| 摘要 |
<p>An ultrasonic diagnostic apparatus for forming a sectional image of a subject by either a movable focusing system or a variable aperture system based upon echoes obtained by applying ultrasonic radiation onto the subject. The echoes from the subject are converted (100, 102) into signals depending upon their intensities, and different time delays are imparted thereto to form (110, 112) signals that correspond to different depths in the subject. Among the latter signals, those corresponding to particular depths are selectively combined (108, 113A, 113B, 114A, 114B, 116A, 116B, 118A, 118B, 120, 122A, 122B, 124), and thereby a sectional echo image of the subject is visually displayed (126, 128, 130). In changing the depth or aperture, the level of the combined signal (204) from the adder (120) is adjusted depending on the delay time defined by the delay circuits (116A, 116B) such that the average level of the combined signal (204) at the time of change will become substantially the same as that in the ordinary condition. Therefore, the change in sensitivity due to a change in the focal point or the aperture can be minimized, and a high azimuthal resolution is obtained.</p> |
