Abstract

In an ultrasonic diagnostic apparatus in which ultrasonic echo beams is focused three-dimensionally, a probe employs plural transducers arranged in two directions, lateral and azimuth directions. The transducers arranged in each azimuth direction are connected to a transmitting-receiving channel in a transmitting-receiving portion via a switch circuit. The switch circuit operates on the control of a switching controller and can connect a transducer selected by the controller in the azimuth direction to the transmitting-receiving channel. Output signals from the transmitting-receiving portion are supplied to a signal processing portion, in which beam forming for three-dimension echo beams is carried out by using a beam former. Thus, transducers arranged on each line in the lateral direction can be driven simultaneously, resulting in a more compact circuit and a reduced number of transmitting and receiving for better real-time processing. Further, the beam former is devided into two stage, one for the lateral direction and the other for the azimuth direction. This combination of two beam formers lead to adjustable focuses in the both direction in addition to a reduced memory capacity in the signal processing.