Method and apparatus for generating shear waves

Abstract

The present disclosure describes ultrasound systems and methods configured to interrogate the stiffness and / or elasticity of a target tissue through shear wave imaging. The systems can be configured to transmit multiple push pulses at different focal depths in the target tissue in a strobe-like fashion. The rapidly transmitted push pulses can generate constructive interference to form shear waves of a composite shear wave. An example system can include a beamformer configured to transmit parameters of a push pulse to a transducer array while receiving new parameters of a push pulse from a controller. The dual transmission and reception of parameters of different push pulses reconfigures the beamformer without interrupting push pulse transmission, thereby minimizing the delay between successive push pulses. The push pulses transmitted according to the disclosed methods can generate a composite shear wave configured to interrogate the tissue with enhanced sensitivity over a wide range of depths.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to ultrasound systems and methods for determining tissue properties using shear waves. Particular implementations involve rapidly applying a series of ultrasound push pulses successively into a target tissue to generate a complex shear wave through the target tissue. BACKGROUND

[0002] One of the long-term goals of diagnostic imaging is accurate tissue characterization. Clinicians desire to use imaging systems such as ultrasound to identify characteristics of target tissue contained in images of the target tissue, e.g., benign vs. malignant. One technique for deriving tissue characteristics is ultrasound elastography, which measures the elasticity and / or stiffness of tissue in the body. For example, a breast tumor or mass that is stiff can be malignant, while a softer and more compliant mass can be benign. In particular, ultrasound shear wave elastography can determine the local stiffness level of various tissues by transmitting a "push pulse" from a transducer into the tissue to generate a shear wave that propagates laterally through the tissue. A tracking pulse emitted by the transducer can then be used to measure the speed of the shear wave as it propagates, which is generally proportional to the stiffness of the tissue. For example, assuming the same push pulse is used to generate a shear wave in each tissue type, the shear wave speed is generally slower in soft tissue than in stiff tissue.

[0003] Existing ultrasound elastography systems can transmit one or more push pulses at a shallow depth within a target tissue over a period of time, then move the focal zone deeper to generate a shear wave that tends to transmit outward and slightly downward. Thus, to generate a comprehensive tissue scan using multiple depths of focal zones, the focal point must be repeatedly adjusted, which can reduce the effectiveness of the overall push (and resulting shear wave) by accumulating significant transition time between each discrete pulse. SUMMARY

[0004] The present disclosure describes ultrasound systems and methods for determining the elasticity and / or stiffness of a target tissue via shear wave imaging. Embodiments can involve rapidly flashing a plurality of push pulses into the target tissue, each push pulse having a different focal depth. Shear waves generated by the rapidly transmitted push pulses can constructively interfere to form a composite shear wave having an approximately planar wave front for insonifying a region of interest with high sensitivity. The rapid flashing of push pulses having different waveform parameters can be performed with a transmit beamformer configured to receive the parameters of a new push pulse without interrupting the ongoing transmission of a current push pulse. Receiving the parameters of a new push pulse during the transmission of the parameters of a current push pulse can be implemented using dual sets of shadow and active registers on the beamformer, respectively. A start signal received from a beamformer controller can initiate a transition between the implementation of the parameters of a current push pulse and the parameters of a next set of push pulses with little to no interruption, such that the composite shear wave generated by the successive pulses smoothly spans the entire target tissue. In some examples, the composite shear wave can have an approximately cylindrical shape over the depth and lateral distance within the tissue. Various push pulse schemes can be implemented according to the embodiments herein, e.g., in the direction of a user and / or automatically according to user preferences and / or tissue dimensions. Each push pulse scheme can include various numbers of push pulses and parameters of the push pulses, enabling customized insonification of a wide range of tissue types and specific regions of interest.

[0005] According to the principles of the present disclosure, an ultrasound imaging system for shear wave imaging can include an ultrasound transducer configured to acquire echoes in response to ultrasound pulses transmitted toward a target tissue. The system can also include a beamformer configured to transmit, from the ultrasound transducer, a current push pulse having a current focal depth according to parameters of the current push pulse to generate a current shear wave. The beamformer can also receive parameters of a next push pulse for transmitting a next push pulse having a next focal depth different from the current focal depth to generate, using a controller circuit, a next shear wave. The current shear wave and the next shear wave can constructively interfere to generate a composite shear wave in the target tissue.

[0006] In some examples, the composite shear wave includes an approximately columnar shape defined in part by a combined depth of a current push pulse and a next push pulse. In some embodiments, the beamformer is configured to transition from the current push pulse to the next push pulse in about 250 ns to about 550 ns. In some examples, the beamformer is configured to transition from the current push pulse to the next push pulse about every 8 ps to about 16 ps. In some embodiments, the beamformer includes one or more active registers and one or more shadow registers configured to transmit parameters of a current push pulse to the ultrasound transducer and receive parameters of a next push pulse from the controller circuit, respectively. In some examples, the beamformer is configured to reduce a transmission delay between the current push pulse and the next push pulse. In some embodiments, the beamformer is configured to repeat the current push pulse until parameters of the next push pulse are used to transmit the next push pulse.

[0007] In some examples, the controller circuit is configured to implement a push pulse scheme according to a user command. The push pulse scheme can include a sequence of push pulses each having a different focal depth. In some embodiments, the system can further include a user interface configured to display the push pulse scheme.

[0008] In some examples, the beamformer is further configured to transmit a tracking pulse from the ultrasound transducer spatially arranged to intersect the composite shear wave at one or more locations within the target tissue. In some embodiments, the beamformer is further configured to receive echo signals from the ultrasound transducer indicative of locations at which the tracking pulse intersects the composite shear wave. In some examples, the system further includes a tissue analysis circuit configured to determine an elasticity of the target tissue based on the echo signals.

[0009] According to principles of the present disclosure, a method of shear wave imaging can include acquiring ultrasound echoes in response to an ultrasound pulse transmitted toward a target tissue, transmitting a current push pulse having a current focal depth to generate a current shear wave according to parameters of the current push pulse, and receiving parameters of a next push pulse for transmitting a next push pulse having a next focal depth different from the current focal depth to generate a next shear wave while transmitting the current push pulse. The current shear wave and the next shear wave can constructively interfere to generate a composite shear wave in the target tissue.

[0010] In some examples, the composite shear wave includes an approximately columnar shape defined in part by a combined depth of the current push pulse and the next push pulse. Some embodiments can also include transitioning from the current push pulse to the next push pulse approximately every 8 μβ to approximately 16 μβ. Some examples can also include reducing a transmission delay between the current push pulse and the next push pulse. Some embodiments can also include repeating parameters of the current push pulse until the next push pulse. Some examples can also include transmitting a tracking pulse arranged in space to intersect the composite shear wave at one or more locations within the target tissue.

[0011] Any of the methods described herein, or steps thereof, can be embodied in a non-transitory computer-readable medium comprising executable instructions that, when executed, can cause a processor circuit of a medical imaging system to perform the methods or steps embodied herein. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 is a block diagram of an ultrasound imaging system constructed in accordance with the principles of the present disclosure.

[0013] Figure 2 is a diagram of a transmit beamformer constructed in accordance with the principles of the present disclosure.

[0014] Figure 3 is a diagram of a composite shear wave generated in accordance with the principles of the present disclosure.

[0015] Figure 4 is a diagram of another composite shear wave generated in accordance with the principles of the present disclosure.

[0016] Figure 5 is a flowchart illustrating a method performed in accordance with the principles of the present disclosure.

[0017] Figure 6 is a schematic diagram of a processor circuit in accordance with the principles of the present disclosure. DETAILED DESCRIPTION

[0018] The following description of certain embodiments of the present system and method is merely exemplary in nature and is in no way intended to limit the application or its applications or uses. In the following detailed description of embodiments of the present system and method, numerous specific details are set forth in order to provide a thorough understanding of the described system and method. However, there can be cases in which details are not described in order not to obscure the present system and method. Further, in the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present system and method. However, there can be cases in which well-known structures are not described in order not to obscure the present system and method. The present system and method are solely directed at teaching inventive concepts, and it is intended that equivalents, modifications, and improvements of the present system and method not specifically recited are fully encompassed by the claims and their equivalents.

[0019] Provided herein are ultrasound-based imaging systems configured to improve shear wave elastography by employing a transmit beamformer configured to generate a smooth shear wave that traverses a wide depth, effectively generating a shear wave in the form of a plane wave or a converging wave originating from multiple focal planes along the depth. The disclosed systems are configured to quickly download new push pulse parameters (e.g., focusing and waveform coefficients) to the beamformer without interrupting current push pulse transmission, thereby reconfiguring the beamformer at the time of beamformer transmission. The parameters of various push pulses can be adjusted according to different push pulse schemes. The parameters of the push pulses can include one or more characteristics of each discrete push pulse, or a relationship between push pulses transmitted according to a given push pulse scheme. For example, the frequency of each push pulse, a waveform coefficient associated with each push pulse, a transition time between successive push pulses, a transition time between sequences of two or more push pulses, a length of time for a particular push pulse repetition, an order of successive push pulses and / or a focal depth, and / or an amplitude that can vary for each push pulse.

[0020] Figure 1 An example ultrasound system 100 is shown that is configured to perform shear wave imaging within tissue of interest by rapidly transmitting multiple push pulses having different focal depths. The system 100 can include an ultrasound acquisition circuit 110. The ultrasound acquisition circuit 110 can include an ultrasound probe 112, a transmit beamformer 126, a multi-line receive beamformer 128, a transmit / receive (T / R) switch 130, a beamformer controller circuit 132, and a signal processor circuit 136. The ultrasound acquisition circuit 110 can be constructed from hardware or a combination of hardware and software.

[0021] The ultrasound probe 112 can house an ultrasound sensor array 114. The ultrasound sensor array 114 can be configured to transmit and receive ultrasound signals. The ultrasound sensor array 114 can be configured to transmit push pulses 116 into a target region 118 in a flash-like manner. The target region 118 can be a portion of a living being, such as a human or animal. The living being can be alive or dead. The target region 118 can contain one or more tissue abnormalities 120, such as a tumor or a stiff tissue inclusion. The target region 118 can include an organ, including but not limited to a human liver, pancreas, kidney, lung, heart, or brain, or a tissue region, such as muscle tissue.

[0022] The push pulses 116 can be arranged to collectively form a composite shear wave 119. The composite shear wave can be created using a plurality of in-phase interfering shear waves that propagate through the target region 118. In additional or alternative embodiments, the push pulses 116 can be generated by other arrays than the single ultrasound sensor array 114. For example, in some examples, one array can be used to apply the push pulses and a different array can be used to image the resulting composite shear wave.

[0023] The ultrasound sensor array 114 can also be configured to transmit a plurality of tracking pulses or beams 124 into the target region 118 to detect propagation of the shear wave 119 created by the push pulses 116. The tracking pulses 124 can be transmitted adjacent to the push pulses 116, and in some examples can be laterally spaced apart relative to the push pulses. In some embodiments, such as when a linear probe is utilized to transmit the tracking pulses, the tracking pulses 124 can be parallel to the push pulses 116. In other examples, the tracking pulses 124 can not be transmitted parallel to the push pulses 116. For example, a curved probe can transmit the tracking pulses 124 at an angle apart in a radial direction. Such pulses can not be parallel in Cartesian space, but are transmitted in the same direction in polar or cylindrical coordinate systems.

[0024] The ultrasound sensor array 114 can be coupled to a transmit beamformer 126 and a multiline receive beamformer 128 via a transmit / receive (T / R) switch 130. A beamformer controller circuit 126 can control coordination of transmission and reception by the beamformers 126, 128. In operation, the transmit beamformer 126 can control the ultrasound sensor array 114 to transmit a series of push pulses 116 into the target region 118 rapidly in succession, e.g., strobed, in the direction of the beamformer controller circuit 132. The transmit beamformer 126 can be configured to receive parameters for a new push pulse for a subsequent push pulse without interrupting the current push pulse transmission, thereby minimizing the transition time between successive pulses and generating a composite shear wave 119. The multiline receive beamformer 128 can produce spatially distinct receive lines (A-lines) of echo signals 134, which can be received by the ultrasound sensor array 114 and can be filtered, de-noised, etc. by a signal processor circuit 136. In some embodiments, components of the acquisition circuit 110 can be configured to generate a plurality of ultrasound image frames 138 from the ultrasound echoes 134.

[0025] The system 100 can also include one or more processor circuits, such as a tissue analysis circuit 140, which can be configured to determine one or more properties of tissue within the target region 118, such as stiffness and / or elasticity, based on the ultrasound image frames 138. The tissue analysis circuit 140 can be made of hardware, software, or a combination of hardware and software.

[0026] In at least one embodiment, the system 100 also includes a display processor circuit 142 coupled with the tissue analysis circuit 140 and a user interface 144. The display processor circuit 142 can be configured to generate ultrasound images 146 and a tissue map 148 of local stiffness values and / or gradients. The display processor circuit 142 can be configured to generate the ultrasound images 146 and / or the tissue map 148 from the image frames 138.

[0027] The user interface 144 can be configured to display the ultrasound images 146 and the tissue map 148 in real-time while performing an ultrasound scan. The user interface 144 can receive user inputs 150 at any time before, during, or after such a procedure. In some examples, the user interface 144 can be a touchscreen configured to receive user inputs 150 while displaying the ultrasound images 146 and / or the tissue map 148. In some examples, the ultrasound images 146 and / or the tissue map 148 displayed on the user interface 144 can be updated at each acquisition frame received and processed by the data acquisition circuit 110 during an ultrasound scan. In embodiments, the user interface 144 operating in conjunction with the display processor circuit 142 can be configured to generate and display a push pulse scheme 152.

[0028] The push pulse scheme 152 can include a series of push pulses applied by the transmit beamformer 126, showing a focal depth of each push pulse, an order of the transmit pulses, and / or a transition time between each successive pulse. The push pulse scheme 152 can include parameters, such as frequency and wavelength, of one or more push pulses per pulse. In some examples, the push pulse scheme 152 can include an estimated shape of the composite shear wave 119 generated by the push pulse sequence.

[0029] Figure 1 The configuration of the system 100 shown in FIG. 1 can vary. For example, the system 100 can be portable or fixed. In some embodiments, various portable devices, such as a laptop computer, a tablet, a smartphone, etc., can be used to implement one or more functions of the system 100. In examples incorporating a portable device, the ultrasound sensor array 114 can be connectable via a USB interface. In some embodiments, Figure 1 One or more components shown in FIG. 1 can be combined into a single element.

[0030] In some embodiments, the tissue analysis circuit 140 can be incorporated within the data acquisition circuit 110 along with the display processor circuit 142.

[0031] Figure 2 is a diagram of the operation of a transmit beamformer 200 according to embodiments of the present disclosure. The transmit beamformer 200 can include a duplexed set of a shadow register 202 and an active register 204. The shadow register 202 and the active register 204 are configured to receive and transmit, respectively, different parameters of push pulses simultaneously via double buffering.

[0032] In operation, the shadow register 202 can store new or next push pulse parameters 206 from a beamformer controller circuit 208. At the same time, the active register 204 can continue to transmit current push pulse parameters 210 to an ultrasound transducer 212. The ultrasound transducer 212 can include an ultrasound sensor array 214. The ultrasound transducer 212 can transmit a push pulse to a target tissue according to such parameters. The new push pulse parameters 206 and the current push pulse parameters 210 can specify push pulses having different focal depths. For example, the current push pulse parameters 210 can specify a push pulse having a shallower focal depth within the target tissue than a push pulse embodied in the new push pulse parameters 206, or vice versa. The beamformer controller circuit 208 can then instruct the transmit beamformer 200 to switch to a new focal zone for a next push pulse transmission, at which time the new push pulse parameters 206 can be transferred from the shadow register 202 to the active register 204 and the new waveform begins to be transmitted via the transducer 212.

[0033] To avoid transmission delays between different elements of the ultrasound sensor array 214, a Fresnel focusing approximation can be applied, which can involve limiting all transmission delays to a single waveform cycle, such that a transmit waveform can complete one focusing configuration and begin another configuration within about one acoustic cycle. For example, the transmission delays of each transmit channel can be decremented until they reach zero, at which point the parameters 206 of a new push pulse that can be stored in the shadow register 202 can be driven to the ultrasound transducers 212 for simultaneous transmission.

[0034] In embodiments, the beamformer controller circuit 208 can be configured to repeat or cycle the logic applied to generate the parameters 210 of the current push pulse, such that a particular push pulse can be repeated ad infinitum, or at least for a defined period of time, e.g., until the beamformer controller circuit 208 instructs the beamformer 200 to transition to a next push pulse according to the parameters of the next set of push pulses. Thus, once a push pulse transmission begins, the transmission can continue autonomously as the beamformer 200 receives the parameters of new push pulses. In some examples, the beamformer controller circuit 208 can be configured to repeat or cycle the logic applied to generate a series of push pulses, e.g., according to a push pulse scheme, such that a composite shear wave generated from the series of push pulses can be generated repeatedly.

[0035] According to particular embodiments, configuring the transmit beamformer 200 with new push pulse parameters 206 can take between 5 μβ to about 10 μβ, or any variation therebetween, e.g., 7, 8, 8.7, 9 μβ. Beamformer configuration time can vary. For example, if one or more push pulse parameters remain the same between successive pulses, the configuration time can be less than that required using a completely new set of push pulse parameters. Periodic reconfiguration of the transmit beamformer 200 can occur stroboscopically, e.g., about once every 9 μβ, or as needed in larger increments, e.g., every 10, 11, 12, 13, 14, 15, 16, 17, 20 μβ or more, or any increment therebetween. The transition time between each successive push pulse can also vary, and can be less than a single wave cycle, e.g., about 300 ns, or about 400 ns, 500 ns, 600 ns, 700 ns, 800 ns, 900 ns, or any length of time therebetween. When transitioning from the parameters of a current set of push pulses, the signals embodying the new push pulse parameters 206 can be driven to the ultrasound transducers 212 at a low frequency for one or more cycles.

[0036] By rapidly reconfiguring the beamformer 200, multiple push pulses each defined by a different focal depth (and / or e.g. frequency) can be smoothly emitted with very short transition times between them and then released simultaneously. The rapid emission of the pulses can improve the fidelity of the resulting shear waves and can generate new shear wave shapes with enhanced sensitivity and penetration. Figure 3 A series of push pulses rapidly emitted in succession is shown in accordance with some embodiments described herein. The series of push pulses can collectively form a composite, quasi-planar or planar shear wave of approximately cylindrical or columnar shape due to constructive interference between the discrete shear waves generated by each push pulse. This columnar shear wave marks an improvement over existing Mach cone shear waves, which include multiple spherical shear waves that do not propagate together to form a column.

[0037] Figure 3 is a diagram of a composite shear wave 300 generated in accordance with the principles of the present disclosure. The composite shear wave 300 is formed from a plurality of push pulses 302 emitted rapidly in succession from a plurality of elements 304. The elements 304 can form an ultrasound sensor array 314 on or within an ultrasound transducer 312. The composite shear wave 300 propagates radially outward through an imaging plane 308, e.g. in the direction of propagation indicated by arrows 316 and 318. Because the push pulses 302 are emitted rapidly in succession to different depths and then released simultaneously, constructive interference between each adjacent wave can produce the composite shear wave 300 defined by an approximately columnar or cylindrical shape, Figure 3 is shown in two parts (the composite shear wave 300 does not cover the focal points of the push pulses 302 for illustrative purposes only. The composite shear wave 300 propagates radially outward from the focal points of the push pulses 302). In embodiments, each push pulse 302 can be emitted from a plurality of elements 304. The push pulses 302 can be emitted one after another in succession with very short times between the emission of each push pulse.

[0038] This particular example illustrates fifteen push pulses 302; however, the number of push pulses can vary depending on the tissue being imaged, user preference, frequency, etc., such that the number of push pulses used to generate a particular composite shear wave can range from 2 to 20 or more. In the illustrated embodiment, a push pulse 302 with a deeper focal region (e.g., push pulse 1) is first emitted, followed by successively shallower focal regions, e.g., up to push pulse 5. The same deep-to-shallow sequence can then be rapidly repeated one or more times. In another example, a push pulse with the shallowest focal region can be emitted first, followed by successively deeper focal regions. The number of deep-to-shallow (or shallow-to-deep) sequences can vary depending on the number of push pulses emitted within each sequence. The lateral spacing between push pulses, e.g., the lateral spacing between push pulses 1, 6, and 11, is shown for illustrative purposes only. In operation, pulses emitted at the same focal depth may not be laterally separated. The composite shear wave 300 spans a tissue depth defined by multiple driving pulses, allowing the tissue elasticity and / or stiffness throughout the defined volume to be determined by tracking the pulses to probe the depth and lateral propagation of the composite shear wave 300.

[0039] In some embodiments, it can be similar to Figure 3 The push pulse scheme is displayed in the manner shown, illustrating the focal areas of multiple push pulses and the composite shear wave generated from them. Parameters of one or more additional push pulses, i.e., the parameters of the push pulses as described above, can be displayed simultaneously with the push pulse scheme. Users can adjust one or more parameters included in a given push pulse scheme. In some examples, users can input the desired tissue depth and / or region of interest to be probed by the composite shear wave, prompting the ultrasound system, such as beamformer controller circuitry, to automatically generate a push pulse scheme based on such instructions.

[0040] Figure 4 This is a diagram of a composite shear wave 400 generated according to the principles of this disclosure. The composite shear wave 400 is formed by a plurality of impinging pulses 402 rapidly emitted from a plurality of elements 404. The elements 404 may form an ultrasonic sensor array 414 above or within an ultrasonic transducer 412. The composite shear wave 400 propagates through an imaging plane 408 (shown by dashed lines) and propagates radially outward in a convex shape, for example in the propagation direction indicated by arrows 416 and 418. As shown, the composite shear wave 400 has an approximate hourglass shape formed by the constructive interference between the impinging pulses 402 (two portions of which are shown).

[0041] The composite shear wave 400 can be formed by rapidly and successively emitting push pulses with deep and shallow focal points (e.g., push pulses 1 and 2), and... Figure 3In contrast to the push pulse scheme shown in FIG. 4, the feature is successive push pulses arranged spatially from deep to shallow (or from shallow to deep). For example, the shallowest and deepest push pulses 402 can be transmitted first, followed by push pulses closer to the more medial depth. In the particular example shown, push pulses 1-6 are transmitted in rapid succession, alternating between deep and shallow focal points. The focal depth is adjusted rapidly to the region between the deepest and shallowest focal points, then push pulses 7-12 are transmitted there. The focal depth can be adjusted again, so that push pulses 13-15 are transmitted in rapid succession. The lateral separation between push pulses, such as between push pulses 1, 3, and 5, is shown for illustrative purposes only. In operation, pulses transmitted at the same focal depth can not be laterally separated. After the 6th push pulse is fired, the tissue targeted by push pulses 1-6 can begin to relax back to its normal state, at which time the shear waves generated by push pulses 1-6 can begin to propagate. After the 12th push pulse is fired, the tissue targeted by push pulses 7-12 can begin to relax back to its normal state, at which time the shear waves generated by push pulses 7-12 can begin to propagate. The shear waves generated by push pulses 13-15 can then begin to propagate after the 15th push pulse is transmitted. The resulting composite shear wave 400 from each constituent shear wave generation can thus form an approximate hourglass shape Figure 4

[0042] Near the center of array 404, individual elements can alternate between deep and shallow focal delays on every other element, for example, to avoid grating lobes. The outer regions of array 404 can transmit depth-focused pulses, for example, from every other element. In various embodiments, pulses with different frequencies can be transmitted from different elements of array 404, for example, so that shallow pulses can have a mid-frequency while deep pulses can have a lower frequency to penetrate more deeply into the target tissue.

[0043] By using a rapidly reconfigurable beamformer according to the disclosed embodiments to flash different push pulse sequences with different focal depths, composite shear waves with a variety of shapes can be generated. The time elapsed between successive pulses within a pulse sequence and / or the time elapsed between successive sequences can vary. For example, a composite shear wave with converging wavefronts can be generated by transmitting a set of alternating deep and shallow focal points, rapidly alternating between shallow and deep focal points every 9-15 ps in a first set, followed by a successive set of alternating deep and shallow focal points, for example, about 100 ns after the first set is transmitted. In embodiments, successive sets of alternating focal points can transition to be closer to the center of the region of interest, so that more deeply focused shear waves can enhance signals generated near the range of the previous set of focal points to be fired.

[0044] Figure 5 ​is a flowchart of a shear wave imaging method performed in accordance with the principles of the present disclosure. The example method 500 illustrates steps that can be utilized in any order by the systems and / or apparatuses described herein. The method 500 can be performed by an ultrasound imaging system, such as the system 100, or other suitable system, including, for example, a mobile system, such as the LUMIFY by Koninklijke Philips N.V. ("Philips"). Additional example systems can include the SPARQ and / or EPIQ, also produced by Philips.

[0045] In the illustrated embodiment, the method 500 begins at block 502 by "acquiring ultrasound echoes in response to ultrasound pulses emitted toward a target tissue."

[0046] At block 504, the method includes "emitting a current push pulse having a current focus depth in accordance with parameters of the current push pulse to generate a current shear wave."

[0047] At block 506, the method includes "receiving parameters of a next push pulse while the current push pulse is being emitted for emitting a next push pulse having a next focus depth different from the current focus depth to generate a next shear wave." In accordance with the claimed method, as further indicated in block 506, "the current shear wave and the next shear wave constructively interfere to generate a composite shear wave in the target tissue."

[0048] In implementing the various embodiments of components, systems, and / or methods using programmable devices, such as computer-based systems or programmable logic, it will be understood that the above-described systems and methods can be implemented using any of a variety of known or later-developed programming languages, such as, for example, "C", "C++", "FORTRAN", "Pascal", etc. Thus, a variety of storage media, such as magnetic computer disks, optical disks, electronic memory, etc., can be prepared containing information which can direct a device, such as a computer, to implement the above-described systems and / or methods. Once the appropriate device has access to the information and programming contained on the storage media, the storage media can supply the information and programming to the device, thereby enabling the device to perform the functions of the systems and / or methods described herein. For example, if a computer disk containing the appropriate material (e.g., source files, object files, executable files, etc.) is supplied to a computer, the computer can receive the information, configure itself appropriately, and perform the functions of the various systems and methods depicted in the above diagrams and flowcharts to implement the various functions. That is, the computer can receive various portions of the information relating to different elements of the above-described systems and / or methods from the disk, implement the individual systems and / or methods, and coordinate the functions of the individual systems and / or methods described above.

[0049] In view of the present disclosure, it should be noted that the various methods and devices described herein can be implemented in hardware, software, and firmware. Furthermore, the various methods and parameters are included by way of example only, and without any limiting nature. In view of the present disclosure, one of ordinary skill in the art can implement the present teachings with the desired equipment and techniques in mind, while still remaining within the scope of the present disclosure.

[0050] Figure 6 is a block diagram illustrating an example processor 600 according to embodiments of the present disclosure. The processor 600 can be used to implement one or more processors described herein, such as the beamformer controller circuit 132, the signal processor circuit 136, the tissue analysis circuit 140, and / or the display processor circuit 142 shown in FIG. 13. In some examples, the processor 600 can be used to implement or be part of one or more components described herein, such as the motion trigger generator 450, the ECG trigger generator 410, the scan converter 430, the multi-planar reformatter 432, and / or the volume Tenderer 434, the multi-line receive beamformer 128, the transmit / receive switch 130, and / or the tissue analysis section 140 shown in FIG. 13. The processor 600 can be any suitable processor type, including but not limited to a microprocessor, a microcontroller, a digital signal processor (DSP), a field-programmable array (FPGA) that has been programmed to form a processor, a graphics processing unit (GPU), an application-specific circuit (ASIC) that has been designed to form a processor, portions of custom integrated circuits, or combinations thereof. The functions of one or more of the processors described herein, including the processor 600, can be incorporated into a fewer number of or a single processing unit (e.g., a CPU) that can be programmed in response to executable instructions to carry out the functions described herein. Figure 1 Figure 1 The processor 600 can include one or more cores 602 (one shown). The core 602 can include one or more arithmetic logic units (ALUs) 604 (one shown). In some embodiments, the core 602 can include one or more floating point logic units (FPLUs) 606 (one shown) and / or one or more digital signal processing units (DPUs) 608 (one shown) in addition to or instead of the ALU 604.

[0051] The processor 600 can include one or more registers 612 communicatively coupled to the core 602. The registers 612 can be implemented using dedicated logic gate circuitry (e.g., flip-flops) and / or any suitable memory technology. In some embodiments, the registers 612 can be implemented using static memory. The registers can provide data, instructions, and addresses to the core 602.

[0052] The processor 600 can include one or more registers 612 communicatively coupled to the core 602. The registers 612 can be implemented using dedicated logic gate circuitry (e.g., flip-flops) and / or any suitable memory technology. In some embodiments, the registers 612 can be implemented using static memory. The registers can provide data, instructions, and addresses to the core 602. ​

[0053] In some embodiments, the processor 600 can include one or more levels of cache memory 610 communicatively coupled to the core 602. The cache memory 610 can provide computer-readable instructions to the core 602 for execution. The cache memory 610 can provide data for processing by the core 602. In some embodiments, the computer-readable instructions can be provided to the cache memory 610 from a local memory (e.g., a local memory attached to the external bus 616). The cache memory 610 can be implemented with any suitable cache memory type, such as a metal-oxide semiconductor (MOS) memory, such as a static random access memory (SRAM), a dynamic random access memory (DRAM), and / or any other suitable memory technology.

[0054] The processor 600 can include a controller 614 that can control input to the processor 600 from components included in other processors and / or systems (e.g., the transmit beamformer 200 shown in FIG. 1) and / or output from the processor 600 to other processors and / or components included in the system (e.g., the signal processor circuit 136 shown in FIG. 1). Figure 2 The controller 614 can control data paths in the ALU 604, the FPLU 606, and / or the DSPU 608. The controller 614 can be implemented as one or more state machines, data paths, and / or dedicated control logic. The gates of the controller 614 can be implemented as standalone gates, FPGAs, ASICs, or any other suitable technology. Figure 2 The registers 612 and the cache 610 can communicate with the controller 614 and the core 602 through internal connections 620A, 620B, 620C, and 620D. The internal connections can be implemented as buses, multiplexers, crossbars, and / or any other suitable connection technology.

[0055] The input and output of the processor 600 can be provided through a bus 616, which can include one or more conductors. The bus 616 can be communicatively coupled to one or more components of the processor 600, such as the controller 614, the cache 610, and / or the registers 612. The bus 616 can be coupled to one or more components of the system, such as the beamformer controller circuit 132, the signal processor circuit 136, the tissue analysis circuit 140, and / or the display processor circuit 142 mentioned earlier. The bus 616 can be implemented as a bus, a multiplexer, a crossbar, and / or any other suitable connection technology.

[0056]

[0057] ​The bus 616 can be coupled to one or more external memory. The external memory can include read only memory (ROM) 632. The ROM 632 can be a mask ROM, an electrically programmable read only memory (EPROM) 635, or any other suitable technology. The external memory can include random access memory (RAM) 633. The RAM 633 can be a static RAM, a battery backed-up static RAM, a DRAM, a SRAM, or any other suitable technology. The external memory can include an electrically erasable programmable read only memory (EEPROM) 635. The external memory can include a flash memory 634. The external memory can include a magnetic storage device, such as a disk 636. In some embodiments, the external memory can be included in a system, such as the ultrasound system 100 shown in FIG. 1. Figure 1

[0058] Aspects of the technology are also described herein with reference to block and / or flow diagrams of methods, apparatus (systems) and / or computer program products according to embodiments of the present embodiments. It is to be understood that the blocks of the block diagrams and / or flow diagrams, and combinations of blocks in the block diagrams and / or flow diagrams, can be implemented by computer executable instructions. These computer executable instructions can be provided to a processor circuit of a general purpose computer, special purpose computer, controller circuit, or control unit, and / or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor circuit of the computer and / or other programmable data processing apparatus, create means for implementing the functions / acts specified in the block diagram and / or flow diagram block or blocks.

[0059] While the present system can have been described with particular reference to an ultrasound imaging system, it is also contemplated that the present system can be extended to other medical imaging systems that obtain one or more images in a systematic manner. Thus, the present system can be used to obtain and / or record image information related to the kidneys, testicles, breasts, ovaries, uterus, thyroid, liver, lungs, musculoskeletal, spleen, heart, arteries and vascular system, as well as other imaging applications related to ultrasound guided interventions, but not limited thereto. Furthermore, the present system can also include one or more programs that can be used with conventional imaging systems, such that they can provide the features and advantages of the present system. Certain other advantages and features of the present disclosure can be readily appreciated as the same becomes better understood by the reader with reference to the

[0060] It should be understood, of course, that according to the present system, device and method, any of the examples, embodiments or processes described herein can be combined with one or more other examples, embodiments and / or processes, or separated, and / or performed in a discrete device or device portion.​

[0061] In conclusion, the above discussion is intended only to be a description of the system of the present application and should not be taken in a limiting sense. Thus, while the system has been described in detail with reference to exemplary embodiments, it should be appreciated that numerous variations and substitutions will occur to those skilled in the art. Accordingly, the specification and drawings are to be regarded in an illustrative sense and are not a limitation on the scope of the appended claims.

Claims

1. An ultrasound imaging system for shear wave imaging, comprising: an ultrasound transducer, wherein the ultrasound transducer comprises an array of ultrasound sensors arranged to acquire echoes, wherein the echoes are in response to ultrasound pulses transmitted toward a target tissue; and a beamformer, wherein the beamformer is arranged to control the array of ultrasound sensors to transmit a current push pulse in accordance with current push pulse parameters, wherein the current push pulse has a current focus depth, wherein the current push pulse is arranged to generate a current shear wave, wherein the beamformer is arranged to receive parameters of a next push pulse while transmitting the current push pulse parameters to the ultrasound transducer, wherein the parameters of the next push are used to transmit a next push pulse, wherein the next push pulse has a next focus depth, wherein the next focus depth is different from the current focus depth, wherein the next push pulse is arranged to generate a next shear wave, wherein the current shear wave and the next shear wave constructively interfere to generate a composite shear wave in the target tissue.

2. The ultrasound imaging system of claim 1, wherein the composite shear wave comprises an approximately cylindrical shape, wherein the approximately cylindrical shape is defined in part by a combined depth of the current push pulse and the next push pulse.

3. The ultrasound imaging system of claim 1, wherein, the beamformer comprises an active register and a shadow register configured to transmit the parameters of the current push pulse to the ultrasound transducer and receive the parameters of the next push pulse from a controller circuit, respectively.

4. The ultrasound imaging system of claim 1, wherein, the beamformer is configured to reduce a transmission delay between the current push pulse and the next push pulse.

5. The ultrasound imaging system of claim 1, wherein, the beamformer is configured to repeat the current push pulse until the parameters of the next push pulse are used to transmit the next push pulse.

6. The ultrasound imaging system of claim 1, wherein, a controller circuit is arranged to implement a push pulse scheme in accordance with a user command.

7. The ultrasound imaging system of claim 6, wherein, the push pulse scheme comprises a sequence of push pulses, each push pulse having a different focus depth.

8. The ultrasound imaging system of claim 7, further comprising a user interface configured to display the push pulse scheme.

9. The ultrasound imaging system of claim 1, wherein, the beamformer is further configured to transmit a tracking pulse, wherein the tracking pulse is spatially arranged to intersect the composite shear wave at one or more locations within the target tissue.

10. The ultrasound imaging system of claim 9, wherein the beamformer is further configured to receive echo signals, wherein the echo signals are indicative of locations where the tracking pulse intersects the composite shear wave.

11. The ultrasound imaging system of claim 10, further comprising tissue analysis circuitry, wherein, the tissue analysis circuit is arranged to determine an elasticity of the target tissue based on the echo signals.

12. A method of shear wave imaging, the method comprising: acquiring ultrasound echoes, wherein the ultrasound echoes are in response to ultrasound pulses transmitted toward a target tissue; transmitting a current push pulse, wherein the current push pulse has current pulse parameters, wherein the current push pulse has a current focus depth in accordance with the current push pulse parameters, wherein the current push pulse is arranged to generate a current shear wave; and receiving parameters of a next push pulse concurrently with transmitting the current push pulse parameters, wherein the next push parameters are used to transmit a next push pulse, wherein the next push pulse has a next focal depth, wherein the next focal depth is different than the current focal depth, wherein the next push pulse is arranged to generate a next shear wave, wherein the current shear wave and the next shear wave constructively interfere to generate a composite shear wave in the target tissue.

13. The method of claim 12, wherein the composite shear wave comprises an approximately cylindrical shape, wherein the approximately cylindrical shape is defined in part by a combined depth of the current push pulse and next push pulse.

14. The method of claim 12, further comprising decrementing a transmission delay between the current push pulse and the next push pulse.

15. The method of claim 12, further comprising repeating the current push pulse until the next push pulse is transmitted with the next push pulse parameters.

16. The method of claim 12, further comprising transmitting a tracking pulse, wherein, the tracking pulse is spatially arranged to intersect the composite shear wave at one or more locations within the target tissue.

17. A non-transitory computer readable medium comprising executable instructions that, when executed, cause a processor circuit of an ultrasound imaging system to perform the method of claim 12.

Images