Abstract: A method for real-time displaying of cross-sectional images during an intravascular ultrasound (IVUS) imaging procedure includes, during an intravascular ultrasound imaging procedure, receiving electrical signals from at least one transducer in a catheter as the at least one transducer rotates and moves longitudinally along a lumen of a patient blood vessel; during the intravascular ultrasound imaging procedure, processing the received electrical signals to form a series of cross-sectional images that are longitudinally-offset from one another along a length of the lumen; during the intravascular ultrasound imaging procedure, concurrently displaying i) a most recent image and ii) a previous image that is either a) selected by the operator or b) automatically selected as having a maximum or minimum of a selected image characteristic; and, during the intravascular ultrasound imaging procedure, updating the display of the most recent image as a new image from the series of cross-sectional images is processed.

Abstract: A medical imaging assembly includes an elongated catheter having a connector at the proximal end; an array of transducers on the distal end of the catheter; conductors electrically coupled to the array of transducers and in electrical communication with the connector of the catheter; and a control unit coupleable to the catheter to send and receive electrical signals between the control unit and the array of transducers through the connector of the catheter. The control unit has a processor to execute instructions including 1) selecting a first subset of M transmitting transducers and a second subset of N receiving transducers from the array of transducers, where N>M; and 2) for each of at least N transmit/receive cycles, a) directing the first subset of M transmitting transducers to transmit an acoustic signal; and b) directing the second subset of N receiving transducers to receive corresponding echo signals.

Abstract: A method for real-time displaying of cross-sectional images during an intravascular ultrasound (IVUS) imaging procedure includes, during an intravascular ultrasound imaging procedure, receiving electrical signals from at least one transducer in a catheter as the at least one transducer rotates and moves longitudinally along a lumen of a patient blood vessel; during the intravascular ultrasound imaging procedure, processing the received electrical signals to form a series of cross-sectional images that are longitudinally-offset from one another along a length of the lumen; during the intravascular ultrasound imaging procedure, concurrently displaying i) a most recent image and ii) a previous image that is either a) selected by the operator or b) automatically selected as having a maximum or minimum of a selected image characteristic; and, during the intravascular ultrasound imaging procedure, updating the display of the most recent image as a new image from the series of cross-sectional images is processed.

Abstract: A method for processing a sequence of ultrasound frames for display includes receiving a sequence of intravascular ultrasound (IVUS) frames of a vessel having a lumen, the sequence including a first frame and a second frame; determining one or more texture features for each of one or more regions of the first frame; determining at least one flow feature for each of the one or more regions by comparing the first and second frames; deriving a lumen border for the first frame using the one or more texture features and the at least one flow feature to characterize the one or more regions as within or outside of the lumen of the vessel; and displaying an ultrasound image of the first frame with the lumen border.

Abstract: A medical imaging assembly includes an elongated catheter having a connector at the proximal end; an array of transducers on the distal end of the catheter; conductors electrically coupled to the array of transducers and in electrical communication with the connector of the catheter; and a control unit coupleable to the catheter to send and receive electrical signals between the control unit and the array of transducers through the connector of the catheter. The control unit has a processor to execute instructions including 1) selecting a first subset of M transmitting transducers and a second subset of N receiving transducers from the array of transducers, where N>M; and 2) for each of at least N transmit/receive cycles, a) directing the first subset of M transmitting transducers to transmit an acoustic signal; and b) directing the second subset of N receiving transducers to receive corresponding echo signals.

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: 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: 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.