Ultrasound shear wave elastography method and system based on dynamic tracking window

Abstract

The application discloses an ultrasonic shear wave elasticity imaging method and system based on a dynamic tracking window, and the method comprises the following steps: selecting an ROI region on a B-mode ultrasonic image corresponding to a biological tissue to be measured; configuring a slidable dynamic tracking window in the ROI region; exciting a shear wave at a push focus; performing tracking scanning of a scanning block in the dynamic tracking window; calculating time-stamped tissue displacement data according to a tracking echo signal and a preset reference signal; updating the position of the dynamic tracking window according to the time stamp and at a preset sliding speed; repeatedly performing tracking scanning of the scanning block on the dynamic tracking window; and performing shear wave velocity inversion on the tissue displacement data to obtain shear wave velocity distribution and corresponding shear modulus distribution in the ROI region. The application significantly improves the equivalent time sampling rate in the window without increasing the hardware cost, and effectively alleviates the problem of insufficient sampling rate in imaging of a large range of interest regions or high-wave-velocity tissues.

Description

Technical Field

[0001] This invention relates to the field of ultrasound imaging technology, and more specifically to an ultrasound shear wave elastography method and system based on a dynamic tracking window. Background Technology

[0002] Ultrasonic shear wave elastography (SWE) relies on high-intensity acoustic radiation force pulses to apply force to biological tissue, exciting shear waves that propagate laterally within the tissue. By capturing the minute tissue displacements induced by these shear waves using high-frame-rate detection, the propagation velocity of the shear waves can be obtained. Based on the isotropic linear elastic tissue mechanics assumption, the tissue shear modulus and Young's modulus can be calculated using the formulas \(G=ρ·c_s²\) and \(E≈3·ρ·c_s²\), respectively. This imaging technology is widely used in clinical scenarios such as liver fibrosis grading, elasticity detection of thyroid and breast lesions, and musculoskeletal injury assessment. Due to the low-speed propagation characteristics of shear waves, SWE imaging systems require kilohertz-level time sampling rates, placing high demands on the timing design of the equipment's transmission and reception.

[0003] In existing technologies, there are four mature mainstream imaging schemes in the industry: the first is the ultrafast plane wave imaging scheme of SSI (Supersonic Imagine), which relies on a single plane wave transmission to acquire full field-of-view data and achieve an ultra-high equivalent shear wave tracking frame rate; the second is the TAST time-aligned tracking scheme proposed by GE, which improves the sampling efficiency of a single transmission by using parallel beamforming of multiple receiver lines within the ROI (Region of Interest), and completes full-area imaging by combining multi-cycle data time-series stitching; the third is the comb push scheme, which synchronously transmits multiple sets of excitation pulses to generate multi-source shear waves, and uses a directional filtering algorithm to separate the effective unidirectional shear wave signal; the fourth is the classic ARFI acoustic radiation force pulse imaging scheme, which adopts a point-by-point serial "push-track" scanning logic to complete the acquisition of tissue elasticity parameters pixel by pixel.

[0004] The four mainstream imaging schemes mentioned above all have different technical problems: The first type of defect is that it is impossible to balance frame rate and imaging resolution. Planar wave schemes rely on sacrificing lateral resolution and echo signal-to-noise ratio to achieve a high tracking frame rate, while ARFI, comb push and other schemes require multiple complete excitation tracking cycles to cover the entire detection area, resulting in low imaging efficiency. The second type of defect is that the tracking frame rate under the traditional focused ultrasound architecture has a hard upper limit. The highest effective sampling rate of imaging is constrained by the pulse repetition frequency and the total number of scan lines in the region of interest. Organs with large detection fields and high shear wave velocities, such as the thyroid gland and muscles, are prone to insufficient sampling and loss of shear wave signals. The third type of defect is that all existing schemes use a fixed range of region of interest scanning sequences, failing to utilize the physical characteristics of shear wave propagation—that at any given time the shear wave is only distributed within a narrow range in the detection area. This results in the continuous acquisition of a large amount of invalid tissue area data without effective shear wave signals, causing a waste of computing power and transmission resources.

[0005] In summary, existing technologies cannot dynamically adjust the scanning range based on the real-time propagation state of the shear wave while maintaining compatibility with traditional line-scan ultrasound hardware architecture, making it difficult to simultaneously meet the requirements of high imaging resolution, high shear wave tracking frame rate, and low hardware modification costs. Summary of the Invention

[0006] In view of this, embodiments of the present invention provide an ultrasonic shear wave elastography method and system based on a dynamic tracking window, so as to at least solve the problem that the prior art cannot dynamically adjust the scanning range according to the real-time propagation state of the shear wave while being compatible with the traditional line-scan B-ultrasound hardware architecture.

[0007] The embodiments of the present invention provide the following technical solutions: This invention provides an ultrasonic shear wave elastography method based on a dynamic tracking window, comprising: Select a region of interest (ROI) on the B-mode ultrasound image corresponding to the biological tissue to be tested; Configure a sliding dynamic tracking window within the ROI area; A push wave is emitted within the biological tissue to be tested to excite the shear wave at the push focus. During the propagation process, the instantaneous distribution area of ​​the shear wave within the ROI region can be tracked and covered by the dynamic tracking window. Within the dynamic tracking window, a tracking scan of the scan block is performed, tracking echo signals are acquired, and the timestamps of each tracking transmit-receive signal in each tracking scan are recorded. The time-stamped tissue displacement data is calculated based on the tracking echo signal and the preset reference signal; Based on the timestamp, the position of the dynamic tracking window is updated at a preset sliding speed, causing it to slide towards the far end of the ROI along the predetermined propagation direction of the shear wave. Repeatedly scan the dynamic tracking window after the position is updated, and perform subsequent operations until the required number of scan blocks are collected. Shear wave velocity inversion is performed on the time-stamped tissue displacement data to obtain the shear wave velocity distribution and the corresponding shear modulus distribution within the ROI region.

[0008] Preferably, the method for calculating the required number of scans for a block includes: Obtain the preset range of shear wave velocity of the biological tissue under test and the distance from the far boundary of the ROI region to the push focus; The window size and total acquisition time of the dynamic tracking window are calculated based on the distance and the preset range of wave speed, and the preset sliding speed of the window is calculated based on the preset range of wave speed. Based on the window size and the lateral coverage width that can be estimated by displacement in a single tracking transmit-receive, the number of tracking transmits required for each scan block is determined, and then the scan duration of a single scan block is determined based on the number of tracking transmit-receives and the pulse repetition frequency; The required number of scans for a single scan block is calculated based on the total acquisition time and the scan time of a single scan block.

[0009] Preferably, the window size W of the dynamic tracking window is calculated by the following formula: W = D·(1 - v_min / v_max)+ δ, where D is the distance from the push focus to the far boundary of the ROI, v_min and v_max are the lower limit and upper limit of the preset range of the wave speed, and δ is the protection redundancy; when the calculated W ≥ D, the system reverts to scanning the entire ROI area.

[0010] Preferably, configuring a slidable dynamic tracking window within the ROI region includes: Initialize the center position of the dynamic tracking window to a position that aligns the starting boundary of the dynamic tracking window with the push focus; and / or Before performing a tracking scan of a scan block within the dynamic tracking window, at least one frame of reference signal is acquired for the ROI region or a predetermined tracking region as a baseline reference for subsequent tissue displacement data calculation. The reference signal includes radio frequency (RF) data or in-phase quadrature (IQ) data.

[0011] Preferably, updating the position of the dynamic tracking window according to a preset sliding speed includes: The candidate center position of the dynamic tracking window is calculated based on the preset sliding speed and the timestamp; When the candidate center position exceeds the far boundary of the ROI region, the center position of the dynamic tracking window is locked at the far boundary of the ROI region so that the dynamic tracking window remains within the ROI region.

[0012] Preferably, during the repeated scanning of the dynamic tracking window at the updated position, If the amplitude of the shear wave decays below a preset amplitude threshold before the required number of scans is achieved, the area not fully covered is marked with low confidence, or all scan blocks within the dynamic tracking window are rescanned.

[0013] Preferably, the shear wave velocity inversion of the time-stamped tissue displacement data includes: The tracking echo signal obtained from each tracking scan is cross-correlated with the reference signal or the phase difference is calculated to obtain the tissue displacement data at each spatial location; Based on the tissue displacement data and the corresponding timestamp, shear wave velocity inversion is performed.

[0014] Preferably, before performing a tracking scan of the scan block within the dynamic tracking window, the method further includes: Perform a low-density or short-duration push-track pre-acquisition, wherein the push-track includes a push pulse and multiple tracking transmissions; Based on the arrival time difference or cross-correlation between adjacent tracking lines in the pre-collection, the coarse shear wave velocity of the biological tissue to be tested is estimated. Based on the rough shear wave velocity and the preset error tolerance, the preset range of the wave velocity is narrowed; If the pre-collected signal-to-noise ratio does not reach the preset threshold, the preset range of shear wave velocity is retained.

[0015] Preferably, after completing the scanning and acquisition of the required number of scan blocks, the method further includes: Without exciting the shear wave, background data is collected according to the same scanning sequence as the tracking scan; Calculate the background vibration intensity based on the aforementioned background data; The signal vibration intensity is calculated based on the tissue displacement data obtained from the tracking scan. Calculate the quality evaluation index based on the signal vibration intensity and the background vibration intensity; When the quality evaluation index is lower than the preset confidence threshold, a low confidence prompt message is output.

[0016] Preferably, performing tracking transmission and reception within the dynamic tracking window includes: The tracking transmission is performed using a diffused wave emission method with the virtual focus located on the back of the ultrasound probe, in order to increase the lateral coverage width of a single tracking transmission; Within the dynamic tracking window, beamforming and displacement estimation are performed on the received diffuse echo signal.

[0017] This invention also provides an ultrasonic shear wave elastography system, comprising: an ultrasonic probe, a transmitting module, a receiving module, a beamforming module, a dynamic tracking control module, a shear wave elastography estimation module, and a display and interaction module; The dynamic tracking control module is used to control the configuration and sliding of the dynamic tracking window, and to control the launching module to perform tracking scanning of the scanning block and updating the window position as in any of the above methods. The shear wave elastic estimation module is used to perform shear wave velocity inversion based on the tissue displacement data to obtain the shear wave velocity distribution and the corresponding shear modulus distribution within the ROI region. The display and interaction module is used to display B-mode ultrasound images, ROI selection interfaces, flexible pseudo-color images, and quality prompts.

[0018] Compared with the prior art, the beneficial effects that the at least one technical solution adopted in the embodiments of the present invention can achieve include at least: The present invention discloses an ultrasonic shear wave elastography method based on a dynamic tracking window. By utilizing the physical characteristic that shear waves occupy only a narrow spatial band at any given time, the limited pulse repetition frequency resources are concentrated on the currently effective wavefront region. This significantly improves the equivalent time sampling rate within the window without increasing hardware costs, thereby effectively alleviating the problem of insufficient sampling rate in imaging large regions of interest or high-wave velocity tissues and avoiding the problem of shear wave loss. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1-2 This is a flowchart of an ultrasonic shear wave elastography method based on a dynamic tracking window, according to an embodiment of the present invention. Figure 3 This is a schematic diagram illustrating the geometric derivation of the tracking window size according to an embodiment of the present invention; Figure 4 For the existing tracking scan timing diagram; Figure 5 This is a timing diagram for dynamic tracking in an embodiment of the present invention; Figure 6 This is a schematic diagram illustrating the dynamic following window following the propagation of a shear wave according to an embodiment of the present invention; Figure 7 This is a flowchart of the background noise verification and quality evaluation after scanning according to an embodiment of the present invention; Figure 8 This is a comparison diagram of focused wave emission (left) and diffused wave emission (right) according to an embodiment of the present invention; Figure 9 This is a comparison chart of window tracking rates under different organs in an embodiment of the present invention. Detailed Implementation

[0021] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0022] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. This application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0023] It should be noted that various aspects of embodiments within the scope of the appended claims are described below. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this application, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number and aspects set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using structures and / or functionalities other than one or more of the aspects set forth herein.

[0024] It should also be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of this application. The drawings only show the components related to this application and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0025] Additionally, specific details are provided in the following description to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that practice can be carried out without these specific details.

[0026] Based on this, the embodiments of this specification propose a processing solution: such as Figure 1-2 As shown, this invention proposes an ultrasonic shear wave elastography method based on a dynamic tracking window. After selecting a Region of Interest (ROI) on a B-mode ultrasound image, a dynamic tracking window that can slide along the shear wave propagation direction is set to cover the instantaneous distribution area of ​​the shear wave in real time. The required number of scan blocks M is pre-calculated by setting the shear wave velocity range, the distance to the far end of the ROI, the window size, and the sliding speed, ensuring that the shear wave reaches the far end of the ROI throughout its entire propagation. During actual acquisition, the shear wave is first excited, then a scan block is completed within the current window, and a timestamp is recorded. The window position is then updated according to the preset sliding speed, and the scan is repeated the required number of times. Finally, all time-stamped displacement data are integrated to perform wave velocity inversion and obtain the shear modulus distribution. This achieves effective signal coverage with fewer scan lines, significantly improving the imaging frame rate and signal-to-noise ratio.

[0027] The symbols used in the formulas of this invention are explained below: The symbol ceil(·) represents rounding up (i.e., the smallest integer not less than the parameter), and the symbol floor(·) represents rounding down; the coverage criteria of w=ceil(W / d) and N=ceil(D / d) are used uniformly, that is, w tracing lines must completely cover window W and N lines must completely cover ROI.

[0028] The technical solutions provided by the various embodiments of this application are described below with reference to the accompanying drawings.

[0029] like Figure 1-6 As shown, this embodiment of the invention provides an ultrasonic shear wave elastography method based on a dynamic tracking window, comprising: Step S1: Select a region of interest (ROI) on the B-mode ultrasound image corresponding to the biological tissue to be tested.

[0030] The Region of Interest (ROI) is the effective imaging area manually selected by the operator on the B-mode ultrasound anatomical image of the biological tissue to be tested, used for shear wave elastography detection. It is the global effective boundary range of all scanning operations, parameter calculations, and elastography outputs in this invention. Its main purpose is to accurately locate the target tissue area to be detected, shield irrelevant tissue outside the ROI, avoid invalid calculations and interference signals, and set scanning constraint boundaries for the dynamic tracking window.

[0031] Step S2: Configure a sliding dynamic tracking window within the ROI area; The dynamic tracking window is a local scanning area limited to a single block ultrasound transmission and reception, located within the Region of Interest (ROI). Its width is determined by the tissue wave velocity and the ROI geometry. It can slide along the shear wave propagation direction at a preset speed to cover the narrow band region where the shear wave is instantaneously located in real time. The dynamic tracking window does not refer to a spatially fixed rectangle, but rather a sampling mask that dynamically adjusts in time as the shear wavefront moves.

[0032] Step S3: A push wave is emitted within the biological tissue to be tested to excite the shear wave at the push focus. During the propagation process, the instantaneous distribution area of ​​the shear wave within the ROI region can be tracked and covered by the dynamic tracking window.

[0033] In this embodiment of the invention, a high-intensity acoustic radiation force pulse is typically emitted by an ultrasonic probe to the focal point within the tissue. The acoustic radiation force effect is used to drive the tissue particles to generate lateral vibration, thereby forming an outward propagating shear wave.

[0034] From the perspective of physical propagation characteristics, when shear waves propagate within biological tissue, their vibrational energy is concentrated in a narrow, localized wavefront region at any given moment, rather than being uniformly distributed across the entire region of interest (ROI) imaging area. This invention fully utilizes this inherent physical prior, abandoning the inefficient mode of traditional elastography that evenly distributes sampling resources across the entire ROI. Instead, it dynamically focuses ultrasound emission and sampling resources onto the effective wavefront region instantaneously occupied by the shear wave, achieving targeted, dense sampling of the effective signal. This significantly improves the temporal sampling density of the effective shear wave field while reducing resource waste caused by ineffective sampling across the entire region.

[0035] For example, when the shear wave is first excited, the dynamic tracking window is located near the push focus; as the shear wave propagates further away, the window moves synchronously, always aligning the high frame rate sampling with the current peak position. This design allows the system to significantly increase the sampling density of the effective signal region without increasing the hardware pulse repetition frequency limit.

[0036] Steps S1-S3 define the Region of Interest (ROI) based on the ultrasound image, lock the target tissue to be measured, limit the effective range of subsequent window sliding and data acquisition, isolate irrelevant tissue interference, and set up a dynamic tracking window within the ROI. Based on the physical characteristics of the instantaneous local distribution of shear waves, the basis for local follow-up sampling is established. Finally, by setting the window to move with the wave and cover the instantaneous wave zone in real time, the hardware scanning partitioning basis is provided for subsequent block-based directional acquisition and centralized sampling of effective shear wave signals.

[0037] Step S4, in the dynamic tracking window [x_c Within [W / 2, x_c+W / 2], a tracking scan of the scan block is performed, the tracking echo signal is acquired, and the timestamp of each tracking transmit-receive signal in each tracking scan is recorded. Within each dynamic tracking window, multiple scan block scans are required, and each scan block tracking scan consists of w tracking transmit-receive cycles, where w satisfies w*d≥W.

[0038] Right now w=ceil(W / d); Where d is defined as the center-to-center distance between adjacent tracking transmissions, or it can be defined as the lateral coverage width that a single transmission can form for displacement estimation under parallel beamforming conditions; each transmission-reception cycle records the transmission timestamp t_k.

[0039] In this invention, dynamic tracking restricts the scanning range to within the tracking window W, and the number of emission times per block is w = ceil(W / d). The tracking rate within the window is: f_new=PRF / w=PRF / ceil(W / d) Since the w transmissions within a block are not simultaneous, and the shear wave continues to propagate during block scanning, each tracking line records a transmission timestamp t_k, and velocity inversion uses the actual sampling time. The window center position x_c can be updated according to the start / center time of each block or the timestamp of each tracked transmission to reduce timing errors within the block. The improvement in tracking rate within the window of this invention compared to traditional methods, f_new / f_trad=ceil(D / d) / ceil(W / d), mainly depends on the wave velocity range and ROI geometry, and is not directly related to the probe model or PRF.

[0040] In this embodiment of the invention, when parallel beamforming is enabled for tracking transmission and multiple receive lines can be generated in a single transmission, w is taken as the minimum number of transmissions required to cover the window W.

[0041] In this embodiment of the invention, tracking scanning refers to a dedicated scan that directionally emits tracking ultrasound beams and receives radio frequency signals from tissue echoes within a dynamic window. It collects echo data corresponding to the micro-deformation of tissue caused by shear wave disturbance, which is the original data source for subsequent time-domain displacement estimation. Furthermore, it focuses on the window where the instantaneous wavefront is located, thereby achieving concentrated sampling of effective signals, improving the sampling density of effective data, and suppressing noise interference from irrelevant areas.

[0042] The timestamp is the timestamp corresponding to each tracking transmission. It is mainly used to combine the preset window sliding speed and the single block time to calculate the single sliding distance of the window, update the center position of the window, realize the window to move synchronously with the wavefront, and support the wave speed inversion solution.

[0043] By setting w to satisfy w*d≥W, multiple beams are horizontally stitched to cover the entire dynamic window space, ensuring that all areas to be measured within the window are covered by the beams. This avoids both insufficient transmissions causing local missed sampling and redundant invalid sampling caused by transmission redundancy, thus accurately matching the window space span.

[0044] Because the dynamic tracking window only covers a portion of the ROI, the number of tracking transmissions required for a single scan block is far fewer than in a traditional full ROI scan. This allows for a significant increase in the equivalent time sampling rate within the window at the same pulse repetition frequency. Simultaneously, since the window itself slides over time, and there are time intervals between multiple transmissions within the scan block, it is essential to accurately record the actual timestamp or relative time offset of each tracking transmission-reception sequence to eliminate timing errors introduced by window movement and discrete sampling.

[0045] Step S4 uses the scan block as the smallest time-series acquisition unit, limiting local sampling to only within the dynamic window covering the instantaneous wavefront; by constraining the number of transmissions to satisfy w·d≥W, it ensures that a single block completely covers the horizontal scanning range of the window and has no sampling blind spots; and simultaneously retains the scanning time-series data to provide original sampling data and time reference for subsequent window position iteration updates and quantitative inversion of shear wave velocity, thus avoiding invalid scanning of the entire ROI while locking the effective signal area.

[0046] Step S5: Calculate the timestamped tissue displacement data based on the tracking echo signal and the preset reference signal.

[0047] Tissue displacement data, used as direct input for shear wave velocity inversion, is a core physical quantity in ultrasound shear wave elastography (SWE). It refers to the minute spatial displacement of tissue particles from their original equilibrium position due to shear wave propagation.

[0048] Step S5 uses a combination of a preset reference signal and a timestamp to transform the low-amplitude, high-time-density echo data acquired within the dynamic window into an accurate and quantifiable tissue displacement-time series, thereby providing a reliable data foundation for subsequent shear wave velocity imaging.

[0049] Step S6: Update the position of the dynamic tracking window according to the timestamp at a preset sliding speed, so that it slides towards the far end of the ROI along the predetermined propagation direction of the shear wave.

[0050] like Figure 4shown in the figure, is a conventional tracking scanning timing diagram. In the traditional method, a frame is used as the basic acquisition unit, and for each frame, N scan lines within the entire ROI need to sequentially complete one transmission-reception, with the scan line numbers increasing linearly from 1 to N over time. When the shear wavefront propagates across the ROI, each frame only collects a small number of discrete scan line sampling points at the current position of the wavefront within its frame duration. Due to the long scanning gap between frames, signal loss and aliasing are highly prone to occur when the shear wave propagates through the current scanning area within the frame interval.

[0051] As shown in Figure 5 shown in the figure, is a dynamic follow-up tracking timing diagram of an embodiment of the present invention. The present invention reconstructs the traditional frame-based acquisition mode into one that uses a scan block as the basic acquisition unit: each block only sequentially completes transmission-reception for w scan lines covered by the current dynamic tracking window (where w<N), and the scan line number range advances block by block in the diagonal direction toward the far end of the ROI as the window slides; each block marked by the dashed box in the figure is arranged diagonally in the time-scan line coordinate system, which is substantially consistent with the propagation direction of the shear wavefront, so that the acquisition time of each block is synchronously aligned with the current position of the wavefront, thereby realizing continuous and seamless tracking of the wavefront.

[0052] As shown in Figure 6 shown in the figure, is a schematic diagram of the dynamic follow-up window following the propagation of the shear wave according to an embodiment of the present invention. This figure intuitively demonstrates the position evolution process of the dynamic tracking window during the propagation of the shear wave from the spatial dimension: at the initial moment, the window is located near the push focus (aligned with the shear wave excitation position), and as the shear wave propagates toward the far end of the ROI at a preset sliding speed V_slide, the center position x_c of the window moves forward synchronously according to x_c(t_k)=clip(V_slide·t_k, W / 2, D W / 2), so that the window always covers the narrow-band wavefront area where the shear wave is instantaneously located; the window positions corresponding to different time points in the figure are connected in series in sequence to form a continuous covering path along the propagation direction of the shear wave, which ensures that the signals of the entire process of the shear wave from excitation to crossing the far end of the ROI are effectively collected, and avoids signal loss in the scanning gap of the traditional method.

[0053] As shown in Figure 5-6 shown in the figure, step S6 can update the center position of the tracking window according to the following formula, so that the window slides toward the far end of the ROI along with the shear wavefront: x_c(t_k)=clip(V_slide·t_k, W / 2, D W / 2) wherein, clip(·) is a double-boundary clipping operation, which ensures that the window is always located inside the ROI; the update of the window center takes the center moment of each block or the timestamp of each tracking transmission as the independent variable.

[0054] In this embodiment of the invention, when V_slide·t≥D When W / 2, x_c is clipped to D. W / 2, the right side of the window touches the far end of the ROI.

[0055] In this invention, the window displacement is not predetermined but tightly coupled with the actual acquisition timing. The system calculates the distance the window should move based on a preset sliding speed and the actual time consumed, thereby ensuring that the next scan block accurately continues the coverage area of ​​the previous scan block, achieving continuous and seamless tracking of the shear wavefront. It should be understood that although this embodiment describes an update method based on a predetermined sliding speed, in other possible implementations, the window position can also be fine-tuned by combining real-time feedback signal characteristics, as long as the window's wavefront following characteristics are maintained.

[0056] Step S6 calculates the displacement increment based on the window sliding speed and the time taken for a single block scan, and translates the window one by one to make the window moving rate match the shear wave travel rate, continuously covering the instantaneous wavefront that is constantly propagating forward, thereby achieving concentrated sampling only of the effective wavefield.

[0057] Furthermore, the window gradually slides from the focus of the push to the far end of the ROI, sampling in stages and segments. Without performing a full-area scan at once, it completely collects the entire propagation link data of the shear wave from the starting point to the far end of the ROI, ultimately ensuring that the elastic parameters of the entire region can be inverted. The window is always limited to a narrow area of ​​the instantaneous wavefront, and the scanning range switches synchronously with the wavefront movement, avoiding blank tissue areas without shear waves throughout the entire process, continuously reducing redundant sampling and increasing the effective signal sampling density.

[0058] In summary, step S6 dynamically adjusts the window coordinates based on the scanning time and preset sliding speed, so as to realize that the tracking window moves forward synchronously with the shear wave front, and traverses the complete propagation path of the shear wave in segments, thus avoiding invalid scanning of the entire domain on the basis of complete data across the entire link.

[0059] Step S7: Repeat the scanning of the updated dynamic tracking window blocks and perform subsequent operations until the required number of scan blocks have been collected. Through this iterative mechanism, the system discretizes the originally continuous time axis into a series of interconnected or appropriately overlapping scan block sequences. Each scan block corresponds to a segment of local spatiotemporal data on the shear wave propagation path. Finally, the data collected from all scan blocks are stitched together on the time axis to form a complete record of the shear wave propagation process within the entire ROI region.

[0060] In step S7, the required number of scans M for each scan block is calculated based on the maximum duration of the slowest shear wave traversing the ROI. This process is repeated until M scans are completed, ensuring that the entire process of the low-speed shear wave traveling from the push focus to the far end of the ROI is captured completely, avoiding data truncation due to insufficient sampling steps. Furthermore, the spatiotemporal process of continuous shear wave propagation is divided into multiple independent block acquisitions. Each cycle only performs a local scan within the window of the instantaneous wavefront, abandoning synchronous sampling across the entire ROI, which continuously reduces invalid sampling and increases the effective signal sampling density. Since each scan block corresponds to a segment of local spatiotemporal data of the shear wave, all block data are spliced ​​and fused along the time axis to form a complete time-series dataset covering the entire ROI, providing complete raw data for the full-domain inversion of shear wave velocity and shear modulus. Finally, in conjunction with the shear wave amplitude attenuation threshold rule, if the wave signal attenuates prematurely and fails, the cycle can be terminated early, avoiding unnecessary redundant scanning and optimizing imaging acquisition efficiency.

[0061] Furthermore, during the repeated tracking and scanning of the dynamic tracking window after the update position, if the amplitude of the shear wave attenuates to below a preset amplitude threshold before reaching the required number of scan acquisitions, the area not fully covered is marked with low confidence, or all scan blocks within the dynamic tracking window are rescanned.

[0062] Specifically, if the shear wave amplitude decays below the threshold before the number of acquisitions reaches M, the area not fully covered is marked with low confidence, or the process reverts to full ROI scanning / reacquisition. In order to mark or supplement the blank areas of the ROI that have not been traversed by the window when the shear wave decays prematurely and the remaining blocks are no longer acquired, local imaging defects are eliminated.

[0063] In step S7, if the shear wave amplitude attenuates below a preset amplitude threshold during the scanning process, the scanning acquisition is terminated. This adaptive stopping mechanism is an important supplement to the fixed number of acquisitions M. In actual clinical scenarios, the tissue attenuation characteristics of different patients vary greatly, and sometimes the shear wave has completely dissipated before reaching the distal end of the ROI. If the remaining M scans are mechanically performed in this case, not only will no effective signal be obtained, but the examination time will also be prolonged and unnecessary acoustic radiation dose will be increased. By monitoring the signal amplitude in real time and comparing it with the preset threshold, the system can intelligently determine the end of the shear wave's life cycle and release resources immediately once the signal is confirmed to be unusable. This not only improves examination efficiency but also reflects the solution's focus on patient safety and experience. The threshold can be an absolute amplitude threshold or a signal-to-noise ratio threshold relative to the background noise; this invention does not limit this.

[0064] In summary, step S7 achieves closed-loop sampling control based on the total number of acquisitions M. By cyclically and discretely acquiring and stitching together the spatiotemporal data of each block, the entire propagation process of shear waves within the ROI is fully reproduced on the basis of efficient local sampling, taking into account both sampling completeness and acquisition efficiency.

[0065] Step S8: Perform shear wave velocity inversion on the tissue displacement data with timestamps to obtain the shear wave velocity distribution and the corresponding shear modulus distribution within the ROI region.

[0066] Among them, shear wave velocity inversion can be displacement estimation based on the phase difference method and wave velocity inversion based on cross-correlation or TOF fitting.

[0067] Specifically, the update of the window center position x_c(t_k) uses the timestamp t_k of each tracking transmission as the independent variable, or the center time t_block_k of each block as the independent variable. The shear wave velocity inversion is based on the displacement sequence with timestamps and adopts a wave velocity inversion method that combines phase difference displacement estimation with cross-correlation or time-of-flight (TOF) fitting.

[0068] In step S8, because the collected data contains precise timestamp information, the inversion algorithm can accurately reconstruct the displacement change curve of each spatial point on the real physical time axis, and then calculate the shear wave velocity using algorithms such as the phase difference method, time-of-flight method, or cross-correlation method. The final generated elasticity map not only reflects the stiffness distribution of the tissue, but also has a higher signal-to-noise ratio and spatial resolution due to the high sampling rate.

[0069] Shear wave velocity inversion is a numerical calculation process that uses tissue micro-displacement and timestamp information collected at different times, combined with a physical model of shear wave propagation, and algorithms such as time-domain cross-correlation to inversely solve the actual propagation velocity of the shear wave at each location from the spatiotemporal changes of displacement. It is the core computational step that transforms sampled data into wave velocity parameters.

[0070] Shear wave velocity distribution is a spatial distribution map of the shear wave propagation velocity corresponding to each pixel position in the ROI space. It intuitively represents the difference in shear wave speed in tissues at different locations and is used as an intermediate quantitative result to reflect the softness and hardness differences of local tissues.

[0071] Shear modulus distribution is a spatial distribution map of shear modulus calculated from the shear wave velocity at each point based on the constitutive relationship of elasticity. Shear modulus is an intrinsic physical quantity characterizing the stiffness of biological tissue, and this distribution is the final elastic imaging result, used for tissue lesion screening and elasticity assessment.

[0072] After acquiring one or more frames of reference RF data or in-phase quadrature IQ data in the ROI region or at least the predetermined tracking region as a baseline reference for displacement estimation, in step S7, the RF data or IQ data obtained from each tracking scan are cross-correlated or phase difference calculated with the baseline reference to obtain displacement estimates for each spatial location; and based on the displacement estimates and the corresponding timestamps, shear wave velocity inversion is performed.

[0073] In summary, step S8 summarizes the segmented displacement sampling data with timestamps from the entire process, solves the physical parameters from the tissue deformation time domain information through inversion calculation, and finally outputs the ROI global elastography results; relying on the complete time-series data with timestamps, the accuracy of inversion calculation is ensured, the elasticity of the tissue under test is visualized and the imaging loop from raw ultrasound echo data to clinically usable elasticity parameter maps is completed.

[0074] Through steps S1-S8, this embodiment switches the scanning strategy from static full-field to dynamic local following, essentially a software-managed gain technique that does not change the existing focusing and transmitting hardware architecture. By utilizing the spatiotemporal sparsity of shear wave propagation, the limited system sampling capacity is concentrated on the most valuable signal region, thus overcoming the constraints of frame rate and field of view in traditional methods and solving the problem of insufficient sampling rate in large regions of interest or high-wavelength tissue imaging in existing technologies.

[0075] The method for calculating the required number of scans for a scan block includes: obtaining the preset range of the shear wave velocity of the biological tissue under test and the distance from the far boundary of the ROI region to the push focus; calculating the window size and total acquisition time of the dynamic tracking window based on the distance and the preset range of the wave velocity, and calculating the preset sliding speed of the window based on the preset range of the wave velocity; determining the number of tracking transmissions required for each scan block based on the window size and the lateral coverage width that can form a displacement estimate by a single tracking transmission-reception, and then determining the scan time of a single scan block based on the number of tracking transmission-receptions and the pulse repetition frequency; and calculating the required number of scans for the scan block based on the total acquisition time and the scan time of a single scan block.

[0076] The preset range of shear wave velocity [v_min, v_max] corresponding to the biological tissue under test is a range of shear wave velocity values ​​[vmin, vmax] pre-calibrated based on the inherent elastic properties of different biological tissues in the human body. These are empirical prior parameters corresponding to the tissue: different organs (liver, breast, skeletal muscle, etc.) have different textures, and the shear wave propagation velocity naturally falls within a fixed range. This value is pre-loaded into the system before imaging.

[0077] The dynamic tracking window is the effective transverse scanning width W along the shear wave propagation direction, which is the transverse coverage range of the ultrasonic beam in a single scan block.

[0078] In this embodiment, the formulas for calculating the dynamic tracking window size W and the sliding speed V_slide are as follows: W=D·(1 v_min / v_max)+δ V_slide=(v_min+v_max) / 2 Where δ is the protection redundancy, with a value range of 0–10 mm, preferably 2–5 mm, used to accommodate the diffraction broadening and edge attenuation of the wavefront; if W≥D is calculated by the above formula, that is, the window is no smaller than the ROI, then the system reverts to scanning the entire ROI, where D is the distance between the far boundary of the ROI region and the push focus.

[0079] When δ is large and D is small, or when v_min / v_max is small, resulting in W≥D in the formula calculation, the system reverts to a traditional full ROI scan and prompts the operator.

[0080] Specifically, such as Figure 3 As shown, the derivation of the tracking window size W is as follows: In a simplified model of uniform, unidirectional propagation, it is assumed that the shear wave is simultaneously excited from the pushing focus at the lateral position x=0 and propagates within a preset wave velocity range [v_min, v_max]. Let the time when the fastest wavefront reaches the far end D of the ROI be t*=D / v_max, then at that time, the slowest wavefront is located at: x_min(t*)=v_min·t*=D·v_min / v_max.

[0081] To ensure that the tracking window W always contains both the fastest and slowest wavefronts within the interval (0, t*] (i.e., before the shear wave crosses the ROI), W must be at least the distance between the fastest and slowest wavefronts: W_min=D x_min(t*)=D·(1 v_min / v_max) Considering diffraction broadening, wavefront edge attenuation, and estimated instabilities at the boundaries, a protective redundancy δ is introduced to obtain the complete window size formula. The sliding velocity V_slide at the center of the window is taken as the midpoint velocity of the fastest and slowest wavefronts, and is calculated when V_slide·t exceeds [W / 2, D]. When the range is W / 2], it is locked at the boundary by clip.

[0082] Note: The above derivation is based on a simplified model of uniform, unidirectional, one-dimensional propagation. In real tissues that are non-uniform, anisotropic, attenuated, or have boundary reflections, robustness should be improved by: (a) appropriately increasing the protection redundancy δ; (b) enabling the background verification of Strategy 2; and (c) allowing window overlap between adjacent blocks or reverting to a full ROI scan when the estimation reliability decreases.

[0083] In this embodiment, a scan block is defined as the smallest temporal acquisition unit, representing a complete local tracking scan process, rather than just a spatial block. The logic for determining the number M is to assume that the shear wave propagates at a minimum speed within a preset range, calculate the maximum time required for it to traverse the entire ROI, and then divide it by the execution time of a single scan block, thereby ensuring that even under the slowest wave speed conditions, the entire process of the shear wave traversing the ROI can be completely captured.

[0084] As a preferred implementation method, the total collection time Satisfy ,in The distance between the far boundary of the ROI region and the push focus. For the minimum shear wave velocity, To allow for a safety margin, typically 1-5 ms is used to cover the wavefront wake at the boundary; the scan duration for a single scan block... It can be represented as ,in To track the number of launches, The pulse repetition frequency; and then .

[0085] It should be understood that the above formula is only a specific quantitative example. In other implementations, the value of M can also be determined by looking up a table, machine learning prediction model or other empirical formulas, as long as complete coverage of the slowest shear wave can be guaranteed.

[0086] In some embodiments, configuring a slidable dynamic tracking window within the ROI region includes initializing the center position of the dynamic tracking window to a position that aligns the starting boundary of the dynamic tracking window with the push focus.

[0087] The push focus is on the starting position of the shear wave, and the initial edge of the window is aligned with it. This ensures that the first round of block scanning precisely covers the newly generated initial wavefront, preventing the initial segment of the shear wave from escaping the scanning range and the loss of the first segment of data. Furthermore, by ensuring that the initial position of the window is aligned with the starting point of the shear wave, subsequent gradual sliding along the propagation direction allows it to follow the wavefront from near to far across the ROI, and also matches the propagation path of the shear wave from the push point to the far end of the ROI.

[0088] In this embodiment of the invention, in the initial stage, the window starting boundary is aligned with the push focus, thereby establishing a stable displacement baseline reference before the shear wave is fully formed or just formed, so as to facilitate accurate calculation by the subsequent phase difference method.

[0089] In this embodiment of the invention, updating the position of the dynamic tracking window according to a preset sliding speed includes: calculating the candidate center position of the dynamic tracking window based on the preset sliding speed and the timestamp; when the candidate center position exceeds the far boundary of the ROI region, locking the center position of the dynamic tracking window at the far boundary position of the ROI region, so that the dynamic tracking window remains within the ROI region.

[0090] In other words, the embodiments of the present invention introduce boundary locking logic during the sliding process to prevent the window from moving out of the effective imaging area due to accumulated errors in sliding speed or extreme parameter settings.

[0091] For example, when the right boundary of the window touches the far boundary of the ROI, the system stops moving the window to the right and locks its position, continuing to collect data in situ until the shear wave attenuates or the preset number of iterations is reached. This ensures the security of data acquisition and avoids wasting resources in invalid areas.

[0092] As a preferred example, Center of window The update can be performed using a truncation function: ,in For sliding speed, For the current moment, For window size, This represents the distance to the far end of the ROI. This formula ensures the window is always positioned within the ROI using double-boundary clipping. Within the scope. Similarly, this mathematical expression is not the only limitation; any control logic that can achieve the "follow-up + limit" function is within the protection scope of this invention.

[0093] In some embodiments, before performing a tracking scan of the scan block within the dynamic tracking window, the method further includes: performing a low-density or short-duration push-track pre-acquisition, the push-track including a push pulse and multiple tracking transmissions; estimating the coarse shear wave velocity of the biological tissue under test based on the arrival time difference or cross-correlation between adjacent tracking lines in the pre-acquisition; narrowing the preset range of the wave velocity based on the coarse shear wave velocity and a preset error tolerance; and retaining the preset range of the shear wave velocity if the signal-to-noise ratio of the pre-acquisition does not reach a preset threshold.

[0094] Before the tracking scan, a low-density or short-duration push-tracking pre-acquisition is performed (i.e., a push pulse superimposed with a small number of tracking transmissions). Based on the arrival time difference or cross-correlation between adjacent tracking lines, a rough value of the shear wave velocity is estimated. Based on this, [v_min, v_max] is narrowed to [ ·(1 ε), ·(1+ε)](typical ε=0.2–0.3), then calculate W using the narrowed range; if the pre-collected signal-to-noise ratio does not reach the preset threshold, then retain the original preset range.

[0095] Before initiating the formal high-density dynamic tracking acquisition, the system performs a low-density pre-acquisition scan. This pre-acquisition scan typically uses less push pulse energy and a sparser tracking line density. Its purpose is not to generate a high-precision elastic image, but to quickly obtain a coarse estimate of the shear wave propagation velocity within the current region of interest in a very short time. For example, a representative coarse shear wave velocity can be estimated by calculating the time difference between the arrival of displacement peaks on adjacent tracking lines or by using a simple cross-correlation algorithm. This design allows the system to dynamically adjust subsequent master acquisition parameters based on the actual tissue characteristics of the individual patient, rather than mechanically relying on a default wide range based on population statistics.

[0096] After obtaining the coarse shear wave velocity, the system does not directly use it as the new boundary, but instead introduces a preset error tolerance to construct an updated wave velocity range. As a preferred implementation, the updated minimum shear wave velocity can be set as the coarse shear wave velocity multiplied by... The updated maximum shear wave velocity can be set to the approximate shear wave velocity multiplied by [the value]. ,in This is the error tolerance. The setting of the error tolerance reflects a delicate balance between window tightness and leakage risk. If... If the value is too small, although it can maximize the compression of the dynamic tracking window size and thus achieve a very high frame rate, if the actual shear wave velocity deviates from the predicted value due to tissue anisotropy or lesion heterogeneity, it is very easy for the shear wave to escape the window, causing acquisition failure; conversely, if... If the value is too large, the purpose of pre-calibrating the narrowing window is lost. In practical applications, the error tolerance can be configured differently according to organ type or probe frequency. For example, a smaller value (such as 0.1-0.2) can be used in liver examinations with good homogeneity, while a larger value (such as 0.3-0.5) can be used in thyroid or breast examinations with complex structures, in order to balance efficiency and robustness.

[0097] In some of these embodiments, such as Figure 7As shown, after completing the required number of scans of the scan block, the method further includes: acquiring background data according to the same scanning sequence as the tracking scan without exciting the shear wave; calculating the background vibration intensity based on the background data; calculating the signal vibration intensity based on the tissue displacement data obtained from the tracking scan; calculating a quality evaluation index based on the signal vibration intensity and the background vibration intensity; and outputting a low confidence prompt message when the quality evaluation index is lower than a preset confidence threshold.

[0098] Specifically, the flowchart for background noise verification and quality evaluation after scanning includes the following steps: Step 1, under the condition of no shear wave excitation, background data X_noise is acquired according to the same scanning sequence as the main acquisition; Step 2, the background vibration intensity σ_noise is calculated based on the background data; Step 3, the signal vibration intensity σ_signal is calculated based on the tissue displacement data obtained from the tracking scan; Step 4, the quality evaluation index is calculated according to Q=σ_signal / σ_noise based on the signal vibration intensity and the background vibration intensity; Step 5, when the quality evaluation index Q is lower than the preset confidence threshold Q0 (typically 3-5), a low confidence prompt message is output, suggesting that the operator adjust the section or probe position and retain the original data for post-processing.

[0099] After calculating the background vibration intensity and the signal vibration intensity, the system divides the two to obtain the quality evaluation index Q. It is crucial to emphasize that this index is essentially a signal-to-noise ratio (SNR) metric, not simply the absolute signal amplitude. In clinical practice of ultrasound shear wave elastography, the stiffness of different tissues varies greatly; for example, the shear wave displacement amplitude of normal liver tissue and advanced cirrhotic tissue can differ by several times. If only the absolute signal intensity is relied upon to determine data validity, it is highly likely that weak, normal signals from soft tissues will be misclassified as invalid data, or high-amplitude interference caused by motion artifacts in a high-noise background will be mistaken for valid elastic signals. By introducing the background vibration intensity as the denominator for normalization, the quality evaluation index Q effectively isolates the influence of the tissue's inherent stiffness characteristics, focusing on assessing the purity of the signal relative to background disturbances during the current acquisition process.

[0100] Therefore, this mechanism is crucial for identifying false positive or false negative results caused by non-tissue elasticity factors. In actual examinations, a patient's respiratory movements, heartbeats, intestinal peristalsis, and even slight shaking of the probe held by the operator can all generate additional mechanical vibrations in the tissue. These motion artifacts typically manifest as broadband or specific-frequency random noise, significantly increasing the level of background vibration intensity. When such interference is present, even if the main acquisition signal contains genuine shear wave components, its signal-to-noise ratio relative to the increased background noise will decrease significantly, causing the quality assessment index Q to fall below the preset confidence threshold. In this case, the low confidence alert output by the system can promptly warn the operator that the current data is unreliable.

[0101] In some of these embodiments, such as Figure 8 As shown, tracking transmission and reception are performed within the dynamic tracking window, including: performing tracking transmission using a diffuse wave transmission method with the virtual focus located on the back of the ultrasound probe to increase the lateral coverage width of a single tracking transmission; and performing beamforming and displacement estimation on the received diffuse wave echo signal within the dynamic tracking window.

[0102] Specifically, during tracking transmission and reception within the dynamic tracking window, the tracking transmission mode is switched from focused transmission to diffuse wave transmission with the virtual focus located on the back of the transducer. Diffused wave tracking is still limited to beamforming within the dynamic window. Under the condition of meeting the displacement estimation SNR threshold, the lateral coverage width d of a single diffuse wave transmission can be greater than the corresponding width of focused transmission, reducing the number of transmissions and receptions in the scan block, thereby further improving the tracking rate within the window.

[0103] Traditional focused wave emission uses precise delay control to concentrate acoustic energy at a specific focal point within the tissue. Its advantage lies in the extremely high lateral resolution and signal-to-noise ratio of the focal region, but the trade-off is a very narrow effective illumination area per emission, typically covering only the width of a few array element spacings. In scenarios requiring coverage of the entire dynamic tracking window, the system must perform multiple dense focused emissions to complete data acquisition for a single scan block, directly limiting the upper limit of the time sampling rate. In contrast, the diffused wave emission method used in this embodiment applies a reverse delay sequence, causing the emitted wavefront to exhibit a divergent shape as if emanating from a virtual focal point on the back of the ultrasound probe. While this acoustic field characteristic sacrifices some lateral focusing gain, it results in a significant increase in the lateral coverage width of a single emission. For example, in a typical abdominal convex array probe application, the single coverage width of focused emission might only be around 1.6 mm, while switching to diffused wave emission can extend this width to 2.4 mm or even wider, maintaining relatively uniform coverage across the entire detection depth.

[0104] This embodiment is specifically designed based on the physical mechanism of shear wave elastic imaging. The inversion calculation of shear wave velocity mainly relies on the phase difference or time of flight of displacement signals between adjacent spatial locations. This process is essentially a measurement of the wave propagation slope, rather than anatomical imaging of the fine structure of tissue. Therefore, as long as the lateral sampling density provided by the diffused wave still meets the basic requirements of the Nyquist sampling theorem for the shear wave wavelength, its slightly reduced lateral resolution will not have a substantial impact on the accuracy of velocity estimation. Conversely, due to the significantly increased lateral coverage width d of a single tracking transmission, the calculation logic based on the target transmission count determined in the aforementioned embodiment... The number of transmissions w required to cover a dynamic tracking window of the same size will be reduced proportionally. Assuming a constant pulse repetition frequency (PRF), the time consumed by a single scan block will decrease. This shortens the window, resulting in a linear increase in the equivalent tracking frame rate within the window. Taking thyroid nodule examination as an example, if the dynamic tracking window width is 9.23mm, 14 transmissions are required when using focused transmission, with a frame rate of approximately 1429Hz; while using the diffuse wave transmission in this embodiment, only 6 transmissions are required, and the frame rate can jump to 3333Hz, an increase of more than 130%, which is crucial for capturing high-speed propagating shear waves.

[0105] It is important to emphasize that the diffused wave emission in this embodiment is not equivalent to full-field plane wave imaging. Although the emitted sound field itself has diffusion characteristics, the system only performs beamforming and data processing within the spatial range corresponding to the current dynamic tracking window. Echo data outside the window is actively discarded or not processed. This "wide-area emission, local reception" strategy cleverly combines the advantages of two paradigms: it utilizes the wide single-pass coverage of diffused waves to reduce the number of transmissions, while inheriting the high signal-to-noise ratio and high frame rate advantages of dynamic window local focusing processing, avoiding the problem of drastic signal-to-noise ratio deterioration in deep tissues due to lack of focus in full-field plane wave imaging. It should be understood that the specific location of the virtual focus can be adaptively adjusted according to the probe curvature and target depth, for example, set within a range of 5mm to 50mm on the back of the probe, so as to obtain a relatively ideal coverage uniformity and signal-to-noise ratio balance at different depths. In addition, the emission of the push wave still maintains the traditional focusing mode to ensure that a sufficiently strong shear wave is excited in the target area. This embodiment only modifies the diffusion of the tracking wave used to detect displacement, thereby maximizing the tracking sampling rate while ensuring excitation efficiency.

[0106] In some of these embodiments, when a convex array ultrasonic probe or a phased array ultrasonic probe is used, the distance between the far boundary of the ROI region and the push focus, the size of the dynamic tracking window, and the position of the dynamic tracking window are defined in polar coordinates.

[0107] Specifically, unlike the rectangular field of view formed by linear array probes, convex array and phased array probes generate a fan-shaped scanning field of view, with their spatial sampling points physically distributed radially and azimuthally. Directly applying the aforementioned linear sliding logic based on Cartesian coordinates to such probes would cause a mismatch between the coverage width of the window at the edge of the fan and the actual wavefront propagation path, leading to geometric distortion in the shear wave velocity estimation. Therefore, this embodiment reconstructs the original one-dimensional lateral distance parameter into polar coordinate parameters: the distance D between the original ROI region's far boundary and the push focus is redefined as the radial distance difference along the sound beam propagation direction; the original dynamic tracking window size W no longer represents the straight-line width but corresponds to a range of azimuth angles; the original window center position x_c is converted to the center angle θ_c. This parameter definition conversion ensures that the dynamic tracking strategy can adapt to the natural geometric characteristics of the fan-shaped sound field, allowing the tracking window to uniformly cover the shear wavefront in the angular dimension.

[0108] The dynamic tracking window corresponds to an azimuth range, which is calculated based on the preset range of shear wave velocity and the far radial distance of the ROI region.

[0109] In polar coordinates, although shear wave propagation is primarily radial, its wavefront broadening in the transverse direction manifests as a change in angular span. To ensure that the dynamic tracking window can effectively cover the region between the fastest and slowest wavefronts, as in a linear array probe, the system needs to dynamically calculate the required azimuth span based on the current radial depth. For example, with the same physical window width requirement, as the detection depth increases, the corresponding azimuth span should decrease accordingly to maintain constant arc length coverage. This conversion process essentially transforms prior wave velocity information in physical space into control commands in the angular domain, enabling the dynamic window's angle to adaptively adjust with depth, thereby maintaining tight coverage of the shear wavefront at all depth levels within the fan-shaped field of view.

[0110] In order to achieve the above polar coordinate adaptation without changing the core scheduling algorithm, this embodiment defines an equivalent horizontal coordinate at the center radial depth of the ROI region, and maps the distance between the far boundary of the ROI region and the push focus, the size of the dynamic tracking window and the position of the dynamic tracking window to the equivalent horizontal coordinate.

[0111] Specifically, the system selects a reference depth r0 at the geometric center of the ROI as a reference plane, and linearly maps the arc length parameter in polar coordinates to a virtual Cartesian horizontal distance at this depth. Through this mapping, all the mathematical models and control logic used in the aforementioned embodiments to calculate the window size, sliding speed, and number of scan blocks can be directly reused without needing to derive a complex set of nonlinear control equations for the sector geometry. For example, the formula originally used to calculate the window width... While maintaining the same form, the W and D values ​​have been replaced with their corresponding values ​​in the equivalent transverse coordinate system. This design significantly reduces the complexity of the algorithm implementation and ensures the system's response speed and stability when switching between different probe types.

[0112] It should be understood that the aforementioned equivalent mapping based on central radial depth is essentially an engineering approximation. In a strictly geometric sense, the arc length and angle at different depths within a sector field of view are not linearly related, thus potentially introducing scale errors at the proximal and distal edges of the ROI. However, within the clinically common abdominal or cardiac scanning depth range (e.g., 60mm to 150mm), and when the sector angle is within a conventional range, this geometric distortion error caused by the central depth approximation is typically controlled to within 5%, far lower than the impact of anisotropy and noise on elasticity measurement results from biological tissue itself. Therefore, this approximation successfully achieves low-cost application of the core inventive concept to non-linear array probes while ensuring imaging accuracy. Of course, in special application scenarios with extreme accuracy requirements, alternative solutions such as multi-segment polyline approximation, depth-by-depth lookup table correction, or real-time trigonometric function calculation can be used to eliminate this approximation error, but these alternative solutions do not deviate from the core technical concept of this invention regarding "constructing a dynamic following mechanism in polar coordinates." Through the adaptation of this embodiment, the same ultrasound elastography system can seamlessly support multiple probes such as linear array, convex array and phased array, which significantly improves the clinical applicability and examination flexibility of the equipment.

[0113] This invention also provides an ultrasonic shear wave elastography system, including an ultrasonic probe, a transmitting module, a receiving module, a beamforming module, a dynamic tracking control module, a shear wave elastography estimation module, and a display and interaction module. The dynamic tracking control module controls the configuration and sliding of the dynamic tracking window, and controls the transmitting module to perform tracking scanning of the scan block and update the window position as described above. The shear wave elastography estimation module performs shear wave velocity inversion based on the tissue displacement data to obtain the shear wave velocity distribution and corresponding shear modulus distribution within the Region of Interest (ROI). The display and interaction module displays B-mode ultrasound images, the ROI selection interface, an elastic pseudo-color image, and quality prompts.

[0114] The transmitting module includes a push wave transmitting unit (generating high-intensity acoustic radiation force push pulses) and a tracking wave transmitting unit (generating short-duration, low-sound-pressure tracking pulses); the receiving module includes an analog front-end (AFE) and a high-speed data acquisition (ADC).

[0115] The beamforming module is also used to perform delay superposition (DAS) on the acquired radio frequency (RF) signals, supporting dynamic focusing and diffuse wave synthesis.

[0116] Furthermore, the dynamic tracking control module calculates the size W and center position x_c of the tracking window in real time and sends scanning sequence control commands to the transmitting module. The shear wave elasticity estimation module is also used to perform displacement estimation (e.g., phase difference method based on complex signal autocorrelation) and shear wave velocity inversion (based on cross-correlation time-of-flight fitting, etc.) on the scanned, timestamped IQ data, and outputs the shear wave velocity and corresponding shear modulus.

[0117] Compared with existing technologies, this invention can optimize scanning timing scheduling without changing the existing linear scanning focused ultrasound hardware architecture, relying on the physical propagation characteristics of shear waves being concentrated only in a local narrow band region of the ROI at any given time. Overall, it has the following beneficial technical effects: ① Without altering the existing linear scan focused emission B-mode ultrasound architecture, by utilizing the physical prior that shear waves occupy only a narrow region of the Region of Interest (ROI) at a given moment, the tracking sampling rate within the window is improved compared to traditional full ROI scanning; for example... Figure 9 As shown, under the respective clinical scanning parameters of each organ (ROI lateral D=20mm, using ceil coverage criterion): Liver (3.5MHz convex array probe, scanning depth 100mm, PRF 7.5kHz, v∈[1.0, 3.0]m / s, δ=0): Traditional method 577Hz → Basic scheme of this invention 833Hz (+44%) → This invention + Strategy 3 1250Hz (+117%). Thyroid (12MHz linear array probe, scanning depth 30mm, PRF 20kHz, v∈[1.5, 7.0]m / s, δ=0): Traditional method 1176Hz → Basic scheme of this invention 1429Hz (+21%) → This invention + Strategy 1 (pre-calibration) + Strategy 3 (diffusion wave emission) 3333Hz (+183%). Kidney (3.5MHz convex array probe, scanning depth 80mm, PRF 9kHz, v∈[1.5, 4.0]m / s, δ=0): Traditional method 692Hz → Basic scheme of this invention 1125Hz (+63%) → This invention + Strategy 3 1500Hz (+117%). The above data were obtained by strictly discretizing the coverage criteria w=ceil(W / d) and N=ceil(D / d). It should be noted that the tracking rate refers to the "equivalent tracking block rate for the current shear wavefront region within the window", rather than the overall imaging frame rate of the entire ROI at each time step; the elasticity parameter map of the complete ROI is obtained by inverting and stitching together the displacement data of multiple time slices.

[0118] ②As the scanning schedule changes from "static full ROI coverage" to "dynamic shear wave following", it helps to improve the phenomenon of shear wave "loss" in organs with large ROI and high v_max. ③ Strategy 1 (Pre-calibration) provides a tighter window estimate between different lesions in the same organ, and the window can be further narrowed if the estimate is reliable; ④ Strategy 2 (baseline quality assessment) provides objective quality assessment indicators for the acquisition results, which helps operators identify low-quality acquisition caused by disturbances such as breathing, heartbeat, and hand tremors; ⑤ Strategy 3 (Diffusion Wave Emission) can balance the window coverage width and estimation accuracy to a certain extent, provided that the displacement estimation SNR threshold is met. ⑥ The implementation of this invention is located in the transmission-reception timing and digital processing software layer, and the engineering modification cost is relatively low.

[0119] The elastic imaging method of the present invention is illustrated below with several specific embodiments: Example 1 involves SWE elastography for diffuse liver lesions (such as liver fibrosis, fatty liver, and cirrhosis). Considering that the effective imaging depth of liver parenchyma usually needs to reach 6–15 cm during transabdominal ultrasound scanning, this example uses a low-frequency convex array probe to balance penetration depth and image quality. Specific parameters are as follows: (1) Probe: 128-element convex array probe (curvilinear), center frequency 3.5MHz, equivalent adjacent emission center spacing d=1.6mm (focused emission) or d=2.4mm (diffusion emission) at the center depth of ROI; (2) Scanning depth: 100mm (typical transabdominal liver scan depth, which can be adjusted between 80 and 150mm depending on the patient's body size); (3) Due to the bidirectional propagation of sound waves, PRF_max = c0 / (2·depth) = 1540 / (2·0.10) ≈ 7700Hz, but PRF = 7500Hz is actually taken. (4) Lateral distance of ROI: D=20mm, δ=0mm; (5) Preset wave velocity range for organs: [v_min, v_max] = [1.0, 3.0] m / s.

[0120] Calculated from the formula: W = 20·(1 1 / 3)+0=13.33mm, V_slide=2.0m / s.

[0121] Traditional line scanning tracking: N=ceil(20 / 1.6)=13 lines, f_trad=7500 / 13≈577Hz; Basic scheme of the invention: w = ceil(13.33 / 1.6) = 9 transmissions, T_block = 9 / 7500 = 1.2ms, f_new = 7500 / 9 ≈ 833Hz (approximately 44% improvement over traditional methods); In this invention (diffused wave d=2.4mm): w'=ceil(13.33 / 2.4)=6, f_new'=7500 / 6=1250Hz (an improvement of about 117% compared to the traditional method).

[0122] The total acquisition time is estimated using the formula: T_acq≥D / v_min+T_margin=20 / 1.0+2=22ms; the required number of blocks: M≥ceil(22 / 1.2)=19 blocks. After displacement estimation and shear wave velocity inversion, the displacement sequence within the entire ROI outputs the shear wave velocity distribution cs(x,z) and the corresponding shear modulus distribution G(x,z).

[0123] Note: For convex array probe geometry, D and d are estimated as equivalent linear parameters at the center depth of the ROI; strictly speaking, they should be defined in (θ, r) polar coordinates as described above, while the form of the W formula remains unchanged.

[0124] Example 2: Elastography of Breast Tumors Example 2 involves SWE elastography of small superficial breast masses. Specific parameters are: (1) Probe: 128-element high-frequency linear array probe, center frequency 7.5MHz, pitch 0.3mm, focused emission d=4·pitch=1.2mm, diffuse emission d=6·pitch=1.8mm; (2) Scan depth: 40mm (typical breast SWE scan depth, which can be adjusted between 20-60mm depending on the location of the lesion), corresponding to an upper limit of PRF of about 19kHz, and actually PRF=18000Hz; (3) ROI lateral distance: D=20mm, δ=2mm (due to irregular scattering at the edge of the tumor, a large protection redundancy is set); (4) Preset wave velocity range for organs: [v_min, v_max] = [1.0, 5.0] m / s.

[0125] From the formula, we can obtain: W = 20·(1 1 / 5)+2=18.0mm, V_slide=3.0m / s.

[0126] Traditional line scan tracking: N=ceil(20 / 1.2)=17, f_trad=18000 / 17≈1059Hz; Basic scheme of the invention: w=ceil(18.0 / 1.2)=15, T_block=15 / 18000≈0.83ms, f_new=18000 / 15=1200Hz(+13%); This invention combines a diffused wave emission method: (d=1.8mm):w'=ceil(18.0 / 1.8)=10, f_new'=18000 / 10=1800Hz(+70%).

[0127] The total acquisition time T_acq≥20 / 1.0+2=22ms, and the required number of blocks M≥ceil(22 / 0.83)=27 blocks.

[0128] Because breast SWE is easily affected by operator disturbances (hand tremors, breathing), this embodiment also uses a quality assessment method based on baseline data: before the main acquisition, a baseline data of about 6ms is acquired with the same follow-up sequence but without emitting push waves to obtain σ_noise; after the main acquisition, the quality index is calculated according to Q=σ_signal / σ_noise. When Q<3, the display module prompts low confidence and suggests adjusting the section or probe position and retaining the original data for post-processing.

[0129] Example 3: Elastography of Thyroid Nodules Example 3 involves SWE elastography of thyroid nodules. Because thyroid tissue has a high v_max (up to 7 m / s), the shear wave "loss" problem is prominent in traditional linear scanning methods. Specific parameters are: (1) Probe: 128-element high-frequency linear array probe, center frequency 12MHz, pitch 0.3mm (the same pitch as in Example 2 is used for comparison), focused emission d=1.2mm, diffuse emission d=1.8mm; (2) Scan depth: 30mm (the thyroid gland is located superficially, and the typical scan depth is 20–40mm), PRF=20000Hz; (3)ROI:D=20mm,δ=0mm; (4) Preset wave velocity range for organs: [v_min, v_max] = [1.5, 7.0] m / s; (5) Enable calibration steps and spread wave emission mode.

[0130] Basic scheme: W=20·(1 1.5 / 7)≈15.71mm, V_slide=4.25m / s, N=ceil(20 / 1.2)=17, w=ceil(15.71 / 1.2)=14; f_trad=20000 / 17≈1176Hz, f_basic=20000 / 14≈1429Hz(+21%).

[0131] Enable pre-scan calibration: Perform a low-density push—tracking pre-acquisition, estimating based on the time difference of arrival between adjacent tracking lines. ≈3.0m / s, narrowing the range to [2.1, 3.9]m / s with ε=0.3, substituting into the aforementioned window size calculation formula, we calculate W'=20·(1 2.1 / 3.9)≈9.23mm, w'=ceil(9.23 / 1.2)=8, f'=20000 / 8=2500Hz (relative to the uncalibrated basic scheme +75%).

[0132] Superimposed diffused wave emission mode (diffused wave, d=1.8mm): w''=ceil(9.23 / 1.8)=6, f''=20000 / 6≈3333Hz (approximately 183% improvement over traditional methods).

[0133] The total acquisition time T_acq≥20 / 1.5+2≈15.3ms, the basic scheme T_block=14 / 20000=0.7ms, and the required number of blocks M≥ceil(15.3 / 0.7)=22 blocks.

[0134] Example 4: Renal elastography Example 4 involves imaging of renal corticomedullary elastography parameters. Specific parameters are: (1) Probe: 128-element convex array probe, center frequency 3.5MHz, equivalent spacing between adjacent transmission centers d=1.6mm (focusing) or d=2.4mm (diffusion); (2) Scan depth: 80mm, corresponding to a PRF upper limit of approximately 9.6kHz, but the actual PRF is set to 9000Hz; (3) Lateral distance of ROI: D=20mm, δ=0mm; (4) Preset wave velocity range for organs: [v_min, v_max] = [1.5, 4.0] m / s.

[0135] From the aforementioned formula, we can obtain: W = 20·(1 1.5 / 4)=12.5mm, V_slide=2.75m / s.

[0136] Traditional line scan tracking: N=ceil(20 / 1.6)=13, f_trad=9000 / 13≈692Hz; Basic scheme of the invention: w=ceil(12.5 / 1.6)=8, T_block=8 / 9000≈0.89ms, f_new=9000 / 8=1125Hz(+63%); This invention combines diffused wave (d=2.4mm): w'=ceil(12.5 / 2.4)=6, f_new'=9000 / 6=1500Hz(+117%).

[0137] The total acquisition time T_acq≥20 / 1.5+2≈15.3ms, and the required number of blocks M≥ceil(15.3 / 0.89)=18 blocks.

[0138] In this specification, the same or similar parts between the various embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, for the product embodiments described later, since they correspond to the methods, the descriptions are relatively simple, and the relevant parts can be referred to the descriptions in the system embodiments.

[0139] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for ultrasonic shear wave elastography based on a dynamic tracking window, characterized in that, include: Select a region of interest (ROI) on the B-mode ultrasound image corresponding to the biological tissue to be tested; Configure a sliding dynamic tracking window within the ROI area; A push wave is emitted within the biological tissue to be tested to excite the shear wave at the push focus. During the propagation process, the instantaneous distribution area of ​​the shear wave within the ROI region can be tracked and covered by the dynamic tracking window. Within the dynamic tracking window, a tracking scan of the scan block is performed, tracking echo signals are acquired, and the timestamps of each tracking transmit-receive signal in each tracking scan are recorded. The time-stamped tissue displacement data is calculated based on the tracking echo signal and the preset reference signal; Based on the timestamp, the position of the dynamic tracking window is updated at a preset sliding speed, causing it to slide towards the far end of the ROI along the predetermined propagation direction of the shear wave. Repeatedly scan the dynamic tracking window after the position is updated, and perform subsequent operations until the required number of scan blocks are collected. Shear wave velocity inversion is performed on the time-stamped tissue displacement data to obtain the shear wave velocity distribution and the corresponding shear modulus distribution within the ROI region.

2. The method according to claim 1, characterized in that, The methods for calculating the required number of scans for a block include: Obtain the preset range of shear wave velocity of the biological tissue under test and the distance from the far boundary of the ROI region to the push focus; The window size and total acquisition time of the dynamic tracking window are calculated based on the distance and the preset range of wave speed, and the preset sliding speed of the window is calculated based on the preset range of wave speed. Based on the window size and the lateral coverage width that can be estimated by displacement in a single tracking transmit-receive, the number of tracking transmits required for each scan block is determined, and then the scan duration of a single scan block is determined based on the number of tracking transmit-receives and the pulse repetition frequency; The required number of scans for a single scan block is calculated based on the total acquisition time and the scan time of a single scan block.

3. The method according to claim 2, characterized in that, The window size W of the dynamic tracking window is calculated by the following formula: W = D·(1 - v_min / v_max) + δ, where D is the distance from the push focus to the far boundary of the ROI, v_min and v_max are the lower limit and upper limit of the preset range of the wave speed, and δ is the protection redundancy; when the calculated W ≥ D, the system reverts to scanning the entire ROI area.

4. The method according to claim 2, characterized in that, Configuring a sliding dynamic tracking window within the ROI region includes: Initialize the center position of the dynamic tracking window to a position that aligns the starting boundary of the dynamic tracking window with the push focus; and / or Before performing a tracking scan of a scan block within the dynamic tracking window, at least one frame of reference signal is acquired for the ROI region or a predetermined tracking region as a baseline reference for subsequent tissue displacement data calculation. The reference signal includes radio frequency (RF) data or in-phase quadrature (IQ) data.

5. The method according to claim 2, characterized in that, The step of updating the position of the dynamic tracking window according to a preset sliding speed includes: The candidate center position of the dynamic tracking window is calculated based on the preset sliding speed and the timestamp; When the candidate center position exceeds the far boundary of the ROI region, the center position of the dynamic tracking window is locked at the far boundary of the ROI region so that the dynamic tracking window remains within the ROI region.

6. The method according to claim 5, characterized in that, During the repeated scanning of the dynamic tracking window at the updated position, If the amplitude of the shear wave decays below a preset amplitude threshold before the required number of scans is achieved, the area not fully covered is marked with low confidence, or all scan blocks within the dynamic tracking window are rescanned.

7. The method according to claim 2, characterized in that, Shear wave velocity inversion of the time-stamped tissue displacement data includes: The tracking echo signal obtained from each tracking scan is cross-correlated with the reference signal or the phase difference is calculated to obtain the tissue displacement data at each spatial location; Based on the tissue displacement data and the corresponding timestamp, shear wave velocity inversion is performed.

8. The method according to any one of claims 2-7, characterized in that, Before performing a tracking scan of the scan block within the dynamic tracking window, the method further includes: Perform a low-density or short-duration push-track pre-acquisition, wherein the push-track includes a push pulse and multiple tracking transmissions; Based on the arrival time difference or cross-correlation between adjacent tracking lines in the pre-collection, the coarse shear wave velocity of the biological tissue to be tested is estimated. Based on the rough shear wave velocity and the preset error tolerance, the preset range of the wave velocity is narrowed; If the pre-collected signal-to-noise ratio does not reach the preset threshold, the preset range of shear wave velocity is retained.

9. The method according to any one of claims 1-7, characterized in that, After completing the required number of scans of the scan block, the method further includes: Without exciting the shear wave, background data is collected according to the same scanning sequence as the tracking scan; Calculate the background vibration intensity based on the aforementioned background data; The signal vibration intensity is calculated based on the tissue displacement data obtained from the tracking scan. Calculate the quality evaluation index based on the signal vibration intensity and the background vibration intensity; When the quality evaluation index is lower than the preset confidence threshold, a low confidence prompt message is output.

10. The method according to claim 1, characterized in that, Performing tracking transmission and reception within the dynamic tracking window includes: The tracking transmission is performed using a diffused wave emission method with the virtual focus located on the back of the ultrasound probe, in order to increase the lateral coverage width of a single tracking transmission; Within the dynamic tracking window, beamforming and displacement estimation are performed on the received diffuse echo signal.

11. An ultrasonic shear wave elastography system, characterized in that, include: The system includes an ultrasonic probe, a transmitting module, a receiving module, a beamforming module, a dynamic tracking control module, a shear wave elasticity estimation module, and a display and interaction module. The dynamic tracking control module is used to control the configuration and sliding of the dynamic tracking window, and to control the launching module to perform tracking scanning of the scanning block and update the window position according to the method described in claim 1; The shear wave elastic estimation module is used to perform shear wave velocity inversion based on the tissue displacement data to obtain the shear wave velocity distribution and the corresponding shear modulus distribution within the ROI region. The display and interaction module is used to display B-mode ultrasound images, ROI selection interfaces, flexible pseudo-color images, and quality prompts.

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