Abstract: An optical communication system for ultrasound imaging systems employs a light source and photodetector array in the imaging console. The light source and photodetector array are coupled to each other through an optical fiber passing through the probe. Information from the probe is communicated to the console by an optical modulator, situated in the optical path from source to detector. The ultrasound signals are converted into electrical signals by probe electronics, and these electrical signals serve to alter either the phase or amplitude of optical signals passing through the modulator. Since the light source and photodetectors reside in the imaging console, very little power is dissipated in the probe.

Abstract: Ultrasonic imaging performed with a large aperture phased array employs partially coherent processing to provide an improved real-time ultrasound image compared to that obtainable using either fully coherent or fully incoherent processing. Partially coherent processing is achieved by computing different sums across the imaging aperture and using a weighted total of the computed sums to generate a real-time image, enabling the operator to choose the extent of coherent summation versus incoherent summation across the aperture. Since coherent summation affects spatial resolution and incoherent summation affects contrast resolution, a trade-off between spatial and contrast resolution results in an optimal image for a given application.

Abstract: An apparatus and method are described for imaging blood flow from within a vasculature. An ultrasound catheter probe carrying an ultrasound transducer array is inserted within a blood vessel. The transducer array emits ultrasound excitation signals and receives ultrasound echo waveforms reflected from blood and tissue in a region of the vasculature. A series of the echo waveforms resulting from a series of excitation signals are combined in a manner such that the echo signals from static features in the region, such as tissue and plaque, are significantly attenuated. The combined signal primarily represents the relatively dynamic features in the region (i.e. the blood flow). A blood flow image is constructed from the combined signal. The blood flow image is colorized and combined with an image of the relatively static features in the region. Thereafter, the combined image is displayed on a video display.

Abstract: An ultrasonic imaging system for displaying color flow images includes a receiver which demodulates ultrasonic echo signals received by a transducer array and dynamically focuses the baseband echo signals. A color flow processor includes a frequency domain adaptive wall filter which automatically adjusts to changes in Doppler-shifted frequency and bandwidth of the wall signal components in the focused baseband echo signals after the echo signals have undergone Fourier transformation into the frequency domain. The mean Doppler-shifted frequency of the resulting filtered baseband echo signals is used to indicate velocity of moving scatterers and to control color in the displayed image.

Abstract: A phased array sector scanning ultrasonic imaging system produces simultaneously, and samples, three receive beams for each transmitted ultrasonic pulse directed upon flowing reflectors. Flow velocity is measured in the cross range direction using a correlation technique while flow velocity in the range direction is simultaneously measured using a Doppler method. By performing cross correlation in both the range and cross range directions with data acquired from a set of such multi-beam acquisitions, a B-scan image is produced which indicates both magnitude and direction of the flowing reflectors.

Abstract: A phased array sector scanning (PASS) ultrasonic imaging system produces a fixed focus, steered transmit beam with an array of transducer elements. A receiver forms the echo signals received from an ultrasonic energy reflecting object at the array elements into a receive beam steered in the same direction as the transmit beam and dynamically focused. A midprocessor in the receiver makes corrections to the receive beam samples to offset errors caused by the transmit beam being out of focus at all but its fixed focal range.

Abstract: A beam former in a PASS ultrasonic imaging system includes a set of sigma-delta modulators which operate to separately digitize the received echo signal from each transducer element. The oversampled one-bit digital representations of each echo signal are delayed as required for beam steering and focusing, and are summed together. A decimator filter reduces the sample rate of the digitized receive beam prior to display of the image resulting from the receive beam.

Abstract: A catheter based ultrasound imaging system is disclosed which is capable of providing images of coronary vessels at frequencies near 50 MHz. The catheter based system implements a Synthetic Aperture Focusing Technique (SAFT) by scanning through a miniature ultrasound transducer array to sequentially select and fully multiplex a subset of array elements to operate as a sub-aperture of the total synthetic aperture on each firing; thus reducing the number of required catheter interconnections. Each synthetic aperture array is dynamically and retrospectively focused to accommodate precision imaging at high frequency without conventional signal to noise losses.

Abstract: A PASS ultrasonic system performs a scan in which phase errors due to aberrations in the sound media are corrected prior to the acquisition of each beam. Phase errors are measured by cross correlating each of a set of reference beams with the desired beam to produce beam forming errors as a function of beam angle. This function is Fourier transformed to produce phase corrections that are employed by the ultrasonic system to offset the phase errors.

Abstract: A phased array sector scanning (PASS) ultrasonic imaging system produces a steered transmit beam with an array of transducer elements that are driven with separate carrier frequencies. A receiver forms the echo signal into a receive beam steered in the same direction as the transmit beam and is dynamically focused. A transmit beam processor Fourier transforms this receive beam to produce a signals corresponding to the separate carrier frequencies which can be delayed to retrospectively dynamically focus the transmit beam or alter the direction in which it is steered.

Abstract: A phased array sector scanning ultrasonic imaging system produces digitized baseband samples of the received ultrasonic echo signals amplified by a time gain control (TGC) to compensate for dispersion losses in the media in which the ultrasonic signals propagate. A time frequency control filter employs the same TGC control signal to calculate a phase shift correction as well as the coefficients which determine the characteristics of a bandpass filter such that the frequency dependent dispersion losses in the ultrasonic echo signals are compensated.

Abstract: A method for dynamic focus of received energy, in a vibratory energy imaging system, into a beam in which contribution from transducers in an array of N such transducers, are progressively enabled to contribute to beam focussing dependent upon distance between a particular j-th transducer (where 1.ltoreq.j.ltoreq.N) is responsive to the depth, or range R, of the focal point at any instant of time; the initial steering angle .theta., with respect to the array normal, is used in conjunction with a range clock, to determine the time when each off-normal transducer channel is enabled to add to the beam (dynamic apodization) and to finely adjust the channel time delay to properly focus the beam after the enablement of the channel.

Abstract: Apparatus for testing data conversion/transfer functions in each of a plurality N of channels of a vibratory energy imaging system includes a multiplexer for providing, to an addressable memory having a plurality of L=2.sup.M locations in each of which a data word of B bits can be stored, a selected one of an input data word and a test data word, each of which can address one of the L locations of the memory means. The address multiplexer facilitates retrieval from memory of a B-bit data word having a value selected to implement a selected function for that channel, so that comparision of data from the selected test address with the data which has been sent to that location for storage, will indicate if proper data is stored for carrying out the designated function.

Abstract: A method for correcting data conversion/transfer errors in each of a plurality N of channels of a vibratory energy imaging system, by: providing an addressable memory having a plurality L=2.sup.M locations, each for storage of a data word of B bits; then storing in each of the L locations of the memory means a B-bit data word having a value selected to cause the output-to-input transfer function for that channel to assume a desired relationship, with respect to a standard transfer measure; and selecting that one of the L data word locations, responsive to that actual one of an M-bit data word output from a channel ADC or from a data bus, responsive to a test signal, in which to place corresponding data.

Abstract: Apparatus for providing a desired output signal as a function of a single-valued input signal in an electronic system, includes: an addressable memory, having a plurality L locations, each for storage of a data word of B bits; a circuit for storing in each of the L locations of the memory means a B-bit data word having a value selected to provide a particular output value; and circuitry for converting a present single-valued increment of input signal to a unique address, within the range of allowable locations of the memory, to cause each increment of input signal to select the associated one of the L data word locations, from which to output corresponding data.

Abstract: A method for imaging a sample with a beam of vibratory energy from an array of transducers excites the array with successive ones of a plurality M of coded excitation signal sets with each set occurring in a different one of successive excitation time intervals. Each different set has signals with a different code. An excitation beam, produced by the array, is focused into the sample at successively smaller distances, along a selected ray path from the array, during each successive excitation time interval. A reception beam is focused along the ray path at successively greater distances from a minimum distance away from the array during each successive one of a like plurality of reception time intervals, for receiving, during each reception time interval, return response signals reflected from the sample.

Abstract: A method and apparatus for improved digital processing of the analog echo signals in a coherent imaging system is described which simplifies the channel circuitry requirements. The analog echo signals detected with a phased array of transducer elements are first compressed in a non-linear manner then expanded non-linearly with analog-to-digital converter means to provide increased instantaneous dynamic range in the overall system. Representative phased array coherent imaging systems having the improved digital processing means are also disclosed.

Abstract: A method for iterative phase conjugation adaptive reduction of phase aberration effects upon the time delays necessary for formation of a beam of coherent energy focused within non-homogeneous medium at a selected range R from, and at an angle .theta. with respect to the normal to, the surface of an array of a plurality N of transducers, each for providing a portion of the energy of the beam when excited and for converting energy reflected thereto to a signal therefrom, first bounces from a large collection of scatterers, contained in a portion of the medium to be investigated, a probe beam for that beam angle .theta.. The received signals from each of the (N-1) pairs of adjacent transducers are cross-correlated to drive a like number of phase conjugation correction signals, which are then arithmetically operated upon to provide a time correction for the time delay associated with each probe beam transducer, for that range R and angle .theta..

Abstract: A method for generating a stream of digital data words, each representing an analog signal amplitude from a beam of vibratory energy received by a plurality N of transducers each associated with one of a like number of separate channels of a phased array, uses the steps of: sampling, after a delay of a multiple number of cycles at a fixed frequency F, an analog input signal in each channel at a fixed frequency F for conversion to a digital data word at each sample; then demodulating the digital data word stream in each channel to baseband and reducing the data word rate by a factor D; and phase-rotating the baseband data stream of each channel by a phase difference .DELTA..phi. determined by the focal range R and steering angle .theta. to obtain, along both the sampling delay, a different channel time delay t.sub.d,j, for each j-th channel, where 1.ltoreq.j.ltoreq.N, necessary to steer and focus the beam to a desired angle/range combination.

Abstract: A CORDIC (COordinate Rotation DIgital Computer) subsystem for multiplication of two complex digital numbers B and C, where one number is the sum of real and imaginary data portions, expressed in rectangular form (say C.sub.r or C.sub.I), and the other number can be expressed in the rectangular form or can be represented by magnitude data, expressed in polar form (say, .vertline.B.vertline., .phi.). An N-stage CORDIC portion of either recursive or pipeline sequential form, but devoid of multipliers, is used to rotate the I and Q terms of the first number through a phase angle .phi. of the polar-form multiplier number of the equivalent, taken from the rectangular form. The final computed data are the real and imaginary parts of the product.