Method for adaptively filtering doppler signals using a complex time domain filter
First Claim
1. A processor for color flow imaging of velocity of scatterers flowing past moving tissue, comprising:
- a source of basebanded signals;
a first velocity estimator for estimating velocity of said tissue based on said basebanded signals;
selection logic means for selecting complex filter coefficients in dependence on at least said estimated tissue velocity;
delay means coupled to receive said basebanded signals;
a complex filter coupled to receive delayed basebanded signals from said delay means and to receive signals representing complex filter coefficients from said selection logic means; and
a second velocity estimator for estimating flow velocity of said scatterers based on said filtered basebanded signals.
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Abstract
A time domain technique for implementing an adaptive wall filter improves imaging of low-velocity blood flow by removing signals associated with slowly moving tissue. Adaptive wall filtering is performed by estimating wall velocity and bandwidth, and then filtering the basebanded data with a complex time domain notch filter. The wall velocity estimate determines the center frequency of a wall signal while the wall variance estimate determines the wall signal bandwidth. The complex filter coefficients selected are those which will center the complex notch filter on the wall center frequency, and which will set the filter cutoff frequencies (measured from this center frequency) to match the wall signal bandwidth.
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Citations
23 Claims
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1. A processor for color flow imaging of velocity of scatterers flowing past moving tissue, comprising:
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a source of basebanded signals; a first velocity estimator for estimating velocity of said tissue based on said basebanded signals; selection logic means for selecting complex filter coefficients in dependence on at least said estimated tissue velocity; delay means coupled to receive said basebanded signals; a complex filter coupled to receive delayed basebanded signals from said delay means and to receive signals representing complex filter coefficients from said selection logic means; and a second velocity estimator for estimating flow velocity of said scatterers based on said filtered basebanded signals. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method for color flow imaging of velocity of scatterers flowing past moving tissue, comprising the steps of:
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acquiring basebanded data; estimating velocity of said tissue from said basebanded data; selecting complex filter coefficients in dependence on at least said estimated tissue velocity; delaying said basebanded data; filtering said delayed basebanded signals in accordance with said selected complex filter coefficients; and estimating flow velocity of said scatterers from the filtered basebanded data. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15)
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16. A color flow imaging system for imaging velocity of scatterers flowing past moving tissue, comprising:
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a plurality of transducers arranged in a sequence to form an array; means for selectively operating said transducers in a transmission mode to produce propagating vibratory energy pulses from electrical driving signals; means for selectively operating said transducers in a reception mode to produce analog electrical detection signals in response to detection of reflected vibratory energy pulses; means responsive to said analog electrical detection signals for converting said analog electrical detection signals into basebanded signals; first velocity estimation means for estimating velocity of said tissue based on said basebanded signals; selection logic means for selecting complex filter coefficients in dependence on at least said estimated tissue velocity; delay means coupled to receive said basebanded signals from said supplying means; filter means coupled to receive delayed basebanded signals from said delay means and to receive signals representing complex filter coefficients from said selection logic means; correlation means coupled to receive filtered basebanded signals from said filter means; and second velocity estimation means for estimating flow velocity of said scatterers based on said filtered basebanded signals. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23)
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Specification