Abstract: In an ultrasound scanner (90), signals responsive to received ultrasound waves are processed by a B-mode processor (222) and a computer (232). The data processed by the B-mode processor (222) is used to generate a display of a reference image in an area (120) of a display (100), and the data processed by the computer (232) is used to generate a region of interest (140) of the reference image and an enlarged image corresponding to the region of interest in another area (150) of the display (100), thereby improving the spatial resolution and frame rate of the displayed images.

Abstract: A method and an apparatus for monitoring the wall signal input to the wall filter of a spectral Doppler processor to check for probe-motion-induced clutter. This clutter is typically of higher frequency and amplitude than that due to normal vessel wall motion. Some additional threshold logic is used to check for energy within a frequency band greater than the normal wall signal frequencies. If significant energy above some “rattle” threshold is detected for a predefined time interval, the Doppler audio is automatically muted. This can be effected at one or more points within the normal Doppler audio signal path in a conventional scanner. If the rattling clutter is no longer detected, the Doppler audio is re-activated or ramped up smoothly.

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: A method and an apparatus for automatically initializing and adjusting the Doppler sample gate position and size settings based on actual vessel image data. A vessel segment search method employs an object search technique based solely on geometric and morphological information in a binarized vessel image obtained from either B-mode or color flow image data. The morphologically best or nearest vessel segment within a target search region in the two-dimensional image is found. The sample gate is placed at or near the center of the targeted vessel segment. The sample gate size is adjusted in relation to the vessel size. Then the best available steering angle that minimizes the Doppler angle is selected.

Abstract: An ultrasound system determines the relative movement in a first direction (F1) of first matter, such as blood flow, and second matter, such as an artery wall, in a subject under study (S). A beam (B1) of ultrasound waves defining a plurality of beam positions (BP1 and BP2) and beam axes (A1and A2) are moved in scan directions having components parallel to direction F1. First and second blocks of data representing the first and second matter, respectively, are generated. A processor (20) performs an estimation of speckle size on first data to obtain a first result, and performs analysis of the second block of data to obtain a second result. The two results are analyzed to obtain a measure of the relative movement of the first and second matter.

Abstract: Method and apparatus for automatically detecting and sizing cystic objects in ultrasound imaging. The cystic objects can be automatically detected by the steps of reading an image frame from memory; defining a search region within the image frame or a decimated version of the image frame; binarizing the pixel values within the search region based on a pixel value threshold that is adaptive to local pixel value statistics; morphological filtering the binarized pixel values to eliminate structures smaller than the speckle size; counting the number of continuous objects and keeping track of their area; and rejecting objects that are outside a predetermined size range. Each detected cystic object is automatically sized and graphical information representing the results of the automatic sizing process may be displayed.

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 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 method of calibrating Doppler time-velocity waveforms obtained using a duplex ultrasound scanner. A spectral broadening error margin for the maximum velocity waveform is determined based on a unified theory of intrinsic spectral broadening for pulsed Doppler signals. The error margin is colorized or highlighted in the Doppler waveform display.

Abstract: A Doppler unit generates a Doppler signal from ultrasound backscattered signals. A logic unit performs a Fourier transform and compresses the resulting signals according to a compression curve determined in part by the noise level in the system. The peak values of the compressed signals also may be used to adjust the video gray mapping of the compressed signals in order to improve the appearance of a Doppler image on a display.

Abstract: A method and an apparatus for displaying an ultrasound image comprising a region of interest (ROI) having an optimal image quality and a background region having a normal image quality. In the displayed image the background region lies outside the ROI. The optimal image quality within the ROI is achieved by using a set of imaging parameters which are different than the set of imaging parameters used to acquire the background image, including one or more of the following: different (e.g., shorter) transmit waveforms, an increased number of transmit focal zones per unit depth, different transmit and/or receive apertures, different center frequencies for the receive bandpass filter (primary and/or (sub)harmonics), and higher vector density (i.e., decreased vector spacing). Since the optimal imaging is restricted to a ROI, a high frame rate is still possible within the ROI depending on its size.

Abstract: A method and an apparatus for automating the B-mode transmit waveform center frequency/length adjustment based on actual image data. The average SNR and the spatial correlation statistics in selected kernels of the image data are analyzed to test if high-quality signal is present. By placing one or more of the test kernels at relatively great depth (i.e., close to the bottom of the user-selected image depth range), the overall test results indicate the highest-resolution transmit waveform that can be used, while providing a sufficiently strong signal down to the desired depth.

Abstract: A method and apparatus for calculating the inter-slice spacing in a data volume and registering the slices of that volume using SAD calculations. The resulting transformed data volume is then three-dimensionally reconstructed using a projection technique. If during scanning the probe is translated in the Z direction and at the same time is shifted in the X and/or Y direction, the SAD value will be artificially high. By translating two adjacent images with respect to each other in the X direction and then in the Y direction, and searching for the minimum SAD value, the amount of shift in the X and/or Y direction can be determined and that shift can then be removed. Also by rotating two slices with respect to each other and looking for a minimum SAD value, rotational motion of the probe during scanning can be removed.

Abstract: A method and an apparatus for automating time-gain compensation (TGC) and lateral-gain compensation (LGC) based on the B-mode image data. The automatic gain adjustments are aimed at equalizing the mean signal intensities along the axial (for TGC) and/or lateral (for LGC) direction of the image, and suppressing any lateral band (for TGC) and/or sector (for LGC) that contains mostly noise. The automatic TGC/LGC adjustment method is implemented in software on a digital scanner and uses a noise model of the entire B-mode processing chain from the beamformer through the B-mode processor to the back-end video processor.

Abstract: A method for automatic Doppler angle estimation based on the B-mode and color flow (if available) image. The method uses an algorithm for automatic vessel slope measurement which first finds an optimal initial point within the sample volume or range gate, and then searches for the most reliable pixel points (near or far walls) based on a combination of intensity-only and intensity-difference thresholds, before performing a slope estimation. B-mode intensity data and, optionally, color flow velocity or power data (before gray/color mapping) are used. The algorithm may also be applied to methods for automatic tracking of vessel diameter and flow rate calculations, although the primary objective is to achieve automatic Doppler angle estimation in an ultrasound scanner.

Abstract: A method and an apparatus for enhancing the side-lobe performance of a sparse ultrasonic transducer array using harmonic imaging to reduce all beam sidelobe (including grating lobe) levels. Harmonic imaging consists of using the active transducer elements to transmit an ultrasound signal (wideband or narrowband) of center frequency f.sub.0 and receive at one or more harmonic frequencies nf.sub.0, where n.gtoreq.2.

Abstract: A method and an apparatus for tracking scan plane motion in free-hand three-dimensional ultrasound scanning using adaptive speckle correlation. The method employs a correlation index which adapts to different display dynamic range and post-processing filters. The method may include the following steps: choosing a kernel within each frame image for correlation calculations; rejecting duplicate image frames; measuring the degree of correlation between successive image frames; rejecting correlation estimates which may be associated with hand jitter and other artifacts; and computing the average frame-to-frame (i.e., interslice) spacing based on the average correlation estimate. This image-based motion tracking technique enables three-dimensional reconstruction with good geometric fidelity, without use of any external position-sensing device.

Abstract: A pulsed Doppler technique uses coded excitation on transmit and pulse compression on receive. Coded excitation allows a long transmit pulse to be compressed on receive such that most energy is concentrated in a short interval. In the case of a single coded transmit for each transmit focal position, the receive signals are compressed utilizing matched or mismatched filtering. In the case of a two or more coded transmits for each transmit focal position, the receive signals are compressed utilizing filtering coefficients which match the respective transmit codes during each firing. These techniques can be used to maximize Doppler sensitivity of a small but deep-lying sample volume. Alternatively, for a given transmit acoustic burst length and dosage, the sample volume can be reduced to achieve better spatial resolution without compromising sensitivity.

Abstract: A method and an apparatus for adaptively enhancing the B-mode image during post-detection image processing in an ultrasound imaging system. A low pass filter which smooths out speckle and a high pass filter which enhances edges are placed in parallel signal paths connected to the output of an envelope detector in a B-mode processor. The signals in the high pass filter path are logarithmically compressed before high pass filtering. The signals in the low pass filter path are logarithmically compressed after low pass filtering. Respective weighting factors are applied to the low- and high-pass-filtered signals by an adaptive weighting device, which may take the form of a processor or a look-up table. The weighted low- and high-pass-filtered signals are then summed and optionally input to an anti-aliasing low pass filter before decimation and scan conversion.

Abstract: An analytical method for automatic tracing of a Doppler time-velocity waveform envelope. At the core of this algorithm is a maximum frequency detection mechanism which is based on searching for the highest frequency bin whose spectral amplitude exceeds a certain noise threshold. The method is based on a theoretical noise amplitude distribution in the video spectral domain. In particular, the method uses a precise model of the statistical distribution of the video spectral power of white noise to establish a threshold for maximum frequency detection. Input to the noise model is the average white noise level in the video spectral display, which can be computed using either of two analytical methods.