one set of calibration resistors, with both ends of each set of calibration resistors connected to the corresponding EEG measurement channel; A switching switch is connected to the calibration unit, which controls the operation of the switching switch to control the conduction state of the corresponding calibration branch.

4. The system according to claim 3, characterized in that, The calibration branch also includes: The first protection circuit has one end connected to the switching switch and the other end connected to the at least one set of calibration resistors.

5. The system according to claim 1, characterized in that, Also includes: A second protection circuit is connected to the at least one EEG measurement channel and is positioned before the constant current source. The second protection circuit is used to protect the circuit unit positioned thereafter. A filtering circuit, connected to at least one EEG measurement channel, is disposed between the second protection circuit and the constant current source. The filtering circuit is used to filter out high-frequency interference.

6. A method for measuring brain electrical impedance based on the brain electrical impedance measurement system according to any one of claims 1-5, characterized in that, Includes the following steps: A constant current source injects a current excitation signal into at least one EEG measurement channel so that the impedance signal and the EEG signal are superimposed to form an EEG measurement signal; The analog-to-digital converter is used to convert the electroencephalogram (EEG) 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 converter; The impedance measurement unit is used to calculate the impedance value corresponding to the EEG measurement signal based on the digital signal.

7. The method according to claim 6, characterized in that, The step of calculating the impedance value corresponding to the electroencephalogram (EEG) measurement signal based on the digital signal includes: Obtain the calibration coefficients; Based on the calibration coefficient and the impedance signal, the impedance value corresponding to the EEG measurement signal is determined, wherein the impedance signal is separated from the digital signal.

8. The method according to claim 7, characterized in that, The acquisition of calibration coefficients includes: Send a control command to the switching switch to control the conduction of at least one calibration branch; Receive electrical signals output from at least one EEG measurement channel after the at least one calibration branch is activated; The calibration coefficient is determined based on the electrical signal output from the at least one EEG measurement channel.

9. A brain electrical impedance measurement device, characterized in that, include: A memory and a processor are communicatively connected, the memory storing computer instructions, and the processor executing the computer instructions to perform the brain electrical impedance measurement method according to any one of claims 6-8.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer instructions for causing the computer to perform the brain electrical impedance measurement method according to any one of claims 6-8.

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