CN113456032B - Sector scanning magneto-acoustic-electric imaging device and method based on ultrasonic excitation - Google Patents
Sector scanning magneto-acoustic-electric imaging device and method based on ultrasonic excitation Download PDFInfo
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Abstract
The invention relates to a sector scanning magneto-acoustic-electric imaging device and method based on ultrasonic excitation, comprising an imaging device and an image reconstruction module, wherein the imaging device excites a biological tissue to be detected, the acquired magneto-acoustic-electric signals are directly transmitted to the image reconstruction module, and the image reconstruction module processes the acquired magneto-acoustic-electric signals to obtain an electric conductivity image of an object to be detected; the imaging device comprises a sound field excitation module, a magnetic field excitation module and a signal detection module; the image reconstruction module is used for reconstructing conductivity distribution according to the magneto-acoustic-electric voltage signals of the biological tissues to be detected, which are acquired by the signal acquisition circuit and subjected to secondary amplification and filtering. The method and the device of the invention are based on the method that the scanning reference point is outside the object to be detected and the scanning angle is smaller than 180 degrees, can compress the scanning time on the premise of ensuring the imaging quality, and simplify the operation flow.
Description
Technical Field
The invention relates to a magneto-acoustic-electric imaging device and a method, in particular to a sector scanning magneto-acoustic-electric imaging device and a method based on ultrasonic excitation.
Background
The electrical impedance imaging has the technical advantages of nondestructive imaging and functional imaging through tissue electrical property imaging, is a new generation medical imaging technology after morphological and structural imaging, has important value for life science research and early diagnosis of diseases, especially cancers, and provides a brand-new diagnosis method for clinical medicine. When the biological tissue is diseased, the morphological structure of the biological tissue is not greatly changed in early stage, but the charge quantity carried by various chemical substances in the biological tissue, namely the charge space distribution, is greatly changed, and macroscopically shows the change of the electrical characteristics of the diseased tissue including the electrical impedance, the electrical conductivity and the dielectric constant, so that the early diagnosis of the disease can be helped by imaging the electrical characteristics of the diseased tissue, and the early treatment effect is achieved. In 2008, the detection result of a mouse with Nature review before and after treatment of subcutaneous lymphoma shows that the structure of the pathological tissues is not changed obviously, but after the number of tumor cells is reduced obviously, the change of the electrical characteristics of the pathological tissues is very obvious, which further proves that the electrical characteristics of the tissues are changed obviously earlier than the morphology and structure of the tissues in the process of generating and developing tumors.
In 2008, magneto-acoustic-electric imaging methods based on the electrical impedance imaging theory and the ultrasonic imaging theory are proposed for the first time, and with the increasing development of imaging technologies and urgent demands for novel medical imaging technologies, the imaging methods are receiving more and more attention. As an emerging electrical impedance imaging technology, the magneto-acoustic electrical imaging technology can quantitatively measure tissue conductivity and has the characteristics of high contrast of electrical impedance imaging and high resolution of ultrasonic imaging. In 2008, L Kunyansky, C P Ingram and R S Witte have verified the feasibility of rotating magnetoacoustic tomography (MAET) from experiments and theory, in 2021, tong Sun et al proposed an amplification of fast rotating magnetoacoustic tomography based on plane wave filtered back projection algorithm, and Chen Xin et al in Shenzhen university also proposed a magnetoacoustic imaging image reconstruction method and system in patent CN111505107 a. It can be found that: the imaging of a similar imaging device is complex, and the magneto-acoustic electric imaging method needs to take the physical center of the target to be detected as a reference point, and can realize the imaging of the electric parameters of the target to be detected by scanning 360 degrees, so that the required scanning detection time is long, the operation is complex, and the requirements of modern actual clinical medical application are difficult to meet.
Disclosure of Invention
The invention aims to overcome the defect that the existing magneto-acoustic-electric imaging method needs to take the physical center of a target to be detected as a reference point to perform 360-degree scanning to acquire electric parameters for imaging, compress scanning time and simplify operation flow on the premise of ensuring imaging quality, and provides a sector scanning magneto-acoustic-electric imaging device and method based on ultrasonic excitation.
The invention relates to a sector scanning magneto-acoustic imaging device based on ultrasonic excitation, which comprises an imaging device and an image reconstruction module. The imaging device excites the biological tissue to be detected, the acquired magneto-acoustic and electric signals are directly transmitted to the image reconstruction module, and the conductivity image of the object to be detected is obtained after the processing of the image reconstruction module.
The imaging device comprises a sound field excitation module, a magnetic field excitation module and a signal detection module. The sound field excitation module generates a sound field excitation source, i.e., ultrasonic waves. Because the ultrasonic waves can be attenuated rapidly in the air, in order to reduce attenuation and better couple with biological tissues to be detected, a coupling water sac is added later, and the coupling water sac is fully contacted with the acoustic field excitation module, so that the purpose of reducing the attenuation of the ultrasonic waves is achieved. The magnetic field excitation module generates a static magnetic field, and a uniform magnetic field and a non-uniform magnetic field are applicable. The biological tissue to be tested is excited by ultrasonic waves and can generate vibration, so that the magnetic induction wire is cut, the current of the moving source is generated, and the signal detection module collects the current of the moving source and converts the current into a magneto-acoustic electric voltage signal.
The sound field excitation module comprises an ultrasonic driving excitation source, an ultrasonic transducer and a coupling water bag. One end of the ultrasonic transducer is connected with an ultrasonic driving excitation source, and the other end of the ultrasonic transducer is in direct contact with the coupling water bag. The ultrasonic driving excitation source is a voltage source signal, and is transmitted to the ultrasonic transducer through the transmission line, and ultrasonic waves are emitted through the ultrasonic transducer. The coupling water bag is filled with medium water and is filled in the space between the ultrasonic transducer and the biological tissue to be tested, so that the attenuation of ultrasonic waves is reduced, and the ultrasonic waves can act on the biological tissue to be tested.
Alternatively, the excitation signals that may be generated by the ultrasound driven excitation source include, but are not limited to, pulsed excitation signals, continuous wave frequency modulated signals, and specifically modulated excitation signals.
Alternatively, the ultrasound transducer may be an ultrasound transducer array and a single ultrasound transducer. The ultrasonic energy conversion arrays are in fan-shaped arrangement to realize excitation at different angles, and the interval angles between the different ultrasonic energy conversion arrays can be fixed or not; a single ultrasonic transducer controls the emission angle by rotation to achieve large angle excitation.
The magnetic field excitation module adopts an open magnet structure and is placed around the biological tissue to be detected to generate a static magnetic field. Specifically, the permanent magnet, the electromagnet and the superconducting magnet are all applicable, and the uniform magnetic field and the non-uniform magnetic field are all applicable.
The signal detection module consists of a signal detection electrode, a pre-signal amplification circuit, a signal filtering circuit, a post-signal amplification circuit and a signal acquisition circuit. After excitation by a sound field and excitation by a magnetic field, a target tissue to be detected can generate weak kinetic current, a signal detection electrode is in direct contact with the biological tissue to be detected to detect the kinetic current, a detected signal is transmitted to a pre-signal amplification circuit for amplification treatment, the amplified signal is transmitted to a signal filtering circuit for filtering noise in the signal, the noise filtered signal is transmitted to the post-signal amplification circuit for secondary amplification, the acquisition of a signal acquisition circuit is facilitated, the secondary amplified signal is transmitted to the signal acquisition circuit for acquisition, and the signal acquisition circuit transmits the acquired signal to an image reconstruction module.
Alternatively, the detection electrode may be a metal electrode, such as a copper or brass electrode, or a depolarized electrode, such as an Ag-AgCl (silver-silver chloride) electrode.
Alternatively, the signal filtering circuit may use, but is not limited to, a filtering circuit including a butterworth filter, an FIR filter, a wiener filter, and an adaptive filter.
The image reconstruction module is used for reconstructing conductivity distribution according to the magneto-acoustic-electric voltage signals of the biological tissue to be detected, which are acquired by the signal acquisition circuit and subjected to secondary amplification and filtering.
According to another aspect of the invention, the sector scanning magneto-acoustic-electric imaging method based on ultrasonic excitation specifically comprises the following steps:
Step1, an ultrasonic driving excitation source of a sound field excitation module generates an excitation signal which acts on an ultrasonic transducer, and the ultrasonic transducer is coupled with biological tissues to be detected through a coupling water bag;
step 2, the ultrasonic transducer emits ultrasonic waves to excite the biological tissue to be detected, and the biological tissue to be detected is caused to vibrate;
Step 3, a magnetic field excitation module generates a static magnetic field in a biological tissue region to be detected, ions vibrating in the biological tissue to be detected are deflected under the action of Lorentz force under the action of the magnetic field, and then positive charges or negative charges or ions are separated and concentrated, so that a local electric field is formed in the biological tissue to be detected, and a local bioelectric current is generated;
Step 4, the signal detection electrode is directly contacted with the biological tissue to be detected, the biological current is measured, and is collected by a signal collection circuit after the pre-amplification, filtering treatment and post-processing method, and then is transmitted to an image reconstruction module;
And 5, processing by an image reconstruction module according to the known static magnetic field distribution information generated by the magnetic field excitation module and the magneto-acoustic-electric voltage signals acquired by the signal acquisition circuit by adopting an image reconstruction algorithm to reconstruct the conductivity distribution of the biological tissue to be detected.
Further, the specific implementation flow of the image reconstruction module is as follows:
Step 5.1, constructing a voltage matrix according to the acquired magneto-acoustic-electric voltage signals, wherein rows represent voltage values at different positions at the same time, and columns represent voltage values at different times at the same position;
Step 5.2, according to the voltage matrix, deducting according to the reciprocity theorem, and degrading the voltage matrix into a matrix taking the position as a variable, namely a reciprocity current density matrix;
step 5.3, deducing a conductivity matrix, namely numerical values representing the conductivities of different positions according to the reciprocal current density matrix, and performing reconstruction calculation by using a plurality of iterative algorithms including least square iteration and Gaussian-Newton error method iteration;
And 5.4, reconstructing a conductivity distribution image according to the conductivity matrix.
According to the sound pressure-vibration speed coupling equation, the vibration speed of vibration ions at each position in the biological tissue to be detected can be conveniently calculated, and a vibration speed matrix is obtained; the static magnetic field generated by the magnetic field excitation module around the biological tissue to be detected is also a matrix taking the position as a variable, which is called a magnetic field matrix; and then combining the voltage matrix obtained in step 1, and performing matrix operation by applying the reciprocity theorem, so that the average current density of the current density distributed at the biological tissue to be detected can be conveniently obtained, namely, the current density matrix which only takes the position as a variable is degenerated, and the matrix is called a reciprocity current density matrix.
In case the reciprocal current density vector and the reciprocal electric field strength vector are known, the conductivity can be reconstructed by iterative methods. Specifically, the two-dimensional imaging area can be discretized into rectangular small units of M rows and N columns, the conductivity is considered to be uniform in each small rectangular area, then a target functional is established, the problem of reconstructing the conductivity is changed into the problem of finding the optimal conductivity combination, and therefore, only the conductivity matrix which enables the established target functional to obtain the minimum value is required to be solved. And setting a target error according to the obtained reciprocal current density matrix and a reciprocal electric field intensity matrix obtained by gradient calculation of the voltage matrix, and performing iterative calculation by using various algorithms including least square iteration and Gaussian-Newton error method iteration to finally obtain the conductivity matrix meeting the target accuracy.
The beneficial effects are that:
The method and the device of the invention are based on the method that the scanning reference point is outside the object to be detected and the scanning angle is smaller than 180 degrees, can compress the scanning time on the premise of ensuring the imaging quality, and simplify the operation flow.
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For a clearer description of the technical solutions of the present invention, the methods and the specific devices involved, the figures to be used for the embodiments will be briefly described, it being obvious that the following figures are only some embodiments of the present invention, and that it is possible for a person skilled in the art to obtain some of the figures from these figures without inventive effort.
FIG. 1 is a schematic diagram of the composition of a sector scanning magneto-acoustic imaging apparatus based on ultrasonic excitation according to the present invention;
FIG. 2 is a schematic diagram of the workflow of an image reconstruction module of a sector scanning magneto-acoustic imaging apparatus based on ultrasonic excitation in accordance with the present invention;
FIG. 3 is a schematic diagram showing an implementation of P1 in the workflow of the ultrasonic excitation-based sector scanning magneto-acoustic imaging apparatus of the present invention;
FIG. 4 is a schematic diagram showing the implementation of P2 in the workflow of the ultrasonic excitation-based sector scanning magneto-acoustic imaging apparatus of the present invention;
FIG. 5 is a schematic diagram of an embodiment of the invention employing an ultrasonic transducer array for a sector scanning magneto-acoustic imaging apparatus based on ultrasonic excitation;
FIG. 6 is a schematic diagram of an embodiment of the ultrasound excitation-based sector scanning magneto-acoustic imaging apparatus of the present invention employing a single ultrasound transducer;
In the figure, an A1 ultrasonic driving excitation source, an A2 ultrasonic transducer, an A2a ultrasonic transducer array, an A2b single ultrasonic transducer, an A3 coupling water sac, an A4 magnetic field excitation module, an A5 biological tissue to be detected, an A6 signal detection electrode, an A7 pre-signal amplification circuit, an A8 signal filter circuit, an A9 post-signal amplification circuit, an A10 signal acquisition circuit, an A11 image reconstruction module, a 0 scanning reference point, a P1 voltage matrix to reciprocal current density matrix process and a P2 reciprocal current density matrix to conductivity matrix process.
Detailed Description
The technical solutions according to the present invention will be clearly, fully and completely described in the following with reference to the accompanying drawings and detailed description of the embodiments of the invention. It will be apparent that the embodiments to be described below are only some, but not all, embodiments of the invention. All other embodiments obtained without inventive effort, which are within the scope of protection of the invention, are obvious to a person skilled in the art from the examples to be described below.
The invention aims to provide a sector scanning magneto-acoustic-electric imaging device and method based on ultrasonic excitation, which can overcome the defect that the existing magneto-acoustic-electric imaging method needs to take the physical center of a target to be detected as a reference point to perform 360-degree scanning to acquire electric parameters for imaging, compress scanning time on the premise of ensuring imaging quality according to the existing magneto-acoustic-electric imaging theory, simplify operation flow, set the scanning reference point outside the target to be detected, and ensure that the scanning angle is smaller than 180 degrees.
The invention relates to a sector scanning magneto-acoustic imaging system based on ultrasonic excitation, which comprises an imaging device and an image reconstruction module. The imaging device excites the biological tissue to be detected, the acquired magneto-acoustic and electric signals are directly transmitted to the image reconstruction module A11, and the conductivity image of the object to be detected is obtained after the processing of the image reconstruction module.
As shown in the schematic diagram of the composition of the sector scanning magneto-acoustic imaging device based on ultrasonic excitation in fig. 1:
The imaging device comprises a sound field excitation module, a magnetic field excitation module and a signal detection module. The sound field excitation module generates a sound field excitation source, i.e., ultrasonic waves. The magnetic field excitation module A4 generates a static magnetic field. The biological tissue A5 to be measured is excited by ultrasonic waves, and generates a moving source current under the action of a static magnetic field. The signal detection module actively collects the current of the moving source, transmits the current to the image reconstruction module after processing, and realizes reconstruction of the conductivity distribution of the biological tissue to be detected according to the voltage signal.
The sound field excitation module comprises an ultrasonic driving excitation source A1, an ultrasonic transducer A2 and a coupling water bag A3; one end of the ultrasonic transducer A2 is connected with an ultrasonic driving excitation source A1, and the other end of the ultrasonic transducer A2 is in direct contact with the coupling water bag A3. The ultrasonic driving excitation source is a voltage source and is conducted to the ultrasonic transducer A2 through a transmission line to excite the ultrasonic transducer A2 to emit ultrasonic waves. The coupling water bag A3 is filled with medium water, and is filled in the space between the ultrasonic transducer A2 and the biological tissue A5 to be tested, so as to reduce attenuation of ultrasonic waves and enable the ultrasonic waves to act on the biological tissue to be tested.
The magnetic field excitation module A4 adopts an open magnet structure and is placed around the biological tissue A5 to be detected to generate a static magnetic field. Specifically, the permanent magnet, the electromagnet and the superconducting magnet are all applicable, and the uniform magnetic field and the non-uniform magnetic field are all applicable.
The signal detection module comprises a signal detection electrode A6, a preposed signal amplification circuit A7, a signal filter circuit A8, a postsed signal amplification circuit A9 and a signal acquisition circuit A10; the signal detection electrode A6 is in direct contact with the biological tissue A5 to be detected, the other end of the signal detection electrode A6 is connected with the input end of the preposed signal amplification circuit A7, the output end of the preposed signal amplification circuit A7 is connected with the input end of the signal filtering circuit A8, the output end of the signal filtering circuit A8 is connected with the input end of the postsignal amplification circuit A9, the output end of the postsignal amplification circuit A9 is connected with the input end of the signal acquisition circuit A10, and the output end of the signal acquisition circuit A10 is connected with the image reconstruction module A11. Specifically, the signal detection electrode A6 is directly contacted with the biological tissue A5 to be detected, and is used for detecting a voltage signal on the surface of the biological tissue A5 to be detected, the detected signal is transmitted to the pre-signal amplification circuit A7 for amplification treatment, the amplified signal is transmitted to the signal filtering circuit A8 to remove noise in the signal, the noise-removed signal is transmitted to the post-signal amplification circuit A9 for secondary amplification, so that the signal acquisition circuit a10 is conveniently acquired, the secondary amplified signal is transmitted to the signal acquisition circuit a10 for acquisition, and the signal acquisition circuit a10 transmits the acquired signal to the image reconstruction module a11.
The image reconstruction module A11 reconstructs the conductivity distribution of the biological tissue A5 to be detected according to the magneto-acoustic-electric voltage signals of the biological tissue to be detected, which are acquired by the signal acquisition circuit A10 and amplified by the pre-signal amplification circuit A7, filtered by the signal filtering circuit A8 and amplified by the post-signal amplification circuit A9.
The invention relates to a sector scanning magneto-acoustic imaging device and a method based on ultrasonic excitation, which specifically work processes as follows:
The ultrasonic driving excitation source A1 of the sound field excitation module generates an excitation signal which acts on the ultrasonic transducer A2, and the ultrasonic transducer A2 is coupled with the biological tissue A5 to be detected through the coupling water sac A3. The ultrasonic transducer A2 emits ultrasonic waves to excite the biological tissue A5 to be detected, and the biological tissue A5 to be detected is caused to vibrate. The magnetic field excitation module A4 generates a static magnetic field in the region of the biological tissue A5 to be detected, ions vibrating in the biological tissue A5 to be detected are deflected under the action of Lorentz force under the action of the magnetic field, and then positive charges and negative charges or ions are separated and concentrated, so that a local electric field is formed in the biological tissue A5 to be detected, and local bioelectric current is generated. The signal detection electrode A6 is directly contacted with the biological tissue A5 to be detected, the biological current is measured, and after the biological current is amplified by the pre-signal amplification circuit A7, filtered by the signal filtering circuit A8 and amplified by the post-signal amplification circuit A9, the biological current is collected by the signal collection circuit A10 and then transmitted to the image reconstruction module A11. The image reconstruction module A11 adopts an image reconstruction algorithm to process according to the known static magnetic field distribution information generated by the magnetic field excitation module A4 and the magneto-acoustic-electric voltage signal acquired by the signal acquisition circuit A10, so as to reconstruct the conductivity distribution of the biological tissue A5 to be detected.
As shown in a schematic work flow diagram of an image reconstruction module of the sector scanning magneto-acoustic-electric imaging device based on ultrasonic excitation in fig. 2, a specific implementation flow of the image reconstruction module a11 is as follows:
1. constructing a voltage matrix according to the acquired magneto-acoustic-electric voltage signals, wherein rows represent voltage values at different positions at the same time, and columns represent voltage values at different times at the same position;
2. according to the voltage matrix obtained in step1, we perform deduction according to the reciprocity theorem, so that the voltage matrix is degenerated into a matrix which only takes the position as a variable, and the matrix is called a reciprocity current density matrix;
3. Deducing a conductivity matrix, namely numerical values representing conductivities of different positions according to the reciprocal current density matrix obtained in the step 2, wherein the numerical values can be specifically calculated by reconstruction by using algorithms including a least square method and a Gaussian-Newton error method;
4. And (3) reconstructing a conductivity distribution image according to the conductivity matrix obtained in step (3).
As shown in a specific implementation schematic diagram of P1 in the workflow of the sector scanning magneto-acoustic imaging apparatus based on ultrasonic excitation in fig. 3, the invention is as follows:
The specific implementation method of the process P1 for calculating the reciprocal current density matrix by the voltage matrix is as follows: according to the sound pressure-vibration speed coupling equation, the vibration speed of vibration ions at each position in the biological tissue to be detected can be conveniently calculated to obtain a vibration speed matrix; the static magnetic field generated by the magnetic field excitation module around the biological tissue to be detected is also a matrix taking the position as a variable, which is called a magnetic field matrix; and then combining the voltage matrix obtained in step 1, and performing matrix operation by applying the reciprocity theorem, so that the average current density of the current density distributed at the biological tissue to be detected can be conveniently obtained, namely, the current density matrix which only takes the position as a variable is degenerated, and the matrix is called a reciprocity current density matrix.
As shown in a specific implementation schematic diagram of P2 in the workflow of the sector scanning magneto-acoustic imaging apparatus based on ultrasonic excitation in fig. 4, the invention is as follows:
The specific implementation method of the process P2 for calculating the conductivity matrix by the reciprocal current density matrix is as follows: in case the reciprocal current density vector and the reciprocal electric field strength are known, the conductivity can be reconstructed by iterative methods. Specifically, the two-dimensional imaging area can be discretized into rectangular small units of M rows and N columns, the conductivity is considered to be uniform in each small rectangular area, then a target functional is established, the problem of reconstructing the conductivity is changed into the problem of finding the optimal conductivity combination, and therefore, only the conductivity matrix which enables the established target functional to obtain the minimum value is required to be solved. And setting a target error according to the reciprocal current density matrix obtained from P1 and the reciprocal electric field intensity matrix obtained by gradient solving of the voltage matrix, and performing iterative calculation by using various algorithms including least square iteration and Gaussian-Newton error method iteration to finally obtain the conductivity matrix meeting the target precision.
As shown in fig. 5, a schematic diagram of an embodiment of the sector scanning magneto-acoustic imaging apparatus based on ultrasonic excitation according to the present invention using an ultrasonic transducer array is shown:
Specifically, the ultrasonic transducer array A2a is different from the traditional linear transverse array ultrasonic transducer array, but adopts a novel sector array ultrasonic transducer array taking the scanning reference point 0 as the center of a circle, and the interval angle between different ultrasonic transducers can be fixed or not. Therefore, the circle center position is known, the interval angle between the ultrasonic transducers is also known, all the position information can be acquired only by means of the serial numbers of the ultrasonic transducers, the number of parameters required to characterize the position information is greatly reduced, meanwhile, the ultrasonic transducer array A2a is arranged in a fan shape, unlike the traditional linear transverse array arrangement mode, the ultrasonic transducer array A2a does not need to be moved in 360 degrees in an all-round manner, the ultrasonic transducer array A2a smaller than 180 degrees is used for realizing the full coverage of the biological tissue A5 to be tested, all the ultrasonic transducers are only required to be excited once, all the information required to be acquired by the biological tissue A5 to be tested can be acquired through the signal detection electrode A6, and the specific operation flow is greatly simplified.
As shown in fig. 6, a schematic diagram of an embodiment of the sector scanning magneto-acoustic imaging apparatus based on ultrasonic excitation according to the present invention using a single ultrasonic transducer is shown:
Specifically, a single ultrasonic transducer A2b is selected for excitation, the excitation angle of the ultrasonic transducer is slightly adjusted, the full coverage of the biological tissue A5 to be detected can be realized generally only through small-angle regulation and control smaller than 180 degrees, and finally all information of the biological tissue A5 to be detected is acquired through a signal detection electrode A6. Similarly, this approach also has the same advantage as the embodiment of fig. 5 that the number of parameters that characterize the position information that we need can be significantly reduced.
The principles and embodiments of the present invention are explained herein and help to understand the method and core ideas of the present invention by means of specific examples; also, it will be apparent to those skilled in the art that certain modifications may be made in the specific embodiments and application scope of the invention in accordance with the teachings of the present invention. In view of the foregoing, nothing described in this specification should be taken as a limitation on the invention.
Claims (5)
1. The sector scanning magneto-acoustic-electric imaging device based on ultrasonic excitation comprises an imaging device and an image reconstruction module, wherein the imaging device excites biological tissues to be detected, the acquired magneto-acoustic-electric signals are directly transmitted to the image reconstruction module, and the image reconstruction module processes the acquired magneto-acoustic-electric signals to obtain an electric conductivity image of an object to be detected; the method is characterized in that:
the imaging device comprises a sound field excitation module, a magnetic field excitation module and a signal detection module;
The sound field excitation module comprises an ultrasonic driving excitation source, an ultrasonic transducer and a coupling water bag; one end of the ultrasonic transducer is connected with an ultrasonic driving excitation source, and the other end of the ultrasonic transducer is in direct contact with the coupling water bag; the ultrasonic driving excitation source is a voltage source signal, and is transmitted to the ultrasonic transducer through the transmission line, and ultrasonic waves are emitted through the ultrasonic transducer; the coupling water bag is filled with medium water and is filled in a space between the ultrasonic transducer and the biological tissue to be tested, so that attenuation of ultrasonic waves is reduced, and the ultrasonic waves act on the biological tissue to be tested;
The signal detection module comprises a signal detection electrode, a pre-signal amplification circuit, a signal filtering circuit, a post-signal amplification circuit and a signal acquisition circuit; after excitation by a sound field and excitation by a magnetic field, the target tissue to be detected can generate weak kinetic current, the signal detection electrode is in direct contact with the biological tissue to be detected to detect the kinetic current, the detected signal is transmitted to the pre-signal amplification circuit for amplification treatment, the amplified signal is transmitted to the signal filtering circuit for filtering out noise in the signal, the noise-filtered signal is transmitted to the post-signal amplification circuit for secondary amplification, so that the acquisition of the signal acquisition circuit is facilitated, the secondary amplified signal is transmitted to the signal acquisition circuit for acquisition, and the signal acquisition circuit transmits the acquired signal to the image reconstruction module;
the image reconstruction module is used for reconstructing conductivity distribution according to the magneto-acoustic-electric voltage signals of the biological tissue to be detected, which are acquired by the signal acquisition circuit and subjected to secondary amplification and filtering;
The ultrasonic transducer is an ultrasonic transducer array or a single ultrasonic transducer; the ultrasonic transducer arrays are in fan-shaped arrangement by taking a scanning reference point as a circle center so as to realize excitation at different angles, the interval angles among the different ultrasonic transducers are fixed or not fixed, full coverage of biological tissues to be detected is realized through the ultrasonic transducer arrays smaller than 180 degrees, all the ultrasonic transducers are only required to be excited once, and all the information of the biological tissues to be detected is acquired through the signal detection electrode; the single ultrasonic transducer controls the emission angle through rotation to realize large-angle excitation;
a sector scanning magneto-acoustic electro-imaging method based on ultrasonic excitation by the device, comprising the steps of:
Step1, an ultrasonic driving excitation source of a sound field excitation module generates an excitation signal which acts on an ultrasonic transducer, and the ultrasonic transducer is coupled with biological tissues to be detected through a coupling water bag;
step 2, the ultrasonic transducer emits ultrasonic waves to excite the biological tissue to be detected, and the biological tissue to be detected is caused to vibrate;
Step 3, a magnetic field excitation module generates a static magnetic field in a biological tissue region to be detected, ions vibrating in the biological tissue to be detected are deflected under the action of Lorentz force under the action of the magnetic field, and then positive charges or negative charges or ions are separated and concentrated, so that a local electric field is formed in the biological tissue to be detected, and a local bioelectric current is generated;
Step 4, the signal detection electrode is directly contacted with the biological tissue to be detected, the biological current is measured, and is collected by a signal collection circuit after the pre-amplification, filtering treatment and post-processing method, and then is transmitted to an image reconstruction module;
Step 5, the image reconstruction module adopts an image reconstruction algorithm to process according to the known static magnetic field distribution information generated by the magnetic field excitation module and the magneto-acoustic-electric voltage signals acquired by the signal acquisition circuit, so as to reconstruct the conductivity distribution of the biological tissue to be detected;
the specific process of reconstructing the conductivity distribution of the biological tissue to be detected by the image reconstruction module is as follows:
Step 5.1, constructing a voltage matrix according to the acquired magneto-acoustic-electric voltage signals, wherein rows represent voltage values at different positions at the same time, and columns represent voltage values at different times at the same position;
Step 5.2, according to the voltage matrix, deducting according to the reciprocity theorem, and degrading the voltage matrix into a matrix taking the position as a variable, namely a reciprocity current density matrix;
step 5.3, deducing a conductivity matrix, namely numerical values representing the conductivities of different positions according to the reciprocal current density matrix, and performing reconstruction calculation by using a plurality of iterative algorithms including least square iteration and Gaussian-Newton error method iteration;
Step 5.4, reconstructing a conductivity distribution image according to the conductivity matrix;
In the step 5.2, according to a sound pressure-vibration speed coupling equation, calculating the vibration speed of vibration ions at each position in the biological tissue to be detected to obtain a vibration speed matrix; the static magnetic field generated by the magnetic field excitation module around the biological tissue to be detected is also a matrix taking the position as a variable, which is called a magnetic field matrix; combining the voltage matrix obtained in the step 5.1, performing matrix operation by using a reciprocity theorem to obtain the average current density of the current density distribution at the biological tissue to be detected, namely, degrading the current density matrix into a current density matrix taking the position as a variable, which is called a reciprocity current density matrix;
The specific implementation method of the process of calculating the conductivity matrix from the reciprocal current density matrix comprises the following steps: under the condition that the reciprocal current density vector and the reciprocal electric field strength are known, reconstructing the conductivity by an iterative method; dispersing a two-dimensional imaging area into M rows and N columns of rectangular small units, considering that the conductivity is uniform in each small rectangular area, then establishing a target functional, changing the problem of conductivity reconstruction into an optimal conductivity combination problem, and solving a conductivity matrix which enables the established target functional to obtain the minimum value; setting a target error according to a reciprocal current density matrix and a reciprocal electric field intensity matrix obtained by gradient solving of a voltage matrix, and performing iterative calculation to finally obtain a conductivity matrix meeting target precision.
2. A sector scanning magneto-acoustic imaging apparatus based on ultrasonic excitation as claimed in claim 1, wherein: the excitation signals generated by the ultrasonic driving excitation source comprise pulse excitation signals, continuous wave frequency modulation signals and modulation excitation signals.
3. A sector scanning magneto-acoustic imaging apparatus based on ultrasonic excitation as claimed in claim 1, wherein:
The magnetic field excitation module is an open magnet structure, is placed around biological tissues to be detected and is used for generating a static magnetic field, the open magnet structure comprises a permanent magnet, an electromagnet and a superconducting magnet, and the static magnetic field comprises a uniform magnetic field and a non-uniform magnetic field.
4. A sector scanning magneto-acoustic imaging apparatus based on ultrasonic excitation as claimed in claim 1, wherein: the detection electrode is a metal electrode or a depolarization electrode.
5. A sector scanning magneto-acoustic imaging apparatus based on ultrasonic excitation as claimed in claim 1, wherein: the signal filtering circuit uses one of a plurality of filtering circuits including a Butterworth filter, an FIR filter, a wiener filter or an adaptive filter;
the image reconstruction module is used for reconstructing conductivity distribution according to the magneto-acoustic-electric voltage signals of the biological tissue to be detected, which are acquired by the signal acquisition circuit and subjected to secondary amplification and filtering.
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