Measurement of true blood velocity by an ultrasound system
First Claim
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1. A steered beam ultrasound instrument for measuring two components of the flow velocity of blood and similar liquids comprising:
- a linear transducer array for transmitting pulses of ultrasound with a preselected emission frequency and for generating received echo signals,said array being comprised of a row of elements divisible into a transmitter sub-array and into left and right receiver sub-arrays that are variably located such that received center wave vectors through any observation point in the field of view subtend approximately equal angles with respect to a transmitter wave vector through the observation point,means for exciting the elements of said transmitter sub-array to sequentially generate ultrasound pulses that propagate along a designated beam direction and insonify a sample volume through which the true flow velocity vector is being determined,left and right receiver means for coherently demodulating echo signals generated by the respective sub-arrays with phase quadrature emission frequency references and for producing left and right focused in-phase and quadrature signals,computation means for deriving in-phase and quadrature Doppler signals for the beam direction and for the transverse direction realized by combining four signals representing the differences of the focused left and right in-phase and quadrature signals and the sums of the focused left and right in-phase and quadrature signals,a range gate for extracting analog samples from said Doppler signals after every pulse transmission at a time corresponding to reception of echoes backscattered from the sample volume, anda Doppler processor for deriving from sets of said analog samples two components of flow velocity parallel to and transverse to the beam direction.
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Abstract
Two components of the velocity of blood or similar liquids and the true flow vector are derived by a linear transducer array cross-beam configuration. Ultrasound pulses are transmitted from the center elements and backscattered echoes are received by left and right receiver sub-arrays whose locations depend on the observation point. A duplex imaging system with a sector scanner incorporates a Doppler modality with little added complexity and provides components of flow velocity parallel to and transverse to the acoustic beam direction from which the true velocity vector is computed.
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Citations
17 Claims
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1. A steered beam ultrasound instrument for measuring two components of the flow velocity of blood and similar liquids comprising:
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a linear transducer array for transmitting pulses of ultrasound with a preselected emission frequency and for generating received echo signals, said array being comprised of a row of elements divisible into a transmitter sub-array and into left and right receiver sub-arrays that are variably located such that received center wave vectors through any observation point in the field of view subtend approximately equal angles with respect to a transmitter wave vector through the observation point, means for exciting the elements of said transmitter sub-array to sequentially generate ultrasound pulses that propagate along a designated beam direction and insonify a sample volume through which the true flow velocity vector is being determined, left and right receiver means for coherently demodulating echo signals generated by the respective sub-arrays with phase quadrature emission frequency references and for producing left and right focused in-phase and quadrature signals, computation means for deriving in-phase and quadrature Doppler signals for the beam direction and for the transverse direction realized by combining four signals representing the differences of the focused left and right in-phase and quadrature signals and the sums of the focused left and right in-phase and quadrature signals, a range gate for extracting analog samples from said Doppler signals after every pulse transmission at a time corresponding to reception of echoes backscattered from the sample volume, and a Doppler processor for deriving from sets of said analog samples two components of flow velocity parallel to and transverse to the beam direction. - View Dependent Claims (2, 3, 4, 5)
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6. A steered beam ultrasound instrument for measuring the true flow velocity of blood and similar liquids comprising:
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a linear transducer array comprised of a row of transducer elements divisible into a central transmitter sub-array and into left and right receiver sub-arrays that are variably located such that straight lines between any observation point in the field of view and the centers of said receiver sub-arrays have equal angles with respect to a straight line between the observation point and the center of said transmitter sub-array, transmitter means for exciting the transmitter sub-array elements to sequentially generate pulses of ultrasound with a preselected emission frequency that propagate along a designated beam direction and insonify a sample volume through which the true flow velocity vector is being determined, left and right receiver means for coherently demodulating received echo signals, generated by the elements of the respective sub-arrays, with phase quadrature emission frequency reference signals and for time delaying and summing the demodulated signals to produce focused in-phase and quadrature signals for both the left and right sub-arrays, a Doppler signal computation circuit for deriving two difference signals representing the differences of the left and right focused in-phase and quadrature signals and two sum signals representing the sums of the left and right focused in-phase and quadrature signals, and for combining said four sum and difference signals to produce in-phase and quadrature Doppler processor input signals for the beam direction and for the transverse direction, a range gate for extracting analog samples from said Doppler signals after every pulse transmission at a time corresponding to reception of echoes backscattered from the sample volume, a Doppler processor embodying a complex arithmetic implementation of the Fourier Transform for deriving from sets of said analog samples two components of flow velocity parallel to and transverse to the beam direction, and means for vectorially summing the two components of flow velocity to realize the true velocity vector. - View Dependent Claims (7, 8, 9)
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10. A duplex ultrasonic imaging system having a B-scan and Doppler orientation mode of operation and a subsequent Doppler mode of operation comprising:
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a common linear array of transducer elements for both modes for transmitting pulses of ultrasound with a preselected emission frequency and for generating received echo signals, means for exciting selected elements during B-scan operation to sequentially generate ultrasound pulses that propagate along different beam directions to perform a sector scan of a region being examined, means for coherently demodulating said echo signals using phase quadrature emission frequency references and for time delaying and summing the demodulated signals to produce a focused in-phase and a focused quadrature signal, means for deriving a resultant signal from said focused in-phase and quadrature signals, and a B-scan display for displaying the resultant signals as a visual image of the insonified region, said linear array during Doppler operation being divisible into a transmitter sub-array and into left and right receiver sub-arrays that are variably located such that straight lines between any observation point in the field of view and the centers of said receiver sub-arrays have equal angles with respect to a straight line between the observation point and the center of said transmitter sub-array, means for exciting said transmitter sub-array during Doppler operation to sequentially generate ultrasound pulses that are transmitted along a chosen beam direction intersecting a sample volume through which the true velocity vector is being measured, the received echo signals being coherently demodulated and time delayed as in B-scan mode except that in alternate ultrasound pulse repetition intervals the phase of the phase quadrature references in a left or right group of receiving channels is reversed by π
, and means for generating left and right focused in-phase and quadrature signals,computation means for deriving in-phase and quadrature Doppler signals for the beam direction and transverse direction realized by combining four signals representing the differences and sums of the four left and right focuses signals, a range gate for extracting analog samples from said Doppler signals after every pulse transmission period at a time corresponding to reception of echoes backscattered from the sample volume, a Doppler processor for deriving from sets of said analog samples two components of velocity parallel to and transverse to the beam direction, and means for vectorially summing the two components to realize the time flow velocity vector. - View Dependent Claims (11, 12, 13)
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14. A method of measuring the true flow velocity of blood and similar liquids by use of an ultrasound system having a linear array of piezoelectric elements which are divisible into a central transmitter sub-array and left and right receiver sub-arrays comprising the steps of:
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exciting said transmitter sub-array to sequentially generate pulses of ultrasound that propagate along a chosen beam direction and insonify a sample volume in the object being examined through which the true velocity vector is being determined, locating the positions of said receiver sub-arrays such that center wave vectors through the sample volume subtend approximately equal angles with respect to a transmitter wave vector through the sample volume, and alternately after every pulse transmission detecting received echoes and generating electrical echo signals, processing the echo signals in a left group and right group of receiving channels, each having in-phase and quadrature channels in which the echo signals are coherently demodulated using phase quadrature emission frequency reference signals and are timed delayed and summed to generate left and right focused in-phase and quadrature signals, computing in-phase and quadrature Doppler signals for the beam direction and for the transverse direction from combinations of the four left and right focused signals, gating said Doppler signals for a short interval after every pulse transmission to extract two pairs of analog samples representing echoes backscattered from the sample volume, analyzing sets of said pairs of analog samples with a Doppler processor to realize two components of velocity parallel to and transverse to the beam direction, and vectorially summing the two components to realize the true flow velocity vector. - View Dependent Claims (15, 16)
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17. A method of measuring the transverse component of the flow velocity of blood and similar liquids at right angles to an acoustic beam direction by use of an ultrasound system having a linear array of piezoelectric elements which are divisible into a central transmitter sub-array and left and right receiver sub-arrays, the transverse component to be vectorially summed with a component parallel to the beam direction to realize the true velocity vector, comprising the steps of:
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exciting said transmitter sub-array to sequentially generate pulses of ultrasound that propagate along a chosen beam direction and insonify a sample volume in the object being examined through which the true velocity vector is being determined, locating the positions of said receiver sub-arrays such that center wave vectors through the sample volume subtend approximately equal angles with respect to a transmitter wave vector through the sample volume, and alternately after every pulse transmission detecting received echoes and generating electrical echo signals, processing the echo signals in a left group and right group of receiving channels, each having in-phase and quadrature channels in which the echo signals are coherently demodulated using phase quadrature emission frequency reference signals and are time delayed and summed to generate left and right focused in-phase and quadrature signals, computing in-phase and quadrature Doppler signals for the transverse direction from combinations of the four left and right focused signals, gating said Doppler signals for a short interval after every pulse transmission to extract a pair of analog samples representing echoes backscattered from the sample volume, and analyzing sets of said pairs of analog samples with a Doppler processor to realize the component of velocity transverse to the beam direction.
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Specification