Preliminary evaluation of the prototype stereoscopic endoscope: precise three-dimensional measurement system.

A prototype stereoscopic endoscope (incorporating two charged-coupled devices), developed for the accurate three-dimensional measurement of gastrointestinal tract lesions, was initially evaluated with two-dimensional target grids and in vitro measurement of 15 objects of known size (marbles, cubes, and rectangular prisms) placed in a plastic model of the sigmoid colon. Images of the objects were captured and stored in a computer. Stereoscopic measurements were compared with results from the standard (open biopsy forceps) method by a blinded endoscopist. The volume measured with the stereoscope did not differ significantly from the true volume, whereas the volume obtained with the open biopsy forceps method differed significantly from the actual volume, consistently underestimating the actual size. The aberration ratios (percentage deviation between the measured and true volume, expressed as mean +/- SD) obtained with the stereoscopic endoscope were superior (9.2% +/- 9.5%) to those obtained with the open biopsy forceps method (-34.0% +/- 26.8%). These preliminary in vitro results with the stereoscope show considerable promise for the simple and precise three-dimensional measurement of gastrointestinal lesions and warrant human clinical trials.