CN110731774B - Medical multi-focus imaging system and method for imaging biological tissue by using same - Google Patents

Medical multi-focus imaging system and method for imaging biological tissue by using same Download PDF

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CN110731774B
CN110731774B CN201810799248.7A CN201810799248A CN110731774B CN 110731774 B CN110731774 B CN 110731774B CN 201810799248 A CN201810799248 A CN 201810799248A CN 110731774 B CN110731774 B CN 110731774B
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CN110731774A (en
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戴明
陈昕
陈思平
朱慧萍
孙通
于凌尧
陈冕
林浩铭
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Shenzhen University
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    • A—HUMAN NECESSITIES
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Abstract

The medical multi-focus imaging system comprises a conductivity front end detection unit, a control unit, an excitation signal transmission unit and a voltage detection and processing unit; the conductivity front end detection unit comprises a detection water tank, a static magnetic field generation device and a probe; the control unit includes: a control module and a motion control platform; the voltage detection and processing unit includes: the voltage detection module and the conductivity calculation module; in the conductivity acquisition process, the conductivity values measured at the focusing point and the adjacent symmetrical points are adopted, so that the particle vibration amplitude of each focusing point and the particle vibration amplitude of the adjacent symmetrical points are relatively consistent, the Lorentz force generated under the action of the same static magnetic field is also relatively consistent, the influence of the focusing probe on the conductivity imaging resolution in the single excitation of the focusing probe in the Z-axis direction is overcome by using a method of multiple stepping sweep excitation of the single focusing probe, the problem of uneven distribution of ultrasonic excitation vibration sources is solved, and the magneto-acoustic electric conductivity imaging resolution is remarkably improved.

Description

Medical multi-focus imaging system and method for imaging biological tissue by using same
Technical Field
The invention relates to the field of medical imaging, in particular to a medical multi-focus imaging system and a method for imaging biological tissues by using the same.
Background
The existing conductivity detection methods mainly comprise electrical impedance imaging (EIT), magnetic resonance electrical impedance imaging (MREIT), magneto-acoustic imaging (MAT), magneto-acoustic electric imaging (MAET), induction magneto-acoustic imaging (MAT-MI) and difference frequency magneto-acoustic imaging (DF-MAET), but various imaging methods have limitations, such as: the Electrical Impedance (EIT) imaging method is not high in resolution and is not suitable for current tissue conductivity imaging; inductive magnetoacoustic imaging (MAT-MI) uses coil excitation, with alternating magnetic fields influencing the tissue current; the voltage injection magneto-acoustic detection method injects current into an imaging body, and the dispersive distribution of the current reduces the spatial resolution; the magneto-acoustic-electric imaging (MAET) combines the advantages of magnetism, sound and electric field, overcomes the limitation of a traditional single physical field, has the advantages of high resolution of ultrasonic imaging and high contrast of traditional electrical impedance imaging, has low requirements on magnet field intensity and uniformity, is low in cost, can be detected by an electrode, is relatively simple in subsequent processing method, is widely applied to the research of conductivity imaging, but is not difficult to realize by receiving magneto-acoustic-electric signals by an electrode because the existing magneto-acoustic-electric imaging method is based on the reciprocity theorem, the magneto-acoustic-electric inverse process needs to be solved, discomfort exists in the inverse process, vector quantity is scalar, defect of information can be caused in the process of scalar quantity to vector, meanwhile, a problem of solving boundary setting exists, the existing conductivity imaging method adopts a short pulse high-voltage signal for excitation, the instantaneous excitation power for an ultrasonic probe is high, the damage and the weakening of performance of the probe are easy to be caused, and the plane wave common detection probe is adopted for excitation, the average excitation power is not large on an ultrasonic excitation path, the detected signal is low in signal-noise ratio, and the magneto-acoustic-electric signal is received by the electrode, so that the detection function of the probe is not used, and the complex imaging method is difficult to realize based on the high-resolution of the reciprocal imaging and the complex imaging method;
The magnetoacoustic conductivity imaging is used as the supplement of the existing medical imaging method, the magnetic field, the electric field, the sound field and the three physical fields are fused, the imaging method designed by utilizing the advantages of high resolution of ultrasonic imaging, high contrast of electrical impedance imaging and relatively simple subsequent processing of electric field detection signals is based on the magnetoacoustic electric imaging theory, an ultrasonic focusing water immersion power probe is adopted to excite a tested sample, the electric conductivity values of the focusing points and adjacent symmetrical points of each focusing point are obtained by combining excitation signals and electrode detection voltage signals and moving the focusing point of the probe, so that the conductivity distribution map of the focusing probe in biological tissues is obtained. Furthermore, in the field of conductivity imaging, obtaining as high resolution as MRI, photoacoustic imaging remains a worldwide problem, but MRI, photoacoustic imaging, all have its limitations such as: MRI is limited by the environment of use, and imaging is slow, cost is high, photoacoustic imaging can only image the surface of the imaged body with high resolution, and neither method can diagnose cancer early.
Traditional electrical impedance methods are not suitable for biological tissue conductivity imaging; induction magneto-acoustic imaging uses coil excitation, and there is an influence of an alternating magnetic field on tissue current; the voltage injection magneto-acoustic detection method injects current into an imaging body, the dispersion distribution of the voltage injection magneto-acoustic detection method reduces the spatial resolution, magneto-acoustic electric imaging combines the advantages of magnetism, sound and electric fields, the limitation of a traditional single physical field is overcome, the method has the advantages of high resolution of ultrasonic imaging and high contrast of traditional electrical impedance imaging, and has low requirements on magnet field intensity and uniformity, so the cost is low, the method can be used for electrode detection, the subsequent processing method is relatively simple, the current magneto-acoustic electric imaging is based on the reciprocity theorem, plane wave probe excitation is adopted, a narrow pulse high-voltage signal is used as an excitation signal source signal, weak voltage signals are detected through electrode pairs, the probe circumferential scanning excitation is adopted, the magneto-acoustic electric imaging is processed through a magneto-acoustic electric algorithm based on the reciprocity theorem, the magneto-acoustic electric inverse process needs to be solved, discomfort exists in the inverse process, the vector is reached, the defect of information can be caused in the process of the vector is reached by the vector, meanwhile, the problem of boundary setting and solving is also existed, the traditional imaging method adopts the short pulse high-voltage signal for excitation, the transient excitation power is high, the ultrasonic probe is easy to cause damage and performance attenuation of the probe, the plane wave excitation is adopted to carry out excitation, the excitation is adopted as the plane wave excitation, the excitation is adopted to carry out the excitation signal, the current excitation has high power, the average power, the excitation signal is not has high power, the excitation signal has the average excitation signal, and has the average signal, and has the advantages, and the high-quality, and the current excitation is difficult to realize, and has the excitation and has the advantages and high-quality, and can be easily and low. In addition, the plane wave probe with larger probe power and smaller ultrasonic beam is difficult to manufacture, and the problem of unbalanced sound intensity distribution such as sound intensity near a focusing point, small sound intensity far away from the focusing point exists when the focusing probe is used for excitation, so that the detected conductivity amplitude values at two different positions (depths) with the same conductivity change are different, and when a tested sample is excited by the focusing probe, the position of the focusing point in an imaging area cannot be estimated, so that the fact that the conductivity measured by the tested sample when the conductivity change is the same and the position area is different is difficult to ensure that the conductivity measured by the tested sample has larger difference is solved, and the signal to noise ratio of the biological tissue conductivity distribution obtained by adopting plane wave excitation is not high, so that further improvement and perfection are needed.
Disclosure of Invention
The invention provides a medical multi-focus imaging system and a method for imaging biological tissues by using the same, which aim to solve the problems of high computational complexity but low accuracy of the imaging system in the prior art and solve the technical problems of low signal-to-noise ratio and low resolution of a conductivity distribution diagram obtained in the prior art.
The technical scheme adopted for solving the technical problems is as follows:
the medical multi-focus imaging system comprises a conductivity front end detection unit, a control unit, an excitation signal transmission unit and a voltage detection and processing unit:
the conductivity front-end detection unit includes,
the detection water tank is used for containing a sample to be detected, a silver-plated copper electrode is arranged in the detection water tank, and the silver-plated copper electrode is arranged perpendicular to the bottom of the detection water tank;
the static magnetic field generating device comprises two static Ru-Fe-B magnets and a C-shaped bracket which are oppositely arranged at two sides of the detection water tank;
the probe is an ultrasonic water immersion focusing power probe, extends to the surface of the tested sample and is used for providing ultrasonic vibration required for high-power ultrasonic excitation of the tested sample;
the control unit may comprise a control unit for controlling the control unit,
the control module is used for controlling the probe to perform stepping excitation movement through the motion control platform, triggering the excitation signal conveying unit to generate a linear sweep frequency Chirp signal, and triggering the voltage detection and processing unit to perform conductivity calculation processing;
The motion control platform is used for controlling the probe to perform scanning motion at a designated focusing point and feeding back the current position information of the probe motion process to the control module;
the excitation signal conveying unit is respectively connected with the control module and the probe, the excitation signal conveying unit is excited by the control module to generate a linear sweep-frequency Chirp signal, the linear sweep-frequency Chirp signal is conveyed to the probe to excite the probe to generate ultrasonic waves, and the linear sweep-frequency Chirp signal of the excitation signal conveying unit is also conveyed to the voltage detection and processing unit;
the voltage detection and processing unit respectively comprises a voltage detection and processing unit,
the voltage detection module is connected with the excitation signal conveying unit and the detection water tank at the same time and is used for processing a linear sweep frequency Chirp signal from a power divider of the excitation signal conveying unit and an electrode voltage signal from a detection conductivity front-end detection unit;
the conductivity calculation module is used for receiving the electrode voltage signal and the linear sweep Chirp signal processed by the voltage detection module, triggering the electrode voltage signal and the linear sweep Chirp signal to perform conductivity calculation processing by the trigger signal transmitted by the control module, obtaining a conductivity curve of a single measured sample excitation point after the signal processing, and drawing an internal conductivity distribution map of the measured sample according to the conductivity curves of a series of excitation points.
Further preferably, the excitation signal delivery unit includes,
the signal generation module is used for triggering the trigger signal transmitted by the control module to generate a linear sweep frequency Chirp signal;
the power distribution module is used for distributing the linear sweep frequency Chirp signals generated by the signal generation module to the power amplification module and the voltage detection module respectively;
and the power amplification module is used for amplifying the power of the linear sweep frequency Chirp signal from the power distribution module and transmitting the amplified signal to the probe so as to excite the probe to generate ultrasonic waves.
Further, the conductivity calculation module further comprises,
the impedance matching module is connected with the voltage detection module and is used for carrying out impedance matching on the electrode voltage signal from the voltage detection module and the linear sweep Chirp signal;
ADC acquisition module: the analog-to-digital converter is connected with the impedance matching module and is used for converting the two paths of signals processed by the impedance matching module into corresponding digital signals;
and a pre-amplification module: the digital signal amplifying device is connected with the ADC acquisition module and is used for amplifying the digital signals obtained by processing the two paths of signals through the ADC acquisition module;
and the average value processing module is used for: the digital signal processing module is connected with the pre-amplifying module and is used for carrying out mean value processing on the amplified digital signal;
And a band-pass filtering module: the digital signal processing module is connected with the average value processing module and is used for carrying out band-pass filtering processing on the digital signal subjected to average value processing;
digital dot multiplication module: the digital point multiplication processing module is connected with the band-pass frequency wave module and is used for carrying out digital point multiplication processing on the digital signal subjected to band-pass filtering processing;
and a low-pass filtering module: the digital point multiplication module is connected with the digital point multiplication module and is used for carrying out low-pass filtering processing on the digital signal subjected to the digital point multiplication processing;
and an FFT conversion module: the digital signal processing module is connected with the low-pass filtering module and used for processing the digital signal;
the scale conversion and peak detection module: the signal processing module is connected with the FFT conversion module and is used for obtaining a conductivity curve of a single excitation point of the sample to be detected through the intermediate frequency signal;
an imaging processing module: and the conductivity curve of the required excitation point obtained by the scale conversion and peak detection module is collected, and a conductivity distribution diagram is drawn according to the conductivity curve of the required excitation point.
Further, the voltage detection module further comprises a first impedance matching module, a first ADC acquisition module and a first pre-amplification module which are sequentially connected, the first impedance matching module, the first ADC acquisition module and the first pre-amplification module respectively conduct signal processing on electrode voltage signals and linear sweep frequency Chirp signals, the first impedance matching module is electrically connected with the silver-plated copper electrode and the power distribution module, and the first pre-amplification module is connected with the impedance matching module.
Further, the imaging processing module is connected with the first display module, the two-dimensional conductivity distribution diagram drawn by the imaging processing module is displayed on the first display module, and the first display module is further used for displaying state information of the voltage detection module.
Further, the conductivity calculation module is further connected with a first input module, and the first input module is used for inputting a conductivity calculation instruction and a mode required to be displayed by the first display module.
In addition, the control module is also connected with a second display module, and the second display module is an 8-inch Di-Wen DGUS screen with a touch function.
More preferably, the control module is further connected to a second input module, and the second input module is used for inputting a control command and a preset scan plan.
A method for imaging biological tissue by using a conductivity imaging system is characterized in that the probe performs uniform step scanning in the Z-axis direction and the X-axis direction to obtain a tested sampleA two-dimensional conductivity distribution diagram, wherein the Z-axis direction is the direction from the probe to the bottom of the water tank, the X-axis direction is the horizontal direction, and the stepping point in the Z-axis direction is Z 1 ，z 2 ……z m The stepping point in the X-axis direction is X 1 ，x 2 ……x n The method specifically comprises the following steps:
Firstly, after receiving an input instruction of a first input module through a conductivity calculation platform, obtaining a constant k calculated by the conductivity calculation module at an excitation site, wherein k is a constant calculated by the calculation platform and is determined by the step length in the Z-axis direction, the frequency of frequency sweep excitation m in the Z-axis direction, the acquisition frequency of an ADC acquisition module, the sound velocity c and the width T factor of linear frequency sweep, and when a control probe focuses on (x) 1 ，z 1 ) At a site, imaging is performed at the site by a conductivity imaging system, obtained at (x 1 ，z 1 ) Conductivity curve at excitation and extracting z on the curve 1 Focusing point and k magnetoacoustic conductivity values adjacent to the symmetry point position, moving the probe in the Z-axis direction and positioning the probe focus at (x) 1 ，z 2 ) The position is then measured by a conductivity imaging system at (x 1 ，z 2 ) Imaging the position to obtain z 2 Conductivity curve at excitation and extracting z on the curve 2 The focusing point and k magnetoacoustic conductivity values adjacent to the symmetrical point are obtained by repeating the above steps 3 ， z 4 ……z m The magnetoacoustic conductivity values of the focal point and adjacent symmetry points are extracted at the same time, k x m focal points and adjacent symmetry points are extracted, and a first composite conductivity curve along Z axis is obtained based on the position information of each focal point, and the above-mentioned conductivity curve along x axis is obtained 1 A step of acquiring magnetoacoustic conductivity value in Z axis direction of the site, and controlling the probe to x 2 ，x 3 ……x n The Z-axis direction movement of the sites obtains conductivity values of the sites in the Z-axis direction, n synthesized conductivity curves along the Z-axis direction are obtained, k is m is n conductivity values in total, and a two-dimensional conductivity distribution map on the XZ plane can be obtained by combining the probe excitation point positions and corresponding algorithms.
Using conductivity imaging systemsThe biological tissue imaging method is characterized in that the probe performs uniform step scanning in the Z-axis direction, the Y-axis direction and the X-axis direction to obtain a three-dimensional conductivity distribution map of a measured sample, wherein the Z-axis direction is the direction from the probe to the bottom of a detection water tank, the X-axis direction is the horizontal direction, the Y-axis direction is the longitudinal direction vertical to the X-axis, and the step locus is Z in the Z-axis direction 1 ，z 2 …… z m The stepping point in the X-axis direction is X 1 ，x 2 ……x n The stepping locus in the Y-axis direction is Y 1 ，y 2 ……y p The method specifically comprises the following steps:
first, the control probe is at x as described above 1 Site, x 2 ，x 3 ……x n The Z-axis direction movement of the sites obtains the conductivity value of each site in the Z-axis direction, n synthesized conductivity curves along the Z-axis direction are obtained, k is m is n conductivity values in total, and the probe excitation point position and the corresponding algorithm are combined to obtain the y-passing on the XZ plane 1 And then controlling the probe focal point (x n ，y 1 ， z m ) The first start of the return movement is the excitation point (x 1 ，y 1 ，z 1 ) The probe focal point is then controlled to step one step in the Y-axis direction to (x) 1 ，y 2 ，z 1 ) The process of acquiring the two-dimensional conductivity plane distribution map is then repeated, namely when the probe is at the position x 1 ，x 2 ，x 3 ……x n The Z-axis direction movement of the sites obtains the conductivity value of each site in the Z-axis direction, n synthesized conductivity curves along the Z-axis direction are obtained, k is m is n conductivity values in total, and the probe excitation point position and the corresponding algorithm are combined to obtain the y-passing on the XZ plane 2 Is a two-dimensional conductivity profile of (a). And so on, when the probe scans stepwise p times in the Y-axis direction to move to (x) m ，y p ，z n ) And then obtaining two-dimensional conductivity distribution diagrams of p XZ planes, and reconstructing a three-dimensional conductivity distribution diagram in XYZ space by combining Y-axis excitation position information, namely through k, m, n and p conductivity values.
The implementation of the invention can achieve the following beneficial effects:
in the two different focusing points and adjacent symmetrical points, the focusing points of the same probe are used for excitation, so that particle vibration amplitude generated in the focusing points and adjacent symmetrical points in an imaging body is certain (similar), therefore, the principle that the conductivity amplitude of the two focusing points and adjacent symmetrical points with the same conductivity change is similar is utilized, the focusing point positions are changed by moving the focusing probe in the depth direction, so that the conductivity amplitude of each focusing point and adjacent symmetrical points is obtained in the Z axis direction, then the m conductivity curves in the Z axis direction are sequentially obtained by combining with the m-1 stepping excitation in the Z axis direction, then the positions of the probe in the X axis direction are changed, thus obtaining a next batch of m conductivity curves in the Z axis direction, the conductivity values of each focusing point and adjacent symmetrical point are extracted from the m conductivity curves, and then a conductivity curve in the Z axis direction is synthesized, the conductivity curve formed by n-1 stepping movements in the X axis direction is obtained, the two-dimensional conductivity distribution map formed by the conductivity amplitude of each focusing point and adjacent symmetrical point on the X axis is obtained, the ultrasonic vibration amplitude of the focusing point is guaranteed to be in the Z axis direction, thus the ultrasonic vibration resolution is improved, the ultrasonic vibration resolution is greatly influenced when the ultrasonic vibration is focused in the same, and the vibration resolution is greatly influenced in the Z axis direction, and the vibration resolution is greatly influenced by the vibration amplitude of the imaging point, the method has the advantages of high resolution, overcomes the disadvantage of uneven distribution of the conductivity of the non-focusing point, and has the advantages of high conductivity imaging resolution, good signal to noise ratio, low imaging cost, greatly reduced calculation complexity and higher imaging speed.
In the conductivity acquisition process, conductivity values measured at the focusing point and the adjacent symmetrical points are adopted, so that the particle vibration amplitude of each focusing point and the particle vibration amplitude of the adjacent symmetrical points are consistent, the Lorentz force generated under the action of the same static magnetic field is also consistent, the influence of the focusing probe on the conductivity imaging resolution of the focusing probe in the single excitation in the Z-axis direction is overcome by using a method of multiple stepping sweep excitation of the single focusing probe, the problem of uneven distribution of ultrasonic excitation vibration sources is solved, and the magneto-acoustic electric conductivity imaging resolution is remarkably improved.
Drawings
FIG. 1 is a schematic diagram of a medical multi-focal point imaging system of the present invention;
fig. 2 is a schematic structural diagram of a conductivity calculation module according to the present invention;
FIG. 3 is a graph of conductivity magnitudes after 30 conductivity curves along the Z-axis have been aligned in depth of excitation order;
FIG. 4 is a schematic diagram of a focal point position change structure of the probe at a two-layer conductivity change interface;
FIG. 5 is a graph of the conductivity of a sample under test having a two-layer conductivity change interface;
FIG. 6 is a schematic view of a focal point position change structure of the probe at a four-layer conductivity change interface;
FIG. 7 is a graph of conductivity of a sample under test obtained with four layers of conductivity change interfaces;
FIG. 8 is 10 conductivity curves obtained at 10 different focus excitation point positions;
FIG. 9 is a flow chart diagram of a method of two-dimensional imaging with a conductivity imaging system;
fig. 10 is a step diagram of a probe for two-dimensional imaging with a conductivity imaging system.
Reference numerals: 1-detecting a water tank; 2-a sample to be tested; 3-a probe; 4-a control module; 5-a motion control platform; 6-opening; 7-a voltage detection module; 71-a first impedance matching module; 72-a first ADC acquisition module; 73-a first pre-amplification module; 8-a conductivity calculation module; 81-an impedance matching module; an 82-ADC acquisition module; 83-a pre-amplification module; an 84-means processing module; an 85-bandpass filtering module; 86-digital dot multiplication module; 87-a low pass filtering module; 88-FFT conversion module; 89-a scale conversion and peak detection module; 90-an imaging processing module; 9-a signal generation module; 10-a power distribution module; 11-a power amplification module; 12-a first display module; 13-a first input module; 14-a second display module; 15-a second input module; 16-silver-plated copper electrode; 17-static magnetic field generating means; a-a first interface; b-a second interface; c-a third interface; d-a fourth interface; e-a first start excitation position; f-finally focusing the excitation position; g-lower interface; i-lower interface; k-final focal point position; an o-upper interface peak; a p-lower interface peak; h-the thickness of the sample to be measured; q-excitation site.
Detailed Description
For a clearer understanding of technical features, objects and effects of the present invention, a detailed description of embodiments of the present invention will be made with reference to the accompanying drawings. It will be apparent that the described embodiments are only some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Because biological tissues have different electrical characteristics under different physiological and pathological states, peripheral blood vessels are rich in the growth process of tumors, peripheral resistivity can also change, and functional lesions of the biological tissues are earlier than structural lesions, and functional recovery is delayed and structural recovery is performed, so that detection of pathological changes is expected by detecting the change of tissue conductivity, the purpose of early diagnosis of pathological tissues is achieved, and conductivity imaging research has important significance for disease prevention and recovery. The magneto-acoustic electric imaging method and the magneto-acoustic electric imaging system of the invention provide a novel imaging method, which not only can step and scan in the X-axis direction, but also can step and scan and excite in the probe depth direction and the longitudinal depth, and can clearly obtain a two-dimensional conductivity distribution map or a three-dimensional conductivity distribution map which is close to the conductivity of biological tissues. Therefore, the method is expected to obtain high-resolution biological tissue conductivity imaging on the prior magneto-acoustic-electric technology, thereby realizing early diagnosis and treatment of biological tissues such as tumors, cancers and the like. The invention is a magneto-acoustic-electric imaging system based on linear sweep theory, which adopts a linear sweep basic principle probe to excite sample tissue placed in static magnetic field, the sample tissue is excited by an ultrasonic probe to cause local particle vibration, the vibrating particles generate Lorentz force in the magnetic field to separate positive and negative charges, and then a current source is formed in the sample tissue, therefore, the received voltage signal and ultrasonic excitation signal are received through silver-plated copper electrodes placed on the surface of the sample, and then are sent to a mixer through a band-pass filter, and then are subjected to a low-pass filter, and after fast Fourier change and scale transformation, a conductivity curve can be obtained, and the specific structure and method are as follows:
The medical multi-focus imaging system comprises a conductivity front end detection unit, a control unit, an excitation signal transmission unit and a voltage detection and processing unit;
the conductivity front end detection unit includes:
the detection water tank 1 is used for containing a detected sample 2, a silver-plated copper electrode 16 is arranged in the detection water tank 1, and the silver-plated copper electrode 16 is arranged perpendicular to the bottom of the detection water tank 1;
the static magnetic field generating device 17 comprises two static Ru-Fe-B magnets and a C-shaped bracket which are oppositely arranged at two sides of the detection water tank;
the probe 3 is an ultrasonic water immersion focusing power probe and extends to the surface of the tested sample 2, and is used for providing ultrasonic vibration excitation required for high-power ultrasonic excitation on the tested sample 2;
the control unit includes:
the control module 4 is used for controlling the probe 3 to move through the motion control platform 5, triggering the excitation signal conveying unit to generate a linear sweep frequency Chirp signal and triggering the voltage detection and processing unit to perform conductivity calculation processing;
the motion control platform 5 is used for controlling the probe 3 to perform scanning motion at a designated focusing point and feeding back the current position information of the probe 3 in the motion process to the control module 4;
the control module 4 is also connected to a second display module 14, the second display module 14 being an 8 inch touch enabled divin DGUS screen. The control module 4 is further connected to a second input module 15, and the second input module 15 is used for inputting control instructions and a preset scan plan.
The excitation signal conveying unit is respectively connected with the control module 4 and the probe 3, the excitation signal conveying unit is excited by the control module 4 to generate a linear sweep-frequency Chirp signal, the linear sweep-frequency Chirp signal is conveyed to the probe 3 to be excited to generate ultrasonic waves, and the linear sweep-frequency Chirp signal of the excitation signal conveying unit is also conveyed to the voltage detection and processing unit;
the voltage detection and processing unit includes:
the voltage detection module 7 is simultaneously connected with the excitation signal transmission unit and the silver-plated copper electrode in the detection water tank 1 and is used for receiving a linear sweep Chirp signal from the excitation signal transmission unit and an electrode voltage signal from the conductivity front-end detection unit; the voltage detection module 7 further comprises a first impedance matching module 71, a first ADC acquisition module 72 and a first pre-amplification module 73 which are sequentially connected, the first impedance matching module 71, the first ADC acquisition module 72 and the first pre-amplification module 73 respectively perform signal processing on the electrode voltage signal and the linear sweep Chirp signal, wherein the first impedance matching module 71 is electrically connected with the detection water tank 1 and the power distribution module 10, and the first pre-amplification module 73 is connected with the impedance matching module 81.
The conductivity calculation module 8 is configured to receive the electrode voltage signal and the linear sweep Chirp signal processed by the voltage detection module 7, trigger the electrode voltage signal and the linear sweep Chirp signal to perform conductivity calculation processing by using the trigger signal transmitted by the control module 4, obtain a conductivity curve of an excitation point of the single detected sample 2 after the signal processing, and draw an internal conductivity distribution diagram of the detected sample 2 according to the conductivity curves of a series of excitation points. The conductivity calculation module 8 specifically includes:
The impedance matching module 81 is connected with the voltage detection module 7 module and is used for performing impedance matching on the electrode voltage signal from the voltage detection module 7 and the linear sweep Chirp signal;
the ADC acquisition module 82 is connected with the impedance matching module 81 and is used for converting the two paths of signals processed by the impedance matching module 81 into corresponding digital signals through an analog-to-digital converter;
the pre-amplifying module 83 is connected with the ADC acquisition module 82 and is used for amplifying the digital signals obtained by processing the two paths of signals by the ADC acquisition module 82;
the mean value processing module 84 is connected to the pre-amplifying module 83, and is configured to perform mean value processing on the amplified digital signal;
the band-pass filtering module 85 is connected with the mean value processing module 84 and is used for carrying out band-pass filtering processing on the digital signal subjected to mean value processing;
the digital dot multiplication module 86 is connected with the band-pass frequency wave module 85 and is used for carrying out digital dot multiplication on the digital signal subjected to band-pass filtering treatment;
the low-pass filtering module 87 is connected with the digital dot multiplication module 86 and is used for carrying out low-pass filtering processing on the digital signal subjected to the digital dot multiplication processing;
the FFT conversion module 88 is connected with the low-pass filtering module 87 and is used for converting the digital signal processed by the low-pass filtering module 87 into an intermediate frequency signal;
A scale conversion and peak detection module 89 connected with the FFT conversion module 88, and used for obtaining a conductivity curve of a single excitation point of the tested sample 2 through the intermediate frequency signal;
the imaging processing module 90 is connected with the scale conversion and peak detection module 89, acquires the conductivity curve of the required excitation point obtained by the scale conversion and peak detection module 89, and draws a conductivity distribution diagram according to the conductivity curve of the required excitation point; the imaging processing module 90 is connected with the first display module 12, the two-dimensional conductivity distribution diagram drawn by the imaging processing module 90 is displayed on the first display module 12, and the first display module 12 also displays the state information of the voltage detection module 7. The conductivity calculation module 8 is further connected to a first input module 13, and the first input module 13 is used for inputting a conductivity calculation command and a mode required to be displayed by the first display module 12.
The excitation signal transmission unit includes:
the signal generating module 9 is used for triggering the trigger signal transmitted by the control module 4 to generate a linear sweep Chirp signal;
the power distribution module 10 is used for distributing the linear sweep frequency Chirp signals generated by the signal generation module 9 to the power amplification module 11 and the voltage detection module 7 respectively;
The power amplification module 11 is configured to power-amplify the linear sweep Chirp signal from the power distribution module 10 and transmit the amplified signal to the probe 3, so as to excite the probe 3 to generate ultrasonic waves, thereby generating local particle vibration in the sample to be tested.
In the method for two-dimensional imaging by using the conductivity imaging system, as shown in fig. 9, a probe performs uniform step-and-scan in the X-axis direction to obtain a two-dimensional conductivity distribution map of the measured sample 2, wherein the Z-axis direction is the direction from the surface of the measured sample 2 to the bottom of the detection water tank 1, the X-axis direction is the horizontal direction, and the step-by-step point in the Z-axis direction is Z 1 ，z 2 ……z m The stepping point in the X-axis direction is X 1 ，x 2 ……x n The focusing probe 3 excites the sample to be measured at the focusing point to generate particle vibration at the focusing point, and the vibrating particles generate positive and negative charge separation due to the action of the static magnetic field, namely the Lorentz force under the action of the static magnetic body, and the magneto-acoustic voltage signals generated at the two sides of the sample to be measured are detected through a pair of electrodes which are closely attached to the two sides of the sample to be measured and are orthogonal to the static magnetic field direction and the probe excitation direction. The method for obtaining the conductivity amplitude at the focusing point by combining the ultrasonic excitation source signal and the detected magneto-acoustic voltage signal comprises the following steps:
As shown in fig. 10, the number of conductivity amplitudes required to be extracted at the focusing point and adjacent symmetric points of each excitation site is obtained after calculation by the conductivity calculation module, namely, a constant K, where K is a constant calculated by the calculation platform and is determined by factors such as a Z-axis direction stepping length, a Z-axis direction frequency sweep excitation number m, a frequency, a sound velocity c, a linear sweep time width T and the like, the system ADC uses the frequency, the sound velocity c, and the linear sweep time width T, and after receiving an input instruction of the first input module by the conductivity calculation platform, the constant K calculated at the excitation site by the conductivity calculation module is obtained, and is determined after the system setting parameters are determined, where K is a constant value in each step of motion excitation. The probe 3 is then controlled to focus on (x 1 ，z 1 ) On the locus, the circular ring in the figure is an excitation locus q, the distance between the probe 3 and the focusing point is constant at 5cm (probe focusing 5)cm, but also other values) at this site by imaging with a conductivity imaging system, obtained at (x 1 ，z 1 ) Conductivity curve at excitation and extracting z on the curve 1 Magnetoacoustic conductivity values at the focus point and adjacent symmetry point positions (1 focus point + k-1 adjacent symmetry point), the probe is moved in the Z-axis direction and the probe focus is located at (x) 1 ，z 2 ) The position is then measured by a conductivity imaging system at (x 1 ，z 2 ) Imaging the position to obtain z 2 Conductivity curve at excitation and extracting z on the curve 2 The focusing point and k magnetoacoustic conductivity values adjacent to the symmetrical point are obtained by repeating the above steps 3 ，z 4 ……z n The magnetoacoustic conductivity values at the focus point and adjacent symmetry point are then extracted together to obtain k x m focus points and conductivity values at adjacent symmetry points, a first conductivity curve is obtained, according to the above-mentioned at x 1 A step of acquiring magnetoacoustic conductivity values in the Z-axis direction of the site, and controlling the probe 3 to x 2 ，x 3 ……x n The Z-axis direction movement of the sites obtains conductivity values of the sites in the Z-axis direction, n synthesized conductivity curves along the Z-axis direction are obtained, k is m is n conductivity values in total, and a two-dimensional conductivity distribution map on the XZ plane can be obtained by combining the probe excitation point positions and corresponding algorithms.
The individual excitation sites are as follows:
1. linear excitation linear sweep Chirp signals fed to both ends of the ultrasonic probe:
2. the received voltage signal detected by a pair of silver-plated copper electrodes in close proximity to the surface of the sample under test can be expressed as:
3. through carrying out digital coherent demodulation on a transmitting signal and a receiving signal, namely, at each excitation point position, transmitting 10 Chirp excitation signals through a signal generator module, and simultaneously receiving 10 linear sweep frequency Chirp signals through a verasonics system (in the process of collecting the transmitting signal and the receiving signal through a digital band-pass filter), carrying out band-pass filtering and ten times of mean value processing on the transmitting signal and the receiving signal respectively by 2-3Mhz, then carrying out digital dot multiplication, and then carrying out a low-pass filter of 0.6MHz to obtain a difference frequency signal, namely, an intermediate frequency, of the transmitting signal and the receiving signal, wherein the intermediate frequency change generated in a conductivity discontinuous region is related to the depth of the excitation position, and the expression of the transmitting signal and the receiving signal after dot multiplication is as follows:
The intermediate frequency signal after low pass filtering is proportional to:
4. intermediate frequency signal (difference frequency between emission and excitation signal (difference in frequency)):
5. theoretical axial resolution (axial resolution ΔR obtained by the device of the invention)
In the above formula: initial frequency: f (f) 0 =2 MHz, probe center frequency=2.5 MHz, bandwidth: Δf=1 MHz, chirped continuous wave duration: t=1000 μs, probe furthest from biological tissue (or proxy) boundary: r=15 cm, propagation speed of sound waves in biological tissue (or imitation). c=1540m/s.
The specific functions of the modules related to the invention are described below:
and the control module is used for: the device is used for controlling the movement of the focusing point of the probe to focus in the XZ direction for step scanning, and simultaneously is also used for generating two trigger signals, wherein the trigger signal 1 is used for triggering the signal generating module to generate a linear sweep frequency signal, and the trigger signal 2 is used for triggering the conductivity calculating module to perform conductivity calculation processing. The control module presets the pulse width time, sweep frequency start, end frequency, center frequency, delay time, repetition period and other parameter information required by the excitation source, and can also modify the parameters required by the signal generation module through the control module, send the parameters to the signal generation module for signal generation, and turn on and turn off through the trigger signal 1. The MC600 is used as a control module in the present invention. But is not limited to, the control module.
A second input module: the input module is used for inputting control instructions and a preset scanning plan, and is performed by touch, a mouse, keys and the like.
And a second display module: the control module is used for displaying the position data of the motion control platform, the scanning plan and the scanning progress, receiving the information such as the instruction, the trigger signal state, the control module state and the like by the control module, and feeding back the received control module state information by the control module. Preferably, an 8 inch touch enabled Di-text DGUS screen is used for display.
A signal generation module: when the information required by the excitation sources such as pulse width time, sweep frequency start, stop frequency, center frequency, delay time, repetition period and the like sent by the control module is received, the signal generation module generates a linear sweep frequency continuous wave excitation signal, namely a linear sweep frequency Chirp signal, and the signal output port signal is started or cut off by receiving the trigger signal 1, so that the excitation signal source is started or cut off. For generating a chirped continuous wave signal required for detection. In this embodiment, the signal generator is generated by a direct digital frequency synthesizer (Direct Digital Synthesizer, abbreviated as "DDS"), which has the advantages of low cost and power consumption, high resolution, and fast conversion time. In practical application, the method is preferably realized by adopting an AD9952DDS chip with modulation functions such as amplitude modulation, frequency modulation, phase modulation and the like and an on-chip D/A converter, and can also synthesize a chirp excitation signal with 2-3 MHz, 1Mhz bandwidth, 100-2000us adjustable sweep time and 200mv amplitude by adopting an internal program of a Verasonics system.
A first input module: the system is used for inputting a conductivity calculation instruction and a mode required to be displayed by the first display module, and feeding back the received control module state information through the module.
A first display module: the system is used for displaying information such as a conductivity calculation result and a state of the voltage detection module, and can be an input module such as a keyboard, a mouse, a touch screen and the like.
And a power distribution module: and the linear sweep frequency excitation signal generated by the signal generating module is distributed, one path of distributed signal is sent to the power amplifying module and then sent to the ultrasonic power probe, and the other path of distributed signal is sent to the voltage detecting module for ADC acquisition and subsequent signal processing. Which is mainly used for the shunting of the signal.
And a power amplification module: the power amplifier is used for amplifying the power of the excitation signal after passing through the power distribution module and then sending the power to the ultrasonic excitation probe. The power amplification module is adjustable by 0-60DB, and 53DB is generally used for power amplification of the ultrasonic excitation signal.
Probe: the ultrasonic water immersion focusing power probe is used for carrying out high-power ultrasonic excitation on a test sample, so that the ultrasonic waves cause particles to vibrate in a tissue body, the sample in a static magnetic field generates charge separation under the action of Lorentz force, and finally, the charges are accumulated on an electrode to form a weak voltage signal. The invention adopts a high-power ultrasonic excitation probe with the bandwidth of 1.8-3.5MHz, the focusing depth of 5cm, water immersion and excitation power of 2W, preferably, a French Imasonic CDC10963 probe or a Blatek water immersion focusing high-power excitation probe. And the probe needs to be subjected to 50 ohm impedance matching and magnetic shielding treatment. The invention adopts the focusing point of the focusing probe to perform point-by-point stepping sweep-frequency excitation on the imitation body.
Motion control platform: the ultrasonic probe is used for controlling and controlling the ultrasonic probe to scan at a designated focusing point and feeding back the current position information of the motion process to the control system. Specifically, the motion control platform is used for controlling the ultrasonic probe to focus in a direction along the excitation direction of the probe (Z-axis direction), wherein the step length of each step in the Z-axis direction is set to be 2, and controlling the focusing point of the ultrasonic probe to perform step scanning along the electrode direction (X-axis direction), the step length of motion in the direction is set to be l, in the process of point-by-point motion of the probe, the focusing point of the probe is firstly arranged at a certain point A on the X-axis, then the probe sequentially moves in a downward step scanning manner along the Z-axis, after the probe finishes scanning on the Z-axis, the probe returns to the original position A on the Z-axis, and sequentially moves in a downward step scanning manner along the Z-axis, and each step length is d until the probe finishes scanning in the Z-axis direction, and then the focusing point of the probe moves to the initial position B, and then the step length l is horizontally moved on the X-axis, in the previous step length is required to be scanned, and in the scanning process, after the focusing point of the probe moves to the target excitation point and is still, a trigger signal is generated by the control and calculation module, and the trigger signal module is started to the excitation signal generation module to excite the sample to be detected. In the probe motion control, a motion command is generated through a motion control module, three stepping motors of an X axis, a Y axis and a Z axis in a motion control platform are controlled, and the stepping motion of the probe in space is controlled through the motion speed, the motion step length, the motion acceleration and the like of each stepping motor are controlled through the control module.
Conductivity calculation module: the method is that the voltage detection module is used for obtaining excitation signals and electrode voltage signals after the power distribution module, impedance matching, ADC acquisition, pre-amplification, mean processing and band-pass filtering are respectively carried out on the two paths of signals, then digital point multiplication and low-pass filtering are carried out, then the intermediate frequency signals are obtained through FFT conversion, the conductivity curve of the imitation body when a single excitation point is arranged in the Z axis direction is obtained through scale conversion and peak detection, after m times of stepping excitation in the Z axis direction, the conductivity calculation module is used for obtaining m conductivity curves, then the conductivity calculation module is used for extracting k conductivity values of each focusing excitation point and adjacent symmetrical points, the conductivity calculation module is used for synthesizing a conductivity curve in the Z axis direction through combining probe position information, then a step length is carried out on the X axis, the operation is repeated, a second synthesized conductivity curve is obtained, until n conductivity curves are synthesized, meanwhile, the control module is used for giving out a stop motion instruction to the motion control platform, the control module is used for generating a trigger signal 2, the conductivity calculation module is used for calculating a two-dimensional conductivity distribution map according to the step length of the X axis and the conductivity distribution map, and conducting linear interpolation treatment on the conductivity distribution map through the linear interpolation calculation module. Preferably, the conductivity calculation module uses a Verasonics calculation platform.
In addition, the conductivity calculation module can also automatically adjust the ADC and the impedance adjustment module of the voltage detection module and detect the state of the ADC and the impedance adjustment module.
The voltage detection module: the voltage detection module is used for carrying out impedance matching, ADC acquisition, pre-amplification and other processes on the excitation signals, and simultaneously carrying out impedance matching, ADC acquisition, pre-amplification and other processes on the electrode voltage signals, and feeding back the state information of the voltage detection module to the control and calculation module.
In order to reduce the influence of random noise on the imaging resolution, as shown in fig. 8, at each focusing excitation point position, we acquire the transmission signal and the reception signal 10 times, and perform averaging processing 10 times and then perform corresponding algorithm processing to obtain a conductivity curve, where g represents a lower interface, i represents a lower interface, k represents a final focusing point position, o represents an upper interface peak, p represents a lower interface peak, and h represents a thickness of the measured sample 2.
Fig. 8 is used to show the variation of the amplitude of the upper and lower electrical conductivity variation interfaces of the sample 2 to be measured uniformly after single focusing excitation, 10 electrical conductivity graphs are obtained at 10 different focusing excitation points, wherein the two peak values on each electrical conductivity graph represent the variation of the amplitude of the upper and lower electrical conductivity of the sample 2 to be measured when the sample 2 to be measured is excited at different excitation points, and the average value of the 10-time amplitude of the upper interface i is similar to the average value of the 10-time amplitude of the lower interface g, so as to show the variation of the amplitude of the electrical conductivity variation interface of the focusing probe in the stepping excitation process, that is, the amplitude of the electrical conductivity variation interface is affected by the excitation position of the single focusing point.
The two-dimensional conductivity profiles obtained in the XZ plane are set forth below for 30 focal points along the Z axis: the method comprises the steps of carrying out dynamic focusing and stepping excitation for 30 times in the Z-axis direction to obtain 30 conductivity curves, arranging the conductivity curves on a transverse axis sequentially, obtaining four interfaces shown in fig. 3 through an image processing method, wherein transverse data in fig. 3 are the times of stepping frequency sweeping in the Z-axis direction, the first interface a, the second interface b, the third interface c and the fourth interface d are seen from top to bottom, the conductivity amplitude of each interface is extracted, the average value is removed, the average value is used as the conductivity amplitude of the corresponding interface position, the four conductivity curves are converted into position information in the Z-axis direction according to a parallel line imaging principle, then the position information in the Z-axis direction is combined with a starting position point, a conductivity curve with the conductivity amplitude more accurate in the Z-axis direction can be obtained, the probe is moved in the X-axis direction, the operation is repeated, another conductivity curve in the Z-axis direction can be obtained, n conductivity curves are sequentially scanned in a stepping mode on the X-axis, and then the two-dimensional conductivity distribution map is obtained by combining the n synthesized conductivity curves with the position information.
The measured sample 2 is not subjected to hole digging treatment, the probe movement mode is shown in fig. 4, and fig. 4 is a schematic diagram of a position change structure of the probe in the measured sample 2 from a first starting excitation position e to a last focusing excitation position f in a stepping manner; the resultant conductivity graph obtained by stepping the sweep excitation from the first starting excitation position e to the last focusing excitation position f above the sample 2 to be measured with the probe controlled to focus on the first starting excitation position e, wherein the X-value represents the X-axis coordinate, the Y-value represents the site conductivity value, the first peak represents the first interface a, i.e., the upper interface, the second peak represents the fourth interface d, i.e., the lower or bottom interface, and the X-axis depth represents the distance between the first interface to the second interface, is shown in fig. 5.
The tested sample 2 is dug with a hole 6, four layers of conductivity change interfaces can be obtained, the probe movement mode is shown in fig. 6, and fig. 6 is a schematic diagram of the change of the probe focusing point position by controlling the probe to focus on the first starting excitation position above the tested sample to move to the last focusing excitation position in a stepping way; as shown in fig. 6, the probe is controlled to focus on a composite conductivity graph (amplitude represents an interface position, a first peak represents a first interface a, a second peak represents a second interface b, wherein an X value represents an X-axis coordinate, a Y value represents a conductivity value of the site, an X-axis depth represents a distance between the first interface a and the second interface b, a third peak of a third interface c and a fourth peak of a fourth interface d can be obtained sequentially, a conductivity change interface can obtain a peak, the peak position is related to the conductivity change position, the first peak is similar to the fourth peak in size, the second peak is similar to the third peak in size, and the first peak and the fourth peak are distances between the upper interface of the imitation body and the lower interface, namely the thickness of the measured sample 2.
In the method for carrying out three-dimensional imaging by utilizing the conductivity imaging system, a probe 3 carries out uniform step scanning in the Z-axis direction, the Y-axis direction and the X-axis direction to obtain a two-dimensional conductivity distribution diagram of a tested sample 2, wherein the Z-axis direction is the direction from the surface of the probe to the bottom of a detection water tank 1, the X-axis direction is the horizontal direction, the Y-axis direction is the longitudinal direction vertical to the X-axis, and the step locus is Z in the Z-axis direction 1 ，z 2 ……z m The stepping point in the X-axis direction is X 1 ，x 2 ……x n The stepping locus in the Y-axis direction is Y 1 ，y 2 ……y p The specific three-dimensional imaging process comprises the following steps:
first, the probe is controlled at the x1 position, x 2 ，x 3 ……x n The Z-axis direction movement of the sites obtains the conductivity value of each site in the Z-axis direction, n synthesized conductivity curves along the Z-axis direction are obtained, k is m is n conductivity values in total, and the probe excitation point position and the corresponding algorithm are combined to obtain the y-passing on the XZ plane 1 And then controlling the probe focal point (x n ，y 1 ， z m ) The first start of the return movement is the excitation point (x 1 ，y 1 ，z 1 ) Subsequently controlling the probe againThe focus point is stepped one step in the Y-axis direction to (x) 1 ，y 2 ，z 1 ) The process of acquiring the two-dimensional conductivity plane distribution map is then repeated, namely when the probe is at the position x 1 ，x 2 ，x 3 ……x n The Z-axis direction movement of the sites obtains the conductivity value of each site in the Z-axis direction, n synthesized conductivity curves along the Z-axis direction are obtained, k is m is n conductivity values in total, and the probe excitation point position and the corresponding algorithm are combined to obtain the y-passing on the XZ plane 2 Is a two-dimensional conductivity profile of (a). And so on, when the probe scans stepwise p times in the Y-axis direction to move to (x) m ，y p ，z n ) And then obtaining two-dimensional conductivity distribution diagrams of p XZ planes, and reconstructing a three-dimensional conductivity distribution diagram in XYZ space by combining Y-axis excitation position information, namely through k, m, n and p conductivity values.
The XYZ directions represent the magnetic field direction, the ultrasonic excitation direction and the electrode detection direction are perpendicular to each other, and for convenience of description and understanding, X represents the horizontal direction, Z represents the vertical direction, and Y represents the direction perpendicular to the XZ plane, but is not limited to the above description.
The embodiments of the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to the above-described embodiments, which are merely illustrative and not restrictive, and many forms may be made by those having ordinary skill in the art without departing from the spirit of the present invention and the scope of the claims, which are to be protected by the present invention.

Claims (10)

1. A method for imaging biological tissues by using a medical multi-focus imaging system is characterized in that a probe (3) of the medical multi-focus imaging system performs uniform step scanning in a Z-axis direction and an X-axis direction to obtain a two-dimensional conductivity distribution map of a tested sample (2), wherein the Z-axis direction is a direction from the probe (3) to the bottom of a water tank (1), the X-axis direction is a horizontal direction, and a stepping point in the Z-axis direction is Z 1 ，z 2 ……z m The stepping point in the X-axis direction is X 1 ，x 2 ……x n The method comprises the following steps:
firstly, after receiving an input instruction of a first input module (13) through a conductivity calculation platform, obtaining a constant k calculated by the conductivity calculation module at an excitation site, wherein k is a constant calculated by the calculation platform and is determined by a Z-axis direction stepping length, a Z-axis direction frequency sweep excitation frequency m, an ADC acquisition module (82) acquisition frequency sound velocity c and a linear frequency sweep time width T factor, and when a control probe (3) focuses on (x) 1 ，z 1 ) At a site, imaging is performed at the site by a conductivity imaging system, obtained at (x 1 ，z 1 ) Conductivity curve at excitation and extracting z on the curve 1 Focusing point and k magnetoacoustic conductivity values adjacent to the symmetry point position, moving the probe in the Z-axis direction and positioning the probe focus at (x) 1 ，z 2 ) The position is then measured by a conductivity imaging system at (x 1 ，z 2 ) Imaging the position to obtain z 2 Conductivity curve at excitation and extracting z on the curve 2 The focusing point and k magnetoacoustic conductivity values adjacent to the symmetrical point are obtained by repeating the above steps 3 ，z 4 ……z m The magnetoacoustic conductivity values of the focal point and adjacent symmetry points are extracted, and a first composite conductivity curve along Z axis is obtained based on the information of each focal point position 1 A step of acquiring magnetoacoustic conductivity values in the Z-axis direction of the site, the probe (3) being controlled in x 2 ，x 3 ……x n The Z-axis direction movement of the sites obtains conductivity values of each site in the Z-axis direction, n synthesized conductivity curves along the Z-axis direction are obtained, k multiplied by m multiplied by n conductivity values are combined, and the probe excitation point position and the corresponding algorithm are combined, so that a two-dimensional conductivity distribution map on the XZ plane can be obtained.
2. The method according to claim 1, characterized in that the probe (3) of the medical multi-focal point imaging system is in the Z-axis directionUniformly step-scanning in the Y-axis direction and the X-axis direction to obtain a three-dimensional conductivity distribution diagram of a tested sample (2), wherein the Z-axis direction is the direction from a probe (3) to the bottom of a detection water tank (1), the X-axis direction is the horizontal direction, the Y-axis direction is the longitudinal direction vertical to the X-axis, and a step site in the Z-axis direction is Z 1 ，z 2 ……z m The stepping point in the X-axis direction is X 1 ，x 2 ……x n The stepping locus in the Y-axis direction is Y 1 ，y 2 ……y p The method comprises the following steps:
first, the probe is controlled at x 1 Site, x 2 ，x 3 ……x n The Z-axis direction movement of the sites obtains the conductivity value of each site in the Z-axis direction, n synthesized conductivity curves along the Z-axis direction are obtained, k multiplied by m multiplied by n conductivity values are combined, and the probe excitation point position and the corresponding algorithm are combined, so that the X Z plane passing through y can be obtained 1 And then controlling the probe focal point (x n ，y 1 ，z m ) The first start of the return movement is the excitation point (x 1 ，y 1 ，z 1 ) The probe focal point is then controlled to step one step in the Y-axis direction to (x) 1 ，y 2 ，z 1 ) The process of acquiring the two-dimensional conductivity profile is then repeated, i.e. when the probe is at x 1 ，x 2 ，x 3 ……x n The Z-axis direction movement of the sites obtains the conductivity value of each site in the Z-axis direction, n synthesized conductivity curves along the Z-axis direction are obtained, k multiplied by m multiplied by n conductivity values are combined, and the probe excitation point position and the corresponding algorithm are combined, so that the X Z plane passing through y can be obtained 2 And so on, as the probe is stepped through p times in the Y-axis direction to (x) m ，y p ，z n ) And then obtaining two-dimensional conductivity distribution diagrams of p XZ planes, and reconstructing a three-dimensional conductivity distribution diagram in XYZ space by combining Y-axis excitation position information, namely through k multiplied by m multiplied by n multiplied by p conductivity values.
3. The method according to claim 1 or 2, wherein the medical multi-focus imaging system comprises a conductivity front-end detection unit, a control unit, an excitation signal delivery unit and a voltage detection and processing unit:
the conductivity front-end detection unit includes,
The detection water tank (1) is used for containing a detected sample (2), a silver-plated copper electrode (16) is arranged in the detection water tank (1), and the silver-plated copper electrode (16) is arranged perpendicular to the bottom of the detection water tank (1);
the static magnetic field generating device (17) comprises two static Ru-Fe-B magnets and C-shaped brackets, wherein the two static Ru-Fe-B magnets and the C-shaped brackets are oppositely arranged on two sides of the detection water tank (1);
the probe (3) is an ultrasonic linear array probe, extends to the surface of the tested sample (2) and is used for providing ultrasonic waves required for high-power ultrasonic electronic focusing excitation on the tested sample (2);
the control unit may comprise a control unit for controlling the control unit,
the control module (4) is used for controlling the probe (3) to perform stepping excitation movement through the motion control platform (5), and the control module (4) is used for triggering the excitation signal conveying unit to generate a linear sweep frequency Chirp signal and is also used for triggering the voltage detection and processing unit to perform conductivity calculation processing;
the motion control platform (5) is used for controlling the probe (3) to perform scanning motion at a designated focusing point and feeding back the current position information of the motion process of the probe (3) to the control module (4);
the excitation signal conveying unit is respectively connected with the control module (4) and the probe (3), the excitation signal conveying unit is excited by the control module (4) to generate a linear sweep-frequency Chirp signal, the linear sweep-frequency Chirp signal is conveyed to the probe (3) to excite the probe to generate ultrasonic waves, and the linear sweep-frequency Chirp signal of the excitation signal conveying unit is also conveyed to the voltage detection and processing unit;
The voltage detection and processing unit respectively comprises a voltage detection and processing unit,
the voltage detection module (7) is connected with the excitation signal conveying unit and the detection water tank (1) at the same time and is used for processing a linear sweep Chirp signal from a power distributor of the excitation signal conveying unit and an electrode voltage signal from a detection conductivity front-end detection unit;
the conductivity calculation module (8) is used for receiving the electrode voltage signal and the linear sweep Chirp signal processed by the voltage detection module (7), triggering the electrode voltage signal and the linear sweep Chirp signal to be subjected to conductivity calculation processing by the trigger signal transmitted by the control module (4), obtaining a conductivity curve of an excitation point of a single tested sample (2) after the signal processing, and drawing an internal conductivity distribution map of the tested sample (2) according to the conductivity curves of a series of excitation points.
4. A method as claimed in claim 3, wherein: the excitation signal transmission unit includes:
the signal generation module (9) is used for triggering the trigger signal transmitted by the control module (4) to generate a linear sweep frequency Chirp signal;
the power distribution module (10) is used for distributing the linear sweep frequency Chirp signals generated by the signal generation module (9) to the power amplification module (11) and the voltage detection module (7) respectively;
And the power amplification module (11) is used for amplifying the power of the linear sweep Chirp signal from the power distribution module (10) and transmitting the signal to the probe (3) so as to excite the probe (3) to generate ultrasonic waves.
5. A method as claimed in claim 3, wherein: the conductivity calculation module (8) further comprises:
the impedance matching module (81) is connected with the voltage detection module (7) and is used for carrying out impedance matching on the electrode voltage signal from the voltage detection module (7) and the linear sweep Chirp signal;
the ADC acquisition module (82) is connected with the impedance matching module (81) and is used for converting the two paths of signals processed by the impedance matching module (81) into corresponding digital signals through the analog-to-digital converter;
the pre-amplifying module (83) is connected with the ADC acquisition module (82) and is used for amplifying the digital signals obtained by processing the two paths of signals by the ADC acquisition module (82);
the mean value processing module (84) is connected with the pre-amplifying module (83) and is used for carrying out mean value processing on the amplified digital signals;
the band-pass filtering module (85) is connected with the mean value processing module (84) and is used for carrying out band-pass filtering processing on the digital signal subjected to mean value processing;
The digital dot multiplication module (86) is connected with the band-pass filtering module (85) and is used for carrying out digital dot multiplication on the digital signal subjected to band-pass filtering treatment;
the low-pass filtering module (87) is connected with the digital dot multiplication module (86) and is used for carrying out low-pass filtering treatment on the digital signal subjected to the digital dot multiplication treatment;
the FFT conversion module (88) is connected with the low-pass filtering module (87) and is used for converting the digital signal processed by the low-pass filtering module (87) into an intermediate frequency signal;
the scale conversion and peak detection module (89) is connected with the FFT conversion module (88) and is used for obtaining a conductivity curve of a single excitation point of the tested sample (2) through the intermediate frequency signal;
and the imaging processing module (90) is connected with the scale conversion and peak detection module (89), acquires the conductivity curve of the required excitation point obtained by the scale conversion and peak detection module (89), and draws a conductivity distribution diagram according to the conductivity curve of the required excitation point.
6. The method of claim 4, wherein: the voltage detection module (7) further comprises a first impedance matching module (71), a first ADC acquisition module (72) and a first pre-amplification module (73) which are sequentially connected, the first impedance matching module (71), the first ADC acquisition module (72) and the first pre-amplification module (73) respectively conduct signal processing on electrode voltage signals and linear sweep Chirp signals, the first impedance matching module (71) is electrically connected with a silver-plated copper electrode and the power distribution module (10), and the first pre-amplification module (73) is connected with the impedance matching module (81).
7. The method of claim 5, wherein: the imaging processing module (90) is connected with the first display module (12), the two-dimensional conductivity distribution diagram drawn by the imaging processing module (90) is displayed on the first display module (12), and the first display module (12) also displays the state information of the voltage detection module (7).
8. The method of claim 7, wherein: the conductivity calculation module (8) is also connected with a first input module (13), and the first input module (13) is used for inputting a conductivity calculation instruction and a mode required to be displayed by the first display module (12).
9. A method as claimed in claim 3, wherein: the control module (4) is also connected with a second display module (14), and the second display module (14) is an 8-inch Divin DGUS screen with a touch function.
10. A method as claimed in claim 3, wherein: the control module (4) is also connected with a second input module (15), and the second input module (15) is used for inputting control instructions and a preset scanning plan.
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