Spatial awareness in Natural Orifice Transluminal Endoscopic Surgery (NOTES) navigation

Abstract

Objective: To characterise navigational patterns in the abdominal cavity associated with different spatial awareness status of the operator during navigation of Natural Orifice Transluminal Endoscopic Surgery (NOTES). It is hypothesised that poor spatial awareness will manifest as erratic navigational patterns and poor performance.

Subjects and methods: Ten endoscopic novices navigated a defined course in a NOTES phantom (NOSsE) simulating the path of peritoneoscopic examination. Subjects performed the task three times without and once with an additional laparoscopic camera. Electromagnetic tracking was used to trace the tip of the endoscope during the navigation. Metrics of performance included the number of correctly visualised course targets, between targets localisation time and path length, and total completion time. Spatial awareness was explored by means of topological modelling of the navigation trace. Spatial navigation maps were generated from the tip trace footprint, differentiated using the Earth Movers Distance (EMD) and captured in a two dimensional chart where proximity in the projected space reflects similarity of navigation behaviour. Groups were identified displaying idiosyncratic target to target transitions in endoscopic navigation behaviour.

Results: No significant differences were found between four sessions in terms of the path length. Time was statistically improved when using supplemental visualisation (p<0.05). Four awareness groups were identified based on the subjects exhibited navigation footprint over the frontal plane, namely: (1) consistent navigation and performance; (2) inconsistent navigation and performance; (3) improvements in navigation and performance despite undifferentiated behavioural signatures; and (4) inconsistent navigation with improvements in performance.

Conclusions: Tracking the tip of the endoscope permits reconstruction of the navigation path during extraluminal navigation. The spatial location of the tip of the endoscope during navigation was used to unveil the operator's spatial awareness. Navigation routes in this study have been projected onto a 2D scene, related to performance and classified according to exhibited spatial awareness. Our assessment of this relationship suggests that poor spatial awareness is accompanied by erratic manoeuvres, often leading to poor performances, and vice versa. Tracking the location of the tip of the endoscope is an important issue in NOTES, and similarly understanding the spatial awareness of the operator is crucial in terms of the safety in NOTES. This work may have significant implications for training and assessment of new NOTES or minimally invasive surgeons. It may also lead to the new designs of endoscopes for NOTES.