Annular array multi-mode aperture-matched high-resolution ultrasonic CT image reconstruction method

Abstract

The application belongs to the technical field of medical ultrasonic imaging and industrial nondestructive testing, and discloses a kind of annular array multi-mode aperture matching high-resolution ultrasonic CT image reconstruction method, comprising the following steps: selecting calibration target object is placed in annular array center, the number of array elements included in the transmitting aperture and receiving aperture is determined, and circumferential scanning is carried out;The number of array elements included in the transmitting aperture and receiving aperture is changed respectively, and circumferential scanning is repeated;Data processing is carried out on the scanning results to obtain a reconstructed image, and the number of array elements included in the optimal transmitting aperture and corresponding receiving aperture is determined by calculating the half-width of the reconstructed image;The position of the calibration target object in the annular array is changed, and the optimal transmitting aperture and the number of array elements included in the corresponding receiving aperture under the condition of non-central calibration target position are determined by repeating the steps;According to the position of the target to be measured, the corresponding optimal transmitting and receiving aperture size is set, and the circumferential scanning and image reconstruction are repeated.The application can improve the resolution of image reconstruction.

Description

Technical Field

[0001] This invention belongs to the fields of medical ultrasound imaging and industrial non-destructive testing technology, specifically relating to a high-resolution ultrasound CT image reconstruction method based on ring array multi-mode aperture matching. Background Technology

[0002] With the rapid development of computer technology, information processing technology, and visual communication technology, humanity has entered a new information age. The amount of knowledge available to people is exploding, thus urgently requiring the continuous improvement and development of information processing technology to provide more convenient, faster, and more diversified services. Digital image processing and related technologies are a crucial component of information processing technology, finding increasingly widespread application in many fields. The requirement for digital images is high resolution. For example, medical images need to display minute lesions invisible to the human eye; satellite images require at least the ability to distinguish faces and even identification documents; some detection, identification, and control devices require sufficiently high-resolution images to ensure measurement and control accuracy. Therefore, improving image resolution is a key goal pursued in the field of image acquisition.

[0003] Ultrasound computed tomography (USCT) is a promising ultrasound diagnostic technique that can simultaneously record multiple acoustic information such as reflection, attenuation, and sound velocity to reconstruct images with high discrimination between benign and malignant tumors. Unlike common diagnostic equipment such as X-ray, CT, and magnetic resonance imaging (MRI), USCT technology does not involve ionizing radiation and is harmless to the human body. Furthermore, the expected cost of a USCT system is within the range of state-of-the-art X-ray diagnostic systems, eliminating the need for expensive imaging fees and biopsy procedures for patients, and allowing for repeat examinations.

[0004] Currently, the most frequently used ultrasound CT diagnostic equipment in the field of medical ultrasound includes linear array ultrasound probes and area array ultrasound probes. Linear array ultrasound transducers are simple in structure and low in cost, and the control of the ultrasound beam is easier in programming; however, their imaging is anisotropic, and image quality is affected by the position and depth of the object being measured. Lateral resolution is significantly lower than axial resolution, and echoes from deeper regions gradually attenuate during propagation. Furthermore, the application of linear array ultrasound transducers in medical imaging relies heavily on the technical skills of medical personnel, which can cause unnecessary interference. Area array ultrasound transducers are commonly used for ultrasound detection in three-dimensional space; however, area array ultrasound transducers have a larger number of array elements and more complex beam control algorithms, resulting in higher application costs.

[0005] In the field of non-destructive testing, pipeline transportation, as one of the most common means of material transport, is mainly used for long-distance transportation of oil and natural gas, agricultural irrigation, hydraulic engineering, and various industrial installations. With the rapid development of my country's economy in recent years, the volume of products such as oil and natural gas transported has increased significantly, leading to a corresponding increase in pipeline usage. This places more stringent demands on pipeline use and maintenance. Pipelines themselves may have certain defects, and most pipelines are often subjected to high pressure, high temperature, impact, and harsh environments during operation, resulting in pipeline corrosion and damage, and a relatively high rate of leakage accidents. Therefore, research on pipeline defect detection is of great significance for predicting pipeline corrosion and damage and preventing major accidents. However, inspecting numerous pipelines requires substantial manpower, material resources, financial resources, and time, with long inspection cycles and poor timeliness, failing to meet economic efficiency requirements.

[0006] For objects with arc or ring-shaped structures, linear and area arrays often fail to fit snugly enough during detection, neglecting information about movement gaps. Ring-array ultrasound probes, due to their unique arrangement, have transducer elements close to the object in any region within the array. However, current domestic research on ring-array ultrasound CT image reconstruction and fabrication is still in its early stages. Limited by imaging conditions and system resolution, existing image reconstruction algorithms struggle to obtain high-resolution images. Therefore, improvements to image reconstruction algorithms are needed to enhance the quality of reconstructed images. Summary of the Invention

[0007] To address the above problems, this invention proposes a high-resolution ultrasound CT image reconstruction method based on multi-mode aperture matching of a ring array. For different objects under test, there are different numbers of transmitting apertures with varying array elements, and the receiving aperture corresponds to these different numbers of receiving apertures when receiving echo data. The method proposed in this invention aims to modify the size matching of different transmitting and receiving apertures during the ring array image reconstruction process to adapt to the precise measurement of different biological tissues and non-destructive testing, thereby improving image resolution.

[0008] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a high-resolution ultrasound CT image reconstruction method based on ring array multi-mode aperture matching, comprising the following steps:

[0009] S1. Select the target object and place it at the center of the circular array. Determine the number of array elements included in the transmitting aperture and receiving aperture. Change the center of the transmitting aperture and receiving aperture and perform multiple transmitting-receiving processes until a complete circular scan is completed.

[0010] S2. Change the number of array elements included in the transmitting aperture and receiving aperture respectively, and repeat step S1 to obtain multiple complete circular scan results.

[0011] S3. Process and reconstruct the data of each circumferential scan result to obtain the reconstructed image of each circumferential scan result. Calculate the half-width at half-maximum of the reconstructed image and determine the optimal transmitting aperture and the number of array elements included in the corresponding receiving aperture based on the half-width at half-maximum of the reconstructed image.

[0012] S4. Change the position of the calibration target in the ring array, repeat steps S1 to S3, and determine the optimal number of array elements included in the transmitting aperture and receiving aperture under different calibration target position conditions.

[0013] S5. Based on the position of the target under test in the circular array, obtain and set the optimal number of array elements included in the transmitting aperture and receiving aperture, change the center of the transmitting aperture and receiving aperture, and perform multiple transmitting-receiving processes until a complete circular scan is completed; then reconstruct the image based on the results of the circular scan.

[0014] Preferably, in step S2, the number of array elements included in the transmitting aperture and the receiving aperture is set to one of 1, 3, 5, 9, 17, and 33, respectively.

[0015] Preferably, in step S3, the method for data processing and reconstruction of each circumferential scanning result is as follows:

[0016] Beam sampling and synthesis are performed on the received data from the centers of different transmitting and receiving apertures;

[0017] Then, Gaussian filtering, Hilbert transform, and logarithmic compression are performed.

[0018] By transforming the coordinates, the data in polar coordinates is converted to Cartesian coordinates, and the data is resampled to adapt to the display mode of the ultrasound equipment.

[0019] Preferably, in step S3, time gain compensation is used when performing beam sampling and synthesis.

[0020] Preferably, the ring array comprises 256 array elements.

[0021] Preferably, in step S1, the transmit-receive process is performed multiple times in a counterclockwise direction, with each array element as the center of the transmit aperture and the receive aperture, until a complete circular scan is completed.

[0022] Preferably, in step S1, the centers of the transmitting aperture and the receiving aperture coincide.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] 1. The high-resolution ultrasound CT image reconstruction method based on ring array multi-mode aperture matching proposed in this invention presents high-resolution images by changing the emission aperture and receiving aperture for different types of objects to be measured, which effectively improves the problems of low imaging resolution, poor signal-to-noise ratio and limited application range of traditional methods.

[0025] 2. This invention increases or decreases the size of the transmitting and receiving apertures, which reduces the system storage while ensuring imaging quality, and is more effective for measuring objects that require precise measurement.

[0026] 3. This invention improves upon acoustic power and image signal-to-noise ratio. The ring array possesses self-focusing properties; therefore, the proposed ultrasonic imaging method avoids beam defocusing by varying the sizes of the transmitting and receiving apertures, thus achieving advantages such as short image reconstruction time and high reconstruction resolution while reducing system complexity.

[0027] 4. This invention employs a ring transducer array. Due to its symmetrical structure, the ring array allows for the extraction of only a portion of the data during image processing to achieve relatively good imaging results. Combined with the image reconstruction method proposed in this invention, the image resolution can be further reconstructed.

[0028] 5. This invention employs ultrasound CT technology, primarily using cross-sectional imaging of the subject without interference from tissues above and below the same plane. Compared to commonly used X-ray detection, ultrasound CT technology has no harmful ionizing radiation, faster imaging speed, and better penetration in biological tissues. Therefore, ultrasound CT has high density resolution and can repeatedly examine biological tissues or organs.

[0029] 6. Hair-based imaging experiments demonstrated that this invention can reconstruct high-quality images without any depth dependence. The ring array ultrasound acquisition data came from a 256-channel Verasonics acquisition system (Verasonics Inc., Kirkland, WA, USA), achieving good imaging results. By controlling the ring array beamforming, multi-directional echo data of the object under test can be obtained. Special processing of this data can further improve image resolution and imaging quality. Attached Figure Description

[0030] Figure 1 A flowchart of a high-resolution ultrasound CT image reconstruction method using ring array multi-mode aperture matching provided in an embodiment of the present invention;

[0031] Figure 2 This is a schematic diagram of the transceiver control of the ultrasound CT image reconstruction method with multi-mode aperture matching of a ring array in an embodiment of the present invention;

[0032] Figure 3The curves showing the full width at half maximum (FWHM) of the reconstructed images for different receiving apertures when a hair strand is located at the center of the circular array.

[0033] Figure 4 The curves showing the full width at half maximum (FWHM) of the reconstructed images for different receiving apertures when a hair strand is located at the edge of the circular array.

[0034] Figure 5 The full width at half maximum (FWHM) curves of the reconstructed images corresponding to each transmitting aperture when the hair strand is located at the center of the ring array, and the imaging results of the optimal aperture (optimal transmitting aperture is 17, optimal receiving aperture is 17).

[0035] Figure 6 The full width at half maximum (FWHM) curves and optimal aperture imaging results are shown for the reconstructed images corresponding to each transmitting aperture when the hair strand is located at the edge of the ring array (optimal transmitting aperture is 3, optimal receiving aperture is 5). Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] like Figure 1 As shown, this embodiment of the invention provides a high-resolution ultrasound CT image reconstruction method based on ring array multi-mode aperture matching, comprising the following steps:

[0038] S1. Select the target object and place it at the center of the circular array. Determine the transmitting aperture and receiving aperture. Change the center of the transmitting aperture and receiving aperture and perform multiple transmitting-receiving processes until a complete circular scan is completed.

[0039] In step S1, multiple transmit-receive processes are performed counterclockwise, with each array element serving as the center of the transmit and receive apertures, until a complete circular scan is completed. Specifically, in this embodiment, the ring array includes 256 array elements, so each complete circular scan includes 256 transmit-receive processes.

[0040] Specifically, such as Figure 2 As shown, in step S1, the centers of the transmitting aperture and the receiving aperture coincide.

[0041] S2. Change the number of array elements included in the transmitting aperture and receiving aperture respectively, and repeat step S1 to obtain multiple complete circular scan results.

[0042] In step S2, the number of array elements included in the transmitting aperture and the receiving aperture are set to 1, 3, 5, 9, 17, or 33, respectively. Furthermore, the number of array elements included in the transmitting aperture and the receiving aperture can be equal or unequal. Additionally, the number of array elements in the transmitting aperture and the receiving aperture can be arbitrarily chosen, but the number of array elements in the transmitting and receiving apertures cannot exceed 1 / 8 of the total number of array elements.

[0043] S3. Process and reconstruct the data of each circumferential scan result to obtain the reconstructed image of each circumferential scan result. Calculate the half-width at half-maximum (WHM) of the reconstructed image and determine the optimal transmitting aperture and the number of array elements included in the corresponding receiving aperture based on the WHM of the reconstructed image.

[0044] Specifically, in step S3, the method for data processing and reconstruction of each circumferential scanning result is as follows:

[0045] (1) Beam sampling and synthesis of the received data at the center of different transmitting and receiving apertures; in order to avoid the repetition of the received echo information from the object under test due to the specificity of the ring array symmetry structure, the obtained data is extracted to reduce the amount of data storage and processing time, thereby speeding up the image reconstruction.

[0046] (2) Then, Gaussian filtering, Hilbert transform, and logarithmic compression are performed. Gaussian filtering can reduce the influence of noise outside the frequency range; Hilbert transform is used to extract the envelope, so that high-frequency changes in the received signal are eliminated during the demodulation process of envelope detection; logarithmic compression can reduce the grayscale values ​​to a dynamic range that can be recognized by the human eye and display.

[0047] (3) By transforming the coordinates, the data in polar coordinates is transformed into the Cartesian coordinate system, and the data is resampled to adapt to the mode display of the ultrasound equipment.

[0048] Specifically, in step S3, time gain compensation is used during beam sampling and synthesis. Time gain compensation refers to gradually increasing the gain of the echo signal after the pulse emission begins as time progresses. This correction makes the same tissue or structure at different depths appear relatively consistent on the sonogram, overcoming the signal attenuation caused by ultrasonic energy decay.

[0049] S4. Change the position of the calibration target in the ring array, repeat steps S1 to S3, and determine the optimal transmitting aperture and corresponding receiving aperture size under different calibration target position conditions.

[0050] S5. Based on the position of the target under test in the circular array, obtain and set the number of array elements included in the optimal transmitting aperture and receiving aperture, that is, set the actual transmitting aperture and receiving aperture to the corresponding optimal size; change the center of the transmitting aperture and receiving aperture, and perform multiple transmitting-receiving processes until a complete circular scan is completed; then reconstruct the image based on the results of the circular scan.

[0051] In step S5, the method for reconstructing the image is the same as in step S3.

[0052] Experimental example:

[0053] This invention provides an embodiment of a CT experimental platform, which mainly includes the following operational steps:

[0054] (1) Install the water-sealed 256-element ring array on an acrylic clamp and fix it with nuts of the same material;

[0055] (2) The upper and lower surfaces of the electric rotary table along the vertical direction are connected to the acrylic clamp and the detection bracket of the fixed ring array respectively by nuts;

[0056] (3) Place an acrylic water tank with a diameter of 60cm under the testing bracket. The water level should completely cover the upper surface of the ring array to ensure that the entire ring array is submerged in water.

[0057] (4) The constant temperature heater is fixed on the inner wall of the water tank and the temperature is controlled at about 23℃ to ensure a constant temperature environment inside the water tank.

[0058] (5) The 256-element ring array is connected to the Verasonics multi-channel high-speed acquisition system through two ultrasonic transducer connectors, with one-to-one correspondence between the array elements and the system channels.

[0059] (6) The host is responsible for controlling the ring ultrasonic transducer array and the acquisition system to perform fully automatic ultrasonic signal acquisition and storage according to the predefined scanning mode.

[0060] A 0.03 mm diameter strand of adult female hair was used as the test subject, and ultrasound CT imaging tests were conducted using a constructed imaging system experimental platform. The specific test procedure is as follows: First, the hair strand was placed at the center of a 256-element circular array. The emission aperture was changed to 1, 3, 5, 9, 17, and 33, with corresponding receiving apertures of 1, 3, 5, 9, 17, and 33. The entire circular array elements underwent 256 transmit-receive cycles sequentially until a complete circular scan was completed. The acquired data was transmitted to the workstation's receiving data buffer via a PCI Express cable. Next, the hair strand was placed at the edge of the circular array, and the above operation was performed. Finally, the method proposed in this invention was used to process and reconstruct the acquired data.

[0061] Results Analysis: Half-width at half-maximum (HWHM) is a method for measuring image resolution. It refers to the width of a peak or brightest point in an image, the distance from its maximum value to half its value. A smaller HWHM indicates clearer details and higher resolution in the image. To further verify the imaging effects under different transmit / receive aperture matching modes, this invention performs HWHM quantization analysis on imaging under multiple transmit apertures corresponding to different receive apertures, such as... Figure 3 and Figure 4 As shown. The optimal transmit / receive aperture and the optimal aperture imaging results for a hair strand located at the center and edge of the ring array are as follows. Figure 5 and Figure 6 As shown. Among them, (a) is the full width at half maximum (FWHM) curve of each transmitting aperture when the hair strand is located at the center (edge) position and the optimal receiving aperture is 17 (5), and (b) is the imaging result of the optimal aperture.

[0062] In summary, the present invention provides a high-resolution ultrasound CT image reconstruction method based on ring array multi-mode aperture matching. It changes the number of transmitting and receiving apertures for different types of objects to present high-resolution images, effectively improving the problems of low imaging resolution, poor signal-to-noise ratio, and limited application range of existing methods.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for high-resolution ultrasound CT image reconstruction using multi-mode aperture matching with a ring array, characterized in that, Includes the following steps: S1. Select the target object and place it at the center of the circular array. Determine the number of array elements included in the transmitting aperture and receiving aperture. Change the center of the transmitting aperture and receiving aperture and perform multiple transmitting-receiving processes until a complete circular scan is completed. S2. Change the number of array elements included in the transmitting aperture and receiving aperture respectively, and repeat step S1 to obtain multiple complete circular scan results. S3. Process and reconstruct the data of each circumferential scan result to obtain the reconstructed image of each circumferential scan result. Calculate the half-width at half-maximum of the reconstructed image and determine the optimal transmitting aperture and the number of array elements included in the corresponding receiving aperture based on the half-width at half-maximum of the reconstructed image. S4. Change the position of the calibration target in the ring array, repeat steps S1 to S3, and determine the optimal number of array elements included in the transmitting aperture and receiving aperture under different calibration target position conditions. S5. Based on the position of the target under test in the circular array, obtain and set the optimal number of array elements included in the transmitting aperture and receiving aperture, change the center of the transmitting aperture and receiving aperture, and perform multiple transmitting-receiving processes until a complete circular scan is completed; then reconstruct the image based on the results of the circular scan.

2. The high-resolution ultrasound CT image reconstruction method based on multi-mode aperture matching of a ring array according to claim 1, characterized in that, In step S2, the number of array elements included in the transmitting aperture and the receiving aperture are set to one of 1, 3, 5, 9, 17, and 33, respectively.

3. The high-resolution ultrasound CT image reconstruction method based on multi-mode aperture matching of a ring array according to claim 1, characterized in that, In step S3, the method for data processing and reconstruction of each circumferential scanning result is as follows: Beam sampling and synthesis are performed on the received data from the centers of different transmitting and receiving apertures; Then, Gaussian filtering, Hilbert transform, and logarithmic compression are performed. By transforming the coordinates, the data in polar coordinates is converted to Cartesian coordinates, and the data is resampled to adapt to the display mode of the ultrasound equipment.

4. The high-resolution ultrasound CT image reconstruction method based on multi-mode aperture matching of a ring array according to claim 3, characterized in that, In step S3, time gain compensation is used when performing beam sampling and synthesis.

5. The high-resolution ultrasound CT image reconstruction method based on multi-mode aperture matching of a ring array according to claim 1, characterized in that, The ring array comprises 256 elements.

6. The high-resolution ultrasound CT image reconstruction method based on multi-mode aperture matching of a ring array according to claim 4, characterized in that, In step S1, the transmission-reception process is performed multiple times in a counterclockwise direction, with each array element as the center of the transmitting aperture and the receiving aperture, until a complete circular scan is completed.

7. The high-resolution ultrasound CT image reconstruction method based on multi-mode aperture matching of a ring array according to claim 4, characterized in that, In step S1, the centers of the transmitting aperture and the receiving aperture coincide.

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