Ultrasonic wave diagnostic apparatus to concurrently display an echo signal and a reference signal

Abstract

A signal, which is the sum of an ultrasonic wave echo signal and a group of PPM (pulse-position-modulated) pulses representative of a reference signal, is applied to a cathode ray tube (CRT) and is swept along one axis by a first sweeping signal with a first frequency and along a second axis by a second sweeping signal of lower frequency. The ultrasonic echo signal and the group of PPM pulses are concurrently displayed on the CRT. Ultrasonic wave rate pulses synchronous with the first sweeping signal are applied at the first frequency to an ultrasonic transducer to emit ultrasonic waves which upon receipt are converted to an ultrasonic wave echo signal. A sawtooth wave generator circuit is provided for generating a sawtooth wave with a second frequency n times the first frequency. Here, n is an integer and equal to or larger than 2. The reference signal, such as an electrocardiographic signal, is modulated by the sawtooth wave to produce a train of pulse-position-modulated (PPM) pulses. Electronic circuitry rearranges the PPM pulses produced during a period of the rate pulse to fit within the period of a selected sawtooth wave included in the rate pulse period. The ultrasonic wave echo signal and the PPM pulses representing samples of the reference signal are added and displayed on a cathode ray table to form an M-mode image and a representation of the reference image. For every display of the ultrasonic wave echo signal corresponding to an ultrasonic wave pulse displayed, n PPM pulses representing the reference signal are displayed.