EIT electrode detachment detection circuit, method and EIT device

Abstract

The present application proposes an EIT electrode detachment detection circuit, method and EIT device, the EIT electrode detachment detection circuit includes a voltage-controlled current source, a multi-way analog switch and a peak holding circuit, the output end of the voltage-controlled current source is connected to the input end of the multi-way analog switch, the output end of the multi-way analog switch is connected to a plurality of electrode pairs, and the output end of the voltage-controlled current source is connected to the input end of the peak holding circuit. The present invention can quickly output the voltage-controlled current source to each electrode pair through the multi-way analog switch, and then measure the voltage of the voltage-controlled current source to the ground through the peak holding circuit, and can quickly judge whether the electrode pair is detached according to the magnitude of the voltage of the voltage-controlled current source to the ground, thereby improving the electrode detection efficiency.

Description

Technical Field

[0001] The invention relates to an EIT electrode detachment detection circuit, method and EIT equipment, belonging to the technical field of bioelectrical impedance imaging technology and application field. Background Art

[0002] Electrical Impedance Tomography (EIT): Bioelectrical impedance tomography is a type of non-invasive medical imaging. The basic principle is to apply a safe excitation current (voltage) signal to the surface of the target tissue to be measured, and simultaneously measure the voltage (current) signal on the surface of the target tissue. The impedance (or impedance change) image distribution in the detected tissue is obtained using an image reconstruction algorithm based on the measured signal.

[0003] In the process of electrical impedance imaging, due to the nonlinear distribution characteristics of current in the body, the image reconstruction process has serious pathological characteristics. A small disturbance in the measured data may lead to a large reconstruction error, which requires the data acquisition system to have extremely high measurement accuracy. Previous research results show that in addition to the hardware system itself, the contact effect between the electrode and the skin is a key factor affecting the signal measurement quality: when there is poor contact, on the one hand, it will make the measurement system more sensitive to external interference, and on the other hand, the uncertainty of the measurement data will be introduced due to the instability of the contact impedance, which will lead to a decrease in the overall signal quality and artifacts in the imaging results.

[0004] In actual clinical applications, on the one hand, it is necessary to monitor the quality of measurement data to ensure the reliability of imaging data. On the other hand, when some electrodes have contact abnormalities, it is also necessary to quickly locate these electrodes among a large number of electrodes to facilitate timely elimination of problems. Therefore, appropriate methods are needed for detection and judgment. The existing electrode detachment detection technology determines whether it has detached by statistically analyzing the results of multiple measurements, which is time-consuming. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, an object of the present invention is to provide an EIT electrode detachment detection circuit and method, which can quickly detect whether an electrode has detached, thereby improving the electrode detection efficiency.

[0006] According to an embodiment of the present invention, a first solution is provided: an EIT electrode detachment detection circuit, comprising a voltage-controlled current source, a multi-channel analog switch and a peak holding circuit,

[0007] The output end of the voltage-controlled current source is connected to the input end of the multi-way analog switch, the output end of the multi-way analog switch is connected to a plurality of electrode pairs, and the multi-way analog switch is used to connect the output current of the voltage-controlled current source to the corresponding electrode pairs according to the received control signal,

[0008] The output end of the voltage-controlled current source is connected to the input end of the peak holding circuit. The peak holding circuit is used to detect the voltage of the voltage-controlled current source to ground and determine whether the electrode is detached according to the voltage of the voltage-controlled current source to ground.

[0009] Furthermore, as a more preferred implementation scheme of the present invention, the peak holding circuit includes a comparison unit and a threshold voltage unit, the output end of the voltage-controlled current source is connected to the first input end of the comparison unit, and the output end of the threshold voltage unit is connected to the second input end of the comparison unit.

[0010] Further, as a more preferred embodiment of the present invention, the comparison unit includes a first comparator, a digital potentiometer and a second comparator, the first input terminal of the first comparator is connected to the output terminal of the voltage-controlled current source, the second input terminal of the first comparator is connected to the output terminal of the digital potentiometer, the output terminal of the first comparator is connected to the input terminal of the digital potentiometer, the output terminal of the digital potentiometer is connected to the second input terminal of the second comparator, and the output terminal of the threshold voltage unit is connected to the first input terminal of the second comparator.

[0011] Furthermore, as a more preferred embodiment of the present invention, it also includes a control unit, and the output end of the control unit is connected to the input end of the multi-channel analog switch.

[0012] Furthermore, as a more preferred implementation scheme of the present invention, it also includes a control unit including a single chip microcomputer, MCU or FPGA.

[0013] According to an embodiment of the present invention, another solution is provided as a method for detecting the detachment of an EIT electrode, which comprises the following steps:

[0014] S1, output the voltage-controlled current source to the corresponding electrode pair through a multi-way analog switch;

[0015] S2. Measure the voltage of the voltage-controlled current source to ground through a peak holding circuit, and determine whether the electrode pair is detached according to the voltage of the voltage-controlled current source to ground.

[0016] Further, as a more preferred embodiment of the present invention, step S2 comprises:

[0017] A comparison unit is used to compare the voltage of the voltage-controlled current source to ground with the voltage of the threshold voltage unit. When the voltage of the voltage-controlled current source to ground is higher than the voltage of the threshold voltage unit, the electrode pair is in a detached state.

[0018] Further, as a more preferred embodiment of the present invention, step S1 comprises:

[0019] The control unit outputs a control signal to the multi-way analog switch, and the multi-way analog switch outputs the voltage-controlled current source to the corresponding electrode pairs in sequence according to the control signal.

[0020] Furthermore, as a more preferred embodiment of the present invention, the step S2 further includes:

[0021] S3. Reset the peak holding circuit.

[0022] According to an embodiment of the present invention, another solution is provided, which is an EIT device, characterized by comprising any one of the above-mentioned EIT electrode detachment detection circuits.

[0023] Compared with the prior art, the technical solution provided by the present application has the following beneficial effects: the present invention can quickly output the voltage-controlled current source to each electrode pair through a multi-way analog switch, and then measure the voltage of the voltage-controlled current source to the ground through a peak holding circuit, and judge whether the electrode pair has fallen off based on the voltage of the voltage-controlled current source to the ground, so as to quickly detect whether the electrode has fallen off and improve the electrode detection efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a module schematic diagram of the EIT electrode detachment detection circuit of the present invention;

[0025] Figure 2 A schematic diagram of a module of an implementation mode of a peak holding circuit of the present invention;

[0026] Figure 3 A module schematic diagram of another embodiment of a peak holding circuit of the present invention;

[0027] Figure 4 It is a schematic diagram of the process of the EIT electrode detachment detection method of the present invention. DETAILED DESCRIPTION

[0028] In order to enable those skilled in the art to better understand the technical solutions in the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of this application.

[0029] It should be noted that when an element is referred to as being "fixed on" or "set on" another component, it can be directly on the other component or indirectly set on the other component; when a component is referred to as being "connected to" another component, it can be directly connected to the other component or indirectly connected to the other component.

[0030] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "

[0031] The orientations or positional relationships indicated by “horizontal”, “top”, “bottom”, “inside”, “outside”, etc. are based on the orientations or positional relationships shown in the drawings and are only for the convenience of describing the present application and simplifying the description. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, they should not be understood as limitations on the present application.

[0032] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, "multiple" and "several" mean two or more, unless otherwise clearly and specifically defined.

[0033] It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the conditions under which this application can be implemented. Therefore, they have no substantive technical significance. Any structural modification, change in proportional relationship or adjustment of size should still fall within the scope of the technical content disclosed in this application without affecting the effects and purposes that can be achieved by this application.

[0034] In the process of electrical impedance imaging, due to the nonlinear distribution characteristics of current in the body, the image reconstruction process has serious pathological characteristics. A small disturbance in the measured data may lead to a large reconstruction error, which requires the data acquisition system to have extremely high measurement accuracy. In actual clinical applications, on the one hand, it is necessary to monitor the quality of the measured data to ensure the reliability of the imaging data. On the other hand, when some electrodes have contact abnormalities, it is also necessary to quickly locate these electrodes among a large number of electrodes to facilitate timely elimination of the problem. Therefore, appropriate methods are needed for detection and judgment. The existing electrode detachment detection technology is to determine whether it is detached by statistically analyzing the results of multiple measurements, which is time-consuming.

[0035] In order to solve the above technical problems, the present invention provides an EIT electrode detachment detection circuit, referring to Figure 1The EIT electrode detachment detection circuit includes a voltage-controlled current source, a multi-channel analog switch, a control unit and a peak holding circuit, wherein the output end of the control unit is connected to the input end of the multi-channel analog switch. The output end of the voltage-controlled current source is connected to the input end of the multi-channel analog switch, and the output end of the multi-channel analog switch is connected to a plurality of electrode pairs. The multi-channel analog switch is used to connect the output current of the voltage-controlled current source to the corresponding electrode pair according to the received control signal. The output end of the voltage-controlled current source is connected to the input end of the peak holding circuit. The peak holding circuit is used to detect the voltage of the voltage-controlled current source to the ground, and judge whether the electrode is detached according to the voltage of the voltage-controlled current source to the ground.

[0036] In the technical scheme, it should be noted that in the process of electrical impedance imaging of adjacent driving modes, each frame imaging needs to have 16 pairs of different excitation electrode pairs, so there are 16 electrodes (i.e. electrode 1, electrode 2, electrode 3, electrode 4 ... electrode 16) in the present embodiment, and the voltage-controlled current source is used as the excitation source of the electrode, and the voltage-controlled current source includes a P end and an N end, and the P end and the N end are opposite to each other. The two input ends of the multi-way analog switch are respectively connected to the P end and the N end of the voltage-controlled current source, and the multi-way analog switch has 16 output ends respectively connected to the 16 electrodes. The control unit includes a single-chip microcomputer, an MCU or an FPGA, and the control unit outputs a control signal to the control end of the multi-way analog switch, and the multi-way analog switch switches the voltage-controlled current source according to the control signal to output the excitation source to 16 pairs of different excitation electrode pairs (electrode 1 and electrode 2, electrode 2 and electrode 3, and so on). The peak holding circuit connects the P end or the N end of the voltage-controlled current source, measures the voltage to ground of the P end or the N end, and determines whether the excitation electrode falls off by the voltage to ground. Due to the design of the voltage-controlled current source, when the excitation electrode falls off, the voltage-controlled current source will still generate a current of the same magnitude. At this time, due to the existence of parasitic parameters such as parasitic capacitance and parasitic resistance in each link of the device, the current generated by the voltage-controlled current source can indeed flow to the ground plane through these parasitic parameters. However, due to these parasitic parameters, its equivalent impedance is very large. According to Ohm's law U=R*I, the current I remains unchanged, the resistance R increases significantly, and the corresponding voltage U also increases significantly. As a preferred embodiment, in the present invention, the voltage from the P end of the voltage-controlled current source to the ground is measured. The larger the voltage, the greater the load. When the voltage is measured to exceed a certain threshold, it is considered that the electrode has fallen off.

[0037] For a detailed explanation, refer to Figure 2 In an embodiment of the present invention, the peak holding circuit includes a comparison unit and a threshold voltage unit, the output end of the voltage-controlled current source is connected to the first input end of the comparison unit, and the output end of the threshold voltage unit is connected to the second input end of the comparison unit.

[0038] In this technical solution, it should be noted that the threshold voltage unit sets the threshold voltage, and the voltage to ground of the voltage-controlled current source P terminal and the threshold voltage are compared through the comparison unit. When the voltage to ground of the voltage-controlled current source P terminal is greater than the threshold voltage, the excitation electrode connected to the voltage-controlled current source P terminal is in a detached state.

[0039] The present invention can detect electrode detachment while measuring electrical impedance, and has excellent real-time performance. It is more accurate and faster than the existing statistical method. The judgment process is implemented by hardware, which has good reliability, simplicity and efficiency. It makes it possible for operators to eliminate electrode connection abnormalities in a timely and rapid manner, and also provides a reference basis for the evaluation of the quality of continuous electrical impedance data acquisition.

[0040] For a detailed explanation, refer to Figure 3 In an embodiment of the present invention, as a more preferred implementation scheme of the present invention, the comparison unit includes a first comparator, a digital potentiometer and a second comparator, the first input end of the first comparator is connected to the output end of the voltage-controlled current source, the second input end of the first comparator is connected to the output end of the digital potentiometer, the output end of the first comparator is connected to the input end of the digital potentiometer, the output end of the digital potentiometer is connected to the second input end of the second comparator, and the output end of the threshold voltage unit is connected to the first input end of the second comparator.

[0041] In this technical solution, it should be noted that the voltage at the P terminal of the voltage-controlled current source is always compared with the output of the digital potentiometer. Among them, when the output of the digital potentiometer is less than the voltage of the voltage-controlled current source P, the output of the first comparator is pulled low, which will trigger the output of the digital potentiometer to increase. When the output of the digital potentiometer increases to a voltage greater than the voltage at the P terminal of the voltage-controlled current source, the output of the first comparator becomes a high level, and the output of the digital potentiometer no longer increases. The output of the digital potentiometer is the peak value of the voltage-controlled current source P. The second comparator can determine whether the electrode has fallen off by comparing the peak value with the threshold voltage output of the threshold voltage unit. When the peak value is greater than the threshold voltage, it means that the excitation electrode connected to the P terminal of the voltage-controlled current source has fallen off, and the second comparator outputs a low level; otherwise, it outputs a high level, indicating that the electrode is normal.

[0042] Further as a preferred embodiment, the output end of the second comparator can be connected to a response device, so that the user can more intuitively feel whether the electrode has fallen off. The response device includes a sound device, a light-emitting device or a display screen. When the diode falls off, the sound device emits a sound warning, the diode or light bulb lights up, and the display shows words such as "electrode falls off".

[0043] refer to Figure 4 According to an embodiment of the present invention, another scheme is provided for a method for detecting the detachment of an EIT electrode, which comprises the following steps:

[0044] S1, output the voltage-controlled current source to the corresponding electrode pair through a multi-way analog switch;

[0045] Specifically, the control unit outputs a control signal to the multi-way analog switch, and the multi-way analog switch outputs the voltage-controlled current source to the corresponding electrode pairs in sequence according to the control signal.

[0046] S2. Measure the voltage of the voltage-controlled current source to ground through a peak holding circuit, and determine whether the electrode pair is detached according to the voltage of the voltage-controlled current source to ground.

[0047] Specifically, a comparison unit is used to compare the voltage of the voltage-controlled current source to ground with the voltage of the threshold voltage unit. When the voltage of the voltage-controlled current source to ground is higher than the voltage of the threshold voltage unit, the excitation electrode connected to the voltage-controlled current source is in a detached state.

[0048] Furthermore, as a more preferred embodiment of the present invention, the step S2 further includes:

[0049] S3. Reset the peak holding circuit.

[0050] During the actual operation of the present invention, since the electrodes connected to the voltage-controlled current source P will be switched in sequence, after each switch, it can be determined whether the electrode connected at this time has fallen off. For example, during each frame of imaging, the voltage-controlled current source P will switch to electrodes 1, 2, 3, ... 15, and 16 in sequence. When electrode 1 is connected, it can be determined whether electrode 1 has fallen off; when electrode 2 is connected, it can be determined whether electrode 2 has fallen off, and so on. Since the voltage at the end of the voltage-controlled current source P is always compared with the output of the digital potentiometer. The output of the digital potentiometer will increase or decrease during each comparison process. Therefore, before each judgment of falling off, the digital potentiometer needs to be cleared. This operation can be achieved by outputting a control signal to the chip.

[0051] According to an embodiment of the present invention, another solution is provided, which is an EIT device, comprising the above-mentioned EIT electrode detachment detection circuit.

[0052] In this technical solution, it should be noted that the monitor needs to wear an electrode belt with electrodes. The present invention applies a safe excitation current (voltage) signal on the surface of the target tissue to be measured, and at the same time measures the voltage (current) signal on the surface of the target tissue, analyzes and calculates the impedance information carried by the corresponding position, and uses this as a basis for bioimpedance imaging. At the same time, the EIT electrode detachment detection circuit in the present invention detects whether the electrode has fallen off, and the real-time performance is very good. It is more accurate and faster than the existing statistical methods, and the judgment and other processes are implemented by hardware, which has good reliability, simplicity and efficiency. It makes it possible for operators to eliminate electrode connection abnormalities in a timely and rapid manner, and also provides a reference basis for the evaluation of the quality of continuous impedance data acquisition.

[0053] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An EIT electrode detachment detection circuit, characterized in that: Including voltage-controlled current source, multi-channel analog switch and peak hold circuit, The output end of the voltage-controlled current source is connected to the input end of the multi-way analog switch, the output end of the multi-way analog switch is connected to a plurality of electrode pairs, and the multi-way analog switch is used to connect the output current of the voltage-controlled current source to the corresponding electrode pairs according to the received control signal, The output end of the voltage-controlled current source is connected to the input end of the peak holding circuit, and the peak holding circuit is used to detect the voltage of the voltage-controlled current source to the ground, and judge whether the electrode is detached according to the voltage of the voltage-controlled current source to the ground; The peak holding circuit comprises a comparison unit and a threshold voltage unit, the output end of the voltage-controlled current source is connected to the first input end of the comparison unit, and the output end of the threshold voltage unit is connected to the second input end of the comparison unit; The comparison unit includes a first comparator, a digital potentiometer and a second comparator, wherein the first input terminal of the first comparator is connected to the output terminal of the voltage-controlled current source, the second input terminal of the first comparator is connected to the output terminal of the digital potentiometer, the output terminal of the first comparator is connected to the input terminal of the digital potentiometer, the output terminal of the digital potentiometer is connected to the second input terminal of the second comparator, and the output terminal of the threshold voltage unit is connected to the first input terminal of the second comparator.

2. The EIT electrode detachment detection circuit according to claim 1, characterized in that: It also includes a control unit, the output end of the control unit is connected to the input end of the multi-channel analog switch.

3. The EIT electrode detachment detection circuit according to claim 2, characterized in that: It also includes a control unit including a single chip microcomputer, MCU or FPGA.

4. A method for detecting EIT electrode detachment, characterized in that: The EIT electrode detachment detection circuit applied to any one of claims 1 to 3, wherein the EIT electrode detachment detection method comprises the following steps: S1, output the voltage-controlled current source to the corresponding electrode pair through a multi-way analog switch; S2. Measure the voltage of the voltage-controlled current source to ground through a peak holding circuit, and determine whether the electrode pair is detached according to the voltage of the voltage-controlled current source to ground.

5. The EIT electrode detachment detection method according to claim 4, characterized in that: The step S2 comprises: A comparison unit is used to compare the voltage of the voltage-controlled current source to ground with the voltage of the threshold voltage unit. When the voltage of the voltage-controlled current source to ground is higher than the voltage of the threshold voltage unit, the electrode pair is in a detached state.

6. The EIT electrode detachment detection method according to claim 4, characterized in that: The step S1 comprises: The control unit outputs a control signal to the multi-way analog switch, and the multi-way analog switch outputs the voltage-controlled current source to the corresponding electrode pairs in sequence according to the control signal.

7. The EIT electrode detachment detection method according to claim 4, characterized in that: After step S2, the method further includes: S3, resetting the peak holding circuit.

8. An EIT device, characterized in that: It comprises the EIT electrode detachment detection circuit as claimed in any one of claims 1 to 3.

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