CN102846318B - 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 impedancescanning, EIS) field.

Background technology

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

1999, the TransScan company of Israel released the platform EIS breast cancer equipment-TS2000 that beats the world, and obtains U.S. FDA mandate, can be used as the auxiliary diagnostic tool of X-ray photographic in breast cancer diagnosis.2003, associating Shanghai Dong Ying company of The Fourth Military Medical University of China released domestic First EIS breast cancer equipment-Angelplan and get permission to enter clinical practice through Chinese SFDA.EIS equipment all adopts hand-held probe, and for ensureing that all electrodes on probe all can reliably contact with breast surface in testing process, it is too large that probe all can not design conventionally.However, EIS is still often subject to the puzzlement of electrode contact artifact in measuring.

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

By finite element software, COMSOL solves eigen[value, can obtain 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 the inner no current of breast source does not exist electric current accumulative effect simultaneously, therefore the Potential distribution of breast inside meets typical Laplace's equation:

Wherein, σ is for organizing electric conductance, and Ω represents breast to be detected, for in breast and surface potential value.The electrode bar that in EIS testing process, sinusoidal excitation voltage is held by patient is introduced through pectoralis major, is then flowed out by the probe electrode (the equal virtual earth of electrode) of breast surface via breast tissue.Therefore, Potential distribution, except meeting the eigen[value of formula (1), also needs to meet the Di Likelai boundary condition shown in formula (2).Di Likelai border г 1 comprises detecting head surface (comprising electrode surface and shield electrode surface) and pectoralis major place plane, 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 that the electric conductance of skin, much larger than air, does not therefore exist bound current on this border.Be that the described Electric Field Distribution of formula (1) also needs to meet the Newman boundary condition shown in formula (3) (being called again electrically isolated condition):

By solving formula (1)-(3), can obtain the Potential distribution of EIS at detecting head surface, consider that electrode (copper material) can regard perfact conductor as, 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 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 that probe detects.

I=∫ _sJds (5)

The electric current that 8 × 8 electrode measurements are obtained shows according to its correspondence position, can obtain the CURRENT DISTRIBUTION (seeing Fig. 3 (b)) of probe.If udder size equates with probe size, perturbed surface (pectoralis major plane) and probe face sizableness so, electric current can only flow between these two planes, and therefore 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 obtaining.Because Edge fluctuation is more obvious, the disturbance information being brought by cancer has covered trend gradually.For the impact of objective evaluation boundary effect, define a cancer significance evaluation index (breast cancer significance measure herein, BCSM), BCSM represents the ratio of meansigma methods with the meansigma methods of the electrode detection electric current on probe four limits of outermost of probe (N × N) center electrode detection electric current.

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

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

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

Summary of the invention

The technical problem to be solved in the present invention is to solve the serious boundary effect and the electrode contact artifact problem that in existing EIS system imaging, exist, 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, comprises the following steps:

Step 1, the first electrode assembly and the second electrode assembly that contact with body surface to be imaged are set respectively 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;

The difference of step 4, CURRENT DISTRIBUTION according to object to be imaged under two different chucking powers, builds the impedance image of object to be imaged.

In order to improve the impedance image effect finally obtaining, 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 and the second electrode assembly are identical plate electrode array.Adopt two groups of identical plate electrodes, can use the first electrode assembly as voltage drive end (the second electrode assembly is as virtual earth end) or use the second electrode assembly as voltage drive end (the first electrode assembly is as virtual earth end) in order to mammary gland impedance measurement, compare traditional EIS measuring method, can improve one times of the focus investigation depth above (the breast lesion investigation depth of traditional E IS technology is for only about 3cm) of mammary gland EIS

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 the more than 4 times of traditional E IS image, and disturbance information is more easily identified;

Two, constant pressure in measuring process, can avoid the problem of the pressure instability in traditional E IS hand hold transducer measuring process, overcomes its electrode contact artifact problem;

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

Four, the inventive method is due to the term harmonization (as contact situation, probe pressure etc.) that can ensure in measuring process, need not adopt multichannel collecting and/or high speed acquisition to ensure 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 (single channel even) still less, can significantly reduce the hardware cost of EIS system, improve the portability of equipment.

Brief description of the drawings

Fig. 1 is that mammary gland EIS checks schematic diagram;

Fig. 2 (a) is EIS detection model;

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

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

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

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

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

Fig. 5 is the situation of movement schematic diagram of the interior cancer of mammary gland tissue after 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 supercharging pre-test CURRENT DISTRIBUTION, BCSM=1.5354; Fig. 7 (b) measures CURRENT DISTRIBUTION, BCSM=1.7995 for after supercharging; The CURRENT DISTRIBUTION that Fig. 7 (c) is differential pressure measurement, BCSM=11.1312; Fig. 7 (d) is the CURRENT DISTRIBUTION of medium filtering differential pressure measurement after treatment, BCSM=11.1237;

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

Detailed description of the invention

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 to 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 are arranged at as shown in Figure 4 (a) breast both sides, each plane electrode array comprises 960 equally distributed electrodes.Consider that the breast diameter of Chinese women is 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, and therefore the length of side of plane electrode array is got 170mm.Its volume is calculated as 1,285,568mm3 by hemisphere.When breast x-ray molybdenum target checks, mammary gland thickness is generally at 12.5 ~ 71.5mm, 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 measuring process, can estimate wide is 108mm.In conjunction with EIS probe designs, electrode length of side 3mm, interval 1mm, surrounding shield electrode bandwidth 7mm, finally adopts the plate electrode array as shown in Fig. 4 (b), and it is of a size of 175cm × 111cm.

As shown in Figure 4 (b), its scanning work flow process is as follows for the circuit block diagram of DFPD-EIS system of the present invention: while 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 successively upwards closed, and high-speed a/d acquisition channel completes the current detecting of 960 electrodes one by one.Any time, on upper surface, only have the switch of an electrode upwards closed, all the other are all in ground state.After all electrode measurements of upper surface complete, enter lower surface measurement links.S _downswitch is closed downwards, S _topswitch is upwards closed, and all the other processes are identical with upper surface electrode measuring process.

The aqueous high molecular gels such as in order further to make fully contacting between plate electrode array and tissue, the one side that can contact with object to be imaged at described plate electrode array arranges conducting medium layer, preferred ultrasonic coupling agent.

While adopting above-mentioned DFPD-EIS system to measure, first once increase pressure measurement before, then suitably increase pressure and measure for the second time.Increase after 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 cancer change in location three types nothing but in this process.The first situation, cancer mobility is very poor, and position does not change completely; The second situation, cancer mobility, not as good as normal structure, is accompanied by and organizes downward synchronizing moving Δ h ₁, Δ h ₁< Δ h; The third situation, cancer mobility is fine, is directly accompanied by and organizes downward synchronizing moving Δ h.Make a concrete analysis of as follows: from upper surface measurement electrode, first and second kinds of situations are distance between cancer and measurement electrode and reduce, reduce distance for Δ h and Δ h ₁; From lower surface measurement electrode, the third situation also shows as distance between cancer and measurement electrode and reduces 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 measurement electrode diminishes after supercharging, and decrease is mammary gland thickness decrease to the maximum.

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

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

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

Wherein, I ₀for from the longer-distance electric current of cancer projected position, x, y, d is respectively horizontal parameter and the depth parameter of cancer, σ ₁for cancer is organized electric conductance, σ ₂for cancer surrounding tissue electric conductance, α is cancer radius.Suppose that cancer is positioned at center probe position, at the projection centre of cancer, i.e. x=y=0.Can obtain 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>d place, in like manner can obtain electric current I=I ₀; The BCSM that can obtain thus cancer disturbance estimates and is about 1+2k/d ³.And α <d (cancer is with spheroid analysis, and its radius is less than the cancer degree of depth certainly), so the BCSM that EIS detection method cancer forms can not be greater than 3, this point consistent with experimental result (referring to Fig. 3).

Formula (8) is carried out to differential on cancer depth direction d, can obtain

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

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

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

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

In order to verify the effectiveness of the inventive method, carry out emulation experiment as an example of the DFPD-EIS system of 16 × 16 electrodes shown in Fig. 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, completely mobile the and cancer of cancer is accompanied by tissue and moves down two kinds of situations of 1mm.Fig. 7 be cancer in supercharging measuring process, position does not change the measurement result of situation completely.Deduct the CURRENT DISTRIBUTION (Fig. 7 (a)) measuring before supercharging by the CURRENT DISTRIBUTION (Fig. 7 (b)) measuring after supercharging, can obtain the CURRENT DISTRIBUTION image shown in Fig. 7 (c).Can find out, differential pressure measurement can effectively reflect the disturbance information of cancer, and it is 11.1312 (seeing Fig. 7 (c)) that BCSM is estimated in disturbance.Because the numerical model that we adopt has strictly been considered the structural design of popping one's head in, increased the boundary condition of zero current for the interval between electrode, simulation result distributes close to the real current of EIS probe measurement more.Therefore, taking electrode as least unit, there is local dip noise (seeing arrow indication in Fig. 7 (a) and Fig. 7 (c)) to a certain degree in the electric current measuring, but these noises (disturbance causing due to interelectrode interval) current disturbing causing unlike cancer can form the interlock in a large region, therefore can be processed and be eliminated by filtering methods such as medium filterings.Fig. 7 (d), for adopting 3 × 3 window medium filterings to process pressure reduction image afterwards, has effectively protruded the disturbance information of cancer, 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) measuring than EIS improves more than 8 times.In fact, breast carcinoma is infiltrative growth, the poor mobility of general breast carcinoma focus, and therefore, in the time of pressurized, cancer can't be followed the thickness contraction process of tissue completely and move down, but is also unlikely to not move completely.Fig. 8 be cancer in supercharging measuring process, cancer is accompanied by tissue and moves down the measurement result of 1mm situation, wherein, Fig. 8 (a) is supercharging pre-test CURRENT DISTRIBUTION, BCSM=1.5354; Fig. 8 (b) measures CURRENT DISTRIBUTION, BCSM=1.6658 for after supercharging; Fig. 8 (c) is the CURRENT DISTRIBUTION of differential pressure measurement (being to measure before the CURRENT DISTRIBUTION that measures after supercharging deducts supercharging), BCSM=5.8531; Fig. 8 (d) is the CURRENT DISTRIBUTION of medium filtering differential pressure measurement after treatment, BCSM=5.9912.Fig. 8 relatively more approaches the situation of clinical practice, has reflected the effect that DFPD-EIS system may obtain in actual applications.Fig. 8 (d) shows that two-sided pressure reduction formation method can protrude 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, DFPD-EIS formation method proposed by the invention can effectively improve the quality of EIS image.From quantitative target BCSM, DFPD-EIS is higher for the sensitivity of cancer disturbance, and under square one, the BCSM numerical value of the image of DFPD-EIS is the more than 4 times of EIS image, and disturbance information is more easily identified.In addition, the new system proposing can solve the electrode contact artifact problem in EIS system, simultaneously due to the term harmonization that can ensure in measurement, can take to compare EIS system measurement passage (single channel even) 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, comprises the following steps:

Step 1, the first electrode assembly and the second electrode assembly that contact with body surface to be imaged are set respectively 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;

The difference of step 4, CURRENT DISTRIBUTION according to object to be imaged under two different chucking powers, builds 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 and the second electrode assembly are identical plate electrode array.

3. electrical impedance imaging method as claimed in claim 2, is characterized in that, the one side that described plate electrode array contacts with object to be imaged is provided with 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, described filtering adopts median filter method.