DIAGNOSTIC ULTRASOUND SYSTEM

A diagnostic ultrasound system is provided for displaying a color image of a motion of a tissue scans an ultrasonic pulse signal along a tomographic plane to acquire an electrical echo signal, extracts a Doppler signal from the echo signal, calculates velocity data concerning the motion of the tissue for respective sample points on the tomographic plane on the basis of the Doppler signal, and forms data of a B-mode tomographic image on the basis of the echo signal. The system comprises an element for setting a scale along which each of the velocity data over a measurable band of frequencies of the Doppler signal is assigned to each gradation data for color display, the measurable band of frequencies being limited by a pulse repetition frequency of the ultrasonic pulse signal and a given low-velocity band of the measurable frequency band being enhanced in the gradation data than a remaining velocity band of the measurable band, an element for converting the velocity data into the gradation data according to the scale, an element for blanking either one of the converted gradation data and the calculated velocity data at every sample point when each of them exceeds a specified threshold, and an element for displaying the velocity color image subjected to blanking and superimposed on the B-mode tomographic image.