Abstract: A piezoelectrically active conformal filler material is incorporated in a 1-3, 3-3 or 2-2 piezocomposite structure. The piezoelectrically active conformal filler material has a 0-3 structure and is made of fine piezoelectric ceramic particles surrounded by a conformal polymer matrix. Using such piezocomposite material, the reception and transmission sensitivity (efficiency) of a piezoelectric layer can be improved without any increase in the acoustic impedance of the final piezoelectric layer. The resulting piezocomposite material can be used to fabricate ultrasonic transducer arrays.

Abstract: A method and an apparatus for color mapping of flow power data in which the flow states containing information of most interest to the user are enhanced, while flow states not containing information of interest are suppressed. This is accomplished using a color mapping having three segments which are connected at upper and lower knee points, the latter being settable either automatically or via operator inputs. In the automatic mode, the host computer determines the positions of the knee points based on analysis of a single or a mean image frame of power Doppler data or based on system parameters (e.g., dynamic range) set by the operator. The host computer then constructs a color mapping having the determined knee points and loads that color mapping into the video processor.

Abstract: A method and an apparatus for compensating for fully or partially inoperative elements in an ultrasonic transducer array. The inoperative elements are compensated for by "bridging" or "shorting" them to fully operative elements. This compensation technique can be applied to one-dimensional or multi-dimensional transducer arrays. A bridge between a fully or partially inoperative element and an adjacent fully operative element can be achieved by physically shorting the elements somewhere in the signal chain or by electrically connecting the elements via switches, e.g., of a multiplexer. The state of the multiplexer switches (i.e., open or closed) is controlled by loading MUX State control data into a flash memory located on-board the probe. This MUX State control data includes switch settings for connecting a defective element to an adjacent fully functional element in the transducer array.

Abstract: A method and an apparatus for three-dimensional ultrasound imaging of a needle-like instrument, such as a biopsy needle, inserted in a human body. The instrument is visualized by transmitting ultrasound beams toward the instrument and then detecting the echo signals using a linear array of transducer elements. The problem of ultrasound being reflected from a biopsy needle in a direction away from the transducer array is solved by steering the transmitted ultrasound beams to increase the angle at which the beams impinge upon the biopsy needle. Ideally the ultrasound beams are perpendicular to the biopsy needle. This increases the system's sensitivity to the needle because the reflections from the needle are directed closer to the transducer array. This can be accomplished using either the B mode or the color flow mode of an ultrasound imaging system.

Abstract: 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.

Abstract: 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.

Abstract: An adaptive transducer array in which the element pitch is controlled by the imaging system depending on the mode of operation. A multiplicity of transducer elements are connected to a multiplicity of beamformer channels by a multiplexing arrangement having multiple states. In one multiplexer state, successive transducer elements are respectively connected to successive beamformer channels to produce an aperture having a small element pitch equal to the distance separating the centerlines of two adjacent transducer elements. In another multiplexer state, selected transducer elements are respectively connected to successive beamformer channels to produce an aperture having an increased element pitch equal to the small pitch multiplied by a factor of two or more. The aperture is increased by connecting together pairs of adjacent elements to a respective beamformer channel or by connecting every other element to a respective beamformer channel to form a sparse array.

Abstract: A method and an apparatus for mitigating aliasing when imaging moving fluid or tissue using velocity Doppler shift data. To eliminate the effects of slight aliasing in the velocity mode, symmetrical (or non-directional) velocity/color maps are used to map positive and negative velocity data of the same magnitude to the same color and same display intensity. If the pulse repetition frequency is adjusted so that only subtle aliasing is present, an optimal frame averaging of the data can be achieved by removing the sign of the velocity data either before or during frame averaging.

Abstract: A signal processing technique for improving the axial resolution and/or the sensitivity of an ultrasonic imaging system. This technique also improves the lateral resolution and the depth of field. The technique is based on combining two or more transmit wave functions in an optimal manner to achieve a synthetic waveform which has greater bandwidth and/or energy than the individual wave functions. This scheme operates on the imaging data before the data reaches the envelope detector, while the phase information is still maintained within the signal. Using a synthetic transmit wave design approach, the effective emitted pressure waveform would have a bandwidth which would be wider than the transducer bandwidth with high sensitivity. The synthetic transmit waveform design scheme consists of firing two or more relatively long transmit waveforms for each single A-line in a given focal zone. The frequency spectrum for each of these transmit pulses is centered at a slightly different frequency.

Abstract: 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.

Abstract: 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.

Abstract: A method for controlling the contrast resolution and the tissue texture of ultrasonic images employs a signal processing algorithm to adjust an image by changing the tissue texture (speckle grain size). The algorithm increases the image contrast by allocating a different speckle pattern to different grey scale levels. This signal processing algorithm is based on the Hilbert transform. It uses the property of the Hilbert transform to generate a quadrature component of the given image which is modulated by the speckle pattern as well as all other image information. The quadrature component is then squared before being selectively added to or subtracted from the square of the in-phase component of the given image to control the information in the image. The added or subtracted signals have different textures (or spatial frequency components). The arithmetic operation between the in-phase and quadrature phase components determines the image texture.

Abstract: A method for optimizing the beam distribution to obtain the highest frame rate together with the least amount of acoustic noise while limiting the spatial aliasing to an acceptable level. The beam distribution is adjusted according to the scan format and as a function of the beam width, which is proportional to the product of the F number and the operating wavelength. As the F number changes in going from the shallow depth to a deeper depth, the number of beams fired to construct an image would change correspondingly. In addition, if the F number is changing in going from the center of image to the edge of the image, the separation of the fired beams would change. Alternatively, if the operating frequency is being changed in going from shallower depths to deeper depths or in going from the center of image to the edge of the image, the beam spacing is changed in order to fire the optimum number of beams at all times, and thereby obtain the highest frame rate.

Abstract: An ultrasonic probe for coupling acoustic signals between the probe and a medium is provided. The ultrasonic probe has a piezoelectric element having a plurality of piezoelectric layers each having a different acoustic impedance. The piezoelectric layers are stacked in progressive order of acoustic impedance such that the layer with the acoustic impedance nearest to that of the medium is proximate the medium. At least one of said piezoelectric layers is made of piezoelectric composite material. The ultrasonic probe further has an electrode means for electrically coupling the piezoelectric layers to a voltage source for applying an oscillation voltage potential to each piezoelectric layer. The probe further has a control means for controlling the polarization of at least one of the piezoelectric layers.