1982 Volume 24 Issue 2 Pages 225-233_1
As a purpose to determine the size of gastric ulcer endoscopically, an experimental model was designed and basic experiment was done. Rubber disk, 5mm in diameter was used as a marker. This marker disk was set in the center of a round object, 25mm in diameter, simulating an ulcer. Using endoscope, this model was photographed at various Lens-Object-Dis-tance (LOD). At first, the ratio of the object to marker disk area on the pictures enlarged in cabinetsize were calculated. An aberration ratio was less than 10% by using GTF-B100 in over 3cm of LOD and in over 5cm of LOD by GIF-P2, so that the precise area of the object disk was calculated without correcting optical distortion (Table 1, 2). However, the aberration ratio to the true ratio was more than 10% by using GTF-B100 in less than 3cm of LOD and in less than 5cm of LOD by GIF-P2. The increasement of the aberration ratio in the latter was due to more marked optical distortion of wide angle lens used for the fiberscope. Secondarily, in order to correct the optical distortion of fiberscope, a transparent board traced an endoscopic photograph of graph paper in the same LOD was employed in measurement when GTF-B100 was used in less than 3cm of LOD and when GIF-P2 in less than 5cm of LOD (Table 5). By use of the board, the aberration ratio became less than 10%. Therefore, it became possible to determine the precise area of the object disk endoscopically even in such short LOD. Accordingly, it became possible to determine the precise area of gastric ulcer by this marker disk method.
