Ultrasonic imaging system utilizing dynamic and pseudo-dynamic focusing

摘要

A phased array ultrasonic imaging system is disclosed which combines aspects of both dynamic and pseudo-dynamic focusing. The system includes a linearly arranged array of side-by-side transducers adapted for propagating ultrasonic energy into a body to be ultrasonically examined and for receiving reradiated sonic energy from points within the body. A signal channel is connected to each of the transducers for activating same to propagate the sonic energy and for receiving electrical signals from the transducers (which correspond to the reradiated energy). Controllable delay means are provided in each of the channels for introducing linear phase shifts in the electrical signals proceeding in the channels during both transmission and reception to thereby azimuthally steer the transducer array. Means are further provided for processing the received signals proceeding through the channels and for combining same to effect a visual display of the bodily portion being examined. Means synchronized with the activating of the transmitters periodically reduce the gain of one or more symmetric outer transducer pairs of the array, thereby effecting reducing the aperture of the array to enable improved response to reflected acoustic information reaching the array from the near field thereof. The outer elements are similarly restored to enlarge the effective array aperture for improved response to reflected acoustic information arising from the far field of the array. Pursuant to the improvement of the invention, means are provided for adjusting the focal length of the array coincident with the aforementioned change in gain of the one or more outer transducer pairs, i.e., coincident with a change in effective aperture of the array in order to thereby maintain or achieve a desired resolution within a specified focal range.