Abstract

A probe set in contact with a subject under examination emits ultrasonic waves, scanning a sectional plane of the subject. The probe receives the waves reflected from the sectional plane, thereby acquiring tomography data and velocity data. Frames of tomography data and frames of velocity data are stored. After completion of the scanning, a tomography image of the sectional plane is reproduced from the tomography data and is displayed. An operator sets a region of interest (ROI) on the tomography image displayed. A blood flow velocity distribution, a blood stream volume or a tissue velocity distribution is calculated from the velocity data corresponding to the ROI. That is, the operator can devote himself to an operation of fitting the scanning plane of the probe to an optimum sectional plane of the body during a scan and to an operation of setting the ROI in an optimum position while tomography images are being reproduced. In other words, the operator is relieved of the burden of performing the probe operation and the ROI setting operation simultaneously. Thus, it becomes easy to fit the scanning plane to the optimum plane and to set the ROI in the optimum position.