A novel method for the measurement of flow direction in pulsed Doppler systems

Blood flow direction was measured using a correlation method that ensures determination of the amount that the scatterers move between two transmitted pulses. A transducer was used for transmission of ultrasonic bursts and reception of its echo. At the receiving transducer, the signal involves the sum of all the individual echos from each of the acoustic particles, delayed by the time that the ultrasound takes to travel from the source transducer to the particle and back to the receiving transducer. The echo that comes form the blood consists of the sum of all the echoes from the scattering particles within blood. Therefore, the echo from the blood will also be characterized by a spectral band. The transmitted pulse has a spectrum which centered about resonant frequency of the transducer. By the summation of these variables, which are independent, bandpass Gaussian amplitude modulated echoes appears as a bandpass white Gaussian noise (BPWGN). One of the important characteristics of BPWGN is the sharpness of the bandpass region where the Q is the center frequency divided by the 3-dB bandwidth.<>