Method and system for encoding and decoding radio frequency data

Abstract

Disclosed herein are systems and methods for encoding radio frequency (RF) data (e.g., electrical signals) by a microwave beamformer. The microwave beamformer can sum samples of the RF data stored in a plurality of memory cells using a pseudo-random sampling pattern (700). In some examples, the memory cells can be included in a delay line of the microwave beamformer. The summed samples can form a coded signal that is transmitted to a decoder that reconstructs the original RF data from the coded signal. In some examples, the decoder can use knowledge of the pseudo-random sampling pattern to reconstruct the original data.

Description

Technical Field

[0001] The present application relates to encoding and decoding radio frequency data associated with ultrasound signals. More particularly, the present application relates to utilizing a microbeamformer to encode radio frequency data for decoding by an ultrasound imaging system. Background Art

[0002] While providing high resolution, ultrasound image acquisition using focused beam transmission and dynamic receive beamforming imposes time constraints on real-time volumetric imaging. Compared to unfocused beam imaging methods, an order of magnitude higher is required for focused beam transmission to cover the three-dimensional (3D) imaging region of interest (ROI), which results in a much slower frame rate. This can be a serious problem for imaging applications where high frame rates are important (e.g., 3D cardiac imaging). For faster imaging, unfocused ultrasound transmissions can be used. Compared to focused beam transmissions, unfocused transmissions can illuminate a large portion of the ROI with a single transmission. These unfocused transmissions can include plane waves or spherical or cylindrical diverging waves.

[0003] Ultrasound probes with two-dimensional (2D) transducer arrays can be used for faster and / or higher resolution 3D imaging. However, 2D transducer arrays can have arrays of hundreds or thousands of transducer elements that need to be coupled to an imaging system. In order to avoid the use of a large number of cables between the ultrasound probe and the imaging system base, some ultrasound probes include a microbeamformer. The microbeamformer receives signals from individual transducer elements and performs some preliminary beamforming operations to combine signals from transducer element groups (e.g., subarrays, tiles) into output signals. The preliminary beamforming operation may include applying a delay to the signal from the individual transducer element and then summing the delayed signal to generate an output signal. The number of output signals may be based on the number of tiles into which the transducer array is divided. Combining the signals of individual transducer element groups into output signals may reduce the number of channels required. For example, an ultrasound probe may have 128 output channels coupled to the ultrasound system base. However, microbeamformers are typically designed to focus the transmit beam, and as the receive beam is steered away from the transmit beam main axis, image quality begins to degrade. Implementing divergent and plane wave imaging with a transducer array coupled to a microbeamformer reduces image contrast and introduces grating lobe artifacts. Techniques for combining the potential high-speed 3D imaging capabilities of divergent and plane wave imaging with transducer arrays including microbeamformers with reduced image degradation are desirable. Summary of the invention

[0004] Methods and systems for microwave beamforming operations that can improve image acquisition speed and quality are disclosed. Microbeamforming and beamforming operations perform encoding and decoding. Instead of constructing an image directly from the microwave beamformed data, the original data is reconstructed based on a finite number of measurements and image formation is performed based on the reconstruction. The microwave beamformer can use a jittered sampling scheme to encode the data in a manner compatible with analog RAM. The microwave beamformer encoding can multiplex spatial frequencies in a fast time. Based on the output of the encoded microwave beamformer, the original signal can be reconstructed using a computationally inexpensive inversion method as described herein. An image can be formed from the reconstructed data.

[0005] According to an example of the present disclosure, a system may include a transducer array including a plurality of transducer elements. The transducer elements may be configured to receive ultrasound echoes and convert the ultrasound echoes into electrical signals (e.g., RF data, RF signals). The system may include a microwave beamformer coupled to the plurality of transducer elements. The microwave beamformer may include a first delay line coupled to a first transducer element of the plurality of transducer elements. The first delay line may include a first plurality of memory cells configured to store the electrical signals received from the first transducer element. The microwave beamformer may also include a second delay line coupled to a second transducer element of the plurality of transducer elements. The second delay line may include a second plurality of memory cells configured to store the electrical signals received from the second transducer element. The microwave beamformer may be configured to perform jitter sampling on the electrical signals stored in the first plurality of memory cells and the second plurality of memory cells and generate a jitter signal. The system may include a decoder configured to receive the dithering signal and generate a reconstructed signal representative of the electrical signal.

[0006] According to an example of the present disclosure, a method may include: acquiring multiple samples of an electrical signal, wherein the electrical signal is associated with an acoustic signal; storing the multiple samples in multiple memory cells, wherein individual memory cells of the multiple memory cells store individual samples of the multiple samples; pseudo-randomly selecting a subset of the multiple memory cells, wherein the subset includes fewer memory cells than the multiple memory cells; summing the individual samples of the multiple samples stored in the subset of the multiple memory cells to generate a jitter signal; and decoding the jitter signal to generate a reconstructed signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1Simplified diagrams illustrating an imaging system with a typical microbeamformer arrangement and an imaging system with a microbeamformer arrangement according to an example of the present disclosure are shown.

[0008] Figure 2 is a block diagram of an ultrasound imaging system arranged according to some examples of the present disclosure.

[0009] Figure 3 is a block diagram illustrating an example processor according to some examples of the present disclosure.

[0010] Figure 4 is a block diagram of components of an imaging system according to an example of the present disclosure.

[0011] Figure 5 is a block diagram of a programmable delay line according to an example of the present disclosure.

[0012] Figure 6 is a graphical illustration of typical delay-and-sum beamforming with jittered sampling according to an example of the present disclosure.

[0013] Figure 7 is a diagram of an example jitter sample grouping according to an example of the present disclosure.

[0014] Figure 8 is a graphical representation of the delays of transducer elements in a two-dimensional array according to an example of the present disclosure.

[0015] Fig.9A is an illustration of an example of a set of pseudo-random delay patterns on a 16-element by 16-element array with 4 by 4 tiles according to an example of the present disclosure.

[0016] Fig. 9B is a diagram of an example packet 900B according to an example of the present disclosure, wherein three sequential time samples are shown in three dimensions.

[0017] Fig.10 are flow diagrams of methods according to some examples of the present disclosure.

[0018] Fig.11 , Fig.12 and Fig.13 Examples of an original signal and a reconstructed signal generated according to examples of the present disclosure are shown. DETAILED DESCRIPTION

[0019] The following description of certain exemplary embodiments is merely exemplary in nature and is in no way intended to limit the invention or its application or use. In the following detailed description of the embodiments of the present system and method, reference is made to the accompanying drawings, which form part of the following detailed description and illustrate by way of illustration specific embodiments in which the described systems and methods can be practiced. These embodiments are described herein in sufficient detail to enable those skilled in the art to practice the currently disclosed systems and methods, and it should be understood that other embodiments may be utilized and structural and logical changes may be made without departing from the spirit and scope of the present system. In addition, for the sake of clarity, when certain features are obvious to those skilled in the art, the detailed description of these features will not be discussed in detail to avoid blurring the description of the present system. Therefore, the following detailed description should not be considered to have a limiting meaning, and the scope of the present system is limited only by the claims.

[0020] According to the principles of the present disclosure, instead of combining signals from individual transducer elements using a conventional delay + sum method, a microwave beamformer can be used as an encoder to encode radio frequency (RF) data associated with received echoes, and the encoded data can be transmitted from an ultrasound probe to an imaging system base, where the encoded data is decoded to reconstruct the original RF data (e.g., signal). An image can then be generated based on the reconstructed data. Generating an image based on the reconstructed data can have fewer artifacts (e.g., grating lobes) than generating an image based on typical delay + sum beamforming. In addition to mitigating artifacts of microwave beamforming, reconstruction of the original data can also allow more advanced adaptive beamforming algorithms, which can require original channel data.

[0021] In ultrasound imaging applications, RF data may be highly correlated and / or compressible (e.g., in a fast time). Encoding RF data may exploit this redundancy and compress the original RF data. However, despite the compression, the original RF data may still be recovered by decoding the encoded data. This may reduce the amount of data required to be transmitted between the ultrasound probe and the base of the imaging system.

[0022] Figure 1A simplified diagram illustrating an imaging system 100 having a typical microbeamformer arrangement and an imaging system 102 having a microbeamformer arrangement according to an example of the present disclosure is shown. The imaging system 100 includes an ultrasound probe 104, which may include a transducer array having individual transducer elements (not shown). The transducer array may transmit ultrasound signals and receive echo signals in response to the transmitted ultrasound signals. The transducer elements may generate electrical signals (e.g., RF data) in response to the echo signals. The RF data may be transmitted from the transducer elements to a microbeamformer 106. The microbeamformer may split the signals from the transducer elements into tiles. In Figure 1 In the example shown, the transducer elements are grouped into two tiles P1, P2. The microbeamformer may apply an appropriate delay to the signals received from each transducer in the tile and sum the delayed signals into a single output signal OS1, OS2 for each tile P1, P2, respectively. The appropriate delay may be determined at least in part on the relative position of the transducer element on the tile relative to the other transducer elements. The output signals OS1 and OS2 may be partially beamformed signals. The output signals OS1 and OS2 may be provided to a main beamformer 108 included in a system base 110 of the imaging system 100. The main beamformer 108 may apply an additional delay to the output signals OS1 and OS2 to form a fully beamformed signal BFS for generating an ultrasound image 112.

[0023] The imaging system 102 may include an ultrasound probe 114 that may include a transducer array having individual transducer elements (not shown) that transmit RF data to a microbeamformer 116 that divides the transducer elements into tiles P1, P2, similar to the case of the system 100. In contrast to the system 100, the microbeamformer may sample the RF data received from the transducer elements and / or apply delays in a pseudo-random manner, and then sum the delayed samples of each tile to generate a coded signal ES1, ES2. The coded signal ES1, ES2 may be provided to a decoder 124 located on the system base 120. The decoder 124 may reconstruct the original RF data from the coded signal ES1, ES2. The reconstructed data may be provided to the beamformer 118, which may perform a beamforming operation to generate an image 122.

[0024] According to an example of the present disclosure, a system may include a transducer array including a plurality of transducer elements. The transducer element may be configured to receive an ultrasound echo and convert the ultrasound echo into an electrical signal (e.g., RF data, RF signal). The system may include a microwave beamformer coupled to a plurality of transducer elements. The microwave beamformer may include a first delay line coupled to a first transducer element of a plurality of transducer elements. The first delay line may include a first plurality of memory cells configured to store an electrical signal received from the first transducer element. The microwave beamformer may also include a second delay line coupled to a second transducer element of a plurality of transducer elements. The second delay line may include a second plurality of memory cells configured to store an electrical signal received from the second transducer element. In some examples, the delay line may be a programmable delay line. In some examples, the plurality of memory cells are configured as a circular buffer. The microbeamformer may be configured to dither sample the electrical signals stored in the first and second pluralities of memory cells and generate a dithered signal. The system may include a decoder configured to receive the dithered signal and generate a reconstructed signal representative of the electrical signals.

[0025] In some examples, the system may include a main beamformer configured to generate a beamformed signal based at least in part on the reconstructed signal. In some examples, the main beamformer may include a decoder. In some examples, the system may include a transmit controller, wherein the transmit controller provides a delay to be added to the dither signal by the microbeamformer to focus or steer a beam associated with the ultrasound echo.

[0026] In some examples, the microbeamformer is configured to generate a dithered signal by pseudo-randomly summing electrical signals sampled from the first plurality of memory cells and the second plurality of memory cells. In some examples, the decoder is configured to apply a covariance matrix to the dithered signal to generate a reconstructed signal, wherein the covariance matrix is ​​based at least in part on the dithered sampling of the electrical signals stored in the first plurality of memory cells and the second plurality of memory cells.

[0027] In some examples, the microbeamformer is configured to dither sample electrical signals stored in the first plurality of memory cells and the second plurality of memory cells using a time sample period of a pseudo-random pattern. In some examples, the time sample period of the pseudo-random pattern is configured such that individual memory cells of the first plurality of memory cells and the second plurality of memory cells are sampled no more than once per storage cycle.

[0028] In some examples, a first subset of the plurality of transducer elements is grouped into a first tile including a first transducer element, and a second subset of the plurality of transducer elements is grouped into a second tile including a second transducer element.

[0029] Figure 2 A block diagram of an ultrasound imaging system 200 constructed according to the principles of the present disclosure is shown. The ultrasound imaging system 200 according to the present disclosure may include a transducer array 214, which may be included in an ultrasound probe 212 (e.g., an external probe or an internal probe (e.g., an intravascular ultrasound (IVUS) catheter probe)). In other embodiments, the transducer array 214 may be in the form of a flexible array configured to apply conformal imaging to the surface of an object to be imaged (e.g., a patient). The transducer array 214 is configured to transmit an ultrasound signal (e.g., a beam, a wave) and receive echoes in response to the ultrasound signal. Various transducer arrays may be used, such as linear arrays, curved arrays, or phased arrays. For example, the transducer array 214 can include a two-dimensional array of transducer elements (as shown), which can be scanned in both the altitude dimension and the azimuth dimension for 2D imaging and / or 3D imaging. It is generally known that the axial direction is the direction normal to the array face (in the case of a curved array, the axial direction is the fan-out direction), the azimuth direction is generally defined by the longitudinal dimension of the array, and the altitude direction is transverse to the azimuth direction.

[0030] The transducer array 214 may be coupled to a microbeamformer 216, which may be located in the ultrasound probe 212 and may control the transmission and reception of signals by the transducer elements in the array 214. In some embodiments, the microbeamformer 216 may control the transmission and reception of signals by the active elements (e.g., an active subset of the array elements that define an active aperture at any given time) in the array 214. The transducer elements in the array 214 may generate radio frequency (RF) data (e.g., electrical signals) and transmit the RF data to the microbeamformer 216.

[0031] In some embodiments, the microbeamformer 216 can be coupled, for example, by a probe cable or wirelessly, to a transmit / receive (T / R) switch 218 that switches between transmit and receive and protects the decoder 244 and the main beamformer 222 from high energy transmit signals. In some embodiments, such as in a portable ultrasound system, the T / R switch 218 and other elements of the system can be included in the ultrasound probe 212 rather than in the ultrasound system base, which can house the image processing electronics. The ultrasound system base typically includes software and hardware components, including circuits for signal processing and image data generation and executable instructions for providing a user interface.

[0032] The process of transmitting ultrasound signals from the transducer array 214 under the control of the microbeamformer 216 is directed by the transmit controller 220, which can be coupled to the T / R switch 218, and the decoder 244 is coupled to the main beamformer 222. The transmit controller 220 can control the direction in which the beam is steered. The beam can be steered forward from directly in front of the transducer array 214 (orthogonal to the transducer array 214), or steered at different angles to obtain a wider field of view. Unfocused beams (e.g., plane waves, diverging waves) can also be emitted. The transmit controller 220 can also be coupled to the user interface 224 and receive input from user operation of user controls. The user interface 224 may include one or more input devices (e.g., a control panel 252), which may include one or more mechanical controls (e.g., buttons, encoders, etc.), touch-sensitive controls (e.g., touch pads, touch screens, etc.), and / or other known input devices.

[0033] According to the principles of the present disclosure, the microbeamformer 216 may receive RF data from the transducer elements of the transducer array 214 to generate a coded signal. The details of the coding will be explained in further detail below. The microbeamformer 216 may be coupled to the decoder 244 via a probe cable or wirelessly. The coded signal may be provided by the microbeamformer 216 to the decoder 244. The decoder 244 may decode the coded signal provided by the microbeamformer 216 to reconstruct the RF data. The reconstructed RF data may be provided by the decoder 244 to the main beamformer 222. In some embodiments, the decoder 244 may be implemented by one or more processors.

[0034] The main beamformer 222 may perform a beamforming operation (e.g., delay + sum or other beamforming operation) to generate a fully beamformed signal. The beamformed signal of the beamformer 222 is coupled to the processing circuit 250, which may include one or more processors (e.g., signal processor 226, B-mode processor 228).

[0035] The signal processor 226 can be configured to process the received beamformed RF data in various ways, such as bandpass filtering, decimation, I component and Q component separation, and harmonic signal separation. The signal processor 226 can also perform additional signal enhancements, such as speckle reduction, signal compounding, and noise cancellation. The processed signals (also referred to as I and Q components or IQ signals) can be coupled to additional downstream signal processing circuits for image generation. The IQ signals can be coupled to multiple signal paths within the system, each of which can be associated with a specific arrangement of signal processing components suitable for generating different types of image data (e.g., B-mode image data, Doppler image data). For example, the system may include a B-mode signal path 258 that couples a signal from the signal processor 226 to the B-mode processor 228 for generating B-mode image data.

[0036] The B-mode processor can use amplitude detection for imaging structures in the body. The signal generated by the B-mode processor 228 can be coupled to a scan converter 230 and / or a multi-plane reformatter 232. The scan converter 230 can be configured to arrange the echo signals into a desired image format according to the spatial relationship when the echo signals are received. For example, the scan converter 230 can arrange the echo signals into a two-dimensional (2D) fan format or a three-dimensional (3D) format of a pyramid or other shape. The multi-plane reformatter 232 can convert the echoes received from points in a common plane in a volumetric region of the body into an ultrasound image (e.g., a B-mode image) of the plane, for example, as described in U.S. Pat. No. 6,443,896 (Detmer). In some embodiments, the scan converter 230 and the multi-plane reformatter 232 can be implemented as one or more processors.

[0037] The volume renderer 234 may generate an image (also referred to as a projection, rendering, rendering result) of the 3D data set as viewed from a given reference point, for example, as described in U.S. Pat. No. 6,530,885 (Entrekin et al.). In some embodiments, the volume renderer 234 may be implemented as one or more processors. The volume renderer 234 may generate a rendering (e.g., a positive rendering or a negative rendering) by any known or future known technique (e.g., surface rendering and maximum intensity rendering).

[0038] The outputs (e.g., B-mode images) from the scan converter 230, the multiplanar reformatter 232, and / or the volume renderer 234 can be coupled to an image processor 236 for further enhancement, buffering, and temporary storage prior to being displayed on an image display 238. The graphics processor 240 can generate graphic overlays for display with the images. These graphic overlays can contain, for example, standard identifying information (e.g., patient name), date and time of the image, imaging parameters, etc. For these purposes, the graphics processor can be configured to receive input from a user interface 224 (e.g., typed patient name or other annotations). The user interface 224 can also be coupled to the multiplanar reformatter 232 for selecting and controlling the display of multiple multiplanar reformatted (MPR) images.

[0039] The system 200 may include a local memory 242. The local memory 242 may be implemented as any suitable non-transitory computer-readable medium (e.g., a flash drive, a disk drive). The local memory 242 may store data generated by the system 200 (including B-mode images), executable instructions, input provided by a user via the user interface 224, or any other information necessary for the operation of the system 200.

[0040] As previously mentioned, system 200 includes user interface 224. User interface 224 may include display 238 and control panel 252. Display 238 may include a display device implemented using various known display technologies (e.g., LCD, LED, OLED or plasma display technology). In some embodiments, display 238 may include multiple displays. Control panel 252 may be configured to receive user input (e.g., threshold, filter type, drawing type). Control panel 252 may include one or more hard controls (e.g., buttons, knobs, dials, encoders, mice, trackballs, etc.). In some embodiments, control panel 252 may additionally or alternatively include soft controls (e.g., GUI control elements or referred to as GUI controls) provided on a touch-sensitive display. In some embodiments, display 238 may be a touch-sensitive display that includes one or more soft controls of control panel 252.

[0041] In some embodiments, Figure 2 The various components shown in can be combined. For example, image processor 236 and graphics processor 240 can be implemented as a single processor. In another example, scan converter 230 and multi-plane reformatter 232 can be implemented as a single processor. In some embodiments, Figure 2 The various components shown may be implemented as separate components. In some embodiments, Figure 2One or more of the various processors shown may be implemented by a general purpose processor and / or a microprocessor configured to perform a specific task. In some embodiments, one or more of the various processors may be implemented as an application specific integrated circuit. In some embodiments, one or more of the various processors (e.g., image processor 236) may be implemented using one or more graphics processing units (GPUs).

[0042] Figure 3 is a block diagram illustrating an example processor 300 according to the principles of the present disclosure. The processor 300 may be used to implement one or more processors described herein, for example, Figure 2 The image processor 236 is shown. The processor 300 may be any suitable processor type, including but not limited to a microprocessor, a microcontroller, a digital signal processor (DSP), a field programmable array (FPGA) (where the FPGA has been programmed to form a processor), a graphics processing unit (GPU), an application specific integrated circuit (ASIC) (where the ASIC has been designed to form a processor), or a combination thereof.

[0043] Processor 300 may include one or more cores 302. Core 302 may include one or more arithmetic logic units (ALUs) 304. In some embodiments, core 302 may include a floating point logic unit (FPLU) 306 and / or a digital signal processing unit (DSPU) 308 in addition to or in lieu of ALU 304.

[0044] Processor 300 may include one or more registers 312 that are communicatively coupled to core 302. Registers 312 may be implemented using dedicated logic gates (e.g., flip-flops) and / or any memory technology. In some embodiments, registers 312 may be implemented using static memory. Registers may provide data, instructions, and addresses to core 302.

[0045] In some embodiments, the processor 300 may include one or more levels of cache memory 310 communicatively coupled to the core 302. The cache memory 310 may provide computer readable instructions to the core 302 for execution. The cache memory 310 may provide data for processing by the core 302. In some embodiments, the computer readable instructions may have been provided to the cache memory 310 via a local memory (e.g., a local memory attached to the external bus 316). The cache memory 310 may be implemented using 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.

[0046] Processor 300 may include controller 314, which may be controlled by other processors and / or components included in the system (e.g., Figure 2 252 and scan converter 230) to the input of the processor 300 and / or from the controller 300 to other processors and / or components included in the system (e.g., Figure 2 308 and the output of the volume renderer 234). The controller 314 can control the data paths in the ALU 304, FPLU 306 and / or DSPU 308. The controller 314 can be implemented as one or more state machines, data paths and / or dedicated control logic units. The gates of the controller 314 can be implemented as independent gates, FPGAs, ASICs, or any other suitable technology.

[0047] Registers 312 and cache 310 may communicate with controller 314 and core 302 via internal connections 320A, 320B, 320C, and 320D. The internal connections may be implemented as a bus, multiplexer, crossbar switch, and / or any other suitable connection technology.

[0048] Input and output to the processor 300 may be provided via a bus 316, which may include one or more conductors. The bus 316 may be communicatively coupled to one or more components of the processor 300, such as the controller 314, cache memory 310, and / or registers 312. The bus 316 may be coupled to one or more components of the system, such as the previously mentioned display 238 and control panel 252.

[0049] Bus 316 may be coupled to one or more external memories. External memory may include read-only memory (ROM) 332. ROM 332 may be a mask ROM, an electronically programmable read-only memory (EPROM), or any other suitable technology. External memory may include random access memory (RAM) 333. RAM 333 may be static RAM, battery-backed static RAM, dynamic RAM (DRAM), or any other suitable technology. External memory may include electrically erasable programmable read-only memory (EEPROM) 335. External memory may include flash memory 334. External memory may include a magnetic storage device such as a disk 336. In some embodiments, external memory may be included in a system (e.g., Figure 2 In the ultrasound imaging system 200 shown, for example, the local memory 242.

[0050] As previously referenced Figure 1As discussed, a transducer array comprising a plurality of transducer elements may be divided into tiles (sometimes also referred to as sub-arrays or simply groups) by a microbeamformer. Figure 4 4 is a block diagram of components of an imaging system 400 according to an example of the present disclosure. The imaging system 400 may include a transducer element 402, a microbeamformer 404, and a decoder 406. The transducer element 402 may be included in a transducer array ( Figure 4 4). The transducer element 402 can provide an RF signal to each delay line 408 of the microwave beamformer 404. In some examples (e.g., Figure 4 In the example shown), the delay line 408 can be a programmable delay line. The delay line 408 can be coupled to a summing node 410. All delay lines coupled to the same summing node 410 can be included in the same tile 412. The output of the summing node 410 from each tile 412 can be provided to the decoder 406. The components of the imaging system 400 can be used to implement Figure 2 For example, the microbeamformer 404 may be used to implement one or more of the components of the imaging system 200 shown in FIG. Figure 2 Microbeamformer 216 in.

[0051] Figure 5 is a block diagram of a programmable delay line 500 according to an example of the present disclosure. In some examples, the programmable delay line 500 can be used to implement Figure 4 Delay line 408 in. Delay line 500 can receive input via input line 502. In some examples (e.g., Figure 5 In the example shown in FIG. 5 , the input line 502 may include an input buffer 504. The input line 502 may receive a signal from a transducer element ( Figure 5 ) (e.g., Figure 4 The delay line 500 may include a plurality of input switches 506. The input switches 506 may direct the electrical signal from the input line 502 to one or more memory cells 508 by selectively coupling the memory cells 508 to the input line 502. In some examples, the memory cells 508 may utilize capacitors (e.g., Figure 5 The memory cell 508 may store an electrical signal received from the input line 502. The delay line 500 may include a plurality of output switches 510. The output switches 510 may selectively couple one or more memory cells 508 to an output line 512. When coupled to the output line 512, the electrical signal stored in the memory cell 508 may be transmitted to the output line 512. The output line 512 may transmit the electrical signal to the summing node ( Figure 5 ) (e.g., Figure 4 In some examples (e.g., Figure 5 In the example shown), the output line 512 may include an output buffer 514.

[0052] The operation of the input switch 506 can be controlled by the input controller logic circuit 516. The input controller logic circuit 516 can receive a clock signal and the input switch 506 is closed in response to the rising and / or falling edges of the clock in the clock signal. In some examples, the input controller logic circuit 516 may include a counter and a multiplexer. The input controller logic circuit 516 controls which memory cells 508 store the electrical signal received via the input line 502 within each clock cycle. Therefore, the delay line 500 effectively samples the electrical signal on the input line 502 and stores the sample in the memory cell 508. The sampling rate can be based on the frequency of the clock signal. The sampling rate of the delay line 500 should not be less than the Nyquist rate of the electrical signal to avoid aliasing of the electrical signal.

[0053] In some examples, the delay line 500 can be configured as a circular buffer. That is, within each clock cycle, one input switch 506 is closed to couple one memory cell 508 to the input line 502, thereby storing the electrical signal present on the input line 502 during that clock cycle. The input controller logic circuit 516 cycles through the input switches 506 in the same order. For example, the first memory cell 508 (e.g., Figure 5 The top memory cell 508 shown may hold a first time sample, the second memory cell 508 may hold a second time sample, etc. After all memory cells 508 have been written, the input controller logic circuit 516 may repeat the cycle, overwriting any stored data in the memory cells 508 during the next memory cycle. For example, if the delay line 500 includes eight input switches 506 and eight memory cells 508, then after eight clock cycles, the data in the first memory cell 508 will be overwritten with the new data received from the input line 502.

[0054] The operation of the output switches 510 may be controlled by output controller logic 518. The output controller logic 518 may receive the delay data and change which output switches 510 are closed to couple the memory cells 508 to the output line 512. The output controller logic 518 may be controlled by one or more shift registers (not shown) or a transmit controller ( Figure 5 ) (e.g., Figure 2508) receives the delay data. In other examples, the delay data can be programmed into a memory included in the output controller logic circuit 516. The time between when a sample of the electrical signal is stored on the memory cell 508 and when the memory cell 508 is coupled to the output line 512 can determine the delay of the electrical signal. Providing a sample of the electrical signal to the output line 512 can be a destructive read. That is, once the memory cell 508 has provided a sample to the output line 512, the memory cell 508 no longer stores the electrical signal. Therefore, a sample can only be read once from the memory cell 508. Once read, there is no valid data in the memory cell 508 until the memory cell 508 is coupled to the input line 502 again to receive a new sample of the electrical signal.

[0055] For example purposes, Figure 5 The delay line 500 shown, and the principles of the present disclosure are not limited to Figure 5 Examples of other suitable delay lines and / or delay line controls that may be used may be found in US Pat. Nos. 5,997,479 and 6,013,032 to Savord and 8,161,817 to Robinson.

[0056] In typical microbeamformer operation, each sample from each memory cell 508 may be appropriately delayed by controlling the output switch 510 and provided to the output line 512 for summing with the outputs of the other delay lines of the tile. When the delay lines 500 are arranged as circular buffers, the maximum delay may be limited to the length of a memory cycle (e.g., eight cycles in the previously described example). Otherwise, the samples may be overwritten by newly acquired samples. The microbeamformer may then provide the summed outputs of the delay lines of the tile to the main beamformer.

[0057] According to the principles of the present disclosure, a jitter sampling scheme may be used to control the output switch 510. Figure 6 As described in more detail in Figure 5-9, the jitter sampling scheme can apply a pseudo-random delay to the electrical signal stored in the memory unit 508. In addition, not all samples collected by the memory unit 508 can be provided to the output line 512. That is, the jitter sampling scheme can downsample the electrical signal. The jitter sampling scheme can be provided to the output controller logic circuit 518 to control the operation of the output switch 510, thereby performing the jitter sampling operation. The jitter sampling scheme can encode the electrical signal so that the electrical signal can be reconstructed by the decoder.

[0058] Figure 6 It is a typical delay and sum (DAS) beamforming (A flat) and jitter sampling (A) according to an example of the present disclosure jitter ). For ease of understanding, the jitter sampling scheme is first described with reference to a one-dimensional array of fifteen transducer elements grouped into three tiles, where each tile includes five transducer elements. In DAS beamforming, samples of electrical signals (e.g., RF data) from transducer elements acquired by a delay line (e.g., delay line 500) are delayed so that signals from the same spatial location are aligned in time (e.g., delayed) and then summed. This is shown in panes 602, 604, and 606. The horizontal axis corresponds to the transducer element and the vertical axis corresponds to the time sample of the transducer element. The time samples can be stored in a memory unit (e.g., memory unit 508). As indicated by the dark blue square 608 for tile 1, the dark blue square 610 for tile 2, and the dark blue square 612 for tile 3, the first time sample from each transducer element is summed together after alignment to obtain the signals for tile 1, tile 2, and tile 3. For example, the first time sample can be stored in Figure 5 508 shown at the top. Next, the second time samples for each transducer element may be aligned and summed. For example, the second time samples may be stored in Figure 5 The signals from the five transducer elements of each tile are combined into a single signal and sent to the imaging system base by the microbeamformer. Figure 5 In the example shown, three signals instead of fifteen are sent from the ultrasound probe to the imaging system.

[0059] In accordance with the principles of the present disclosure, a microbeamformer may be used to encode electrical signals rather than performing typical DAS beamforming. The encoding may use a jittered sampling scheme that pseudo-randomly sums the time samples stored in the delay lines for the transducer elements. Panes 614, 616, and 618 illustrate examples of jittered sampling schemes. As shown in dark blue square 620, tile 1 combines the second time samples for transducer elements 1, 3, 4, and 5 with the first time sample from transducer element 2. As shown in dark blue square 622, tile 2 combines the second time samples of transducer elements 6, 8, 10, the third time sample of transducer element 7, and the first time sample of transducer element 9. As shown in dark blue square 624, tile 3 combines the second time samples of transducer elements 11 and 13 with the first time samples of transducer elements 12, 14, and 15.

[0060] The jittered sampling scheme can reduce the amount of data transmitted from the ultrasound probe to the imaging system base, but can allow reconstruction of the original complete sampled data. The jittered sampling scheme can access only a small number of previous samples (e.g., Figure 6 In the example shown, three previous samples are used), so a delay line with a large number of memory cells is not required. The jitter sampling scheme reads each memory cell only once per memory cycle. In addition, Figure 6 As shown, the jitter sampling scheme communicates across tiles by varying the pseudo-random pattern across tiles and time.

[0061] Figure 7 An example jitter sample grouping 700 is illustrated according to an example of the present disclosure. The example jitter sample grouping 700 shows how the jitter sampling scheme varies across time. Each pane shows a non-overlapping delay grouping for the jitter sampling scheme, which is used to generate three sequential output samples according to the tile. The light-colored blocks of each pane illustrate the time samples for each transducer element read from the memory unit. Figure 7 In the example dither sampling scheme shown, three sequential sample patterns are grouped together and then randomly summed across the transducer elements so that each memory cell is read once. Figure 6 Unlike conventional microwave beamforming shown in the top pane, the delay does not increase monotonically. Figure 7 Three groups of fifteen sample segments are shown, but other numbers of groups may be used. For example, five different groups of time samples may be used that result in the data being divided into twenty-five time sample segments. In this example, the jittered sampling scheme is repeated periodically for each non-overlapping fifteen sample segment. Other jittered sampling schemes of non-overlapping sampling may also be used.

[0062] In a heuristic manner, the jittered sampling acquisition scheme for encoding an RF signal (e.g., an electrical signal) by a microbeamformer can be understood as follows: although two consecutive rapid time samples of the microbeamformer are very similar and the samples have exactly the same spatial frequency (e.g., a first time sample stored in a first memory unit and a sequential second time sample stored in a second memory unit of the delay line), the two consecutive jittered samples sample different spatial frequencies. In a sense, the jittered sampling acquisition multiplexes different spatial frequencies in rapid time. If the microbeamformer clock (e.g., a clock signal controlling the input control logic circuit 516, the input control logic circuit 516 controls Figure 5 This is possible if the operation of the input switch 506 in ) is significantly faster than the RF signal sampling requirement. However, dithered sampling can perform better compression than simply downsampling the data to its Nyquist limit.

[0063] Figure 6 A shown flat and A jitter Both of these can be written as a linear operator for downsampling the original data (x) comprising 225 data points (15 samples x 3 tiles x 5 transducer elements per tile) to a reduced number of measurements (y) (15 samples x 3 tile output signals).

[0064] A flat x=yorA jitter x=y

[0065] exist Figure 6 and Figure 7 A one-dimensional example of microwave beam forming, for A flat And A jitter In both cases, the data compression ratio is 20%.

[0066] The jitter sampling scheme can be extended to two-dimensional (2D) transducer arrays. In 2D, the microbeamformer groups the transducer elements in rectangular tiles (e.g., 3×3, 4×4, 5×5). Depending on the type of microbeamformer included in the ultrasound probe, the microbeamformer can impose additional constraints on the delays of the transducer elements that can be applied to each tile. Each tile can be controlled by a row-by-row constant delay and a column-by-column constant delay (e.g., left delay and bottom delay). Figure 8 A row-by-row delay 802 and a column-by-column delay 804 are shown. Figure 8 In the example shown, the transducer elements are grouped into 4×4 tiles. The delay applied to the electrical signal of each individual transducer element may be the sum of these row-by-row delays 802 and column-by-column delays 804. The control line values ​​for the left and bottom delays may be used to generate a tile 806 of a pseudo-random delay pattern. Figure 8 As shown, different colors indicate different delay values ​​fed to the delay line and the resulting delays of the transducer elements in tile 806. Figure 8 The pane 808 of shows several examples of pseudo-random delay patterns that satisfy the microbeamformer control constraints that can be used to implement a jittered sampling scheme. Figure 6-7 For the 1D case shown, three sequential time samples can be grouped together and then summed randomly. Again, the memory cell is read only once, so the method does not rely on samples being corrupted in previous reads.

[0067] In some examples, five different time sample groups may be used so that the data is divided into fifteen time sample segments. For an analog 2D array comprising 256 elements (16×16), Fig.9AAn example of a set of pseudo-random delay patterns 900A is shown over sixteen 4-element x 4-element tiles corresponding to these fifteen time sample periods. Fig. 9B An example packet 900B is shown having three sequential time samples shown in three dimensions. Fig.9A and Fig. 9B The diagram shows that the samples can be grouped into three non-overlapping sets, similar to Figure 6-7 The case of a one-dimensional array acquisition scheme is shown.

[0068] The jitter samples are collected by a microbeamformer and combined to generate a jitter signal. The jitter signal may be encoded RF data sampled from the transducer elements. In some examples, a delay may be added to the jitter samples and / or the jitter signal to focus or steer the ultrasound beam. The jitter signal may then be provided to a decoder to reconstruct the RF data (e.g., original RF data).

[0069] Reconstructing RF data from a coded signal (e.g., a dithered signal) can be an inverse problem. In reconstructing an estimate of the original (e.g., real) data (x), the compressibility and non-randomness of the RF data can be exploited to improve the reconstruction. To reconstruct the RF data, it can be assumed that the RF data is drawn from a Gaussian distribution with a certain covariance matrix Σ, and the estimate of x (x map ) can be found given the observed data (y) and the prior assumptions on the distribution p(x) of x.

[0070] This estimate of x (x map ) is called the Maximum Posterior (MAP) estimator because it maximizes the posterior distribution,

[0071] max x p(x|y)∝p(y|x)p(x) (1)

[0072] where p(x|y) is the probability of measuring the outcome y given the true data x. For a linear operator A (e.g., A jitter ), the MAP estimator has a closed-form solution:

[0073]

[0074] where Σ is the estimated covariance matrix and y is the output of the microbeamformer (eg, a dithered signal). The decoder may have a pseudo-random pattern (A) used by the microbeamformer to generate the dithered signal. jitter). Thus, equation (2) can be used to reconstruct the original data and perform beamforming. In some examples the covariance matrix Σ can be estimated from a single frame of data and / or can be estimated from synthetically generated data. The matrix in equation (2) can be pre-computed so that the inversion requires only a single matrix multiplication and can be very fast.

[0075] Since both the signal reconstruction operation and the beamforming operation are linear, they can be combined in a single operation to reconstruct the final image from the dithered data.That is, in some examples, the decoder can be included in the main beamformer (or vice versa).

[0076] Fig.10 1 is a flow chart of a method 1000 according to an example of the present disclosure. The flow chart summarizes the microwave beamforming encoding method described herein. At block 1002, a step of "collecting a plurality of samples of an electrical signal" may be performed. In some examples, the collection of a plurality of samples of the electrical signal is controlled by a clock signal. The frequency of the clock signal may be higher than the Nyquist rate of the electrical signal.

[0077] The electrical signal may be associated with the acoustic signal. For example, the transducer element may generate an electrical signal in response to a received echo. The echo may be in response to an ultrasonic signal emitted by the transducer element and / or other transducer elements. The electrical signal may be radio frequency data (e.g., a radio frequency signal). For example, before box 1002, a step of "transmitting an ultrasonic signal" may be performed. In some examples, such transmission may be performed by a transducer array, which includes a plurality of transducer elements. In some examples, the ultrasonic signal may be a plane wave or a diverging wave. After transmitting the ultrasonic signal, a step of "receiving an acoustic signal in response to the ultrasonic signal" may be performed. The acoustic signal (e.g., an echo) may be received using a transducer array. After receiving the acoustic signal, a step of "generating an electrical signal in response to the acoustic signal" may be performed. In some examples, the electrical signal may be generated using a plurality of transducer elements. In some examples, at least one of the plurality of memory cells is coupled to each of the plurality of transducer elements. In some examples, the plurality of transducer elements are grouped into a plurality of tiles, and summing individual samples of the plurality of samples includes summing individual samples associated with at least two tiles of the plurality of tiles.

[0078] At block 1004, a step of storing the plurality of samples in a plurality of memory cells may be performed. Individual memory cells in the plurality of memory cells may store individual samples in the plurality of samples.

[0079] At block 1006, a step of pseudo-randomly selecting a subset of the plurality of memory cells may be performed. The subset may include fewer memory cells than the plurality of memory cells. In some examples, pseudo-randomly selecting a subset of the plurality of memory cells may downsample the electrical signal. In some examples, after block 1006, a step of adding a delay to the pseudo-randomly selected subset of the plurality of memory cells may be performed. The delay may focus or steer a beam associated with the acoustic signal.

[0080] At block 1008, a step of "summing individual samples of the plurality of samples" may be performed. The individual samples may be stored in a subset of the plurality of memory cells. The summing of the individual samples may generate a dithering signal.

[0081] At block 1010, a step of "decoding the jitter signal" may be performed. Decoding the jitter signal may generate a reconstructed signal. Decoding may include applying the matrix described in equation (2) to the jitter signal. In some examples, the covariance matrix may be based at least in part on a pseudo-random selection.

[0082] Figure 11-13 Examples of an original signal and a reconstructed signal generated according to examples of the present disclosure are shown.

[0083] exist Fig.11 , simulated per-channel data from an S5-1 phased array is shown. Pane 1102 shows the original "real image", pane 1104 shows the reconstruction generated after encoding the real data using a dithered sampling scheme and decoding the dithered signal generated by the dithered sampling scheme, and pane 1106 shows the difference between the real and the reconstruction. All panes are displayed with the same dynamic range. This data set was obtained by simulating a synthetic phantom with various gray levels and point targets, where the diverging waves were emitted from a virtual vertex 50 mm behind the physical aperture, including 21 angles uniformly distributed ranging from -45° to 45°. The covariance matrix used to calculate the reconstruction was calculated using data obtained at 0° transmission. The dithered sampling and reconstruction were performed on data obtained at 8° transmission. The real data and the reconstructed data match each other well, and the difference data only has some content corresponding to high amplitude and high frequency echoes.

[0084] Fig.12Simulated channel data from a hypothetical 2D transducer array with 4096 elements (64×64) is shown. However, for simplicity, instead of showing the raw data for all channels, one slice of the 2D array is shown. The x-element index is fixed to channel 23, and the signals from all y-elements are shown. The full aperture is divided into sub-arrays of 16 elements by 16 elements, and the dithered sampling technique described herein is applied to each sub-array. Similar to Fig.11 , the real data is presented in pane 1202, the reconstruction after compression using a dithered sampling scheme is presented in pane 1204, and the difference is presented in pane 1206. This data set is obtained by simulating a synthetic speckle phantom with a highly echogenic target in the middle using plane wave transmission. Fig.12 The real data image and the reconstructed data image in appear similar, however, the difference image has more content with a relatively larger amplitude. Fig.11 The reconstruction shown is just as clean, but the downsampling rate is significantly higher than in the 2D case (for Fig.11 20% for a 1D array in , compared to 20% for Fig.13 ). Despite the significant downsampling, the reconstruction scheme is able to recover most of the original data, e.g. Fig.12 shown.

[0085] Fig.13 Images collected by diverging ultrasound beams according to examples of the present disclosure are shown. The left column (panes 1302, 1304, and 1306) shows images collected by beamforming and displaying B-mode images directly from raw channel signals. That is, the signals from each transducer element are independently processed by the main beamformer without microwave beamforming. The second column (panes 1308, 1310, and 1312) shows images collected by a typical microwave beamforming operation using a patch size of 5. The third column (panes 1314, 1316, and 1318) shows images generated by the raw signals compressed using a jitter sampling scheme and reconstructed according to the principles of the present disclosure. The top row (panes 1302, 1308, and 1314) shows images from a simulated phantom beamformed from one divergent transmission wave. The middle row (panes 1304, 1310, and 1316) shows images from a simulated phantom beamformed from 11 divergent wave transmissions (middle row). Both the top row images and the middle row images were acquired using a 50 mm focal spot.The bottom row (panes 1306, 1312, and 1318) shows images from an in vivo cardiac dataset generated from 16 diverging wave transmissions and a 50 mm focal spot.

[0086] like Fig.13As shown, the jittered sampling scheme used to encode and decode the RF data significantly improves the final image compared to conventional microwave beamforming. Improvements are achieved in both contrast and reduction in grating lobe artifacts obtained using jittered sampling reconstruction beamforming. For example, the grating lobe artifacts in the circle 1320 in pane 1308 do not appear in the reconstructed image of pane 1314. In the case of eleven shots, these grating lobe artifacts are not as obvious as in the case of a single shot because they are slightly reduced by angular compounding with the other shots. However, in another example of an improved scheme demonstrated by the principles of the present disclosure, the grayscale inside the hypoechoic cyst 1322 of pane 1310 is increased and the overall contrast is reduced compared to pane 1316. This avoids grating lobe artifacts and reduced contrast artifacts of the microwave beamformed image, and an image closer to that obtained by beamforming from per-channel data is obtained using the jittered sampling and reconstruction scheme described herein. For Fig.13 For all dithered reconstructed images shown, the covariance matrix was estimated from synthetic data including in vivo cardiac data.

[0087] Finally, in the heart example in the bottom row, even the per-channel beamformed image in pane 1306 has some clutter in the regions corresponding to the heart chambers. However, with the microwave beamformed image in pane 1312, the overall image contrast is low due to the large amount of clutter introduced by the microwave beamforming process. In the image generated by the dithered sampling and reconstruction scheme in pane 1318, there is no clutter and reduction in contrast.

[0088] As described herein, a jitter sampling scheme can be used with a microbeamformer to encode RF data received from a transducer element. The encoded signal can be transmitted to a decoder for reconstruction of the original RF data. The encoding can allow less data to be transmitted between the ultrasound probe and the imaging system base. The encoding and reconstruction can allow improved image generation (e.g., via beamforming or other methods) compared to images generated according to typical microbeamforming operations. The systems, methods, and apparatus described herein can allow the use of unfocused beam imaging (e.g., plane wave, diverging wave) performed using an ultrasound probe including a microbeamformer.

[0089] In various embodiments where components, systems and / or methods are implemented using a programmable device (e.g., a computer-based system or a programmable logic unit), it should be understood that the above-described systems and methods can be implemented using various known or later developed programming languages ​​(e.g., "C", "C++", "FORTRAN", "Pascal", "VHDL", etc.). Accordingly, various storage media (e.g., computer disks, optical disks, electronic memory, etc., which can contain information capable of directing a device such as a computer) can be prepared to implement the above-described systems and / or methods. Once the appropriate device has access to the information and programs contained on the storage medium, the storage medium can provide the information and programs 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 appropriate materials (e.g., source files, object files, executable files, etc.) is provided to a computer, the computer can receive the information, configure itself appropriately and perform the functions of the various systems and methods outlined in the above diagrams and flow charts, thereby implementing the various functions. That is, the computer can receive portions of the various information related to the different elements of the above-described systems and / or methods from the disk, implement the various systems and / or methods, and coordinate the functions of the various systems and / or methods described above.

[0090] 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 / or firmware. In addition, various methods and parameters are included only as examples without any limiting meaning. In view of the present disclosure, those of ordinary skill in the art can implement this teaching to affect these technologies when determining their own techniques and required instruments while remaining within the scope of the present invention. The functions of one or more processors in the processor described herein can be incorporated into a smaller number or a single processing unit (e.g., CPU), and can be implemented using an application specific integrated circuit (ASIC) or a general processing circuit that is programmed to perform the functions described herein in response to executable instructions.

[0091] Although the present system has been described with specific reference to an ultrasound imaging system, it is also contemplated that the present system can be extended to other medical imaging systems in which one or more images are obtained in a systematic manner. Thus, the present system can be used to obtain and / or record image information relating to, but not limited to, the kidneys, testes, breasts, ovaries, uterus, thyroid, liver, lungs, musculoskeletal, spleen, heart, arteries, and vascular systems, as well as other imaging applications associated with ultrasound-guided interventions. In addition, the present system can also include one or more programs that can be used with a conventional imaging system, such that the one or more programs can provide the features and advantages of the present system. After studying the present disclosure, a person skilled in the art can easily conceive of certain additional advantages and features of the present disclosure, or a person skilled in the art can experience certain additional advantages and features of the present disclosure after adopting the novel systems and methods of the present disclosure. Another advantage of the present system and method can be that a conventional medical imaging system can be easily upgraded to incorporate the features and advantages of the present system, apparatus, and method.

[0092] Of course, it should be understood that any of the examples, embodiments, or processes described herein may be combined with one or more other examples, embodiments, and / or processes, or may be separated in devices or device portions according to the present systems, devices, and methods, and / or performed in devices or device portions according to the present systems, devices, and methods.

[0093] Finally, the above discussion is intended only to illustrate the present system and method and should not be construed as limiting the claims to any particular embodiment or group of embodiments. Therefore, although the present system has been described in detail with reference to exemplary embodiments, it should also be understood that a person of ordinary skill in the art may devise numerous modifications and alternative embodiments without departing from the broader and intended spirit and scope of the present system and method as set forth in the claims. Accordingly, the description and drawings should be regarded as illustrative rather than limiting the scope of the claims.

Claims

1. A system comprising: a transducer array comprising a plurality of transducer elements divided into tiles, wherein the transducer elements are configured to receive ultrasound echoes and convert the ultrasound echoes into electrical signals; a microwave beamformer coupled to the plurality of transducer elements, the microwave beamformer comprising: a first delay line coupled to a first transducer element of the plurality of transducer elements, wherein the first delay line comprises a first plurality of memory cells configured to store the electrical signal received from the first transducer element; and a second delay line coupled to a second transducer element of the plurality of transducer elements, wherein the second delay line comprises a second plurality of memory cells configured to store the electrical signal received from the second transducer element; wherein, for each transducer element, each delay line comprises a plurality of memory cells for storing time samples of the electrical signal; wherein the microbeamformer is configured to perform dither sampling on the electrical signals stored in the first plurality of memory cells and the second plurality of memory cells and generate dither signals; wherein, for each tile, the time samples for each transducer element of the tile are selected from the plurality of memory cells of the delay line according to a set of pseudo-random sampling patterns or a jittered sampling scheme, and then the selected time samples are summed; and A decoder is configured to receive the dithering signal and generate a reconstructed signal representative of the electrical signal. 2 . The system of claim 1 , further comprising a main beamformer configured to generate a beamformed signal based at least in part on the reconstructed signal.

3. The system according to claim 1, wherein: The microbeamformer is configured to generate the dithering signal by pseudo-randomly summing the electrical signals sampled from the first and second pluralities of memory cells.

4. The system according to claim 1, wherein: The microbeamformer is configured to dither sample the electrical signals stored in the first and second pluralities of memory cells using a pseudo-random pattern of time sample periods.

5. The system according to claim 4, wherein: The time sample periods of the pseudo-random pattern are configured such that individual memory cells of the first plurality of memory cells and the second plurality of memory cells are sampled no more than once per storage cycle.

6. The system according to claim 1, wherein: The first delay line is a programmable delay line.

7. The system according to claim 1, wherein: The first plurality of memory cells is configured as a circular buffer.

8. The system of claim 1, further comprising a main beamformer, the main beamformer comprising the decoder.

9. The system of claim 1, further comprising a transmission controller, wherein: The transmit controller provides a delay to be added to the dither signal by the microbeamformer to focus or steer a beam associated with the ultrasound echo.

10. A method comprising: acquiring a plurality of time samples of an electrical signal from a transducer array of tiled transducer elements, wherein the electrical signal is correlated with the acoustic signal; storing the plurality of time samples in a plurality of memory cells, wherein individual memory cells of the plurality of memory cells store individual time samples of the plurality of time samples, wherein, for each transducer element, each delay line comprises a plurality of memory cells for storing the time samples of the electrical signal; pseudo-randomly selecting a subset of the plurality of memory cells from the plurality of memory cells according to a set of pseudo-random sampling patterns or a dithered sampling scheme, wherein the subset includes fewer memory cells than the plurality of memory cells; summing the individual time samples of the plurality of time samples stored in the subset of the plurality of memory cells to generate a dithering signal; and The dithered signal is decoded to generate a reconstructed signal.

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