A new ultrasonic probe for endosonographic imaging of the upper GI-tract. Preliminary observations.

A new ultrasonic probe (7.5 MHz, diameter 3.7 mm) was used in vitro in 3 gastric resection specimens and in vivo in 12 patients in an attempt to visualize normal and pathological wall structure of the esophagus, stomach and duodenum via the working channel of a gastroscope, and of the biliary tract via the percutaneous approach. In 5 of these patients conventional endosonography was performed. The probe visualizes the normal layer structure and pathological lesions of the upper GI-tract wall, since it can be accurately positioned at the structure of interest under visual control; water is instilled into the hollow organs to improve transmission of the ultrasound beam. Intra- and transmural changes such as blood vessels in the wall of the esophagus and stomach in portal hypertension, or gastric and esophageal tumors were demonstrated. The important advantage of the probe is that it can be used in stenosed or narrowed hollow organs, where conventional endosonography fails. However, the depth of penetration of the ultrasonic beam (10-15 mm) and circumferential imaging of the gastric wall are still inferior to those of conventional endoscopic ultrasound. As the focus distance of the ultrasound probe to the biliary ducts is too small, visualization of the biliary system is incomplete. Technical improvements could make this new probe an irreplacable diagnostic tool in the future.