Method and apparatus for ultrasonic synthetic transmit aperture imaging using orthogonal complementary codes
First Claim
1. A system for imaging ultrasound scatterers, comprising:
- an ultrasound transducer array including a multiplicity of transducer elements for transmitting ultrasound waves and detecting ultrasound echoes reflected by said ultrasound scatterers;
transmit means coupled to said transducer array for pulsing a first number N of transducer elements, for N transmit events, with signals derived from N orthogonal complementary code sets, each of said code sets comprising N complementary code sequences;
receive means coupled to said transducer array for receiving signals from a second number M of transducer elements of said multiplicity following each of said N transmit events, each set of signals received at said M transducer elements representing a respective received data sequence;
analog-to-digital conversion means for converting each of the N×
M received signals into a respective digital signal;
means for decoding the N×
M digital signals by computing the sum of the N received data sequences cross-correlated with the N orthogonal complementary code sequences transmitted from each respective one of said N transducer elements to form a decoded data set for said each respective one of said N transducer elements;
beamforming means for forming a beamformed data set from the decoded data sets; and
means (24) for displaying an image that is a function of said beamformed data set.
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Abstract
Signal-to-noise ratio in synthetic transmit aperture imaging is significantly increased by encoding the transmit signals in orthogonal complementary codes for multiple point sources to be transmitted simultaneously. A number N of elements of a transducer array are simultaneously activated to transmit unfocused ultrasound waves during each one of N transmit events. For each transmit event, a different set of N code sequences is applied by a controller to N pulsers for the transducers to drive the transducers. The imaging depth is divided into several zones and code lengths are employed which increase with depth. A Hadamard construct of the orthogonal complementary sets, which requires only 2N correlations for decoding, is used.
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Citations
17 Claims
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1. A system for imaging ultrasound scatterers, comprising:
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an ultrasound transducer array including a multiplicity of transducer elements for transmitting ultrasound waves and detecting ultrasound echoes reflected by said ultrasound scatterers; transmit means coupled to said transducer array for pulsing a first number N of transducer elements, for N transmit events, with signals derived from N orthogonal complementary code sets, each of said code sets comprising N complementary code sequences; receive means coupled to said transducer array for receiving signals from a second number M of transducer elements of said multiplicity following each of said N transmit events, each set of signals received at said M transducer elements representing a respective received data sequence; analog-to-digital conversion means for converting each of the N×
M received signals into a respective digital signal;means for decoding the N×
M digital signals by computing the sum of the N received data sequences cross-correlated with the N orthogonal complementary code sequences transmitted from each respective one of said N transducer elements to form a decoded data set for said each respective one of said N transducer elements;beamforming means for forming a beamformed data set from the decoded data sets; and means (24) for displaying an image that is a function of said beamformed data set. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method for acquiring ultrasound scattering data, comprising the steps of:
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driving a first number N of transducer elements of a multiplicity of transducer elements in an array, for N transmit events, with pulses derived from N orthogonal complementary code sets, each of said code sets comprising N complementary code sequences, said driving of N transducer elements being performed once for each respective one of said N orthogonal complementary code sequences within each of said code sets; receiving signals from a second number M of transducer elements of said multiplicity following each of said N transmit events, each set of signals received at said M transducer elements representing a respective received data sequence; converting each of the N×
M received signals into a respective digital signal;decoding the N×
M digital signals by computing the sum of the N received data sequences cross-correlated with the N orthogonal complementary code sequences transmitted from each respective one of said N transducer elements to form a decoded data set for said each respective one of said N transducer elements; andforming a beamformed data set from the decoded data sets. - View Dependent Claims (12, 13, 14)
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15. A method for imaging ultrasound scatterers in a field of view, comprising the steps of:
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driving a first set of transducer elements of a multiplicity of transducer elements in a transducer array, during each one of a first plurality of transmit events, with pulses derived from a first set of orthogonal complementary code sequences having a first length, each transmit event of said first plurality comprising driving said first set of transducer elements with a respective one of said first set of orthogonal complementary code sequences; receiving signals from a second set of transducer elements following each of said transmit events of said first plurality to form a first received data set of received data sequences corresponding to ultrasound scatterers located at a first range of depth relative to the transducer array; converting each of said received data sequences of said first received data set into a respective digital signal to form a first set of digital signals; decoding said first set of digital signals by computing the sum of the received data sequences of said first received data set cross-correlated with the respective orthogonal complementary code sequences of said first set of orthogonal complementary code sequences to form a first decoded data set for each one of said first set of transducer elements; forming a first beamformed data set from the first decoded data sets; and displaying a first image which is a function of said first beamformed data sets. - View Dependent Claims (16, 17)
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Specification