Abstract: In performing three-dimensional flow imaging using coded excitation and wall filtering, a coded sequence of broadband pulses (centered at a fundamental frequency) is transmitted multiple times to a particular transmit focal position. On receive, the receive signals acquired for each firing are compressed and bandpass filtered to isolate a compressed pulse centered at the fundamental frequency. The compressed and isolated signals are then wall filtered to extract the flow imaging data. This process is repeated for a multiplicity of transmit focal positions in each of a multiplicity of scanning planes to acquire a volume of flow imaging data. Volume rendered images are then produced which allow the user to view the data volume from any angle. In addition, the data volume may be reformatted to produce two-dimensional images of arbitrary cut planes through the data volume.

Abstract: Coded excitation for medical ultrasound imaging is implemented by transmitting code or element symbols in the encoded base sequence on different firings. The encoded base sequence is formed by convolving a base sequence with an oversampled code sequence. For each firing the designated code or element symbol in the encoded base sequence is replaced by a unit symbol (i.e., 1 or -1) while the other symbol locations are all set to zero. After each transmit, the received waveform is multiplied by the respective symbols and accumulated to synthesize the received encoded waveform.

Abstract: A method and apparatus for improving the SNR in medical ultrasound imaging utilize Golay-coded excitation of the transducer array. A Golay pair is a pair of binary (+1,-1) sequences with the property that the sum of the autocorrelations of the two sequences is a Kronecker delta function. This translates into two important advantages over codes in general: (1) Golay codes have no range sidelobes, and (2) Golay codes can be transmitted using only a bipolar pulser versus a more expensive digital-to-analog converter. Degradation of the Golay code is avoided by employing multiple focal zones, where the Golay code is used only in the deepest focal zones in order to minimize dynamic focusing effects, and by employing two consecutive transmits on each beam to minimize tissue motion between the two code sequences.

Abstract: Signal-to-noise ratio in medical ultrasound imaging is improved by using Golay-encoded excitation of a transducer array. Two orthogonal Golay pairs of sequences are transmitted to respective transmit focal zones. Start of transmission of the Golay pair to the second zone is delayed until shortly after the start of transmission of the Golay pair to the first transmit focal zone such that the two pairs of firings are overlapped in time. The receive filtering follows two parallel paths, one for each focal zone. Each decoding filter (also used for bandpass filtering) supplies its output signal to a vector summer, the output signal of which is multiplexed to conventional B-mode processing (envelope detection, logarithmic compression and edge-enhancement filter), followed by scan conversion for display.

Abstract: A method and apparatus for ultrasonically imaging flow directly in B mode employs a sequence of pulses transmitted to a transmit focal position, with the backscattered signals from this sequence being filtered to remove echoes from stationary or slow-moving reflectors along the transmit path. The resulting flow signals are superimposed on a conventional B-mode vector and displayed. A B-mode flow image is formed by repeating this procedure for multiple transmit focal positions across the region of interest. The filtering is performed in slow time (along transmit firings) using a high-pass "wall" filter (e.g., an FIR filter) with harmonic image feed-through and optionally B-mode (fundamental) feed-through. The resulting B-mode flow image has low clutter from stationary or slow-moving tissue or vessel walls, high resolution, high frame rate and flow sensitivity in all directions.

Abstract: In a method and apparatus for ultrasound imaging of biological tissue using higher-order nonlinear signal components an ultrasound line is acquired at different excitation levels. The acquisition is repeated I times with identical beamforming parameters, but varying excitation level. All of the transmitted waveforms are nonlinearly distorted, but the degree of distortion depends on the excitation level, making it possible to extract individual nonlinear signal components by properly combining the received echo signals. A pre-computed estimation matrix, dependent on the order of an estimation model and the excitation levels, is stored in computer memory and used to compute the nonlinear components of interest. The real-time calculations reduce to a linear combination of the received echo signals. A further reduction in computational load can be achieved if one is interested in only the n-th-order nonlinear component.

Abstract: Signal-to-noise ratio in synthetic transmit aperture imaging is significantly increased by encoding the transmit signals in orthogonal complementary codes for multiple point sources to be transmitted simultaneously. A number N of elements of a transducer array are simultaneously activated to transmit unfocused ultrasound waves during each one of N transmit events. For each transmit event, a different set of N code sequences is applied by a controller to N pulsers for the transducers to drive the transducers. The imaging depth is divided into several zones and code lengths are employed which increase with depth. A Hadamard construct of the orthogonal complementary sets, which requires only 2N correlations for decoding, is used.

Abstract: A method and apparatus for improving the SNR in medical ultrasound imaging utilize Golay-coded excitation of the transducer array. A Golay pair is a pair of binary (+1,-1) sequences with the property that the sum of the autocorrelations of the two sequences is a Kronecker delta function. This translates into two important advantages over codes in general: (1) Golay codes have no range sidelobes, and (2) Golay codes can be transmitted using only a bipolar pulser versus a more expensive digital-to-analog converter. Degradation of the Golay code is avoided by employing multiple focal zones, where the Golay code is used only in the deepest focal zones in order to minimize dynamic focusing effects, and by employing two consecutive transmits on each beam to minimize tissue motion between the two code sequences.

Abstract: A method and an apparatus for selectively performing contrast harmonic imaging, tissue harmonic imaging and B-mode flow imaging with an ultrasound imaging system utilizes phase-coded excitation on transmit and selective firing-to-firing, i.e., "slow-time", filtering on receive. "Slow-time" filtering in combination with transmit phases which change over the set of transmit firings results in different effective "slow-time" filters corresponding to the different harmonic modes within the reflected signal. The transmit phases and the "slow-time" filter weightings are designed to selectively enhance the desired modes while substantially suppressing other modes.

Abstract: A multi-row ultrasound transducer array having a central row of transducer elements and a pair of outermost rows of transducer elements on opposing sides of the central row. The corresponding elements of the outermost rows are connected in parallel to a respective signal lead. The area of each element in the central row is less than the combined area of each pair of elements of the outermost rows. The greater total area of the combined elements of the outermost rows as compared to the area of each element of the central row provides improved elevation performance (thinner and more uniform image slice, greater contrast resolution), especially in the very near field, as compared to conventional transducers. The array may further include one or more pairs of rows of elements intermediate the central row and the respective outermost rows. The corresponding elements of the intermediate rows are connected in parallel to respective signal leads.

Abstract: The frame rate in medical ultrasound imaging is increased significantly by reducing the number of transmit events per image frame using spatially encoded transmit events in accordance with an invertible encoding matrix. First, M sets of encoded signals are transmitted, one set after the next, from M transmitting elements of a transducer array. For each transmission, all M transmitting elements are activated simultaneously in accordance with the encoding of a particular set of signals. The resulting scattering data are stored for each of the M transmit events, and are subsequently decoded with the inverse of the encoding matrix to obtain individual elemental information. The complete set of scattering data captures the time history of the ultrasound pulses that are transmitted from a single transducer element of the phased array, such as the m-th transmitter element, scattered by the medium under investigation, and subsequently received at the n-th receiver element, for all M transmitters and N receivers.