CN111067524B

CN111067524B - Method for estimating average dielectric property of microwave breast imaging

Info

Publication number: CN111067524B
Application number: CN201911369741.6A
Authority: CN
Inventors: 肖夏; 刘雨
Original assignee: Tianjin University
Current assignee: Tianjin University
Priority date: 2019-12-26
Filing date: 2019-12-26
Publication date: 2021-12-03
Anticipated expiration: 2039-12-26
Also published as: CN111067524A

Abstract

The invention relates to a method for estimating the average dielectric properties of microwave breast imaging, comprising the following steps: stretching each breast MRI source image, discretizing each tissue of the breast, adding a layer of skin by taking the boundary contour of the breast as a reference, and establishing a three-dimensional breast model by interpolation processing; setting a tumor position and a tumor radius in a three-dimensional breast model, arranging antenna arrays on the surface of skin to replace point sources, sequentially transmitting signals by each antenna, receiving the signals by other antennas, and carrying out imaging processing on all received signals by using a confocal algorithm; constructing an improved focus quality metric index; determining an objective function, namely an image signal-to-clutter ratio SCR; and solving the maximum value of the SCR of the microwave breast image to obtain the corresponding average dielectric constant of the breast.

Description

Method for estimating average dielectric property of microwave breast imaging

Technical Field

The invention belongs to the technical field of biomedical detection, and relates to a method for estimating the average dielectric property of microwave breast imaging based on an image quality metric index.

Background

Mammary gland tumor is the malignant tumor disease with the highest incidence rate in women, and the mortality rate is the first of the mortality rates of the malignant tumors in women. The diagnosis of early breast tumors is of decisive significance for improving the treatment rate of breast diseases and the long-term survival rate of patients. The conventional detection methods for early breast cancer include mammography, ultrasonic imaging technology, computed tomography, magnetic resonance imaging technology, thermal imaging detection and the like, but all of the methods have certain disadvantages, such as radiation damage to human body, low imaging contrast, high cost and the like. The principle of detecting breast cancer by using ultra-wideband electromagnetic waves lies in that different biological tissues have different absorption, reflection and transmission characteristics of the electromagnetic waves, so that the electromagnetic field generated when pulse signals transmitted by an antenna are transmitted in breast tissues can reflect rich information of malignant tissues. Confocal microwave imaging for breast cancer detection relies on accurate knowledge of the average dielectric properties of a particular breast of a patient. After the average dielectric property is accurately estimated, the microwave signals are subjected to coherent superposition at the tumor part to generate a clear microwave image. Conversely, if the average dielectric property estimate is inaccurate, a blurred, unfocused image may be reconstructed, possibly masking cancerous lesions.

A Focal Quality Metric (FQMs) is an image Quality metric for estimating the degree of focus of an entire image. The core indexes for evaluating the quality of the microwave image in the photoelectric imaging system include signal-to-noise ratio, contrast and the like. The signal-to-noise ratio is provided on the basis of radar detection, and a series of factors in the process of reaching a detector from the background characteristic of a target through a transmission environment and the like are integrated for calculation.

The invention utilizes an improved focus quality metric and image Signal-to-noise Ratio (SCR) to accurately estimate the average dielectric properties of microwave breast imaging.

Disclosure of Invention

It is an object of the present invention to provide a method of estimating the average dielectric properties of microwave breast imaging based on an image quality metric. The technical scheme of the invention is as follows:

a method of estimating average dielectric properties for microwave breast imaging, comprising the steps of:

(1) and stretching the breast MRI source image, discretizing each tissue of the breast of the source image, and adding a layer of skin by taking the boundary contour of the breast as a reference to prepare a breast simulation model.

(2) Setting a tumor position and a tumor radius in a breast simulation model, performing electromagnetic parameter assignment on each tissue, laying an antenna array on the skin surface to replace with a point source, sequentially transmitting signals by each antenna, receiving the signals by other antennas, performing imaging processing on all received signals by using a confocal algorithm, setting different dielectric constant values for the breast simulation model, and obtaining a plurality of corresponding confocal images;

(3) constructing an improved focus quality metric phi_MF：

I'＝I*M (1)

Where I' is the image after linear convolution, M is the linear convolution kernel, X, Y are the image size, F_x,y(m, n) is the value at (m, n) of an 8 × 8 Discrete Cosine Transform (DCT) sub-block centered at (x, y);

(4) determining an objective function, namely an image signal-to-clutter ratio SCR:

wherein alpha is_TIs the maximum energy of the tumor region, alpha_BIs the maximum of energy except for the tumor region;

(5) calculating phi corresponding to each image according to the obtained confocal images_MFAnd SCR to obtain dielectric constant ε_r-φ_MFAnd ε_r-SCR curves and normalization processing;

(6) observing the curve after normalization to obtain the dielectric constant value epsilon when the signal-to-noise ratio SCR is equal to 1_r1In epsilon_r∈[ε_r1-0.5,ε_r1+0.5]Within the interval of (1), take phi_MFE corresponding to the minimum value of_rMFThen the mean dielectric constant of the breast simulation model is ε_rMF。

Drawings

FIG. 1 Breast MRI Source map

FIG. 2 breast model tumor location and antenna location map

FIG. 3 dielectric constant ε_rPhi and phi_MFCurve of relationship with SCR

Figure 4 tumor imaging

Detailed Description

The invention is described below with reference to the figures and examples.

(1) FIG. 1 is a breast MRI source image, first stretching a picture to 600 × 600 pixels to make each pixel point in the picture correspond to an FDTD grid, which is performed in MATLAB, first reading in a source image only including the picture itself, converting it into a gray value matrix, then stretching the picture by using an imbesize command, discretizing each tissue of the source image breast, adding a layer of skin based on the boundary contour of the breast, considering only one breast, and cutting out the right breast as a simulation model

(2) The tumor position (43mm, 23mm) and tumor radius (3 mm) were set in the breast, and electromagnetic parameters were assigned to each tissueThe method comprises the steps of arranging antenna arrays on the surface of the skin, replacing the antenna arrays with point sources (as shown in figure 2), sequentially transmitting signals by each antenna, receiving the signals by other antennas, imaging all the received signals by using a confocal algorithm, and setting the dielectric constant value range to be more than or equal to epsilon and less than or equal to 5_rAt most 23, sampling interval is 0.1, and 181 corresponding confocal images are obtained;

(3) calculating phi corresponding to each image according to the confocal images obtained in the step (2)_MFAnd SCR to obtain dielectric constant ε_r-φ_MFAnd ε_r-SCR relation curve and normalization (as shown in fig. 3);

(4) observing fig. 3, the value of the dielectric constant epsilon is obtained when the signal-to-noise ratio SCR is 1_r112.2 at ε_r∈[11.7,12.7]Within the interval of (1), take phi_MFE corresponding to the minimum value of_rThe average dielectric constant of this breast model is 12.1, 12.1.

(5) As shown in FIG. 4, ε is selected_rThe tumor was simulated and imaged with confocal imaging algorithm at (42.5mm, 20.5mm) similar to the preset tumor position, so the mean dielectric constant of the breast model was 12.1.

Claims

1. A method of estimating average dielectric properties for microwave breast imaging, comprising the steps of:

(1) Stretch the breast MRI source image, discretize each tissue of the breast in the source image, and add a layer of skin based on the breast boundary contour to make a breast simulation model;

(2) Set the tumor location and tumor radius in the breast simulation model, assign electromagnetic parameters to each tissue, and place an antenna array on the skin surface to replace it with a point source. The received signal is processed by the confocal algorithm, and different dielectric constant values are set for the breast simulation model to obtain the corresponding multiple confocal images;

(3) Construct an improved focus quality metric φ _MF :

I'=I*M (1)

Among them, I' is the image after linear convolution, M is the linear convolution kernel, X, Y is the image size, F _{x, y} (m, n) is an 8×8 discrete centered on (x, y) the value at (m,n) of the cosine transform (DCT) sub-block;

(4) Determine the objective function, that is, the image signal-to-noise ratio SCR:

Among them, α _T is the maximum energy in the tumor area, and α _B is the maximum energy outside the tumor area;

(5) According to the obtained confocal images, calculate the φ _MF and SCR corresponding to each image, obtain the dielectric constant ε _r -φ _MF and ε _r -SCR curves, and perform normalization processing;

(6) Observe the normalized curve, and obtain the dielectric constant value ε _r1 when the signal-to-noise ratio SCR=1, and take φ in the interval range of ε _r ∈[ε _r1 -0.5,ε _r1 +0.5] The minimum value of _MF corresponds to ε _rMF , then the average dielectric constant of this breast simulation model is ε _rMF .