CN102846318A - Electrical impedance imaging method - Google Patents

Abstract

The invention discloses an electrical impedance imaging method, and belongs to the technical field of electrical impedance scanning and imaging. The method disclosed by the invention comprises: step 1, respectively arranging a first electrode device and a second electrode device contacting with the surface of an object to be imaged at the two opposite sides of the object to be imaged, and enabling the first electrode device and the second electrode device to apply a constant clamp force onto the object to be imaged; step 2, applying an input electric signal via the first electrode device, acquiring the output electric signal of the second electrode device, and obtaining the current distribution of the object to be imaged under the clamp force; step 3, changing the clamping forced applied on the object to be imaged by the first electrode device and the second electrode device, and repeating the step 2; and step 4, constructing the impedance image of the object to be imaged according to the current distribution difference value of the object to be imaged between two different clamp forces. Compared with the prior art, the method disclosed by the invention has the advantages of higher sensitivity, good electrode contact antifact inhibition effect, and low implementation cost.

Description

A kind of electrical impedance imaging method

Technical field

The present invention relates to a kind of electrical impedance imaging method, belong to electrical impedance scanning imaging technology (electrical impedance scanning, EIS) field.

Background technology

Since the electric conductance of Human Breast Cancer kitchen range tissue receive (impedance) greater than (less than) the mammary gland normal structure, obtained developing rapidly as basic breast cancer detection or diagnostic techniques to measure the anti-or admittance of tissue resistance.Because the impedance concept is more known by the people, so this class technology is called as electrical impedance technology.At present, non-intrusion type has been developed in the bulk measurement stage by in vitro tissue measurement, intrusive mood in bulk measurement in this field.The electrical impedance scanning imaging technology is electrical impedance technology at the Typical Representative in breast cancer detection and diagnostic application field.EIS is incorporated into the pectoralis major of electric conductivity excellence by the bar-shaped electrode of the rustless steel of holding with the constant amplitude ac voltage signal, then by all the electrode virtual earths of measuring probe with breast surface, and approximate parallel electric field of formation between pectoralis major and probe.Detect electric current by measuring probe, the electric conductance that then calculates zone to be detected is received distributions, carries out breast cancer diagnosis according to the admittance distribution.Healthy mammary gland tissue can be regarded a uniform formation as, so its admittance distributes near even distribution; When having cancerous tissue in the mammary gland, because the local phenomenon (speck effect, or local dip phenomenon) that increases of numerical value, will appear greater than normal surrounding tissue in the cancerous tissue admittance in the electric conductance in zone to be detected or the susceptance image.The EIS testing process as shown in Figure 1, expression be not have cancer tissue, the current distributions in the even tissue situation in the surveyed area.Center probe is regional owing to even tissue distributes, and forms uniform Electric Field Distribution; Around the probe, because scantily current potential guiding of current flowing, can be at first that diversity flows and the vertical area that passes the probe place.Electric current is attracted by earth potential and is flowed out by the electrode around the probe near detecting head surface (detecting head surface virtual earth) time.Even this effect causes the EIS technology that equally distributed tissue is measured, also can not get equally distributed dmittance chart picture, the image border measured value is usually greater than the central area.When existing cancer to organize in the measured zone, measurement result should be that the admittance value in picture centre zone increases, if but the amplitude that increases less than the increase amplitude of marginal area, disturbance information just may be weakened even be flooded, thereby have influence on detecting of breast carcinoma, this effect is boundary effect.What the EIS measuring process adopted is constant amplitude voltage, multiply by this constant amplitude voltage to admittance and be the measurement CURRENT DISTRIBUTION, so CURRENT DISTRIBUTION and admittance to distribute be a kind of concept of equivalence, this paper all explains to measure CURRENT DISTRIBUTION.The EIS measurement belongs to low frequency measurement, and the general measure frequency is (α and β scattering frequency range that tissue electrical quantity information is concentrated) below 20KHz, measures electric current take conductive electric current as main, and displacement current can be ignored substantially.Therefore, only consider the electric conductance effect in practice and the analysis.

1999, the TransScan company of Israel released the platform EIS breast cancer equipment-TS2000 that beats the world, and obtained the U.S. FDA mandate, can be used as the auxiliary diagnostic tool of X-ray photographic in breast cancer diagnosis.2003, associating Shanghai east shadow company of China The Fourth Military Medical University released domestic First EIS breast cancer equipment-Angelplan

And get permission to enter clinical practice through Chinese SFDA.EIS equipment all adopts the hand-held probe, all can reliably contact with breast surface in testing process for guaranteeing all electrodes on the probe, and it is too large that probe all can not design usually.However, still often be subject to the puzzlement of the pseudo-shadow of electrode contact during EIS measures.

8 * 8 the most frequently used in detecting take EIS electrode probes are as example, its boundary effect in the big or small breast cancer of difference of emulation.China female breast size distribution interval is 100-170mm, and the attitude that lies low breast thickness is between 30-60mm.The skin of breast average thickness is 5mm, and electrical conductivity is 0.01S/m.In the EIS testing process, breast is pressed through the doctor and is detected after floating, so it can be similar to and regard the square column body as, and its length of side is 100-170mm, and thickness is 30-60mm.This column is double-layer structure, and the surface is skin layer.Fig. 2 is sample calculation.Fig. 2 (a) is for diameter is the breast EIS detection model of 100mm, and having radius in the mammary gland tissue is the cancer of 10mm, and its degree of depth is 20mm; The cancer tissue conductivities is 0.7S/m, and mammary gland tissue is fat, and electrical conductivity is 0.04S/m.Fig. 2 (b) is for adopting the model after the tetrahedron element subdivision is processed.

COMSOL finds the solution eigen[value by finite element software, can obtain the probe measurement CURRENT DISTRIBUTION, concrete numerical solution process is: EIS detects by apply low frequency sinusoidal excitation (driving frequency＜20K Hz) to breast tissue, then detects electric current in breast surface.Consider that there is not the electric current accumulative effect in the inner no current of breast source simultaneously, so the Potential distribution of breast inside satisfies typical Laplace's equation:

Wherein, σ is for organizing electric conductance, and Ω represents breast to be detected,

For reaching the potential value on surface in the breast.The electrode bar that sinusoidal excitation voltage is held by the patient in the EIS testing process is introduced through pectoralis major, then flows out via the probe electrode (the equal virtual earth of electrode) of breast tissue by breast surface.Therefore, Potential distribution also need satisfy the Di Likelai boundary condition shown in the formula (2) except the eigen[value that satisfies formula (1).Di Likelai border г 1 comprises detecting head surface (comprising electrode surface and shield electrode surface) and plane, pectoralis major place, and its boundary condition is respectively U=0 and U=1.9V (EIS driving voltage amplitude).

Except border г 1, other surfaces of Ω are referred to as Newman border г 2.The peripheral material that г 2 borders contact is air, considers the electric conductance of skin much larger than air, does not therefore have bound current on this border.Be that the described Electric Field Distribution of formula (1) also needs to satisfy the Newman boundary condition shown in the formula (3) (being called again electrically isolated condition):

By finding the solution formula (1)-(3), can obtain the Potential distribution of EIS

At detecting head surface, consider that electrode (copper material) can regard perfact conductor as, then it can regard equipotential volume as, and its electric field intensity tangential component is zero.So on the contact surface of probe and breast, the electric field intensity in the tissue only has normal component.To current potential

Calculate the electric current distribution of electrode surface by formula (4), through type (5) carries out integration can obtain the CURRENT DISTRIBUTION of popping one's head in and detecting.

I=∫ _sJds (5)

The electric current that 8 * 8 electrode measurements are obtained shows the CURRENT DISTRIBUTION that can obtain popping one's head in (seeing Fig. 3 (b)) according to its correspondence position.If udder size equates with probe size, so perturbed surface (pectoralis major plane) and probe face sizableness, electric current can only flow between these two planes, so Edge fluctuation (boundary effect) almost can be ignored.Fig. 3 (a) is detecting head surface CURRENT DISTRIBUTION in such cases, the visible current disturbing information of significantly being brought by cancer.Fig. 3 (c)-3 (d) is further breast enlargement size, and probe detects the CURRENT DISTRIBUTION that obtains.Because Edge fluctuation is more obvious, the disturbance information that is brought by cancer has gradually covered trend.Impact for the objective evaluation boundary effect, this paper has defined a cancer significance evaluation index (breast cancer significance measure, BCSM), BCSM represents the probe (ratio of the meansigma methods of the electrode detection electric current on the meansigma methods of the center electrode detection electric current of N * N) and four limits of probe outermost.

Wherein, N is the electrodeplate of a certain row or column of probe, and i is the probe line index, and j is the probe column index.When N was even number, BCSM represented the ratio of meansigma methods of the electrode detection electric current on the meansigma methods of four electrode detection electric currents of center probe position and probe outermost four limits; When N was odd number, BCSM represented the ratio of meansigma methods of the electrode detection electric current on the meansigma methods of nine electrode detection electric currents of center probe position and probe outermost four limits.Specific to 8 * 8 electrode EIS probe, BCSM is defined as follows:

$\mathrm{BCSM}=(\left(\mathrm{\Σ}{I}_{i_{|\mathrm{4,5}},j_{|\mathrm{4,5}}}\right)/4)/(\left(\mathrm{\Σ}{I}_{i_{|\mathrm{0,7}},j_{|\mathrm{0,7}}}\right)/28)---\left(7\right)$

BCSM is greater than 1, and the disturbance information that the expression cancer brings might be identified in testing process; BCSM represents then that less than or equal to 1 the disturbance information that cancer brings is submerged in boundary effect, and disturbance information is difficult to be identified.Fig. 3 (a)-(d) emulation during the employing traditional method, breast size by with probe quite to progressively greater than the process of probe, BCSM numerical value has directly affected effective identification of cancer disturbance information by 1.4480 to 1.0353 rapidly declines.

Summary of the invention

The technical problem to be solved in the present invention is to solve serious boundary effect and the pseudo-shadow problem of electrode contact that exists in the existing EIS system imaging, and a kind of reliable and effective electrical impedance imaging method is provided.

The present invention specifically solves the problems of the technologies described above by the following technical solutions:

A kind of electrical impedance imaging method may further comprise the steps:

Step 1, arrange respectively and contacted the first electrode assembly of body surface to be imaged and the second electrode assembly in the relative both sides of object to be imaged, and make the first electrode assembly and the second electrode assembly treat imaging object to apply constant chucking power;

Step 2, apply input electrical signal by the first electrode assembly, and gather the output electrical signals of the second electrode assembly, obtain the CURRENT DISTRIBUTION of object to be imaged under this chucking power;

Step 3, change the first electrode assembly and the second electrode assembly are treated the chucking power that imaging object applies, and repeating step 2;

Step 4, according to the difference of the CURRENT DISTRIBUTION of object to be imaged under two different chucking powers, make up the impedance image of object to be imaged.

In order to improve the impedance image effect that finally obtains, further, the inventive method also comprises:

The impedance image of step 5, object to be imaged that step 4 is obtained is carried out filtering.For example, can adopt the methods such as mean filter, medium filtering and Wiener filtering, the present invention preferably adopts median filter method.

As preferred version of the present invention, described the first electrode assembly is identical plate electrode array with the second electrode assembly.Adopt two groups of identical plate electrodes, can use the first electrode assembly as voltage drive end (the second electrode assembly is as the virtual earth end) or use the second electrode assembly as voltage drive end (the first electrode assembly is as the virtual earth end) in order to the mammary gland impedance measurement, compare traditional EIS measuring method, can improve the focus investigation depth of mammary gland EIS more than one times (the breast lesion investigation depth of traditional E IS technology is for only about 3cm)

Compared to existing technology, the inventive method has following beneficial effect:

One, imaging sensitivity is higher: adopting the BCSM numerical value of the impedance image of the inventive method acquisition is more than 4 times of traditional E IS image, and disturbance information is easier to be identified;

Two, constant pressure in the measuring process can be avoided the problem of the pressure instability in the traditional E IS hand hold transducer measuring process, overcomes the pseudo-shadow problem of its electrode contact;

Three, the present invention adopts the double-face electrode array to carry out impedance measurement, compares traditional E IS and can improve the focus investigation depth more than one times;

Four, the inventive method is owing to the term harmonization (such as contact situation, probe pressure etc.) that can guarantee in the measuring process, need not adopt multichannel collecting and/or high speed acquisition to guarantee the concordance of measuring process to reduce as far as possible Measuring Time as traditional E IS, and can take to compare EIS system measurement passage (even single channel) still less, can significantly reduce the hardware cost of EIS system, improve the portability of equipment.

Description of drawings

Fig. 1 is that mammary gland EIS checks sketch map;

Fig. 2 (a) is the EIS detection model;

Fig. 2 (b) is gridding methods corresponding to EIS detection model;

Fig. 3 is that the breast surface EIS of different size detects the CURRENT DISTRIBUTION that obtains; Wherein, Fig. 3 (a) is breast and probe equal and opposite in direction, BCSM=1.4480; Fig. 3 (b) is 100mm for udder size, BCSM=1.0898; Fig. 3 (c) is 130mm for udder size, BCSM=1.0667; Fig. 3 (d) is 170mm for udder size, BCSM=1.0353;

Fig. 4 (a) is DFPD-EIS system structure sketch map of the present invention;

The plate electrode array sketch map that Fig. 4 (b) adopts for DFPD-EIS of the present invention system;

Fig. 4 (c) is the circuit block diagram of DFPD-EIS of the present invention system;

Fig. 5 is the situation of movement sketch map of cancer in the rear mammary gland tissue of pressurization;

Fig. 6 is gridding methods corresponding to DFPD-EIS measurement structure of the present invention;

Fig. 7 is the DFPD-EIS measuring results under the not mobile situation of cancer; Wherein, Fig. 7 (a) is for measuring CURRENT DISTRIBUTION, BCSM=1.5354 before the supercharging; Fig. 7 (b) measures CURRENT DISTRIBUTION, BCSM=1.7995 for after the supercharging; Fig. 7 (c) is the CURRENT DISTRIBUTION of differential pressure measurement, BCSM=11.1312; Fig. 7 (d) is the CURRENT DISTRIBUTION of the differential pressure measurement of medium filtering after processing, BCSM=11.1237;

Fig. 8 is that cancer is accompanied by tissue and suitably moves down DFPD-EIS measuring results under the situation; Wherein, Fig. 8 (a) is for measuring CURRENT DISTRIBUTION, BCSM=1.5354 before the supercharging; Fig. 8 (b) measures CURRENT DISTRIBUTION, BCSM=1.6658 for after the supercharging; Fig. 8 (c) is the CURRENT DISTRIBUTION of differential pressure measurement, BCSM=5.8531; Fig. 8 (d) is the CURRENT DISTRIBUTION of the differential pressure measurement of medium filtering after processing, BCSM=5.9912.

The specific embodiment

Below in conjunction with accompanying drawing technical scheme of the present invention is elaborated:

Electric impedance imaging system of the present invention is (for the purpose of difference, follow-up electrical impedance imaging method of the present invention is referred to as two-sided pressure reduction electrical impedance scanning imaging method: dual-face pressure difference electrical impedance scanning, be called for short DFPD-EIS) comprise two identical plane electrode arrays that shown in Fig. 4 (a), are arranged at the breast both sides, each plane electrode array comprises 960 equally distributed electrodes.Consider the breast diameter of Chinese women in 100-170mm, female breast can be similar to regards a hemispherical form as.The structure of similar x-ray molybdenum target breast imaging, breast is subject to the pressure of two plate electrode arrays, and its form will be changed to a similar cuboid by hemispherical.The breast diameter capping of Chinese women calculates according to 170mm, so the length of side of plane electrode array is got 170mm.Its volume is calculated as 1,285,568mm3 by hemisphere.Mammary gland thickness was generally at 12.5 ~ 71.5mm when breast x-ray molybdenum target checked, because the larger thickness of breast is larger, therefore the corresponding one-tenth-value thickness 1/10 of getting is 71.5mm.According to constancy of volume in the measuring process, can estimate the wide 108mm that is.In conjunction with the EIS probe designs, electrode length of side 3mm, interval 1mm, shield electrode bandwidth 7mm finally adopts the plate electrode array shown in Fig. 4 (b) all around, and it is of a size of 175cm * 111cm.

The circuit block diagram of DFPD-EIS of the present invention system is shown in Fig. 4 (b), and its scanning work flow process is as follows: when adopting the array measurement of upper surface plate electrode, and S _DownSwitch is upwards closed, and 960 electrodes and the shield electrode of whole lower surface plate electrode array all connect driving voltage; S _TopSwitch is closed downwards, the equal ground connection of all electrodes and shield electrode, and then all electrodes of upper surface are upwards closed one by one, and the high-speed a/d acquisition channel is finished the current detecting of 960 electrodes one by one.Any time, only have the switch of an electrode upwards closed on the upper surface, all the other all are in ground state.After all electrode measurements of upper surface are finished, enter the lower surface measurement links.S _DownSwitch is closed downwards, S _TopSwitch is upwards closed, and all the other processes are identical with the upper surface electrode measuring process.

In order further to make fully contacting between plate electrode array and the tissue, can the conducting medium layer be set at described plate electrode array and the contacted one side of object to be imaged, the aqueous high molecular gels such as preferred ultrasonic coupling agent.

When adopting above-mentioned DFPD-EIS system to measure, at first once increase the measurement before the pressure, then suitably increase pressure and carry out measurement second time.After increasing pressure, mammary gland thickness can dwindle, and its principle as shown in Figure 5.If mammary gland thickness is reduced into h-Δ h by h, the position of cancer also can change in this course.Specifically, the three types nothing but of the cancer change in location in this process.The first situation, the cancer mobility is very poor, and the position does not change fully; The second situation, the cancer mobility is accompanied by and organizes downward synchronizing moving Δ h not as good as normal structure ₁, Δ h ₁＜Δ h; The third situation, the cancer mobility is fine, directly is accompanied by to organize downward synchronizing moving Δ h.Make a concrete analysis of as follows: from the upper surface measurement electrode, first and second kinds of situations are that distance reduces between cancer and the measurement electrode, reduce distance and are Δ h and Δ h ₁From the lower surface measurement electrode, the third situation also shows as between cancer and the measurement electrode apart from reducing Δ h.Therefore, from the differential pressure measurement angle of DFPD-EIS, these three kinds of situations can be classified as a kind of situation, i.e. along with the reducing of mammary gland thickness, the distance between cancer and the measurement electrode diminishes after the supercharging, and decrease is mammary gland thickness decrease to the maximum.

As can be known, the electric current that EIS measures can be expressed as according to existing document (Zhang Feng etc., " based on breast carcinoma automatic diagnosis and the parameter extraction of electrical impedance scanning imaging ", automatization's journal the 5th phase of 38 volumes):

I=I ₀[1+k(3d ²-(x ²+y ²+d ²))/(x ²+y ²+d ²) ^5/2]

$k=\frac{{\mathrm{\σ}}_1/{\mathrm{\σ}}_2-1}{{\mathrm{\σ}}_1/{\mathrm{\σ}}_2+2}{a}^3---\left(8\right)$

Wherein, I ₀For from the longer-distance electric current of cancer projected position, x, y, d are respectively horizontal parameter and the depth parameter of cancer, σ ₁For cancer is organized electric conductance, σ ₂Be cancer surrounding tissue electric conductance, α is the cancer radius.Suppose that cancer is positioned at the center probe position, at the projection centre of cancer, i.e. x=y=0.Can get I=I according to formula (8) ₀[1+2k/d ³]; Beyond cancer upright projection scope, get one away from focus central point, i.e. x=y〉the d place, in like manner can get electric current I=I ₀The BCSM that can get thus the cancer disturbance estimates and is about 1+2k/d ³And α＜d (cancer is with the spheroid analysis, and its radius is certainly less than the cancer degree of depth), so the BCSM that EIS detection method cancer forms can be greater than 3, this point consistent with experimental result (seeing Fig. 3 for details).

Formula (8) is carried out differential at cancer depth direction d, can get

$I^{\′}\left(d\right)=I_{0}k\frac{d({9x}^2+9y^2-{6d}^2)}{{(x^2+y^2+d^2)}^{7/2}}---\left(9\right)$

Therefore, compare with tissue thickness hour when the focus change in depth, can obtain pressure differential partial image I (Δ d) by the differential approximation formula

$I\left(\mathrm{\Δd}\right)=I(d-\mathrm{\Δd})-I\left(d\right)=I^{\′}\left(d\right)(-\mathrm{\Δd})=I_{0}k\frac{d({9x}^2+{9y}^2-6d^2)}{{(x^2+y^2+d^2)}^{7/2}}(-\mathrm{\Δd})---\left(10\right)$

In the projection centre of cancer, namely x=y=0 can get I=I according to formula (10) equally ₀K (6/d ⁴) (Δ d); Beyond cancer drop shadow spread, get x=y〉the d place, can get electric current I → 0; This shows that BCSM that two-sided pressure reduction EIS system (DFPD-EIS) forms by the cancer disturbance is obviously greater than traditional EIS mode.

In order to verify the effectiveness of the inventive method, carried out emulation experiment as an example of the DFPD-EIS system of 16 * 16 electrodes shown in Figure 6 example.For the thick mammary gland tissue of 65mm, supercharging intensity is that mammary gland thickness reduces 2mm.Emulation very poor the and mobility of cancer movement of tissue slightly differ from two kinds of situations, namely fully not mobile the and cancer of cancer is accompanied by tissue and moves down two kinds of situations of 1mm.Fig. 7 be cancer in the supercharging measuring process, the position does not change the measurement result of situation fully.Deduct the CURRENT DISTRIBUTION (Fig. 7 (a)) that measures before the supercharging by the CURRENT DISTRIBUTION (Fig. 7 (b)) that measures after the supercharging, namely can obtain the CURRENT DISTRIBUTION image shown in Fig. 7 (c).Can find out that differential pressure measurement can effectively reflect the disturbance information of cancer, it is 11.1312 (seeing Fig. 7 (c)) that BCSM is estimated in disturbance.Because our numerical model that adopts has strictly been considered the structural design of probe, increased the boundary condition of zero current for the interval between the electrode, simulation result distributes close to the real current of EIS probe measurement more.Therefore, take electrode as least unit, there is local dip noise (seeing arrow indication among Fig. 7 (a) and Fig. 7 (c)) to a certain degree in the electric current that measures, but the current disturbing that these noises (because disturbance that interelectrode interval causes) cause unlike cancer can form the interlock in a large zone, therefore can process by filtering methods such as medium filterings and eliminate.Fig. 7 (d) has effectively protruded the disturbance information of cancer for adopting 3 * 3 window medium filterings to process pressure reduction image afterwards, has improved picture quality.The BCSM value of Fig. 7 (d) is 11.1237, and the BCSM (seeing Fig. 3, BCSM value 1.0353-1.4480) that measures than EIS improves more than 8 times.In fact, breast carcinoma is infiltrative growth, the poor mobility of general breast carcinoma focus, and therefore when pressurized, cancer can't be followed the thickness contraction process of tissue fully and move down, but also is unlikely to fully not mobile.Fig. 8 be cancer in the supercharging measuring process, cancer is accompanied by the measurement result that tissue moves down the 1mm situation, wherein, Fig. 8 (a) is for measuring CURRENT DISTRIBUTION, BCSM=1.5354 before the supercharging; Fig. 8 (b) measures CURRENT DISTRIBUTION, BCSM=1.6658 for after the supercharging; Fig. 8 (c) is the CURRENT DISTRIBUTION of differential pressure measurement (being to measure before the CURRENT DISTRIBUTION that measures after the supercharging deducts supercharging), BCSM=5.8531; Fig. 8 (d) is the CURRENT DISTRIBUTION of the differential pressure measurement of medium filtering after processing, BCSM=5.9912.Fig. 8 has reflected the effect that the DFPD-EIS system may obtain in actual applications relatively more near the situation of clinical practice.Fig. 8 (d) shows that two-sided pressure reduction formation method can protrude the cancer disturbance information really largely, and BCSM value (5.9912) is measured (seeing Fig. 3, BCSM value 1.0353-1.4480) with respect to EIS and improved more than 4 times.

Above-mentioned numerical experiment shows, the quality that DFPD-EIS formation method proposed by the invention can Effective Raise EIS image.From quantitative target BCSM, DFPD-EIS is higher for the sensitivity of cancer disturbance, and the BCSM numerical value of the image of DFPD-EIS is more than 4 times of EIS image under the square one, and disturbance information is easier to be identified.In addition, the new system that proposes can solve the pseudo-shadow problem of electrode contact in the EIS system, simultaneously because the term harmonization in can guaranteeing to measure, can take to compare EIS system measurement passage (even single channel) still less, can significantly reduce the hardware cost of EIS system, improve the portability of equipment.

Claims (5)

1. an electrical impedance imaging method is characterized in that, may further comprise the steps:

Step 1, arrange respectively and contacted the first electrode assembly of body surface to be imaged and the second electrode assembly in the relative both sides of object to be imaged, and make the first electrode assembly and the second electrode assembly treat imaging object to apply constant chucking power;

Step 2, apply input electrical signal by the first electrode assembly, and gather the output electrical signals of the second electrode assembly, obtain the CURRENT DISTRIBUTION of object to be imaged under this chucking power;

Step 3, change the first electrode assembly and the second electrode assembly are treated the chucking power that imaging object applies, and repeating step 2;

Step 4, according to the difference of the CURRENT DISTRIBUTION of object to be imaged under two different chucking powers, make up the impedance image of object to be imaged.

2. electrical impedance imaging method as claimed in claim 1 is characterized in that described the first electrode assembly is identical plate electrode array with the second electrode assembly.

3. electrical impedance imaging method as claimed in claim 2 is characterized in that described plate electrode array and the contacted one side of object to be imaged are provided with the conducting medium layer.

4. electrical impedance imaging method as claimed in claim 1 is characterized in that, also comprises:

The impedance image of step 5, object to be imaged that step 4 is obtained is carried out filtering.

5. electrical impedance imaging method as claimed in claim 4 is characterized in that, median filter method is adopted in described filtering.

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