Real-Time Spectrum Analysis and Display of Directional Doppler Ultrasound Blood Velocity Signals

Development of a real-time system for three-dimensional display of Doppler shifted frequencies within an ultrasound flowmeter signal is described. The device is based on a fast Fourier transform (FFT) spectrum analyzer which provides both high frequency and time resolution over a variable range of frequencies up to 40 kHz. Signal preprocessing filters unwanted low frequency artifacts due to arterial wail motion and automatically controls input gain to limit peak amplitudes while matched phase shift networks translate forward and reverse components for a directional output. A digital first moment is calculated and the display may be viewed in a continuous or freeze frame mode. Clinical applications underway have shown improved detail and accuracy in the use of ultrasound for diagnosing various vascular abnormalities.