Electrical impedance imaging system based on digital active electrode

Abstract

The invention provides an electrical impedance tomography system based on a digital active electrode. The electrical impedance tomography system can be applied to the technical field of electrical impedance tomography. The system comprises a plurality of active electrode modules which are cascaded and connected end to end, and each active electrode module comprises an electrode arranged on the surface of a to-be-detected object; the controller is used for configuring the active electrode module into an excitation mode or an acquisition mode; the current generation unit is used for providing an excitation current signal for the electrode when the working mode is the excitation mode; the voltage acquisition unit is used for acquiring a digital voltage signal which is obtained by responding to an excitation current signal provided by the first active electrode module under the action of a to-be-detected object when the working mode is an acquisition mode; the demodulation unit is used for demodulating the digital voltage signal to obtain voltage information corresponding to the active electrode module; and the main control module is used for generating a conductivity distribution image corresponding to the to-be-detected object according to the received voltage information corresponding to the plurality of active electrode modules.

Description

Technical Field

[0001] This disclosure relates to the field of electrical impedance tomography, and more specifically, to an electrical impedance tomography system based on a digital active electrode. Background Technology

[0002] Electrical Impedance Tomography (EIT) technology is characterized by being radiation-free, having a small device size, and enabling continuous imaging, making it widely used in clinical scenarios such as continuous monitoring. EIT can utilize the different electrical properties of different tissues and organs in the human body. By uniformly arranging a set of electrode arrays on the surface of the object under test, and then injecting excitation current into different electrode pairs in sequence according to a certain excitation pattern, and collecting the response electrical signals on the remaining electrode pairs, the impedance distribution image of the object under test can be obtained using a reconstruction algorithm.

[0003] In realizing the present invention, the inventors discovered that there is a highly nonlinear relationship between the electrical signals and conductivity acquired by EIT, and that the reconstruction is susceptible to noise interference. This results in low spatial resolution of the reconstructed impedance distribution image, making it difficult to extract clear tissue structure information. Summary of the Invention

[0004] In view of this, the present disclosure provides an electrical impedance imaging system based on digital active electrodes.

[0005] One aspect of this disclosure provides a digital active electrode-based electrical impedance imaging system, comprising: multiple active electrode modules, wherein the multiple active electrode modules are cascaded and connected end-to-end, the multiple active electrode modules including a first active electrode module operating in excitation mode and a second active electrode module operating in acquisition mode, each active electrode module including: electrodes disposed on the surface of the object under test; a controller for configuring the active electrode module to excitation mode or acquisition mode; a current generation unit for providing an excitation current signal to the electrodes when operating in excitation mode; a voltage acquisition unit for acquiring a digital voltage signal generated by the object under test in response to the excitation current signal provided by the first active electrode module when operating in acquisition mode; a demodulation unit for demodulating the digital voltage signal to obtain voltage information corresponding to the active electrode module; and a main control module connected to each of the multiple active electrode modules for generating an impedance distribution image corresponding to the object under test based on the received voltage information corresponding to each of the multiple active electrode modules.

[0006] According to an embodiment of this disclosure, the current generation unit includes: a digital-to-analog converter for generating an excitation voltage signal when the operating mode is excitation mode; and a voltage-controlled current source for converting the excitation voltage signal into an excitation current signal and providing the excitation current signal to the electrodes when the operating mode is excitation mode.

[0007] According to embodiments of this disclosure, the excitation modes include an outflow excitation mode and an absorption excitation mode. The first active electrode module includes an outflow electrode module operating in the outflow excitation mode and an absorption electrode module operating in the absorption excitation mode. The voltage-controlled current source includes: a current source subunit, used to convert the excitation voltage signal into an excitation current signal and provide the excitation current signal to the electrode when the operating mode is the outflow excitation mode; and a current collector subunit, used to provide a target return path for the excitation current signal to absorb the excitation current signal, wherein the target return path is the path formed by the electrode of the absorption electrode module and the current collector subunit of the outflow electrode module.

[0008] According to embodiments of this disclosure, each of the multiple active electrode modules further includes a first multiplexer and a second multiplexer. For the nth active electrode module: the first terminal of the first multiplexer and the first terminal of the second multiplexer are both connected to the electrode; the second terminal of the second multiplexer is connected to the second terminal of the first multiplexer in the (n+1)th active electrode module; the third terminal of the second multiplexer is connected to the (n-1)th active electrode module; the third terminal of the first multiplexer is connected to the current source subunit; and the fourth terminal of the first multiplexer is connected to the current collector subunit. The (n+1)th active electrode module is a next-level active electrode module cascaded with the nth active electrode module, and the (n-1)th active electrode module is a previous-level active electrode module cascaded with the nth active electrode module. 1 < n < N, where N is the total number of active electrode modules, and n and N are both positive integers. The controller is further configured to set the active electrode module to an excitation mode or a acquisition mode by controlling the selection states of the first multiplexer and the second multiplexer.

[0009] According to an embodiment of this disclosure, when the outflow electrode module and the absorption electrode module are adjacent, the first multiplexer of the outflow electrode module is closed and the second multiplexer selects the second terminal, while the first multiplexer of each active electrode module other than the outflow electrode module is open and the second multiplexer selects the first terminal.

[0010] According to embodiments of this disclosure, when the outflow electrode module and the absorption electrode module are not adjacent, the first multiplexer of the outflow electrode module is closed and the second multiplexer is enabled at its second terminal; the first multiplexer of the active electrode module between the outflow electrode module and the absorption electrode module is open and the second multiplexer is enabled at its second terminal; and the first multiplexer of each active electrode module other than the outflow electrode module, the absorption electrode module and the active electrode module between the outflow electrode module is open and the second multiplexer is enabled at its first terminal.

[0011] According to an embodiment of this disclosure, the current generation unit further includes: the current generation unit further includes a sampling resistor, and the current source subunit is connected to the first terminal of the first multiplexer via the sampling resistor; the controller is further configured to adjust the amplitude of the excitation voltage signal output by the digital-to-analog converter according to the ratio between the voltage across the sampling resistor and the resistance value of the sampling resistor, so that the ratio satisfies the preset excitation current.

[0012] According to embodiments of this disclosure, the controller is further configured to sequentially configure the operating modes of every two adjacent active electrode modules (excluding the first active electrode module) as acquisition modes.

[0013] According to an embodiment of this disclosure, the voltage acquisition unit includes: a preprocessing subunit, configured to preprocess the received first initial voltage signal and second initial voltage signal respectively to obtain a first intermediate voltage signal and a second intermediate voltage signal; and an analog-to-digital converter, configured to convert the difference between the first intermediate voltage signal and the second intermediate voltage signal into a digital voltage signal; wherein the first initial voltage signal is a voltage signal generated by the current second active electrode module in response to the excitation current signal, and the second initial voltage signal is a voltage signal generated by the next active electrode module cascaded with the current second active electrode module in response to the excitation current signal.

[0014] According to embodiments of this disclosure, the voltage information includes the real part and imaginary part of a digital voltage signal; the demodulation unit is further configured to send the real part and imaginary part to the controller; the controller is further configured to send the real part and imaginary part to the main control module via a data line.

[0015] According to embodiments of this disclosure, by integrating a demodulation unit and a controller within the active electrode module, the controller configures the operating mode of the active electrode module, and the demodulation unit demodulates the digital voltage signal obtained by the excitation current signal acting on the object under test within the active electrode module to obtain the voltage information of the active electrode module. This allows the main control module to transmit only digital signals to each active electrode module, thereby reducing the number of data lines between the main control module and each active electrode module. This avoids unnecessary noise introduced by parasitic parameters and spatial electromagnetic interference caused by excessive data lines, while reducing the communication bandwidth requirements between the main control module and each active electrode module, improving the system signal-to-noise ratio, and enabling flexible adjustment of the number of active electrode modules. Furthermore, multiple active electrode modules cascaded and connected end-to-end can simultaneously receive instructions from the main control module to switch operating modes and perform voltage demodulation, which is beneficial for achieving impedance distribution images with higher spatial resolution and accuracy. Attached Figure Description

[0016] The above and other objects, features and advantages of this disclosure will become clearer from the following description of embodiments with reference to the accompanying drawings, in which:

[0017] Figure 1 A schematic block diagram of a digital active electrode-based electrical impedance imaging system according to an embodiment of the present disclosure is shown.

[0018] Figure 2 A schematic diagram of the internal structure of an active electrode module according to an embodiment of the present disclosure is shown.

[0019] Figure 3 The flowchart illustrating a measurement of a test object using a digital active electrode-based electrical impedance imaging system according to an embodiment of the present disclosure is shown.

[0020] Figure 4a The diagram illustrates the gated state of a multiplexer in a digital active electrode-based electrical impedance imaging system according to an embodiment of the present disclosure under adjacent excitation.

[0021] Figure 4b The diagram illustrates the gated state of a multiplexer in a digital active electrode-based electrical impedance imaging system according to an embodiment of the present disclosure under non-adjacent excitation. Detailed Implementation

[0022] The embodiments of the present disclosure will now be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the disclosure. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the present disclosure for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of the present disclosure.

[0023] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0024] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0025] When using expressions such as "at least one of A, B and C", they should generally be interpreted in accordance with the meaning that is commonly understood by those skilled in the art (e.g., "a system having at least one of A, B and C" should include, but is not limited to, a system having A alone, a system having B alone, a system having C alone, a system having A and B, a system having A and C, a system having B and C, and / or a system having A, B and C, etc.).

[0026] EIT hardware systems can be categorized into two architectures based on electrode type: passive electrodes and active electrodes. Passive electrode architectures consist solely of purely conductive materials, without integrating any active devices. The captured bioelectrical signals must be transmitted to the impedance data acquisition system via long transmission lines. Parasitic parameters of the transmission lines and electromagnetic interference in the environment introduce additional noise, reducing image quality. Active electrode architectures, on the other hand, integrate active devices on the electrode side, such as impedance transformers and preamplifiers, for impedance transformation and signal amplification of bioelectrical signals. This enhances the anti-interference capability of bioelectrical signals during transmission and improves image quality.

[0027] In one embodiment of the related technology, the voltage acquisition of EIT adopts a numerical differential method, which is susceptible to common-mode interference from the object under test; and the voltage acquisition unit does not integrate a multi-level adjustable gain adjustment circuit, which can easily introduce additional noise and lead to a decrease in the system signal-to-noise ratio.

[0028] In another embodiment of the related technology, the analog-to-digital converter used in the EIT system needs to be both high-speed and high-precision to convert the acquired high-frequency electrode bioelectric signals into digital signals. However, the amount of data in the converted digital signals is large, requiring multiple wire bundles and high bandwidth for data transmission with the main control module.

[0029] In view of this, embodiments of the present disclosure provide a power impedance imaging system based on digital active electrodes, comprising: multiple active electrode modules, wherein the multiple active electrode modules are cascaded and connected end-to-end, the multiple active electrode modules including a first active electrode module operating in excitation mode and a second active electrode module operating in acquisition mode, each active electrode module including: electrodes disposed on the surface of the object under test; a controller for configuring the active electrode module to excitation mode or acquisition mode; a current generation unit for providing an excitation current signal to the electrodes when operating in excitation mode; a voltage acquisition unit for acquiring a digital voltage signal obtained by the object under test in response to the excitation current signal provided by the first active electrode module when operating in acquisition mode; a demodulation unit for demodulating the digital voltage signal to obtain voltage information corresponding to the active electrode module; and a main control module connected to each of the multiple active electrode modules for generating an impedance distribution image corresponding to the object under test based on the received voltage information corresponding to each of the multiple second active electrode modules.

[0030] Figure 1 A schematic block diagram of a digital active electrode-based electrical impedance imaging system according to an embodiment of the present disclosure is shown. It should be noted that... Figure 1 The examples shown are merely examples of system architectures that can be applied to the embodiments of this disclosure, in order to help those skilled in the art understand the technical content of this disclosure, but do not mean that the embodiments of this disclosure cannot be used in other devices, systems, environments or scenarios.

[0031] like Figure 1 As shown, the system includes multiple active electrode modules (such as active electrode modules 101 to 108 in the figure) and a main control module 120. The multiple active electrode modules are cascaded and connected end to end, that is, active electrode module 101 is connected to active electrode module 102, active electrode module 102 is also connected to active electrode module 103, active electrode module 103 is also connected to active electrode module 104, active electrode module 104 is also connected to active electrode module 105, active electrode module 105 is also connected to active electrode module 106, active electrode module 106 is also connected to active electrode module 107, active electrode module 107 is also connected to active electrode module 108, and active electrode module 108 is also connected to active electrode module 101.

[0032] Taking the active electrode module 101 as an example, each active electrode module includes an electrode 101_1, a controller 101_2, a current generation unit 101_3, a voltage acquisition unit 101_4, and a demodulation unit 101_5. The electrode 101_1 can be a flexible electrode body. In addition, a metal ring opening structure or an interface directly connected to the flexible electrode can be reserved at the position corresponding to the electrode 101_1 for connecting the flexible electrode body. The metal ring opening structure can be connected to the flexible electrode female buckle by riveting. The electrode 101_1 is arranged on the surface of the object to be measured.

[0033] The controller 101_2 is used to configure the active electrode module 101 to either excitation mode or acquisition mode. When the active electrode module 101 is in excitation mode, it functions as the first active electrode module, using the current generation unit 101_3 to provide an excitation current signal to the electrode 101_1. Since the internal tissues of the test object have different impedance characteristics, the excitation current signal does not pass uniformly through all tissues of the test object, but flows to tissues with lower impedance. When the active electrode module 101 is in acquisition mode, it functions as the second active electrode module, using the voltage acquisition unit 101_4 to acquire a digital voltage signal obtained by the test object in response to the excitation current signal provided by the first active electrode module. The digital voltage signal can reflect the impedance distribution of the internal tissues of the test object. The demodulation unit 101_5 is used to demodulate the digital voltage signal to obtain voltage information corresponding to the active electrode module. The voltage information quantifies the resistance and phase delay of different tissues within the test object to the excitation current signal, thus reflecting the electrical characteristics of different tissues. The voltage information includes the real and imaginary parts of the digital voltage signal.

[0034] The main control module 120 is used to generate an impedance distribution image of the object under test based on the voltage information corresponding to each of the multiple active electrode modules, thereby obtaining the state information of different tissues inside the object under test. The main control module 120 includes a synchronization clock unit, a serial communication unit, and an image reconstruction unit. The synchronization clock unit is used to generate a globally unified pulse signal or clock signal and send the pulse signal or clock signal to the electrode modules 101 to the active electrode modules 108 via the SYNC / CLK signal line to drive the active electrode modules 101 to 108 to operate synchronously. The serial communication unit is used for bidirectional data communication between the main control module 120 and the active electrode modules 101-108. Specifically, a half-duplex asynchronous serial protocol can be used, connecting the main control module 120 to the active electrode modules 101-108 via UART1TX / RX data lines to UART8TX / RX data lines respectively. In addition, the main control module 120 is also connected to the active electrode modules 101-108 via the RST signal line for global reset. A power supply line (VCC) and a ground line (GND) are also included between the main control module 120 and the active electrode modules 101-108. The image reconstruction unit is used to reconstruct the impedance distribution image of the object under test based on the voltage information using an image reconstruction algorithm and upload it to the host computer 130.

[0035] It should be understood that Figure 1 The number of active electrode modules shown is merely illustrative. Depending on implementation requirements, any number of active electrode modules can be used, and the multiple units included in each active electrode module can be integrated onto the same chip or built onto multiple independent chips; this is not limited here.

[0036] According to embodiments of this disclosure, by integrating a demodulation unit and a controller within the active electrode module, the controller configures the operating mode of the active electrode module, and the demodulation unit demodulates the digital voltage signal obtained by the excitation current signal acting on the object under test within the active electrode module to obtain the voltage information of the active electrode module. This allows the main control module to transmit only digital signals to each active electrode module, thereby reducing the number of data lines between the main control module and each active electrode module. This avoids unnecessary noise introduced by parasitic parameters and spatial electromagnetic interference caused by excessive data lines, while reducing the communication bandwidth requirements between the main control module and each active electrode module, improving the system signal-to-noise ratio, and enabling flexible adjustment of the number of active electrode modules. Furthermore, multiple active electrode modules cascaded and connected end-to-end can simultaneously receive instructions from the main control module to switch operating modes and perform voltage demodulation, which is beneficial for achieving impedance distribution images with higher spatial resolution and accuracy.

[0037] According to an embodiment of this disclosure, the current generation unit includes: a digital-to-analog converter for generating an excitation voltage signal when the operating mode is excitation mode; and a voltage-controlled current source for converting the excitation voltage signal into an excitation current signal and providing the excitation current signal to the electrodes when the operating mode is excitation mode.

[0038] According to embodiments of this disclosure, the digital-to-analog converter in the current generation unit is connected to the controller. For the first active electrode module operating in excitation mode, the digital-to-analog converter generates an excitation voltage signal, which can be a sinusoidal voltage signal. The voltage-controlled current source is used to convert the excitation voltage signal into an excitation current signal and provide the excitation current signal to the electrode. The excitation current signal can be a sinusoidal current signal with constant amplitude, which can avoid exciting the nonlinear response of the tissue within the test object and facilitate subsequent demodulation.

[0039] According to embodiments of this disclosure, the excitation modes include an outflow excitation mode and an absorption excitation mode. The first active electrode module includes an outflow electrode module operating in the outflow excitation mode and an absorption electrode module operating in the absorption excitation mode. The voltage-controlled current source includes: a current source subunit, used to convert the excitation voltage signal into an excitation current signal and provide the excitation current signal to the electrode when the operating mode is the outflow excitation mode; and a current collector subunit, used to provide a target return path for the excitation current signal to absorb the excitation current signal, wherein the target return path is the path formed by the electrode of the absorption electrode module and the current collector subunit of the outflow electrode module.

[0040] According to embodiments of this disclosure, a current concentrator unit is used to provide a target return path for the excitation current signal. Based on this, a closed loop is realized whereby the current source subunit of the outgoing electrode module flows out of the electrode of the electrode module, the electrode of the test object absorbs the electrode of the electrode module, and the current concentrator unit of the outgoing electrode module flows out of the electrode module.

[0041] According to embodiments of this disclosure, the relative positional relationship between the absorption electrode module and the inflow electrode module can be determined according to different situations of the test object in actual needs. The absorption electrode module and the inflow electrode module can be adjacent or not adjacent.

[0042] According to embodiments of this disclosure, the current collection unit and the current source unit are integrated inside the active electrode module, so that the outflow electrode module operating in the outflow excitation mode, the tissue under test, and the absorption electrode module operating in the absorption excitation mode form a complete closed loop. This allows the active electrode module to be configured according to the controller to be configured with adjacent or non-adjacent first active electrode modules. Combined with the voltage acquisition of the second active electrode module, it provides image reconstruction data sources of different dimensions for the electrical impedance imaging of the object under test.

[0043] According to an embodiment of this disclosure, the voltage acquisition unit includes: a preprocessing subunit, configured to preprocess the received voltage signal generated by the current second active electrode module in response to the excitation current signal, i.e., the first initial voltage signal, and the voltage signal generated by the next active electrode module cascaded with the current second active electrode module in response to the excitation current signal, i.e., the second initial voltage signal, respectively, to obtain a first intermediate voltage signal and a second intermediate voltage signal; and an analog-to-digital converter, configured to convert the difference between the first intermediate voltage signal and the second intermediate voltage signal into the digital voltage signal.

[0044] The voltage acquisition unit is connected to the front end of the demodulation unit. The preprocessing subunit may include a buffer component, a gain amplification component, and a filtering component. The buffer component, the gain amplification component, and the filtering component may be arranged and combined in different orders, which is not limited here.

[0045] According to embodiments of this disclosure, the buffer component includes a buffer circuit for impedance matching, converting the acquired high-impedance first and second initial voltage signals into low-impedance voltage signals. This reduces the attenuation of the first and second initial voltage signals during transmission and their impact on subsequent processing, improving the accuracy of image reconstruction. The gain amplification component includes a programmable gain amplification circuit for dynamically amplifying the amplitudes of the impedance-matched first and second initial voltage signals, ensuring that the amplified signals match the demodulation unit and improving the system's signal-to-noise ratio and measurement accuracy. The filtering component may include a bandpass filter for filtering out interference noise from the amplified first and second initial voltage signals, providing a high signal-to-noise ratio data source for subsequent demodulation.

[0046] Therefore, it can be seen that the voltage acquisition unit of each second active electrode module performs differential signal acquisition, thus reducing common-mode interference.

[0047] According to embodiments of this disclosure, each of the multiple active electrode modules further includes a first multiplexer and a second multiplexer. For the nth active electrode module: the first terminal of the first multiplexer and the first terminal of the second multiplexer are both connected to the electrode; the second terminal of the second multiplexer is connected to the second terminal of the first multiplexer in the (n+1)th active electrode module; the third terminal of the second multiplexer is connected to the (n-1)th active electrode module; the third terminal of the first multiplexer is connected to the current source subunit; and the fourth terminal of the first multiplexer is connected to the current collector subunit. The (n+1)th active electrode module is a next-level active electrode module cascaded with the nth active electrode module, and the (n-1)th active electrode module is a previous-level active electrode module cascaded with the nth active electrode module. 1 < n < N, where N is the total number of active electrode modules, and n and N are both positive integers. The controller is further configured to set the active electrode module to an excitation mode or a acquisition mode by controlling the selection states of the first multiplexer and the second multiplexer.

[0048] According to an embodiment of this disclosure, the current generation unit further includes a sampling resistor, and the current source subunit is connected to the first terminal of the first multiplexer via the sampling resistor; the controller is further configured to adjust the amplitude of the excitation voltage signal output by the digital-to-analog converter according to the ratio between the voltage across the sampling resistor and the resistance value of the sampling resistor, so that the ratio satisfies the preset excitation current.

[0049] According to embodiments of this disclosure, before acquiring the first initial voltage signal and the second initial voltage signal, the amplitude of the excitation voltage signal output by the digital-to-analog converter can be adjusted by the controller so that the ratio between the voltage across the sampling resistor and the resistance of the sampling resistor satisfies the preset excitation current, thereby ensuring that the excitation current signal clock provided to the object under test maintains high accuracy and a certain degree of stability.

[0050] The active electrode module also includes a third multiplexer connected to the preprocessing subunit. This third multiplexer has two switchable input sources: a first input source (a first initial voltage signal and a second initial voltage signal) and a second input source (the voltage across a sampling resistor). The controller can switch the selection state of the third multiplexer to the second input source to acquire the voltage across the sampling resistor. Based on Ohm's law, the voltage across the sampling resistor and the resistance of the sampling resistor are equivalent to the current value of the excitation current signal. The controller can generate an adjustment command based on the deviation between the ratio and the preset excitation current, sending it to the digital-to-analog converter (DAC) to adjust the amplitude of the excitation voltage signal output by the DAC until the ratio meets the preset excitation current. The adjusted excitation voltage signal is then used to measure the object under test.

[0051] According to embodiments of this disclosure, before the measurement begins, the amplitude of the excitation voltage signal output by the digital-to-analog converter is adjusted by the controller so that the ratio between the voltage across the sampling resistor and the resistance of the sampling resistor satisfies the preset excitation current, thereby improving the accuracy and stability of the excitation current signal, solving the quality problem of the excitation current signal, and providing a certain data foundation for obtaining high-precision and high-reliability image reconstruction.

[0052] To better understand the internal circuit connections of the active electrode module in the embodiments of this disclosure, the following will be combined with... Figure 2 Provide an explanation.

[0053] Figure 2 A schematic diagram of the internal structure of an active electrode module according to an embodiment of the present disclosure is shown.

[0054] like Figure 2 As shown, the active electrode module includes electrodes, a voltage acquisition unit, a current generation unit, a controller, and a demodulation subunit. The current generation unit includes a voltage-controlled current source and a digital-to-analog converter (DAC). The voltage-controlled current source includes a sampling resistor R1, a current source subunit, a sampling resistor R2, and a current collector subunit. The sampling resistor R1 adjusts the amplitude of the excitation voltage signal output by the DAC, and the sampling resistor R2 maintains the symmetry of the circuit. The voltage acquisition unit includes a preprocessing subunit and an DAC. The demodulation unit uses a target digital algorithm to demodulate the digital voltage signal, obtaining the real and imaginary parts of the digital voltage signal with the same frequency as the excitation current signal. The target digital algorithm can be a Fast Fourier Transform or other algorithms that achieve the same purpose.

[0055] The second active electrode module can be any two active electrode modules in the system other than the first active electrode module. However, for a complete measurement cycle after the first active electrode module is determined, the two second active electrode modules configured each time are adjacent. The preprocessing process of the first and second initial voltage signals is performed in the preprocessing subunit, which will not be described in detail here.

[0056] According to the embodiments of this disclosure, to perform a complete round of measurement on the object under test, two adjacent active electrode modules can be selected sequentially as the second active electrode module to collect differential voltage, so as to achieve uniform voltage acquisition, avoid acquisition blind spots, improve the resolution of the reconstructed impedance distribution image, and at the same time, for different application scenarios, the measurement requirements can be met without changing the system structure.

[0057] The demodulation unit sends the demodulated real and imaginary data to the controller. The controller can package the amplitude and phase information and send it to the main control module via the UARTx TX / RX data line, thereby reconstructing the conductivity distribution image in the main control module.

[0058] To better understand the overall process of measuring the object under test using the digital active electrode-based electrical impedance imaging system according to embodiments of this disclosure, the following will be explained... Figure 3 Provide an explanation.

[0059] Figure 3 The flowchart illustrating a measurement of a test object using a digital active electrode-based electrical impedance imaging system according to an embodiment of the present disclosure is shown.

[0060] like Figure 3 As shown, this embodiment includes operations S301 to S308.

[0061] In operation S301, configure the first active electrode module.

[0062] The positions of the outflow electrode module and the absorption electrode module in the first active electrode module can be adjacent or not adjacent, which will not be elaborated here.

[0063] In operation S302, the third multiplexer in the outflow electrode module is selected to select the second input source in order to acquire the voltage across the sampling resistor.

[0064] In operation S303, the amplitude of the excitation voltage signal output by the digital-to-analog converter is adjusted according to the ratio between the voltage across the sampling resistor and the resistance value of the sampling resistor.

[0065] In operation S304, it is determined whether the ratio meets the preset excitation current. If the ratio meets the preset excitation current, operation S305 is executed; if the ratio does not meet the preset excitation current, the process returns to execution of operation S303.

[0066] In operation S305, the second active electrode module is configured, and the third multiplexer of the second active electrode module is selected to select the first input source to acquire the differential voltage of the first initial voltage signal and the second initial voltage signal.

[0067] In operation S306, determine whether the differential voltages of all second active electrode modules have been collected. If the differential voltages of all second active electrode modules have been collected, execute operation S307; if the differential voltages of all second active electrode modules have not been collected, return to execute operation S305.

[0068] In operation S307, the digital voltage signal obtained from the differential voltage is demodulated to obtain voltage information. This completes the measurement corresponding to a set of first active electrode modules. Then, operations S301 to S308 are repeated to reconfigure the first active electrode modules for measuring the object under test until each set of first active electrode modules has been traversed. Based on the voltage information obtained from each measurement, the impedance distribution image of the object under test can be reconstructed.

[0069] According to embodiments of this disclosure, the controller packages the amplitude and phase information obtained from demodulation and sends them to the main control module via data lines, reducing the number of data lines between the main control module and the active electrode module, thereby reducing excessive parasitic parameters of data lines and noise introduced by spatial electromagnetic interference.

[0070] The active electrode module also includes a first multiplexer S1, a second multiplexer S2, and a third multiplexer S3. The first terminal of the first multiplexer S1 and the first terminal of the second multiplexer S2 are both connected to the electrode. The second terminal of the second multiplexer S2 is connected to the second terminal of the first multiplexer S1 in the next cascaded active electrode module. The third terminal of the second multiplexer S2 is connected to the previous cascaded active electrode module. The third terminal of the first multiplexer S1 is connected to the current source subunit. The fourth terminal of the first multiplexer S1 is connected to the current collector subunit. Both output terminals of the third multiplexer S3 are connected to the preprocessing subunit. One set of the two input terminals of the third multiplexer S3 is located at both ends of the electrode, and the other set is located at both ends of the sampling resistor R1.

[0071] According to an embodiment of this disclosure, when the outflow electrode module and the absorption electrode module are adjacent, the first multiplexer of the outflow electrode module is closed and the second multiplexer selects the second terminal, while the first multiplexer of each active electrode module other than the outflow electrode module is open and the second multiplexer selects the first terminal.

[0072] According to embodiments of this disclosure, when the outflow electrode module and the absorption electrode module are not adjacent, the first multiplexer of the outflow electrode module is closed and the second multiplexer is enabled at its second terminal; the first multiplexer of the active electrode module between the outflow electrode module and the absorption electrode module is open and the second multiplexer is enabled at its second terminal; and the first multiplexer of each active electrode module other than the outflow electrode module, the absorption electrode module and the active electrode module between the outflow electrode module is open and the second multiplexer is enabled at its first terminal.

[0073] To better understand the selection states of multiple multiplexers for each of the multiple active electrode modules under different first active electrode module configurations, the following will be explained through... Figure 4a and Figure 4b To illustrate.

[0074] Figure 4a The diagram illustrates the gated state of a multiplexer in a digital active electrode-based electrical impedance imaging system according to an embodiment of the present disclosure under adjacent excitation.

[0075] like Figure 4a As shown, adjacent excitation means configuring the operating modes of two adjacent active electrode modules as excitation modes, so that... Figure 4a Taking the nth active electrode module as operating in outflow excitation mode and the (n+1)th active electrode module as operating in absorption excitation mode as an example, the first multiplexer S1 of the nth active electrode module is closed, the second multiplexer S2 selects the second terminal, and the third multiplexer S3 selects the first source. In addition, the first multiplexer S1 of the 1st to (n-1)th active electrode modules and the (n+1)th to Nth active electrode modules are open, the second multiplexer S2 selects the first terminal, and the third multiplexer S3 selects the first input source.

[0076] At this point, the current source subunit of the nth active electrode module, the electrode of the nth active electrode module, the object under test, the electrode of the (n+1)th active electrode module, and the current collection subunit of the nth active electrode module constitute a closed excitation current signal transmission path.

[0077] Figure 4b The diagram illustrates the gated state of a multiplexer in a digital active electrode-based electrical impedance imaging system according to an embodiment of the present disclosure under non-adjacent excitation.

[0078] like Figure 4b As shown, non-adjacent excitation means configuring the operating modes of two non-adjacent active electrode modules as excitation modes, so as to Figure 4b Taking the nth active electrode module as operating in outflow excitation mode and the (n+2)th active electrode module as operating in absorption excitation mode as an example, the first multiplexer S1 of the nth active electrode module is closed, the second multiplexer S2 selects the second terminal, and the third multiplexer S3 selects the first input source. The first multiplexer S1 of the (n+1)th active electrode module is open, the second multiplexer S2 selects the second terminal, and the third multiplexer S3 selects the first input source. In addition, the first multiplexer S1 of the 1st to (n-1)th active electrode modules and the (n+2)th to Nth active electrode modules are open, the second multiplexer S2 selects the first terminal, and the third multiplexer S3 selects the first input source.

[0079] At this point, the current source subunit of the nth active electrode module, the electrode of the nth active electrode module, the object under test, the electrode of the (n+2)th active electrode module, and the current collection subunit of the nth active electrode module constitute a closed excitation current signal transmission path.

[0080] According to embodiments of this disclosure, without changing the circuit connection relationship of multiple active electrode modules in the system, the controller controls the switching / selection state of multiple multiple multiplexers of each of the multiple active electrode modules, and configures adjacent first active electrode modules or non-adjacent first active electrode modules and second active electrode modules, so as to realize the measurement of electrical impedance information of different tissues in the object under test according to the actual needs of the application scenario.

[0081] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present disclosure. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions indicated in the blocks may occur in a different order than those indicated in the drawings. For example, two consecutively indicated blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in a block diagram or flowchart, and combinations of blocks in a block diagram or flowchart, may be implemented using a dedicated hardware-based system that performs the specified function or operation, or using a combination of dedicated hardware and computer instructions. Those skilled in the art will understand that the features described in the various embodiments of the present disclosure can be combined and / or combined in various ways, even if such combinations are not explicitly described in the present disclosure. In particular, the features described in the various embodiments of this disclosure may be combined and / or combined in various ways without departing from the spirit and teachings of this disclosure. All such combinations and / or combinations fall within the scope of this disclosure.

[0082] The embodiments of this disclosure have been described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of this disclosure. Although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of this disclosure, and all such substitutions and modifications should fall within the scope of this disclosure.

Claims

1. A power impedance imaging system based on digital active electrodes, characterized in that, include: Multiple active electrode modules are cascaded and connected end-to-end. Each active electrode module includes a first active electrode module operating in excitation mode and a second active electrode module operating in acquisition mode. Each active electrode module includes: Electrodes placed on the surface of the object to be measured; A controller is configured to set the active electrode module to the excitation mode or the acquisition mode. A current generation unit is used to provide an excitation current signal to the electrode when the operating mode is the excitation mode; A voltage acquisition unit is used to acquire a digital voltage signal obtained by the object under test in response to the excitation current signal provided by the first active electrode module when the working mode is the acquisition mode. The demodulation unit is used to demodulate the digital voltage signal to obtain voltage information corresponding to the active electrode module; The main control module, which is connected to each of the plurality of active electrode modules, is used to generate an impedance distribution image corresponding to the object under test based on the voltage information received from each of the plurality of active electrode modules.

2. The system according to claim 1, characterized in that, The current generating unit includes: A digital-to-analog converter, used to generate an excitation voltage signal when the operating mode is the excitation mode; A voltage-controlled current source is used to convert the excitation voltage signal into the excitation current signal and provide the excitation current signal to the electrode when the operating mode is the excitation mode.

3. The system according to claim 2, characterized in that, The excitation mode includes an outflow excitation mode and an absorption excitation mode. The first active electrode module includes an outflow electrode module operating in the outflow excitation mode and an absorption electrode module operating in the absorption excitation mode. The voltage-controlled current source includes: A current source subunit is used to convert the excitation voltage signal into the excitation current signal and provide the excitation current signal to the electrode when the operating mode is the outflow excitation mode; A current manifold unit is used to provide a target return path for the excitation current signal to absorb the excitation current signal, wherein the target return path is the path formed by the electrode of the absorption electrode module and the current manifold unit of the outflow electrode module.

4. The system according to claim 3, characterized in that, Each of the plurality of active electrode modules further includes a first multiplexer and a second multiplexer. For the nth active electrode module: the first terminal of the first multiplexer and the first terminal of the second multiplexer are both connected to the electrode; the second terminal of the second multiplexer and the second terminal of the first multiplexer are connected to the (n+1)th active electrode module; the third terminal of the second multiplexer is connected to the (n-1)th active electrode module; the third terminal of the first multiplexer is connected to the current source subunit; and the fourth terminal of the first multiplexer is connected to the current collector subunit. The (n+1)th active electrode module is a next-level active electrode module cascaded with the nth active electrode module, and the (n-1)th active electrode module is a previous-level active electrode module cascaded with the nth active electrode module. 1 < n < N, where N is the total number of the plurality of active electrode modules, and n and N are both positive integers. The controller is also configured to configure the active electrode module to the excitation mode or the acquisition mode by controlling the gating state of the first multiplexer and the second multiplexer respectively.

5. The system according to claim 4, characterized in that, When the outflow electrode module and the absorption electrode module are adjacent, the first multiplexer of the outflow electrode module is closed and the second multiplexer is selected at the second terminal, while the first multiplexer of each active electrode module other than the outflow electrode module is open and the second multiplexer is selected at the first terminal.

6. The system according to claim 4, characterized in that, When the outflow electrode module and the absorption electrode module are not adjacent, the first multiplexer of the outflow electrode module is closed and the second multiplexer is selected at the second terminal; the first multiplexer of the active electrode module between the outflow electrode module and the absorption electrode module is open and the second multiplexer is selected at the second terminal; the first multiplexer of each active electrode module other than the outflow electrode module and the active electrode module between the absorption electrode module and the outflow electrode module is open and the second multiplexer is selected at the first terminal.

7. The system according to claim 4, characterized in that, The current generation unit further includes a sampling resistor, and the current source subunit is connected to the first connection of the first multiplexer via the sampling resistor; The controller is also used to adjust the amplitude of the excitation voltage signal output by the digital-to-analog converter according to the ratio between the voltage across the sampling resistor and the resistance value of the sampling resistor, so that the ratio satisfies the preset excitation current.

8. The system according to claim 2, characterized in that, The controller is also configured to sequentially configure the operating modes of every two adjacent active electrode modules (excluding the first active electrode module) to the acquisition mode.

9. The system according to claim 7, characterized in that, The voltage acquisition unit includes: The preprocessing subunit is used to preprocess the received first initial voltage signal and second initial voltage signal respectively to obtain the first intermediate voltage signal and the second intermediate voltage signal. An analog-to-digital converter is used to convert the difference between the first intermediate voltage signal and the second intermediate voltage signal into the digital voltage signal; Wherein, the first initial voltage signal is the voltage signal generated by the current second active electrode module in response to the excitation current signal, and the second initial voltage signal is the voltage signal generated by the next active electrode module cascaded with the current second active electrode module in response to the excitation current signal.

10. The system according to claim 9, characterized in that, The voltage information includes the real part and the imaginary part of the digital voltage signal; The demodulation unit is also used to send the real part data and the imaginary part data to the controller; The controller is also used to send the real data and the imaginary data to the main control module via a data line.

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