this invention provides an ultrasonic imaging system that implements imaging by distinguishing sharply and definitely the echo components generated by scattering in a microbubble contrast medium , from the tissue harmonic components generated by nonlinear propagation of a transmitted pulse . this ultrasonic imaging system , constructed to transmit / receive ultrasonic pulses to / from a living body and form a contrast image of the inside of the living body by using the contrast - imaging microbubbles , repeats the transmitting / receiving operations four times in all , under the same transmitting / receiving focus conditions at different phase angles = 0 °, = 120 °, =− 120 °, = 180 °] of the carrier of a transmitted pulse wave including a common envelope signal , sums up three time - series receive echo signals associated with , , , forms the contrast image , sums up two time - series receive echo signals associated with , , forms an image of the living body having a nonlinear pulse propagation property , and makes a superimposed display of the two kinds of images .