Method and system for electrical impedance tomography of blood perfusion

Abstract

The present disclosure provides a blood perfusion electrical impedance imaging method and system, the blood perfusion electrical impedance imaging method comprising: acquiring a real-time photoplethysmographic pulse wave signal at a fingertip of a target object; arranging n groups of electrode pairs to form an array sensor, each group of electrode pairs comprising two electrodes, and n being an integer not less than 4; arranging the array sensor along a circumferential direction of a chest cavity of the target object; in an adjacent excitation measurement mode, applying an excitation current to a first electrode pair, sequentially measuring voltage difference data of each of the other electrode pairs except the first electrode pair, and cyclically applying the excitation current to the electrodes to obtain a plurality of impedance values; performing equal-time-interval sampling on each of the impedance values to obtain an impedance signal corresponding to each of the impedance values, taking the photoplethysmographic pulse wave signal as a reference signal, and respectively performing matched filtering on each of the impedance signals and the reference signal to obtain a blood perfusion signal; and generating a blood perfusion image according to the blood perfusion signal, the blood perfusion image representing a blood perfusion condition of the chest cavity.

Description

Technical Field

[0001] This disclosure relates to the technical field of electrical impedance imaging, and more specifically, to a method and system for electrical impedance imaging of blood perfusion. Background Technology

[0002] Gas exchange in the lungs occurs in the alveoli. For effective gas exchange to occur, the alveoli must be ventilated and perfused. Pulmonary ventilation refers to the process of air flowing into the lungs during inhalation and flowing out during exhalation; its imaging can reflect the condition of the pulmonary airways and alveolar ventilation. Blood perfusion is the result of the combined action of the heart and lungs; its imaging can reflect the pulmonary artery blood supply.

[0003] Traditional imaging methods often employ radionuclide imaging, requiring the inhalation of radioactive particles or gases as imaging agents. Combining single-photon emission computed tomography (SPECT) and computed tomography (CT) can provide images of lung ventilation or perfusion. However, due to its susceptibility to respiratory system interference, the invasiveness of radioactive particles, and the potential for X-ray beam damage to biological cells, it cannot be used frequently as a long-term monitoring tool for patients.

[0004] Imaging is a traditional method for assessing lung perfusion. During breath-holding, a "ball-like" injection of hypertonic saline (such as a 10% NaCl solution) is administered. The resistance change caused by the saline flowing through the bloodstream indicates the perfusion volume. The disadvantages of this method are that breath-holding affects pulmonary blood flow, it cannot be imaged simultaneously with respiratory signals, and recalibration is required for experiments on different individuals.

[0005] Therefore, the urgent technical problem to be solved is how to separate the blood perfusion signal from the impedance signal. Summary of the Invention

[0006] To address at least one of the technical problems described above and in other aspects in the prior art, embodiments of this disclosure provide a method and system for electrical impedance imaging of blood perfusion, which can perform real-time imaging, avoid the influence of breath-holding on blood flow status, and has fast filtering speed and strong noise suppression capability. By combining photoplethysmography pulse wave signals and impedance signals, the dimensions and levels of the data source are increased, thereby improving the reliability of blood perfusion signals.

[0007] This disclosure provides an impedance imaging method for blood perfusion, comprising: acquiring real-time photoplethysmography (PPG) signals at the fingertips of a target object; arranging n sets of electrode pairs into an array sensor, wherein each set of electrode pairs includes two electrodes, and n is an integer not less than 4; setting the array sensor along the circumferential direction of the chest cavity of the target object; applying an excitation current to a first electrode pair in an adjacent excitation measurement mode, sequentially measuring the voltage difference data of each of the other electrode pairs except the first electrode pair, cyclically applying the excitation current to the electrodes to obtain multiple impedance values; sampling each impedance value at equal time intervals to obtain an impedance signal corresponding to each impedance value; using the PPG signals as reference signals and performing matched filtering on each impedance signal to obtain a blood perfusion signal; generating a blood perfusion image based on the blood perfusion signal, wherein the blood perfusion image is used to characterize the blood perfusion status of the chest cavity.

[0008] According to some embodiments of this disclosure, the above-mentioned acquisition of real-time photoplethysmography (PPG) signals at the fingertips of the target object includes: conditioning the PPG signals to filter out noise in the PPG signals.

[0009] According to some embodiments of this disclosure, in the adjacent excitation measurement mode, applying an excitation current to the first electrode pair, sequentially measuring the voltage difference data of other electrode pairs besides the first electrode pair, and cyclically applying the excitation current to the electrodes to obtain multiple impedance values ​​includes: comparing the multiple voltage difference data with the excitation current to obtain multiple impedance values.

[0010] According to some embodiments of this disclosure, the above-mentioned sampling of each of the above-mentioned impedance values ​​at equal time intervals to obtain an impedance signal corresponding to each of the above-mentioned impedance values, and the use of the above-mentioned photoplethysmography (PPG) signal as a reference signal to perform matched filtering with each of the above-mentioned impedance signals to obtain a blood perfusion signal includes: using the above-mentioned PPG signal as a reference signal to extract the blood perfusion signal by frequency domain analysis.

[0011] According to some embodiments of this disclosure, the above-mentioned generation of a blood perfusion image based on the blood perfusion signal, wherein the blood perfusion image is used to characterize the blood perfusion status of the pleural cavity includes: generating a blood perfusion image based on the blood perfusion signal using an image reconstruction algorithm.

[0012] Another aspect of the embodiments of this disclosure provides a blood perfusion electrical impedance imaging system, comprising: an array sensor disposed circumferentially on the lateral side of the chest cavity of a target object; a photoplethysmography (PPG) acquisition unit disposed at the fingertip of the target object, the PPG acquisition unit being adapted to acquire real-time PPG signals; a multi-channel impedance measurement unit configured to be connected to the array sensor, the multi-channel impedance measurement unit being adapted to apply an excitation current to the array sensor and acquire impedance values; a control unit configured to be connected to the multi-channel impedance measurement unit for controlling the multi-channel impedance measurement unit; a frequency domain analysis unit configured to be connected to both the multi-channel impedance measurement unit and the PPG acquisition unit, the frequency domain analysis unit being adapted to separate blood perfusion signals; and an image reconstruction unit configured to be connected to the frequency domain analysis unit, the image reconstruction unit being adapted to generate blood perfusion images based on the blood perfusion signals.

[0013] According to some embodiments of this disclosure, the array sensor described above consists of a plurality of electrodes arranged in a row.

[0014] According to some embodiments of the present disclosure, the above-described blood perfusion electrical impedance imaging system further includes: a signal conditioning unit configured to be connected between the photoplethysmography (PPG) acquisition unit and the frequency domain analysis unit, wherein the signal conditioning unit is adapted to filter out noise in the PPG signal.

[0015] According to some embodiments of this disclosure, the frequency domain analysis unit described above is composed of a matched filter.

[0016] According to an embodiment of the present disclosure, a method and system for electrical impedance imaging of blood perfusion combines photoplethysmography (PPI) signals and impedance signals. Using the PPI signal as a reference signal, it performs matched filtering with multiple impedance signals to obtain a blood perfusion signal. A blood perfusion image is generated based on the blood perfusion signal. The blood perfusion image is used to characterize the blood perfusion status of the pleural cavity. It can perform real-time imaging, avoids the influence of breath-holding on blood flow status, and has fast filtering speed and strong noise suppression capability. Combining PPI signals and impedance signals increases the dimension and level of the data source and improves the reliability of the blood perfusion signal. Attached Figure Description

[0017] Figure 1 This is a flowchart of a blood perfusion electrical impedance imaging method according to an illustrative embodiment of the present disclosure;

[0018] Figure 2 This is a structural diagram of a blood perfusion electrical impedance imaging system according to an illustrative embodiment of the present disclosure; and

[0019] Figure 3This is a schematic diagram of the working principle of a frequency domain analysis unit according to an illustrative embodiment of the present disclosure.

[0020] In the accompanying drawings, the meanings of the reference numerals are as follows:

[0021] 1. Array sensor;

[0022] 2. Photoplethysmography (PPG) acquisition unit;

[0023] 3. Multi-channel impedance measurement unit;

[0024] 4. Control unit;

[0025] 5. Signal conditioning unit;

[0026] 6. Frequency domain analysis unit;

[0027] 7. Image reconstruction unit. Detailed Implementation

[0028] 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.

[0029] 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.

[0030] 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.

[0031] When using expressions such as "at least one of A, B, and C," the expression should generally be interpreted in accordance with the meaning commonly understood by a person skilled in the art (e.g., "a system having at least one of A, B, and C" should include, but is not limited to, systems having A alone, having B alone, having C alone, having A and B, having A and C, having B and C, and / or having A, B, and C, etc.). Similarly, when using expressions such as "at least one of A, B, or C," the expression should generally be interpreted in accordance with the meaning commonly understood by a person skilled in the art (e.g., "a system having at least one of A, B, or C" should include, but is not limited to, systems having A alone, having B alone, having C alone, having A and B, having A and C, having B and C, and / or having A, B, and C, etc.).

[0032] According to one aspect of the inventive concept of this disclosure, Electrical Impedance Tomography (EIT) is a non-invasive, radiation-free, real-time imaging method that is inexpensive, portable, and can be used as a long-term monitoring tool. By continuously rotating a current injection and voltage measurement around the chest, electrical impedance tomography can obtain a tissue impedance distribution map on a cross-section of the chest. Electrical impedance tomography can perform functional imaging of the lungs, obtaining information on lung overinflation or collapse that cannot be shown by CT. In addition, it can provide information on regional lung ventilation or perfusion. However, when using electrical impedance tomography for chest examination during respiration, ventilation volume dominates its impedance signal, accounting for the majority of the impedance signal energy, while the blood perfusion signal is much smaller than the ventilation signal. Therefore, to address the challenge of extracting blood perfusion signals from impedance signals, this disclosure employs a method that combines photoplethysmography (PPG) signals with impedance signals. Using the PPG signals as a reference signal, matched filtering is performed with multiple impedance signals to obtain the blood perfusion signal. A blood perfusion image is then generated based on this signal. This image characterizes the blood perfusion status of the pleural cavity, enabling real-time imaging and avoiding the influence of breath-holding on blood flow. Furthermore, it features fast filtering speed and strong noise suppression capabilities. Combining PPG signals with impedance signals increases the dimension and level of the data source, thereby improving the reliability of the blood perfusion signal.

[0033] Figure 1 This is a flowchart of a blood perfusion electrical impedance imaging method according to an illustrative embodiment of the present disclosure.

[0034] According to embodiments of this disclosure, such as Figure 1 As shown, a blood perfusion electrical impedance imaging method includes the following steps S1-S6.

[0035] Step S1: Acquire the real-time photoplethysmography (PPG) signal at the fingertip of the target object.

[0036] Step S2: Arrange n sets of electrode pairs to form an array sensor 1. Each set of electrode pairs includes two electrodes, and n is an integer not less than 4.

[0037] Step S3: Set up array sensor 1 along the circumferential direction of the target object's chest cavity.

[0038] Step S4: In the adjacent excitation measurement mode, apply excitation current to the first electrode pair, measure the voltage difference data of each of the other electrode pairs except the first electrode pair in sequence, apply excitation current to the electrodes in a cyclic manner, and obtain multiple impedance values.

[0039] Step S5: Sample each impedance value at equal time intervals to obtain the impedance signal corresponding to each impedance value. Use the photoplethysmography pulse wave signal as a reference signal and perform matched filtering with each impedance signal to obtain the blood perfusion signal.

[0040] Step S6: Generate a blood perfusion image based on the blood perfusion signal. The blood perfusion image is used to characterize the blood perfusion status of the pleural cavity.

[0041] According to embodiments of this disclosure, the target object can be the human body.

[0042] According to embodiments of this disclosure, during the cardiac cycle, the blood flowing through the arterioles, capillaries, and venules in peripheral blood vessels exhibits corresponding pulsatile changes. The blood volume is largest during cardiac contraction and smallest during cardiac diastole. This pulsatile change in the photoplethysmography (PPG) signal is obtained using a PPG sensor, and the resulting waveform contains PPG blood flow information. Therefore, systolic and diastolic blood pressure can be obtained through the relationship between PPG blood flow information and blood pressure signals.

[0043] According to the embodiments of this disclosure, n sets of electrode pairs can be 8 sets of electrode pairs, each set of electrode pairs includes two electrodes, that is, 16 electrodes. Each electrode is arranged to form an array sensor 1 and is labeled 1, 2, 3...16 respectively. The array sensor 1 can be composed of 4, 8 or 16 electrodes.

[0044] According to an embodiment of the present disclosure, in the adjacent excitation measurement mode, an excitation current is applied to the first electrode pair (1, 2), and the voltage difference data of each of the other electrode pairs (2, 3), (3, 4), (4, 5)...(15, 16), (16, 1) are measured in sequence, wherein the effective voltage difference data are the voltage difference data of each of the electrode pairs (3, 4), (4, 5)...(15, 16).

[0045] According to embodiments of this disclosure, by combining photoplethysmography (PPG) signals and impedance signals, using the PPG signals as reference signals, and performing matched filtering with multiple impedance signals respectively, a blood perfusion signal is obtained. A blood perfusion image is generated based on the blood perfusion signal. The blood perfusion image is used to characterize the blood perfusion status of the pleural cavity, enabling real-time imaging, avoiding the influence of breath-holding on blood flow status, and exhibiting fast filtering speed and strong noise suppression capability. Combining PPG signals and impedance signals increases the dimension and level of the data source, improving the reliability of the blood perfusion signal.

[0046] According to embodiments of this disclosure, acquiring a real-time photoplethysmography (PPG) signal at the fingertip of a target object includes: conditioning the PPG signal to filter out noise in the PPG signal.

[0047] According to embodiments of this disclosure, filtering out noise in the photoplethysmography (PPG) signal ensures signal quality when the PPG signal is used as a reference signal.

[0048] According to embodiments of this disclosure, in an adjacent excitation measurement mode, an excitation current is applied to a first electrode pair, and the voltage difference data of each of the other electrode pairs (excluding the first electrode pair) is measured sequentially. The excitation current is cyclically applied to the electrodes to obtain multiple impedance values, including: comparing the multiple voltage difference data with the excitation current to obtain multiple impedance values; and sampling each impedance value at equal time intervals to obtain an impedance signal corresponding to each impedance value.

[0049] According to embodiments of this disclosure, the impedance signal can be represented by the following formula (1):

[0050]

[0051] Where Z represents the impedance signal, I represents the applied excitation current, and U represents the voltage difference data between the other electrode pairs.

[0052] According to embodiments of this disclosure, since different tissues within the target body have different electrical characteristics, the obtained impedance value can reflect the corresponding state and functional information of the electrical characteristics of different tissues within the body, which is simple to operate and low in cost.

[0053] According to an embodiment of this disclosure, taking 16 electrodes as an example, after applying an excitation current to the first electrode pair (1, 2) and measuring the voltage difference data of the other electrode pairs, an excitation current is applied to the electrode pair (2, 3), and the voltage difference data of the other electrode pairs (4, 5), (5, 6), (6, 7)...(15, 16), (16, 1) are measured sequentially. Then, an excitation current is applied to the electrode pair (3, 4), and the voltage difference data of the other electrode pairs (5, 6), (6, 7), (7, 8)...(15, 16), (16, 1), (1, 2) are measured sequentially. This process is repeated, applying excitation current to the 16 electrodes cyclically to obtain 208 channels of effective voltage difference data. Half of the data is repeated, resulting in 104 channels of effective voltage difference data. These are then compared with their corresponding excitation currents to obtain 104 impedance values.

[0054] According to embodiments of this disclosure, if there are n groups of electrode pairs, the number N of effective voltage difference data can be represented by the following formula (2):

[0055]

[0056] Where N represents the number of effective voltage difference data.

[0057] According to embodiments of this disclosure, obtaining effective voltage difference data can reduce errors during matched filtering.

[0058] According to embodiments of this disclosure, sampling each impedance value at equal time intervals to obtain an impedance signal corresponding to each impedance value, and using the photoplethysmography (PPG) signal as a reference signal, performing matched filtering with multiple impedance signals respectively to obtain a blood perfusion signal includes: using the PPG signal as a reference signal, extracting the blood perfusion signal through frequency domain analysis.

[0059] According to embodiments of this disclosure, for a time series Z(i) consisting of impedance values, Z(i) is affected by both respiration and blood perfusion, and Z(i) can be expressed by the following formula (3):

[0060] Z(i) = aZ c (i)+bZ L (i)+σ (3)

[0061] Among them, Z c (i) represents the blood flow impedance value, a represents the coefficient of the blood flow impedance value, and Z L (i) represents the respiratory impedance value, b represents the coefficient of the respiratory impedance value, and σ represents other factors that affect the impedance value besides blood flow and respiration.

[0062] According to embodiments of this disclosure, due to the blood flow impedance value Zc (i) and respiratory impedance Z L (i) Since the frequency band range is different, the blood perfusion signal can be extracted using frequency domain analysis.

[0063] According to an embodiment of this disclosure, a single photoplethysmography (PPG) signal is used as a reference signal and matched with multiple impedance signals to obtain a blood perfusion signal.

[0064] According to embodiments of this disclosure, frequency domain analysis can perform real-time imaging and is non-invasive to the target object, eliminating the need for the target object to hold its breath and avoiding the impact of breath-holding on blood flow. By using the photoplethysmography (PPG) signal as a reference signal and integrating the PPG signal and impedance signal, the dimensions and levels of the data source are increased, thereby improving the reliability of the blood perfusion signal.

[0065] According to embodiments of this disclosure, generating a blood perfusion image based on a blood perfusion signal, wherein the blood perfusion image is used to characterize the blood perfusion status of the pleural cavity includes: generating the blood perfusion image based on the blood perfusion signal using an image reconstruction algorithm.

[0066] According to embodiments of this disclosure, blood perfusion images are reconstructed in real time using an image reconstruction algorithm to reflect the blood perfusion or blood distribution in the pleural cavity.

[0067] According to embodiments of this disclosure, since the impedance value presented by the target object is different in different states, the state information of the target object can be reflected by the above method.

[0068] According to embodiments of this disclosure, the image reconstruction algorithm has high real-time performance, fast image reconstruction speed, high accuracy, and high reliability.

[0069] According to an optional embodiment of this disclosure, the photoplethysmography (PPG) signal can be replaced by a cardiac electrical signal acquired at the heart location. Using the cardiac electrical signal as a reference signal, a blood perfusion signal is obtained by matched filtering with multiple impedance signals, and then a blood perfusion image is generated based on the blood perfusion signal.

[0070] Figure 2 This is a structural diagram of a blood perfusion electrical impedance imaging system according to an illustrative embodiment of the present disclosure.

[0071] According to embodiments of this disclosure, such as Figure 2As shown, a blood perfusion electrical impedance imaging system includes an array sensor 1, a photoplethysmography (PPG) acquisition unit 2, a multi-channel impedance measurement unit 3, a control unit 4, a frequency domain analysis unit 6, and an image reconstruction unit 7. The array sensor 1 is positioned circumferentially on the lateral side of the target object's chest cavity. The PPG acquisition unit 2 is positioned at the fingertip of the target object and is used to acquire real-time PPG signals. The multi-channel impedance measurement unit 3 is configured to connect to the array sensor 1 and is used to apply an excitation current to the array sensor 1 and acquire impedance values. The control unit 4 is configured to connect to the multi-channel impedance measurement unit 3 and is used to control the multi-channel impedance measurement unit 3. The frequency domain analysis unit 6 is configured to connect to both the multi-channel impedance measurement unit 3 and the PPG acquisition unit 2, and is used to separate the blood perfusion signal. The image reconstruction unit 7 is configured to connect to the frequency domain analysis unit 6 and is used to generate a blood perfusion image based on the blood perfusion signal.

[0072] According to an embodiment of this disclosure, the control unit 4 controls the multi-channel impedance measurement unit 3 to apply an excitation current to the array sensor 1, thereby obtaining the impedance value.

[0073] According to embodiments of this disclosure, the blood perfusion electrical impedance imaging system can perform real-time imaging, avoids the influence of breath-holding on blood flow status, and has fast filtering speed and strong noise suppression capability. By combining photoplethysmography pulse wave signals and impedance signals, it increases the dimension and level of the data source and improves the reliability of blood perfusion signals.

[0074] According to embodiments of this disclosure, the array sensor 1 consists of a plurality of electrodes arranged in a row.

[0075] According to embodiments of this disclosure, arranging multiple electrodes can avoid errors in voltage difference data caused by different spacing between electrodes.

[0076] According to embodiments of the present disclosure, the blood perfusion electrical impedance imaging system further includes a signal conditioning unit 5, which is configured to be connected between the photoplethysmography (PPG) acquisition unit 2 and the frequency domain analysis unit 6. The signal conditioning unit 5 is adapted to filter out noise in the PPG signal.

[0077] According to an embodiment of this disclosure, the control unit 4 simultaneously controls the signal conditioning unit 5 to acquire the photoplethysmography (PPG) signal through the PPG acquisition unit 2.

[0078] According to embodiments of this disclosure, the signal conditioning unit ensures the signal quality of the photoplethysmography (PPG) signal.

[0079] Figure 3This is a schematic diagram illustrating the working principle of a frequency domain analysis unit 6 according to an illustrative embodiment of the present disclosure.

[0080] According to embodiments of this disclosure, such as Figure 3 As shown, the frequency domain analysis unit 6 is composed of matched filters.

[0081] According to embodiments of this disclosure, the photoplethysmography (PPG) signal and impedance signal are transmitted to the frequency domain analysis unit 6, the blood perfusion signal is separated using a matched filter, and the blood perfusion signal is transmitted to the image reconstruction unit 7 to generate a blood perfusion image.

[0082] According to an embodiment of this disclosure, a matched filter is used to separate the blood perfusion signal. Taking 16 electrodes as an example, one noise-filtered photoplethysmography (PPG) signal is used as a reference signal and matched with 104 impedance values ​​to obtain 104 blood perfusion signals. The blood perfusion signal reaches its peak at a specific moment when the matched filter outputs.

[0083] According to embodiments of this disclosure, the matched filter has a fast filtering speed and strong noise suppression capability, which can meet the real-time requirements of lung perfusion imaging, and there is no need to adjust the coefficients of the matched filter according to heart rate and respiratory rate.

[0084] It should also be noted that the directional terms mentioned in the embodiments, such as "up," "down," "front," "back," "left," and "right," are only for reference to the directions in the accompanying drawings and are not intended to limit the scope of protection of this disclosure. Throughout the drawings, the same elements are represented by the same or similar reference numerals. Conventional structures or constructions will be omitted where they may cause confusion in understanding this disclosure, and the shapes and dimensions of the components in the drawings do not reflect actual size and proportion, but are only schematic representations of the embodiments of this disclosure.

[0085] Unless otherwise stated, the numerical parameters in this specification and the appended claims are approximate values ​​and can be varied according to desired characteristics derived from the content of this disclosure. Specifically, all figures used in the specification and claims to indicate composition, reaction conditions, etc., should be understood to be modified by the term "about" in all cases. Generally, this means that a specific amount varies by ±10% in some embodiments, ±5% in some embodiments, ±1% in some embodiments, and ±0.5% in some embodiments.

[0086] The use of ordinal numbers such as "first," "second," "third," etc., in the specification and claims to modify the corresponding elements does not imply that the element has any ordinal number, nor does it represent the order of one element with another element, or the order of manufacturing methods. The use of these ordinal numbers is only to enable a named element to be clearly distinguished from another element with the same name.

[0087] Furthermore, unless specifically described or required to occur in a specific order, the order of the above steps is not limited to those listed above and can be varied or rearranged according to the desired design. Moreover, the above embodiments can be used in combination with each other or with other embodiments based on design and reliability considerations; that is, technical features from different embodiments can be freely combined to form more embodiments.

[0088] 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. The scope of this disclosure is defined by the appended claims and their equivalents. 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 method for electrical impedance imaging of blood perfusion, comprising: Acquire the real-time photoplethysmography (PPG) signal at the fingertip of the target object; n sets of electrode pairs are arranged to form an array sensor, wherein each set of electrode pairs includes two electrodes, and n is an integer not less than 4; The array of sensors is arranged along the circumferential direction of the chest cavity of the target object; In the adjacent excitation measurement mode, an excitation current is applied to the first electrode pair, and the voltage difference data of each of the other electrode pairs except the first electrode pair are measured in sequence. The excitation current is applied to the electrodes in a cyclic manner to obtain multiple impedance values. Each impedance value is sampled at equal time intervals to obtain an impedance signal corresponding to each impedance value. The photoplethysmography pulse wave signal is used as a reference signal and matched with each impedance signal respectively. The blood perfusion signal is obtained by frequency domain analysis. A blood perfusion image is generated based on the blood perfusion signal, wherein the blood perfusion image is used to characterize the blood perfusion status of the pleural cavity.

2. The blood perfusion electrical impedance imaging method according to claim 1, wherein acquiring the real-time photoplethysmography (PPG) signal at the fingertip of the target object includes: The photoplethysmography (PPG) signal is conditioned to filter out noise in the PPG signal.

3. The electrical impedance imaging method for blood perfusion according to claim 1, wherein in the adjacent excitation measurement mode, an excitation current is applied to the first electrode pair, and the voltage difference data of each of the other electrode pairs besides the first electrode pair are measured sequentially, and the excitation current is applied to the electrodes cyclically to obtain multiple impedance values, including: The multiple voltage difference data are compared with the excitation current to obtain multiple impedance values.

4. The electrical impedance imaging method for blood perfusion according to claim 1, wherein generating a blood perfusion image based on the blood perfusion signal, wherein, The blood perfusion images used to characterize the blood perfusion status of the pleural cavity include: A blood perfusion image is generated based on the blood perfusion signal using an image reconstruction algorithm.

5. A blood perfusion electrical impedance imaging system, comprising: An array of sensors is positioned circumferentially on the outer side of the target object's chest cavity; A photoplethysmography (PPG) acquisition unit is installed at the fingertip of the target object. The PPG acquisition unit is suitable for acquiring real-time PPG signals. A multi-channel impedance measurement unit is configured to be connected to the array sensor, the multi-channel impedance measurement unit being adapted to apply an excitation current to the array sensor and acquire impedance values; A control unit is configured to be connected to the multi-channel impedance measurement unit for controlling the multi-channel impedance measurement unit; The frequency domain analysis unit is configured to be connected to the multi-channel impedance measurement unit and the photoplethysmography pulse wave acquisition unit respectively. The frequency domain analysis unit is suitable for separating blood perfusion signals by frequency domain analysis. An image reconstruction unit is configured to be connected to the frequency domain analysis unit, the image reconstruction unit being adapted to generate a blood perfusion image based on the blood perfusion signal.

6. The blood perfusion electrical impedance imaging system according to claim 5, wherein the array sensor is composed of a plurality of electrodes arranged in a row.

7. The blood perfusion electrical impedance imaging system according to claim 5, further comprising: A signal conditioning unit is configured to be connected between the photoplethysmography (PPG) acquisition unit and the frequency domain analysis unit, and the signal conditioning unit is adapted to filter out noise in the PPG signal.

8. The blood perfusion electrical impedance imaging system according to claim 5, wherein the frequency domain analysis unit is composed of a matched filter.

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