Role of Landmark for Spatial Mapping in Non-rigid Environments

Spatial orientation in colonoscopy is difficult. Previous studies have shown that knowledge of shape information is more useful than direction or location information. However, the mechanism of spatial mapping in a non-rigid environment is unknown. It was hypothesized that visual landmarks were used as the primary cue for spatial orientation, as in rigid environments, even when other conflicting cues were available. An experiment was conducted to examine the role of visual landmarks in spatial mapping in a non-rigid environment. Simulated colonoscopy procedures were performed in colon models representing a compressed colon and a colon with missing landmarks. Preliminary results indicated that time, and not visual landmarks, were used as the dominant cue for spatial mapping. This may explain the conflict experienced by endoscopists who are aware of the stretchable nature of the colon, combined with the unreliable landmarks. Therefore, a useful navigational aid might be developed to encourage the use of a different strategy for spatial mapping in situations where the spatial relationship between landmarks is not constant, as in the colon.