CN102894961A - Electrical impedance tomography method of self-structuring background frame - Google Patents

Abstract

The invention discloses an electrical impedance tomography method for self-constructing a background frame. The method imports a frame of EIT raw data collected from uniformly distributed electrodes on a target into a background frame construction system. In the background frame construction system, based on the EIT original The data symmetry mapping process constructs and outputs a frame of background frame, and takes the difference between the original EIT data and the background frame constructed based on the data as a known quantity through differential EIT imaging, calculates the distribution of the internal resistivity of the target by solving, and finally outputs EIT Image; it can be used to reconstruct the target internal resistivity distribution image with one frame of EIT raw data.

Description

A self-constructed background frame for electrical impedance tomography

technical field

The invention belongs to the field of electrical impedance tomography (Electrical Impedance Tomography, EIT), in particular to an electrical impedance tomography method for self-constructing background frames.

Background technique

Electrical impedance tomography applies a certain AC current on the surface of a certain fault of the target to be measured, and measures the boundary voltage on the corresponding detection electrode, and then reconstructs the target internal resistivity distribution image or the distribution of resistivity change according to a certain reconstruction algorithm. image, the former is called static EIT, and the latter is called dynamic EIT. Static EIT reconstructs the distribution image of the internal resistivity of the measured target based on a frame of data. It is a more pathological imaging method. It is easily affected by noise and it is difficult to obtain a good quality image, so it has poor practicability. However, there has always been a need in practice to obtain an image of the internal resistivity distribution of the measured target based on one frame of data. Dynamic EIT adopts the differential imaging method to reconstruct the image after making difference between two frames of measured data, which can reduce the influence of noise, so it can dynamically reflect the change of the internal resistivity of the measured target in real time. A Chinese patent application (patent number: ZL 03134598.0) discloses an electrical impedance tomography method and device for bedside image monitoring, and discloses the dynamic EIT technical solution in detail. However, the dynamic EIT can only be imaged by making a difference between two frames of data, and cannot use one frame of data to reflect the distribution of the internal resistivity of the target. Therefore, a self-constructed background frame electrical impedance tomography method is needed to reconstruct the image of the internal resistivity distribution of the target with one frame of raw data.

Contents of the invention

In view of the practical requirement of using a frame of measured data for electrical impedance tomography, the purpose of the present invention is to provide an electrical impedance tomography method for self-constructing background frames, which can reconstruct the image of the internal resistivity distribution of the target.

In order to achieve the above tasks, the present invention takes the following technical solutions:

An electrical impedance tomography method for self-constructing background frames, characterized in that the method imports a frame of EIT raw data collected from uniformly distributed electrodes on the target into the background frame construction system, and in the background frame construction system based on the original EIT The data symmetry mapping process constructs and outputs a frame of background frame, and takes the difference between the original EIT data and the background frame constructed based on the data as a known quantity through differential EIT imaging, calculates the distribution of the internal resistivity of the target by solving, and finally outputs EIT image;

Described background frame construction system is a software system, and it comprises EIT raw data import, the construction of raw data symmetry mapping matrix, raw data symmetry mapping, the construction of background frame and the output of background frame; Wherein:

The import of described EIT raw data is to import a frame of raw data collected by the EIT hardware system into the background frame construction system, and number and store the EIT raw data;

The original data symmetry mapping matrix is a matrix that stores the measurement position of a frame of EIT original data, and has 2 rows and N columns of elements, the first row stores the number of the original data whose measurement position is on the right side of the target with a symmetrical structure, and the second row The second line stores the number of the original data whose measurement position is on the left side of the target with a symmetrical structure, and the two elements in the same column are the numbers of the EIT original data with a symmetrical measurement position;

The described EIT original data symmetry mapping process is to arrange all the elements of a frame of EIT original data into a 2×N matrix according to the original data symmetry mapping matrix, and copy the elements of the first row or the second row to another one line;

The structure of the background frame is to construct a frame of complete original data as the background frame according to the numbering of the original data in the symmetrical mapping matrix after the symmetrically mapped data;

The output of the background frame is to output the constructed background frame in the file format required by EIT differential imaging.

The symmetrical measurement position is a symmetrical measurement position on the left and right sides of the target.

The measurement position is the position of two electrodes for obtaining a raw data.

The method of the present invention can realize reconstruction of target internal resistivity distribution image with one frame of EIT raw data.

Description of drawings

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

Figure 2 is a flowchart of an embodiment.

Fig. 3 is a schematic diagram of the target and electrode distribution of the embodiment.

Fig. 4 is a schematic diagram of a partial symmetrical measurement position of the embodiment.

Fig. 5 is a resistivity distribution diagram of an approximate ellipse target reconstructed by the embodiment.

Detailed ways

First of all, it should be noted that the following examples are only for those skilled in the art to further understand the present invention, the present invention is not limited to this example, all equivalent replacements and additions made by those skilled in the art according to the technical solution of the invention , also belong to the protection scope of the present invention.

Referring to Fig. 1, this embodiment provides a self-constructed background frame electrical impedance tomography method, a frame of EIT raw data collected from uniformly distributed electrodes on the target is imported into the background frame construction system, and in the background frame construction system Construct and output a frame of background frame based on the symmetry mapping process of EIT original data, and use the difference between EIT original data and the background frame constructed based on this data as a known quantity through differential EIT imaging, and calculate the distribution of the internal resistivity of the target by solving, Finally output the EIT image;

The core of the method is to construct the background frame based on the symmetry mapping process of the EIT raw data, which is realized by the background frame construction system in this embodiment. The background frame construction system is a software system whose function is to use a frame of EIT raw data to construct a background frame and output it. It includes EIT raw data import, construction of raw data symmetry mapping matrix, raw data symmetry mapping, background frame construction and background frame output.

Among them, the import of EIT raw data is used to import a frame of raw data collected by the EIT hardware system to the background frame construction system, and to number and store the EIT raw data.

The raw data symmetry mapping matrix is a matrix that stores the measurement position of a frame of EIT raw data. It has 2 rows and N columns of elements. The first row stores the number of the original data whose measurement position is on the right side of the target, and the second row stores the measurement position at the target The number of the raw data on the left, the two elements in the same column are the numbers of the EIT raw data with symmetrical measurement positions.

A target is a target with a symmetrical structure.

The measurement position is the position of the two electrodes from which a raw data is obtained.

The symmetrical measurement position is a measurement position where the left and right sides of the target are symmetrical.

EIT original data symmetry mapping is to arrange all elements of a frame of EIT original data into a 2×N matrix according to the original data symmetry mapping matrix, and copy the elements of the first row or the second row to another row.

The construction of the background frame is to use the symmetrically mapped data to construct a complete frame of original data as the background frame according to the number of the original data in the symmetrical mapping matrix.

The output of the background frame is to output the constructed background frame in the file format required by EIT differential imaging.

Differential EIT imaging uses the difference between the original EIT data and the background frame constructed based on the data as a known quantity, and calculates the distribution of the internal resistivity of the target by solving.

In this embodiment, a frame of raw data measured by a 16-electrode EIT system is used to construct a background frame and perform differential imaging, as shown in FIG. 2 . In this embodiment, a symmetrical object approximately ellipsoidal is used as the target, and its two-dimensional section is shown in FIG. 3 . The 16 EIT electrodes are numbered from 0 to 15, among which electrodes 4 and 12 are located on the symmetry axis of the target, and the other 14 electrodes are symmetrically distributed on both sides of the target. A frame of EIT raw data generated by the EIT system according to the opposite excitation-proximity measurement mode contains 192 double-type boundary voltages.

In this embodiment, the background frame construction system is a software system established by means of a third-party programming environment, and its functions are shown in the area inside the dotted line box in FIG. 2 . In this system, after data is imported, it is called and stored in the form of variables.

In this embodiment, the EIT raw data import program imports each border voltage into the background frame construction system according to the order in which the border voltages are generated, and numbers them from 1 to 192 after importing. Finally, the number and the corresponding boundary voltage are stored in the 2×192 matrix M1. The first row of the matrix M1 stores the number of the boundary voltage, and the second row stores the boundary voltage corresponding to the number.

In the EIT opposite excitation-adjacent measurement mode, except for the excitation electrode, two adjacent measurements constitute a measurement position. The symmetrical measurement position is a measurement position where the left and right sides of the target are symmetrical. Partially symmetrical measurement positions in this embodiment are shown in FIG. 4 . When the excitation signal is applied before and after the target, such as when the excitation current I is applied between electrode 4 and electrode 12, as shown in Figure 4(a), the measurement position is marked with capital letters U and numbers, such as: between electrode 5 and electrode 6 The measurement position is marked as U66; the symmetrical measurement position is marked with (*the same number), for example: the symmetrical measurement positions U66 and U79 are respectively marked as U66 (*1) and U79 (*1). When the excitation signal is applied to the symmetrical electrodes, such as when the excitation current I is applied to the electrode 3 and the electrode 11 and the same excitation current is applied to the electrode 5 and the electrode 13, as shown in Figure 4(b), there is also such a symmetrical measurement For example, when the excitation current I is applied to the electrode 3 and the electrode 11, the measurement position U50 composed of the electrode 4 and the electrode 5 and the measurement position U95 composed of the electrode 4 and the electrode 3 when the excitation current I is applied to the electrode 5 and the electrode 13 are a pair Symmetrical measurement position. Under this condition, a pair of symmetrical measurement positions is marked with (*same number) or (**same number). Apply excitation current I to other symmetrical electrodes to obtain corresponding symmetrical measurement positions.

In this embodiment, constructing the original data symmetry mapping matrix is to establish a 2×96 matrix M2, so that the first row stores the numbers of the 96 EIT boundary voltages on the right side of the target, and the second row stores the 96 EITs on the left side of the target The number of the boundary voltage, and ensure that the boundary voltage corresponding to the two numbers in the same column is obtained at the symmetrical measurement position. The symmetry mapping process of EIT raw data is to store 192 boundary voltages in matrix M1 in 2×96 matrix M3 according to the boundary voltage numbers in matrix M2, and copy the elements of the first or second row of M3 Go to another line to get matrix M4. The next step is to construct a background frame based on the matrix M4, which mainly refers to transferring each element in the 2×96 matrix M4 to the ath position in the 1×192 matrix M5 according to the corresponding number a in M2. The 192 boundary voltages of matrix M5 form a complete background frame. After the background frame is constructed, it is transformed into a file format acceptable to the reconstruction algorithm for output. The EIT differential imaging method used in this embodiment is not based on differential imaging of two frames of raw data, but uses the difference between one frame of raw data and a background frame constructed based on the raw data to estimate the internal resistivity distribution of the target. Finally, the reconstructed resistivity distribution image is displayed on a computer monitor, as shown in FIG. 5 .

Claims (3)

1. A method for electrical impedance tomography of self-constructed background frame, it is characterized in that, the method imports a frame of EIT raw data collected from evenly distributed electrodes on the target into the background frame construction system, in the background frame construction system based on The EIT original data symmetry mapping process constructs and outputs a frame of background frame. The difference between the EIT original data and the background frame constructed based on the data is taken as a known quantity through differential EIT imaging, and the distribution of the internal resistivity of the target is estimated by solving the solution. Finally, output EIT image; Described background frame construction system is a software system, and it comprises EIT raw data import, the construction of raw data symmetry mapping matrix, raw data symmetry mapping, the construction of background frame and the output of background frame; Wherein: The import of described EIT raw data is to import a frame of raw data collected by the EIT hardware system into the background frame construction system, and number and store the EIT raw data; The original data symmetry mapping matrix is a matrix that stores the measurement position of a frame of EIT original data, and has 2 rows and N columns of elements, the first row stores the number of the original data whose measurement position is on the right side of the target with a symmetrical structure, and the second row The second line stores the number of the original data whose measurement position is on the left side of the target with a symmetrical structure, and the two elements in the same column are the numbers of the EIT original data with a symmetrical measurement position; The described EIT original data symmetry mapping process is to arrange all the elements of a frame of EIT original data into a 2×N matrix according to the original data symmetry mapping matrix, and copy the elements of the first row or the second row to another one line; The structure of the background frame is to construct a frame of complete original data as the background frame according to the numbering of the original data in the symmetrical mapping matrix after the symmetrically mapped data; The output of the background frame is to output the constructed background frame in the file format required by EIT differential imaging. 2. The method according to claim 1, wherein the symmetrical measurement position is a symmetrical measurement position on the left and right sides of the target. 3. The method according to claim 1, wherein the measurement position is the position of two electrodes for obtaining a raw data.

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