Abstract: A method and apparatus for coupling ultrasonic energy into a clad or unclad waveguide include using phased array techniques to increase the area and intensity of radiation into the waveguide. An array of ultrasound transducers is positioned at the exterior of the waveguide and at dissimilar distances from the end of the waveguide. The transducers are individually fired by applying separate phase-shifted excitation signals. The phase shifting achieves a selected phase-differential relationship with respect to signals applied to adjacent transducers. The selected phase-differential relationship defines an angle of radiation into the waveguide. In the preferred embodiment, the apparatus is a medical device, such as an angioplasty device or ultrasound imaging device.

Abstract: Piezoelectric elements in a transducer array are individually excited and used to sense the back-scattered signal from fluid flowing within an interrogation volume. The array is preferably a 2-D phased array with a pitch no greater than one-half the acoustic wavelength of the interrogation signal. By activating the transducer elements as a pattern of concentric rings as viewed from a point of interrogation, and by suitable phasing and range-gating of an interrogation signal, a substantially spherical interrogation volume (SIV) is created. The return signal from the SIV provides an isotropic indication of the speed of flow of the fluid. The focussing distance along an interrogation axis can be changed by changing either the size of the aperture created by the pattern of activated elements or their relative phasing. The interrogation direction can be angled off-axis by activating the transducer elements in a pattern of concentric ellipses.

Abstract: An ultrasound system and method for intravascular ultrasonic imaging includes an array of beacons that are fixed to direct ultrasonic energy toward an imaging transducer, with individual beacons being identifiable in order to determine the angular position of the imaging transducer. Based upon the data related to beacon identification, operation of the imaging device is adaptively adjusted in order to compensate for variations in angular velocity of the transducer. Adaptive compensation may be performed by adjusting the pulse repetition rate of transmitted ultrasonic energy, by adjusting the scan conversion algorithm or mapping reflected ultrasonic energy, or by varying control of the drive structure for rotating the transducer. The beacons are preferably piezoelectrically active, but passive beacons may also be used. Position identification may be performed by techniques including amplitude sensing, phase sensing, pulse length sensing, and frequency sensing.

Abstract: A method and system of monitoring performance of a heart include echocardiographic transmission and reception to form time series of frames containing mean squared difference data. Mean squared signal change, mean squared speed or root mean squared speed may be used to form functional images, such as average speed over a selected time interval or peak speed over a selected time interval.

Abstract: A method and system for monitoring performance of a heart includes forming a time series of frames of echocardiographic data. The time series may be for a systolic interval, but longer intervals are also possible. The frames of the time series have sets of corresponding data points with respect to specific sites of a patient's heart. For each set of corresponding data points, a time domain signal as a function of a selected scalar is determined, thereby yielding a time domain signal which varies with frame-to-frame variations of the selected scalar. The scalar has a physiological significance to the contractile state or the motion of the myocardium. Mean squared speed, root mean squared speed, mean squared rate of signal change, integrated backscatter, correlation area, and echocardiographic signal data magnitude are suitable scalars. For each time domain signal, a phase angle is obtained to assign a pixel value to an image data point.

Abstract: Spherical annulus piezoelectric transducers 62, 64 and spherical disc piezoelectric transducer 66 form a spherical shell having a radius of curvature R with a focal point 70 near the end of cladded-core acoustic waveguide 72. Each transducer 62, 64, 66 generates a bulk acoustic wave of a unique frequency and transmits it to focal point 70 where it enters core 74 of cladded-core acoustic waveguide 72. Alternatively, a conical annulus piezoelectric transducers 92, 116 on a prism 90 generate bulk acoustic waves of multiple discrete frequencies and focus them through cladding 75 and into core 74 of cladded-core acoustic waveguide 72. Surface acoustic waves of multiple discrete frequencies can be generated by multiple sets of curvilinear interdigital conductors 132, 134 on a piezoelectric substrate 122. The shape of curvilinear interdigital conductors 132, 134 focuses the surface acoustic waves at focal point 70 located near the end of acoustic waveguide 72.

Abstract: An ultrasonic transducer for controlling an elevation aperture utilizes the electric field-induced polarization properties of relaxor ferroelectric materials. The Curie temperature of the material is typically close to room temperature, so that the application of a bias voltage provides piezoelectric activity. By varying the thickness of a dielectric layer that spaces apart the relaxor ferroelectric material from an electrode or providing the bias voltage, the piezoelectric activity can be tailored. That is, degrees of polarization of the relaxor ferroelectric material are varied spatially in correspondence with changes in thickness of the dielectric layer. The effective elevation aperture of the transducer can be varied by adjusting the bias voltage.

Abstract: A two-dimensional ultrasonic transducer array includes a plurality of transducer elements, with each element having a plurality of piezoelectric layers. The transducer elements vary in transverse areas of radiating regions. The effect of the variations in transverse areas on the electrical impedances of the elements is at least partially offset by varying the specific impedance, i.e., impedance per unit area, of the transducer elements in the array. In a preferred embodiment, the specific impedance is varied by selecting the electrical arrangements of piezoelectric layers in each element according to the transverse area of the element. Series, parallel and series-parallel arrangements are employed. This impedance normalization improves the electrical connection of the transducer elements to driving circuitry. In alternative embodiments, impedance normalization is achieved by varying element thicknesses, element materials and/or degrees of poling across the two-dimensional array.

Abstract: Pulses of ultrasound are focused in the patient's body to create an interrogation volume where a characteristic of blood flow is to be measured. The bandwidth of the back-scattered Doppler return signal is measured. In order to measure flow velocity independent of direction, the interrogation volume is generated substantially as a sphere in which the range dimension is set equal to the lateral dimensions (azimuth and elevation) of the interrogation signal. The Doppler bandwidth is then scaled to provide a direction-independent measurement of flow velocity. In order to determine the direction of flow, the interrogation volume is generated substantially as an ellipsoid. The long axis of the ellipsoidal interrogation volume is then rotated until the measured Doppler bandwidth is at a minimum, which is reached when the long axis is aligned with the flow direction.

Abstract: Pulses of ultrasound are focused in the patient's body to create an interrogation volume where either the magnitude of velocity or the direction of blood flow is to be measured. The strength of the back-scattered signal is measured for each pulse and the mean squared rate of change of the envelope of the range-gated signal is estimated. In order to measure flow velocity independent of direction, the interrogation volume is generated substantially as a sphere by creating an ultrasonic wave envelope in which the components of the mean square spatial gradient are equal in all directions. The estimated mean square rate of change of the envelope of the back-scattered signal is then scaled to provide a direction-independent measurement of flow velocity. In order to determine the direction of flow, the interrogation volume is generated substantially as an ellipsoid.

Abstract: An apparatus detects a target reactant that binds to an immobilized reactant. The apparatus generates a holographic image at a predetermined location when the reactants are present and bound to one another. The immobilized reactant is bound to a support surface at selected locations. The locations are chosen such that a holographic plate is generated when the target reactant binds to the immobilized reactant. An associated method may be used to detect antibody-antigen reactions, the binding of two strands of nucleic acid, the binding of an enzyme to one of its substrates, and so on.

Abstract: A method and apparatus are provided for determining correlation length of body tissue, metals, crystals, or other materials, substances and the like having an ordered internal stucture (hereinafter structures) and for utilizing such correlation length to test, classify or otherwise characterize the structure. The structure is scanned using standard ultrasonic scanning technology and the output from such scan is processed to determine correlation length in one dimension (length), two dimensions (area), three dimensions (volume). A fourth dimension of time may also be used with one or more of the other three dimensions in the correlation length determination.

Abstract: An intracavity ultrasound diagnostic probe has a fiber acoustic waveguide that guides acoustic signals generated by a piezoelectric transducer located outside the body, through a body cavity and to an imaging site within the body where they reflect back into the ultrasound diagnostic probe that guides them back to the piezoelectric transducer located at the proximal end of the waveguide. The intracavity ultrasound diagnostic probe has one or more acoustic waveguides that could be optical fibers.

Abstract: A system for deriving signals representing a selected cross sectional area and volume of a region of interest in tissue. In the preferred embodiment, area and volume of a fluid filled cavity contained in tissue on a real time basis are determined by launching pulses of ultrasonic pressure waves along a plurality of scan lines, detecting the locations along each line that are in fluid, deriving a signal representing the incremental area within fluid that is between adjacent scan lines, deriving a signal representing the cross sectional area of a cavity within a region of interest by summing the incremental areas and deriving a signal representing the volume of the cavity within a region of interest by revolving each incremental area about an axis of the cavity so as to form an incremental volume of revolution and summing the volume of revolution.

Abstract: A system for deriving signals representing a selected cross sectional area and volume of a region of interest in tissue. In the preferred embodiment, area and volume of a fluid filled cavity contained in tissue on a real time basis are determined by launching pulses of ultrasonic pressure waves along a plurality of scan lines, detecting the location along each line that are in fluid, deriving a signal representing the incremental area within fluid that is between adjacent scan lines, deriving a signal representing the cross sectional area of a cavity within a region of interest by summing the incremental areas and deriving a signal representing the volume of the cavity within a region of interest by revolving each incremental area about an axis of the cavity so as to form an incremental volume of revolution and summing the volumes of revolution.

Abstract: Apparatus for deriving signals indicating a condition of tissue within an area by launching spaced supersonic pulses into a body under examination and detecting the power of supersonic waves scattered from locations along a plurality of known paths. Gain control elements are provided for compensating for changes in amplitude of the scattered supersonic waves resulting from their passage through blood or tissue, the increased attenuation with frequency of the spectrum of the launched pulses and the focussing of the launched pulses. Compensation for ring-down and the attenuation of the chest wall is also provided.