CN107647866A - A kind of electrical impedance imaging method based on deflected secondary air - Google Patents

Abstract

The invention discloses an electrical impedance imaging method based on the partial least squares method. The electrical impedance imaging method is used to perform current excitation in two modes of no-load and imaging targets respectively, and collect boundary voltages measured in the two modes. The obtained boundary voltage change matrix and sensitive matrix information are used to calculate the impedance distribution change of the target area by using the partial least squares method, so as to realize the electrical impedance image reconstruction. The method of the invention corrects the result of image reconstruction and improves the imaging quality of electrical impedance imaging.

Description

A Method of Electrical Impedance Imaging Based on Partial Least Squares Method

technical field

The invention relates to an electrical impedance imaging method based on a partial least square method, and belongs to the technical field of electrical impedance imaging.

Background technique

Electrical Impedance Tomography (EIT) technology is a new functional imaging technology. Electrical impedance imaging technology does not use nuclides or radiation, and is harmless to the human body. It can become a medical monitoring device for long-term and continuous monitoring of patients without causing damage or discomfort to patients. In addition, its equipment is low in cost and does not require a special working environment, etc., so it is an ideal non-invasive medical imaging technology and image monitoring technology with wide application prospects. It quickly became a research hotspot at the end of the 20th century.

How to realize the system's high precision, high resolution and fast convergence of the algorithm is the main problem of EIT technology at present. The research on the electrical impedance reconstruction algorithm shows that the modified Newton-Raphson method has the advantages of small reconstruction error, good convergence and low requirements on the initial value, but its disadvantages are long single-step iteration time and large storage space requirements , thus limiting its use in actual impedance image reconstruction; the equipotential line method is currently the fastest impedance reconstruction algorithm, but the results obtained due to its looseness in theoretical deduction have large errors.

Contents of the invention

The technical problem to be solved by the present invention is to provide an electrical impedance imaging method based on the partial least square method, which can effectively image disturbance targets.

The present invention adopts the following technical solutions for solving the problems of the technologies described above:

The invention provides a method for electrical impedance imaging based on the partial least squares method, and the specific steps are as follows:

Step 1: Carry out current excitation in the two modes of no-load and placing the target respectively, and collect the boundary voltage measured in the two modes respectively, and obtain the boundary voltage change matrix caused by the impedance change of the target area;

Step 2, according to the theory of sensitivity theorem, perform finite element subdivision on the imaging area, and obtain the sensitivity matrix corresponding to the finite element subdivision unit;

Step 3, according to the boundary voltage change matrix obtained in step 1 and the sensitivity matrix obtained in step 2, the impedance distribution change matrix of the target area is obtained;

In step 4, the electrical impedance imaging image is reconstructed through the impedance distribution change matrix of the target area at different frequencies.

As a further optimization scheme of the present invention, the boundary voltage change matrix V=S·Δγ, where Δγ is the impedance distribution change matrix in the target area, and S is the sensitivity matrix.

As a further optimization scheme of the present invention, in step 3, the impedance distribution change matrix of the target area is obtained by the partial least square method.

As a further optimization scheme of the present invention, before obtaining the impedance distribution change matrix in the target area by the partial least squares method, it is necessary to normalize the boundary voltage change matrix obtained in step 1 and the sensitivity matrix obtained in step 2 respectively.

As a further optimization scheme of the present invention, in step 3, the plsr.m function that comes with MATLAB is used to solve the problem.

Compared with the prior art, the present invention adopts the above technical scheme and has the following technical effects: the electrical impedance imaging method based on the partial least squares method of the present invention adopts the electrical impedance imaging method, and is respectively in two modes of no-load and placing imaging targets Perform current excitation, collect the boundary voltage measured in the two modes, and use the partial least squares method to calculate the impedance distribution change in the target area through the obtained boundary voltage change matrix and sensitivity matrix information, so as to realize electrical impedance image reconstruction. The method of the invention corrects the result of image reconstruction and improves the imaging quality of electrical impedance imaging.

Description of drawings

Fig. 1 is a flow chart of the method of the present invention.

Detailed ways

Embodiments of the invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below by referring to the figures are exemplary only for explaining the present invention and should not be construed as limiting the present invention.

Those skilled in the art can understand that, unless otherwise defined, all terms (including technical terms and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It should also be understood that terms such as those defined in commonly used dictionaries should be understood to have a meaning consistent with the meaning in the context of the prior art, and will not be interpreted in an idealized or overly formal sense unless defined as herein Explanation.

Below in conjunction with accompanying drawing, technical scheme of the present invention is described in further detail:

The invention discloses an electrical impedance imaging method based on the partial least squares method, as shown in Figure 1, the specific steps are as follows:

Step 1: Carry out current excitation in the two modes of no-load and placing the target respectively, and collect the boundary voltage measured in the two modes respectively, and obtain the boundary voltage change matrix V caused by the impedance change of the target area;

Step 2, according to the theory of sensitivity theorem, perform finite element subdivision on the imaging area, and obtain the sensitivity matrix S corresponding to the finite element subdivision unit;

Step 3, according to the boundary voltage change matrix V obtained in step 1 and the sensitivity matrix S obtained in step 2, the impedance distribution change matrix Δγ in the target area is obtained by the partial least squares method;

In step 4, the electrical impedance imaging image is reconstructed through the impedance distribution change matrix of the target area at different frequencies.

Among them, the boundary voltage change matrix V=S·Δγ.

Among them, when using the partial least squares method to solve the impedance distribution change matrix Δγ in the target area, it is necessary to first normalize the boundary voltage change matrix V and the sensitivity matrix S, and then use the plsr.m function that comes with MATLAB to solve the problem Impedance distribution change matrix in the target area.

The above is only a specific implementation mode in the present invention, but the scope of protection of the present invention is not limited thereto. Anyone familiar with the technology can understand the conceivable transformation or replacement within the technical scope disclosed in the present invention. All should be covered within the scope of the present invention, therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims (5)

1. a kind of electrical impedance imaging method based on deflected secondary air, it is characterised in that comprise the following steps that：

Step 1, current excitation is carried out under unloaded and drop target both of which respectively, and gathers measured under both of which respectively Boundary voltage, obtain the boundary voltage transformation matrices caused by the impedance variations of target area；

Step 2, it is theoretical according to sensitiveness theorem, finite element fission is carried out to imaging region, it is corresponding to obtain finite element fission unit Sensitive matrix；

Step 3, the sensitive matrix that the boundary voltage transformation matrices and step 2 obtained according to step 1 obtain obtains target area resistance Anti- changes in distribution matrix；

Step 4, by the target area distribution of impedance transformation matrices under different frequency, electrical impedance imaging image is reconstructed.

A kind of 2. electrical impedance imaging method based on deflected secondary air according to claim 1, it is characterised in that side Boundary's voltage change matrix V=S Δ γ, wherein, Δ γ is target area distribution of impedance transformation matrices, and S is sensitive matrix.

A kind of 3. electrical impedance imaging method based on deflected secondary air according to claim 1, it is characterised in that step Target area distribution of impedance transformation matrices are obtained by deflected secondary air in rapid 3.

4. according to claim 3 in a kind of described electrical impedance imaging method based on deflected secondary air, it is characterised in that Before target area distribution of impedance transformation matrices are obtained by deflected secondary air, it is also necessary to the side obtained respectively to step 1 The sensitive matrix that boundary's voltage change matrix and step 2 obtain is normalized.

A kind of 5. electrical impedance imaging method based on deflected secondary air according to claim 4, it is characterised in that step The plsr.m functions carried in rapid 3 by MATLAB are solved.