A new method for the endoscopic determination of gastrointestinal ulcer area.

Current endoscopic measurements of gastrointestinal ulcer area using forceps or graduated probes are associated with a high degree of inaccuracy. Based on a computer-assisted, semiautomatic device for stereological analyses, we have developed a new method for the endoscopic determination of ulcer size. The basic elements are a graphical measuring tablet coupled with a computer, the later being connected to TV-monitor. The endoscopic picture is transmitted to the TV-monitor and the ulcerated area is measured directly on the TV-monitor by means of an electronic overlay marker. The trace of the marker remains visible on the screen so that any circumscribed lesion can be labelled exactly. From the relation of a known, endoscopically introduced reference area to the circumscribed ulcerated area, the latter is calculated by the computer. Multiple measurements obtained at different distances, and visual angles, and with different reference areas, revealed an error of 4.2 +/- 0.5%. Inter-observer variation among 6 different examiners was 2.9 +/- 1.2%. These results document the reliability of endoscopic planimetry of gastrointestinal ulcers.