The present disclosure describes ultrasound systems and methods configured to interrogate the stiffness and/or elasticity of a target tissue via shear wave imaging Systems may be configured to stroboscopically transmit a plurality of push pulses into the target tissue at different focal depths. The quickly transmitted push pulses may generate shear waves that constructively interfere to form a composite shear wave. Example systems may include a beamformer configured to transmit push pulse parameters to a transducer array while receiving new push pulse parameters from a controller. Dual transmission and receipt of different push pulse parameters reconfigures the beamformer without interrupting push pulse transmission, thereby minimizing the delay between successive push pulses. Push pulses transmitted according to the disclosed methods may generate a composite shear wave configured to interrogate tissue with enhanced sensitivity across a broad depth.

In an ultrasound imaging system which produces synthetically transmit focused images, the multiline signals used to form image scanlines are analyzed for speed of sound variation, and a map 60 of this variation is generated. In a preferred implementation, the phase discrepancy of the received multilines caused by speed of sound variation in the medium is estimated in the angular spectrum domain for the receive angular spectrum. Once the phase is estimated for all locations in an image, the differential phase between two points at the same lateral location, but different depth, is computed. This differential phase is proportional to the local speed of sound between the two points. A color-coded two- or three-dimensional map 60 is produced from these speed of sound estimates and presented to the user.

An ultrasound system according to the present disclosure may include a beamformer configured to perform per-channel weighting on the RF signals received at each channel in order to reduce noise clutter in the image. For this purpose, the beamformer may receive at one or more channels associated with an active aperture, sets of receive signals associated with respective transmit beams that at least partially overlap. The beamformer may alter the receive space, e.g., to align the sets of receive signals to a common location (e.g., between the transmit beams) and generate a coherence-based weighting value that may be indicative of blockage. The coherence-based weighting value may be applied on a per-channel basis to the receive signals. The beamformer may also communicate the coherence metric to the controller for altering the transmit space. In some such examples, the power output to one or more elements of the array may be adjusted based upon the per-channel weighting value or determined blockage of the aperture.

Front-end circuitry for an ultrasound system comprises a beamformer FPGA integrated circuit, transmit ICs with both pulse transmitters and linear waveform transmitters and T/R switches, transmit control and receiver ICs, and analog-to-digital converter (ADC) ICs. Only the transmit ICs require high voltages, and the transmit/receive switches are integrated in the transmit ICs, isolating the receiver ICs from high voltages. The transmitters can be trimmed to adjust the pulse rise and fall rates, enabling the transmission of pulses with low harmonic frequency content and thus better harmonic images.

An ultrasonic diagnostic imaging system scans a plurality of planar slices in a volumetric region which are parallel to each other. Following detection of the image data of the slices the slice data is combined by projecting the data in the elevation dimension to produce a “thick slice” image. Combining may be by means of an averaging or maximum intensity detection or weighting process or by raycasting in the elevation dimension in a volumetric rendering process. Thick slice images are displayed at a high frame rate of display by combining a newly acquired slice with slices previously acquired from different elevational planes which were used in a previous combination. A new thick slice image may be produced each time at least one of the slice images is updated by a newly acquired slice. Frame rate is further improved by multiline acquisition of the slices.

Estimation of vibration amplitude of intra-capillary micro-bubbles driven to vibrate with an incident ultrasound wave with amplitude and frequency to adjust the drive amplitude of the incident wave to obtain specified vibration amplitude of extra-capillary tissue. Estimation uses transmission of M groups of pulse complexes having low frequency pulse (LF) at bubble drive frequency, and high frequency (HF) pulse with angular frequency ω.sub.H>˜5ω.sub.L, and pulse duration shorter than π/4ω.sub.L along HF beam. The phase between HF and LF pulses is ω.sub.Lt.sub.m for each group, where t.sub.m varies between the groups. Within each group, LF pulse varies between pulse complexes in amplitude and/or, where the LF pulse can be zero for a pulse complex, and LF pulse is different from zero for pulse complex within each group. HF receive signals are processed to obtain a parameter relating to bubble vibration amplitude when the HF pulse hits bubble.

In an image compressing ultrasound system, for generating an imaging sample, delays are applied transducer-element-wise to respective time samples. The delayed samples are summed coherently in time, the coherently summed delays being collectively non-focused. An image is sparsified based on imaging samples and, otherwise than merely via said imaging samples, on angles (236) upon which respectively the delays for the generating of the imaging samples are functionally dependent. An image-compressing processor (120) may minimize a first p-norm of a first matrix which is a product of two matrices the content of one representing the image in a compression basis. The minimizing is subject to a constraint that a second p-norm of a difference between a measurement matrix and a product of an image-to-measurement-basis transformation matrix, an image representation dictionary matrix, and the matrix representing the image in the compression basis does not exceed an allowed-error threshold. The measurement matrix is populated either by channel data, or by output of a Hilbert transform applied to the channel data in a time dimension.

Fresnel elevation focusing at a selected elevation angle is performed by transmitting a sequential set of Fresnel-focused ultrasound pulses, where a different Fresnel phase pattern is used for each pulse, and where the receive signals are coherently compounded. The different Fresnel patterns cause the secondary lobe energy to be reduced via averaging of variations of the pressure fields in the secondary lobe regions. In some embodiments, the method of coherently compounded Fresnel focusing is combined with coherently compounded defocused wave (e.g. plane wave or diverging wave) imaging in the azimuth direction. Each of the elevation slices are collected by changing the Fresnel patterns respectively employed when the sequence of plane waves or diverging waves are transmitted, such that the coherent compounding can benefit both planes simultaneously. Hadamard receive encoding and subsequent dynamic receive beamforming may be employed to further improve performance in the elevation direction.

A two dimensional ultrasonic array transducer receives echo signals from increasing depths of a volumetric region. The 2D array is configured into patches of elements which are processed by a microbeamformer and summed signals from a patch are coupled to a channel of an ultrasound beamformer At the shallowest depth the 2D array receives echoes from small patches in the center of the aperture. As signals are received from increasing depths the aperture is grown by symmetrically adding patches of progressively larger sizes on either side of the small patches in the center. The inventive technique can improve the multiline performance of both 1D and 2D array probes.

Systems and methods for filtering an analog waveform before it is sampled by an analog-to-digital converter (ADC) in an ultrasound system are provided. The waveform can be filtered by delaying the same waveform by two different time delays and combining the delayed waveforms to effectively cancel out the fundamental components, thereby providing more sensitive detection of harmonic components in received echo signals. This filtering approach leverages an architecture that can also be used for multiline beamforming to perform the temporal filtering, in which a single acoustic signal can be read out of the ARAM twice, separated by time, taking advantage of the fact that the ARAM allows for non-destructive read operations.