Abstract: In order to make both the maintenance of a scan range and a frame rate for ultrasonic imaging and high definition of an image compatible with each other, a sound-ray density for scan is made nonuniform, and a sound-ray density is rendered dense at a required portion and coarse at portions other than the portion.

Abstract: An ultrasound machine that generates a color representation of moving structure, such as cardiac wall tissue within a region of interest, and is displayed on a monitor. The color representation is generated by displaying at least one color characteristic related to a set of signal values of the structure, such as velocity or strain rate. The related feature of the set of signal values is mapped to the color characteristic by an apparatus comprising a front-end that generates received signals in response to backscattered ultrasound waves. A Doppler processor generates a set of signal values representing a spatial set of values of the moving structure. A host processor embodies a tracking function and a time integration function to generate tracked movement parameter profiles and displacement parameter values over a time period corresponding to sampled anatomical locations within the region of interest. The displacement parameter values are then mapped to color characteristic signals.

Abstract: The present invention is a method of and system for imaging an object with an ultrasound transducer array that transmits ultrasound beams and detects echoes reflected from the object. A plurality of adjacent ultrasound beams are transmitted at the object, each of the beams being separated from an adjacent beam by a first predetermined distance. A plurality of groups of echoes are received from the object, with each of the groups of echoes corresponding to one of the plurality of the ultrasound beams. Each of these echoes are spaced from the corresponding ultrasound beam by a second predetermined distance which is less than the first predetermined distance. The transmitted ultrasound beams are arranged such that one of the received echoes corresponding to an ultrasound beam substantially overlaps with one of the received echoes corresponding to an adjacent ultrasound beam. At least a subset of the received echoes are then processed to obtain B-mode data from each of the processed echoes.

Abstract: An ultrasonic imaging system uses a specially configured scanhead to provide ultrasound return signals that are processed by an imaging unit to generate a three-dimensional Doppler ultrasound image. One embodiment of the scanhead includes a first pair of apertures aligned along a first axis, and a second pair of apertures aligned along a second axis that is perpendicular to the first axis. All of the apertures lie in a common plane. Respective signals from the apertures along each axis are processed to generate two-dimensional Doppler motion vectors. The resulting pairs of two-dimensional Doppler motion vectors are then processed to generate three-dimensional Doppler motion vectors that are used to generate a three-dimensional Doppler image. In another embodiment, three co-planar apertures are arranged equidistantly from each other about a common center, and the three-dimensional Doppler image is generated from respective signals from the apertures.

Abstract: In an intravascular ultrasonic (IVUS) imaging system ring-down artifact is reduced or eliminated by dynamically enhancing the ring-down over a plurality of scans, determining the ring-down range by keying on a ring-down-to-blood transition characterized by a rapid change from high amplitude to low amplitude echoes, and using a spectral pattern for a single or several A-scans within the ring-down range, using for example an FFT analysis, as the basis of selectively filtering current or subsequent images using the recently computed ring-down pattern.

Abstract: In order to properly discern a plurality of streams of blood flow having different contrast agent arrival times or blood concentration properties, an ultrasonic diagnostic apparatus 200 comprises: an ultrasonic probe 1; a transceiver section 2; a quadrature detector section 3; a power calculating section 4 for calculating the power P of blood flow; a power peak holding section 21 for comparing the latest power P and a predecessor peak value Po, and outputting the larger one as a peak value P′ and an elapsed time t′ corresponding to the peak value P′; a predecessor power/elapsed time keeping section 22 for keeping the predecessor peak value Po and the corresponding elapsed time ‘to’ and outputting these values to the power peak holding section 21; a timer 11 for measuring an elapsed time t from a reference time; a blood flow image producing section 25 for producing a power peak hold blood flow image G2 in which the hue is changed before and after the elapsed time t′ reaches

Abstract: An ultrasound system that performs image processing in the digital domain, including CW Doppler. The ultrasound system is provided with a transducer having a plurality of elements and an ultrasound receiver with a plurality of channels. Each channel receives an analog echo signal and outputs a digital representation of the analog echo signal using an A/D converter capable of converting a signal with a dynamic range of at least 154 dB.

Abstract: Ultrasound images are obtained using a set of Golay codes with orthogonal property as ultrasound receiving and transmitting signals. Ultrasound signals having a plurality of codes are transmitted simultaneously by using the orthogonal property of the Golay codes. A superior signal-to-noise rate (SNR) is realized using the Golay codes, without suffering a decrease in the frame rate.

Abstract: Techniques are provided for obtaining selected instantaneous area measurements for a dynamic orifice through which blood is flowing in at least one direction, for obtaining instantaneous flow rates of blood passing through such a dynamic orifice and for obtaining flow volume for blood passing through a dynamic orifice. All of these techniques involve ensonifying a thin sample volume of blood flow exiting at the orifice, which volume is in a region of flow which is substantially laminar, such region normally being the vena contracta for the orifice, with an ultrasonic pulsed Doppler signal, receiving backscattered signal from blood within the sample volume and forming a power-velocity spectrum from the received backscattered signal. Techniques are disclosed for assuring that only laminar flow is looked at in forming the power-velocity spectrum.

Abstract: Nonlinear tissue or contrast agent effects are detected by combining echoes from multiple, differently modulated transmit pulses below the second harmonic band. The received echoes may even overlap the fundamental transmit frequency band. The modulation may be amplitude modulation or phase or polarity modulation, and is preferably both amplitude and phase or modulation. The present invention affords the ability to utilize a majority of the transducer passband for both transmission and reception, and to transmit pulses which are less destructive to microbubble contrast agents.

Abstract: A method is provided to simultaneously acquire two ultrasound images. A first set of ultrasound pulses are transmitted at a first frame rate utilizing a first mode of operation. The echoes from the first set of ultrasound pulses are received. A second set of ultrasound pulses are transmitted at a second frame rate utilizing a second mode of operation. The first and second frame rates are different. The first set of ultrasound pulses defines an entire image, while the second set of ultrasound pulses defines a partial image. The echoes from the second set of ultrasound pulses are received, and the echoes from the first and second sets of ultrasound pulses are displayed as a single image.

Abstract: An ultrasound diagnostic apparatus and method for measuring a blood flow velocity effectively select one of the positive frequency range and the negative frequency range to compute noise threshold, and determine a reliability of the computed noise threshold. A sample data generator samples a reflected signal of the ultrasound signal transmitted into a human body. A frequency distribution data generator processes the sample data, and generates a frequency distribution data including a number of frequency components. A first determiner selects one of a positive frequency range and a negative frequency range of the frequency distribution data. A second determiner determines a noise threshold by using a predetermined number of frequency components within the frequency range selected by the first determiner. A third determiner determines a peak frequency component having the highest frequency among the frequency components.

Abstract: An ultrasound imaging system capable of generating a flow image from B-mode echo frames. For each location in a target region, phase information is derived from the B-mode echo frames, and frame-to-frame changes in the phase information are processed to detect the presence of fluid flow at that location. A demodulator receives the B-mode echo frames and demodulates them into baseband signal components from which the phase information is derived. Preferably, the demodulator is highly accurate and robust, such that frame-to-frame changes in the phase information are reliably measured. From the reliably measured phase information, a phase shift metric is then computed and thresholded by a user-adjustable threshold value. Flow is present if the phase shift metric is greater than the threshold value and is absent otherwise.

Abstract: This invention relates to estimating the amount of blood flowing to the tissues of the kidney. More particularly, the invention is related to analyzing obtained power Doppler ultrasound images taken of the kidney and even more specifically of the kidney cortex tissue to produce a numerical value that correlates to the blood flow.

Abstract: An ultrasonic diagnostic imaging apparatus and method are provided for segmenting signals from nonlinear targets such as microbubble contrast agents. Received echo signals are separated into their constituent linear and nonlinear components by a Doppler filter using pulse inversion separation. A threshold level is derived from an estimate made of the contributions to the echo signal from linear scattering and noise. Echo signals which exceed the threshold level are segmented as nonlinear (microbubble-originating) signals and displayed as such, whereas signals not exceeding the threshold are suppressed in the image display.

Abstract: An ultrasound color flow imaging system is programmed to optimize display images on a display monitor (18) by automatically adjusting a threshold. B-mode data corresponding to valid color data is subjected to statistical analysis including mean and standard deviation (S3). The threshold is computed according to mean plus k (standard deviation), where k preferably is based on a linear regression equation.

Abstract: A rendering system includes a rendering unit (2) and a data processing unit (1) for the processing of a multi-dimensional object data set. The data processing unit is arranged to sample a surface model of the object data set. The successive representations of the surface model from the respective viewing directions are shown on the rendering unit. For the last viewing direction indicated, that is, the final direction, the representation of the multi-dimensional object data set is shown as viewed from the final direction.

Abstract: In order to obtain an optimum PRF, the velocity distribution of an echo source is calculated based on the Doppler shift of an ultrasonic wave echo, the profile of the velocity distribution is calculated (172), the reflection of the profile is corrected (174), the maximum value of the velocity in the corrected profile is detected (176), and the PRF of the ultrasonic wave transmission is adjusted based thereon (178).

Abstract: A high-speed non-invasive method and apparatus for detecting and measuring arterial stenosis without requiring imaging is disclosed. A Doppler ultrasound system automatically and repeatedly scans an area of interest to construct at least one velocity profile through segments of arteries over an area of interest. The velocity profiles and delta velocity profiles are automatically analyzed to determine a number of parameters indicative of potentially stenotic areas within the artery. These parameters may include: i) the average or peak velocity across the velocity profile, ii) the peak delta velocity across the velocity profile, iii) blunt flow present in the velocity profile, iv) turbulence in the blood flow, and v) the degree of skew in the velocity profile. The delta velocity profile defined as the change in the velocity profile with respect to the length of the artery is used to examine how the above parameters change along the length of the artery.

Abstract: An ultrasound scanning system (10) includes a plurality of range gates (71-74) responsive to ultrasound waves for generating a plurality of Doppler signal samples representing different depth increments within a subject (S) being studied. A logic unit (30) generates Doppler frequency signals and generates B-mode data. A display (60) generates a B-mode image and a Doppler image which may be superimposed on the B-mode image. The Doppler image (DI) is arranged to illustrate depth increments within the subject being studied versus Doppler velocity or frequency.

Abstract: A pulse wave detection device capable of accurately detecting pulse waves without influence of noise caused by hand movement or the like has a main sensor disposed on a radial artery and having an emitter for emitting an ultrasonic signal toward the radial artery and a receiver for receiving a reflected ultrasonic signal, and an auxiliary sensor disposed on an ulnar artery and having an emitter for emitting an ultrasonic signal toward the ulnar artery and a receiver for receiving a reflected ultrasonic artery. If the amplitude of an ultrasonic signal received by the main sensor is not between two threshold values, it is determined that detection of pulse waves from the radial artery is difficult. Then detection of pulse waves from the ulnar artery is performed by using the auxiliary sensor. After the lapse of a predetermined period of time from the start of detection using the ulnar artery, the main sensor is again selected to be used.

Abstract: A method for automatically placing a range gate over a moving blood vessel during ultrasound imaging. Doppler data received from a number of depths in the tissue is analyzed in order to calculate the average velocity of the tissue at each depth. A search is performed in the average velocities to select a maximum velocity. The maximum velocity is associated with a blood vessel and a range gate is placed at a depth corresponding to the maximum velocity. In a presently preferred embodiment of the invention, the average velocity is calculated by performing a first lag autocorrelation of the echo data received from each depth in response to a series of Doppler pulses.

Abstract: A hand held ultrasonic instrument is provided in a portable unit which performs both B mode and Doppler imaging. The instrument includes a transducer array mounted in a hand-held enclosure, with an integrated circuit transceiver connected to the elements of the array for the reception of echo signals. A digital signal processing circuit performs both B mode and Doppler signal processing such as filtering, detection and Doppler estimation, as well as advanced functions such as assembly of multiple zone focused scanlines, synthetic aperture formation, depth dependent filtering, speckle reduction, flash suppression, and frame averaging.

Abstract: A method and an apparatus for automatically maintaining the Doppler sample gate position at a preselected vessel position in B-mode or color flow images during tissue or probe motion. The sample gate is locked onto the selected vessel automatically when the vessel position has changed. Optionally, the vessel slope cursor is automatically updated when the vessel position has changed. The method employs pattern matching of images from successive frames to determine how much a vessel in the image frame has been translated and rotated from one frame to the next. Preferably, either a cross-correlation method is applied to the imaging data in the spatial domain to determine the relative object translation and/or rotation between image frames, or a matched filtering method is applied to the imaging data in the frequency (i.e., Fourier) domain to determine the relative object translation and/or rotation between image frames.

Abstract: The present invention relates generally to systems and methods for assessing blood flow in blood vessels, for assessing vascular health, for conducting clinical trials, for screening therapeutic interventions for adverse effects, and for assessing the effects of risk factors, therapies and substances, including therapeutic substances, on blood vessels, especially cerebral blood vessels, all achieved by measuring various parameters of blood flow in one or more vessels and analyzing the results in a defined matter. The relevant parameters of blood flow include mean flow velocity, systolic acceleration, and pulsatility index. By measuring and analyzing these parameters, one can ascertain the vascular health of a particular vessel, multiple vessels and an individual. Such measurements can also determine whether a substance has an effect, either deleterious or advantageous, on vascular health. In one of many embodiments, the present invention further provides an expert system for achieving the above.

Abstract: A method for producing Doppler ultrasound data at a user-requested pulse repetition frequency (PRF) utilizing undersampled echo signals. Echo signals are created in response to Doppler pulses that are transmitted into the patient at a rate less than a desired PRF. The echo signals are analyzed in the time domain to determine a velocity of scatterers in an area of tissue defined by a range gate. From the velocity, the Doppler shift of the scatterers is determined. The echo signals are interpolated to produce a number of samples equal in number to that which would have been produced had the Doppler pulses been transmitted at the user-requested PRF. The interpolated echo signals are then analyzed in the frequency domain which produces a number of spectra indicative of the velocity and direction of the moving scatterers. From the Doppler shift determined, the correct spectra is selected and displayed for a user.

Abstract: A method for the delivery of substances to a cell is disclosed. In a preferred embodiment, one administers continuous wave ultrasound or pulse-wave ultrasound to a cell bathed in a cocktail containing macromolecules and monitors the ultrasound using reflected echos of the ultrasound. One then observes incorporation of the substances into the cell. In a preferred embodiment of the present invention, macromolecules are combined in a cocktail solution comprising bubble micronuclei.

Abstract: In order to capture an image representing pulsation strength in moving velocity of an echo source, a moving velocity V of the echo source is detected based on the Doppler shift in an ultrasonic echo, and a pulsation strength P in the moving velocity V is detected at a pulsation detecting means 132 by a calculation that employs a value Vn of the moving velocity V at a current time phase and a value Vo of the moving velocity V at a past time phase.

Abstract: An ultrasonic diagnostic imaging system is provided with synthesized transmit focus. Several beams are transmitted, each with a different transmit focus. Echoes received from the differently focused beams are combined to form a scanline with an extended focus. The echoes are preferably weighted and/or phase adjusted prior to being combined. Combining is performed in the r.f. domain before nonlinear processing of the signals such as amplitude detection. The resultant extended focus scanline exhibits the property of dynamic transmit focusing.

Abstract: A method and system for generating data for a spectral Doppler strip in an ultrasound system includes a beamformer that provides Doppler data to a signal processor. The signal processor applies an autoregressive model and determines autoregressive parameters responsive to the Doppler data. Information responsive to the autoregressive parameters is generated, and a window function is applied to the information. At least one spectrum responsive to the auto-regressive parameter is estimated with a Fourier transform.

Abstract: A method and an apparatus for adaptive wall (high-pass) filtering to remove low-frequency clutter in spectral Doppler I/Q data prior to FFT processing. The I/Q data is passed through a low-pass filter which rejects the flow frequency components above the clutter frequency range. The total power of the low-pass filter output is then computed. A system noise model is used to predict the mean system noise power in the low-pass filter output. The predicted mean noise power provides a noise threshold to gage how much clutter power is present in the current FFT packet. If no significant clutter is present, then wall filter selection logic will automatically select the lowest wall filter cutoff frequency stored in a filter coefficient LUT. If significant clutter power is present in the FFT packet, then the mean and variance of the clutter frequency over the FFT packet are estimated and then input into the filter selection logic, which selects the most suitable filter cutoff for the current clutter signal.

Abstract: A multifocus ultrasonic imaging system transmits two or more successive multifocus beams in order to increase the number of separate focal zones along a given scan line. The operating conditions for different transmit foci are controlled in a multifocus transmit event in order to optimize the operating conditions for each transmit focus and to reduce the unwanted transmit foci interference. In one example, two consecutive multifocus transmit events are transmitted and the transmit focal zones of the first and second transmit events are interleaved in range, thereby increasing the separation between transmit focal zones within a single transmit event.

Abstract: A method and an apparatus for suppressing background noise in spectral Doppler imaging using adaptive noise-reduction low-pass filters. A pair of adaptive low-pass filters are arranged in the two audio Doppler channels for suppressing background noise in the audio Doppler data. The low-pass filtering can be implemented in the frequency domain, i.e., before the IFFT operation, or in the time domain, i.e., after the IFFT operation. Maximum frequency traces are fed into a filter selection block which prescribes the filter cutoffs of the low-pass filters.

Abstract: A demodulator for use in an ultrasound information processing system is described, where in a preferred embodiment the demodulator uses a half-band filter to perform mirror-cancellation during the demodulation process. The demodulator comprises a mirror canceling quadrature mixer that mixes the input signal with quarter-sampling-frequency sinusoids and then low-pass-filters the mixed signals with half-band filters having a cutoff frequency of one-fourth the sampling frequency. In an ultrasound demodulator in accordance with a preferred embodiment, a significantly sharper mirror cancellation on the wideband input signal is achieved. Additionally, the number and complexity of mirror canceling filter operations significantly reduced, allowing for easier hardware implementation using less expensive, off-the-shelf components. Furthermore, simplified hardware for digitally providing harmonic imaging applications is achieved.

Abstract: A method and apparatus for quantifying and displaying ultrasound signals in an ultrasonic system are provided. A first signal value for each of at least one spatial location in a region of interest is acquired at a first time, and the signal values are summed to obtain a first surface integral value. A second signal value for each of said at least one spatial location in said region of interest is acquired at a second time, and the second signal values are summed to obtain a second surface integral value. The first surface integral value is summed with the second surface integral value to obtain a time based integral. The time based integral is displayed. Other quantities based on any of various ultrasound parameters, such as Doppler energy, Doppler velocity and B-mode intensity, are calculated and displayed as quantities or as waveforms as a function of time. Furthermore, various comparisons of quantities and waveforms are provided. Image plane data or other ultrasound data are used in the calculations.

Abstract: The method of the invention controls an ultrasound system that implements a clutter filter, to derive parameters such as blood flow velocity, echo power and/or echo amplitude data from an anatomical region of interest (ROI) and into which a contrast agent has been introduced. The method initially transmits an ensemble of N ultrasound beams along a common azimuth and elevation into the ROI to cause destruction of the contrast agent lying along the azimuth. Estimated wall motion velocity data is then derived for the tissue wall region through use of selected echo signal data derived from a subset of the N ultrasound beams of the ensemble, the subset excluding echo signal data from a first M of the N ultrasound beams or any subset of the N ultrasound beams. The clutter filter is then adjusted to attenuate selected echo signal data returned from the ROI that exhibits the wall motion velocity data.

Abstract: An ultrasonic imaging system includes an ultrasonic transducer having an image data array and a tracking array at each end of the image data array. The tracking arrays are oriented transversely to the image data array. Images from the image data array are used to reconstruct a three-dimensional representation of the target. The relative movement between respective frames of the image data is automatically estimated by a motion estimator, based on frames of data from the tracking arrays. As the transducer is rotated about the azimuthal axis of the image data array, features of the target remain within the image planes of the tracking arrays. Movements of these features in the image planes of the tracking arrays are used to estimate motion as required for the three-dimensional reconstruction. Similar techniques estimate motion within the plane of an image to create an extended field of view.

Abstract: A pressure volume loop of the heart of a patient is obtained utilizing an electrocardiograph and a brachial-artery pressure cup pressure-measurement system having an echo-Doppler sensor positioned to measure the flow waves at the aortic root.

Abstract: A flow display method enabling the state of flows in a plane to be grasped together with inflow into and outflow from that plane. A Doppler method, for example, is used to obtain a velocity profile at each point in a planar area (100) of interest defined in a three-dimensional flow. A flow rate profile in the planar area (100) is found on the basis of the thus obtained velocity profile. From the flow rate profile and the velocity profile there are determined source points (12) representative of inflow into the planar area (100) and sink points (14) representative of outflow therefrom. Contour lines in the flow rate profile then join the source points (12) and the sink points (14) to obtain a display of planar streamlines (10).

Abstract: An ultrasonic imaging system for displaying velocity of fluid includes a receiver which demodulates ultrasonic echo signals received by a transducer array from two different positions. The resulting data is organized into frames of data from the two different positions. The data is used to calculate the angle of rotation between the frames. The fluid flow velocity then is calculated from the frames of data and the angle of rotation.

Abstract: A method and apparatus for quantifying and displaying ultrasound signals in an ultrasonic system are provided. A first signal value for each of at least one spatial location in a region of interest is acquired at a first time, and the signal values are summed to obtain a first surface integral value. A second signal value for each of said at least one spatial location in said region of interest is acquired at a second time, and the second signal values are summed to obtain a second surface integral value. The first surface integral value is summed with the second surface integral value to obtain a time based integral. The time based integral is displayed. Other quantities based on any of various ultrasound parameters, such as Doppler energy, Doppler velocity and B-mode intensity, are calculated and displayed as quantities or as waveforms as a function of time. Furthermore, various comparisons of quantities and waveforms are provided. Image plane data or other ultrasound data are used in the calculations.

Abstract: A method and device for determining a plurality of cardiovascular parameters are described, wherein the parameters are determined from noninvasively obtained data, thereby obviating the need for invasive procedures such as cardiac catheterization. These determinations are enabled by incorporating fluid dynamics and thermodynamics equations with nonivasively obtained mechanical cardiac event data to estimate a desired cardiovascular parameter. Exemplary parameters obtainable with the method and device include aortic and mitral valve areas, cardiac left ventricular stroke volume, and aortic and mitral valve pressure gradients.

Abstract: A hand held ultrasonic instrument is provided in a portable unit which performs both B mode and Doppler imaging. The instrument includes a transducer array mounted in a hand-held enclosure, with an integrated circuit transceiver connected to the elements of the array for the reception of echo signals. A digital signal processing circuit performs both B mode and Doppler signal processing such as filtering, detection and Doppler estimation, as well as advanced functions such as assembly of multiple zone focused scanlines, synthetic aperture formation, depth dependent filtering, speckle reduction, flash suppression, and frame averaging.

Abstract: An ultrasonic imaging system for displaying color flow images includes a receiver which generates color flow signals corresponding to frames obtained from different pulse repetition rates and different numbers of transducer stimulations per beam position. The color flow signals are selected and combined to enable visualization of fluid (e.g., blood) flow dynamics while maintaining segmentation of fluid flow from other tissue.

Abstract: A method for increasing the valid data points produced by a digital filter. Input data is applied to a pair of filters that produce transients in response to different input data values. Output data from each of the filters is then combined to produce a data set with no transients. In one embodiment, the pair of filters have the same impulse response but the input data is applied to one filter in a first direction and to the other filter in an opposite direction. In another embodiment, the input data is applied to both filters in the same direction but the filters have inverted impulse responses. The present invention is particularly useful for minimizing a gap created when an ultrasound system alternates between different imaging modes. In addition, the present invention, can be used to increase the number of valid data points that are analyzed during color flow ultrasound imaging.

Abstract: An ultrasonic imaging system for displaying color flow images includes a receiver which demodulates ultrasonic echo signals received by a transducer array and dynamically focuses the baseband echo signals. A color flow processor includes a plurality of logic units which perform different algorithms based on the type of examination being conducted.

Abstract: A method and an apparatus for improving the signal-to-noise ratio (SNR) and/or resolution in color flow ultrasound imaging by using complementary-coded excitation of the transducer array. The SNR is improved by transmitting a pair of Golay-coded pulse sequences in alternating sequence at the same transmit focal position over multiple firings and then partly decoding the beamsummed data. The partly decoded data is then vector summed and high pass filtered. The summed and high-pass-filtered data is optionally decimated by a factor of two. The decimated or undecimated data is then input to the parameter estimator, which provides imaging signals representing the flow in a scan plane. Those imaging signals are then displayed as color information on a display monitor.

Abstract: An ultrasound color flow imaging system is programmed to optimize display images of power and velocity by automatically adjusting thresholds by using histograms and samplings of color flow data.

Abstract: According to the present invention, a method and apparatus rely upon tomographic measurement of the speed of sound and fluid velocity in a pipe. The invention provides a more accurate profile of velocity within flow fields where the speed of sound varies within the cross-section of the pipe. This profile is obtained by reconstruction of the velocity profile from the local speed of sound measurement simultaneously with the flow velocity. The method of the present invention is real-time tomographic ultrasonic Doppler velocimetry utilizing a to plurality of ultrasonic transmission and reflection measurements along two orthogonal sets of parallel acoustic lines-of-sight. The fluid velocity profile and the acoustic velocity profile are determined by iteration between determining a fluid velocity profile and measuring local acoustic velocity until convergence is reached.

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.