A breast ultrasound ct reflection imaging method and apparatus

Abstract

The application discloses a breast ultrasound CT reflection imaging method and device, and belongs to the technical field of medical image processing. The method comprises the following steps: sequentially collecting first echo signals corresponding to each array element of a ring-shaped probe in N times of emission and reception events of a patient's breast respectively; performing redundancy reduction processing, filtering processing and receiving end delay superposition processing according to the first echo signals to obtain target echo signals corresponding to each array element in the N times of emission and reception events; calculating a normalized spatial coherence value of each imaging point of a reconstructed image according to the target echo signals corresponding to each array element, and then calculating a short-interval spatial coherence coefficient of each imaging point; and performing gray value assignment on each imaging point according to the short-interval spatial coherence coefficient of each imaging point in the reconstructed image. The improved SLSC method is applied to processing data collected by the ultrasound CT, so that the image contrast is improved, and the uniformity of the image resolution in the axial direction and the lateral direction is ensured.

Description

A breast ultrasound CT reflection imaging method and device Technical Field

[0001] This invention belongs to the field of medical image processing technology, and more specifically, relates to a method and apparatus for breast ultrasound CT reflection imaging. Background Technology

[0002] Clutter is very common in ultrasound imaging, appearing as a hazy noise artifact. It originates from the interaction between sound waves and surrounding tissues, such as reverberation, off-axis scattering, and acoustic and electronic noise. It is most easily observed in anechoic or hypoechoic areas of ultrasound images, such as breast cysts, blood vessels, and fluid-filled bladders. Ultrasound-CT reflectance imaging has potential applications in the screening and diagnosis of breast diseases, but clutter reduces image contrast and the ability to identify cysts, calcifications, and other subtle diagnostic details, increasing the difficulty of observing and measuring regions of interest.

[0003] Ultrasonic CT reflection imaging algorithms are mainly based on delay-and-sum (DAS) beamforming methods, utilizing the amplitude information of the echo signal for imaging. Traditional DAS methods are simple to operate, but clutter is very noticeable in DAS images. The Van Cittert-Zernike theorem in acoustics states that the spatial covariance of the echo signals received by each channel of an ultrasonic probe within a given time is a function of the element spacing. Based on this, the short-lag spatial coherence (SLSC) method was proposed. SLSC utilizes the spatial coherence between channels for imaging, and many studies have shown that SLSC can effectively reduce clutter and improve the contrast of the region of interest.

[0004] Therefore, applying the SLSC method to ultrasound CT reflective imaging can overcome the shortcomings of the DAS method and improve image quality. Domestic and international research on SLSC has mostly focused on linear array probes, without addressing synthetic aperture imaging with ring arrays. Due to the high complexity of the SLSC imaging method and the large number of ultrasound CT array element channels, there are currently no reports on breast ultrasound CT reflective imaging based on SLSC. Summary of the Invention

[0005] In view of the above-mentioned defects or improvement needs of the existing technology, the present invention provides a breast ultrasound CT reflection imaging method and device. Its purpose is to utilize the improved SLSC method to process the data acquired by ultrasound CT, which takes advantage of the isotropic characteristics of the ring probe, thereby improving the image contrast and ensuring the uniformity of image resolution in the axial and lateral directions, thus solving the technical problem of poor breast ultrasound CT reflection imaging effect in the existing technology.

[0006] To achieve the above objectives, according to one aspect of the present invention, a method for breast ultrasound CT reflectance imaging is provided, comprising:

[0007] S1: Sequentially acquire the first echo signal corresponding to each element of the ring probe in N transmission and reception events of the patient's breast, and perform redundancy reduction processing, filtering processing and receiver delay superposition processing on the first echo signal to obtain the target echo signal corresponding to each element in N transmission and reception events.

[0008] S2: Calculate the normalized spatial coherence value of each imaging point in the reconstructed image based on the target echo signal S(t) corresponding to each array element, and then calculate the short-interval spatial coherence coefficient of each imaging point;

[0009] S3: Assign a grayscale value to each imaging point based on the short-interval spatial coherence coefficient of each imaging point in the reconstructed image.

[0010] In one embodiment, for the transmitting array element n of the i-th transmit-receive event, the left and right sides of the transmitting array element n are retained. The first echo signal received by the array element is used as the second echo signal corresponding to the i-th transmit / receive event; the second echo signal is bandpass filtered to obtain the third echo signal; the third echo signal is subjected to receiver delay superposition operation to obtain the target echo signal S(t) corresponding to the array element n of the i-th transmit / receive event, where n∈[1, ele]. N ], ele N This refers to the number of elements in the ring probe array.

[0011] In one embodiment, the target echo signal corresponding to array element n of the i-th transmit-receive event t(m,n,p)=(d np +d pm ) / c;

[0012] Where rf(t) represents the second echo signal received by array element m at time t after being transmitted by array element n in the i-th transmit-receive event, and t(m,n,p) represents the time required for the sound wave to be reflected after being transmitted by array element n and propagating in the medium and encountering the imaging point p(x,y), and then reaching array element m; d np d pm Let n represent the distance from array element n to imaging point p(x,y) and the distance from imaging point p(x,y) to receiving array element m, respectively. Let c represent the speed of sound and m∈[1,M].

[0013] In one embodiment, M refers to the number of receiver array elements.

[0014] In one embodiment, the normalized spatial coherence value for each imaging point of the reconstructed image is:

[0015]

[0016] The value at imaging point p(x,y) is determined by the values ​​of the i-th transmit / receive event and the (i+l-th)-th transmit / receive event within the neighborhood of point p, expressed as k. x ×k y The average of the coherence values ​​of each pixel is obtained; the number of horizontal samples k x = x2 - x1 + 1, axial sample number k y =y2-y1+1,s i (x,y) and s i+l (x,y) represent the target echo signals at imaging point p(x,y) for the i-th and i+k-th emission events, respectively.

[0017] In one embodiment, the short-interval spatial coherence coefficient of each imaging point L represents the number of array elements in the maximum interval.

[0018] In one embodiment, S3 includes: setting the short-interval spatial coherence coefficient R of each imaging point in the reconstructed image to... slsc The coefficient is represented as a value in the range of 0 to 1, and is mapped to a gray value of 0 to 255.

[0019] According to another aspect of the present invention, a breast ultrasound CT reflection imaging apparatus is provided for performing the above-described breast ultrasound CT reflection imaging method, comprising:

[0020] The acquisition module is used to sequentially acquire the first echo signal corresponding to each element of the ring probe in N transmission and reception events of the patient's breast, and perform redundancy reduction processing, filtering processing and receiver delay superposition processing on the first echo signal to obtain the target echo signal corresponding to each element of the array in N transmission and reception events.

[0021] The calculation module is used to calculate the normalized spatial coherence value of each imaging point of the reconstructed image based on the target echo signal S(t) corresponding to each array element, and then calculate the short-interval spatial coherence coefficient of each imaging point;

[0022] An imaging module is used to assign grayscale values ​​to each imaging point based on the short-interval spatial coherence coefficient of each imaging point in the reconstructed image.

[0023] According to another aspect of the present invention, an electronic device is provided, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps of the above-described method.

[0024] According to another aspect of the present invention, a computer-readable storage medium is provided having a computer program stored thereon, which, when executed by a processor, implements the steps of the above-described method.

[0025] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects:

[0026] This invention calculates the normalized spatial coherence value of each imaging point in the reconstructed image based on the target echo signal S(t) corresponding to each array element, and then calculates the short-interval spatial coherence coefficient of each imaging point; the grayscale value of each imaging point is assigned based on the short-interval spatial coherence coefficient of each imaging point in the reconstructed image. This invention applies an improved SLSC method to process the data acquired by ultrasound CT, improving image contrast and ensuring the uniformity of image resolution in both the axial and lateral directions. Attached Figure Description

[0027] Figure 1 is a schematic diagram of the overall process of the present invention;

[0028] Figure 2 is a schematic diagram of the principle of the present invention;

[0029] Figure 3 is a schematic diagram of the SLSC principle of the ring probe;

[0030] Figure 4 is a flowchart illustrating a specific embodiment of the present invention;

[0031] Figure 5a is a schematic diagram of the results of breast imaging using the DAS method;

[0032] Figure 5b is a schematic diagram of the results of breast imaging using the method of the present invention;

[0033] Figure 5c is a schematic diagram of the results of breast imaging using the conventional SLSC method. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0035] As shown in Figures 1 and 2, the present invention provides a breast ultrasound CT reflection imaging method, comprising:

[0036] S1: Sequentially acquire the first echo signal corresponding to each element of the ring probe in N transmission and reception events of the patient's breast, and perform redundancy reduction processing, filtering processing and receiver delay superposition processing on the first echo signal to obtain the target echo signal corresponding to each element in N transmission and reception events.

[0037] S2: Calculate the normalized spatial coherence value of each imaging point in the reconstructed image based on the target echo signal S(t) corresponding to each array element, and then calculate the short-interval spatial coherence coefficient of each imaging point;

[0038] S3: Assign a grayscale value to each imaging point based on the short-interval spatial coherence coefficient of each imaging point in the reconstructed image.

[0039] First, considering the isotropic nature of the ring probe, the SLSC method was improved accordingly. Finally, the improved SLSC method was applied to process the data acquired by ultrasound CT, which improved image contrast and ensured the uniformity of image resolution in both the axial and lateral directions.

[0040] The breast ultrasound CT reflection imaging method provided by this invention includes the following steps:

[0041] 1. Data Acquisition: Data was acquired using a ring-probe ultrasound CT imaging system, wherein the number of probe elements was ele. N The number of transmit and receive events is N, and the number of receive channels is equal to the number of probe array elements. Array element 1 transmits sound waves, and all channels receive echo signals. This process continues until all transmit and receive events have been traversed, completing the data acquisition for a single slice.

[0042] 2. Data Preprocessing: To reduce redundant data, the transmitted signal in the i-th transmit / receive event is removed, and the left and right sides of the transmit array element are retained. The array element receives the signal, and the echo signal corresponding to the i-th transmit / receive event is obtained, where M is an even number, and its value is determined empirically within a certain range. Select from the options. Use an FIR bandpass filter to filter the data.

[0043] 3. Delay superposition operation at the receiving end: For an N-image... x ×N y For the image to be reconstructed, the echo signal corresponding to the i-th transmission and reception event is first subjected to a delay superposition operation at the receiving end, as shown in the formula:

[0044]

[0045]

[0046] Where rf(t) represents the echo signal received by array element m at time t during the i-th transmission event, and t(m,n,p) represents the time required for the sound wave emitted by array element n, propagating in the medium, being reflected after encountering imaging point p, and the reflected echo to reach array element m. t(m,n,p) is calculated using the relative relationship between distance and time. np d pm Let n represent the distance from array element n to imaging point p, and let p represent the distance from array element m to imaging point p, respectively. Let c represent the speed of sound. S(t) represents the signal at the receiver after delay and superposition during the i-th transmission event. Finally, S(t) is saved.

[0047] 4. If i≤N, repeat step 2 to preprocess the data obtained under the (i+1)th transmission event; if i>N, proceed to step 5.

[0048] 5. Short-interval spatial coherence operation at the transmitting end: After completing the delay superposition operation at the receiving end for all transmission events, a short-interval spatial coherence operation is performed at the transmitting end. The principle of short-interval spatial coherence is shown in Figure 3. The value at the imaging point p(x,y) is determined by k values ​​in the neighborhood of point p from the i-th transmission event and the (i+l)-th transmission event. x ×k y The average of the pixel coherence values ​​is obtained. The normalized spatial coherence calculated between emission events with an element spacing of l is as follows:

[0049] Normalized spatial coherence

[0050] Wherein, the number of horizontal samples k x = x2 - x1 + 1, axial sample number k y =y2-y1+1,s i (x,y) and s i+l (x,y) represents the signal after delay at the receiver at the imaging point p(x,y) of the i-th and (i+l)-th transmission events. When the number of lateral samples is 0... The calculation formula is the same as that for conventional SLSC. Short-interval spatial coherence coefficient R slsc Depend on Integrating from 1 to L yields:

[0051]

[0052] Where L represents the number of array elements with the maximum spacing, and its value is usually 1% to 3% of the emission aperture. R can be used as the maximum number of array elements with the maximum spacing. slsc Simply put, it can be represented as different array element intervals l The sum of.

[0053] 6. Mapping Imaging: For an N-image... x ×N y The SLSC image, where the value of each pixel in the SLSC image is obtained from R in step 4. slsc The coefficients are represented by values ​​ranging from 0 to 1, and are finally mapped to 0 to 255 for imaging.

[0054] The breast ultrasound CT reflection imaging method proposed in this invention can be implemented using a CPU or a GPU. Considering the imaging time, this embodiment uses a GPU for implementation. The steps include: data acquisition, data preprocessing, time-delay superposition operation at the receiving end, short-interval spatial coherence operation at the transmitting end, and mapping imaging. The specific process is shown in Figure 4.

[0055] (1) Data acquisition: First, the subject lies prone on the scanning table, and the unilateral breast to be scanned is centered on the ring probe (the probe radius is 110 mm and there are 2048 array elements). Then, the scanning parameters are set, the number of transmission events is set to 512 and the number of receiving channels is set to 2048, and the ring probe is used to acquire data of a slice of human breast tissue.

[0056] (2) Data preprocessing: For the i-th transmit and receive event, the signals received by the array elements on the left and right sides of the transmit array element are retained as reflected echo signals. The reflected echo signals are filtered by an FIR bandpass filter with an order of 72 and a passband frequency range of 1.5MHz to 4.5MHz.

[0057] (3) DAS operation at the receiving end: The reflection data corresponding to the i-th transmit-receive event is transmitted from the CPU to the GPU, and the delay superposition operation is performed at the receiving end. The result of the delay superposition is saved to the global memory of the GPU.

[0058] (4) SLSC operation at the transmitter: After completing the delay superposition operation at the receiver for all transmission events, access the delay superposition result in the GPU global memory, and perform the SLSC operation at the transmitter. The number of horizontal samples k in the SLSC imaging parameters of this invention is... x =3, axial sample number k y =3, maximum array element spacing L=4.

[0059] (5) The imaging results using the improved SLSC method of this invention and the conventional SLSC method are shown in Figures 5b and 5c, and the DAS imaging result is shown in Figure 5a. Compared with DAS, SLSC effectively reduces clutter in the breast lesion area, improves the contrast of the lesion, and also increases the visibility of the internal structure of the fat region. Comparing Figures 5b and 5c, it can be seen that the SLSC method proposed in this invention produces smoother images with higher contrast and more uniform resolution of imaging points.

[0060] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for breast ultrasound CT reflectance imaging, characterized in that, include: S1: Sequentially acquire the first echo signal corresponding to each element of the ring probe in N transmission and reception events of the patient's breast, and perform redundancy reduction processing, filtering processing and receiver delay superposition processing on the first echo signal to obtain the target echo signal corresponding to each element in N transmission and reception events. S2: Calculate the normalized spatial coherence value of each imaging point in the reconstructed image based on the target echo signal S(t) corresponding to each array element, and then calculate the short-interval spatial coherence coefficient of each imaging point; S3: Assign a grayscale value to each imaging point based on the short-interval spatial coherence coefficient of each imaging point in the reconstructed image.

2. The breast ultrasound CT reflectance imaging method as described in claim 1, characterized in that, For the transmitting array element n in the i-th transmit-receive event, retain the left and right sides of the transmitting array element n. The first echo signal received by the array element is used as the second echo signal corresponding to the i-th transmission event; the second echo signal is bandpass filtered to obtain the third echo signal; the third echo signal is subjected to receiver delay superposition operation to obtain the target echo signal S(t) corresponding to the i-th transmission and reception event, n∈[1, ele]. N ], ele N This refers to the number of elements in the ring probe array.

3. The breast ultrasound CT reflectance imaging method as described in claim 2, characterized in that, The target echo signal corresponding to the transmitting element n of the i-th transmit-receive event t(m,n,p)=(d np +d pm ) / c; where rf(t) represents the second echo signal received by array element m at time t after being emitted by array element n in the i-th emission event, and t(m,n,p) represents the time required for the sound wave emitted by array element n to be reflected after encountering the imaging point p(x,y) in the medium and the reflected echo to reach array element m; d np d pm Let n represent the distance from array element n to imaging point p(x,y) and the distance from imaging point p(x,y) to receiving array element m, respectively. Let c represent the speed of sound and m∈[1,M].

4. The breast ultrasound CT reflection imaging method as described in claim 2, characterized in that, M refers to the number of receiver array elements.

5. The breast ultrasound CT reflectance imaging method as described in claim 1, characterized in that, The normalized spatial coherence value for each imaging point in the reconstructed image is: The value at imaging point p(x,y) is determined by the values ​​of the i-th transmit / receive event and the (i+l-th)-th transmit / receive event within the neighborhood of point p, expressed as k. x ×k y The average of the coherence values ​​of each pixel is obtained; the number of horizontal samples k x = x2 - x1 + 1, axial sample number k y =y2-y1+1,s i (x,y) and s i+l (x,y) represent the target echo signals at imaging point p(x,y) for the i-th and (i+l)-th emission events, respectively.

6. The breast ultrasound CT reflectance imaging method as described in claim 4, characterized in that, The short-interval spatial coherence coefficient of each imaging point L represents the number of array elements in the maximum interval.

7. The breast ultrasound CT reflectance imaging method as described in claim 1, characterized in that, S3 includes: calculating the short-interval spatial coherence coefficient R of each imaging point in the reconstructed image. slsc The coefficient is represented as a value in the range of 0 to 1, and is mapped to a gray value of 0 to 255.

8. A breast ultrasound CT reflection imaging device, characterized in that, A method for performing breast ultrasound CT reflection imaging according to any one of claims 1-7, comprising: an acquisition module, configured to sequentially acquire the first echo signal corresponding to each element of the ring probe in N transmission and reception events of a patient's breast, and perform redundancy reduction processing, filtering processing, and receiver delay superposition processing on the first echo signal to obtain the target echo signal corresponding to each element in the N transmission and reception events; a calculation module, configured to calculate the normalized spatial coherence value of each imaging point in the reconstructed image based on the target echo signal S(t) corresponding to each element, and then calculate the short-interval spatial coherence coefficient of each imaging point; and an imaging module, configured to assign a grayscale value to each imaging point based on the short-interval spatial coherence coefficient of each imaging point in the reconstructed image.

9. An electronic device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 7.

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