Apparatus and method for estimating missing doppler signals and spectra
First Claim
1. In an ultrasound imaging system, a method comprising the steps ofreceiving a sequence of Doppler signals, said sequence of Doppler signals having at least one region comprising data and at least one gap;
- determining a first set of parameters of a Doppler signal model in response to said sequence of Doppler signals, whereby said Doppler signal model approximates said sequence of Doppler signals in said region comprising data;
determining a second set of parameters of said Doppler signal model, responsive to said first set of parameters, for said gap;
synthesizing a set of Doppler information for said gap in response to said second set of parameters; and
combining a set of Doppler information for said region comprising data with said set of Doppler information for said gap.
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Abstract
The invention provides a method and system for estimating missing Doppler signals and spectra in an ultrasound imaging system: (1) parameters representative of a Doppler data model are matched to actual Doppler data that is received; (2) the parameters are interpolated or extrapolated (possibly after normalization, smoothing, or other manipulation) for regions where actual Doppler data is missing ("Doppler gaps"); and (3) a set of synthesized Doppler spectra are constructed, using the model and the interpolated or extrapolated parameters, for those Doppler gaps. The Doppler data model is an autoregressive model, or another model in which the Doppler data may be approximated by supplying a source signal to an autoregressive filter. The parameters of the model comprise a set of autoregressive filter coefficients and a σ2 (variance) value. The reflection coefficients of these autoregressive filter coefficients are determined. The reflection coefficients and σ2 value for a Doppler gap are interpolated from reflection coefficients and σ2 values from at least one block of Doppler data before the Doppler gap and at least one block of Doppler data after the Doppler gap. In a preferred embodiment, a windowing function may be used when combining the actual Doppler data with the synthesized Doppler data. A set of synthesized Doppler spectra may also be determined in response to the Doppler data near the Doppler gap. A white noise source having the interpolated σ2 value may be generated and filtered using an autoregressive filter having the interpolated reflection coefficients, to produce a set of synthesized Doppler data.
78 Citations
37 Claims
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1. In an ultrasound imaging system, a method comprising the steps of
receiving a sequence of Doppler signals, said sequence of Doppler signals having at least one region comprising data and at least one gap; -
determining a first set of parameters of a Doppler signal model in response to said sequence of Doppler signals, whereby said Doppler signal model approximates said sequence of Doppler signals in said region comprising data; determining a second set of parameters of said Doppler signal model, responsive to said first set of parameters, for said gap; synthesizing a set of Doppler information for said gap in response to said second set of parameters; and combining a set of Doppler information for said region comprising data with said set of Doppler information for said gap. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. In an ultrasound imaging system, a method for processing ultrasound imaging signals, comprising
receiving a sequence of Doppler signals, said sequence of Doppler signals having at least one gap between a first region comprising data and a second region comprising data; -
determining a first variance and a first set of coefficients for a first autoregressive model in response to said sequence of Doppler signals in said first region comprising data, whereby said first autoregressive model with said first set of coefficients and said first variance approximates said sequence of Doppler signals in said first region comprising data; determining a first set of reflection coefficients in response to said first set of coefficients; determining a second variance and a second set of coefficients for a second autoregressive model in response to said sequence of Doppler signals in said second region comprising data, whereby said second autoregressive model with said second set of coefficients and said second variance approximates said sequence of Doppler signals in said second region comprising data; determining a second set of reflection coefficients in response to said second set of coefficients; interpolating said first and second sets of reflection coefficients to determine a new set of reflection coefficients for said gap; synthesizing a set of Doppler signal spectra for said gap in response to said new set of reflection coefficients; and combining said Doppler signal spectra using at least one windowing function for said first region comprising data, said gap, and said second region comprising data. - View Dependent Claims (17, 18)
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19. Apparatus comprising
means for receiving a sequence of Doppler signals, said sequence of Doppler signals having at least one region comprising data and at least one gap; -
means for determining a first set of parameters of a Doppler signal model in response to said sequence of Doppler signals, whereby said Doppler signal model approximates said sequence of Doppler signals in said region comprising data; means for determining a second set of parameters of said Doppler signal model, responsive to said first set of parameters, for said gap; means for synthesizing a set of Doppler information for said gap; and means for combining a set of Doppler information for said region comprising data with said set of Doppler information for said gap. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33)
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34. Apparatus comprising
means for receiving a sequence of Doppler signals, said sequence of Doppler signals having at least one gap between a first region comprising data and a second region comprising data; -
means for determining a first variance and a first set of coefficients for a first autoregressive model in response to said sequence of Doppler signals in said first region comprising data, whereby said first autoregressive model with said first set of coefficients and said first variance approximates said sequence of Doppler signals in said first region comprising data; means for determining a first set of reflection coefficients in response to said first set of coefficients; means for determining a second variance and a second set of coefficients for a second autoregressive model in response to said sequence of Doppler signals in said second region comprising data, whereby said second autoregressive model with said second set of coefficients and said second variance approximates said sequence of Doppler signals in said second region comprising data; means for determining a second set of reflection coefficients in response to said second set of coefficients; means for interpolating said first and second sets of reflection coefficients to determine a new set of reflection coefficients for said gap; means for synthesizing a set of Doppler information for said gap in response to said new set of reflection coefficients; and means for combining said Doppler information using at least one windowing function for said first region comprising data, said gap, and said second region comprising data. - View Dependent Claims (35, 36, 37)
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Specification