WO2025087445A1 - Large-aperture ultrafast ultrasound imaging system and method - Google Patents

Abstract

A large-aperture ultrafast ultrasound imaging system and method. The large-aperture ultrafast ultrasound imaging system comprises an ultrasound transmitting module (1) and a large-aperture ultrasound transducer array (2). The ultrasound transmitting module (1) is used for generating a transmitting pulse sequence, wherein the transmitting pulse sequence excites, by means of pulses of different waveforms, a transmitting unit on the large-aperture ultrasound transducer array (2) at the same time or according to a transmission delay, so as to form an ultrasound pulse wave, and a plurality of ultrasound pulse waves generated by means of the excitation of a plurality of transmitting pulse sequences form a group of ultrafast ultrasound sequences. The large-aperture ultrasound transducer array (2) comprises a plurality of ultrasound transducer units, wherein each ultrasound transducer unit is used for receiving the transmitting pulse sequence generated by means of the ultrasound transmitting module, converting the transmitting pulse sequence into the ultrasound pulse wave and transmitting same to an object under test. Therefore, the imaging rate is greatly improved, the detection angle is complete, imaging details are rich, boundary information is more complete, and the sensitivity to blood flow Doppler signals in different directions is also improved.

Description

Large aperture ultrafast ultrasonic imaging system and method

This application claims the priority of the Chinese patent application filed with the China Patent Office on October 25, 2023, with application number 202311388008.5 and invention name “A large-aperture ultrafast ultrasonic imaging system and method”, the entire contents of which are incorporated by reference in this application.

Technical Field

The present application belongs to the field of biomedical imaging technology, and in particular, relates to a large-aperture ultrafast ultrasound imaging system and method.

Background Art

Ultrasound imaging is the most widely used examination method in medical imaging technology. The basic principle is that when ultrasound propagates in the human body, due to the difference in acoustic impedance caused by the difference in tissue structure distribution in the human body, the ultrasound is reflected and scattered during the propagation process and is received by the ultrasound array and reconstructed through hardware or software beamforming.

Ultrasonic tomography usually uses large-aperture ultrasonic transducer arrays such as circular and polygonal ultrasonic arrays to achieve ultrasonic transmission and reception. Reflective ultrasonic tomography excites individual units on the large-aperture ultrasonic transducer array one by one and receives echo signals for imaging. It has disadvantages such as large data volume and slow imaging speed, which makes it difficult to promote and use in clinical practice.

As a new generation of ultrasound technology, ultrafast ultrasound imaging technology has the characteristics of high frame rate and high sensitivity, which breaks through the performance limitations of traditional ultrasound imaging. The main implementation method of ultrafast ultrasound is plane wave imaging technology, which can obtain echo signals in the entire imaging area with one emission. Its pulse repetition frequency is equal to the frame rate, but due to the lack of emission focusing, the imaging signal-to-noise ratio is low and the imaging quality is poor.

Existing ultrafast ultrasound imaging technologies mostly use a linear array. Due to the emission directionality limitation of a linear array, the tilt angle of the plane wave should not be too large, which further limits its detection sensitivity to the organ tissue boundary perpendicular to the array direction and the Doppler signal parallel to the array direction. At the same time, due to the limited receiving aperture of the linear array, only part of the ultrasound reflection and scattered echo signals can be received, which limits the imaging resolution and contrast.

Summary of the invention

The purpose of this application is to provide a large-aperture ultrafast ultrasonic imaging system and method to solve the above-mentioned technical problems.

In order to solve the above technical problems, the large aperture ultrafast ultrasonic imaging system and method of the present application are specifically The technical solution is as follows:

A large-aperture ultrafast ultrasonic imaging system comprises an ultrasonic transmitting module and a large-aperture ultrasonic transducer array.

The ultrasonic transmitting module is used to generate a transmitting pulse sequence, wherein the transmitting pulse sequence excites the transmitting units on the large-aperture ultrasonic transducer array simultaneously or according to the transmitting delay through pulses of different waveforms to form an ultrasonic pulse wave, and the multiple ultrasonic pulse waves generated by the excitation of multiple transmitting pulse sequences constitute a group of ultrafast ultrasonic sequences;

The large-aperture ultrasonic transducer array includes a plurality of ultrasonic transducer units, which are used to receive a transmission pulse sequence generated by an ultrasonic transmission module, and convert the transmission pulse sequence into an ultrasonic pulse wave to transmit to the object to be measured. The ultrasonic pulse wave is reflected and scattered during propagation in the object to be measured, and finally propagates to the large-aperture ultrasonic transducer array, is received by the array, and is converted into an ultrasonic echo signal.

In one embodiment, the maximum angular difference of the ultrasound propagation direction at any point in the imaging area of different ultrasound transducer units on the large-aperture ultrasound transducer array is greater than 60°.

In one embodiment, the large-aperture ultrasonic transducer array includes the following forms: one or more arc-shaped ultrasonic transducer arrays form an arc-shaped large-aperture ultrasonic transducer array; multiple linear ultrasonic transducer arrays form a linear large-aperture ultrasonic transducer array; multiple ultrasonic transducer units are arranged in space to form a spherical large-aperture ultrasonic transducer array or a polyhedral large-aperture ultrasonic transducer array.

In one embodiment, the ultrafast ultrasound sequence includes one or more ultrasound pulse waves, each of which completely covers and excites the imaging area during propagation. Under the control of the emission pulse sequence, the ultrasound pulse wave is any combination of a single excitation angle or a plurality of divergent waves, plane waves, and focused waves with different excitation angles. The excitation angle of the ultrasound pulse wave is changed by changing the emission delay or exciting the emission units at different positions. The variable range of the excitation angle of the focused wave, plane wave, or divergent wave is between -90° and 90°.

In one embodiment, it also includes a data acquisition module, which is used to receive ultrasonic echo signals, realize analog amplification, analog-to-digital conversion, storage, transmission and output digital signals to the image reconstruction module.

In one embodiment, a system control module is further included, wherein the system control module is used to control The number and distribution of the transmitting units, the properties of the transmitting pulse sequence, the transmitting delay, and the analog amplification gain and sampling rate parameters of the data acquisition module.

In one embodiment, the system further includes an image reconstruction module, which performs image reconstruction by using a delay-sum based beamforming algorithm.

In one embodiment, the image reconstruction module reconstructs the echo signal obtained by exciting a single ultrasonic pulse wave at a certain angle in the ultrafast ultrasonic sequence to form a sub-image, and the gray value of any point on the sub-image is:
I(x,z)=∑ _i RF(i,τ(i,α,x,z),α);

Where x, z are the coordinates of any point on the sub-image, α is the ultrasonic pulse wave excitation angle, RF is the ultrasonic echo signal, τ is the ultrasonic propagation time, and the sub-images obtained by different ultrasonic pulse wave excitations are coherently superimposed to obtain the final reconstructed image; i is the index of the ultrasonic transducer unit;

The ultrafast ultrasound sequence is a coded transmitted ultrasound pulse wave, wherein the coded transmission simultaneously transmits a plurality of ultrasound pulse waves with coded transmission signal amplitudes and excitation angles in a single transmission event, and decodes the signal before image reconstruction.

In one embodiment, the large-aperture ultrasonic transducer array is composed of one or more curved ultrasonic transducer arrays, and the ultrafast ultrasonic sequence in a single transmission event includes multiple plane waves with different excitation angles and different signal amplitudes. The steps of spatial domain encoding and decoding are as follows:

S1: construct Hadamard matrix;

S2: In each emission event, according to the elements of each row or column of the Hadamard matrix, the emission units in multiple different regions are excited simultaneously with the emission sequence corresponding to the amplitude weight;

S3: summing the ultrasonic echo signals of different emission events according to the amplitude weight of each emission event to synthesize the echo signal of the ultrasonic pulse wave with a single excitation angle.

The present application also discloses an ultrafast ultrasonic imaging method of a large-aperture ultrafast ultrasonic imaging system, comprising the following steps:

Step 1: The ultrasonic transmitting module generates a transmitting pulse sequence to excite the large-aperture ultrasonic transducer array. The transmitting pulse sequence excites the transmitting units on the large-aperture ultrasonic transducer array simultaneously or according to the transmitting delay to generate ultrasonic pulse waves. Multiple transmitting pulse sequences excite the generated multiple ultrasonic pulse waves to form a group of ultrafast ultrasonic sequences.

Step 2: The large-aperture ultrasonic transducer array receives the transmission pulse sequence generated by the ultrasonic transmission module, and transmits ultrasonic pulse waves to the object to be measured at a large-aperture ultrasonic excitation angle to cover the target imaging range;

Step 3: The large-aperture ultrasonic transducer array detects the ultrasonic echo signal from the object to be measured at a large-aperture ultrasonic detection angle and transmits it to the data acquisition module for analog-to-digital conversion, storage, transmission and output of the digital signal to the image reconstruction module for further ultrasonic image reconstruction.

The large-aperture ultrafast ultrasonic imaging system and method of the present application have the following advantages:

The present application adopts multiple ultrasonic transducer units to form a large-aperture ultrasonic transducer array, and simultaneously excites or changes the excitation time of the ultrasonic array units through pulses of different waveforms, obtains multiple frames of plane wave images of the same imaging area from multiple deflected emission angles, and coherently superimposes the multiple frames of images to obtain a composite image. Due to the synthetic focusing effect when superimposing plane wave images corresponding to different deflection angles, this method can effectively improve the signal-to-noise ratio of the imaging results, and different emission angles can improve the edge loss problem of the image.

(1) Fast imaging speed. Compared with the imaging method of reflection ultrasonic tomography that excites ultrasonic transducer units one by one, large-aperture ultrafast ultrasonic imaging adopts the method of simultaneously exciting emission-type ultrasonic transducer units. The ultrasonic pulse wave generated by one emission can radiate the entire effective imaging area and collect ultrasonic signals in the entire effective imaging area, which greatly improves the imaging speed.

(2) The detection angle is complete and the imaging details are rich. The use of a large-aperture ultrasonic transducer array can cover a larger ultrasonic excitation and ultrasonic reception angle. The existing ultrafast ultrasound technology mostly uses a linear ultrasonic array with limited excitation and detection angles. There are disadvantages such as incomplete imaging result boundaries and low sensitivity to blood flow Doppler signals in the direction parallel to the array. The use of a large-aperture ultrasonic transducer array can make the boundary information of the imaging results more complete and improve the sensitivity to blood flow Doppler signals in different directions.

Instruction Manual

FIG1 is a diagram of a large-aperture ultrafast ultrasonic imaging system of the present application.

FIG2 is a diagram of an ultrafast ultrasonic imaging system based on an arc-shaped large-aperture ultrasonic transducer array and a schematic diagram of a focused wave ultrafast ultrasonic sequence of the present application.

3 is a diagram of an ultrafast ultrasonic imaging system based on a linear large-aperture ultrasonic transducer array to simultaneously excite transmitting units at different positions and a schematic diagram of a plane wave ultrafast ultrasonic sequence according to the present application.

4 is a diagram of an ultrafast ultrasound imaging system and a schematic diagram of a plane wave ultrafast ultrasound sequence based on simultaneous or delayed excitation of transmitting units at the same position by a linear large-aperture ultrasound transducer array according to the present invention.

5 is a diagram of an ultrafast ultrasonic imaging system based on an arc-shaped large-aperture ultrasonic transducer array to excite transmitting units at different positions and a schematic diagram of a diverging wave ultrafast ultrasonic sequence according to the present application.

6 is a diagram of an ultrafast ultrasonic imaging system for adjusting the position of a virtual source based on an arc-shaped large-aperture ultrasonic transducer array and a schematic diagram of a diverging wave ultrafast ultrasonic sequence according to the present application.

FIG. 7 is a diagram of an ultrafast ultrasonic imaging system based on a spherical large-aperture ultrasonic transducer array and a schematic diagram of a diverging wave ultrafast ultrasonic imaging sequence according to the present application.

FIG8 is a schematic diagram of a diverging wave ultrafast ultrasonic imaging sequence of an ultrafast ultrasonic imaging system atlas based on a polyhedral large-aperture ultrasonic transducer array of the present application.

FIG. 9 shows an ultrafast ultrasound sequence in a single emission event, including multiple plane waves with different excitation angles and different signal amplitudes.

Figure numerals: 1. Ultrasonic transmitting module; 2. Large-aperture ultrasonic transducer array; 3. System control module; 4. Data acquisition module; 5. Image reconstruction module; 6. Object to be measured.

DETAILED DESCRIPTION

In order to better understand the purpose, structure and function of the present application, the following is a further detailed description of a large-aperture ultrafast ultrasonic imaging system and method of the present application in conjunction with the accompanying drawings.

As shown in Figure 1, the large-aperture ultrafast ultrasonic imaging system of the present application mainly includes an ultrasonic transmitting module 1, a large-aperture ultrasonic transducer array 2, a data acquisition module 4, a system control module 3 and an image reconstruction module 5, and secondly also includes a transmitting and receiving conversion switch, a preamplifier circuit and a spatial scanning module.

The ultrasonic transmitting module 1 in this embodiment is used to generate a transmitting pulse sequence to excite the large-aperture ultrasonic transducer array 2. The transmitting pulse sequence can excite the transmitting units on the large-aperture ultrasonic transducer array 2 simultaneously or according to the transmission delay through pulses of different waveforms to form an ultrasonic pulse wave. The multiple ultrasonic pulse waves generated by the excitation of multiple transmitting pulse sequences constitute a group of ultrafast ultrasonic sequences.

The large-aperture ultrasonic transducer array 2 in this embodiment includes multiple ultrasonic transducer units. The maximum angular difference in the ultrasonic propagation direction of any point in the imaging area of different ultrasonic transducer units on the large-aperture ultrasonic transducer array 2 is greater than 60°. It is used to receive the transmission pulse sequence generated by the ultrasonic transmitting module 1, and convert the transmission pulse sequence into an ultrasonic pulse wave to be transmitted to the object to be measured 6. Due to the difference in acoustic impedance distribution in the object to be measured 6, the ultrasonic pulse wave is reflected and scattered during the propagation process in the object to be measured 6, and finally propagates to the large-aperture ultrasonic transducer array 2, is received by it and converted into an ultrasonic echo signal.

As shown in FIG. 2 , the large-aperture ultrasonic transducer array 2 may include one or more arc-shaped ultrasonic transducer arrays, the arc angle of the arc-shaped ultrasonic transducer array ranges from 5° to 359°, and the arc-shaped ultrasonic transducer arrays are combined to form an arc-shaped large-aperture ultrasonic transducer array.

As shown in FIG. 3-4, the large-aperture ultrasonic transducer array 2 may also include multiple linear ultrasonic transducer arrays, wherein the multiple linear ultrasonic transducer arrays are arranged to form a polygon or a part of a polygon, and the multiple linear ultrasonic transducer arrays are combined to form a linear large-aperture ultrasonic transducer array.

As shown in FIG. 7 , the large-aperture ultrasonic transducer array 2 may further include a plurality of ultrasonic transducer units, and the ultrasonic transducer units are spatially arranged to form a part of a sphere, thereby forming a spherical large-aperture ultrasonic transducer array.

As shown in FIG. 8 , the large-aperture ultrasonic transducer array 2 may further include a plurality of ultrasonic transducer units, and the ultrasonic transducer units are spatially arranged to form a part of a polyhedron, forming a polyhedron large-aperture ultrasonic transducer array.

The data acquisition module 4 in this embodiment receives the ultrasonic echo signal, implements analog amplification, analog-to-digital conversion, storage, transmission, and outputs the digital signal to the image reconstruction module 5 .

The system control module 3 in this embodiment controls the number and distribution of the transmitting units, the properties of the transmitting pulse sequence, the transmitting delay, and the analog amplification gain and sampling rate of the data acquisition module 4 and other parameters.

The image reconstruction module 5 in this embodiment receives the digital signal output by the data acquisition module 4 and reconstructs the acoustic impedance difference distribution in the body to be measured according to the amplitude, time, phase and frequency information contained therein.

The transmit-receive conversion switch in this embodiment is used to realize the switching of the ultrasonic transducer unit between the transmit mode and the receive mode.

The preamplifier circuit in this embodiment is used to achieve pre-amplification of the ultrasonic echo signal.

The spatial scanning module in this embodiment is used to implement large-aperture ultrasound of the object to be measured.

The imaging frame rate of the system is configured to be 100 fps or higher to achieve ultrafast ultrasound imaging.

The ultrafast ultrasound sequence includes one or more ultrasound pulse waves, each of which completely covers and excites the imaging area during propagation. Under the control of the transmission pulse sequence, the ultrasound pulse wave can be any combination of a single excitation angle or multiple divergent waves, plane waves, and focused waves with different excitation angles. The excitation angle of the focused wave, plane wave, or divergent wave can be variable in the range of -90° to 90°.

As shown in FIG2 , the large-aperture ultrasonic transducer array 2 is composed of a plurality of arc-shaped ultrasonic transducer arrays, and the ultrafast ultrasonic sequence includes a plurality of focused waves with different excitation angles, and the transmitting units on the selected large-aperture ultrasonic transducer array are excited by the emission pulse sequence simultaneously or according to the emission delay, so that the ultrasonic pulse waves converge in front of the ultrasonic array, thereby making the ultrasonic pulse waves focused waves. The emission pulse sequence changes the excitation angle of the focused wave by exciting the transmitting units at different positions, and sequentially emits wavefront 1, wavefront 2, and wavefront 3.

As shown in FIG3 , the large-aperture ultrasonic transducer array 2 is composed of a plurality of linear ultrasonic transducer arrays, the ultrafast ultrasonic sequence includes a plurality of plane waves with different excitation angles, and the transmitting pulse sequence changes the excitation angle of the plane wave by simultaneously exciting the transmitting units at different positions, and sequentially transmits wavefront 1, wavefront 2, and wavefront 3.

As shown in FIG4 , the large-aperture ultrasonic transducer array 2 is composed of a plurality of linear ultrasonic transducer arrays, and the ultrafast ultrasonic sequence includes a plurality of plane waves with different excitation angles. The transmitting pulse sequence excites the transmitting units at the same position simultaneously or with a delay, so that the excitation phases of the transmitting units change linearly with respect to each other, and wavefront 1, wavefront 2, and wavefront 3 are emitted in sequence, thereby adjusting the excitation angle and time of the plane wave.

As shown in FIG5 , the large-aperture ultrasonic transducer array 2 is composed of a plurality of arc-shaped ultrasonic transducer arrays, and the ultrafast ultrasonic sequence includes a plurality of divergent waves with different excitation angles. By defining virtual sources, such as virtual source 1, virtual source 2, and virtual source 3 in FIG5 , and making the emission pulse sequence excite the emission unit with a phase delay corresponding to the virtual source, the ultrasonic pulse wave can be made into a divergent wave, and by exciting the emission units at different positions, divergent waves with different angles can be emitted in sequence: wavefront 1, wavefront 2, and wavefront 3.

As shown in FIG6 , the large aperture ultrasonic transducer array 2 is composed of a plurality of arc-shaped ultrasonic transducer arrays, and the ultrafast ultrasonic sequence includes a plurality of divergent waves with different excitation angles. By laterally moving the virtual source, such as virtual source 1 and virtual source 3 in FIG6 , and exciting the emission unit with a phase delay corresponding to the virtual source, the divergent wave direction can be deflected, thereby achieving divergent wave excitation at different angles. The divergence degree of the divergent wave can be adjusted by moving the virtual source closer to or farther away from the array, and the emission unit can be excited with a phase delay corresponding to the virtual source, so that divergent wave excitation with different divergence degrees can be achieved.

As shown in FIG7 , the large-aperture ultrasonic transducer array 2 is composed of a plurality of ultrasonic transducer units to form a spherical large-aperture ultrasonic transducer array. The ultrafast ultrasonic sequence includes a plurality of divergent waves with different excitation angles, such as wavefront 1, wavefront 2, and wavefront 3 in FIG7 . tx1 and tx2 in the figure represent the distribution range of the transmitting units.

As shown in FIG8 , the large-aperture ultrasonic transducer array 2 is composed of a plurality of ultrasonic transducer units to form a polyhedral large-aperture ultrasonic transducer array. The ultrafast ultrasonic sequence includes a plurality of divergent waves with different excitation angles, such as wavefront 1 and wavefront 2 in FIG8 . tx1 and tx2 in the figure represent the distribution range of the transmitting units.

The image reconstruction module 5 in this embodiment can perform image reconstruction by a delayed-sum based beamforming algorithm. The echo signal obtained by exciting a single ultrasonic pulse wave at a certain angle in the ultrafast ultrasonic sequence can be reconstructed to form a sub-image, and the gray value of any point on the sub-image is:
I(x,z)=∑ _i RF(i,τ(i,α,x,z),α).

Where x, z are the coordinates of any point on the sub-image, α is the ultrasonic pulse wave excitation angle, RF is the ultrasonic echo signal, τ is the ultrasonic propagation time, and the sub-images obtained by different ultrasonic pulse wave excitations are coherently superimposed to obtain the final reconstructed image. i is the index of the ultrasonic transducer unit, that is, the i-th ultrasonic transducer unit. The value range of i is from 1 to N, where N is the number of ultrasonic transducer units.

The ultrafast ultrasound sequence in this embodiment may also be a coded transmitted ultrasound pulse wave, wherein the coded transmission simultaneously transmits multiple ultrasound pulse waves with encoded transmission signal amplitudes and excitation angles in a single transmission event, and decodes the signal before image reconstruction to improve the image signal-to-noise ratio.

As shown in FIG9 , the large-aperture ultrasonic transducer array 2 is composed of one or more arc-shaped ultrasonic transducer arrays. The ultrafast ultrasonic sequence in a single emission event includes multiple plane waves with different excitation angles and different signal amplitudes. The steps of spatial domain encoding and decoding are as follows:

S1: Construct the Hadamard matrix.

S2: In each emission event, according to the elements of each row or column of the Hadamard matrix, emission units in multiple different regions are simultaneously excited with an emission sequence corresponding to the amplitude weight.

S3: summing the ultrasonic echo signals of different emission events according to the amplitude weight of each emission event to synthesize the echo signal of the ultrasonic pulse wave with a single excitation angle.

A large-aperture ultrafast ultrasonic imaging method of the present application comprises the following steps:

Step 1: The ultrasonic transmitting module 1 generates a transmitting pulse sequence to excite the large-aperture ultrasonic transducer array 2. The transmitting pulse sequence excites the transmitting units on the large-aperture ultrasonic transducer array simultaneously or according to the transmitting delay to generate an ultrasonic pulse wave. Multiple ultrasonic pulse waves generated by the excitation of multiple transmitting pulse sequences constitute a group of ultrafast ultrasonic sequences.

Step 2: The large-aperture ultrasonic transducer array 2 receives the transmission pulse sequence generated by the ultrasonic transmission module, and transmits ultrasonic pulse waves to the object to be measured 6 at a larger ultrasonic excitation angle to cover the target imaging range.

Step 3: The large-aperture ultrasonic transducer array 2 detects the ultrasonic echo signal from the object to be tested at a larger ultrasonic detection angle and transmits it to the data acquisition module 4, performs analog-to-digital conversion, stores, transmits and outputs the digital signal to the image reconstruction module 5 for further ultrasonic image reconstruction.

It is to be understood that the present application is described by some embodiments, and it is known to those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present application. In addition, under the guidance of the present application, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present application. Therefore, the present application is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of the present application are within the scope protected by the present application.

Claims (10)

A large-aperture ultrafast ultrasonic imaging system comprises an ultrasonic transmitting module (1) and a large-aperture ultrasonic transducer array (2), characterized in that the ultrasonic transmitting module (1) is used to generate a transmitting pulse sequence, wherein the transmitting pulse sequence excites the transmitting units on the large-aperture ultrasonic transducer array (2) with pulses of different waveforms simultaneously or according to a transmitting delay to form an ultrasonic pulse wave, and the multiple ultrasonic pulse waves generated by the excitation of multiple transmitting pulse sequences constitute a group of ultrafast ultrasonic sequences; The large-aperture ultrasonic transducer array (2) comprises a plurality of ultrasonic transducer units, wherein the ultrasonic transducer units are used to receive a transmission pulse sequence generated by an ultrasonic transmission module, and convert the transmission pulse sequence into an ultrasonic pulse wave for transmission to the object to be measured. The ultrasonic pulse wave is reflected and scattered during propagation in the object to be measured, and finally propagates to the large-aperture ultrasonic transducer array (2), is received by the array and converted into an ultrasonic echo signal. A large-aperture ultrafast ultrasonic imaging system according to claim 1, characterized in that the maximum angular difference in the ultrasonic propagation direction at any point in the imaging area of different ultrasonic transducer units on the large-aperture ultrasonic transducer array (2) is greater than 60°. A large-aperture ultrafast ultrasonic imaging system according to claim 1, characterized in that the large-aperture ultrasonic transducer array (2) includes the following forms: one or more arc-shaped ultrasonic transducer arrays form an arc-shaped large-aperture ultrasonic transducer array; multiple linear ultrasonic transducer arrays form a linear large-aperture ultrasonic transducer array; multiple ultrasonic transducer units are arranged in space to form a spherical large-aperture ultrasonic transducer array or a polyhedral large-aperture ultrasonic transducer array. A large-aperture ultrafast ultrasonic imaging system according to claim 1, characterized in that the ultrafast ultrasonic sequence includes one or more ultrasonic pulse waves, each ultrasonic pulse wave completely covers and excites the imaging area during propagation, and under the control of the emission pulse sequence, the ultrasonic pulse wave is any combination of a single excitation angle or a plurality of divergent waves, plane waves, and focused waves with different excitation angles, and the excitation angle of the ultrasonic pulse wave is changed by changing the emission delay or exciting the emission units at different positions, and the variable range of the excitation angle of the focused wave, plane wave or divergent wave is between -90° and 90°. The large-aperture ultrafast ultrasonic imaging system according to claim 1 is characterized in that it also includes a data acquisition module (4), wherein the data acquisition module (4) is used to receive ultrasonic echo signals, realize analog amplification, analog-to-digital conversion, storage, transmission and output digital signals to the image reconstruction module. A large-aperture ultrafast ultrasonic imaging system according to claim 5, characterized in that it also includes a system control module (3), wherein the system control module (3) is used to control the number and distribution of the transmitting units, the properties of the transmitting pulse sequence, the transmitting delay, and the analog amplification gain and sampling rate parameters of the data acquisition module (4). The large-aperture ultrafast ultrasonic imaging system according to claim 6 is characterized in that it also includes an image reconstruction module (5), wherein the image reconstruction module (5) performs image reconstruction by using a delay-sum-based beamforming algorithm. The large-aperture ultrafast ultrasonic imaging system according to claim 7 is characterized in that the image reconstruction module (5) reconstructs the echo signal obtained by exciting a single ultrasonic pulse wave along a certain angle in the ultrafast ultrasonic sequence to form a sub-image, and the gray value of any point on the sub-image is:
I(x,z)=∑ _i RF(i,τ(i,α,x,z),α); Where x, z are the coordinates of any point on the sub-image, α is the ultrasonic pulse wave excitation angle, RF is the ultrasonic echo signal, τ is the ultrasonic propagation time, and the sub-images obtained by different ultrasonic pulse wave excitations are coherently superimposed to obtain the final reconstructed image; i is the index of the ultrasonic transducer unit; The ultrafast ultrasound sequence is a coded transmitted ultrasound pulse wave, wherein the coded transmission simultaneously transmits a plurality of ultrasound pulse waves with coded transmission signal amplitudes and excitation angles in a single transmission event, and decodes the signal before image reconstruction. A large-aperture ultrafast ultrasonic imaging system according to claim 8, characterized in that the large-aperture ultrasonic transducer array (2) is composed of one or more arc-shaped ultrasonic transducer arrays, the ultrafast ultrasonic sequence in a single emission event includes a plurality of plane waves with different excitation angles and different signal amplitudes, and the steps of spatial domain encoding and decoding are as follows: S1: construct Hadamard matrix; S2: In each emission event, according to the elements of each row or column of the Hadamard matrix, the emission units in multiple different regions are excited simultaneously with the emission sequence corresponding to the amplitude weight; S3: summing the ultrasonic echo signals of different emission events according to the amplitude weight of each emission event to synthesize the echo signal of the ultrasonic pulse wave with a single excitation angle. An ultrafast ultrasonic imaging method of a large-aperture ultrafast ultrasonic imaging system according to any one of claims 1 to 9, characterized in that it comprises the following steps: Step 1: The ultrasonic transmitting module (1) generates a transmitting pulse sequence to excite the large-aperture ultrasonic transducer array (2), wherein the transmitting pulse sequence excites the transmitting units on the large-aperture ultrasonic transducer array simultaneously or according to the transmitting delay to generate ultrasonic pulse waves, and multiple ultrasonic pulse waves generated by the excitation of multiple transmitting pulse sequences constitute a group of ultrafast ultrasonic sequences; Step 2: The large-aperture ultrasonic transducer array (2) receives the transmission pulse sequence generated by the ultrasonic transmission module (1), and transmits ultrasonic pulse waves to the object to be measured at a large-aperture ultrasonic excitation angle to cover the target imaging range; Step 3: The large-aperture ultrasonic transducer array (2) detects the ultrasonic echo signal from the object to be measured at a large-aperture ultrasonic detection angle and transmits it to the data acquisition module, performs analog-to-digital conversion, stores, transmits and outputs the digital signal to the image reconstruction module (5) for further ultrasonic image reconstruction.