25 megahertz gastrointestinal ultrasonography

Endoscopic gastrointestinal ultrasonography provides the only method of in vivo evaluation of all gastrointestinal wall layers and surrounding structures. Higher frequencies (7.5 and 12 MHz) have been used due to the proximity of the transducer to the bowel wall. In an attempt to define the tissue characteristics at a macroscopic level and differentiate their structural content as a function of backscattering, the authors have employed a 25-MHz transceiver, high-speed digitizer, and high-resolution display in a conventional in vitro pulse-echo system. A linear B-mode scan constructed from digitized A-modes is stored in the microcomputer and displayed in gray scale (256 levels) on a high-resolution monitor. Transducer characterization yielded focal lateral and axial resolutions of 200 μm and 100 μm, respectively