Retrospective transmit focusing using transmit rate systems, devices, and methods

Abstract

The ultrasound imaging system includes an array of acoustic elements configured to transmit ultrasonic energy at a first transmit rate and receive echoes associated with the ultrasonic energy transmitted at the first transmit rate, the system further including a processor circuit in communication with the array of acoustic elements, the processor configured to generate a plurality of multilines based on the received echoes, determine a second transmit rate, determine a set of transmit focus delays based on the second transmit rate, adjust the plurality of multilines with the set of transmit focus delays, generate an image based on the adjusted plurality of multilines, and output the generated image to a display in communication with the processor circuit.

Description

[Technical Field]

[0001]

[0001] The present disclosure relates generally to ultrasound imaging, and in particular to retrospective transmit focusing used for tissue aberration correction. More specifically, the present disclosure relates to retrospective transmit focusing for ultrasound transmissions based on a transmit rate that may or may not be the same as the transmit rate used for the ultrasound transmission. [Background technology]

[0002]

[0002] An ultrasound probe is configured to transmit ultrasound energy at a particular transmission velocity (e.g., a particular speed of sound). However, differences in density and / or other properties of the medium being imaged cause the ultrasound energy to propagate through the medium at a velocity (e.g., actual transmission velocity) that differs from the configured transmission velocity (e.g., expected transmission velocity). As an illustrative example, ultrasound energy travels at a relatively high transmission velocity (e.g., 1540 m / s) through tissue with a low fat content and / or high density, whereas ultrasound energy travels at a relatively low transmission velocity (e.g., 1480 m / s) through fatty tissue, such as breast tissue. The difference between the expected transmission velocity used to transmit ultrasound energy and the actual transmission velocity at which the ultrasound energy travels within the medium results in tissue aberrations. That is, images generated based on ultrasound energy contain distortions (e.g., blurring) due to the difference in transmission velocities.

[0003]

[0003] In some cases, an ultrasound probe is configured for ultrasound transmission at a particular transmit rate based on a transmit pulse pattern. The transmit pulse pattern is used to activate transducer elements of the ultrasound probe so that ultrasound energy is transmitted, for example, at a desired transmit rate. Configuring an ultrasound probe with a new transmit pulse pattern to affect a desired transmit rate for transmitting ultrasound energy is expensive in terms of resources (e.g., time, cost, materials, etc.). For example, the development and testing required to demonstrate the safety and effectiveness of a new transmit pulse pattern can take several months. Summary of the Invention

[0004]

[0004] Embodiments of the present disclosure relate to retroactive transmit focusing based on a speed of sound, which may or may not be the same as the transmit speed used for ultrasound transmission. For example, techniques described herein may be used to transmit focus ultrasound imaging data associated with ultrasound transmissions transmitted at a first transmit speed based on a different second transmit speed. Specifically, the ultrasound imaging system determines transmit focus weights and / or delays based on the second transmit speed and applies them to the ultrasound imaging data. Thus, the ultrasound imaging system effectively refocuses the transmit beam pattern corresponding to the first transmit speed based on the second transmit speed. In this manner, ultrasound data corresponding to transmissions at a particular transmit speed are adjusted to produce an image as if the transmissions had occurred at a different transmit speed. Thus, tissue aberrations due to differences between the transmit speed at the ultrasound probe and the transmit speed through the medium are reduced, and the use of ultrasound imaging systems configured to transmit ultrasound energy at a particular transmit speed is extended to imaging tissues with a wider range of characteristics (e.g., corresponding to various ultrasound propagation velocities). As such, a single transmit pulse pattern may be used across a variety of ultrasound imaging applications, such as breast imaging, vascular imaging, etc. Thus, the usefulness of ultrasound imaging systems is increased and the costs associated with developing and / or implementing ultrasound imaging systems are reduced.

[0005] In some aspects, an ultrasound imaging system includes an array of acoustic elements configured to transmit ultrasonic energy at a first transmit rate and receive echoes associated with the ultrasonic energy transmitted at the first transmit rate. The system further includes a processor circuit in communication with the array of acoustic elements. The processor can be configured to generate a plurality of multilines based on the received echoes, determine a second transmit rate, determine a set of transmit focus delays based on the second transmit rate, adjust the plurality of multilines using the set of transmit focus delays, generate an image based on the adjusted plurality of multilines, and output the generated image to a display in communication with the processor circuit.

[0006] In some aspects, an ultrasound imaging system includes a plurality of delay lines in communication with an array of acoustic elements and a processor circuit, the processor circuit being further configured to control the plurality of delay lines to delay the plurality of multi-lines according to a set of transmit focus delays to coordinate the plurality of multi-lines.

[0007] In some aspects, the processor circuitry can be further configured to determine a set of transmit focus weights based on the second transmit rate and to adjust the plurality of multilines using the set of transmit focus weights. In some aspects, the ultrasound imaging system further includes a multiplier in communication with the array of acoustic elements and the processor circuitry. Further, the processor circuitry can be configured to control the multiplier to apply the set of transmit focus weights to the plurality of multilines to adjust the plurality of multilines.

[0008] In some aspects, the ultrasound imaging system includes a summer in communication with the processor circuit and the array of acoustic elements. The summer can be configured to sum the conditioned multilines to generate transmit-focused image data. The processor circuit can be configured to generate an image further based on the transmit-focused image data.

[0009]

[0009] In some aspects, the processor circuitry can be configured to determine the set of transmit focus delays further based on a model of the ultrasonic energy transmitted at the second transmit rate.

[0010] In some aspects, the array of acoustic elements can be configured to transmit ultrasonic energy at a first focal depth. In such aspects, the processor circuit can be configured to determine a set of transmit focus delays further based on a model of ultrasonic energy transmitted at a second focal depth. The processor circuit can be further configured to determine the second focal depth based on a second transmit rate.

[0011] In some aspects, the ultrasound energy includes multiple ultrasound beams. Further, the array of acoustic elements can be configured to transmit each of the multiple ultrasound beams from a respective transmit beam location. In some aspects, the multiple multilines correspond to imaging data associated with receive line locations along which echoes are received for each of the multiple ultrasound beams.

[0012] In some aspects, the processor circuitry can be configured to determine the second transmission rate based on user input, the user input including a selection of the second transmission rate from among a set of predetermined transmission rates.

[0013] In some aspects, the processor circuitry can be configured to generate the image further based on the additional adjusted multilines, where the adjusted multilines correspond to first lines of the image and the additional adjusted multilines correspond to second lines of the image.

[0014] In some aspects, the ultrasound imaging system includes a display.

[0015] In some aspects, a method for retrospectively transmit focusing ultrasound data for ultrasound imaging includes controlling, by a processor circuit, an array of acoustic elements in communication with the processor circuit to transmit ultrasound energy at a first transmit rate and receive echoes associated with the transmitted ultrasound energy. The method further includes generating, by the processor circuit, a plurality of multilines based on the received echoes. The method also includes determining, by the processor circuit, a second transmit rate and determining, by the processor circuit, a set of transmit focus delays based on the second transmit rate. The method further includes adjusting, by the processor circuit, the plurality of multilines using the set of transmit focus delays and generating, by the processor circuit, an image based on the adjusted plurality of multilines. The method further includes outputting, by the processor circuit, the generated image to a display in communication with the processor circuit.

[0016]

[0016] Further aspects, features, and advantages of the present disclosure will become apparent from the following detailed description.

[0017]

[0017] Exemplary embodiments of the present disclosure will now be described with reference to the accompanying drawings. [Brief explanation of the drawings]

[0018] [Figures 1A-1C]

[0018] FIG. 1 is a diagram of ultrasound beam transmission according to an aspect of the present disclosure. [Figure 2]

[0019] 1 is a schematic diagram of an ultrasound imaging system according to aspects of the present disclosure. [Figure 3]

[0020] FIG. 2 is a schematic diagram of a processor circuit according to an aspect of the present disclosure. [Figure 4A-4B]

[0021] 10 is a plot of a simulated transmit beam pattern according to an aspect of the present disclosure. [Figure 5]

[0022] FIG. 1 is a flow diagram of a method for retroactive transmit focusing based on transmit rate, according to an aspect of the present disclosure. [Figure 6]

[0023] FIG. 10 is a flow diagram of a method for transmission focusing multi-lines based on transmission rate, according to an aspect of the present disclosure. [Figure 7A-7C]

[0024] 10 is a plot of a transmit beam pattern with retrospectively transmit-focused ultrasound image data, according to an aspect of the present disclosure. [Figure 8]

[0025] 1 is a plot of a point spread function according to an aspect of the present disclosure. [Figure 9A-9B]

[0026] 1 is an ultrasound image of breast tissue, according to an aspect of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0019]

[0027] To promote an understanding of the principles of the present disclosure, reference will now be made to the embodiments illustrated in the drawings, and specific terminology will be used to describe the embodiments. It will nevertheless be understood that no limitations on the scope of the present disclosure are intended. Any alterations and further modifications to the described devices, systems, and methods, and further applications of the principles of the present disclosure, as would normally occur to one skilled in the art to which this disclosure pertains, are fully intended and encompassed by this disclosure. In particular, it is fully intended that features, components, and / or steps described with respect to one embodiment may be combined with features, components, and / or steps described with respect to other embodiments of the present disclosure. However, for the sake of brevity, many iterations of these combinations will not be described individually.

[0020]

[0028] 1A-1C illustrate the transmission of ultrasound beams and the reception of corresponding echoes used to generate multilines. One example of transmitting ultrasound beams and receiving corresponding echoes for the generation of multilines is described in U.S. Patent No. 8,137,272, entitled "Ultrasonic Synthetic Transmit Focusing with a Multiline Beamformer," filed April 17, 2007, and incorporated herein by reference in its entirety. More specifically, FIG. 1A illustrates a profile 10 of a first transmit beam (e.g., an ultrasound beam) transmitted by a transducer array 8 included in an ultrasound probe. FIG. 1A also includes an orthogonal view 20 of the first transmit beam, illustrating a center lobe 20A and side lobes on either side of the center lobe 20A. Thus, the first transmit beam exhibits a relatively constant power level below an intensity peak at the center of the beam (e.g., center lobe 20A). In some embodiments, the power level of the beam is selected (eg, by a designer) at any suitable level (eg, 3 dB, 6 dB, 20 dB, etc.).

[0021]

[0029] As further shown, the first transmit beam has a focal point 12 at the narrowest width of the first transmit beam profile 10. That is, for example, the first transmit beam reaches its narrowest focus at focal region 12 and then diverges. In some examples, focal point 12 corresponds to a point at which the first transmit beam is focused by transmit focusing and / or beamforming (e.g., focusing that affects the output at transducer array 8) during transmission of the first transmit beam. As described in more detail below, focal point 12 is expanded using techniques described herein.

[0022]

[0030] A first transmit beam is transmitted with a width that includes multiple receive lines 14, 16, and 18. Following transmission of the first transmit beam, echoes are received and focused along receive line locations 14, 16, and 18. More specifically, as described in more detail below, echoes received by transducer elements of a receive aperture (e.g., in transducer array 8) in response to a single transmit beam are delayed and summed in three different ways to form multiple lines at various line locations 14, 16, and 18. In the illustrated embodiment, receive line 16 is received below the center of the first transmit beam, and receive lines 14 and 18 are steered and focused laterally to be received on either side of the central line (e.g., receive line 16). As further shown, near-field and far-field portions of outer lines 14 and 18 are within first transmit beam profile 10, while intermediate-field (e.g., central) portions of receive lines 14 and 18 are not included within first transmit beam profile 10. Thus, in some embodiments, echoes and / or echo portions within the near-field and far-field portions are received along lines 14 and 18 from transmit energy on either side of a central line position (e.g., corresponding to receive line 16). As such, objects in the image field are sampled on either side of the central line position (e.g., corresponding to receive lines 14 and 18, respectively). Thus, for efficient image reception and resolution, the laterally spread energy of the first transmit beam in the near and far fields is utilized.

[0023]

[0031] FIG. 1B shows a second transmit beam profile 10′. The second transmit beam is transmitted by shifting the transmit aperture (e.g., in transducer array 8) one receive line spacing to the right relative to the transmit aperture of the first transmit beam. The second transmit beam profile 10′ is similar to the first transmit beam profile 10, and although not shown, an orthogonal view of the second transmit beam is similar to the orthogonal view 20 of the first transmit beam. Thus, as with the first transmit beam, the second transmit beam profile 10′ spans three receive lines 16′, 18′, and 22. Specifically, echoes along the three receive lines 16′, 18′, and 22 are simultaneously received and beamformed in response to the transmission of the second transmit beam. That is, for example, echoes received by transducer elements of a receive aperture (e.g., in transducer array 8) are delayed and summed in three different ways to form multiple lines at various line locations 16', 18', and 22. Because the second transmit beam is transmitted from an aperture that has been moved relative to the first transmit beam, receive line 16' is aligned with receive line 16 from the first transmit, receive line 18' is aligned with receive line 18 from the first transmit, and receive line 22 is positioned to the right of center line 18' of the second transmit.

[0024]

[0032] FIG. 1C shows a third transmit beam profile 10″. The third transmit beam is transmitted by shifting the transmit aperture (e.g., in transducer array 8) one receive line spacing to the right relative to the transmit aperture of the second transmit beam. The third transmit beam profile 10″ is similar to the first transmit beam profile 10 and / or the second transmit beam profile 10′, and although not shown, an orthogonal view of the third transmit beam is similar to the orthogonal view 20 of the first transmit beam. The transmit beam profile 10″ of the third transmit beam includes at least a portion of three receive lines 18″, 22′, and 24. As such, echoes along the three receive lines 18″, 22′, and 24 are simultaneously received and beamformed in response to the transmission of the second transmit beam. That is, for example, echoes received by transducer elements of a receive aperture (e.g., in transducer array 8) are delayed and summed in three different ways to form multiple lines at various line locations 18", 22', and 24. The illustrated receive lines 18", 22', and 24 are spaced from one another by the same spacing as receive lines 14, 16, and 18 and receive lines 16', 18', and 22. Thus, receive line 22' is axially aligned with receive line 22 of the second transmit beam. Furthermore, receive line 18" is axially aligned with receive line 18' of the second transmit beam and receive line 18 of the first transmit beam. Thus, objects in the paths of receive lines 18, 18', and 18" are sampled by three receive lines, each corresponding to a different transmit beam (e.g., the first transmit beam, the second transmit beam, and the third transmit beam, respectively). In this manner, echoes corresponding to the first, second, and third transmit beams are co-aligned at receive lines 18, 18', and 18". The co-aligned echoes combine to generate a line of image data along the alignment line (e.g., corresponding to receive lines 18, 18', and 18"). The line of image data is focused to a greater depth of field than image data formed using any individual receive line, resulting in an extended transmit focus effect.In this way, focusing is effective for a greater depth of field because the echo energy from the three beam transmissions is combined to produce the resulting image data, as described in more detail below.

[0025]

[0033] In some embodiments, the transmission of ultrasound energy (e.g., ultrasound beams) and the reception of corresponding echoes are repeated (e.g., continued) across the image field in the manner shown in FIGS. 1A-1C until the entire image field has been scanned. Furthermore, for a given line location, after echoes for each of the receive lines (e.g., the maximum number of receive lines) corresponding to the location have been received, the receive lines for the line location are processed together (e.g., in parallel). As an illustrative example, the maximum number of receive lines corresponding to the line locations shown in FIGS. 1A-1C is three. Thus, three receive lines corresponding to the same line location, such as 18, 18', and 18'', are received before the receive line for the line location is processed. After the three receive lines have been received, the receive lines are processed together to generate a line of image data at the corresponding location. Thus, a first set of receive lines (e.g., 14, 16, and 18) corresponding to a first transmit beam and a second set of receive lines 16', 18', and 22 are stored until at least a third set of receive lines (e.g., 18", 22, and 24) are received. Thereafter, receive lines 18, 18', and 18" from the first set of receive lines, the second set of receive lines, and the third set of receive lines, respectively, are processed together. In this manner, processing of received echoes does not rely on storing pre-summed radio frequency (RF) data from the transmit. Instead, storage use is reduced (e.g., minimized) to storing a set of receive lines corresponding to a line position before the receive line for that line position is processed, at which point storage is released for storing subsequent receive lines.

[0026]

[0034] Although the transmit beam profiles shown in FIGS. 1A-1C are described herein as including three receive lines, other suitable numbers of spaced-apart, simultaneously received lines may be used, such as four, six, eight, twelve, sixteen, etc. In some cases, increasing the number of receive lines received at the transducer array 8 involves configuring the transducer array to transmit according to a lower F-number (e.g., a lower F-number relative to an F-number corresponding to fewer receive lines) so that the ultrasonic energy transmitted by the transducer array 8 insonifies a larger spread of receive line locations. Thus, transmitting with a smaller transmit aperture generates a wider beam. Therefore, increasing the number of receive lines received at the transducer array 8 involves reducing the number of elements of the transducer array 8 used to transmit ultrasonic energy. Furthermore, while convergent transmit beams are shown in FIGS. 1A-1C, embodiments are not so limited. In some embodiments, for example, divergent transmit beams are transmitted by the transducer array 8 and focused according to techniques described herein.

[0027]

[0035] Referring now to FIG. 2, a block diagram of an ultrasound imaging system 150 is shown, according to an embodiment of the present disclosure. The system 150 is used to scan a region or volume of a patient's body. The system 150 includes an ultrasound imaging probe 102 in communication with a host 130 (e.g., via a communications interface or link). The probe 102 includes a transducer array 104, a transmit beamformer 106, and / or a transmit / receive switch 108 (e.g., a crosspoint switch). The host 130 (e.g., a console) includes multi-line processors 110a-110n, a line store 112, a transmit focuser 132, a transmit focus processor 134, an image processor 122, and a display 124.

[0028]

[0036] In some embodiments, the probe 102 is an external ultrasound imaging device including a housing configured for handheld operation by a user. The transducer array 104 is similar to the transducer array 8 of FIG. 1. The transducer array 104 may be further configured to acquire ultrasound data while a user grasps the housing of the probe 102 such that the transducer array 104 is positioned adjacent to or in contact with the patient's skin. The probe 102 is configured to acquire ultrasound data of an anatomical structure within the patient's body while the probe 102 is positioned outside the patient's body. In some embodiments, the probe 102 may be an external ultrasound probe and / or a transthoracic echocardiography (TTE) probe.

[0029]

[0037] In other embodiments, the probe 102 may be an internal ultrasound imaging device and includes a housing configured to be positioned within a lumen of a patient's body, including the patient's coronary vasculature, peripheral vasculature, esophagus, heart chamber, or other body lumen or cavity. In some embodiments, the probe 102 may be an intravascular ultrasound (IVUS) imaging catheter or an intracardiac echocardiography (ICE) catheter. In other embodiments, the probe 102 may be a transesophageal echocardiography (TEE) probe. The probe 102 may be any suitable form for any suitable ultrasound imaging application, including both external and internal ultrasound imaging.

[0030]

[0038] For an ultrasound imaging device, the transducer array 104 emits ultrasound signals toward an anatomical object in a patient and receives echo signals that are reflected from the object and return to the transducer array 104. The ultrasound transducer array 104 can include any suitable number of acoustic elements, including one or more acoustic elements and / or multiple acoustic elements. In some examples, the transducer array 104 includes a single acoustic element. In some cases, the transducer array 104 includes an array of acoustic elements having any number of acoustic elements in any suitable configuration. For example, the transducer array 104 can include from 1 to 10,000 acoustic elements, including values ​​such as 2 acoustic elements, 4 acoustic elements, 36 acoustic elements, 64 acoustic elements, 128 acoustic elements, 500 acoustic elements, 812 acoustic elements, 1,000 acoustic elements, 3,000 acoustic elements, 8,000 acoustic elements, and / or other greater and lesser values. In some examples, the transducer array 104 includes an array of acoustic elements having any number of acoustic elements in any suitable configuration, such as a linear array, a planar array, a curved array, a curvilinear array, a circumferential array, an annular array, a phased array, a matrix array, a one-dimensional (1D) array, a 1.x-dimensional array (e.g., a 1.5D array), or a two-dimensional (2D) array. The array of acoustic elements (e.g., one or more rows, one or more columns, and / or one or more orientations) can be controlled and actuated uniformly or independently. The transducer array 104 can be configured to obtain one-dimensional, two-dimensional, and / or three-dimensional images of the patient's anatomy. In some embodiments, the transducer array 104 includes piezoelectric micromachined ultrasound transducers (PMUTs), capacitive micromachined ultrasound transducers (CMUTs), single crystal, lead zirconate titanate (PZT), PZT composites, other suitable transducer types, and / or combinations thereof.

[0031]

[0039] The object may include any anatomical structure or feature, such as a patient's blood vessels, nerve fibers, airways, mitral valve leaflets, cardiac structures, abdominal tissue structures, appendix, large intestine (or colon), small intestine, kidneys, liver, and / or other anatomical structures. In some aspects, the object may include at least a portion of a patient's large intestine, small intestine, cecal pouch, appendix, terminal ileum, liver, upper stomach, and / or psoas muscles. The present disclosure may be implemented in the context of any number of anatomical locations and tissue types, including, but not limited to, organs, including the liver, heart, kidneys, gallbladder, pancreas, and lungs; ducts; intestines; nervous system structures, including the brain, dural sac, spinal cord, and peripheral nerves; the urinary tract; and valves, blood, ventricles, or other parts of the heart, abdominal organs, and / or other systems of the body. In some embodiments, the object may include a malignant growth, such as a tumor, a cyst, a lesion, a hemorrhage, or a blood collection within any part of the human anatomy. The anatomical structure may be a blood vessel, such as an artery or vein, of a patient's vascular system, including the cardiovascular system, peripheral vascular system, neurovascular system, renal vascular system, and / or any other suitable lumen within the body. In addition to natural structures, the present disclosure may be implemented in the context of artificial structures, such as, but not limited to, heart valves, stents, shunts, filters, implants, and other devices.

[0032]

[0040] The beamformer 106 is connected to the transducer array 104. The beamformer 106 controls the transducer array 104, for example, for the transmission of ultrasound signals. In such an example, the beamformer 106 is a transmit beamformer. In some embodiments, the transmit beamformer 106 applies time delays to signals transmitted to individual acoustic transducers in the array of the transducer 104 so that the acoustic signals are steered in any suitable direction propagating away from the probe 102. To this end, selected groups of transducer elements (e.g., acoustic elements) of the transducer array 104 of the ultrasound probe 102 are activated by the transmit beamformer 106 at respective delayed times. In this manner, the ultrasound probe 102 is used to transmit ultrasound beams (e.g., ultrasound energy) that are focused at selected focal regions associated with respective transmit directions from respective origins along the transducer array 104. For example, the transmit beamformer 106 activates various groups of transducer elements (e.g., various transmit apertures) of the transducer array 104 such that the ultrasound probe 102 transmits first, second, and third beams shown in FIGS. 1A-1C and corresponding to profiles 10, 10', and 10'', respectively. In some examples, the beamformer 106 may be a receive beamformer and may control the reception of ultrasound echoes at the transducer array 104. The receive beamformer 106 includes multiple stages of beamforming.

[0033]

[0041] As shown, the beamformer 106 is connected to the transducer array 104 by a transmit / receive switch 108. The transmit / receive switch 108 includes a crosspoint switch. Additionally, the transmit / receive switch 108 is implemented to direct high-voltage transmit pulses from the transmit beamformer 106 and / or signals from the host 130 to the ultrasound probe 102, and to direct ultrasound echoes and / or signals from the ultrasound probe 102 to the host 130. Thus, the transmit / receive switch 108 protects circuitry within the ultrasound probe 102 and / or host 130 used for receive, including circuitry configured for lower voltage operation, from the higher voltages of the transmit pulses.

[0034]

[0042] In response to each transmit beam, the ultrasound probe 102 receives echoes (e.g., at the transducer array 104), and the host 130 receives the echoes and / or signals associated with the echoes from the ultrasound probe 102. In the host 130, the echoes received from the ultrasound probe 102 are applied to inputs of the multi-line processors 110a-n. The multi-line processors 110a-n may also be represented as processor circuits and may include other components in communication with the multi-line processors 110a-n, such as memory. The multi-line processors 110a-n may include a central processing unit (CPU), a graphics processing unit (GPU), a digital signal processor (DSP), an application specific integrated circuit (ASIC), a controller, a field programmable gate array (FPGA) device, another hardware device, a firmware device, or any combination thereof configured to perform the operations described herein. The multi-line processors 110a-n may also be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

[0035]

[0043] Additionally, the multiline processors 110a-n are configured to process ultrasound echoes. For example, each of the multiline processors 110a-n includes a receive beamformer configured to apply a respective set of delays to received echoes. In some embodiments, the multiline processors 110a-n provide the first or only stage of transmit beamforming. In other embodiments, the multiline processors 110a-n provide the second or subsequent stage of receive beamforming (e.g., when the first stage of receive beamforming is performed by the beamformer 106). The receive beamformer also applies apodization weights to echoes received from elements of the transducer array 104. As a result of the applied sets of delays and / or apodization weights, the multiline processors 110a-n form differently steered receive beams corresponding to the same transmit beam. More specifically, the multiline processors 110a-n generate multilines (e.g., multiline echoes) corresponding to echoes received along various receive lines for a given transmit beam. For example, multiline processors 110a-n generate multilines corresponding to receive lines 14, 16, and 18 (FIG. 1A), respectively, for the first transmit beam, multilines corresponding to receive lines 16', 18', and 22 (FIG. 1B), respectively, for the second transmit beam, and multilines corresponding to receive lines 18'', 22', and 24 (FIG. 1C), respectively, for the third transmit beam.

[0036]

[0044] The multilines generated in multiline processors 110a-n are output to line store 112. Line store 112 includes memory and / or storage, such as one or more registers, that stores the multilines at least until each multiline corresponding to a particular receive line (e.g., required to form a line in an image) has been acquired. For example, for an image line corresponding to receive line positions 18, 18', and 18", line store 112 stores a first set of multilines corresponding to the first transmit beam and receive line positions 14, 16, and 18, and a second set of multilines corresponding to the second transmit beam and receive line positions 16', 18', and 22, as described above, until at least a third set of multilines corresponding to the third transmit beam and receive lines 18", 22', and 24 have been received.

[0037]

[0045] After each multiline corresponding to a particular image line is received in line store 112, line store 112 outputs the multiline corresponding to the receive line to transmit focuser 132. As shown, transmit focuser 132 includes weights 114a-n, multipliers 116a-n, delay lines 118a-n, and summer 120. In some embodiments, the number of weights 114a-n, multipliers 116a-n, and delay lines 118a-n corresponds to the number of multiline processors 110a-n, which in turn corresponds to the number of receive line positions (e.g., number of multilines) generated for a particular line of the image. Furthermore, transmit focuser 132 may be implemented as a combination of software and / or hardware components. Furthermore, transmit focuser 132 may be implemented as a combination of analog and / or digital components. For example, delay lines 118a-n may be implemented as digital delay lines by storing data (e.g., multi-line data) in memory and reading out the data at a later time corresponding to the desired delay. Additionally or alternatively, delay lines 118a-n may be implemented with shift registers of different lengths and / or clock signals. In some embodiments, delay lines 118a-n are implemented with interpolating beamformers. Similarly, summer 120 may be implemented with summer circuits and / or as a digital summer.

[0038]

[0046] In some embodiments, transmit focuser 132 applies a respective apodization weight to each multiline in a group of multilines corresponding to a particular line of the image (e.g., in a group of multilines received from line store 112). In particular, each of multipliers 116a-n receives as input a multiline in the group of multilines and a corresponding transmit focus weight from weights 114a-n, and outputs an adjusted multiline (e.g., a weighted multiline). In some embodiments, weights 114a-n are configured to weight each multiline as a function of a round-trip impulse response associated with the multiline. Furthermore, weights 114a-n are configured by transmit focus processor 134, as described in more detail below.

[0039]

[0047] The transmit focuser 132 additionally or alternatively delays the multilines received from the line store 112. For example, using delay lines 118a-n, the transmit focuser 132 applies a respective delay to each multiline in a group of multilines corresponding to a particular line of the image. The delay equalizes phase shift variations present from line to line for multilines due to different transmit-receive beam position combinations. Thus, signal cancellation caused by phase differences of the combined multilines is minimized and / or avoided. As such, the delay applied by the delay lines 118 depends on the position of the multiline / receive line relative to the center of the corresponding transmit beam. As an illustrative example, for the first transmit beam shown in FIG. 1A, the delay applied to the multiline associated with receive line position 18 depends on the distance of the receive line position from receive line position 16 (e.g., the center of the first transmit beam). Furthermore, the delays applied by the delay lines 118a-n are configurable by the transmit focus processor 134, as described in more detail below.

[0040]

[0048] The transmit focuser 132 is further configured to sum the adjusted (e.g., weighted and / or delayed) multilines in a summer 120. In particular, the summer 120 sums (e.g., combines) each adjusted multiline in a group of multilines corresponding to a particular line of the image. The output of the summer 120 and / or the transmit focuser 132 is coupled to the image processor 122. The image processor thus receives the combined adjusted multilines. The image processor 122 then generates an image based on the combined adjusted multilines. The image processor 122 further performs scan conversion or other processing to improve the generated image. The resulting image is output for display on the display 124.

[0041]

[0049] As described above, the transmit focuser 132 is in communication with the transmit focus processor 134, which configures the weights 114a-n and / or delay lines 118a-n. The transmit focus processor 134 may also be represented as a processor circuit. The transmit focus processor 134 may include a central processing unit (CPU), a graphics processing unit (GPU), a digital signal processor (DSP), an application specific integrated circuit (ASIC), a controller, a field programmable gate array (FPGA) device, another hardware device, a firmware device, or any combination thereof configured to perform the operations described herein. The transmit focus processor 134 may also be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

[0042]

[0050] In some embodiments, the transmit focus processor 134 configures the weights 114a-n and / or configures the multipliers 116a-n to apply the weights 114a-n based on a weighting algorithm. For example, the weights applied to the multilines may be: Weight(X,Z)=amplitude(X,Z) (1) where X represents the azimuth angle of the received multiline relative to the beam axis of the corresponding transmit beam, X=0 corresponds to the central axis of the transmit beam, and Z represents the depth at which the multiline produces an image point. Furthermore, amplitude(X,Z) represents the insonification amplitude by the transmit wavefront (e.g., the wavefront of the transmit beam) at the point in the image field. By varying the weights as a function of depth (e.g., according to Equation 1), the transmit processor 134 retroactively and dynamically varies the size and shape (apodization) of the transmit aperture with depth. That is, for example, the transmit processor 134 varies the size and shape of the transmit aperture after the transmit beam is transmitted at the ultrasound probe 102.

[0043]

[0051] The transmit focus processor 134 configures the delay lines 118a-n (e.g., the delay that the delay lines affect) based on a delay algorithm. For example, the delay applied to the multiline by the delay lines 118 may be: Delay(X,Z)=propagation_time(X,Z)-propagation_time(0,Z) (2) where X represents the azimuth angle of the received multiline relative to the beam axis of the corresponding transmit beam, X=0 corresponds to the central axis of the transmit beam, and Z represents the depth at which the multiline produces an image point. Furthermore, propagation_time(X,Z) represents the propagation time for the transmit wavefront to reach the point represented by X and Z, and propagation_time(0,Z) represents the time to reach a point at the same depth but on-axis (e.g., on the central axis of the transmit beam).

[0044]

[0052] In some embodiments, the transmit focus processor 134 determines the results of the weighting algorithm (e.g., Equation 1) and / or the delay algorithm (e.g., Equation 2) based on a simulation (e.g., a model) of the transmit field. Specifically, the transmit focus processor 134 determines the values ​​of the function amplitude(X,Z) and / or the function propagation_time(X,Z) based on the simulation. For example, using a monochromatic simulation at multiple frequencies, the transmit focus processor 134 determines the propagation time based on the phase delay of the transmit field. Furthermore, the transmit focus processor 134 determines the amplitude based on averaging the amplitude of the transmit field at several simulated frequencies. In some embodiments, the transmit focus processor 134 then applies a depth-dependent normalization to the weights 114a-n. This normalization multiplies each weight at a given depth by a common factor. In some cases, the normalization is selected so that the speckle region has uniform intensity with depth.

[0045]

[0053] The transmit focus processor configures the transmit focuser 132 to retroactively transmit focus the transmit beam transmitted by the ultrasound probe 102 by configuring the delay lines 118a-n based on the delay algorithm (Equation 2) and / or the multipliers 116a-n and / or weights 114a-n based on the weighting algorithm (Equation 1). That is, for example, the transmit focus processor configures the delay lines 118a-n such that they, in conjunction with the summer 120, refocus multilines that are aligned together in a given direction. Such refocusing takes into account phase differences resulting from the use of various transmit beam positions for each multiline. As a result, the refocusing minimizes or prevents undesired phase cancellation in the combined multilines. Furthermore, the weights 114a-n weight the contributions of multilines relative to their respective proximity to the corresponding transmit beam. For example, transmit focus processor 134 configures weights 114a-n based on a weighting algorithm (e.g., Equation 1) and one or more simulations of the transmit field such that higher weights are applied to multi-lines having higher signal-to-noise ratios. As a result, the image generated and output to display 124 includes an expanded depth of field (e.g., an expanded focus relative to focus 12 with conventional focusing) and improved penetration (e.g., improved signal-to-noise ratio) along each receive line due to the combination of multiple samplings in each receive line direction.

[0046]

[0054] In some embodiments, the transmit focus processor 134 derives the delays for the configuration of delay lines 118a-n and / or the weights for the configuration of weights 114a-n based on a transmit field simulation that models the transmit characteristics of the beam transmitted by the ultrasound probe 102. These characteristics include, for example, the speed of sound used to transmit the transmit beam, the size and / or shape of the transmit aperture (e.g., the number and / or position of transducer elements in the transducer array 104 used to transmit the transmit beam), the focal depth of the transmit beam, etc. In some embodiments, the transmit processor 134 modifies one or more of these characteristics during the transmit field simulation compared to the values ​​used during transmission. For example, the transmit processor 134 uses a speed of sound that is different from the speed of sound used by the ultrasound probe 102 for transmitting the transmit beam to determine the delays for the configuration of delay lines 118a-n and / or the weights for the configuration of weights 114a-n. In this manner, the transmit focuser 132 transmit focuses multiple lines based on a different sound speed than that used for ultrasound transmission, which compensates for the difference between the expected sound speed corresponding to the sound speed setting in the ultrasound probe 102 and the actual sound speed due to the propagation of ultrasound energy through a particular medium, i.e., using transmit focusing based on the actual sound speed to provide tissue aberration correction (TAC), as described in more detail below.

[0047]

[0055] Although ultrasound imaging system 150 is shown and described as having certain components included within ultrasound probe 102 and certain components included within host 130, embodiments are not limited thereto. As such, in some embodiments, display 124 may be a standalone device in communication with host 130. Further, in some embodiments, beamformer 106 and / or switch may additionally or alternatively be included within host 130. In some embodiments, multiline processors 110a-n may be included within ultrasound probe 102. Furthermore, while certain components are shown separately, it is understood that one or more components may be included in a combined system and / or that certain components may perform one or more of the techniques described herein.

[0048]

[0056] In some embodiments, processors 110a-n, 134, and / or 122 may each be part of a combined system (e.g., host 130). For example, in some embodiments, processors 110a-n, 134, and / or 122 may be positioned within the same enclosure or housing. Furthermore, processors 110a-n, 134, and / or 122 may share one or more software or hardware components. As such, one or more of processors 110a-n, 134, and / or 122 may be implemented as a single processing system. In other embodiments, processors 110a-n, 134, and / or 122 may be separate systems but may communicate with each other. The processors may communicate with each other continuously or intermittently. The processors may communicate with each other or with the ultrasound probe, display 124, transmit focuser 132, etc. via one or more wired connecting cables including any suitable conductor, such as a single conductor, twisted pair, a Universal Serial Bus (USB) cable, or any other suitable connecting cable. Processors 110a-n, 134, and / or 122 may additionally or alternatively communicate with each other and / or with other components of ultrasound imaging system 150 via wireless connections, optical connections, or may be connected via any suitable type of removable memory or storage medium or any other suitable communication means. Any and / or all of processors 110a-n, 134, and / or 122 may include or be part of any suitable system or device, such as, but not limited to, a mobile console, a desktop computer, a laptop computer, a tablet, a smartphone, or any other suitable computing device.

[0049]

[0057] FIG. 3 is a schematic diagram of a processor circuit 300 according to an embodiment of the present disclosure. The processor circuit 300 or a similar processor circuit may be implemented in any suitable device or system previously disclosed. One or more processor circuits 300 may be configured to perform the operations described herein. The processor circuit 300 may include additional circuits or electronic components, such as those described herein. In one example, the one or more processor circuits 300 communicate with the transducer array 104, the beamformer 106, circuits, or other components within the ultrasound probe 102. Additionally, the one or more processor circuits 300 communicate with the line store 112, the transmit focuser 132, circuits, or other components within the host 130. The one or more processor circuits 200 also communicate with the display 124 and any other suitable components or circuits within the ultrasound imaging system 150. Additionally, host 130 and / or any of processors 110a-n, 134, and / or 122 may be similar to processor circuit 300. As shown, processor circuit 300 includes a processor 310, a memory 312 containing instructions 314, and a communications module 316. These elements communicate with each other directly or indirectly, for example, via one or more buses.

[0050]

[0058] The processor 310 may include a CPU, a GPU, a DSP, an application specific integrated circuit (ASIC), a controller, a field programmable gate array (FPGA), another hardware device, a firmware device, or any combination thereof configured to perform the operations described herein. The processor 310 may also be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

[0051]

[0059] The memory 312 may include cache memory (e.g., cache memory of the processor 310), random access memory (RAM), magnetoresistive RAM (MRAM), read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), flash memory, solid-state memory devices, hard disk drives, other forms of volatile and non-volatile memory, or a combination of various types of memory. In one embodiment, the memory 312 includes a non-transitory computer-readable medium. The memory 312 stores instructions 314. The instructions 314 include instructions that, when executed by the processor 310, cause the processor 310 to perform operations described herein with respect to the multiline processors 110a-n, the transmit focus processor 134, the image processor 122, etc. The instructions 314 may also be referred to as code. The terms "instructions" and "code" should be interpreted broadly to include any type of computer-readable statement. For example, the terms "instructions" and "code" refer to one or more programs, routines, subroutines, functions, procedures, etc. "Instructions" and "code" include a single computer-readable statement or many computer-readable statements.

[0052]

[0060] The communications module 316 may include any electronic and / or logical circuitry that facilitates the direct or indirect communication of data between the processor circuit 300, components of the host 130, components of the ultrasound probe 102, and / or the display 124. In that regard, the communications module 316 may be an input / output (I / O) device. For example, the communications module 316 may include a touch-sensitive pad or touchscreen display, a keyboard / mouse, a joystick, buttons, a scroll wheel, etc. In some examples, the communications module 316 facilitates direct or indirect communication between various elements of the processor circuit 300 and / or devices and systems of the ultrasound imaging system 150. Additionally, the communications module 316 facilitates wireless and / or wired communications between various elements of the devices and systems of the processor circuit 300 and / or ultrasound imaging system 150 using any suitable communications technology, such as a cable interface such as a USB, micro USB, Lightning, or FireWire interface, Bluetooth, Wi-Fi, ZigBee, Li-Fi, or a cellular data connection such as 2G / GSM, 3G / UMTS, 4G / LTE / WiMax, or 5G.

[0053]

[0061] Reference is now made to Figures 4A-4B, which show simulated transmit beam patterns. In Figures 4A-4B, the horizontal axis represents azimuth angle in any arbitrary units, and the vertical axis represents depth in any arbitrary units. Plots 400 and 450 in Figure 4A each show a respective simulated transmit beam pattern for ultrasonic energy traveling through a medium. For plot 400, the transmit beam pattern corresponds to transmitting ultrasonic energy from an ultrasonic probe (e.g., ultrasonic probe 102) at a transmission velocity of 1540 meters per second (m / s). Plot 450 shows a transmit beam pattern corresponding to transmitting ultrasonic energy from an ultrasonic probe at a transmission velocity of 1480 m / s.

[0054]

[0062] In some embodiments, an ultrasonic probe, such as ultrasonic probe 102, is configured (e.g., via beamformer 106) to transmit ultrasonic energy at a particular transmit velocity, such as the transmit velocity of 1540 m / s shown in FIG. 4A or the transmit velocity of 1480 m / s shown in FIG. 4B. For example, the beamformer 106 activates elements of the transducer array 104 with a transmit pulse pattern corresponding to the desired transmit velocity. Thus, the beamformer activates elements of the transducer array 104 with a first transmit pulse pattern for ultrasonic transmission at 1540 m / s and activates elements of the transducer array 104 with a different second transmit pulse pattern for ultrasonic transmission at 1480 m / s. While ultrasonic waves are configured to transmit ultrasonic energy at a particular transmit velocity (e.g., expected transmit velocity), ultrasonic energy propagates through a medium at a different velocity (e.g., actual transmit velocity) due to differences in density and / or other properties of the medium. As an illustrative example, ultrasound energy travels through tissue with low fat content and / or high density at a relatively high transmission velocity (e.g., 1540 m / s), while ultrasound energy travels through fatty tissue, such as breast tissue, at a relatively low transmission velocity (e.g., 1480 m / s).

[0055]

[0063] In the embodiment shown in Figures 4A-4B, the medium has an ultrasonic propagation velocity of 1480 m / s. Thus, plot 400 corresponds to ultrasonic energy transmitted at a transmission velocity of 1540 m / s (e.g., an expected transmission velocity of 1540 m / s), while the ultrasonic energy propagates through the medium at a transmission velocity of 1480 m / s (e.g., an actual transmission velocity of 1480 m / s). Thus, plot 400 illustrates an example of a transmit beampattern having a mismatch between the actual transmission velocity of ultrasonic energy in the medium and the expected transmission velocity used when transmitting with the ultrasonic probe. On the other hand, plot 450 illustrates an example of a transmit beampattern in which the actual transmission velocity of ultrasonic energy in the medium approximately matches the expected transmission velocity used when transmitting with the ultrasonic probe.

[0056]

[0064] Focal depth 402 corresponds to the focal depth of the transmit beam corresponding to an expected transmission velocity of 1540 m / s (e.g., the focal depth of plot 400), and focal depth 452 corresponds to the focal depth of the transmit beam corresponding to an expected transmission velocity of 1480 m / s (e.g., the focal depth of plot 450). As shown, focal depth 402 is lower than focal depth 452. Thus, FIGS. 4A-4B illustrate that a mismatch between the actual transmission velocity of ultrasound energy in a medium and the expected transmission velocity used when transmitting ultrasound energy in ultrasound probe 102 is associated with a change (e.g., a shift) in the focal depth of the resulting transmit beam pattern. In some cases, this change can cause image distortion (e.g., blurring and / or reduced image resolution) in images resulting from the ultrasound energy. This change in focal depth and / or the resulting image distortion may be referred to as tissue aberration.

[0057]

[0065] As an illustrative example, tissue aberrations occur when a host and / or ultrasound probe is not configured with a transmit pulse pattern that corresponds to the speed at which ultrasound energy propagates through a medium. Configuring an ultrasound host and / or ultrasound probe with a new transmit pulse pattern that affects the desired transmit speed for transmission of ultrasound energy is costly in terms of resources (e.g., time, cost, materials, etc.). For example, the development and testing required to demonstrate the safety and effectiveness of a new transmit pulse pattern can take several months. Therefore, alternative methods of tissue aberration correction (TAC) would increase the usefulness of ultrasound imaging systems and reduce the costs associated with developing and / or implementing ultrasound imaging systems.

[0058]

[0066] As described in more detail below, the ultrasound imaging system 150 is used for tissue aberration correction and / or retroactive transmit focusing of ultrasound imaging data based on a transmit speed different from the transmit speed used during ultrasound transmission. Specifically, the ultrasound imaging system 150 is used to transmit focus ultrasound imaging data associated with ultrasound transmission at a first transmit speed based on a second transmit speed that is different. For example, the ultrasound imaging system 150 determines and applies focus weights and / or delays to the multilines associated with the ultrasound transmission based on the second transmit speed. Thus, the ultrasound imaging system 150 effectively refocuses the transmit beam pattern corresponding to the first transmit speed based on the second transmit speed. In this manner, ultrasound data corresponding to transmission at a particular transmit speed is adjusted to generate an image as if the transmission had occurred at a different transmit speed. Thus, tissue aberrations due to differences between the transmit speed in the ultrasound probe and the transmit speed in the medium are reduced, and the use of an ultrasound imaging system configured to transmit ultrasound energy at a particular transmit speed is extended to imaging tissues with a wider range of characteristics (e.g., corresponding to various ultrasound propagation velocities).

[0059]

[0067] FIG. 5 is a flow diagram of a method 500 of retrospective transmit focusing based on a transmit rate different from the transmit rate used in an ultrasound probe (e.g., ultrasound probe 102) to transmit ultrasound energy, according to aspects of the present disclosure. One or more steps of method 500 are described with reference to FIG. 6. As shown, method 500 has multiple enumerated steps, but embodiments of method 500 may have additional steps before, after, or between the enumerated steps. In some embodiments, one or more of the enumerated steps may be omitted, performed in a different order, or performed simultaneously. The steps of method 500 may be performed by any suitable component within ultrasound imaging system 150, and all steps need not be performed by the same component. In some embodiments, one or more steps of method 500 may be performed by or at the direction of a processor circuit (e.g., processor circuit 300 (FIG. 3)) of ultrasound imaging system 150, including host 130, transmit focus processor 134, image processor 122, or any other component.

[0060]

[0068] In step 502, the method 500 includes controlling the array to transmit ultrasonic energy at a first transmit rate. For example, the host 130 controls the transducer array 104 to output ultrasonic energy at the first transmit rate according to a transmit pulse pattern. More specifically, the host 130 communicates with the beamformer 106, which, in response to this communication, activates one or more transducer elements of the transducer array 104 according to the transmit pulse pattern. As a result, the one or more transducer elements transmit ultrasonic energy at the first transmit rate.

[0061]

[0069] In some embodiments, the first transmission rate is a default transmission rate of the ultrasonic probe 102 and / or the host 130. For example, the ultrasonic probe 102 is pre-configured for transmitting ultrasonic energy at the first transmission rate, and / or the host 130 is pre-configured to control the ultrasonic probe 102 to transmit ultrasonic energy at the first transmission rate. For example, the host 130 is pre-configured with a transmit pulse pattern corresponding to the first transmission rate. Further, in some cases, the first transmission rate is the only transmission rate the ultrasonic probe 102 and / or the host 130 are configured to use. Additionally or alternatively, the host 130 determines the first transmission rate based on user input received at the host 130 via the communications module 316. In some embodiments, for example, the host 130 is pre-configured with multiple transmit pulse patterns corresponding to a respective set of predetermined transmission rates. In such cases, the user input selects a transmission rate from the set of predetermined transmission rates, and based on the selection, the host 130 selects a transmit pulse pattern for controlling the ultrasonic probe 102. As an illustrative example, the first transmission speed is 1540 m / s.

[0062]

[0070] At step 504, the method 500 includes receiving echoes. Specifically, the ultrasound probe 102 receives echoes associated with the ultrasound energy transmitted at the first rate. For example, after transmitting ultrasound energy at the first transmission rate, the ultrasound probe 102 controls operation of the transducer array 104 to receive echoes, and the transmit / receive switch 108 routes signals associated with the received echoes (e.g., electrical signals corresponding to the received echoes) to the host 130.

[0063]

[0071] At step 506, method 500 includes determining a second transmission rate. In some embodiments, host 130 determines the second transmission rate based on user input. For example, host 130 receives user input via communication module 316, which, as described above, includes an I / O device. As such, user input may be received via interaction with a graphical user interface (GUI), a touchscreen interface, a button, a mouse, a keyboard, a joystick, a trackpad, or the like. Further, the user input corresponds to a selection of the second transmission rate. For example, the user input selects the second transmission rate from among a set of transmission rates predetermined and / or preconfigured in host 130. For example, host 130 includes two or more transmission rates, each transmission rate corresponding to a different type of tissue. As such, the user input corresponds to a selection of a type of tissue, such as fatty or dense breast tissue, which is mapped to one of the transmission rates in host 130. Additionally or alternatively, the user input may select the second transmission rate from within a range of transmission rates supported in host 130. As an illustrative example, the transmission velocity range includes transmission velocities associated with the velocity of ultrasound energy in various biological materials (eg, various tissues), such as transmission velocities between 1460 m / s and 1620 m / s.

[0064]

[0072] Additionally or alternatively, the second transmission rate may be determined based on data received at the ultrasound imaging system 150. For example, the ultrasound imaging system 150 (e.g., the host 130) determines the second transmission rate based on an indication of the anatomical feature to be imaged received and / or detected at the ultrasound imaging system 150, the type and / or performance of a probe (e.g., the probe 102) connected to the system 150, patient data, etc. The indication of the anatomical feature corresponds to a user input selecting the anatomical feature. Additionally or alternatively, the ultrasound imaging system 150 may identify the anatomical feature based on one or more settings, such as a depth setting, a position and / or orientation of the probe 102, etc., used to image the feature. In some embodiments, for example, the ultrasound imaging system 150 includes a mapping (e.g., a table) of the indication of the anatomical feature to the imaged anatomical feature to determine the anatomical feature. In some embodiments, ultrasound imaging system 150 is trained to identify the anatomical feature and / or the second transmission rate based on a deep learning network, such as a convolutional neural network (CNN), or another suitable implementation of an artificial intelligence system or structure, including, for example, a random forest deep learning technique or a regression analysis technique. For example, ultrasound imaging system 150 classifies data received at ultrasound imaging system 150 as corresponding to a particular anatomical feature and / or transmission rate based on the deep learning network and / or the artificial intelligence system. Additionally, patient data, including diagnoses, weight, body mass index (BMI), medical history, etc., associated with the patient, is entered into ultrasound imaging system 150 and / or retrieved from a local or remote data store (e.g., a database). Ultrasound imaging system 150 also includes a mapping (e.g., a table) of anatomical features and / or indices of anatomical features to transmission rates and / or patient metrics (e.g., BMI) to transmission rates to determine the second transmission rate.

[0065]

[0073] As an illustrative example, in response to a determination that the anatomical feature being imaged is relatively dense compared to other anatomical features, such as is the case for muscle tissue, and / or a determination that the patient has a relatively low BMI (e.g., a low percentage of total lipids), the second transmission rate is determined to be relatively high.

[0066]

[0074] Further, in some embodiments, the second transmit speed is determined based on an analysis of ultrasound imaging data, such as data associated with received echoes associated with the ultrasound energy transmitted at the first speed (e.g., echoes received in step 504). For example, in some embodiments, ultrasound imaging system 150 identifies tissue aberrations (e.g., sound speed aberrations) in the image from the received echoes and / or based on data associated with the received echoes. Based on the identified aberrations, ultrasound imaging system 150 further determines whether to set the second transmit speed at a speed relatively higher or relatively lower than the first transmit speed and / or the speed adjustment from the first transmit speed. For example, ultrasound imaging system 150 determines a mapping of tissue aberrations in the image from the received echoes (e.g., for various points in the image) and determines the second speed of sound based on the mapping of tissue aberrations. An example of identifying tissue aberrations in an image is described in Provisional Application No. 62 / 838,365, filed April 25, 2019, entitled "SYNTHETIC TRANSMIT FOCUSING ULTRASOUND SYSTEM WITH SPEED OF SOUND MAPPING," the entire contents of which are incorporated herein by reference.

[0067]

[0075] Furthermore, analyzing the ultrasound imaging data to determine the second transmission speed may additionally or alternatively include comparing ultrasound imaging data corresponding to various transmission speeds. For example, the ultrasound imaging system 150 controls the transducer array 104 to transmit ultrasound energy at a set of various transmission speeds, including the first transmission speed (e.g., in step 502), and receives echoes corresponding to the set of various transmission speeds. In some cases, the ultrasound imaging system 150 generates a respective image for each of the set of various transmission speeds based on the echoes. The ultrasound imaging system 150 then identifies an image from the multiple images that has the highest image quality and / or a specific quality, such as the highest brightness, contrast, etc. In particular, the ultrasound imaging system 150 performs image processing, such as pixel-level image processing (e.g., evaluating whether there is a change in pixel color), to compare the images. In some embodiments, the ultrasound imaging system 150 determines the transmission speed corresponding to the identified image as the second transmission speed.

[0068]

[0076] At step 508, the method 500 includes generating multilines based on the received echoes (e.g., the echoes received at step 504). For example, the host 130 generates multilines in the multiline processors 110a-n based on the echoes received at the ultrasound probe 102. To do so, the multiline processors 110a-n apply delay and / or apodization weights to the received echoes (e.g., to electrical signals corresponding to the received echoes) to form differently steered receive beams (e.g., multilines) corresponding to the same transmitted ultrasound energy.

[0069]

[0077] At step 510, method 500 includes transmit focusing the multilines based on the second transmit rate. Specifically, host 130 adjusts the multilines corresponding to particular receive line positions using transmit focuser 132, as described below with reference to FIG. 6, and then combines the adjusted multilines. Furthermore, the multilines generated at step 508 are stored, before being transmit focused, at least until each multiline corresponding to a receive line position has been received, as described above with reference to FIG. 2. In some embodiments, for example, the multilines are stored in line store 112 before host 130 adjusts the multilines based on the second transmit rate.

[0070]

[0078] Referring now to FIG. 6 , a flow diagram of a method 600 for transmit focusing multiple lines based on a second transmit rate is shown, according to aspects of the present disclosure. In particular, step 510 of method 500 is performed according to one or more steps of method 600. As shown, method 600 has multiple enumerated steps, but embodiments of method 600 may have additional steps before, after, or between the enumerated steps. In some embodiments, one or more of the enumerated steps may be omitted, performed in a different order, or performed simultaneously. The steps of method 600 may be performed by any suitable component within ultrasound imaging system 150, and all steps need not be performed by the same component. In some embodiments, one or more steps of method 600 may be performed by or at the direction of a processor circuit (e.g., processor circuit 300 ( FIG. 3 )) of ultrasound imaging system 150, including transmit focus processor 134, image processor 122, or any other component.

[0071]

[0079] At step 602, method 600 includes determining transmit focus weights. In some embodiments, transmit focus processor 134 determines transmit focus weights based on Equation 1 and a simulation of the transmit field. For example, transmit focus processor 134 simulates a transmit field, and based on the simulation, transmit focus processor 134 determines amplitude values ​​(e.g., values ​​of the function amplitude(X,Z)) at various points within the simulated image field. As described above, with reference to Equation 1 and FIG. 2, transmit focus processor 134 uses the determined amplitude values ​​to determine transmit focus weights for multilines corresponding to points within the image field. In particular, transmit focus processor 134 determines transmit focus weights that weight the contribution of multilines relative to their respective proximity to the corresponding transmit beam. For example, transmit focus processor 134 determines a set of transmit focus weights that increase with increasing signal-to-noise ratio at the corresponding multilines (e.g., receive line positions in the simulation) based on the determined amplitude values.

[0072]

[0080] Further, in some embodiments, the transmit focus processor 134 determines transmit focus weights based on the second transmit speed. For example, the transmit focus processor 134 simulates a transmit field based in part on the second transmit speed. The simulated transmit field includes one or more parameters corresponding to characteristics used to transmit ultrasonic energy. These characteristics include, for example, the speed of sound used to transmit the transmit beam, the size and / or shape of the transmit aperture (e.g., the number and / or arrangement of transducer elements in the transducer array 104 used to transmit the transmit beam), the focal depth of the transmit beam, etc. Thus, to simulate a transmit field based on the second speed of sound, the transmit focus processor 134 is configured to set one or more parameters of the simulation based on the second speed of sound. Furthermore, based on the second transmit speed, the transmit focus processor 134 is configured to simulate a transmit field with characteristics that correspond to or differ from values ​​used to transmit ultrasonic energy (e.g., the first transmit speed).

[0073]

[0081] For example, if the second transmit speed is the same as the first transmit speed, the transmit focus processor 134 simulates a transmit field with ultrasonic energy transmitted at the second transmit speed. In such a case, the characteristics of the simulated transmit field correspond to the characteristics (e.g., the first transmit speed) used to transmit ultrasonic energy using the ultrasonic probe 102. As an illustrative example, if the first transmit speed and the second transmit speed are 1540 m / s, the transmit focus processor 134 determines the transmit focus weights based on the simulation of the transmit field corresponding to the transmit speed of 1540 m / s.

[0074]

[0082] On the other hand, if the second transmit speed is different from the first transmit speed, the transmit focus processor 134 is configured to adjust the speed of sound and / or focal depth of the simulated transmit field compared to the corresponding speed of sound and / or focal depth used when transmitting ultrasonic energy. As an illustrative example, if the first transmit speed is 1540 m / s and the second transmit speed is 1480 m / s, the transmit focus processor 134 is configured to simulate the transmit field with a transmit speed of 1480 m / s. In such a case, the simulated transmit field resembles plot 450 shown in FIG. 4B. Additionally or alternatively, the transmit focus processor 134 is configured to simulate the transmit field with a focal depth that is adjusted relative to the focal depth expected for transmitting ultrasonic energy at the first transmit speed. For example, differences in transmit speed result in changes in the focal depth for the transmit field, as shown by the difference between focal depth 402 corresponding to a transmit speed of 1540 m / s and focal depth 452 corresponding to a transmit speed of 1480 m / s (FIGS. 4A-4B). Thus, adjusting the focal depth of the simulated transmit field has a similar effect to simulating the transmit field with a second transmit speed. In some embodiments, transmit focus processor 134 identifies an adjusted focal depth for the simulated transmit field based on the second speed of sound. In some embodiments, for example, transmit focus processor 134 is configured with a mapping (e.g., a lookup table) of transmit speed and focal depth for the transmit field simulation. Thus, transmit focus processor 134 determines the focal depth for the transmit field simulation based on the second speed of sound and the mapping, and transmit focus processor 134 then simulates the transmit field based on the determined focal depth for the simulation.

[0075]

[0083] In either case, based on the simulation, transmit focus processor 134 determines the transmit focus weights. In some embodiments, the transmit focus weights are weights applied to the multilines in transmit focuser 132. Thus, transmit focus processor 134 configures weights 114a-n based on the determined transmit focus weights.

[0076]

[0084] At step 604, method 600 includes determining a transmit focus delay. In some embodiments, the transmit focus processor 134 determines the transmit focus delay based on Equation 2 and a simulated transmit field. For example, the transmit focus processor 134 simulates a transmit field, and based on the simulation, the transmit focus processor 134 determines propagation time (e.g., propagation delay) values ​​(e.g., values ​​of the function propagation_time(X, Z)) at various points within the simulated image field. As described above, with reference to Equation 2 and FIG. 2, the transmit focus processor 134 uses the determined propagation time values ​​to determine transmit focus weights for multilines corresponding to the points within the image field. In particular, the transmit focus processor 134 determines a transmit focus delay that equalizes phase shift variations present from line to line for multilines due to different transmit-receive beam position combinations. Thus, signal cancellation caused by phase differences of the combined multilines is minimized and / or avoided. For example, the transmit focus processor 134 determines the transmit focus delay based on the position of the multilines relative to the center of the corresponding transmit beam within the simulated transmit field.

[0077]

[0085] The transmit focus processor 134 further determines a transmit focus delay based on the second transmit rate. For example, as described above, the transmit focus processor 134 simulates a transmit field based in part on the second transmit rate. Thus, the transmit focus processor 134 simulates a transmit field with a second transmit rate that is the same as or different from the first transmit rate, and / or the transmit focus processor 134 simulates a transmit field with a focal depth that is adjusted relative to the focal depth expected for transmitting ultrasound energy at the first transmit rate. In either case, the transmit focus processor 134 determines a transmit focus delay based on the simulated transmit field. Furthermore, the transmit focus delay is a delay applied to the multi-line signal in the transmit focuser 132 (e.g., via delay lines 118a-n). Thus, the transmit focus processor 134 configures the transmit focuser 132 and / or delay lines 118a-n to apply the determined transmit focus delay.

[0078]

[0086] At step 606, method 600 includes adjusting the multilines based on the determined transmit focus weights and delays. As described above, transmit focus processor 134 configures transmit focuser 132 to apply the determined transmit focus weights and / or delays to the multilines. Thus, adjusting the multilines based on the determined transmit focus weights includes applying weights 114a-n, which are configured to the multilines in multipliers 116a-n based on the transmit focus weights. Furthermore, adjusting the multilines based on the determined transmit focus delays includes delaying the multilines in delay lines 118a-n by the transmit focus delays.

[0079]

[0087] In step 608, method 600 includes summing the adjusted multilines, i.e., combining the multilines adjusted in step 606. In some embodiments, transmit focuser 132 sums the multilines in summer 120, which receives as input the outputs of delay lines 118a-n. By summing the multilines, summer 120 generates transmit-focused image data having an extended depth of field. Summer 120 may be implemented by a summer circuit, as a digital summer, or as a combination thereof.

[0080]

[0088] Referring now to FIG. 5, at step 512, method 500 includes generating an image based on the transmit focused multilines. Specifically, image processor 122 receives the transmit focused multilines as input and generates an image based on the received transmit focused multilines. In some embodiments, the transmit focused multilines correspond to image data associated with lines in the image. Thus, image processor 122 receives sets of transmit focused multilines that respectively correspond to image data associated with various lines in the image (e.g., image data received along various receive lines) and combines the sets of transmit focused multilines to generate an image. Image processor 122 may further perform scan conversion or other processing to improve the generated image. As described above, with reference to step 510 and FIG. 6, transmit focusing the multilines includes adjusting the multilines based on a transmit focus delay. Thus, image processor 122 generates an image based on the multilines adjusted by the transmit focus delay.

[0081]

[0089] At step 514, method 500 includes outputting the image for display. More specifically, the image generated by image processor 122 is output to a display, such as display 124, included in host 130 or communicatively coupled to host 130 (e.g., via a wired or wireless interface).

[0082]

[0090] 7A-7C illustrate transmit beam patterns from retrospectively transmit-focused ultrasound image data (e.g., transmit-focused multiline). In FIGS. 7A-7C, the horizontal axis represents azimuth in any arbitrary units, and the vertical axis represents depth in any arbitrary units. In the embodiment illustrated in FIGS. 7A-7C, each of the transmit beam patterns is determined for ultrasound transmission through a medium in which ultrasound energy propagates at a speed of 1480 m / s. As such, the illustrated transmit beam patterns correspond to beam patterns from retrospectively transmit-focusing the transmit beam patterns illustrated in FIGS. 4A-4B according to techniques described herein (e.g., according to one or more steps of method 500 of FIG. 5 and / or method 600 of FIG. 6).

[0083]

[0091] 7A illustrates a transmit beam plot 700 corresponding to a first ultrasound transmit transmitted by the transducer array 104 at a transmit speed of 1480 m / s. The plot 700 also corresponds to ultrasound imaging data associated with the first ultrasound transmit (e.g., multilines generated based on the first ultrasound transmit) that is retroactively transmit focused based on the transmit speed of 1480 m / s. Thus, the plot 700 illustrates a transmit beam pattern corresponding to the transmit beam pattern in the plot 450 of FIG. 4B after the retroactive transmit focusing. That is, for example, the plot 700 illustrates an adjustment using transmit focus weights and / or delays of the multilines and / or received echoes associated with the ultrasound transmit transmitted in the transmit beam pattern of the plot 450.

[0084]

[0092] 7B shows a transmit beam plot 720 corresponding to a second ultrasound transmit transmitted by the transducer array at a transmit velocity of 1540 m / s. Plot 720 also corresponds to ultrasound imaging data associated with the second ultrasound transmit (e.g., multilines generated based on the second ultrasound transmit) that is transmit focused based on the transmit velocity of 1540 m / s. Thus, plot 720 shows a transmit beam pattern corresponding to the transmit beam pattern in plot 400 of FIG. 4A after retroactive transmit focusing. Thus, plot 720 is due to adjustment of the multilines and / or received echoes associated with the ultrasound transmit transmitted with the transmit beam pattern of plot 400 using transmit focus weights and / or delays.

[0085]

[0093] Compared to the transmitted beam pattern shown in plot 450, the retroactively transmit focused beam pattern shown in plot 700 exhibits an expanded depth of field (e.g., expanded focus). For example, the retroactively transmit focused beam pattern shown in plot 700 has a narrower profile than the transmitted beam pattern shown in plot 450. Similarly, compared to the transmitted beam pattern shown in plot 400, the retroactively transmit focused beam pattern shown in plot 720 exhibits an expanded depth of field. However, compared to the beam pattern of plot 700, the beam pattern of plot 720 has a wider profile, which may result in reduced image resolution and / or increased blur in an image generated based on the beam pattern of plot 720 compared to an image generated based on the beam pattern of plot 700. The difference between plot 700 and plot 720 is due to the effect of the difference in speed between the transmit velocity used in transducer array 104 (e.g., 1540 m / s in this example) and the transmit velocity at which the ultrasound energy propagates in the medium when generating the beam pattern of plot 720 (e.g., 1480 m / s in this example). In other words, the beam pattern of plot 720 is distorted by tissue aberrations compared to the beam pattern of plot 700.

[0086]

[0094] FIG. 7C shows a transmit beam plot 740 corresponding to a third ultrasound transmission transmitted by the transducer array at a transmit velocity of 1540 m / s. Plot 740 also corresponds to ultrasound imaging data associated with the third ultrasound transmission (e.g., multilines generated based on the third ultrasound transmission) that is transmit focused based on a transmit velocity of 1480 m / s. Thus, like plot 720, plot 740 shows a transmit beam pattern corresponding to the transmit beam pattern in plot 400 of FIG. 4A after retroactive transmit focusing. However, while plot 720 is obtained by transmit focusing image data corresponding to the beam pattern of plot 400 based on a transmit velocity of 1540 m / s, plot 740 is obtained by transmit focusing image data corresponding to the beam pattern of plot 400 based on a transmit velocity of 1480 m / s. In further comparison to plot 720, the beam pattern shown in plot 740 maintains a relatively narrow beam profile. Thus, an image generated based on the beam pattern of plot 740 appears less blurry (e.g., sharper) and has relatively higher resolution than an image generated based on the beam pattern of plot 720. In fact, the beam pattern shown in plot 740 appears substantially similar to the beam pattern shown in plot 700. Thus, an image generated based on the beam pattern of plot 740 resembles an image generated based on the beam pattern of plot 700. In this manner, plot 740 illustrates that the difference in velocity between the velocity used in transducer array 104 (e.g., 1540 m / s in this example) and the transmit velocity at which ultrasound energy propagates in the medium (e.g., 1480 m / s in this example) is taken into account (e.g., the effect of the difference is minimized) by retroactive transmit focusing in accordance with the techniques described herein.

[0087]

[0095] FIG. 8 shows a plot 800 comparing point spread functions (802, 804, and 806) at focal depth for different ultrasound imaging and transmit focusing techniques, as also described above with reference to FIGS. 7A-7C. Specifically, plot 800 includes a comparison of focal quality between techniques, with a wider spread of values ​​across the horizontal axis representing relatively poor focal quality and a narrower spread of values ​​across the horizontal axis representing relatively high focal quality. In the illustrated embodiment, each of the point spread functions (802, 804, and 806) is determined for ultrasound transmission through a medium in which ultrasound energy propagates at a velocity of 1480 m / s. In FIG. 8, the horizontal axis represents distance in some arbitrary units, and the vertical axis represents intensity in some arbitrary units.

[0088]

[0096] The first point spread function 802 corresponds to the point spread function in a first image generated based on a first ultrasound transmission having a transmission speed of 1480 m / s. More specifically, the first point spread function 802 corresponds to the point spread function from an image generated based on transmit focusing of ultrasound data associated with the first ultrasound transmission based on the transmission speed of 1480 m / s. Thus, the first point spread function 802 is associated with an image generated based on the transmit beampattern shown in plot 700 of FIG. 7A.

[0089]

[0097] The second point spread function 804 corresponds to the point spread function in a second image generated based on a second ultrasound transmission having a transmission speed of 1540 m / s. Specifically, the second point spread function 804 corresponds to the point spread function from an image generated based on transmit focusing of ultrasound data associated with the second ultrasound transmission based on a transmission speed of 1540 m / s. Thus, the second point spread function 804 is associated with an image generated based on the beam pattern shown in plot 720 of FIG. 7B.

[0090]

[0098] The third point spread function 806 corresponds to a point spread function in a third image generated based on a third ultrasound transmission having a transmission speed of 1540 m / s. However, in comparison to the second point spread function 804, the third point spread function 806 corresponds to a third image generated based on transmit focusing of ultrasound data associated with the third ultrasound transmission based on a transmission speed of 1480 m / s. That is, for example, the third point spread function 806 corresponds to an image generated based on the beam pattern shown in plot 740 of FIG. 7C .

[0091]

[0099] As shown, each of the first point spread function 802 and the third point spread function 806 are relatively similar, while the second point spread function 804 has a relatively broader profile than both the first point spread function 802 and the third point spread function 806. As such, plot 800 further illustrates that for a given point in the corresponding images, the first image and the third image (e.g., corresponding to the first point spread function 802 and the third point spread function 806, respectively) are less blurred and more resolved than the second image (e.g., corresponding to the second point spread function 804). In other words, plot 800 further illustrates that the difference in speed between the transmit velocity used in the transducer array 104 (e.g., 1540 m / s in this example) and the transmit velocity at which ultrasound energy propagates in the medium (e.g., 1480 m / s in this example) is taken into account (e.g., the effect of the difference is minimized) by retroactive transmit focusing in accordance with the techniques described herein.

[0092]

[0100] 9A-9B show ultrasound images of breast tissue with ultrasound energy propagating at a velocity of approximately 1480 m / s. In FIGS. 9A-9B, the horizontal axis represents azimuth in any arbitrary units, and the vertical axis represents depth in any arbitrary units. FIG. 9A shows ultrasound image 900 generated based on transmitting ultrasound energy (e.g., from transducer array 104) at a transmit velocity of 1540 m / s and transmit focusing of ultrasound data (e.g., multi-line) associated with the ultrasound energy based on the transmit velocity of 1540 m / s. FIG. 9B shows ultrasound image 950 generated based on transmitting ultrasound energy (e.g., from transducer array 104) at a transmit velocity of 1540 m / s and transmit focusing of ultrasound data (e.g., multi-line) associated with the ultrasound energy based on the transmit velocity of 1480 m / s. As shown, the image quality of ultrasound image 950 is superior to that of ultrasound image 900 in terms of resolution and / or clarity. 9A-9B therefore further illustrate the advantages of the techniques described herein.

[0093]

[0101] Those skilled in the art will appreciate that the above-described devices, systems, and methods can be modified in various ways. Accordingly, those skilled in the art will appreciate that the embodiments encompassed by the present disclosure are not limited to the specific exemplary embodiments described above. In that regard, while exemplary embodiments have been shown and described, a wide range of modifications, changes, and substitutions are contemplated in the foregoing disclosure. It will be understood that such variations can be made to the foregoing without departing from the scope of the present disclosure. Accordingly, it is appropriate that the appended claims be construed broadly and consistently with the present disclosure.

Claims

1. an array of acoustic elements that transmit ultrasonic energy at a first transmit rate and receive echoes associated with the ultrasonic energy transmitted at the first transmit rate; a processor circuit, The processor circuitry includes: in communication with the array of acoustic elements; generating a plurality of multilines based on the received echoes; determining a second transmission rate; determining a set of transmit focus delays based on the second transmit rate; adjusting the plurality of multilines using the set of transmit focus delays; generating an image based on the adjusted plurality of multilines; outputting the generated image to a display in communication with the processor circuit; Ultrasound imaging system.

2. 2. The ultrasound imaging system of claim 1, further comprising a plurality of delay lines in communication with the array of acoustic elements and the processor circuit, the processor circuit further controlling the plurality of delay lines to delay the plurality of multilines according to the set of transmit focus delays to adjust the plurality of multilines.

3. The processor circuitry further comprises: determining a set of transmit focus weights based on the second transmit rate; The ultrasound imaging system of claim 1 , wherein the set of transmit focus weights is used to adjust the plurality of multilines.

4. 4. The ultrasound imaging system of claim 3, further comprising a multiplier in communication with the array of acoustic elements and the processor circuit, the processor circuit further controlling the multiplier to apply the set of transmit focus weights to the plurality of multilines to adjust the plurality of multilines.

5. 2. The ultrasound imaging system of claim 1, further comprising a summer in communication with the processor circuit and the array of acoustic elements, the summer summing the adjusted multilines to generate transmit-focused image data, and the processor circuit generating the image further based on the transmit-focused image data.

6. The ultrasound imaging system of claim 1 , wherein the processor circuit determines the set of transmit focus delays further based on a model of ultrasound energy transmitted at the second transmit rate.

7. 2. The ultrasound imaging system of claim 1, wherein the array of acoustic elements transmits the ultrasound energy at a first focal depth, and the processor circuit determines the set of transmit focus delays further based on a model of ultrasound energy transmitted at a second focal depth.

8. The ultrasound imaging system of claim 7 , wherein the processor circuitry further determines the second focal depth based on the second transmission speed.

9. The ultrasound imaging system of claim 1 , wherein the ultrasound energy comprises multiple ultrasound beams, and the array of acoustic elements transmits each of the multiple ultrasound beams from a respective transmit beam position.

10. The ultrasound imaging system of claim 9 , wherein the plurality of multilines correspond to imaging data associated with receive line positions, and the echoes are received along the receive line positions for each of the plurality of ultrasound beams.

11. The ultrasound imaging system of claim 1 , wherein the processor circuit determines the second transmit rate based on user input.

12. The ultrasound imaging system of claim 11 , wherein the user input comprises a selection of the second transmit rate from among a set of predetermined transmit rates.

13. 2. The ultrasound imaging system of claim 1, wherein the processor circuit generates the image further based on an additional adjusted plurality of multilines, the adjusted plurality of multilines corresponding to a first line of the image, and the additional adjusted plurality of multilines corresponding to a second line of the image.

14. The ultrasound imaging system of claim 1 further comprising the display.

15. 1. A method for retrospectively transmit focusing ultrasound data for ultrasound imaging, comprising: controlling, by a processor circuit, an array of acoustic elements in communication with the processor circuit to transmit ultrasonic energy at a first transmission rate and to receive echoes associated with the transmitted ultrasonic energy; generating, by the processor circuit, a plurality of multilines based on the received echoes; determining a second transmission rate by the processor circuit; determining, by the processor circuit, a set of transmit focus delays based on the second transmit rate; adjusting, by the processor circuit, the plurality of multilines using the set of transmit focus delays; generating, by the processor circuit, an image based on the adjusted plurality of multilines; outputting the generated image by the processor circuitry to a display in communication with the processor circuitry; A method comprising:

Images