General Electric Company

Marquette Electronics

Theodore Lauer Rhyne

Richard Yung Chiao

William E Engeler

Lowell Scott Smith

Steven Charles Miller

David John Muzilla

Larry Y Mo

John T Pedicone

John E Mahony

Christopher J Gilling

Christopher M Daft

Xuan-Ming Lu

Nim Hak Tea

Kok-Hwee Ng

An ultrasound transducer employs a silicon acoustic matching layer closest to the piezoelectric layer in order to achieve improved resolution. A silicon wafer, ground to an appropriate thickness, is included in the acoustic stack with other matching layer materials during transducer construction. The exact thickness is determined by the details of the design, but is nominally a quarter wavelength in the silicon.

Ultrasound transducer for improving resolution in imaging system

A broadband ultrasonic transducer has a layer of piezoelectric material sandwiched between respective layers of backing and matching material. The piezoelectric element is coupled to a pair of electrical terminals, across which a varying voltage is produced. The piezoelectric layer has a structure such that in response to the varying voltage, a forward-propagating wave emanating from its back surface does not destructively interfere with a forward-propagating wave emanating from its front surface when the frequency of the waves is an even multiple of the half-wave frequency of the particular piezoelectric layer. This effect can be attained by roughening the back surface of the piezoelectric layer or by spatially varying the piezoelectric coupling in the thickness direction in a portion of the piezoelectric layer which is proximate to the back surface.

Broadband ultrasonic transducers and related methods of manufacture

Harmonic imaging using harmonic Golay-coded excitation that encodes the fundamental and second harmonic signals utilizes the transmit sequences encoded using QPSK implemented as quarter-cycle circular rotations or shifts of the base pulse. This is implemented by time shifting the chips of the transmit sequence encoded with a &ldquo;j&rdquo; or &ldquo;&minus;j&rdquo; code symbol by &frac14; fractional cycle at center frequency relative to the chips encoded with a &ldquo;1&rdquo; or &ldquo;&minus;1&rdquo; code symbol. A different QPSK transmit code is used for each of four transmits A, B, C and D. The transmit codes are selected such that (A-B) and (C-D) are encoded by and &minus; , respectively, while (A -B ) and (C -D ) are encoded by X and Y, respectively, where X and Y form a Golay code pair. The coding and decoding technique achieves fundamental suppression and second harmonic compression for a given Golay code pair X and Y.

Harmonic golay-coded excitation with differential pulsing for diagnostic ultrasound imaging

An ultrasound survey frame (SF) is processed in order to determine the portions representing fluid flow. An assembly (,) 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.

Ultrasound color flow adaptive scanning techniques

A method and an apparatus for imaging the nonlinear components of an ultrasound signal returned from ultrasound scatterers in tissue or contrast agents in blood. The method employs a code-modulated wavelet for transmission combined with correlation filtering on reception. Coding methods are used to simultaneously manipulate the linear and nonlinear terms. The manipulations affect the magnitude and temporal arrangement of the resulting decoded waveforms. Among the simultaneous manipulations of linear and harmonic decoded signals are: orthogonal linear terms, finite linear terms, minimum sidelobe with optimal peak harmonic terms and optimally compressed harmonic terms.

Method and apparatus for harmonic tissue imaging and contrast imaging

A method and an apparatus for imaging a nonlinear signal component isolated from the echo signal derived from transmission of a base waveform having fundamental frequency f.sub.0 and relatively high peak power. The nonlinear signal component is isolated by subtracting the linear signal component from the echo signal. This is accomplished using a second transmit firing derived from the same base waveform, but having different transmit characteristics, i.e., the base waveform is convolved with a code sequence to form a coded waveform. The coded waveform is transmitted at relatively low peak power. The beamsummed signal produced from the low-peak-power coded transmit is pulse compressed and then subtracted from the beamsummed signal produced from the high-peak-power uncoded transmit. The signals are scaled as necessary to achieve cancellation of the linear signal components when one beamsummed signal is subtracted from the other, leaving the nonlinear signal component for imaging.

Method and apparatus for acoustic subtraction imaging using linear and

A method and an apparatus for imaging the nonlinear components of an ultrasound signal returned from ultrasound scatterers in tissue or contrast agents in blood. The method employs a code-modulated wavelet for transmission combined with correlation filtering on reception. Transmit codes are used to modulate the phases of wavelets for successive transmit firings focused at the same transmit focal position. For example, for a first transmit firing a first transmit code is used to modulate a base wavelet to form a first coded wavelet and for a second transmit firing a second transmit code is used to modulate the same base wavelet to form a second coded wavelet. On reception, the receive signals resulting from the first and second transmit firings are decoded by correlating the receive signals with first and second receive codes respectively. The transmit and receive codes satisfy the orthogonality condition that the sum of the correlation of the first transmit code with the first receive code and the correlation of the second transmit code with the second receive code equals zero. The combined transmission and reception operations will exactly cancel the linear echo component of the signal, leaving the nonlinear components for imaging.

Nonlinear imaging using orthogonal transmit and receive codes

A method using a progressive sampling rate technique to maintain the sampling rate at the Nyquist frequency of the I/Q data through a tunable equalization bandpass filter in the front end of the imager and then increasing the sampling rate via axial interpolation to prevent aliasing during the nonlinear detection process. If an envelope detector is used, the bandwidth of the detector output should be approximately double that of the I/Q data. In this case, the sampling rate is doubled (or more) by axial interpolation before envelope detection. A 2-point linear interpolator can be used. Depending on the application, this axial interpolator can be turned on or off automatically by the system. After detection, the signal can be low-pass filtered to restrict the speckle bandwidth prior to log compression.

Method and apparatus for preventing axial spatial aliasing in ultrasound

A method for designing ultrasonic transducers used in diagnostic ultrasonic imagers, in particular, transducers made up of at least one piezoelectric layer and at least one acoustic matching layer, plus various bonding and backing layers. The method of transducer design uses a particular family of spectra as the basis of the bandpass characteristic. The approach is to specify a transfer function from the Transitional Butterworth Thompson family of spectra. The specification is influenced by trade-offs in bandwidth, transient response and design feasibility. This family is indexed by a design parameter called M. Using the M factor, a designer can more readily make the engineering trade-offs needed. By adjusting this parameter, any dynamic response from maximally flat to Gaussian can be obtained. Since not all possible members of this spectral family are feasible as transducers, a design space (bandwidth versus band shape) is used to systematically represent the engineering trade-offs and to graphically represent the physical constraints on feasibility.

Method for designing ultrasonic transducers using constraints on

A PASS ultrasonic system includes a separate receive channel for each respective element in an ultrasonic transducer array which imparts a delay to the echo signal produced by each respective element. The delayed echo signals are summed to form a steered, dynamically focused and dynamically windowed receive beam which can be readily interpreted even when the transmit beam does not emanate from the center of the array.

Ultrasound imaging system with dynamic window function

A PASS ultrasonic system includes a receive channel for each element in an ultrasonic transducer array which imparts a delay to the echo signal produced by each element. The delayed echo signals are summed to form a steered and dynamically focused receive beam. Each receive channel is formed as an integrated circuit. The integrated circuit calculates the required time delay for dynamic focussing in the receive channel as a function both of elapsed time in unit increments related to unit phase rotation increments of the carrier frequency and of previously calculated time delay values, in order to control a phase rotator and delay FIFO in the receive channel to implement echo signal delay control.

Ultrasound imaging system with improved dynamic focusing

Optimal measurement of ultrasonic random backscatter from the myocardium is obtained by band limiting and whitening the received signal, squaring, summing and scaling same. The whitening is carried out for all spectrally altering factors to which the ultrasonic signal has been subjected. This includes whitening for the power law frequency response characterstics of the myocardium itself. Scaling includes a factor accounting for the energy of the effective transmitted ultrasonic signal and a factor providing appropriate units of measurement. The optimal measurement may be time averaged over one or more heartbeats for use in the diagnosis of ischemia or other cardiac conditions. It may be subjected to discrete Fourier transform analysis, to obtain its amplitude modulation and phase characteristics for similar purposes.

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Whitefish Bay, WI, United States of America

Theodore Lauer Rhyne