To provide an adaptive multi-dimensional beam pattern with approximately instantaneous conversion for an ultrasonic imaging system employing a multi-dimensional sensor layout.

In a first step, the multi-dimensional beam pattern is divided into subapertures. Next, each subaperture is divided into two interferential subsets of the beam pattern with a round/linear layout in the directions of different coordinates in the multi-dimensional layout. Introduction of the multi- dimensional beam pattern establishes the base of a 3D ultrasound imaging system comprising a small multi-dimensional sensor layout and a device to be arranged at site, and a three-dimensional image with high resolution is generated in real time. Furthermore, a four-dimensional image in which a fourth dimension is time can be obtained, and the obtained image forms video images of operations of many organs.