METHODS FOR INCREASING THE LATERAL RESOLUTION OF B-SCAN.

Abstract

B-scan displays a picture of a cross-section through the body and is widely used in ultrasonic diagnosis. The main deficiency of B-scan is the low lateral resolution, which has its origin in the large diameter of the ultrasound beam. The first system described is a synthetic aperture sonar system working at 2 MHz ( lambda equals 0. 75 mm in water). The important features of the system and the optical processing are given. A second system uses an annular transducer for focussing the ultrasound beam over a depth of 20 cm. The side lobes are reduced by subtracting an echo signal. All systems have a lateral resolution of 2 to 3 mm and thus almost one order of magnitude better than conventional B-scan.