Electromagnetic imaging method, device and equipment based on composite excitation magnetic field and medium

Abstract

The invention discloses an electromagnetic imaging method, device and equipment based on a composite excitation magnetic field and a medium, and relates to the technical field of biomedical engineering.The method comprises the steps that under work of a uniform magnetic field and a symmetrical zero magnetic field generated through alternate excitation, signal collection is conducted on a measuring electrode on a vascular tissue phantom, and a periodic initial voltage signal is obtained; preprocessing the initial voltage signal to obtain a voltage digital signal; according to the voltage digital signal, the upper computer is used for analyzing the corresponding relation between the voltage digital signal and the blood flow in the blood vessel tissue phantom, and blood vessel image representation of the blood vessel tissue phantom is obtained. The method is suitable for blood flow measurement and imaging scenes of the magnetoelectric effect of arterial blood flow.

Description

Technical Field

[0001] The present application relates to the technical field of biomedical engineering, and particularly relates to an electromagnetic imaging method, device, equipment and medium based on a composite excitation magnetic field. Background Art

[0002] Blood flow measurement and imaging technology based on the magnetoelectric effect of arterial blood flow can be applied to the early diagnosis and prevention of human arterial stenosis. The existing blood flow measurement and imaging technology based on the magnetoelectric effect of arterial blood flow uses a relatively large excitation device to generate a constant and uniform magnetic field in the area to be measured, obtains the induced potential difference on the human skin surface through measurement electrodes, and then combines corresponding image reconstruction algorithms to perform human arterial imaging. However, the existing solution relies on a relatively large excitation device and a sufficient number of measurement electrodes. Because a sufficiently large excitation device is required to generate the required uniform magnetic field, there is a problem of high cost. And a sufficient number of measurement electrodes are for ensuring a sufficient amount of measurement data to avoid low imaging resolution caused by insufficient data volume, which is not conducive to imaging. Summary of the Invention

[0003] In view of this, the present application provides an electromagnetic imaging method, device, equipment and medium based on a composite excitation magnetic field, mainly aiming to solve the technical problems of high cost existing in the prior art due to relying on a large excitation device and a sufficient number of measurement electrodes, and low imaging resolution caused by a small number of measurement electrodes in a small volume, which is even not conducive to imaging.

[0004] According to one aspect of the present application, an electromagnetic imaging method based on a composite excitation magnetic field is provided. The method includes:

[0005] Under the working conditions of an alternating excitation-generated uniform magnetic field and a symmetric zero magnetic field, signal acquisition is performed on the measurement electrodes on the blood vessel tissue phantom to obtain a periodic initial voltage signal;

[0006] Preprocess the initial voltage signal to obtain a voltage digital signal;

[0007] According to the voltage digital signal, use the host computer to analyze the corresponding relationship between the voltage digital signal and the blood flow inside the blood vessel tissue phantom to obtain the blood vessel image representation of the blood vessel tissue phantom.

[0008] According to another aspect of the present application, an electromagnetic imaging device based on a composite excitation magnetic field is provided. The device includes:

[0009] A signal control module, configured to perform signal acquisition on the measurement electrodes on the blood vessel tissue phantom under the working conditions of an alternating excitation-generated uniform magnetic field and a symmetric zero magnetic field to obtain a periodic initial voltage signal;

[0010] A signal processing module for preprocessing the initial voltage signal to obtain a voltage digital signal;

[0011] An analysis module for using a host computer to analyze the correspondence between the voltage digital signal and the blood flow inside the vascular tissue phantom according to the voltage digital signal, so as to obtain a vascular image representation of the vascular tissue phantom.

[0012] According to another aspect of the present application, there is provided a computer storage medium on which a computer program is stored, and when the program is executed by a processor, the above electromagnetic imaging method based on a composite excitation magnetic field is implemented.

[0013] According to still another aspect of the present application, there is provided a computer device, including a storage medium, a processor, and a computer program stored on the storage medium and executable on the processor. When the processor executes the program, the above electromagnetic imaging method based on a composite excitation magnetic field is implemented.

[0014] By means of the above technical solution, the electromagnetic imaging method, device, equipment and medium based on a composite excitation magnetic field provided by the present application, compared with the prior art solutions that rely on large excitation devices and a sufficient number of measurement electrodes, which have high costs, and the low imaging resolution caused by the small number of measurement electrodes in small volumes, and even are not conducive to imaging. In the present application, under the working of a uniform magnetic field generated by alternating excitation and a symmetric zero magnetic field, signal acquisition is performed on the measurement electrodes on the vascular tissue phantom to obtain a periodic initial voltage signal; the initial voltage signal is preprocessed to obtain a voltage digital signal; according to the voltage digital signal, the correspondence between the voltage digital signal and the blood flow inside the vascular tissue phantom is analyzed by using a host computer to obtain a vascular image representation of the vascular tissue phantom. It can be seen that through the control method of the composite excitation magnetic field, a uniform magnetic field generated by alternating excitation and a symmetric zero magnetic field are realized, and then based on the fusion of vascular information under the two magnetic fields, the host computer can more comprehensively and accurately reconstruct the vascular image representation of the vascular tissue phantom.

[0015] The above description is only an overview of the technical solution of the present application. In order to be able to understand the technical means of the present application more clearly, it can be implemented according to the content of the specification. And in order to make the above and other purposes, features and advantages of the present application more obvious and understandable, the specific embodiments of the present application are specifically given below. Description of the Drawings

[0016] The drawings described herein are used to provide a further understanding of the present application, and constitute a part of the present application. The schematic embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation to the present application. In the drawings:

[0017] Figure 1Shows a schematic flowchart of an electromagnetic imaging method based on a composite excitation magnetic field provided by an embodiment of the present application;

[0018] Figure 2 Shows a schematic flowchart of another electromagnetic imaging method based on a composite excitation magnetic field provided by an embodiment of the present application;

[0019] Figure 3 Shows a schematic diagram of a composite coil structure of another electromagnetic imaging method based on a composite excitation magnetic field provided by an embodiment of the present application;

[0020] Figure 4 Shows a schematic diagram of the structure of an electromagnetic imaging device based on a composite excitation magnetic field provided by an embodiment of the present application;

[0021] Figure 5 Shows a schematic diagram of the structure of another electromagnetic imaging device based on a composite excitation magnetic field provided by an embodiment of the present application. Detailed implementation manners

[0022] The present application will be described in detail below with reference to the accompanying drawings and in combination with embodiments. It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments may be combined with each other.

[0023] Aiming at the technical problems in the prior art, such as the high cost due to the dependence on large excitation devices and a sufficient number of measurement electrodes, and the low imaging resolution or even the disadvantage for imaging caused by the small number of measurement electrodes in small volumes. This embodiment provides an electromagnetic imaging method based on a composite excitation magnetic field. Through the control mode of the composite excitation magnetic field, a uniform magnetic field and a symmetric zero magnetic field generated by alternating excitation are realized. Furthermore, based on the fusion of blood vessel information under the two magnetic fields, the host computer can reconstruct a more comprehensive and accurate blood vessel image representation of the blood vessel tissue phantom. As Figure 1 shown, the above method includes the following steps:

[0024] Step 101: Under the working conditions of a uniform magnetic field and a symmetric zero magnetic field generated by alternating excitation, collect signals from the measurement electrodes on the blood vessel tissue phantom to obtain a periodic initial voltage signal.

[0025] In this embodiment, a generation and control method of a composite excitation magnetic field is proposed, that is, through an alternating excitation control method, a uniform magnetic field and a symmetric zero magnetic field are generated to realize the alternating excitation of the two magnetic fields. Specifically, the overall scanning period is set to first perform uniform magnetic field excitation and then symmetric zero magnetic field (also known as linear zero magnetic field) excitation. That is, signals are collected from the measurement electrodes on the blood vessel tissue phantom, and the periodic initial voltage signal obtained based on the time series is composed of a first initial voltage signal generated based on the uniform magnetic field and a second initial voltage signal generated based on the symmetric zero magnetic field.

[0026] Step 102: Preprocess the initial voltage signal to obtain a voltage digital signal.

[0027] In this embodiment, the electromagnetic imaging device based on a composite excitation magnetic field includes a single-chip microcomputer, a detection module, a signal control module, a signal processing module, and an analysis module. The detection module includes a peristaltic pump and a measuring device. The signal control module includes an excitation current source and a DA module. The signal control module is configured to collect signals from the measurement electrodes on the blood vessel tissue phantom under the working conditions of a uniform magnetic field generated by alternating excitation and a symmetric zero magnetic field, so as to obtain a periodic initial voltage signal. Further, the signal processing module includes a signal processing circuit and an AD module, which are used to preprocess the initial voltage signal to obtain a voltage digital signal for the host computer to read. Among them, the host computer includes an analysis module, and the host computer is used to write the single-chip microcomputer program.

[0028] Step 103: According to the voltage digital signal, use the host computer to analyze the corresponding relationship between the voltage digital signal and the blood flow inside the blood vessel tissue phantom, so as to obtain the blood vessel image representation of the blood vessel tissue phantom.

[0029] In this embodiment, the voltage digital signal is a set of periodic voltage digital signals. Each set of periodic voltage digital signals includes a first voltage digital signal generated based on a uniform magnetic field and a second voltage digital signal generated based on a symmetric zero magnetic field. The first voltage digital signal corresponds to a first initial voltage signal, and the first initial voltage signal carries blood vessel characterization information such as blood flow velocity. Therefore, based on the blood flow magnetoelectric effect, the blood flow velocity can be extracted. The second voltage digital signal corresponds to a second initial voltage signal, and the second initial voltage signal carries blood vessel characterization information such as position vector and time. Therefore, the central position and radius of the blood vessels in the blood vessel tissue phantom can be extracted. Furthermore, based on the fusion of the blood vessel characterization information under the two magnetic fields, the host computer can reconstruct the blood vessel image representation of the blood vessel tissue phantom more comprehensively and accurately.

[0030] For this embodiment, according to the above solution, under the working of the uniform magnetic field generated by alternating excitation and the symmetric zero magnetic field, signal acquisition is performed on the measurement electrodes on the blood vessel tissue phantom to obtain a periodic initial voltage signal; the initial voltage signal is preprocessed to obtain a voltage digital signal; according to the voltage digital signal, the host computer is used to analyze the corresponding relationship between the voltage digital signal and the blood flow inside the blood vessel tissue phantom to obtain the blood vessel image representation of the blood vessel tissue phantom. Compared with the prior art, which relies on large excitation devices and a sufficient number of measurement electrodes, resulting in high costs, and the low imaging resolution caused by the small number of measurement electrodes in small volumes, and even being disadvantageous for imaging, this embodiment realizes the uniform magnetic field generated by alternating excitation and the symmetric zero magnetic field through the control method of the composite excitation magnetic field, and then based on the fusion of blood vessel information under the two magnetic fields, enables the host computer to more comprehensively and accurately reconstruct the blood vessel image representation of the blood vessel tissue phantom.

[0031] Further, as a refinement and extension of the specific implementation manner of the above embodiment, in order to completely illustrate the specific implementation process of this embodiment, another electromagnetic imaging method based on a composite excitation magnetic field is provided. According to Faraday's law of electromagnetic induction, when a conductor passes through a magnetic field at a certain speed, an induced electromotive force perpendicular to the magnetic field direction will be generated at both ends of the conductor. The magnitude of the induced electromotive force has a linear relationship with the product of the magnetic field strength and the conductor speed. For human blood flow, which combines fluidity and conductivity, when it flows through a magnetic field, a detectable induced electromotive force will be generated on the surface of the human skin. When the blood flow velocity is constant, the greater the magnetic field passed through, the greater the induced electromotive force; when the magnetic field is constant and the blood flow velocity changes with time, the induced electromotive force also changes accordingly. This is the magnetoelectric effect of blood flow. Therefore, this embodiment can solve the technical problems in traditional measurement and imaging methods, such as the measurement and imaging accuracy depending on the number of electrodes and the slow imaging speed. This embodiment can, based on the constructed composite excitation magnetic field and its control method, and based on the fusion of blood vessel information under the two magnetic fields, enable the host computer to more comprehensively and accurately reconstruct the blood vessel image representation of the blood vessel tissue phantom. As Figure 2 shown, the arterial electromagnetic imaging method based on composite excitation magnetic field control includes:

[0032] Step 201: Generate a uniform magnetic field by exciting the Helmholtz coil in the excitation composite coil.

[0033] Step 202: After the gradient coil in the composite coil is energized to generate a gradient magnetic field, a driving magnetic field is generated by exciting the Helmholtz coil in the excitation composite coil to form a symmetric zero magnetic field.

[0034] In implementation, a composite coil is set. For a uniform magnetic field, a pair of Helmholtz coils is used to generate a uniform magnetic field. The Helmholtz coils are composed of two identical circular coils. The two circular coils are placed parallel to each other and separated by a certain distance, which is equal to the radius of the coil. When the current directions through the two circular coils are the same and the magnitudes are equal, a very nearly uniform magnetic field can be generated in the space between the two circular coils, especially in the region near the center.

[0035] For a symmetric zero magnetic field, it is composed of gradient coils and drive coils. The gradient coils are composed of two pairs of rectangular coils with parallel central axes. Among them, the same direct current is passed through the coaxial gradient coils respectively, and the direct currents with the same magnitude but opposite directions are passed through the non-coaxial gradient coils. Due to the superposition of the symmetric magnetic fields, a linear region with an approximate magnetic field intensity of 0 will be generated in the x-axis direction (y = z = 0), that is, the zero magnetic field line; the drive magnetic field is composed of a pair of Helmholtz coils, and the currents passing through the pair of Helmholtz coils are equal in magnitude and the same in direction to ensure the generation of a uniform magnetic field in the central region. It can be seen that by magnetic field superposition, the linear zero magnetic field FFL is periodically moved along the y-axis direction to realize the zero magnetic field line scanning. If it is necessary to realize the magnetic field and scanning in other directions, only a coil group needs to be added in the corresponding direction.

[0036] Therefore, for the composite excitation magnetic field, the composite coil structure is as Figure 3 shown. A control method is proposed to realize the alternating excitation of the two magnetic fields. Specifically, the overall scanning period is set to first perform uniform magnetic field excitation and then perform linear zero magnetic field (symmetric zero magnetic field, variable magnetic field) excitation; when working under the uniform magnetic field, a direct current is passed through the Helmholtz coils through the excitation circuit to generate a uniform magnetic field. When working under the linear zero magnetic field, the single-chip microcomputer is used to control the DC regulated power supply to supply power to the gradient coils to generate a gradient magnetic field. After the excitation circuit generates an alternating current, it is passed through the drive coils (a pair of Helmholtz coils) to realize the zero magnetic field line scanning. Then, by collecting the induced voltage signal of the magnetic field, a voltage sampling signal for a complete period, that is, the initial voltage signal, is obtained, and through continuous alternating excitation, multiple groups of periodic initial voltage signals are obtained.

[0037] Step 203: Use the single-chip microcomputer to perform timing control on the multiplexer and collect signals from the measurement electrodes connected to the multiplexer to obtain periodic initial voltage signals.

[0038] In implementation, the measurement electrodes on the vascular tissue phantom are connected to the multiplexer. The measurement electrodes include two groups of measurement electrodes, and each group of measurement electrodes includes at least two pairs of measurement electrodes. The measurement electrodes in each group are distributed orthogonally and respectively wind around the vascular tissue phantom for one week.

[0039] In implementation, the detection module in the electromagnetic imaging device based on the composite excitation magnetic field includes a peristaltic pump and a measuring device. The measuring device mainly includes a composite coil (gradient electromagnetic coil and drive electromagnetic coil), a vascular tissue phantom, and measuring electrodes (electrode array). The gradient electromagnetic coil is wound with enameled copper wire, and the drive electromagnetic coil is wound with Litz wire. Among them, since Litz wire is composed of multiple strands of copper wire and is prone to deformation, a corresponding wire frame is designed as a support structure. And in order to ensure its relative position fixation in space, a system support structure is designed. The design process of each structure is completed by Solid works and prepared by 3D printing.

[0040] According to the requirements of the actual application scenario, the vascular tissue phantom is intended to be composed of gelatin, and the conductivity parameter is adjusted by sodium chloride solution; the vascular tissue phantom uses a fluid hose, and the hose is made of a material similar to the arterial mechanical parameters, and hoses with uneven thickness are used to simulate the real arterial area. And the peristaltic pump is regulated to generate a flow velocity change with a pulsating period in the hose (vascular tissue phantom) to simulate blood flow. In addition, four pairs (a total of eight) of electrodes are arranged on the periphery of the vascular tissue phantom, divided into two groups, and each group is orthogonally distributed around the phantom for one week to ensure high-precision and multi-point synchronous monitoring of the hydrodynamic and biophysical properties in the vascular tissue phantom. Among them, each pair of electrodes is responsible for a measurement channel, accurately collecting the induced voltage signal response caused by the internal structure change of the phantom, so as to realize the non-invasive evaluation of the internal fluid properties of the phantom, providing an effective tool for subsequent research, which not only helps to improve the spatial resolution of data acquisition, but also can enhance the anti-interference ability and ensure the reliability of experimental results.

[0041] In implementation, the initial voltage signal includes a first initial voltage signal generated based on a uniform magnetic field and a second initial voltage signal generated based on a symmetric zero magnetic field. The first initial voltage signal is used to reconstruct the blood flow velocity of the vascular tissue phantom based on the blood flow magnetoelectric effect; the second initial voltage signal is used to reconstruct the central position and radius of the blood vessels in the vascular tissue phantom.

[0042] In implementation, different excitation magnetic fields will make the generated voltage signals carry different vascular information. The first initial voltage signal generated based on a uniform magnetic field carries vascular characterization information such as blood flow velocity, and the second initial voltage signal generated based on a symmetric zero magnetic field carries vascular characterization information such as position vector and time. By fusing (stitching) the vascular characterization information under the two excitation magnetic fields, a voltage signal sequence based on time is obtained, so that the host computer can more accurately and comprehensively realize the reconstruction of the vascular tissue phantom and obtain a higher-quality vascular imaging.

[0043] Furthermore, the vascular characterization information carried by the uniform magnetic field and the linear zero magnetic field (symmetric zero magnetic field) is specifically:

[0044] For a uniform magnetic field, assuming that the blood conductivity distribution is uniform, the Poisson equation for the relationship between the scalar electric potential and the blood flow vector velocity and the vector magnetic field value can be derived. Therefore, the interaction between the blood flow velocity and the externally applied magnetic field will form an induced electric potential field within a certain range of the vascular tissue phantom. Using appropriate boundary conditions, the distribution of the induced electric potential field generated by the blood flow velocity under a uniform magnetic field can be solved. Therefore, the induced voltage signal caused by the blood flow velocity can be obtained by means of measurement electrodes, detection coils, sensors, etc. placed on the surface of the vascular tissue phantom (including the arm phantom containing the vascular tissue phantom), and can be used to extract vascular characterization information such as blood flow velocity.

[0045] The Poisson equation obtained from the above derivation process is:

[0046]

[0047] Among them, is the Laplace operator, which is used to describe the second-order partial derivatives in space. u is the induced voltage signal, v is the blood flow velocity, B is the excitation magnetic field. The reciprocity theorem can transform the complex field solution problem into a relatively simpler field for analysis and processing. Therefore, based on the reciprocity theorem, the boundary voltage integral equation is further derived from formula (1) as shown in formula (2):

[0048] Δu = ∫∫ s v(x,y)·(J A (x,y)×B)dxdy (2)

[0049] If the entire measured plane s of the vascular tissue phantom is divided into n small imaging units, then formula (2) is discretized and then transformed into a non-homogeneous linear equation system applicable to multiple pairs of measurement electrodes, as shown in formula (3):

[0050] U = [J A ×B·S]v = Wv (3)

[0051] Among them, W is the weight matrix, which represents the contribution of the flow points at different positions to the voltage signal generated by the blood flow magnetoelectric effect. Therefore, the blood flow velocity reconstruction equation based on the blood flow magnetoelectric effect is as shown in formula (4):

[0052] v = W -1 U (4)

[0053] For a linear zero magnetic field (symmetric zero magnetic field, variable magnetic field), for a two-dimensional tomography plane model, according to the vector operation rules, the relationship between the induced voltage signal and the blood flow velocity and the magnetic field is as shown in formula (5):

[0054] Δu = ∫∫ S v×(Jr × B) dS (5)

[0055] Where Δu is the measured induced voltage signal, v is the blood flow velocity, J r is the reciprocal current density, and B is the excitation magnetic field.

[0056] The linear zero - magnetic - field FFL is a magnetic field with a zero - magnetic - field region where the region with zero or approximately zero magnetic field is linear. As time changes, the position of the FFL also changes regularly, thereby scanning the entire measured area. When the magnetic field is a linear zero - magnetic - field, the induced voltage signal will be related to the position vector r and time t, and formula (5) is converted to:[[]]

[0057] u(r,t) = ∫ V J r (r)·(v(r) × B(r,t)) dV (6)

[0058] Therefore, reconstructing the center position and radius of the blood vessel based on the induced voltage signal can be regarded as a process of converting a time signal to a space signal (space - time transformation). Specifically:[[]]

[0059] First, when the time series is t = [t1, t2, …, t N , the sequence of induced voltage signals obtained is u = [u1, u2, …, u N , where N is the number of scanning time series. When the scanning path (the range of the measured area corresponding to the blood - vessel tissue phantom) w, the scanning period T S , the FFL scanning distance step δ SR , and the FFL scanning time step δ TR are determined, the calculation formula for the number of scanning time series is shown in (7):[[]]

[0060]

[0061] Based on the principle of reconstructing the blood - vessel characterization information of the linear zero - magnetic - field, when the FFL scans to the blood - vessel area, the induced voltage signal will show a situation where the value is close to zero. Find the moment t0 corresponding to the zero potential, and calculate the FFL scanning distance from the initial moment to t0 according to this moment, as shown in formula (8):[[]]

[0062]

[0063] Further determine the blood - vessel center position coordinate Co, as shown in formula (9):[[]]

[0064]

[0065] According to Equation (6), the magnitude of the induced voltage signal is related to the volume of the blood flow region. Therefore, the boundary of the arterial blood flow region is determined by establishing a numerical relationship between the voltage amplitude and the arterial radius.

[0066] The voltage signal is differentiated with respect to time as shown in Equation (10):

[0067]

[0068] The approximation of Equation (10) is carried out under the following conditions: ① The blood flow velocity is approximated as a constant value because the zero magnetic field line scanning period is much smaller than the blood flow velocity change period; ② Since the inner diameter of the blood vessel is very small, the reciprocating current density and magnetic field change little in the radial direction. Therefore, the parameter values in the radial direction are uniformly replaced by the parameter values at the center line. At the same time, for the parameter values of each point in the axial direction of the blood vessel, the average value of the axial parameters is used instead; ③ The change of the magnetic flux density with time at the same position is approximated as a linear change, and the derivative of the magnetic flux density with respect to time at the same position is set as a constant. After the above parameter approximation is completed, according to Equation (10), it can be seen that the derivative of the magnetic flux density with respect to time at the same position (referred to as the slope of the voltage signal) is mainly related to the size of the blood vessel radius r. The larger the radius, the larger the amplitude of the voltage signal. Therefore, the blood vessel radius r can be calculated by this derivative.

[0069] Furthermore, according to the coil current that drives the FFL movement during the construction of the magnetic field, the voltage u(Co, t s ) at the initial moment t s of the scan and the amplitude of the voltage u(Co, t e ) at the end moment t e of the scan, usually one is large and the other is small and the polarities are opposite. |u(Co, t s ) - u(Co, t e )| is the slope of the voltage signal, and its linear relationship with the radius r is shown in Equation (11):

[0070] |u(Co, t s ) - u(Co, t e )| = K se (Co)r 2 (11)

[0071] where the proportionality coefficient K se (Co) is shown in Equation (12):

[0072] K se (Co) = |K(Co, t s ) - K(Co, t e )| = πLvJ(Co)|B(Co, t s ) - B(Co, t e )| (12)

[0073] Calculate the proportionality coefficient K based on the prior information of the detection module (measurement electrode, vascular tissue phantom). se (Co), and then combine formula (7) and the voltage signal amplitude to approximately calculate the vascular radius r, as shown in formula (13):

[0074]

[0075] After determining the vascular center position coordinate Co and the vascular radius r, the boundary coordinates Co1 and Co2 of the blood vessel are as shown in formula (14):

[0076]

[0077] According to the requirements of the actual application scenario, in order to realize the fusion of vascular characterization information under two magnetic fields, the generation method of the composite excitation magnetic field is as follows: Select a single-chip microcomputer as the control center of the entire device. The single-chip microcomputer controls the excitation current source through the DA module (digital-to-analog converter), and uses a multiplexer to control the acquisition sequence of the voltage signals of each pair of measurement electrodes. The DA module (digital-to-analog converter) converts the digital signal output by the single-chip microcomputer into an analog signal for controlling the excitation current source; the excitation current source generates a corresponding excitation current according to the analog signal output by the DA module for driving the power supply of the coil; the multiplexer performs multiplexing on the voltage signals of the detection module so that the single-chip microcomputer can select and receive the voltage signals of specific channels.

[0078] Step 204: Preprocess the initial voltage signal to obtain a voltage digital signal.

[0079] To illustrate the specific implementation manner of step 204, as a preferred embodiment, step 204 includes: performing differential amplification processing on the initial voltage signal to obtain the induced potential difference of the measurement electrode; performing noise filtering processing on the induced potential difference to obtain an analog voltage signal; performing analog-to-digital conversion processing on the analog voltage signal to obtain a voltage digital signal; wherein, the noise filtering processing includes system noise filtering processing and external noise filtering processing.

[0080] In implementation, after the induced voltage signal (initial voltage signal) is generated, the signal processing module is used for preprocessing to make the data sent to the host computer (including the parsing module) for inversion more accurate. Specifically, two multiplexers are respectively connected to 4 pairs of measurement electrodes. Through the time series control of the single-chip microcomputer, the induced voltage signal of a pair of measurement electrodes is collected each time. The collected induced voltage signal is subjected to differential amplification processing (the subsequent required data is the induced potential difference between the two electrodes). The processed signal includes system noise, external noise, etc. Therefore, a low-pass filter is designed to filter high-frequency noise interference, and then a notch filter is used to filter power frequency interference. Since the processed signal is still an analog voltage signal, it is converted into a digital voltage signal through the AD conversion module, and the data transmission is completed through the communication module between the AD analog module and the host computer, so that the parsing module in the host computer can perform subsequent processing.

[0081] According to the requirements of the actual application scenario, the signal processing circuit in the signal processing module preprocesses the voltage signal output by the multiplexer to obtain a denoised voltage signal; the AD module (analog-to-digital converter) in the signal processing module converts the analog signal output by the signal processing circuit into a digital signal for the host computer to read.

[0082] Step 205: Use the convolutional neural network in the host computer to perform non-linear mapping and feature extraction on the voltage digital signal to obtain the corresponding relationship between the voltage digital signal and the blood flow inside the vascular tissue phantom.

[0083] In this embodiment and other possible embodiments, the corresponding relationship between the voltage digital signal and the blood flow inside the vascular tissue phantom is configured as the vascular reconstruction auxiliary model (auxiliary model) of the vascular tissue phantom or the vascular reconstruction improved auxiliary model (improved auxiliary model) of the vascular tissue phantom.

[0084] In this embodiment and other possible embodiments, a source domain data set is generated using the electrical impedance imaging model, and the first boundary voltage data corresponding to the target domain data set is generated using the electromagnetic imaging model; the preset auxiliary model is trained according to the first boundary voltage data corresponding to the source domain data set to obtain an improved auxiliary model; the improved auxiliary model is subjected to adaptation layer training and full network fine-tuning using the second boundary voltage data corresponding to the target domain data set to obtain an imaging optimization model.

[0085] In this embodiment and other possible embodiments, the electrical impedance tomography model includes: a plurality of excitation coils in a circular ring shape; a target area is formed on one side of the plurality of excitation coils. The method for using measurement electrodes to collect signals from a target object with a preset shape in the target area to obtain first boundary voltage data corresponding to a periodic initial voltage signal includes: performing finite element division on the target area to obtain a preset number of finite element divided grids; under the operation of a uniform magnetic field generated by alternating excitation and a symmetric zero magnetic field, using measurement electrodes to collect signals from a target object with a preset shape in the target area to obtain first boundary voltage data corresponding to a periodic initial voltage signal. Among them, the measurement electrodes include two groups of measurement electrodes, each group of measurement electrodes includes at least two pairs of measurement electrodes, and the two groups of measurement electrodes are distributed orthogonally to each other and respectively surround the outside of the target object with the preset shape for one week. Among them, the preset number can be configured as 576.

[0086] Since the target object with a preset shape is a self-set test object (virtual test object), the first boundary voltage data includes: a first initial virtual voltage signal corresponding to the target object with a preset shape in the target area generated by the uniform magnetic field and a second initial virtual voltage signal corresponding to the target object with a preset shape in the target area generated by the symmetric zero magnetic field.

[0087] Specifically, the method for obtaining first boundary voltage data by applying a constant excitation current and measuring the boundary voltage includes: performing simulation of the forward imaging problem based on the finite element target object and the adjacent excitation modes under a constant excitation current to determine the corresponding first boundary voltage data.

[0088] Among them, the setting method of the specific source domain data set is as follows: First, set the number, position, size, and shape of the target object (test object or virtual test object). Among them, the number of target objects ranges from 1 to 3, the position and size of the target object are randomly determined within the target area, and the target shape (shape) of the target object includes one or several of a circle, a triangle, and a square. Furthermore, under the operation of a uniform magnetic field generated by alternating excitation and a symmetric zero magnetic field, using measurement electrodes to collect signals from a target object with a preset shape in the target area to obtain a first initial virtual voltage signal and a second initial virtual voltage signal corresponding to the first boundary voltage data corresponding to the periodic initial voltage signal.

[0089] Specifically, the target shapes (shapes) of the marked objects include circles, triangles, and squares, and the generation methods are as follows. (1) Target object of a circle: First, determine the center position of the target object of the circle in the target area as (xi, yi). In addition, after determining the center position, adding the radius size should ensure that it does not exceed the circular target area, that is, it is always inside the field area. The radius of the circle is selected between 0.25, 0.3, and 0.4, as long as the distance from the center to the origin plus the radius of the generated circle does not exceed 1. (2) Target object of a square: First, determine the center of the square of the target object of the square in the target area. After determining the center of the square, each side of the square target is also within the circular background field area, and the square can be rotated at a certain angle. In this invention, only the cases of non-rotation and rotation by 45 degrees are selected. The side length of the square is 0.4 or 0.55. (3) Target object of a triangle: The triangle targets are all equilateral triangles. The generation method is similar to that of the square. First, determine the center of the target object of the triangle in the target area, and then judge whether each vertex is within the circular field area. The rotation angle of the triangle is more than that of the square, with non-rotation and rotation angles of 30, 45, and 60 degrees, but the side length of the triangle target is constantly 0.6. (4) Target object of a mixed shape: The mixed target is generated based on the above three single-graphic targets (target object of a circle, target object of a square, target object of a triangle). Select non-overlapping images (images corresponding to the target object of a circle, target object of a square, target object of a triangle) for finite element target design, and try to avoid selecting cases where the radius or side length is too large to avoid target overlap. The radius of the circle is selected as 0.25, the side length of the square is selected as 0.4, and the side length of the triangle is selected as 0.6.

[0090] Based on the finite element and adjacent excitation mode, use the EIDORS (Electrical Impedance Tomography and Diffuse Optical Tomography Reconstruction Software, an open-source software for electrical impedance imaging) software package in MATLAB to generate the source domain EIT dataset. The excitation electrodes are placed adjacent to each other, and the potential differences between adjacent electrode pairs except the excitation electrodes are measured. As Figure 2 shown, electrodes 1 and 2 are used as excitation, and the potential differences of the remaining electrodes are measured (3-4, 4-5, 5-6,..., 15-16). One measurement with this configuration can collect 16×(16 - 3) = 208 first boundary voltage data, which is not only rich in bioelectrical information but also has good sensitivity.

[0091] Specifically, the electrical impedance tomography model includes: a plurality of electrode models with preset shapes. Among them, the background conductivity of the test object and the field area of the test object (target object) are set; under the background conductivity and field area of the test object, by equidistantly placing a plurality of electrodes on the surface of the test object with a preset shape, applying a constant excitation current and measuring the boundary voltage to obtain the first boundary voltage data corresponding to the bioelectrical information.

[0092] More specifically, the electrical impedance tomography model is a 16 - electrode circular model. By equidistantly placing 16 electrodes on the surface of a preset circular test object, applying a constant excitation current and measuring the boundary voltage to obtain bioelectrical information. Among them, a point - electrode circular finite - element model with 576 meshes including 16 electrodes is selected, the radius of the circular field area is set to 1, and the background conductivity is 1 S / m.

[0093] In this embodiment and other possible embodiments, before using the second boundary voltage data corresponding to the target - domain data set to perform adaptation - layer training and full - network fine - tuning on the improved auxiliary model to obtain an imaging optimization model, signal acquisition is performed on the measurement electrodes on the vascular tissue phantom under the uniform magnetic field generated by alternating excitation and the symmetric zero - magnetic field, and the periodic initial voltage signal obtained is configured as the second boundary voltage data corresponding to the target - domain data set; wherein, the second boundary voltage data includes: a first initial voltage signal corresponding to the vascular tissue phantom in the target area based on the uniform magnetic field and a second initial voltage signal corresponding to the vascular tissue phantom in the target area based on the symmetric zero - magnetic field.

[0094] In this embodiment and other possible embodiments, the method of training a preset auxiliary model according to the first boundary voltage data corresponding to the source - domain data set to obtain an improved auxiliary model includes: obtaining the internal blood flow corresponding to the test object (target object) in the source - domain data set (the first training label when the auxiliary model is trained); training the auxiliary model based on the first boundary voltage data corresponding to the source - domain data set and its corresponding internal blood flow to obtain an improved auxiliary model.

[0095] In this embodiment and other possible embodiments, the preset auxiliary model includes: an input layer, a first convolutional layer, a second convolutional layer, a third convolutional layer, a fourth convolutional layer, a first pooling layer, a second pooling layer, a deconvolution layer (upsampling layer), and an output layer; the input layer deforms the processed first boundary voltage data of the input to obtain a first matrix; the first convolutional layer uses multiple convolutional kernels of a first set size to perform feature extraction on the first matrix and outputs a feature vector of a first dimension; the first pooling layer uses a maximum pooling window of a second set size and a set pooling stride to perform dimensionality reduction and important feature extraction on the feature vector of the first dimension to obtain a feature vector of a second dimension; the second convolutional layer increases the number of output channels of the feature vector of the second dimension to obtain a feature vector of a third dimension; the third convolutional layer and the fourth convolutional layer sequentially perform feature extraction on the feature vector of the third dimension to obtain a target feature vector; the second pooling layer uses a maximum pooling window of a third set size and a set pooling stride to perform dimensionality reduction processing on the target feature vector to obtain a dimensionality-reduced target feature vector; the deconvolution layer (upsampling layer) performs one or more deconvolutions or upsamplings according to the dimensionality-reduced target feature vector to obtain a corresponding processed internal blood flow feature map; the output layer performs convolutional processing on the output processed internal blood flow feature map to obtain a corresponding internal blood flow image.

[0096] In this embodiment and other possible embodiments, before training the preset auxiliary model according to the first boundary voltage data corresponding to the source domain dataset, it further includes: normalizing and / or standardizing the first boundary voltage data corresponding to the source domain dataset.

[0097] In this embodiment and other possible embodiments, before performing adaptation layer training and full network fine-tuning on the improved auxiliary model using the second boundary voltage data corresponding to the target domain dataset, it further includes: normalizing and / or standardizing the second boundary voltage data corresponding to the target domain dataset.

[0098] In this embodiment and other possible embodiments, the method of using the second boundary voltage data corresponding to the target domain dataset to perform adaptation layer training and full network fine-tuning on the improved auxiliary model to obtain an imaging optimization model includes: freezing the model parameters of the improved auxiliary model and adding an adaptation layer to the improved auxiliary model; using a first number of target domain data selected from the target domain dataset to train the adaptation layer to obtain a trained adaptation layer; selecting a second number of labeled target domain data from the target domain dataset to perform full network fine-tuning on the trained auxiliary model and the adaptation layer to obtain the imaging optimization model.

[0099] Step 206: Perform visual reconstruction on the fluid and tissue characteristics in the vascular tissue phantom according to the corresponding relationship to obtain a vascular image representation of the vascular tissue phantom.

[0100] In implementation, the host computer includes a convolutional neural network. The voltage digital signal is a set of periodic voltage digital signals. Each set of periodic voltage digital signals includes a first voltage digital signal generated based on a uniform magnetic field and a second voltage digital signal generated based on a symmetric zero magnetic field. The host computer includes an analysis module, specifically a pre-trained convolutional neural network, which performs complex non-linear mapping and feature extraction on the received digital signal, and analyzes the relationship between the voltage signal and the internal structure of the vascular tissue phantom based on the convolutional neural network architecture. Among them, the convolutional neural network uses its learned recognition ability to convert the digital signal of the induced voltage signal into a corresponding image representation, thereby realizing the visual reconstruction of the fluid and tissue characteristics in the vascular tissue phantom. This reconstruction process can not only provide high-resolution imaging results, but also reveal fine structures and dynamic changes that are difficult to capture by traditional imaging techniques, providing strong data support for clinical diagnosis and scientific research.

[0101] By applying the technical solution of this embodiment, under the working of the uniform magnetic field and the symmetric zero magnetic field generated by alternating excitation, signal acquisition is performed on the measurement electrodes on the vascular tissue phantom to obtain a periodic initial voltage signal; the initial voltage signal is preprocessed to obtain a voltage digital signal; according to the voltage digital signal, the host computer analyzes the corresponding relationship between the voltage digital signal and the internal blood flow of the vascular tissue phantom to obtain a vascular image representation of the vascular tissue phantom. Compared with the prior art solutions that rely on large excitation devices and a sufficient number of measurement electrodes, which have high costs, and the low imaging resolution caused by the small number of measurement electrodes in small volumes, and even are not conducive to imaging, this embodiment realizes the uniform magnetic field and the symmetric zero magnetic field generated by alternating excitation through the control method of the composite excitation magnetic field, and then based on the fusion of vascular information under the two magnetic fields, enables the host computer to more comprehensively and accurately reconstruct the vascular image representation of the vascular tissue phantom.

[0102] Further, as Figure 1 a specific implementation of the method, an electromagnetic imaging device based on a composite excitation magnetic field is provided in an embodiment of the present application, as Figure 4 shown. The device includes: a signal control module 42, a signal processing module 43, and an analysis module 44.

[0103] The signal control module 42 is configured to perform signal acquisition on the measurement electrodes on the vascular tissue phantom under the working of the uniform magnetic field and the symmetric zero magnetic field generated by alternating excitation to obtain a periodic initial voltage signal.

[0104] The signal processing module 43 is configured to preprocess the initial voltage signal to obtain a voltage digital signal.

[0105] The parsing module 44 is configured to utilize a host computer to parse the correspondence between the voltage digital signal and the blood flow inside the vascular tissue phantom according to the voltage digital signal, so as to obtain the vascular image representation of the vascular tissue phantom.

[0106] In a specific application scenario, such as Figure 5 As shown, the device further includes: a detection module 41.

[0107] The detection module 41 is configured to set a composite coil and generate a uniform magnetic field and a symmetric zero magnetic field by means of alternating excitation. Specifically, it is configured to generate a uniform magnetic field by exciting the Helmholtz coil in the composite coil; and, after the gradient coil in the composite coil is energized to generate a gradient magnetic field, a driving magnetic field is generated by exciting the Helmholtz coil in the composite coil to form a symmetric zero magnetic field.

[0108] In a specific application scenario, the measurement electrodes on the vascular tissue phantom are connected to a multiplexer, and the signal control module 42 includes: an acquisition sub-module 421.

[0109] The acquisition sub-module 421 is configured to use a single-chip microcomputer to perform timing control on the multiplexer and collect signals from the measurement electrodes connected to the multiplexer to obtain a periodic initial voltage signal; wherein, the initial voltage signal includes a first initial voltage signal generated based on the uniform magnetic field and a second initial voltage signal generated based on the symmetric zero magnetic field.

[0110] In a specific application scenario, the first initial voltage signal is used to reconstruct the blood flow velocity of the vascular tissue phantom based on the blood flow magnetoelectric effect; the second initial voltage signal is used to reconstruct the central position and radius of the blood vessels in the vascular tissue phantom.

[0111] In a specific application scenario, the measurement electrodes include two groups of measurement electrodes, and each group of measurement electrodes includes at least two pairs of measurement electrodes. The two groups of measurement electrodes are orthogonally distributed around the vascular tissue phantom respectively.

[0112] In a specific application scenario, the signal processing module 43 includes: a first processing sub-module 431, a second processing sub-module 432, and a third processing sub-module 433.

[0113] The first processing sub-module 431 is configured to perform differential amplification processing on the initial voltage signal to obtain the induced potential difference of the measurement electrodes.

[0114] The second processing sub-module 432 is configured to perform noise filtering processing on the induced potential difference to obtain an analog voltage signal, where the noise filtering processing includes system noise filtering processing and external noise filtering processing.

[0115] The third processing sub-module 433 is configured to perform analog-to-digital conversion processing on the analog voltage signal to obtain a voltage digital signal.

[0116] In a specific application scenario, the host computer includes a convolutional neural network, the parsing module 44 is a convolutional neural network, and the parsing module 44 includes: an extraction sub-module 441 and a reconstruction sub-module 442.

[0117] The extraction sub-module 441 is configured to perform non-linear mapping and feature extraction on the voltage digital signal by using the convolutional neural network in the host computer to obtain the correspondence between the voltage digital signal and the blood flow inside the vascular tissue phantom; where the voltage digital signal is multiple groups of periodic voltage digital signals, and each group of periodic voltage digital signals includes a first voltage digital signal generated based on a uniform magnetic field and a second voltage digital signal generated based on a symmetric zero magnetic field.

[0118] The reconstruction sub-module 442 is configured to perform visual reconstruction on the fluid and tissue characteristics in the vascular tissue phantom according to the correspondence to obtain a vascular image representation of the vascular tissue phantom.

[0119] It should be noted that for other corresponding descriptions of each functional unit involved in the electromagnetic imaging device based on a composite excitation magnetic field provided in the embodiments of the present application, reference can be made to Figure 1 and Figure 2 the corresponding descriptions therein, which will not be elaborated here.

[0120] Based on the above as Figure 1 and Figure 2 shown in the method, correspondingly, the embodiments of the present application further provide a computer storage medium, on which a computer program is stored, and when the program is executed by a processor, it implements the electromagnetic imaging method based on a composite excitation magnetic field as shown in the above Figure 1 and Figure 2 shown.

[0121] Based on such an understanding, the technical solution of the present application can be embodied in the form of a software product, which can be stored in a storage medium (which can be a CD-ROM, a USB flash drive, a mobile hard disk, etc.), and includes several instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in various implementation scenarios of the present application.

[0122] Based on the above as Figure 1 、 Figure 2 shown in the method, andFigure 4 , Figure 5 For the virtual device embodiment shown, to achieve the above object, an embodiment of the present application further provides a computer device, which may specifically be a personal computer, a server, a network device, etc. The physical device includes a storage medium and a processor; the storage medium is used to store a computer program; the processor is used to execute the computer program to implement the electromagnetic imaging method based on a composite excitation magnetic field as shown in Figure 1 and Figure 2 .

[0123] Optionally, the computer device may further include a user interface, a network interface, a camera, a radio frequency (RF) circuit, sensors, an audio circuit, a WI-FI module, etc. The user interface may include a display screen (Display), an input unit such as a keyboard (Keyboard), etc. Optionally, the user interface may further include a USB interface, a card reader interface, etc. The network interface may optionally include a standard wired interface, a wireless interface (such as a Bluetooth interface, a WI-FI interface), etc.

[0124] Those skilled in the art can understand that the structure of a computer device provided in this embodiment does not limit the physical device, and it may include more or fewer components, or combine certain components, or have different component arrangements.

[0125] The storage medium may further include an operating system and a network communication module. The operating system is a program for managing the hardware and software resources of the computer device, and supports the operation of information processing programs and other software and / or programs. The network communication module is used to implement communication between components inside the storage medium, and communication between other hardware and software in the physical device.

[0126] Through the description of the above embodiments, those skilled in the art can clearly understand that the present application can be implemented by means of software plus a necessary general hardware platform, or by hardware. By applying the technical solution of the present application, compared with the prior art that relies on a large excitation device and a sufficient number of measurement electrodes, which has a relatively high cost, and the imaging resolution is low due to the small number of measurement electrodes, and even is not conducive to imaging, this embodiment can achieve a uniform magnetic field and a symmetric zero magnetic field generated by alternating excitation through the control method of the composite excitation magnetic field, and then based on the fusion of blood vessel information under the two magnetic fields, enabling the host computer to more comprehensively and accurately reconstruct the blood vessel image representation of the blood vessel tissue phantom.

[0127] Those skilled in the art can understand that the accompanying drawings are only schematic diagrams of a preferred implementation scenario, and the modules or processes in the drawings are not necessarily essential for implementing the present application. Those skilled in the art can understand that the modules in the devices in the implementation scenario can be distributed in the devices of the implementation scenario according to the description of the implementation scenario, or can be correspondingly changed and located in one or more devices different from the present implementation scenario. The modules in the above implementation scenario can be combined into one module, or can be further split into multiple sub-modules.

[0128] The above serial numbers of the present application are only for description and do not represent the advantages or disadvantages of the implementation scenario. The above disclosure is only several specific implementation scenarios of the present application. However, the present application is not limited thereto, and any changes that can be thought of by those skilled in the art should fall within the protection scope of the present application.

Claims

1. An electromagnetic imaging method based on a composite excitation magnetic field, characterized in that: include: Under the uniform magnetic field and symmetrical zero magnetic field generated by alternating excitation, the measuring electrodes on the vascular tissue phantom are used to collect signals to obtain a periodic initial voltage signal. Preprocessing the initial voltage signal to obtain a voltage digital signal; According to the voltage digital signal, a host computer is used to analyze the corresponding relationship between the voltage digital signal and the blood flow inside the vascular tissue phantom to obtain a vascular image representation of the vascular tissue phantom.

2. The method according to claim 1, characterized in that: The step of providing a composite coil and generating a uniform magnetic field and a symmetrical zero magnetic field by alternating excitation comprises: By exciting the Helmholtz coil in the composite coil, a uniform magnetic field is generated; When the gradient coil in the composite coil is energized to generate a gradient magnetic field, a driving magnetic field is generated by exciting the Helmholtz coil in the composite coil to form a symmetrical zero magnetic field.

3. The method according to claim 1 or 2, characterized in that: The measuring electrodes on the vascular tissue phantom are connected to a multiplexer, and the step of collecting signals from the measuring electrodes on the vascular tissue phantom to obtain a periodic initial voltage signal includes: The multiplexer is controlled by a single chip microcomputer, and the measurement electrodes connected to the multiplexer are sampled to obtain periodic initial voltage signals, wherein the initial voltage signals include a first initial voltage signal generated based on a uniform magnetic field and a second initial voltage signal generated based on a symmetrical zero magnetic field.

4. The method according to claim 3, characterized in that The first initial voltage signal is used to reconstruct the blood flow velocity of the vascular tissue phantom based on the magnetoelectric effect of blood flow; the second initial voltage signal is used to reconstruct the center position and radius of the blood vessel in the vascular tissue phantom.

5. The method according to any one of claims 1 to 4, characterized in that: The measuring electrodes include two groups of measuring electrodes, each group of measuring electrodes includes at least two pairs of measuring electrodes, and the measuring electrodes in each group are orthogonally distributed and surround the vascular tissue phantom.

6. The method according to any one of claims 1 to 5, characterized in that: The step of preprocessing the initial voltage signal to obtain a voltage digital signal comprises: Performing differential amplification processing on the initial voltage signal to obtain an induced potential difference of the measuring electrode; Performing noise filtering on the induced potential difference to obtain an analog voltage signal; Performing analog-to-digital conversion on the analog voltage signal to obtain a voltage digital signal; The noise filtering process includes system noise filtering process and external noise filtering process.

7. The method according to any one of claims 1 to 6, characterized in that: The host computer includes a convolutional neural network. The step of using the host computer to analyze the corresponding relationship between the voltage digital signal and the blood flow inside the vascular tissue phantom according to the voltage digital signal to obtain a vascular image representation of the vascular tissue phantom includes: Using the convolutional neural network in the host computer to perform nonlinear mapping and feature extraction on the voltage digital signal, to obtain a corresponding relationship between the voltage digital signal and the blood flow inside the vascular tissue phantom; Visually reconstructing the fluid and tissue characteristics in the vascular tissue phantom according to the corresponding relationship to obtain a vascular image representation of the vascular tissue phantom; The voltage digital signal is a plurality of groups of periodic voltage digital signals, and each group of periodic voltage digital signals includes a first voltage digital signal generated based on a uniform magnetic field and a second voltage digital signal generated based on a symmetrical zero magnetic field.

8. An electromagnetic imaging device based on a composite excitation magnetic field, characterized in that: include: A signal control module is used to collect signals from the measuring electrodes on the vascular tissue phantom under the uniform magnetic field and symmetrical zero magnetic field generated by alternating excitation to obtain a periodic initial voltage signal; A signal processing module, used for preprocessing the initial voltage signal to obtain a voltage digital signal; The analysis module is used to analyze the corresponding relationship between the voltage digital signal and the blood flow inside the vascular tissue phantom using a host computer according to the voltage digital signal to obtain a vascular image representation of the vascular tissue phantom.

9. A computer storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the electromagnetic imaging method based on a composite excitation magnetic field as claimed in any one of claims 1 to 7 is implemented.

10. A computer device comprising a storage medium, a processor, and a computer program stored in the storage medium and executable on the processor, characterized in that: When the processor executes the program, the electromagnetic imaging method based on the composite excitation magnetic field according to any one of claims 1 to 7 is implemented.

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