Ultrasonic diagnosing apparatus

Abstract

The ultrasonic diagnosing apparatus including an ultrasonic probe, an ultrasonic wave transmitting and receiving unit for transmitting ultrasonic pulses toward a living body and receiving ultrasonic waves reflected by the living body to produce an echo signal, and a signal processing circuit for processing the echo signal such that a Doppler frequency representing a relative movement between the ultrasonic probe and living tissues is detected and a velocity of a blood stream which is free from the influence of the relative movement is detected on the basis of the Doppler frequency due to the relative movement between the ultrasonic probe and the living tissues. In a power spectrum distribution, the Doppler frequency can be detected as a peak frequency at which the magnitude of the power spectrum becomes maximum. In one embodiment of the ultrasonic diagnosing apparatus, the frequency axis of the power distribution is shifted such that the Doppler frequency becomes zero, and finally a Doppler frequency due to the blood stream is detected from a power spectrum component outside a cut-off frequency range. In a second embodiment, a first Doppler frequency due to the blood stream is detected from a signal component which is obtained by MTI filters and auto-correlation circuits, a second Doppler frequency due to the relative movement between the ultrasonic probe and the living tissues is detected from a signal component which is obtained by the auto-correlation circuits, and then a velocity of the blood stream is detected from a difference between the first and second Doppler frequencies.