Patent ID: 6296612
Filing Date: 2001-10-02
Classification: A61B,G01S

Abstract:
A system for imaging ultrasound scatterers, comprising:a transmitter for transmitting a multiplicity of pulses of ultrasound into a sample volume of ultrasound scatterers, said multiplicity of pulses forming a packet;a receiver for acquiring a multiplicity of sucessive samples of Doppler signals backscattered from said sample volume of ultrasound scatterers;a display monitor comprising columns of pixels;a processor for processing said Doppler signals to produce spectral line data representing velocity for continuous display of a succession of spectral lines during 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 scale in a respective pixel of a corresponding column of pixels on said display monitor, said processor comprising:a demodulator for demodulating said Doppler signal samples into in-phase and quadrature components;an integrator for integrating the in-phase and quadrature components over a specific time interval;first and second wall filters for substantially rejecting clutter in the integrated in-phase and quadrature components corresponding to stationary or very slow-moving tissue;cutoff frequency selection means for selecting the cutoff frequencies of said first and second wall filters as a function of the clutter power of said integrated in-phase and quadrature components; anda spectrum analyzer for producing spectral power data by Fast Fourier transformation of the wall-filtered in-phase and quadrature components,wherein said cutoff frequency selection means comprise:a low pass filter for rejecting flow frequency components in said integrated in-phase and quadrature components which are above a clutter frequency range;means for computing the total power of the output of said low pass filter;means for providing an estimate of the mean system noise power in said low pass filter output;means for comparing the total power of said low pass filter output to the mean system noise power in said low pass filter output; andfilter coefficient selection means for selecting wall filter coefficients which are a function of the results of comparing the total power to the mean system noise power.