Method and apparatus for automatic tracing of Doppler time-velocity waveform envelope
First Claim
1. A method for automatic tracing of a Doppler velocity-time waveform envelope on a display monitor, comprising the steps of:
- transmitting pulses of ultrasound into a sample volume of ultrasound scatterers;
acquiring a multiplicity of successive samples of Doppler signals backscattered from said sample volume of ultrasound scatterers;
processing said Doppler signals to produce spectral line data representing velocity for continuous display of a succession of spectral lines during the continuation of Doppler signal acquisition, the data for each spectral line comprising a multiplicity of frequency bins for different frequency intervals, each bin containing spectral power data for a respective frequency interval, the spectral power data in each bin for each spectral line being displayed as a grey scale in a respective pixel of a corresponding column of pixels on the display monitor;
for each spectral line, estimating a respective mean spectral noise power, determining a respective spectral noise threshold calculated as a function of said respective estimated mean spectral noise level, and estimating a highest frequency for those frequency bins having a spectral power which exceeds said respective spectral noise threshold; and
tracing an envelope through the pixels corresponding to said frequency bins of highest frequency having a spectral power exceeding said respective spectral noise thresholds.
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Abstract
An analytical method for automatic tracing of a Doppler time-velocity waveform envelope. At the core of this algorithm is a maximum frequency detection mechanism which is based on searching for the highest frequency bin whose spectral amplitude exceeds a certain noise threshold. The method is based on a theoretical noise amplitude distribution in the video spectral domain. In particular, the method uses a precise model of the statistical distribution of the video spectral power of white noise to establish a threshold for maximum frequency detection. Input to the noise model is the average white noise level in the video spectral display, which can be computed using either of two analytical methods.
71 Citations
20 Claims
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1. A method for automatic tracing of a Doppler velocity-time waveform envelope on a display monitor, comprising the steps of:
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transmitting pulses of ultrasound into a sample volume of ultrasound scatterers; acquiring a multiplicity of successive samples of Doppler signals backscattered from said sample volume of ultrasound scatterers; processing said Doppler signals to produce spectral line data representing velocity for continuous display of a succession of spectral lines during the continuation of Doppler signal acquisition, the data for each spectral line comprising a multiplicity of frequency bins for different frequency intervals, each bin containing spectral power data for a respective frequency interval, the spectral power data in each bin for each spectral line being displayed as a grey scale in a respective pixel of a corresponding column of pixels on the display monitor; for each spectral line, estimating a respective mean spectral noise power, determining a respective spectral noise threshold calculated as a function of said respective estimated mean spectral noise level, and estimating a highest frequency for those frequency bins having a spectral power which exceeds said respective spectral noise threshold; and tracing an envelope through the pixels corresponding to said frequency bins of highest frequency having a spectral power exceeding said respective spectral noise thresholds. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A system for automatic tracing of a Doppler velocity-time waveform envelope on a display monitor, comprising:
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means for transmitting pulses of ultrasound into a sample volume of ultrasound scatterers; means for acquiring a multiplicity of successive samples of Doppler signals backscattered from said sample volume of ultrasound scatterers; a display monitor comprising columns of pixels; means for processing said Doppler signals to produce spectral line data representing velocity for continuous display of a succession of spectral lines during the continuation of Doppler signal acquisition, the data for each spectral line comprising a multiplicity of frequency bins for different frequency intervals, each bin containing spectral power data for a respective frequency interval, the spectral power data in each bin for each spectral line being displayed as a grey scale in a respective pixel of a corresponding column of pixels on said display monitor; means for estimating a respective mean spectral noise power for each spectral line; means for determining a respective spectral noise threshold for each spectral line, calculated as a function of said respective estimated mean spectral noise level; means for estimating for each spectral line a highest frequency for those frequency bins having a spectral power which exceeds said respective spectral noise threshold; and means for tracing an envelope through the pixels corresponding to said frequency bins of highest frequency having a spectral power exceeding said respective spectral noise thresholds. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification