摘要:
An ultrasound color flow imaging system is programmed to operate in an adaptive manner. The operational adjustments are made based on the system gain setting or the transmit packet size or both. Based on these operator inputs, the transmit burst length is adjusted for optimum operation. In addition, the transmit peak amplitude and the bandwidth of the receive filter are adjusted as a function of the burst length adjustment.
摘要:
A method and an apparatus for increasing the spatial resolution and sensitivity of a color flow image while maintaining a desired acoustic frame rate. The ultrasound energy is concentrated at a more narrowly defined focal region, which allows for increased flow sensitivity and vessel filling. Better flow uniformity across the color region of interest is also achieved. The method uses multiple transmit focal zones, and transmit and receive apertures having low f-numbers. Using multiple focal zones with low f-numbers allows for tight focusing over a larger depth-of-field. Unique waveforms and unique gain curves are used for each focal zone. Each focal zone is fired on a separate acoustic frame. An adaptive frame averaging algorithm is used to blend together the in-focus data from each of these acoustic frames before the data is displayed.
摘要:
A method and an apparatus for frame averaging ultrasound imaging data. A one-tap IIR filter is used to average the corresponding pixel data of two frames. The frame averaging is a function of a normalized difference between the pixel data of the two frames. This is achieved by taking the absolute difference between the signal levels of the current frame and the previous frame and dividing the result by the arithmetic (or geometric) mean of the two data. A multitude of look-up tables of output values are generated off-line. Each look-up table is designed to be used under a specific set of operating parameters. In response to the user's selection of these operating parameters, the system downloads a selected frame-averaging look-up table from system memory. During subsequent system operation, the downloaded look-up table outputs values which are a function of the normalized difference between the previous and current frame data used to address the look-up table.
摘要:
A method and an apparatus for three-dimensional imaging of ultrasound data by constructing projections of data from a volume of interest. An ultrasound scanner collects B-mode or color flow images in a cine memory, i.e., for a multiplicity of slices. A multi-row transducer array having a uniform elevation beamwidth is used to provide reduced slice thickness. The data from a respective region of interest for each of a multiplicity of stored slices is sent to a master controller, such data forming a volume of interest. The master controller performs an algorithm that projects the data in the volume of interest onto a plurality of rotated image planes using a ray-casting technique. The data for each projection is stored in a separate frame in the cine memory. These reconstructed frames are then displayed selectively by the system operator. Segmentation of three-dimensional projection images is enhanced by decreasing the thickness and increasing the resolution (i.e., decreasing the point spread function) of the two-dimensional slices from which the projections are derived. The slice thickness is decreased by increasing the elevational focus of the beam. The two-dimensional resolution is increased by opening the aperture, i.e., decreasing the f-number, and by increasing the band-width.
摘要:
An ultrasound imaging system having an adaptive spatial filter the filter coefficients of which, for particular image parameter sample, are determined by counting the number of neighboring image parameter samples having zero or near-zero values. If the number of zero or near-zero values in a data window is greater than a predetermined threshold, the data in the window is passed, not filtered. This filter has two advantages over other spatial filters. First, image parameter data samples having only zero or near-zero neighboring values (i.e., isolated "point noise") are not smeared. Second, boundaries such as the edge of color in a vessel (where the surrounding area is black, i.e., the color image parameter values are zero or near zero) are not smoothed as much as in conventional filters, preserving the sharpness of the edge.
摘要:
An ultrasound imaging system for displaying edge-enhanced topographic flow power data surrounded by B-mode anatomical data without masking out any significant edge-enhanced topographic flow power data and without displaying any significant flow power background noise. An improved high-pass topographic filter is used to enhance the edges of the flow in the displayed image in both the horizontal (lateral) and vertical (range) directions. The two-dimensional topographic filter is a digital filter with three taps in each dimension and is incorporated in the acoustic line memory. Also, the raw flow power data is compressed down to 7 bits in such a way that the transfer function is shifted away from zero input power. In this way, the system gain can be set to effectively zero out most of the background noise. After the flow power data passes through the high-pass topographic filter, it is mapped to values between -128 and +127 (8 bits) with zero in the middle. The system gain is set so background flow power noise will be mapped relatively uniformly to within .+-.2 of zero out of the topographic filter. The center of the color map (within .+-.2 of zero) is masked out so that any edge-enhanced topographic flow power that maps within this range is not displayed and, instead, the B-mode imagery is displayed.
摘要:
An ultrasound survey frame (SF) is processed in order to determine the portions representing fluid flow. An assembly (20) again rescans only the portions of a subject represented by the portions of the survey frame in which fluid flow was found. Target frames (TF) then are created from the rescanning and are processed in order to provide a color flow image restricted to the portions of the survey frame in which fluid flow is indicated.
摘要:
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.
摘要:
A color flow imaging 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. Multiple transmit firings of the same coded pulse sequence are focused at the same transmit focal position with the same transmit characteristics. The receive signals are compressed utilizing matched or mismatched filtering. These techniques can be used to maximize color flow sensitivity in deep-lying regions. Alternatively, for a given transmit acoustic burst length and dosage, the spatial resolution can be improved without compromising sensitivity.
摘要:
In performing 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, each coded sequence constituting one firing. On receive, the receive signals acquired for each firing are supplied to a finite impulse response filter which both compresses and bandpass filters the receive pulses, e.g., to isolate a compressed pulse centered at the fundamental frequency. The compressed and isolated signals are then high pass filtered across firings using a wall filter. The wall-filtered signals are used to image blood flow and contrast agents.