| 摘要 |
Calculation of the two-dimensional velocity vector (17) of liquid flowing through a region (3, 16) which is imaged in a B-mode ultrasonic echoscopy display involves dividing the region into a number of small, preferably rectangular, cells (4). One of the cells is scanned rapidly, at least twice, by a beam of ultrasonic energy which is transmitted sequentially along a number of lines of sight (2) which intersect the cell. An image of the cell is formed from the signals reflected from scatterers within the liquid in the cell during each scan of the cell. The two-dimensional brightness functions, S(x,y), of each image of the cell form of a data set S(x,y,t) after the repeated scanning. The data set S(x,y,t) is integrated separately with respect to x and y by projection onto the (x,t) and (y,t) planes. Using the projected functions of S(x,y,t), the average velocity of the scatterers in the cell (and hence of the liquid flowing through the cell) is obtained in the x-direction and in the y-direction. From these two average velocities, the magnitude and direction of the two-dimensional velocity vector is obtained, and displayed on the echogram. The scanning, imaging and computational procedures are then repeated for another of the cells. <IMAGE> |
