Three-dimensional determination of gastric ulcer size with laser endoscopy.

We have developed a new endoscopic system for measuring the three-dimensional structure of the gastric ulcer. The system consists of an argon ion laser generator, a side-viewing endoscope with diffraction grating made of glass fibers, and a graphic processing unit. Via a fiber grating fitted in the tip of the endoscope, about 1600 light spots produced by the diffracted laser beam were projected on to the gastric mucosa. By graphic processing involving the detection of the deviation of the laser spot array on the gastric lesion, the diameter, area, and height or depth of the lesion could be determined. To evaluate the accuracy of the system, the diameter and area of a rubber disc were determined in vitro and in the stomach. A cubic model 10 mm in height was used to evaluate the accuracy of the system in measuring height. Accuracy proved to be satisfactory for clinical use. The course of healing of 6 gastric ulcers treated by histamine receptor antagonist was followed with the system. A linear decrease in diameter and depth of the ulcer was observed.