Micro-scale super-resolution ultrasonic blood flow imaging method based on three-dimensional gradient modulation

Abstract

The invention discloses a microscale super-resolution ultrasonic blood flow imaging method based on three-dimensional gradient modulation, which comprises the following steps of: after carrying out tissue noise filtering on a signal after beam forming, extracting blood flow echo intensity in an original signal and calculating a blood flow track curvature and a space factor; and performing three-dimensional gradient modulation on the blood flow echo intensity according to the space factor and reconstructing an ultrasonic image. The three-dimensional gradient modulation imaging technology is utilized, blood flow intensity information is converted into space information, meanwhile, the blood vessel boundary is highlighted through the three-dimensional structure characteristics of a space diagram, and therefore the space resolution of the imaging system is improved, the three-dimensional image of the blood vessel is reconstructed, and more real and detailed visual information is provided.

Description

Technical Field

[0001] The present invention relates to a technology in the field of medical image processing, in particular to a micro-scale super-resolution ultrasonic blood flow imaging method based on three-dimensional gradient modulation. Background Art

[0002] Due to the limitations of existing ultrasonic blood flow imaging technology, it is difficult to clearly present the fine structure and subtle changes of microvessels, which affects the doctor's accurate understanding of the pathological structure. At the same time, the existing two-dimensional ultrasonic imaging lacks three-dimensional spatial information of blood vessels and cannot fully understand the spatial relationship between blood vessels and surrounding tissues, which limits the doctor's overall grasp of the lesion location and surrounding environment. Summary of the invention

[0003] In view of the above-mentioned deficiencies in the prior art, the present invention proposes a micro-scale super-resolution ultrasonic blood flow imaging method based on three-dimensional gradient modulation. The three-dimensional gradient modulation imaging technology is used to convert blood flow intensity information into spatial information, and at the same time, the blood vessel boundaries are highlighted through the three-dimensional structural characteristics of the spatial map, thereby improving the spatial resolution of the imaging system and reconstructing the stereoscopic image of the blood vessels, providing more realistic and detailed visual information.

[0004] The present invention is achieved through the following technical solutions:

[0005] The present invention relates to a micro-scale super-resolution ultrasonic blood flow imaging method based on three-dimensional gradient modulation. After filtering the tissue noise of the signal after beam synthesis, the blood flow echo intensity in the original signal is extracted and the blood flow trajectory curvature and spatial factor are calculated. Then, the blood flow echo intensity is three-dimensionally gradient modulated according to the spatial factor and an ultrasonic image is reconstructed.

[0006] The blood flow echo intensity uses a singular value decomposition method to remove background noise such as static tissues and blood vessels, and retain the flowing blood flow signal.

[0007] The singular value decomposition method is implemented by but not limited to the technology described in "Singular value decomposition of received ultrasound signal to separate tissue, blood flow, and cavitation signals" (Japanese Journal of Applied Physics, vol. 57, 2018, doi: 10.7567 / JJAP.57.07LF04).

[0008] The blood flow trajectory curvature refers to the partial derivative of the blood flow trajectory intensity in the direction parallel to the ultrasound propagation direction (x direction) and the direction perpendicular to the ultrasound propagation direction (y direction), that is, the degree of concavity of the blood flow trajectory, specifically: Among them: I is the blood flow intensity matrix, and the sign function represents the sign of the physical quantity being acted on.

[0009] When the curvature of the blood flow trajectory is positive, the blood flow trajectory is concave relative to the imaging plane; when the curvature of the blood flow trajectory is negative, the blood flow trajectory is convex relative to the imaging plane; when the curvature of the blood flow trajectory is zero, the blood flow trajectory is parallel to the imaging plane.

[0010] The spatial factor, ie, the inverse of κ of the blood flow trajectory curvature, is used for enhanced modulation of the blood flow echo intensity.

[0011] The three-dimensional gradient modulation refers to: the modulated blood flow echo intensity matrix Where: I is the original blood flow intensity matrix before modulation, μ is the spatial factor, μ max is the maximum spatial factor, and the min function represents the minimum value between two or more physical quantities.

[0012] The maximum spatial factor is obtained by, but not limited to, the following methods: a threshold is set according to different application scenarios, i.e., the maximum spatial factor μ max , thus ensuring modulation stability.

[0013] The maximum spatial factor is obtained by, but not limited to, statistical analysis of data from actual observed organs.

[0014] The blood flow echo intensity matrix can display the blood vessel contour in grayscale or in different colors according to the height of the blood vessel contour, thereby presenting a color effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a flow chart of an embodiment;

[0016] Figure 2 This is an ultrasound image of a rat brain;

[0017] In the figure: (a) B-mode imaging without three-dimensional gradient modulation algorithm processing; (b) super-resolution three-dimensional blood flow imaging after three-dimensional gradient modulation algorithm processing;

[0018] Figure 3 This is an ultrasound image of the rabbit's hind limb lymph nodes;

[0019] In the figure: (a) B-mode imaging without three-dimensional gradient modulation algorithm processing; (b) super-resolution three-dimensional blood flow imaging after three-dimensional gradient modulation algorithm processing (the white dotted line frames the area of ​​interest);

[0020] Figure 4 This is an ultrasound image of a human kidney;

[0021] In the figure: (a) B-mode imaging without 3D gradient modulation algorithm processing; (b) super-resolution stereoscopic blood flow imaging after 3D gradient modulation algorithm processing (the embedded sector area is the actual processing area);

[0022] Figure 5 It is a schematic diagram of the effect of the embodiment. DETAILED DESCRIPTION

[0023] like Figure 1 As shown, this embodiment involves a micro-scale super-resolution ultrasonic blood flow imaging method based on three-dimensional gradient modulation. After collecting and preprocessing echo data, the blood flow echo intensity matrix is ​​extracted and the blood flow trajectory curvature is calculated. Then, the blood flow echo intensity matrix is ​​reconstructed through its inverse, that is, the spatial factor and the maximum value of the spatial factor to obtain an ultrasonic image with a three-dimensional stereoscopic effect.

[0024] After specific experiments, the above method was applied to the ultrasonic blood flow imaging of rat brain, rabbit hind limb lymph nodes and human kidneys. For the rat brain and rabbit hind limb lymph nodes, a linear array probe with 128 array elements, 0.1mm array element spacing, and a center frequency of 18MHz was used for imaging, with an acquisition frequency of 16.7MHz and an acquisition frame rate of 400FPS. For the human abdominal kidney area, a convex array probe with a radius of 60mm, 128 array elements, 0.5mm array element spacing, and a center frequency of 3.5MHz was used for imaging, with an acquisition frequency of 2.5MHz and an acquisition frame rate of 300FPS.

[0025] like Figure 2 a is a B-mode image of blood vessels in the rat brain. Existing ultrasound imaging methods can roughly identify capillaries in brain tissue and their directions, but the recognition of blood vessels is low. In contrast, the blood flow image ( Figure 2 b) It can present the blood vessel area more clearly. For the blood vessels that overlap each other in the imaging plane, the blood vessels located on the upper side will be displayed in a brighter color.

[0026] like Figure 3 As shown in the figure, the above method was further applied to the B-ultrasound imaging experiment of rabbit lymph nodes, and two regions of interest (ROI) were selected from the B-ultrasound image for detailed observation. In the image not processed by the three-dimensional gradient modulation algorithm ( Figure 3a), it can be clearly seen that the microvascular structure in the ROI area is very blurred. After applying the three-dimensional gradient modulation algorithm to the corresponding ROI area ( Figure 3 b), the image quality has been significantly improved. The outlines of microvessels have become clearer and the subtle structural features have been better preserved.

[0027] The above method is further applied to human kidney B-ultrasound images, such as Figure 4 As shown in a, this is an image that has not been processed by the 3D gradient modulation algorithm. When observing the end of the blood vessel, its details are blurred and difficult to identify. The image after further application of the 3D gradient modulation algorithm is shown in Figure 4 As shown in b, by displaying the blood flow intensity as height information, the main and peripheral details of the microblood flow can be distinguished more accurately.

[0028] In order to evaluate the effect of this method on improving the three-dimensional sense of the image, the double Gaussian difference method is used to extract the gradient edges in the image, that is, the boundaries of the area where the gray value changes more slowly. When the double Gaussian difference method extracts more gradient edges, it indicates that the surface details of objects at different depths in the image are better presented, that is, the image has a stronger sense of layering and three-dimensionality. Taking the imaging results of human kidneys and rat brains before and after the application of this algorithm as an example, the proportion of gradient edge pixels in the image to the total pixels is calculated, as shown in Figure 2. Figure 5 As shown in the figure, the percentage of gradient edge pixels in the blood flow images of human kidney and rat brain before and after the application of the present invention, the data from left to right in the figure are: 1.88%, 6.52%, 4.53%, 11.82%. As can be seen from the figure, for the same set of echo data, the proportion of gradient edges in the image processed by the present invention increases significantly, showing that the processed image has richer levels. Combined with these three-dimensional hierarchical information, doctors can more clearly identify the spatial structure and boundary position of the tissue, thereby improving the accuracy of the operation and reducing damage to important structures.

[0029] In summary, compared with the prior art, the present invention significantly improves image quality.

[0030] The above-mentioned specific implementation can be partially adjusted in different ways by those skilled in the art without departing from the principle and purpose of the present invention. The protection scope of the present invention shall be based on the claims and shall not be limited by the above-mentioned specific implementation. Each implementation scheme within its scope shall be subject to the constraints of the present invention.

Claims

1. A microscale super-resolution ultrasonic blood flow imaging method based on three-dimensional gradient modulation, characterized in that: After filtering the tissue noise of the beamformed signal, the blood flow echo intensity in the original signal is extracted and the blood flow trajectory curvature and spatial factor are calculated. Then, the blood flow echo intensity is three-dimensionally gradient modulated according to the spatial factor and the ultrasound image is reconstructed.

2. The microscale super-resolution ultrasonic blood flow imaging method based on three-dimensional gradient modulation according to claim 1 is characterized in that: The blood flow echo intensity uses a singular value decomposition method to remove background noise such as static tissues and blood vessels, and retain the flowing blood flow signal.

3. The microscale super-resolution ultrasonic blood flow imaging method based on three-dimensional gradient modulation according to claim 1 is characterized in that: The blood flow trajectory curvature refers to the partial derivative of the blood flow trajectory intensity in the direction parallel to the ultrasound propagation, that is, the x direction, and in the direction perpendicular to the ultrasound propagation (y direction), that is, the degree of concavity of the blood flow trajectory, specifically: Among them: I is the blood flow intensity matrix, and the sign function represents the sign of the physical quantity being acted on.

4. The microscale super-resolution ultrasonic blood flow imaging method based on three-dimensional gradient modulation according to claim 3 is characterized in that: When the curvature of the blood flow trajectory is positive, the blood flow trajectory is concave relative to the imaging plane; when the curvature of the blood flow trajectory is negative, the blood flow trajectory is convex relative to the imaging plane; when the curvature of the blood flow trajectory is zero, the blood flow trajectory is parallel to the imaging plane.

5. The microscale super-resolution ultrasonic blood flow imaging method based on three-dimensional gradient modulation according to claim 1 is characterized in that: The spatial factor, ie, the inverse of κ of the blood flow trajectory curvature, is used for enhanced modulation of the blood flow echo intensity.

6. The microscale super-resolution ultrasonic blood flow imaging method based on three-dimensional gradient modulation according to claim 1 or 5, characterized in that: The three-dimensional gradient modulation refers to: the modulated blood flow echo intensity matrix Where: I is the original blood flow intensity matrix before modulation, μ is the spatial factor, μ max is the maximum spatial factor, and the min function represents the minimum value between two or more physical quantities.

7. The microscale super-resolution ultrasonic blood flow imaging method based on three-dimensional gradient modulation according to claim 6 is characterized in that: According to different application scenarios, a threshold is set, that is, the maximum spatial factor μ max , thus ensuring modulation stability.

8. The microscale super-resolution ultrasonic blood flow imaging method based on three-dimensional gradient modulation according to claim 6 is characterized in that: The maximum spatial factor is obtained by statistically analyzing data of the actual observed organs.

9. The microscale super-resolution ultrasonic blood flow imaging method based on three-dimensional gradient modulation according to claim 1 is characterized in that: The blood flow echo intensity matrix is ​​displayed in different colors according to the height of the blood vessel contour, thereby presenting a color effect.

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