Systems and methods for beamformed sound velocity selection

Abstract

Methods and systems for beamforming of received ultrasound signals to generate ultrasound images with increased resolution are provided. In one example, a method for an ultrasound system including a plurality of ultrasound transducers, each coupled to a respective receive channel, is provided, the method including time delaying a set of ultrasound receive channel signals to form a plurality of sets of time delayed ultrasound receive channel signals, each set of time delayed ultrasound receive channel signals time delayed based on a different beamforming sound speed; calculating, for each receive channel and for each set of time delayed ultrasound receive channel signals, a beamforming quality metric; and generating an ultrasound image from ultrasound receive channel signals selected from the plurality of sets of time delayed ultrasound receive channel signals based on each beamforming quality metric.

Description

Technical Field

[0001] Embodiments of the subject matter disclosed herein relate to ultrasound imaging, and more particularly, to improving image quality for ultrasound imaging. Background Art

[0002] Medical ultrasound is an imaging modality that uses ultrasound waves to detect and image the internal structures of a patient's body. For example, an ultrasound probe, comprised of multiple transducer elements, transmits ultrasound pulses, which are reflected or retransmitted back, refracted, or absorbed by structures within the body. The probe then receives the reflected echoes, which are processed into an image. Ultrasound images of internal structures can be saved for later analysis by clinicians to aid diagnosis and / or displayed on a display device in real time or near real time. Summary of the Invention

[0003] In one embodiment, a method is provided for an ultrasound system including a plurality of ultrasound transducers, each coupled to a corresponding receive channel, the method comprising: time-delaying a set of ultrasound receive channel signals to form a plurality of time-delayed ultrasound receive channel signal sets, each time-delayed ultrasound receive channel signal set being time-delayed based on a different beamforming sound velocity; calculating a beamforming quality metric for each receive channel and for each time-delayed ultrasound receive channel signal set; and generating an ultrasound image based on an ultrasound receive channel signal selected from the plurality of time-delayed ultrasound receive channel signal sets based on each beamforming quality metric.

[0004] The above advantages and other advantages and features of the present disclosure will be apparent from the following detailed description, either alone or in conjunction with the accompanying drawings. It should be understood that the above summary is provided to introduce a selection of concepts further described in the detailed description in a simplified form. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is solely defined by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that address any disadvantages noted above or in any part of this disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0005] Various aspects of the present disclosure may be better understood by reading the following detailed description and referring to the accompanying drawings, in which:

[0006] Figure 1 A block diagram of an exemplary embodiment of an ultrasound system is shown;

[0007] Figure 2 It is shown that the formation Figure 1 a block diagram of a receiver as part of a system;

[0008] Figure 3 is a graph illustrating a hyperbolic characteristic of a time delay of a received radio frequency signal;

[0009] Figures 4A to 4C shows ultrasound waves traveling through different media at an assumed speed of sound compared to the actual speed of sound and aligned channel data after applying a time delay;

[0010] Figure 5 is a flow chart illustrating an example method for generating an ultrasound image from received channel signals selected based on a beamforming quality metric calculated for each channel and each of a plurality of different time delays during an ultrasound scan; and

[0011] Figure 6 and Figure 7 is a diagram schematically illustrating a beamforming quality metric calculated from a received channel signal based on multiple sound speeds and multiple deep time delays. DETAILED DESCRIPTION

[0012] Medical ultrasound imaging typically involves placing an ultrasound probe, comprising one or more transducer elements, over an imaging subject (such as a patient) at the location of a target anatomical feature (e.g., the abdomen, chest, etc.). Images are acquired by the ultrasound probe and displayed on a display device in real time or near real time (e.g., the image is displayed as soon as it is generated and without intentional delay). During the image acquisition process by the ultrasound probe, transmit beamforming and receive beamforming may be used. Time delays may be implemented during transmit and receive beamforming to modify the beamforming angle and focus range when acquiring ultrasound images. The beamforming time delay may be based on an assumed velocity of ultrasound waves traveling through the imaging medium (e.g., tissue). This assumed velocity may typically be a default velocity set by the system. Different imaging media (e.g., adipose tissue, liver tissue) exhibit different velocities of sound, meaning that the velocity of ultrasound waves traveling through a first medium may be different from the velocity of ultrasound waves traveling through a second medium. Therefore, a predetermined or default assumed velocity set by the system may result in a loss of image resolution depending on the imaging medium covered or changes in the imaging medium during the ultrasound scan. Conventional ultrasound systems may allow ultrasound operators to manually adjust the assumed sound velocity used to calculate beamforming time delays. However, various factors may hinder the correct selection of the sound velocity (e.g., user inexperience, time constraints), which may result in ultrasound images exhibiting lower resolution. Furthermore, a single assumed sound velocity may not be optimal when the sound velocity varies within the medium. Furthermore, ultrasound system manufacturers have found that most operators do not like to manually adjust the ultrasound system to optimize ultrasound image quality.

[0013] Therefore, according to the embodiments disclosed herein, an optimal receive beamforming time delay can be automatically applied to each receive channel coupled to a corresponding transducer element in an ultrasound probe for each depth and at each transmit event, so that the generated ultrasound image can exhibit an improvement in image resolution. Ultrasound data received by the transducer of the ultrasound probe (referred to herein as channel data) before being processed into an image can be time delayed multiple times based on different beamforming sound speeds and analyzed to identify which beamforming sound speed and corresponding time delay to apply to each receive channel to generate an image. In order to identify the time delay applied to each receive channel, a beamforming quality metric can be determined for each receive channel and each different time delay, wherein the beamforming quality metric can be based on a coherence factor that reflects the level of similarity between a subset of receive channel signals centered on the receive channel being calculated. In this way, ultrasound images generated from automatically selected ultrasound imaging parameters can exhibit higher image resolution without the need for operator intervention.

[0014] For example, a set of original undelayed channel signals may be collected and stored in a memory. Assuming that the set of possible speed of sound values ​​includes 20 speed of sound values, 20 time delayed versions of the original undelayed channel signal are created, where each version is delayed by one of the 20 speed of sound (SOS) values. In the following explanation, each sample of the delayed channel data signal will alternatively be referred to as a pixel. Then, for each transmission, in each delayed channel signal, the following steps may be performed: for each depth, a coherence metric is calculated for each channel. The coherence metric is calculated using channels adjacent to the channel being calculated. For each depth, and for each channel, a pixel (e.g., a time delayed channel signal sample) is selected from the set of SOS delayed channel signals with the highest coherence score. In some examples, the coherence metric may be calculated for depth blocks simultaneously rather than for each depth to increase speed. In addition, a weighted average of the channel signals of the pixel / time delay can be calculated instead of taking the pixel with the highest coherence metric from the different SOS delayed channel signals (for example, for each SOS delayed channel signal set for the channel and depth, the corresponding pixel is selected, and the weighted average of all possible pixels is taken instead of the pixel with the highest coherence metric). Further, for each emission and each depth, adjacent channel islands with a coherence metric above a certain threshold in each SOS data set can be identified instead of selecting a single pixel from the SOS delayed channel signal. Then, if a channel belongs to multiple islands, then in the final combination of the islands with different sound speed data sets, the island with the larger size will be the island that includes the channel. This will implicitly select the largest coherence aperture from each delayed data set. As an alternative, the quality metric of each pixel can be proportional to its coherence with its adjacent channels and the size of the coherence aperture to which it belongs in the SOS data set. Then, the pixel with the highest quality score from the SOS data set is selected.

[0015] Figure 1 An exemplary ultrasound system is shown in FIG. , which includes an ultrasound probe, a display device, and an imaging processing system. An ultrasound image can be acquired via the ultrasound probe and displayed on the display device. Figure 2 Shown in Figure 1 A receiver of a system having a plurality of receive channels for receive beamforming. Figure 3 A graph illustrating the hyperbolic characteristic of the delay of the received radio frequency signal is shown in . Figure 4A An exemplary schematic diagram of an ultrasound wave reflected from a point and traveling through different media during ultrasound imaging is shown in FIG. Figure 4B A first alignment of channel data based on a first sound velocity is shown in . Figure 4CThe second alignment of the channel data based on the second sound velocity is shown in FIG. The optimal beamforming sound velocity can be determined for each channel and applied to the time delayed channel signal to obtain the optimal beamforming sound velocity according to the time delay. Figure 5 Ultrasound images are generated using this method. Figure 6 and Figure 7 Graphs illustrating a beamforming quality metric for each receive channel calculated at a plurality of different sound velocities and for each of a plurality of depths of receive wave velocity are shown in FIG.

[0016] See also Figure 1 , shows a schematic diagram of an ultrasound imaging system 100 according to an embodiment of the present disclosure. The ultrasound imaging system 100 includes a transmit beamformer 101 and a transmitter 102, which drives elements (e.g., transducer elements) 104 within a transducer array (referred to herein as a probe 106) to transmit pulsed ultrasound signals (referred to herein as transmit pulses) into a body (not shown). According to one embodiment, the probe 106 can be a one-dimensional transducer array probe. However, in some embodiments, the probe 106 can be a two-dimensional matrix transducer array probe. As further explained below, the transducer elements 104 can be made of piezoelectric material. When a voltage is applied to the piezoelectric crystal, the piezoelectric crystal physically expands and contracts, thereby emitting ultrasound waves. In this way, the transducer elements 104 can convert the electronic transmit signals into acoustic transmit beams.

[0017] After the elements 104 of the probe 106 transmit pulsed ultrasound signals into the body (of the patient), the pulsed ultrasound signals reflect from structures inside the body (such as blood cells or muscle tissue) to produce echoes that return to the elements 104. The echoes are converted into electrical signals, or ultrasound data, by the elements 104, and the electrical signals are received by the receiver 108. The electrical signals representing the received echoes pass through a receive beamformer 110, which outputs ultrasound data.

[0018] The echo signals generated by the transmission operation are reflected from structures located at successive distances along the transmitted ultrasonic beam. The echo signals are sensed individually by each transducer element, and a sample of the echo signal amplitude at a particular point in time represents the amount of reflection occurring at a particular distance (also known as depth). However, due to differences in the propagation paths between the reflection point P and each element, these echo signals are not detected simultaneously. The receiver 108 amplifies the individual echo signals, assigns a calculated reception time delay to each amplified signal, and sums the time-delayed amplified signals to provide a single echo signal that generally indicates the total ultrasonic energy reflected from the point P located at the distance R along the ultrasonic beam oriented at the angle θ.

[0019] During reception of the echo, the time delay of each receive channel is continuously varied to provide dynamic focusing of the received beam at the distance R from which the echo signal is assumed to originate based on an assumed speed of sound of the medium.

[0020] As directed by the processor 116, the receiver 108 provides a time delay during the scan so that the steering of the receiver 108 tracks the direction θ of the beam steered by the transmitter, and samples the echo signals at successive distances R to provide the appropriate time delay and phase shift to dynamically focus along the beam at a point P. Thus, each transmission of the ultrasound pulse waveform results in the acquisition of a series of data points representing the amount of sound reflected from a series of corresponding points P located along the ultrasound beam.

[0021] According to some embodiments, the probe 106 may include electronic circuitry to perform all or part of transmit beamforming and / or receive beamforming. For example, all or part of the transmit beamformer 101, transmitter 102, receiver 108, and receive beamformer 110 may be located within the probe 106. In this disclosure, the terms "scan" or "scanning" may also be used to refer to the acquisition of data through the process of transmitting and receiving ultrasound signals. In this disclosure, the term "data" may be used to refer to one or more data sets acquired by the ultrasound imaging system. The user interface 115 may be used to control the operation of the ultrasound imaging system 100, including input for controlling patient data (e.g., patient medical history), for changing scan or display parameters, for initiating probe repolarization sequences, etc. The user interface 115 may include one or more of the following: a rotary element, a mouse, a keyboard, a trackball, hard keys linked to specific actions, soft keys that can be configured to control different functions, and a graphical user interface displayed on the display device 118.

[0022] The ultrasound imaging system 100 also includes a processor 116 for controlling the transmit beamformer 101, the transmitter 102, the receiver 108, and the receive beamformer 110. The processor 116 is in electronic communication (e.g., communicatively connected) with the probe 106. For the purposes of this disclosure, the term "electronic communication" may be defined to include both wired and wireless communication. The processor 116 may control the probe 106 to acquire data based on instructions stored in the processor's memory and / or the memory 120. The processor 116 controls which of the elements 104 are active and the shape of the beam emitted from the probe 106. The processor 116 is also in electronic communication with a display device 118 and may process data (e.g., ultrasound data) into images for display on the display device 118. The processor 116 may include a central processing unit (CPU) according to one embodiment. According to other embodiments, the processor 116 may include other electronic components capable of performing processing functions, such as a digital signal processor, a field programmable gate array (FPGA), or a graphics board. According to other embodiments, the processor 116 may include multiple electronic components capable of performing processing functions. For example, the processor 116 may include two or more electronic components selected from a list of electronic components including: a central processing unit, a digital signal processor, a field programmable gate array, and a graphics board. According to another embodiment, the processor 116 may also include a composite demodulator (not shown) that demodulates the real RF data and generates composite data. In another embodiment, demodulation may be performed earlier in the processing chain. The processor 116 is adapted to perform one or more processing operations based on multiple selectable ultrasound modalities on the data. In one example, data may be processed in real time during a scanning session as echo signals are received by the receiver 108 and transmitted to the processor 116. For the purposes of this disclosure, the term "real time" is defined to include processes performed without any intentional delay. For example, embodiments may acquire images at a real-time rate of 7 to 20 frames per second. The ultrasound imaging system 100 is capable of acquiring 2D data for one or more planes at significantly faster rates. However, it should be understood that the real-time frame rate may depend on the length of time it takes to acquire each frame of data for display. Therefore, when acquiring relatively large amounts of data, the real-time frame rate may be slower. Thus, some embodiments may have real-time frame rates significantly faster than 20 frames per second, while other embodiments may have real-time frame rates slower than 7 frames per second. Data may be temporarily stored in a buffer (not shown) during a scanning session and processed in a less-than-real-time manner in real-time or offline operations. Some embodiments of the present invention may include multiple processors (not shown) to handle the processing tasks handled by processor 116 according to the exemplary embodiments described above.For example, a first processor may be used to demodulate and extract the RF signal before displaying the image, while a second processor may be used to further process the data (e.g., by augmenting the data as further described herein). It will be appreciated that other embodiments may utilize different processor arrangements.

[0023] The ultrasound imaging system 100 can continuously acquire data at a frame rate of, for example, 10 Hz to 30 Hz (e.g., 10 to 30 frames per second). An image generated based on the data can be refreshed on the display device 118 at a similar frame rate. Other embodiments can acquire and display data at different rates. For example, depending on the size of the frame and the intended application, some embodiments can acquire data at a frame rate of less than 10 Hz or greater than 30 Hz. A memory 120 is included for storing frames of processed acquired data. In an exemplary embodiment, the memory 120 has sufficient capacity to store at least a few seconds of ultrasound data frames. The data frames are stored in a manner that facilitates retrieval based on their acquisition order or time. The memory 120 may include any known data storage medium.

[0024] In various embodiments of the present invention, the processor 116 may process data using various modality-related modules (e.g., B-mode, color Doppler, M-mode, color M-mode, spectral Doppler, elastography, TVI, strain, strain rate, etc.) to generate 2D or 3D data. For example, one or more modules may generate B-mode, color Doppler, M-mode, color M-mode, spectral Doppler, elastography, TVI, strain, strain rate, and combinations thereof. As an example, one or more modules may process color Doppler data, which may include traditional color flow Doppler, power Doppler, HD flow, etc. Image lines and / or frames are stored in memory and may include timing information indicating when the image lines and / or frames were stored in memory. These modules may include, for example, a scan conversion module for performing scan conversion operations to convert acquired images from beam space coordinates to display space coordinates. A video processor module may be provided that reads acquired images from memory and displays the images in real time while a procedure (e.g., ultrasound imaging) is performed on a patient. The video processor module may include a separate image memory, and the ultrasound image may be written to the image memory for reading and display by the display device 118 .

[0025] In various embodiments of the present disclosure, one or more components of the ultrasound imaging system 100 may be included in a portable handheld ultrasound imaging device. For example, the display device 118 and the user interface 115 may be integrated into the external surface of the handheld ultrasound imaging device, which may also include a processor 116 and a memory 120. The probe 106 may include a handheld probe that electronically communicates with the handheld ultrasound imaging device to collect raw ultrasound data. The transmit beamformer 101, the transmitter 102, the receiver 108, and the receive beamformer 110 may be included in the same or different parts of the ultrasound imaging system 100. For example, the transmit beamformer 101, the transmitter 102, the receiver 108, and the receive beamformer 110 may be included in a handheld ultrasound imaging device, a probe, or a combination thereof.

[0026] After performing a two-dimensional ultrasound scan, a data block containing the scan lines and their samples is generated. After applying the back-end filter, a process called scan conversion is performed to transform the two-dimensional data block into a displayable bitmap image with additional scanning information (such as depth, the angle of each scan line, etc.). During scan conversion, interpolation techniques are applied to fill in the missing holes (i.e., pixels) in the resulting image. These missing pixels occur because each element of the two-dimensional block should typically cover many pixels in the resulting image. For example, in current ultrasound imaging systems, bicubic interpolation is applied, which utilizes adjacent elements of the two-dimensional block. Therefore, if the two-dimensional block is relatively small compared to the size of the bitmap image, the scan-converted image will include areas of poor or low resolution, especially for areas with greater depth.

[0027] Now turn Figure 2 , Figure 2 An embodiment 200 of a receiver 214 is shown that includes three sections, including a time gain control section 226, a receive beamforming section 228, and an intermediate processor 230. In one example, the receiver 214 may be Figure 1 1. A non-limiting example of a receiver 108 of FIG. A time gain control (TGC) section 226 includes a respective amplifier 232 for each of the receive channels 234, and a time gain control circuit 236 is provided for controlling the gain of the amplifiers 232. The input of each amplifier 232 is coupled to a respective one of the transducer elements 104 to amplify the echo signal received thereby. The amount of amplification provided by the amplifiers 232 is controlled by a control line 238 driven by the TGC circuit 236, which is set by manual operation of a potentiometer 240.

[0028] The receive beamforming section 228 of the receiver 214 includes a plurality of receive channels 234, each of which receives an analog echo signal from a corresponding amplifier 232 at a corresponding input 242. The analog signal is digitized and produced as a stream of signed digitized samples. These samples are each delayed within the receive channel so that, when summed with samples from the other receive channels, the amplitude of the summed signal for the selected channel is a measure of the strength of the echo signal reflected from a point P located at a distance R on the steered beam θ.

[0029] In order to properly sum the electrical signals generated by the echoes impinging on each transducer element 104, a time delay is introduced into each individual channel 234 of the receiver 214. The time delay added to each receive channel can be based on an assumed speed of sound through the imaged tissue. In one example, the imaged tissue may contain more fat than muscle in certain areas, which can affect the time delay that may be applied when receive beamforming in that area because the propagation speed of ultrasound waves through fat is different from that of ultrasound waves through muscle. In addition to the delayed signed samples, each receive channel 234 also provides the amplitude or absolute value of the delayed signed samples. The delayed signed samples are provided to the coherent summation bus 244, while the amplitude of the delayed signed samples is provided to the incoherent summation bus 246. The coherent summation bus 244 uses a pipeline summer 248 to sum the delayed signed samples from any number of adjacent receive channels to produce a coherent sum (e.g., Figure 2 The non-coherent sum bus 246 uses pipeline summers 250 to sum the magnitudes of delayed signed samples from any number of adjacent receive channels to produce a non-coherent sum (e.g., Figure 2 incoherent and B).

[0030] The receiver intermediate processor section 230 receives the coherently summed beam samples from the pipeline summer 248 and the incoherently summed beam samples from the pipeline summer 250. The intermediate processor section 230 includes a detection processor 252.

[0031] The detection processor 252 calculates and applies a coherence factor in accordance with the present disclosure. The coherence factor may be calculated for each data sample / channel signal and may be defined (at least in one example) as the ratio of the following two quantities: the amplitude of the sum of the received signals; and the sum of the amplitudes of the received signals. In the detection processor 252, the ratio is calculated by calculating the absolute value of the coherent sum from the pipeline summer 248 and then calculating the ratio of the absolute value of the coherent sum from the pipeline summer 248 to the incoherent sum from the pipeline summer 250. If the incoherent sum is zero, the ratio may be set to zero. In one example, the ratio may be calculated by dividing the absolute value of the coherent sum by the sum of the incoherent and a small positive value, which avoids dividing by zero when the incoherent sum is zero. In one example, the detection processor 252 is Figure 1 In another example, the detection processor 252 is connected to the Figure 1 The processor 116 is separate from but operatively coupled to the processor.

[0032] In the case of a radio frequency (RF) beamformer, the signal from each channel is a real, signed quantity, and the coherent sum is the sum of the signals. The incoherent sum is the sum of the absolute values ​​of each signal (e.g., a non-negative sum). In the case of a baseband beamformer, the real signal from each channel is demodulated to form a complex number, so that the coherent sum is also a complex number. The absolute value of the coherent sum is a non-negative real number. The incoherent sum is the sum of the absolute values ​​of the channel signals; it is also a non-negative real number. In both cases, the ratio of the absolute value of the coherent sum to the absolute value of the incoherent sum is a non-negative real number.

[0033] During an ultrasound scan, the transmitter drives the probe so that the generated ultrasonic energy can be directed into a beam. To achieve this, the transmitter applies a time delay to the pulse waveform, which is applied to successive transducer elements in the probe. By adjusting the time delay in a conventional manner, the ultrasonic energy beam can be directed at an angle away from the axis parallel to the probe, thereby focusing the beam within a fixed range. By continuously varying the time delay, ultrasound scanning can be performed because the angle at which the beam can be directed gradually changes.

[0034] A receive ultrasound beamformer can be used as part of an ultrasound imaging system. The ultrasound imaging system can use transmit events from the transmit beamformer and receive events from the receive beamformer to generate a line of ultrasound image. The transmit beamformer can focus on a single location in the scan area, while the receive beamformer can focus on the same location. During receive beamforming, a time delay can be associated with the propagation angle and velocity of the ultrasound wave relative to the angle and velocity at which the ultrasound wave is received by the receive beamformer.

[0035] Due to the varying sound propagation velocities of anatomical media within an anatomical region, ultrasound waves may propagate at different speeds during an ultrasound scan. Depending on the anatomical region the probe may be transmitting into, a default propagation velocity may be used for the ultrasound scan, which can be prone to errors and result in lower image resolution. Because ultrasound waves propagate at different speeds in all media, errors in using the default propagation velocity during ultrasound scanning may occur in scanned regions that include muscle, fat, and bone. When the receive beamformer operates at a default propagation velocity that differs from the actual propagation velocity, the received data may be miscalculated, resulting in inaccurate imaging during ultrasound image generation. In one example, an ultrasound scan may occur over an area that includes muscle and fat, which have different associated sound propagation velocities, and the resulting ultrasound image from the ultrasound scan may include areas of low resolution due to the suboptimal beamformed sound velocity for that area. Automatically selecting the optimal beamformed sound velocity for each channel can result in optimized metrics for ultrasound image generation.

[0036] Now turn Figure 3 , which shows an example of a graph 300 depicting a hyperbolic feature in a radio frequency signal. The hyperbolic feature represents the relative time differences for each RF signal to propagate along each channel for three echoes reflected from three different points / scatterers during an ultrasound scan. When detected by an ultrasound transducer, the echoes can be converted into RF signals to be received by a receive channel during receive beamforming.

[0037] A first axis 304 represents receive channels in an ultrasound imaging system, wherein each vertical line extending from the first axis 304 represents a single channel. A second axis 306 represents time, such that time values ​​closer to the first axis 304 may be smaller than time values ​​further away from the first axis 304.

[0038] When the speed of sound of the scatterers and / or medium through which the echoes travel is a nominal speed of sound, such as 1540 m / s, a dotted hyperbola is generated, such as hyperbola 312. When the speed of sound of the scatterers and / or medium is greater than the nominal speed of sound, an outer solid hyperbola is generated, such as hyperbola 308. When the speed of sound of the scatterers and / or medium is less than the nominal speed of sound, an inner solid hyperbola is generated, such as hyperbola 310.

[0039] like Figure 3As will be appreciated, the shape of the hyperbola varies based on the speed of sound. For example, hyperbola 308 is flatter than hyperbola 310 and hyperbola 312. Furthermore, different media may produce hyperbolas of different shapes. Therefore, when a time delay is added to each RF signal before summing the RF signals during image generation, the time delay is selected based on the speed of sound of the medium. Typically, ultrasound images can be generated by applying an assumed speed of sound (e.g., 1540 m / s). However, if the speed of sound of the medium differs from the assumed speed of sound, the added time delay may not match the shape of the hyperbola, leading to image quality issues, as explained above.

[0040] Now turn Figure 4A , which shows an exemplary schematic diagram 400 of portions of an ultrasound beam 401 returning from a point 402 to one or more transducers of an ultrasound probe. The portions of the ultrasound beam 401 may propagate through various anatomical media while traveling from the point 402 back to the transducers.

[0041] As previously explained, optimal ultrasound image generation may include accurately applying time delays based on an assumed speed of sound for each portion of the ultrasound beam. A first curve 408 may represent an assumed arrival time of the ultrasound beam at the transducer for each portion of the ultrasound beam based on an assumed speed of sound at which each portion of the ultrasound beam may travel through the anatomical scan region. However, as Figure 4A It is understood that not all portions of an ultrasound beam may travel through the same medium and therefore, in practice, one or more portions of the beam may arrive at the ultrasound transducer at a different time than expected based on the assumed speed of sound.

[0042] Thus, as shown, a first portion 404 of the ultrasound beam may propagate from point 402 back to the transducer, accurately matching the arrival time predicted by the first curve 408. A second portion 405 of the ultrasound beam may propagate from point 402 back to the transducer, but because the second portion 405 of the ultrasound beam travels through medium 406, the second portion 405 of the ultrasound beam may not have an arrival time that accurately matches the first curve 408 due to propagation through a different medium than the first portion 404 of the ultrasound beam. The portion of the ultrasound beam that travels through medium 406 may have an arrival time represented by a second curve 410.

[0043] Applying time delays to portions of the ultrasound beam based on an assumed speed of sound represented by the first curve 408 may result in inaccurate time delays being applied to portions of the ultrasound beam propagating through the medium 406. Applying inaccurate time delays may result in lower image quality (e.g., image resolution) when generating an ultrasound image based on one assumed speed of sound.

[0044] Figure 4BAn example diagram of a first alignment 420 of channel signals based on applying time delays derived from a first speed of sound is shown. When time delays are applied based on an assumed speed of sound that is accurate for all portions of an ultrasound beam propagating to and from a transducer, all channel signals may be aligned along a vertical axis 428. In one example, the first alignment 420 may represent the alignment of channel signals when a first set of time delays is applied to a channel signal received from an ultrasound transducer based on the first assumed speed of sound. Figure 4A The ultrasonic beam is aligned with the ultrasonic channel signal when the channel signal is obtained.

[0045] The first segment 422 of the first alignment 420 may include channel signals from channels coupled to ultrasonic transducers that receive the portion of the ultrasonic beam that traveled through the medium 406. The first segment 422 may represent a receive channel in which a time delay applied based on the first assumed speed of sound may not be accurate compared to the actual speed of sound for the portion of the ultrasonic beam during propagation, and thus the channel signals in the first segment 422 are not aligned along the vertical axis 428. The second segment 424 defined by the first bounding box 426 may include channel signals from channels in which a time delay applied based on the first assumed speed of sound may be accurate compared to the actual speed of sound for the portion of the ultrasonic beam during propagation (e.g., transducers that receive the portion of the ultrasonic beam that did not travel through the medium 406). As shown Figure 4B As a visual indication, channel signals parallel to the vertical axis 428 may exhibit high levels of coherence relative to each other (with respect to Figure 2 Detailed explanation), and channel data that is not parallel to the vertical axis 428 can exhibit lower coherence relative to channel data in the second segment 424.

[0046] Figure 4C FIG. 4 is a diagram illustrating an example of a second alignment 440 of a channel signal based on an applied time delay derived from a second speed of sound. In one example, the second alignment 440 may represent a second set of time delays applied to a channel signal received from an ultrasound transducer based on a second assumed speed of sound. Figure 4A The ultrasonic beam is aligned with the ultrasonic channel signal when the channel signal is obtained.

[0047] A third segment 442 of the second alignment 440, defined by the second bounding box 446, may include channel signals from channels coupled to ultrasonic transducers that receive the portion of the ultrasonic beam that traveled through the medium 406. The third segment 442 may represent ultrasonic channels in which the time delay applied based on the second assumed speed of sound may be accurate compared to the actual speed of sound of the portion of the ultrasonic beam during propagation, and thus the channel signals in the third segment 442 are aligned along the vertical axis 448. The fourth segment 444 may include channel signals from channels in which the time delay applied based on the second assumed speed of sound may be inaccurate compared to the actual speed of sound of the portion of the ultrasonic beam during propagation (e.g., transducers that receive the portion of the ultrasonic beam that did not travel through the medium 406). As Figure 4C As a visual indication, channel signals parallel to the vertical axis 448 may exhibit high levels of coherence relative to each other (with respect to Figure 2 Detailed explanation), and channel signals that are not parallel to the vertical axis 448 may exhibit lower coherence relative to channel signals in the third segment 442.

[0048] Therefore, if Figure 4A As shown, ultrasound echoes can propagate at different velocities even from a single point source, so applying a single beamforming echo to time-delay each channel signal can result in lower image quality. Figures 4B to 4C represents two time delays of channel signals from the same channel signal set using two different beamforming velocities. Figure 4B and Figure 4C As shown, using the same beamforming speed of sound to time delay the received channel signals on all channels may result in some channel signals being misaligned, even if other channel signals are more accurately aligned. According to the embodiments disclosed herein, a channel-based approach that independently selects the optimal beamforming speed of sound, and therefore the time delay, for each received channel may result in the generation of ultrasound images having higher image metrics (e.g., image resolution) than using channel signals to generate ultrasound images when only one beamforming speed of sound is selected to time delay all channel signals. In one example, if the channel signals from Figure 4B The first sound velocity is applied to the receiving channel in the second section 424, and the Figure 4C If the second sound velocity is applied to the receive channels in the third segment 442, all receive channel data can be aligned. As will be explained in more detail below, an optimal beamforming sound velocity can be determined for each receive channel. Embodiments for selecting an optimal beamforming sound velocity or a target beamforming sound velocity on a channel-by-channel basis are disclosed herein.

[0049] Figure 5A flow chart illustrating an example method 500 for generating an ultrasound image using a time delay selected independently for each receive channel based on a beamforming quality metric is shown. Figures 1 to 2 The method 500 is described using the systems and components of FIG116 , but it should be understood that other systems and components may be used to implement the method 500 without departing from the scope of the present disclosure. The method 500 may be executed according to instructions stored in a non-transitory memory of a computing device, such as the processor 116 . In some examples, the method 500 may be executed each time the ultrasound probe acquires ultrasound data and forms an image from the ultrasound data, such that the frequency of executing the method 500 matches the frame rate of the ultrasound imaging. In other examples, the method 500 may be executed at a predetermined frequency less than the frame rate (e.g., once per second) during ultrasound imaging and / or in response to a determination that the ultrasound probe has moved or that the anatomical structure being imaged has changed.

[0050] At 501, method 500 includes activating a plurality of ultrasound transducers of an ultrasound probe to transmit an ultrasound beam toward a subject being imaged. The transmitted ultrasound beam may be focused at a particular focal depth and beam angle. At 502, method 500 includes transmitting an ultrasound beam from each transducer in the ultrasound probe (such as receive channel 234, as described with respect to FIG. Figure 2 As described above, Figures 1 to 2 As explained, the channel signal comprises echoes detected by the ultrasound transducer elements, which are received after transmitting the beam.

[0051] At 504, method 500 includes applying a corresponding time delay to each channel signal based on a first sound speed to form a first delayed channel signal for each channel. The first sound speed can be a first sound speed in a set of possible sound speeds. The set of possible sound speeds can be predetermined or set by a user. In one example, the set of possible sound speeds can include 5, 10, 20, or more sound speeds that are within a reasonable sound speed range based on the imaging task (e.g., imaging human anatomy can result in a range of 1400 m / s to 1600 m / s). As previously explained, the reflected echo is from the desired source point to the transducer element. In the case of a constant sound speed in the medium, the arrival time of the echo (e.g., the receive beam) at the transducer element can be a function of the distance from the source point to the transducer element and the sound speed of the medium through which the ultrasound wave travels, for example, distance(source, transducer_element) / medium_sound_speed. When the speed of sound in the medium is not constant, the time of arrival at the transducer element is the integral of the incremental propagation times along the assumed propagation path, where the incremental propagation time is the incremental distance along the path divided by the speed of sound at each incremental distance. Therefore, beamforming is typically performed using a single assumed speed of sound for the medium to cancel the assumed time of arrival differences at the transducer elements, and then the time-delayed signals are summed to form an image (as explained below). If the assumed beamforming speed of sound is different from the true speed of sound in the medium, the beamforming will be suboptimal and may result in less than optimal image resolution and contrast. Therefore, as explained herein, beamforming may be performed on the same channel signals with different speeds of sound, based on a beamforming quality metric calculated for each receive channel at each different speed of sound, to identify a target or optimal speed of sound for each channel used to form an image.

[0052] At 506, method 500 includes calculating a beamforming quality metric for each receive channel from the first delayed channel signal. The beamforming quality metric may be calculated for each receive channel at each depth of the receive beam / imaged tissue. In other examples, the depths may be combined into multiple depth ranges, and the beamforming quality metric may be calculated for each depth range. For example, a beamforming quality metric may be calculated for a first depth, and the beamforming quality metric may be applied to one or more depths above and / or below the first depth (e.g., 2 to 3 depths above the first depth and 2 to 3 depths below the first depth), which may reduce the number of beamforming quality metrics calculated and, therefore, may increase the speed of selecting time delayed channel signals (e.g., as explained below). The depth ranges may be overlapping (as explained above) or non-overlapping. Each beamforming quality metric may include a coherence metric (as indicated at 507) representing a level of similarity between a subset of the delayed channel signals, which is related to image resolution and contrast, but is not required to form an image. In one example, the coherence metric may be the coherence metric described above with respect to Figure 2 However, other methods for determining the coherence measure are possible without departing from the scope of the present disclosure, such as the ratio of the squared amplitudes of the channel signals, the similarity of the phases of the complex channel signals, or the similarity of the signs of the real channel signals.

[0053] For the purpose of calculating the coherence metric, the received channels can be divided into channel subsets by applying a moving window across the received channels at each depth or within a depth range, wherein the window is continuously located above (e.g., centered) each received channel to calculate the coherence metric for the received channel at that depth based on the received channel and one or more adjacent received channel delayed channel signals at that depth or within the depth range. For example, at a first depth (or depth range), a first coherence metric for the first received channel can be calculated from a time-delayed channel signal received by a first received channel at the first depth and a time-delayed channel signal received by a second received channel at the first depth (adjacent to the first received channel). A second coherence metric for the second received channel can be calculated from a time-delayed channel signal received by the first received channel, a time-delayed channel signal received by the second received channel, and a time-delayed channel signal received by a third received channel (adjacent to the second received channel), all at the first depth. The size of the moving window can be set to calculate each coherence metric from three adjacent / contiguous receive channels (excluding the first and last channels), or another suitable number of adjacent / contiguous receive channels (e.g., 2, 5, 7, etc.). As previously explained, the coherence metric can be a normalized value ranging from 0 to 1, inclusive, where 1 means that the amplitude of the beams from those receive channels at that depth represents a high confidence that scattering is from the intended focus direction, and values ​​close to 0 can indicate that stray scattering and / or off-axis scattering may be present in the receive channel signal.

[0054] In some examples, each beamforming quality metric may include a coherence metric and a length metric, as indicated at 509. As explained above, a coherence metric may be calculated for each receive channel at each depth. To calculate the length metric, the coherence metrics calculated for all receive channels at a given depth may be filtered to identify coherence metrics above a threshold (e.g., above 0.5, or the top 10% to 50% of the coherence metrics). Adjacent receive channels with a coherence metric above the threshold may be identified as islands of high coherence, and each receive channel in the island of high coherence may be assigned a length metric value that is proportional to the number of receive channels in the island of high coherence. For example, each receive channel in a first island of high coherence having 10 adjacent receive channels may be assigned a length metric of 0.1, while each receive channel in a second island of high coherence having 20 adjacent receive channels may be assigned a length metric of 0.2. In one example, a beamforming quality metric may be assigned to each receive channel in an island of high coherence, the beamforming quality metric comprising a coherence metric of the receive channel and a length metric of each receive channel in the island of high coherence, such that each receive channel in the island of high coherence has an independently calculated beamforming quality metric. In another example, the coherence metrics and length metrics of all receive channels in the island of high coherence may be averaged, and the average value may be assigned as the beamforming quality metric of each receive channel in the island of high coherence, such that each receive channel in the island of high coherence has the same beamforming quality metric. If a receive channel is not included in any island of high coherence, a beamforming quality metric based solely on the coherence metric of the receive channel may be assigned to the receive channel.

[0055] At 508, method 500 includes repeating 502 through 506 for each different sound speed in the set of possible sound speeds. For example, if the set of possible sound speeds includes 20 sound speeds, the original (e.g., undelayed) set of received channel signals may be time delayed for each additional sound speed, resulting in 20 sets of time-delayed received channel signals, one set for each different sound speed. For each set of time-delayed received channel signals, a beamforming quality metric is calculated for each received channel at each depth (or depth range). Thus, a beamforming quality metric may be calculated for each received channel at each depth and for each sound speed in the set of possible sound speeds.

[0056] At 510, method 500 includes selecting a time-delayed receive channel signal for each receive channel and at each depth or within the depth range based on the beamforming quality metrics calculated for the receive channels at the depths / depth ranges. In a first example, selecting the time-delayed receive channel signal for each receive channel and at each depth may include selecting the time-delayed receive channel signal with the highest beamforming quality metric, as indicated at 511. For example, when generating 20 different sets of time-delayed receive channel signals, 20 different beamforming quality metrics may be calculated for a given receive channel at a given depth, each corresponding to a different time-delayed receive channel signal (wherein each different time-delayed receive channel signal is generated based on the same, undelayed receive channel signal received via the receive channel and is time-delayed based on 20 different sound speeds). The highest beamforming quality metric of those 20 beamforming quality metrics may be identified, and the time-delayed channel signal that produces the highest beamforming quality metric may be selected as the selected time-delayed channel signal for that receive channel and depth. Thus, for each receive channel and each depth, the time-delayed channel signal that produces the highest beamforming quality metric (relative to the other time-delayed channel signals for that receive channel and depth) may be selected.

[0057] In another example, selecting a time-delayed receive channel signal for each receive channel and at each depth may include calculating a weighted average of all time-delayed channel signals for the receive channel and the depth based on the beamforming quality metrics of the time-delayed channel signals, and setting the selected time-delayed channel signal as the weighted average signal. Calculating the weighted average may include applying a weight to each time-delayed channel signal that is proportional to the beamforming quality metric calculated for the time-delayed channel signal. For example, as explained above, for a given receive channel and depth, 20 time-delayed receive channel signals may be formed, each of which is generated based on the same, undelayed receive channel signal received via the receive channel and time-delayed based on 20 different sound speeds. A beamforming quality metric may be calculated for each of the 20 time-delayed receive channel signals. The 20 time-delayed receive channel signals may be averaged using a weight applied to each time-delayed receive channel signal that is proportional (e.g., linearly or nonlinearly) to the beamforming quality metric calculated for the time-delayed receive channel signal.

[0058] At 512, the process described above is repeated for each additional transmit ultrasound beam (e.g., obtaining a set of undelayed receive channel signals at 502; time-delaying each receive channel signal multiple times at 504 and 508, each time delaying using a different beamforming speed of sound; calculating a beamforming quality metric for each channel and depth at 506 and 508; and selecting a time-delayed channel signal for each channel and depth at 510). Thus, for each receive beam (received after the transmit event), a time-delayed channel signal is selected for each depth and each receive channel based on the calculated beamforming quality metric.

[0059] At 514, method 500 includes generating an ultrasound image based on the selected time-delayed channel signals. For example, for each depth of each receive beam, the selected time-delayed receive channel signals are summed to form a beam sum signal, the logarithm of the absolute value of the beam sum signal is determined, scan conversion is performed to square pixels, and the pixels are scaled to 8-bit grayscale values ​​to form an image. Method 500 then returns.

[0060] Figure 6 An exemplary graph 600 illustrating multiple time-delayed channel signals plotted as a function of receive channel, depth, and beamformed sound velocity is shown. Graph 600 depicts the time-delayed receive channel signals obtained for a single transmit event (e.g., one receive beam), as described above with respect to Figure 5 Explained.

[0061] Graph 600 depicts receive channels along the horizontal axis (x-axis), depth along the vertical axis (y-axis), and the speed of sound (SOS) applied to time-delay the receive signals along the transverse axis (z-axis). The number of receive channels increases from the first channel to the last channel (channel N). Depth increases from the top of the vertical axis downward toward the horizontal axis, such that the minimum depth (e.g., the first depth) is closest to the ultrasound probe, while the maximum depth (depth N) is farthest from the ultrasound probe. The SOS may include multiple SOSs selected from a possible SOS range, and its value increases from the first SOS (e.g., 1400 m / s) to the last SOS (e.g., 1600 m / s). The time-delayed receive channel signals are illustrated as points in graph 600. For clarity, only the time-delayed channel signals for the first depth are shown.

[0062] In the example shown, an ultrasound scan is performed such that echoes are received from a subject after an ultrasound signal is transmitted via an ultrasound probe. The echoes are received by the ultrasound transducers of the ultrasound probe, and the output of each transducer is sent along a channel for processing as described above. The channel signals are then processed sequentially with different time delays based on a plurality of different sound speeds (e.g., 10 or 20 speeds between 1400 m / s and 1600 m / s). As described above with respect to Figure 5 As explained above, a beamforming quality metric is calculated for each time-delayed channel signal at each depth. Figure 2 The beamforming quality metric is calculated using a coherence measure of the received signal calculated in the intermediate processor 230 (such as the coherence ratio) as the ratio of the amplitude of the coherently summed received signal to the amplitude of the incoherently summed received signal.

[0063] To form a scan line of an image, the selected time-delayed channel signals at each depth may be summed to form a beam sum for each depth. The beam sum is then converted to grayscale pixels as described above. Based on the beamforming quality metric (calculated for the receive channel and depth), a time-delayed channel signal is selected from all the time-delayed channel signals (for that receive channel and depth). As described above with respect to Figure 5 As explained, one example for selecting the time-delayed channel signal includes selecting the time-delayed channel signal with the highest beamforming quality metric. Figure 6 As shown, for channel 2, 10 different beamforming quality metrics are calculated: one beamforming quality metric for each time-delayed channel signal, where each time-delayed channel signal is time-delayed based on a different sound speed. Since the beamforming quality metric of the time-delayed channel signal 602 is the highest beamforming quality metric of all beamforming quality metrics calculated for channel 2 at the first depth, the time-delayed channel signal 602 (at the first depth) is selected. Figure 6 (Highlighted by a box in the figure for visual clarity). Therefore, for the first depth, the channel signal received through channel 2 and time-delayed by the second SOS is selected as the time-delayed channel signal 603 of channel 2 for the first depth.

[0064] Another example for selecting the time-delayed channel signal includes calculating a weighted average of all the time-delayed channel signals for the received channel and depth. For example, Figure 6This example illustrates selecting a time-delayed channel signal for channel 4. All time-delayed channel signals for the first depth of channel 4 are indicated by box 604. These time-delayed channel signals for the first depth of channel 4 are averaged, and a corresponding weight is applied to each time-delayed channel based on the beamforming quality metric calculated for that time-delayed channel signal. For example, if the beamforming quality metric calculated for the time-delayed channel signal time-delayed by the first SOS is higher than the beamforming quality metric calculated for the time-delayed channel signal time-delayed by the last SOS, the higher weight is applied to the time-delayed channel signal time-delayed by the first SOS. Therefore, for the first depth, the channel signals received by channel 4 time-delayed by all SOSs are averaged using a weighted averaging scheme that applies weights proportional to the corresponding beamforming quality metrics, and the averaged signal is selected as the time-delayed channel signal 605 for channel 4 for the first depth. Once a time-delayed channel signal is selected for each received channel, the multiple time-delayed channel signals for the first depth 606 are summed and further processed to form pixels of the final image. A similar process is performed at each depth, forming the scan lines of the final image. This entire process is repeated for each transmit / receive beam to form the final image.

[0065] Figure 7 Graph 700 is shown, which is similar to graph 600 and thus illustrates multiple time-delayed channel signals plotted as a function of receive channel, depth, and beamforming sound velocity for a single transmit event (e.g., one receive beam). The time-delayed receive channel signals are illustrated as points in graph 700. For clarity, only the time-delayed channel signals for the first depth are shown.

[0066] Figure 7 A plurality of high coherence islands are schematically illustrated, wherein, for the depth and SOS (applied to time delay the channel signals used to calculate the coherence metric), each receive channel has a coherence metric above a threshold. For example, for a first SOS (1400 m / s) and a first depth, there is a first high coherence island 702, a second high coherence island 704, and a third high coherence island 706. A first length metric may be assigned to each receive channel in the first high coherence island 702 (in addition to the coherence metric calculated for each receive channel), a second length metric may be assigned to each receive channel in the second high coherence island 704, and a third length metric may be assigned to each receive channel in the third high coherence island 706, wherein the first length metric is higher than the second and third length metrics, and the third length metric is higher than the second length metric.

[0067] Therefore, as explained above, a beamforming quality metric may be calculated for each receive channel, for each time-delayed channel signal in a plurality of time-delayed channel signals, at each depth (or depth range) in a plurality of depths (or depth ranges), and at each transmit event. For a given depth, receive channel, and transmit event, a time-delayed channel signal may be selected from a subset of time-delayed channel signals, wherein each time-delayed channel signal in the subset of time-delayed channel signals is delayed from the original channel signal using a different beamforming velocity, and wherein the original channel signal is received via the given receive channel. The time-delayed channel signal may be selected based on its beamforming quality metric relative to other beamforming quality metrics calculated for each time-delayed channel signal in the subset of time-delayed channel signals. For example, the selected time-delayed channel signal may have the highest beamforming quality metric among all time-delayed channel signals in the subset of time-delayed channel signals. In another example, the selected time-delayed channel signal may be a weighted sum (e.g., a weighted average) of some or all time-delayed channel signals in the subset of time-delayed channel signals, wherein each time-delayed channel signal is weighted based on its respective beamforming quality metric. In some examples, the beamforming quality metric may be a coherence metric that indicates a level of similarity between a time-delayed channel signal under consideration (received via a given receive channel) and one or more adjacent time-delayed channel signals, wherein the one or more adjacent time-delayed channel signals are time-delayed based on the same beamforming speed of sound as the time-delayed channel signal under consideration, at the same depth, and at the same transmission time, and are received via receive channels adjacent to the given receive channel (e.g., 1 to 5 receive channels on either side of the given receive channel). In some examples, the beamforming quality metric may include a coherence metric and a length metric, wherein the length metric indicates the number of adjacent receive channels around the given receive channel that also have a coherence metric above a threshold. In this way, the beamforming quality metric (whether based solely on the coherence metric or both the coherence metric and the length metric) may be used to select the best time-delayed channel signal (whether based on the maximum beamforming quality metric for a subset of time-delayed channel signals or based on a weighted average of the time-delayed channel signals of the subset of time-delayed channel signals).

[0068] A technical effect of automatically selecting a time-delayed channel signal for each receive channel at each depth using the calculated beamforming quality metric in ultrasound image generation is that ultrasound image quality may be improved without operator intervention.

[0069] The present disclosure also provides support for a method for an ultrasound system comprising a plurality of ultrasound transducers, each coupled to a respective receive channel, the method comprising: time-delaying a set of ultrasound receive channel signals to form a plurality of time-delayed ultrasound receive channel signal sets, each time-delayed ultrasound receive channel signal set being time-delayed based on a different beamforming sound speed; calculating a beamforming quality metric for each receive channel and for each time-delayed ultrasound receive channel signal set; and generating an ultrasound image based on ultrasound receive channel signals selected from the plurality of time-delayed ultrasound receive channel signal sets based on each beamforming quality metric. In a first example of the method, each respective different beamforming sound speed is selected from a set of possible beamforming sound speeds, wherein time-delaying the set of ultrasound receive channel signals to form the plurality of time-delayed ultrasound receive channel signal sets comprises: acquiring the set of ultrasound receive channel signals and storing the set in a memory, and time-delaying the set of ultrasound receive channel signals a plurality of times, each time delaying using a respective different beamforming sound speed, such that a time-delayed ultrasound receive channel signal set is generated for each beamforming sound speed in the set of possible beamforming sound speeds. In a second example of the method, which optionally includes the first example, each beamforming quality metric includes a corresponding coherence metric reflecting a level of coherence between corresponding subsets of ultrasound receive channel signals. In a third example of the method, which optionally includes one or both of the first and second examples, calculating a corresponding coherence metric for each receive channel and for each time-delayed ultrasound receive channel signal set includes: calculating a first coherence metric for each receive channel based on a corresponding subset of the first time-delayed ultrasound receive channel signal set for a first time-delayed ultrasound receive channel signal set time-delayed based on a first beamforming sound speed, each corresponding subset being received via the receive channel and one or more adjacent receive channels; and repeating the coherence metric calculation for each receive channel for each remaining time-delayed ultrasound receive channel signal set, such that the coherence metric is calculated for each receive channel at each different beamforming sound speed. In a fourth example of the method, which optionally includes one or more or each of the first to third examples, each beamforming quality metric further includes a corresponding length metric that reflects the number of additional receive channels adjacent to the receive channel that have a coherence metric above a threshold for the receive channel.In a fifth example, which optionally includes one or more of the first through fourth examples, or each of the methods, generating an ultrasound image based on the selected ultrasound receive channel signals includes: calculating, for each receive channel, a weighted sum of each time-delayed ultrasound receive channel signal received through the receive channel, wherein each time-delayed ultrasound receive channel signal is weighted based on a corresponding beamforming quality metric calculated for the receive channel and the time-delayed ultrasound receive channel signal, and generating an ultrasound image based on each weighted sum. In a sixth example, which optionally includes one or more of the first through fifth examples, or each of the methods, generating an ultrasound image based on the selected ultrasound receive channel signals includes: selecting, for each receive channel, a time-delayed ultrasound receive channel signal received through the receive channel having the highest beamforming quality metric, and generating an ultrasound image based on the selected time-delayed ultrasound receive channel signal. In a seventh example, which optionally includes one or more of the first through sixth examples, or each of the methods, calculating, for each beamforming sound velocity, a beamforming quality metric for each receive channel at each of a plurality of depths. In an eighth example of the method, which optionally includes one or more or each of the first to seventh examples, for each beamformed sound velocity, a beamforming quality metric is calculated for each receive channel at each depth range of a plurality of overlapping or non-overlapping depth ranges. In a ninth example of the method, which optionally includes one or more or each of the first to eighth examples, the ultrasound receive channel signal set is a first ultrasound receive channel signal set obtained at a transmit event, and further includes repeating the time delay, beamforming quality metric calculation, and ultrasound receive channel signal selection for each additional ultrasound receive channel signal set obtained at each additional transmit event.

[0070] The present disclosure also provides support for a system comprising: a plurality of ultrasonic transducers configured to transmit and receive ultrasonic signals; a memory storing instructions; and a processor configured to execute the instructions to: acquire a set of ultrasonic receive channel signals via the plurality of ultrasonic transducers; calculate a corresponding set of beamforming quality metrics for each of a plurality of time-delayed ultrasonic receive channel signal sets, wherein each time-delayed ultrasonic receive channel signal set is time-delayed from the set of ultrasonic receive channel signals based on a different beamforming sound velocity; and generate an ultrasonic image based on a selected set of the plurality of time-delayed ultrasonic receive channel signals based on each corresponding set of beamforming quality metrics. In a first example of the system, the set of ultrasonic receive channel signals is received via a set of receive channels, each receive channel coupled to an ultrasonic transducer of the plurality of ultrasonic transducers, and wherein each beamforming quality metric comprises a measure of similarity between the selected time-delayed ultrasonic receive channel signals. In a second example of the system, optionally including the first example, each beamforming quality metric comprises a corresponding coherence metric for each receive channel, each coherence metric comprising a sum of absolute values ​​of summed time-delayed channel signals for a corresponding receive channel subset to absolute values ​​of time-delayed channel signals for the corresponding receive channel subset, the corresponding receive channel subset comprising the receive channel and one or more adjacent receive channels. In a third example of the system, optionally including one or both of the first and second examples, generating an ultrasound image based on the selected time-delayed ultrasound receive channel signals comprises: calculating, for each receive channel, a weighted sum of each time-delayed ultrasound receive channel signal received through the receive channel, weighting each time-delayed ultrasound receive channel signal based on the corresponding beamforming quality metric calculated for the receive channel and the time-delayed ultrasound receive channel signal, and generating an ultrasound image based on each weighted sum. In a fourth example of the system, which optionally includes one or more of the first to third examples, or each of the examples, generating an ultrasound image based on the selected time-delayed ultrasound receive channel signals includes: selecting, for each receive channel, a time-delayed ultrasound receive channel signal received via a receive channel having a highest beamforming quality metric, and generating the ultrasound image based on the selected time-delayed ultrasound receive channel signal. In a fifth example of the system, which optionally includes one or more of the first to fourth examples, or each of the examples, calculating a corresponding set of beamforming quality metrics at each of a plurality of depths for each set of time-delayed ultrasound receive channel signals.

[0071] The present disclosure also provides support for a method comprising: generating an ultrasound image based on a selected set of time-delayed received channel signals, the method comprising: independently selecting, for each time-delayed received channel signal in the selected set, a time-delayed received channel signal from a plurality of possible time-delayed received channel signals based on a set of beamforming quality metrics calculated for each time-delayed received channel signal in the selected set. In a first example of the method, the plurality of possible time-delayed received channel signals are generated by acquiring an original set of received channel signals and storing them in a memory, and then time-delaying the original set of received channel signals a plurality of times, each time delaying the original set of received channel signals using a correspondingly different beamforming speed, such that a set of time-delayed received channel signals is generated for each beamforming speed in the set of possible beamforming speeds. In a second example of the method, which optionally includes the first example, each received channel signal in the original set of received channel signals is received via a separate receive channel, wherein each beamforming quality metric in the set of beamforming quality metrics is calculated for the corresponding receive channel by calculating a coherence metric over a moving window of the time-delayed received channel signals, the moving window being centered on the receive channel. In a third example of the method, which optionally includes one or both of the first and second examples, independently selecting the time-delayed receive channel signal from a plurality of possible time-delayed receive channel signals based on a set of beamforming quality metrics includes: for a given receive channel, selecting the time-delayed receive channel signal having the highest beamforming quality metric among all time-delayed receive channel signals, all of which are received through the receive channel for a given depth and transmit event.

[0072] When introducing the elements of various embodiments of the present disclosure, the words "one", "a kind of" and "the" are intended to mean that there are one or more elements in these elements. The terms "first", "second" etc. do not represent any order, amount or importance, but are used to distinguish one element from another. The terms "comprise", "comprising" and "having" are intended to be inclusive and mean that additional elements may also exist in addition to the elements listed. As used herein, the terms "connected to", "coupled to" etc., an object (e.g., a material, element, structure, member, etc.) can be connected to or coupled to another object, regardless of whether the one object is directly connected or coupled to another object, or whether there are one or more intervening objects between the one object and another object. In addition, it should be understood that reference to "one embodiment" or "embodiment" of the present disclosure is not intended to be interpreted as excluding the existence of additional embodiments that also include the cited features.

[0073] In addition to any modifications previously indicated, those skilled in the art may devise numerous other variations and alternative arrangements without departing from the spirit and scope of the present description, and the appended claims are intended to cover such modifications and arrangements. Thus, although the above has been described with particularity and detail in connection with what are presently considered to be the most practical and preferred aspects, it will be apparent to those skilled in the art that many modifications, including but not limited to form, function, mode of operation, and use, may be made without departing from the principles and concepts set forth herein. Likewise, as used herein, the examples and embodiments are intended to be illustrative in all respects only and should not be construed as limiting in any way.

Claims

1. A method for use in an ultrasound system comprising a plurality of ultrasound transducers, each ultrasound transducer coupled to a respective receive channel, the method comprising: Time-delaying the ultrasound receiving channel signal set to form a plurality of time-delayed ultrasound receiving channel signal sets, each time-delayed ultrasound receiving channel signal set being time-delayed based on a different beamforming sound velocity; calculating a beamforming quality metric for each receive channel and for each time-delayed set of ultrasound receive channel signals; as well as generating an ultrasound image according to ultrasound reception channel signals selected from the plurality of time-delayed ultrasound reception channel signal sets based on each beamforming quality metric; Wherein, each beamforming quality metric includes a corresponding coherence metric reflecting the coherence level between corresponding subsets of ultrasound receive channel signals; calculating the corresponding coherence metric for each receive channel and for each time-delayed ultrasound receive channel signal set includes: for a first time-delayed ultrasound receive channel signal set time-delayed based on a first beamforming sound speed, calculating the first coherence metric for each receive channel based on a corresponding subset of the first time-delayed ultrasound receive channel signals, receiving each corresponding subset through the receive channel and one or more adjacent receive channels; and for each remaining time-delayed ultrasound receive channel signal set, repeating the coherence metric calculation for each receive channel, so that the coherence metric is calculated for each receive channel at each different beamforming sound speed.

2. The method according to claim 1, wherein Each corresponding different beamforming sound speed is selected from a set of possible beamforming sound speeds, wherein time delaying the ultrasound receive channel signal set to form the multiple time-delayed ultrasound receive channel signal sets includes: acquiring the ultrasound receive channel signal set and storing the set in a memory, and time delaying the ultrasound receive channel signal set multiple times, each time delay using a corresponding different beamforming sound speed, so that a time-delayed ultrasound receive channel signal set is generated for each beamforming sound speed in the set of possible beamforming sound speeds.

3. The method according to claim 1, wherein Each beamforming quality metric further includes a corresponding length metric reflecting a number of additional receive channels adjacent to the receive channel that have a coherence metric for the receive channel above a threshold.

4. The method according to claim 1, wherein Generating an ultrasound image according to the selected ultrasound receiving channel signal includes: calculating, for each receive channel, a weighted sum of each time-delayed ultrasound receive channel signal received through the receive channel, wherein each time-delayed ultrasound receive channel signal is weighted based on a corresponding beamforming quality metric calculated for the receive channel and the time-delayed ultrasound receive channel signal; and The ultrasound image is generated according to each weighted sum.

5. The method according to claim 1, wherein Generating an ultrasound image according to the selected ultrasound receiving channel signal includes: selecting, for each receive channel, the time-delayed ultrasound receive channel signal received through the receive channel having the highest beamforming quality metric; and The ultrasound image is generated according to the selected time-delayed ultrasound receiving channel signals.

6. The method according to claim 1, wherein For each beamformed sound velocity, a beamforming quality metric is calculated for each receive channel at each of a plurality of depths.

7. The method according to claim 1, wherein For each beamformed sound velocity, a beamforming quality metric is calculated for each receive channel at each of a plurality of overlapping or non-overlapping depth ranges.

8. The method according to claim 1, wherein The ultrasound receive channel signal set is a first ultrasound receive channel signal set obtained at a transmit event, and further comprising repeating the time delay, beamforming quality metric calculation, and ultrasound receive channel signal selection for each additional ultrasound receive channel signal set obtained at each additional transmit event.

9. An ultrasound system, comprising: a plurality of ultrasonic transducers configured to transmit and receive ultrasonic signals; a memory storing instructions; and a processor configured to execute the instructions to: collecting an ultrasound receiving channel signal set via the plurality of ultrasound transducers; calculating a corresponding set of beamforming quality metrics for each of a plurality of time-delayed ultrasound receive channel signal sets, wherein each time-delayed ultrasound receive channel signal set is time-delayed from the ultrasound receive channel signal set based on a different beamforming sound velocity; Generating an ultrasound image based on selected time-delayed ultrasound receive channel signals of the plurality of time-delayed ultrasound receive channel signals based on each respective set of beamforming quality metrics; wherein the set of ultrasound receive channel signals is received via a set of receive channels, each receive channel coupled to an ultrasound transducer of the plurality of ultrasound transducers, and wherein each beamforming quality metric comprises a measure of similarity between the selected time-delayed ultrasound receive channel signals; each beamforming quality metric comprises a respective coherence metric for each receive channel, each coherence metric comprising a sum of absolute values ​​of summed time-delayed channel signals for a respective subset of receive channels to absolute values ​​of time-delayed channel signals for the respective subset of receive channels, the respective subset of receive channels comprising the receive channel and one or more adjacent receive channels.

10. The system according to claim 9, wherein: Generating an ultrasound image according to the selected time-delayed ultrasound receiving channel signals includes: calculating, for each receive channel, a weighted sum of each time-delayed ultrasound receive channel signal received through the receive channel, wherein each time-delayed ultrasound receive channel signal is weighted based on a corresponding beamforming quality metric calculated for the receive channel and the time-delayed ultrasound receive channel signal; and The ultrasound image is generated according to each weighted sum.

11. The system according to claim 9, wherein: Generating an ultrasound image according to the selected time-delayed ultrasound receiving channel signals includes: selecting, for each receive channel, the time-delayed ultrasound receive channel signal received through the receive channel having the highest beamforming quality metric; and The ultrasound image is generated according to the selected time-delayed ultrasound receiving channel signals.

12. The system according to claim 9, wherein: A corresponding set of beamforming quality metrics is calculated at each of a plurality of depths for each of the plurality of time-delayed ultrasound receive channel signal sets.

13. A method for generating an ultrasound image based on a selected set of time-delayed received channel signals, the method comprising: For each time-delayed receive channel signal of the selected set, independently selecting the time-delayed receive channel signal from among a plurality of possible time-delayed receive channel signals based on a set of beamforming quality metrics calculated for each time-delayed receive channel signal of the plurality of possible time-delayed receive channel signals; each beamforming quality metric comprising a measure of similarity between the selected time-delayed ultrasound receive channel signals; each beamforming quality metric comprising a respective coherence metric for each receive channel, each coherence metric comprising a sum of an absolute value of the summed time-delayed channel signals for a respective receive channel subset to an absolute value of the time-delayed channel signals for the respective receive channel subset, the respective receive channel subset comprising the receive channel and one or more adjacent receive channels.

14. The method according to claim 13, wherein: The multiple possible time-delayed received channel signals are generated by collecting an original received channel signal set and storing it in a memory, and performing multiple time delays on the original received channel signal set, each time delay using a corresponding different beamforming sound speed, so that a time-delayed received channel signal set is generated for each beamforming sound speed in the possible beamforming sound speed set.

15. The method according to claim 14, wherein Each received channel signal of the set of original received channel signals is received via a separate received channel, wherein each beamforming quality metric of the set of beamforming quality metrics is calculated for the corresponding received channel by calculating a coherence metric over a moving window of the time-delayed received channel signals, the moving window being centered around the received channel.

16. The method according to claim 15, wherein Independently selecting the time-delayed receive channel signal from among the plurality of possible time-delayed receive channel signals based on the set of beamforming quality metrics includes, for a given receive channel, selecting the time-delayed receive channel signal having a highest beamforming quality metric among all time-delayed receive channel signals received through the receive channel for a given depth and transmit event.

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