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CN116687374A - Quantitative microwave thermo-acoustic microscopic imaging method and storage medium - Google Patents

Quantitative microwave thermo-acoustic microscopic imaging method and storage medium Download PDF

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CN116687374A
CN116687374A CN202310661220.8A CN202310661220A CN116687374A CN 116687374 A CN116687374 A CN 116687374A CN 202310661220 A CN202310661220 A CN 202310661220A CN 116687374 A CN116687374 A CN 116687374A
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陈艺
迟子惠
杜爽
蒋华北
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Chongqing University of Post and Telecommunications
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Abstract

The invention discloses a quantitative microwave thermo-acoustic microscopic imaging method and a storage medium, which are used for reconstructing electromagnetic parameters. According to the method, based on a finite element solution thermo-acoustic wave equation and a Helmholtz equation, an A-line image is formed, so that conductivity reconstruction in the depth direction can be obtained, quantitative values in one-dimensional depth are achieved, a two-dimensional B-scan image or a projection plane image can be obtained by combining all the A-line images, then a three-dimensional image can be obtained by combining all the B-scan images, and three-dimensional structure imaging is achieved while the quantitative reconstruction of three-dimensional biological tissue conductivity is guaranteed. The method comprises the following specific steps: (1) sub-domain partitioning of a solution area; (2) selecting an appropriate interpolation function; (3) discrete processing of solving the equation; (4) And carrying out forward solving on the discrete equation and obtaining a three-dimensional thermo-acoustic signal for inverse solving of the equation through a microwave thermo-acoustic microscopic imaging system, thereby obtaining conductivity reconstruction.

Description

Quantitative microwave thermo-acoustic microscopic imaging method and storage medium
Technical Field
The invention belongs to the technical field of microwave thermo-acoustic imaging, and particularly relates to the field of quantitative microwave thermo-acoustic imaging reconstruction.
Background
Along with the improvement of living standard of people, health problems are more and more emphasized. In order to realize accurate diagnosis of diseases, traditional medical image inspection technologies are continuously improved and perfected in recent years, but limitations still exist in each technology, such as an X-ray imaging technology (X-ray) and a computed tomography technology (Computed Tomography, CT) can generate ionizing radiation harmful to human bodies, the contrast of an ultrasonic imaging technology (Ultrasound Imaging, UI) is not high, and a nuclear magnetic resonance imaging technology (Magnetic Resonance Imaging, MRI) is high in price. Thus, various new techniques for disease diagnosis have been developed, wherein the Microwave thermo-acoustic imaging (MTAT) technique is a high-contrast hybrid medical imaging mode combining high resolution of ultrasonic imaging techniques and Microwave imaging techniques.
MTAT uses dielectric contrast in biological tissue to reconstruct high resolution and high contrast tissue thermo-acoustic image, and has shown unique advantages in various biomedical application studies, such as early diagnosis of breast cancer, brain tumor and cerebral hemorrhage imaging, foreign body detection, surgical guidance, etc. The traditional MTAT technology in the early stage is mostly a qualitative imaging algorithm, only can reconstruct the absorption energy density and the like, and cannot quantitatively characterize the distribution of electromagnetic characteristics such as conductivity and the like. The noninvasive quantitative reconstruction of biological tissue electromagnetic properties has important scientific research significance and clinical application value for promoting the development of MTAT technology and even for promoting the accurate diagnosis of the whole biomedical electromagnetics on diseases. Wherein the guilloume Bal group quantitatively analyzed MTAT reconstitution in 2011, they proposed a two-step quantitative algorithm to reconstitute conductivity. However, the quantitative algorithm only carries out numerical simulation verification, and the feasibility of the quantitative algorithm is not verified by actual measurement experiments. In 2012 the Paul Board group, the electric field distribution obtained by using CST simulation software is combined with the absorption distribution obtained by MATLAB calculation to quantitatively reconstruct the conductivity distribution by mixed programming, and the group also only performs numerical simulation verification. In 2022, wang Xiongxiao, a microwave thermo-acoustic imaging technology is proposed to quantitatively reconstruct tissue dielectric characteristics based on deep learning, but a method based on deep learning relies on a large number of training sets, and cannot quantitatively reconstruct the conductivities of various samples at will. While the thought and algorithm of quantitative reconstruction of conductivity of MTAT were first proposed and developed in the H.B. Jiang group (one of the authors of this patent) in 2010, and the feasibility of the quantitative algorithm was verified in breast cancer MTAT, but the imaging resolution of thermo-acoustic signals acquired by the microwave thermo-acoustic tomography system relied on by the algorithm was limited to millimeter or sub-millimeter level, and the distribution of microwave radiation fields was uneven, the present team proposed and built a microwave thermo-acoustic microscopic imaging system (application publication No. CN 114587326A), based on which this patent would propose a quantitative microwave thermo-acoustic microscopic imaging method based on finite element solution thermo-acoustic wave equation and Helmholtz equation to directly quantitatively reconstruct conductivity in depth directions of various samples.
Through retrieval, application publication number CN104473640a, a conductivity reconstruction method for magnetocaloric acoustic imaging is based on the magnetocaloric acoustic imaging principle. The exciting coil is used for applying MHz current excitation to the conductive object, so that Joule heat is generated in the conductive object, and further an ultrasonic signal is generated. And receiving ultrasonic signals by utilizing an ultrasonic transducer, processing and collecting the received ultrasonic signals, and then acquiring a conductivity image of the conductive object by adopting a conductivity image reconstruction algorithm. The method comprises the following specific steps: 1. firstly, obtaining a magnetocaloric acoustic signal with high signal-to-noise ratio; 2. reconstructing the obtained magnetocaloric acoustic signals to obtain the thermal sound source distribution of the conductive object; 3. reconstructing scalar potential space components by utilizing the thermal sound source distribution and the primary magnetic vector space components and adopting a nonlinear finite element solving method; 4. conductivity is reconstructed using the reconstructed scalar potential space component. Compared with the traditional electrical impedance imaging technology, the conductivity reconstruction method of magnetocaloric acoustic imaging realizes the simultaneous improvement of contrast and resolution, and can give out conductivity distribution. The method can reconstruct deeper tissue conductivity, realize conductivity reconstruction in one-dimensional depth direction, acquire two-dimensional B-scan images or projection plane images by combining all A-line images, acquire three-dimensional images by combining all B-scan images, and realize three-dimensional structure imaging while guaranteeing realization of quantitative reconstruction of three-dimensional biological tissue conductivity.
In addition, the system for the conductivity reconstruction method of the magnetocaloric acoustic imaging uses an excitation coil as an excitation source and utilizes an ultrasonic transducer to receive ultrasonic signals. The system used in the patent adopts short pulse width microwaves below 66ns as an excitation source and combines a point focusing ultrasonic transducer to improve the imaging resolution to the micron level.
Disclosure of Invention
The invention aims to overcome the limitation of the resolution of the traditional quantitative microwave thermo-acoustic imaging and the defect that the traditional microwave thermo-acoustic microscopic imaging method cannot quantitatively reconstruct the conductivity, and provides a quantitative microwave thermo-acoustic microscopic imaging method and a storage medium. The technical scheme of the invention is as follows:
a quantitative microwave thermo-acoustic microscopy imaging method comprising the steps of:
dividing subdomains of the solving area based on a finite element grid dividing mode, performing global coding on nodes after the subdomains are divided, and selecting a linear interpolation function to establish unknown quantity connection between the nodes; then carrying out discrete processing on the equation to be solved, namely expanding the equation to be solved by using a limited number of unknowns, and converting the original edge value problem of infinite degrees of freedom into the problem of limited degrees of freedom by using the selected linear interpolation function; and finally, carrying out forward solving and reverse solving on the discrete equation, wherein the reverse solving is to approximate a three-dimensional thermo-acoustic signal obtained through a microwave thermo-acoustic microscopic imaging system to a sound pressure signal, bring the sound pressure signal into a wave equation to solve the absorption energy density, and then obtain the conductivity reconstruction according to the Potentilla theorem.
Further, the step of acquiring the three-dimensional thermo-acoustic signal specifically includes the following steps:
in a microwave thermo-acoustic microscopic imaging system (the microwave thermo-acoustic microscopic imaging system is provided and built by the team (application publication number is CN 114587326A)), a short pulse width microwave is utilized to radiate a biological tissue to be detected, the tissue absorbs the temperature rise of microwave energy to generate a thermo-induced ultrasonic signal outwards, and the three-dimensional thermo-acoustic signal is received through the reflection scanning of point focusing ultrasonic detectors distributed around the tissue.
Further, the finite element-based grid division method divides the subdomains of the solving area, and specifically includes: the grid division mode based on finite elements is to divide the area to be solved into finite small units, and in the two-dimensional problem, the units divided by the subdomains are small triangles or rectangles; in the one-dimensional microscopic imaging problem, the solving area (0,l) is divided into small areas with short line segments, let l denote the length of the e-th unit, M denote the total number of units, and only global coding is performed without introducing local coding for reconstruction.
Further, the selecting a linear interpolation function specifically includes:
to simplify the problem, linear interpolation is used to build a relationship of the unknown quantity phi (x) between nodes:i denotes the corresponding node (where i=1, 2), where N 1 and N2 As an interpolation function, it can be expressed as:
wherein ,x1 and x2 N is the position of the ith node in each linear unit i (x j )＝δ ij ，δ ij Represents a pulsed excitation signal, delta when i=j ij =1; when i+.j, delta ij ＝0。
Further, the discrete processing for solving the equation specifically includes:
firstly, galerkin's method is adopted for thermal acoustic wave equationPerforming finite element discrete processing to obtain the following discrete forms:
wherein P is the sound pressure generated at r at time t; c (C) 0 Is the sound velocity beta e Is the volume expansion coefficient, C p Is specific heat capacity, J (t) =delta (t-t 0 ) A microwave pulse function at the moment t is assumed;representing the gradient of the interpolation function,/->Represents the gradient of the sound pressure, l represents the length of the e-th element, < >>To absorb energy density;As normal vector, finite element absorption boundary isAnd is directed at sound pressure P and absorbed energy density->Performing discrete treatment:
wherein m is the number of nodes, k is the number of nodes, and N k Representing the function of the interpolation as such,the discretization equation form of the thermoacoustic wave equation finally obtained through bringing in and simplifying the absorption energy density is as follows:
wherein ,K. c, M, B each represents a finite element meshA matrix.
For the first order deviation of the sound pressure p from time t, is->Is the second order bias of sound pressure p to time t;
secondly, the Helmholtz equation is adopted by Galerkin's methodPerforming finite element discrete processing to obtain:
wherein ,Es Representing the electric field, E s,i Mu, the electric field distribution at the ith position r For relative permeability, a constant value is considered in biological tissue; epsilon r Is equivalent dielectric constant; k is wave number;
substituting boundary conditions Bayliss and Turkell boundary conditions: whereinFor the scattered field, α, β are parameters about radial loss γ, and the discretization equation of the final helmholtz equation is:
[A]{E S }＝[B]
wherein the incident fieldA. B represent a finite element mesh matrix, respectively.
Further, the discrete equation is solved forward and the three-dimensional thermo-acoustic signal is used for solving in the reverse direction, so that conductivity reconstruction is obtained, and the specific solving steps are divided into two steps:
the first step is to respectively carry out forward and reverse solution according to the thermoacoustic wave equation of discrete processing to obtain the absorption energy density
(1) Forward solving: given an initial value of the absorbed energy densityObtaining sound pressure p c ；
(2) Inverse solution, i.e. sound pressure p, of the three-dimensional thermo-acoustic signal to be obtained o For absorbing energy densityIs solved by (1): here the sound pressure p o Understanding as a function of absorbed energy density, the taylor expansion arrangement can yield the following formula:
wherein ,update vectors for the absorbed energy density;
the second step obtains the total field distribution E according to the Helmholtz equation of the discrete processing s According to the Potentilla theorem, the following relations exist among the absorbed energy density, the conductivity and the electric fieldAnd obtaining the conductivity on a line through continuous fitting, namely forming an A-line conductivity reconstruction image, so as to realize quantitative values on one-dimensional depth.
Further, the specific steps of the second step are as follows:
(1) given an initial conductivity sigma 0 Is brought intoTo obtain->
(2) Comparing the first step andIf the error between the two is not satisfied, updating +.>
(3) Solving the updated sigma repeatedly for the total field distribution E s And absorbed energy densityUp to-> andThe error between them meets the requirements.
An electronic device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, the processor implementing the quantitative microwave thermo-acoustic microscopy imaging method of any one of the claims when the program is executed.
A non-transitory computer readable storage medium having stored thereon a computer program which when executed by a processor implements the quantitative microwave thermo-acoustic microscopy imaging method of any of the claims.
A computer program product comprising a computer program which, when executed by a processor, implements a quantitative microwave thermo-acoustic microscopy imaging method according to any one of the claims.
The invention has the advantages and beneficial effects as follows:
the method can quantitatively reconstruct the conductivities of various samples, and has important significance in accurately diagnosing diseases and preventing disease deterioration in the biomedical field because the conductivities in electromagnetic parameters are directly related to tissue function information such as hemoglobin concentration, water content and the like.
The method is based on finite element solving of a thermoacoustic wave equation and a Helmholtz equation to achieve conductivity reconstruction in a one-dimensional depth direction, a two-dimensional B-scan image or a projection plane image can be obtained by combining all the A-line images, then a three-dimensional image can be obtained by combining all the B-scan images, and three-dimensional structure imaging is achieved while achieving three-dimensional biological tissue conductivity quantitative reconstruction. The method can overcome the limitation of the resolution of the traditional quantitative microwave thermo-acoustic imaging and the defect that the conductivity cannot be quantitatively reconstructed by the traditional microwave thermo-acoustic microscopic imaging method.
Drawings
Fig. 1 is a one-dimensional conductivity reconstruction graph. FIG. 1 (a) single target conductivity initial set-up graph; (b) reconstructing a single target one-dimensional map based on finite elements; (c) a dual target conductivity initial set-up map; (d) reconstructing a dual-target one-dimensional map based on finite elements;
fig. 2 is a two-dimensional conductivity reconstruction graph of each section of a brine pipe. FIG. 2 (a) is a diagram of a brine pipe; (b) reconstructing an x-y plane map by a microwave thermo-acoustic microscopic imaging method; (c) Reconstructing an x-y plane map based on a finite element quantitative microwave thermo-acoustic microscopic imaging method; (d) Reconstructing an x-z plane image by a microwave thermo-acoustic microscopic imaging method; (e) Reconstructing an x-z plane map based on a finite element quantitative microwave thermo-acoustic microscopic imaging method; (f) reconstructing a y-z plane map by a microwave thermo-acoustic microscopic imaging method; (g) Reconstructing a y-z plane map based on a finite element quantitative microwave thermo-acoustic microscopic imaging method;
fig. 3 is a flow chart of a method of providing a preferred embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and specifically described below with reference to the drawings in the embodiments of the present invention. The described embodiments are only a few embodiments of the present invention.
The technical scheme for solving the technical problems is as follows:
the invention aims to provide a quantitative microwave thermo-acoustic microscopic imaging method, which is used for quantitatively reconstructing conductivity in the depth direction based on finite elements to obtain an A-line image, acquiring a two-dimensional B-scan image or a projection plane image by combining all the A-line images, acquiring a three-dimensional image by combining all the B-scan images, ensuring three-dimensional quantitative reconstruction of biological tissue conductivity, and realizing microscopic imaging with resolution of hundred micrometers.
In order to achieve the above purpose, the present invention provides the following technical solutions:
as shown in fig. 1 and 2, a quantitative microwave thermo-acoustic microscopy imaging method comprises the steps of:
(1) Acquiring a three-dimensional thermo-acoustic signal through a microwave thermo-acoustic microscopic imaging system;
(2) Dividing subdomains of a solving area;
(3) Selecting a proper interpolation function;
(4) Discrete processing of solving an equation;
(5) And carrying out forward solving on the discrete equation and using the three-dimensional thermo-acoustic signal for inverse solving, so as to obtain conductivity reconstruction.
Preferably, in the step (1), in the microwave thermo-acoustic microscopic imaging system, the short pulse width microwave is utilized to radiate the biological tissue to be detected, the tissue absorbs the microwave energy, the temperature rise of the microwave energy is outwards generated into a thermo-induced ultrasonic signal, and the three-dimensional thermo-acoustic signal is received through the reflection scanning of the point focusing ultrasonic detectors distributed around the tissue.
Preferably, the finite element-based grid division mode in the step (2) divides the area to be solved into finite small units, and in the two-dimensional problem, the units divided by the subdomains are usually small triangles or rectangles. In the one-dimensional microscopic imaging problem, the solving area (0, L) is divided into small areas of short line segments, L is set to represent the length of the e-th unit, M represents the total number of units, and only global coding is carried out without introducing local coding for reconstruction.
Preferably, the step (3) selects an appropriate interpolation function, and uses linear interpolation to build the relation of the unknown quantity phi (x) between the nodes in order to simplify the problem: wherein N1 and N2 As an interpolation function, it can be expressed as:
wherein ,x1 and x2 Two nodes in each linear cell. N (N) i (x j )＝δ ij When i=j, δ ij =1; when i+.j, delta ij ＝0。
Preferably, the step (4) adopts Galerkin method to solve the discrete processing of equation, and adopts Galerkin method to solve the thermal acoustic wave equation firstPerforming finite element discrete processing to obtain a discrete form:
wherein P is the sound pressure generated at r at time t; c is the speed of sound, typically about 1500m/s in biological soft tissue; beta e Is the volume expansion coefficient; c (C) p Is specific heat capacity;to absorb energy density; j (t) =delta (t- 0 t is a microwave pulse function at the moment of supposing t;The finite element absorption boundary is +.>And is directed at sound pressure P and absorbed energy density->Performing discrete treatment:
wherein m is the number of nodes, and the discretization equation form of the thermoacoustic wave action equation finally obtained through carrying-in reduction is as follows:
wherein ,
for the first order deviation of the sound pressure p from time t, is->Is the second order bias of sound pressure p versus time t.
Secondly, the Helmholtz equation is adopted by Galerkin's methodPerforming finite element discrete processing to obtain:
wherein ,Es,i Mu, for the total field distribution r For relative permeability, a constant value is considered in biological tissue; epsilon r Is equivalent dielectric constant; k is the wave number.
Substituting boundary conditions Bayliss and Turkell boundary conditions: whereinFor the scattered field, α, β are parameters about radial loss γ, and the discretization equation of the final helmholtz equation is:
[A]{E S }＝[B]
wherein the incident field
Preferably, the step (5) performs forward solution on the discrete equation and uses the three-dimensional thermo-acoustic signal in the step (1) for inverse solution, so as to obtain conductivity reconstruction. The specific solving step is divided into two steps, wherein the first step is to respectively carry out forward and reverse solving according to the thermoacoustic wave equation of the discrete processing in the step (5) to obtain the absorption energy density
(1) Forward solving: given an initial value of the absorbed energy densityObtaining sound pressure p c 。
(2) Inverse solution (three-dimensional thermo-acoustic signal to be obtained, i.e. sound pressure p o For absorbing energy densitySolution of (c): here the sound pressure p o Understanding as a function of absorbed energy density, the taylor expansion arrangement can yield the following formula:
wherein ,to absorb the update vector of the energy density.
The second step is to obtain the total field distribution E according to the Helmholtz equation of the discrete processing in the step (5) s . According to the Potentilla theorem, the following relations exist among the absorbed energy density, the conductivity and the electric fieldAnd obtaining the conductivity on a line through continuous fitting, namely forming an A-line conductivity reconstruction image, so as to realize quantitative values on one-dimensional depth. The method comprises the following specific steps:
(1) given an initial conductivity sigma 0 Is brought intoTo obtain->
(2) Comparing the first step andIf the error between the two is not satisfied, updating +.>
(3) Solving the updated sigma repeatedly for the total field distribution E s And absorbed energy densityUp to-> andThe error between them meets the requirements.
The method of the invention proves the practicability and the reliability through experiments of simulation data and actual measurement of simulated body data.
(1) Simulation conditions
The experiment adopts a dual-core CPU with a main frequency of 2.30GHz and a PC with a memory of 32GB, and the simulation is carried out under the MATALB2020a software environment.
(2) Comparison of results
The invention adopts the traditional qualitative microwave thermo-acoustic microscopic imaging algorithm to compare with the microwave thermo-acoustic microscopic imaging algorithm based on finite element quantification.
From the reconstruction results in table 2, it can be seen that: the brine concentration is 6% based on finite element quantitative microwave thermo-acoustic microscopy, the maximum value of a single target of 8.73S/m and the average value of 5.68S/m of conductivity are 8.88S/m, and the maximum value and the average value of the reconstructed conductivity are the values of the corresponding target areas. Compared with the traditional qualitative microwave thermo-acoustic microscopic imaging algorithm, the method has a good quantitative microscopic reconstruction effect.
Table 2: quantitatively reconstructing target conductivity
The system, apparatus, module or unit set forth in the above embodiments may be implemented in particular by a computer chip or entity, or by a product having a certain function.
Computer readable media, including both non-transitory and non-transitory, removable and non-removable media, may implement information storage by any method or technology. The information may be computer readable instructions, data structures, modules of a program, or other data. Examples of storage media for a computer include, but are not limited to, phase change memory (PRAM), static Random Access Memory (SRAM), dynamic Random Access Memory (DRAM), other types of Random Access Memory (RAM), read Only Memory (ROM), electrically Erasable Programmable Read Only Memory (EEPROM), flash memory or other memory technology, compact disc read only memory (CD-ROM), digital Versatile Discs (DVD) or other optical storage, magnetic cassettes, magnetic tape magnetic disk storage or other magnetic storage devices, or any other non-transmission medium, which can be used to store information that can be accessed by a computing device. Computer-readable media, as defined herein, does not include transitory computer-readable media (transmission media), such as modulated data signals and carrier waves.
It should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article or apparatus that comprises the element.
The above examples should be understood as illustrative only and not limiting the scope of the invention. Various changes and modifications to the present invention may be made by one skilled in the art after reading the teachings herein, and such equivalent changes and modifications are intended to fall within the scope of the invention as defined in the appended claims.

Claims (10)

1.一种定量微波热声显微成像方法，其特征在于，包括以下步骤：1. A quantitative microwave thermoacoustic microscopy imaging method, characterized by comprising the following steps: 基于有限元的网格划分方式对求解区域的子域划分，对子域划分后的结点进行全局编码，选择线性插值函数来建立结点间未知量的联系；然后对待求解方程进行离散处理，即待求解方程用有限个未知量展开，利用已经选择的线性插值函数把无限个自由度的原边值问题转化成有限个自由度的问题；最后对离散后的方程进行正向求解和逆向求解，其中逆向求解是把通过微波热声显微成像系统获取的三维热声信号近似为声压信号带入波动方程求解出吸收能量密度，再根据坡应廷定理获得电导率重建。The solution domain is divided into subdomains based on the finite element method. The nodes of the subdomains are globally encoded, and a linear interpolation function is selected to establish the relationship between unknowns between nodes. Then, the equations to be solved are discretized, i.e., expanded with a finite number of unknowns. The selected linear interpolation function is used to transform the original boundary value problem with infinite degrees of freedom into a problem with a finite number of degrees of freedom. Finally, the discretized equations are solved in both the forward and inverse directions. The inverse solution involves approximating the three-dimensional thermoacoustic signal obtained through a microwave thermoacoustic microscopy system as a sound pressure signal and substituting it into the wave equation to solve for the absorbed energy density. Then, the conductivity is reconstructed using Poynting's theorem. 2.根据权利要求1所述的一种定量微波热声显微成像方法，其特征在于，所述获取三维热声信号具体包括以下步骤：2. The quantitative microwave thermoacoustic microscopy imaging method according to claim 1, characterized in that acquiring the three-dimensional thermoacoustic signal specifically includes the following steps: 在微波热声显微成像系统中，利用短脉宽微波辐射待测生物组织，组织吸收微波能量温度升高向外产生热致超声波信号，通过分布在组织周围的点聚焦超声探测器反射式扫描接收三维热声信号。In a microwave thermoacoustic microscopy system, short-pulse microwaves are used to irradiate the biological tissue under test. The tissue absorbs microwave energy, its temperature rises, and it generates a thermoacoustic signal. The three-dimensional thermoacoustic signal is received by a point-focusing ultrasound detector distributed around the tissue through reflective scanning. 3.根据权利要求1所述的一种定量微波热声显微成像方法，其特征在于，所述基于有限元的网格划分方式对求解区域的子域划分，具体包括：基于有限元的网格划分方式是将待求解区域划分为有限的小单元，在二维问题中，子域划分的单元为小三角形或矩形；而在一维显微成像问题中，是将求解区域(0,l)划分成短线段的小区域，设l表示第e个单元的长度，M表示单元总数，只进行全局编码，无需引进局部编码用于重建。3. The quantitative microwave thermoacoustic microscopy imaging method according to claim 1, characterized in that the subdomain division of the solution region based on the finite element meshing method specifically includes: the finite element meshing method divides the solution region into finite small units. In two-dimensional problems, the units for subdomain division are small triangles or rectangles; while in one-dimensional microscopy imaging problems, the solution region (0,l) is divided into small regions of short line segments, where l represents the length of the e-th unit and M represents the total number of units. Only global encoding is performed, and there is no need to introduce local encoding for reconstruction. 4.根据权利要求1所述的一种定量微波热声显微成像方法，其特征在于，所述选择线性插值函数，具体包括：4. The quantitative microwave thermoacoustic microscopy imaging method according to claim 1, characterized in that the selection of the linear interpolation function specifically includes: 为了使得问题简单化采用线性插值来建立各结点间未知量φ(x)的联系：i表示对应第几个结点，i＝1,2，其中N1和N2为插值函数，可表示为：To simplify the problem, linear interpolation is used to establish the relationship between the unknowns φ(x) at each node: i represents the corresponding node number, i = 1, 2, where N1 and N2 are interpolation functions, which can be expressed as: 其中，x1和x2为在每一个线性单元中的第i个结点的位置，Ni(xj)＝δij，δij表示脉冲激励信号，当i＝j时，δij＝1；当i≠j时，δij＝0。Where x1 and x2 are the positions of the i-th node in each linear unit, and Ni ( xj ) = δij , where δij represents the pulse excitation signal. When i = j, δij = 1; when i ≠ j, δij = 0. 5.根据权利要求1所述的一种定量微波热声显微成像方法，其特征在于，所述对求解方程的离散处理，具体包括：5. The quantitative microwave thermoacoustic microscopy imaging method according to claim 1, characterized in that the discretization processing of the solution equation specifically includes: 首先采用伽辽金法对热声波动方程进行有限元离散处理，得到如下离散形式为：First, the Galerkin method was used to analyze the thermoacoustic wave equation. Finite element discretization yields the following discretized form: 其中，P为t时刻位于r处产生的声压；C0为声速，βe为体积膨胀系数，Cp为比热容，J(t)＝δ(t-t0)为假定t时刻的微波脉冲函数；表示对插值函数求梯度，表示对声压求梯度，l表示第e个单元的长度，为吸收能量密度；为法向向量，有限元吸收边界为并对声压P和吸收能量密度做离散处理：Where P is the sound pressure generated at r at time t; C0 is the sound speed; βe is the volume expansion coefficient; Cp is the specific heat capacity; and J(t)＝δ(tt 0 ) is the microwave pulse function assumed at time t. This indicates that the gradient of the interpolation function is being calculated. This represents the gradient with respect to sound pressure, where l represents the length of the e-th unit. To absorb energy density; The normal vector is the finite element absorbing boundary. And the sound pressure P and absorbed energy density were analyzed. Discrete processing: 其中m为结点数，k表示结点个数，Nk表示插值函数，表示吸收能量密度，经过带入化简最终得到热声波动方程的离散化方程形式为：Where m is the number of nodes, k represents the total number of nodes, and Nk represents the interpolation function. Representing the absorbed energy density, after substitution and simplification, the discretized equation form of the thermoacoustic wave equation is finally obtained as follows: 其中，in, K、C、M、B分别表示有限元网格矩阵；K, C, M, and B represent the finite element mesh matrix, respectively; 为声压p对时间t的一阶偏导，为声压p对时间t的二阶偏导； Let p be the first-order partial derivative of the sound pressure p with respect to time t. This is the second-order partial derivative of the sound pressure p with respect to time t; 其次采用伽辽金法对亥姆霍兹方程进行有限元离散处理得到：Secondly, the Galerkin method was used to analyze the Helmholtz equation. Finite element discretization yields: 其中，Es表示电场，Es,i为第i个位置上的电场分布，μr为相对磁导率，在生物组织中视为定值；εr为等效介电常数；k为波数；Where Es represents the electric field, Es ,i is the electric field distribution at the i-th position, μr is the relative permeability, which is considered constant in biological tissue; εr is the equivalent permittivity; and k is the wavenumber. 代入边界条件Bayliss and Turkell边界条件：其中为散射场，α，β是关于径失γ的参数，最终得到亥姆霍兹方程的离散化方程为：Substitute the boundary conditions from Bayliss and Turkell: in Let be the scattered field, and α and β be parameters with respect to radial displacement γ. The resulting discretized equation of the Helmholtz equation is: [A]{ES}＝[B][A]{E S }＝[B] 其中，入射场A、B分别为有限元网格矩阵。Among them, the incident field A and B are finite element mesh matrices, respectively. 6.根据权利要求5所述的一种定量微波热声显微成像方法，其特征在于，所述对离散后的方程进行正向求解和将三维热声信号用于逆向求解，从而获得电导率重建，具体求解步骤分为两步：6. The quantitative microwave thermoacoustic microscopy imaging method according to claim 5, characterized in that the step of solving the discretized equation in the forward direction and using the three-dimensional thermoacoustic signal for the inverse solution to obtain conductivity reconstruction is specifically divided into two steps: 第一步根据离散处理的热声波动方程分别进行正向和逆向求解获得吸收能量密度 The first step is to solve the discrete thermoacoustic wave equation in both the forward and reverse directions to obtain the absorbed energy density. ①正向求解：给定一个吸收能量密度的初始值求得声压pc；① Forward solution: Given an initial value for the absorbed energy density Calculate the sound pressure level p<sub>c</sub>; ②逆向求解，即将获得的三维热声信号即声压po，用于吸收能量密度的求解：这里把声压po理解为关于吸收能量密度的函数，泰勒展开整理可以得到下式：② Inverse solution: the obtained three-dimensional thermoacoustic signal, i.e., sound pressure p<sub>o</sub> , is used to absorb energy density. Solving for: Here, the sound pressure p<sub>o</sub> is understood as a function of the absorbed energy density. A Taylor expansion and simplification yields the following equation: 其中，为吸收能量密度的更新矢量；in, This is the updated vector for the absorbed energy density; 第二步根据离散处理的亥姆霍兹方程，获得总场分布Es，根据坡印廷定理知，吸收能量密度、电导率、电场之间存在如下关系为通过不断拟合求得一条线上的电导率，即形成A-line电导率重建图像，从而实现一维深度上的定量值。The second step involves obtaining the total field distribution Es based on the discrete Helmholtz equation. According to Poynting's theorem, the following relationship exists between the absorbed energy density, conductivity, and electric field: By continuously fitting the data, the conductivity of a line is obtained, thus forming an A-line conductivity reconstruction image, thereby achieving a quantitative value in one-dimensional depth. 7.根据权利要求6所述的一种定量微波热声显微成像方法，其特征在于，所述第二步的具体步骤为：7. The quantitative microwave thermoacoustic microscopy imaging method according to claim 6, characterized in that the specific steps of the second step are as follows: ①给定一个初始电导率σ0，带入求得 ① Given an initial conductivity σ <sub>0</sub> , substitute... Seeking ②比较第一步中求得的和之间的误差，若不满足要求，则更新 ② Compare the results obtained in step one. and If the error between them does not meet the requirements, then update. ③把更新的σ重复求解总场分布Es和吸收能量密度直到和之间的误差满足要求。③ Repeat the solution for the updated σ to obtain the total field distribution Es and the absorbed energy density. until and The error between them meets the requirements. 8.一种电子设备，包括存储器、处理器及存储在所述存储器上并可在所述处理器上运行的计算机程序，其特征在于，所述处理器执行所述程序时实现如权利要求1至7任一项所述定量微波热声显微成像方法。8. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, when the processor executes the program, it implements the quantitative microwave thermoacoustic microscopy imaging method as described in any one of claims 1 to 7. 9.一种非暂态计算机可读存储介质，其上存储有计算机程序，其特征在于，所述计算机程序被处理器执行时实现如权利要求1至7任一项所述定量微波热声显微成像方法。9. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that, when the computer program is executed by a processor, it implements the quantitative microwave thermoacoustic microscopy imaging method as described in any one of claims 1 to 7. 10.一种计算机程序产品，包括计算机程序，其特征在于，所述计算机程序被处理器执行时实现如权利要求1至7任一项所述定量微波热声显微成像方法。10. A computer program product comprising a computer program, characterized in that, when the computer program is executed by a processor, it implements the quantitative microwave thermoacoustic microscopy imaging method as described in any one of claims 1 to 7.
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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20120123256A1 (en) * 2009-06-29 2012-05-17 Helmholtz Zentrum München Deutsches Forschungszentrum Für Gesundheit Und Umwelt (Gmbh) Thermoacoustic imaging with quantitative extraction of absorption map
CN114587326A (en) * 2022-04-07 2022-06-07 重庆邮电大学 Microwave thermoacoustic microscopy imaging system and method

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20120123256A1 (en) * 2009-06-29 2012-05-17 Helmholtz Zentrum München Deutsches Forschungszentrum Für Gesundheit Und Umwelt (Gmbh) Thermoacoustic imaging with quantitative extraction of absorption map
CN114587326A (en) * 2022-04-07 2022-06-07 重庆邮电大学 Microwave thermoacoustic microscopy imaging system and method

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
LEI YAO等: ""Quantitative microwave-induced thermoacoustic tomography"", 《MEDICAL PHYSICS》, vol. 37, no. 7, 28 June 2010 (2010-06-28), pages 3752 - 3759, XP012144848, DOI: 10.1118/1.3456926 *

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