CN112179950B - Three-dimensional bimodal electrical impedance imaging sensor and manufacturing method thereof - Google Patents
Three-dimensional bimodal electrical impedance imaging sensor and manufacturing method thereof Download PDFInfo
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- CN112179950B CN112179950B CN202011055489.4A CN202011055489A CN112179950B CN 112179950 B CN112179950 B CN 112179950B CN 202011055489 A CN202011055489 A CN 202011055489A CN 112179950 B CN112179950 B CN 112179950B
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
- G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
- G01N27/041—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
- G01N27/22—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating capacitance
- G01N27/221—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating capacitance by investigating the dielectric properties
Abstract
The invention discloses a three-dimensional bimodal electrical impedance imaging sensor and a manufacturing method thereof. The sensor provided by the invention is combined with an electrical impedance measurement system, so that the three-dimensional surface capacitance and resistance information of a hemispherical measurement area can be obtained, and the sensor is used for reconstructing the dielectric constant and conductivity distribution of the three-dimensional hemispherical area. By utilizing the difference of the electrical characteristics of the breast tissue and the cancer tissue, the sensor provided by the invention can be applied to the early screening of female breast cancer, and has the advantages of low manufacturing cost, easy carrying and no harm to human bodies.
Description
Technical Field
The invention relates to the field of three-dimensional electrical impedance imaging, in particular to a three-dimensional bimodal electrical impedance imaging sensor and a manufacturing method thereof.
Background
An Electrical Impedance Tomography (EIT) technique developed on the basis of an Electrical Impedance measurement technique is a technique aiming at reconstructing Electrical property distribution inside a human body. The EIT technology has the unique advantages of no radiation, no special environment, low cost, high cost performance, no wound, high speed and the like, is gradually developed into an important supplementary means for early screening and diagnosis of breast cancer, is expected to become a portable medical instrument used in community-level hospitals and even personal daily care, has great significance for reducing the occurrence of breast diseases and improving the survival rate of patients, and has wide application prospect.
Research shows that the biological impedance is determined by the shape, size, structure, physiology and pathology of the tissue, and when the excitation frequency is below 100MHz, the electrical conductivity and dielectric constant of malignant tumor tissue and normal tissue are obviously different. The bioimpedance characteristics of breast tissue can therefore be used to distinguish between tumor tissue and normal breast tissue. The breast tumor in the early stage of development has no obvious morphological change, and is not easy to be detected by using a general imaging detection means, but the electrical characteristics of the breast tumor are changed at the moment. I.e., functional changes in breast tissue often precede organic lesions and various symptoms. Therefore, compared with other imaging methods, the EIT technology has unique advantages for early detection of canceration, and the medical value and the application prospect of the EIT technology are reflected.
The EIT technology has been used as an auxiliary screening device for breast cancer screening, but it faces the following problems: firstly, the computation process of the inverse problem in the EIT technique has strong inadequacy, i.e. a small perturbation of the boundary measurement values may cause a huge change in the solution (electrical parameter distribution); next, although the amount of information to be measured is small and the amount of measurement data can be increased by increasing the number of electrodes, the amount of calculation increases rapidly due to the increase in the amount of data. The above difficulties cause the poor system resolution of the EIT technique.
The traditional EIT sensor mostly adopts a point electrode mode, a measured object field is mostly equivalent to a resistance model, conductivity distribution information is mainly obtained, an electrode needs to be in contact with skin so as to facilitate the injection of an excitation current into a measured area, and the excitation frequency is usually low.
In order to further improve the measurement information quantity on the basis of the traditional EIT sensor and further improve the image reconstruction quality, the invention provides a sensing technology adopting resistance/capacitance bimodal combination, which is used for measuring the conductivity and the dielectric constant of the mammary tissue respectively so as to obtain the electrical characteristic information of the mammary tissue to the maximum extent.
Disclosure of Invention
The invention aims to provide a three-dimensional bimodal electrical impedance imaging sensor and a manufacturing method thereof, which are used for solving the problems in the prior art, and can simultaneously extract the conductivity and dielectric constant information of human tissues under multiple frequencies, so that the estimation of impedance model parameters is more accurate, the image reconstruction process comprises more initial information quantity, and higher imaging quality is obtained.
In order to achieve the purpose, the invention provides the following scheme:
the invention provides a three-dimensional bimodal electrical impedance imaging sensor which comprises a hemispherical sensor support, a capacitance sensor and a resistance sensor, wherein the capacitance sensor is arranged on the hemispherical sensor support, and the resistance sensor is buckled with the semicircular support and a capacitance polar plate.
Preferably, the capacitance sensor comprises a plurality of electrode blocks, and the electrode blocks are capacitance plates and are used for measuring the dielectric constant.
Preferably, a circular pad is arranged in the center of the capacitor plate.
Preferably, the resistance sensor comprises a resistance measuring electrode, and the resistance measuring electrode adopts an electrode buckle for measuring the conductivity.
Preferably, the electrode button is fastened with the resistance sensor through the circular pad.
The manufacturing method of the three-dimensional bimodal electrical impedance imaging sensor is characterized by comprising the following steps: the method comprises the following steps:
s1, constructing a hemispherical sensor support, and attaching a flexible PCB (printed Circuit Board) outside the sensor support;
s2, spreading copper on the inner surface of the flexible PCB circuit board in the step S1, dividing to obtain a capacitor plate, and spreading copper on the outer surface of the capacitor plate for signal shielding;
s3, arranging the circular pad on the capacitor plate, and connecting the circular pad with an electrode buckle to obtain a resistance sensor;
preferably, the division is performed with the apex of the hemispherical sensor support as the center in step S1.
Preferably, in step S2, finite element simulation is used to optimize the position, shape and number of the capacitor plates.
Preferably, the position and the number of the electrode buttons are optimized according to the optimization result of the capacitor plate.
The invention discloses the following technical effects: the invention provides a three-dimensional bimodal electrical impedance imaging sensor, which has the following advantages:
the sensor provided by the invention is combined with an electrical impedance measurement system, so that the three-dimensional surface capacitance and resistance information of a hemispherical measurement area can be obtained, and the sensor is used for reconstructing the dielectric constant and conductivity distribution of the three-dimensional hemispherical area. By utilizing the difference of the electrical characteristics of the breast tissue and the cancer tissue, the sensor provided by the invention can be applied to the early screening of female breast cancer, and has the advantages of low manufacturing cost, easy carrying and no harm to human bodies. Meanwhile, the invention has no radioactivity, and avoids the harm to the body caused by the detection of breast cancer in the traditional medical industry. The three-dimensional image reconstruction algorithm based on deep learning can be realized, and the traditional reconstruction algorithm and the deep learning technology are combined, so that the quality and the speed of image reconstruction are improved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.
FIG. 1 is a biological impedance equivalent circuit model;
FIG. 2 is a schematic structural diagram of a three-dimensional bimodal electrical impedance imaging sensor of the present invention;
FIG. 3 is a flow chart of a method for manufacturing a three-dimensional bimodal electrical impedance imaging sensor according to the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
Referring to fig. 2-3, the present invention provides a three-dimensional bimodal electrical impedance imaging sensor comprising a hemispherical sensor support, a capacitive sensor and a resistive sensor.
Support the outside at the dome sensor and adhere to flexible PCB circuit board, in this embodiment, flexible PCB circuit board chooses for use the monoblock to support the dome sensor and adheres to, and the dome sensor supports and is used for supporting resistance electrode and electric capacity polar plate to adopt the hemisphere shape can laminate women's breast, improve the data acquisition accuracy.
The method comprises the steps of carrying out whole copper paving on a flexible PCB (printed circuit board), wherein conventional conductive metal copper is adopted in the embodiment, the thickness of the copper paving is 0.2mm, the PCB which is paved with copper is divided, the division is carried out transversely by taking the top point of a hemispherical sensor support as a center, namely, the top point of the hemispherical sensor support is taken as a starting point to carry out cutting along the warp direction, in the embodiment, 17 warps are cut, the arc lengths between the midpoints of the adjacent warps are the same, and the hemispherical sensor support is divided into 16 transverse cutting blocks with equal surface area; the copper surface is divided in the longitudinal direction according to the weft directions which form angles of 25 degrees, 50 degrees and 75 degrees with the connecting line of the sphere center and the bottom surface respectively, and a plurality of dividing blocks are formed on the copper surface after transverse and longitudinal division, wherein the dividing blocks are electrode blocks, a plurality of layers of electrode blocks are covered from top to bottom along the hemispherical sensor support, and a circular welding disc is arranged in the center of the capacitor polar plate. The electrode block is used as a capacitor plate for measuring the dielectric constant, and a plurality of layers of capacitor plates form a capacitor sensor.
The resistance sensor comprises a plurality of resistance measuring electrodes, in the embodiment, the resistance measuring electrodes adopt electrode buttons of core electrodes for measuring conductivity, and the electrode buttons penetrate through circular welding discs in the centers of the capacitor plates and are screwed tightly, so that the electrode buttons can be tightly buckled with the flexible PCB and the sensor supporting wall.
Aiming at the limit of a reconstruction algorithm and a sensor, the position, the shape and the number of the capacitor plates are optimized through finite element simulation, and the specific optimization process is as follows:
(1) the capacitor plates are divided into different shapes and different numbers, the divided shapes are preferably in one or a combination of a triangle, a trapezoid or a rhombus, and can also be divided into other shapes; dividing the number of the capacitor plates into integral multiples of 16 so as to form different three-dimensional models of the capacitor plates;
(2) respectively substituting different models into finite element analysis software (such as comsol, ansys and the like) to calculate a three-dimensional sensitivity matrix S and an independent capacitance matrix C for capacitance imaging; then, the condition number of the three-dimensional sensitivity matrix is calculated:
cond(S)＝||S||||S-1||,
and independent capacitance dynamic range:
Dr＝Cmax/Cmin,
wherein, CmaxRepresenting the maximum capacitance value, C, in a matrix of capacitance values CminRepresents the minimum capacitance value in the capacitance matrix C;
(3) and selecting a three-dimensional model corresponding to the calculated sensitivity matrix condition number cond (S) and the minimum value of the independent capacitance value dynamic range Dr, thereby completing the optimization of the capacitance plate.
And placing corresponding electrode buttons at the gravity center positions of the capacitor plates according to the optimization result of the capacitor plates.
The working principle is as follows: human breast is composed of various cells and extracellular substances, and its physiological and pathological states are closely related to its electromagnetic effects. Since most biological tissues exhibit diamagnetic reactions, the study of electrical properties is of great interest. The electrical properties of breast tissue are represented by the biological impedance, which reflects the conductive and dielectric properties of tissue under the action of small currents and can be used to distinguish between tumor and normal breast tissue. Fig. 1 is a bioimpedance equivalent circuit model, wherein C represents an insulation film equivalent capacitance, and R1 and R2 are equivalent resistances of intracellular fluid and extracellular fluid, respectively.
When the injected alternating current is at a low frequency, the cell membrane will act as an isolator, allowing the electrical signal to pass only through the extracellular fluid. As the excitation frequency increases, the cell membrane will act as a capacitor and the fluid within the cell will gradually participate in conducting the current. In the bimodal measurement mode adopted by the invention, the capacitance value (dielectric constant distribution) measured by using the capacitance plates corresponds to the capacitance part in fig. 1, and the resistance value (conductivity distribution) measured by using the electrode buttons corresponds to the resistance part in fig. 1.
The measuring mode of the three-dimensional bimodal electrical impedance imaging sensor adopts an adjacent excitation method and an S-shaped measuring sequence; the resistance matrix measuring mode for conductivity distribution reconstruction adopts an adjacent excitation method and an S-shaped measuring sequence, and the scheme can provide a lower measuring dynamic range, is beneficial to the design of a measuring system, obtains better image quality and can reflect the shape and the position of the cancer tissue more accurately.
The invention combines the electrical impedance imaging technology and the capacitance tomography technology, designs the resistance/capacitance bimodal sensor array, and exerts the advantages of the two technologies so as to more accurately extract the conductivity and dielectric constant information of the human tissues under a plurality of frequencies. By purposefully selecting the frequency to highlight the tissue of interest, i.e. breast tumor tissue, more accurate impedance model parameters are estimated, so that the image reconstruction process includes more initial information, and higher imaging quality is obtained.
In the description of the present invention, it is to be understood that the terms "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like, indicate orientations or positional relationships based on those shown in the drawings, are merely for convenience of description of the present invention, and do not indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and thus, are not to be construed as limiting the present invention.
The above-described embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solutions of the present invention can be made by those skilled in the art without departing from the spirit of the present invention, and the technical solutions of the present invention are within the scope of the present invention defined by the claims.
Claims (4)
1. A three-dimensional bimodal electrical impedance imaging sensor is characterized in that: comprises a hemispherical sensor support, a capacitance sensor and a resistance sensor, wherein the capacitance sensor is arranged on the hemispherical sensor support, the resistance sensor is buckled with the capacitance sensor, the capacitance sensor comprises a plurality of electrode blocks, the electrode blocks are capacitance polar plates, used for measuring the dielectric constant, a circular pad is arranged at the center of the capacitor plate and is insulated from the capacitor plate, the resistance sensor comprises a resistance measuring electrode which adopts an electrode buckle, the electrode buckle is used for measuring the conductivity, the electrode buckle is buckled with the hemispherical sensor support and the capacitor plate through the circular pad, a flexible PCB is attached to the outer side of the hemispherical sensor support, and the electrode buckle penetrates through the circular bonding pad at the center of the capacitor plate and is fastened, so that the electrode buckle is tightly fastened with the flexible PCB and the hemispherical sensor support;
the manufacturing method of the three-dimensional bimodal electrical impedance imaging sensor comprises the following steps:
s1, constructing a hemispherical sensor support, and attaching a flexible PCB (printed Circuit Board) outside the hemispherical sensor support;
s2, spreading copper on the inner surface of the flexible PCB circuit board in the S1, dividing to obtain a capacitance measuring polar plate, and spreading copper on the outer surface of the capacitance measuring polar plate for signal shielding;
and S3, arranging the circular pad on the capacitor plate, and connecting the circular pad with the electrode buckle to obtain the resistance sensor.
2. The method of manufacturing a three-dimensional bimodal electrical impedance imaging sensor according to claim 1, wherein: the division is performed with the apex of the hemispherical sensor support as the center in S1.
3. The method of manufacturing a three-dimensional bimodal electrical impedance imaging sensor according to claim 1, wherein: and in the step S2, the positions, the shapes and the number of the capacitor plates are optimized by adopting finite element simulation.
4. The method of manufacturing a three-dimensional bimodal electrical impedance imaging sensor according to claim 3, characterized in that: and optimizing the positions and the number of the electrode buttons according to the optimization result of the capacitor plate.
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