Evaluation of the tip-bending response in clinically used endoscopes.
OBJECTIVE
Endoscopic interventions require accurate and precise control of the endoscope tip. The endoscope tip response depends on a cable pulling system, which is known to deliver a significantly nonlinear response that eventually reduces control. It is unknown whether the current technique of endoscope tip control is adequate for a future of high precision procedures, steerable accessories, and add-on robotics. The aim of this study was to determine the status of the tip response of endoscopes used in clinical practice.


METHODS
We evaluated 20 flexible colonoscopes and five gastroscopes, used in the endoscopy departments of a Dutch university hospital and two Dutch teaching hospitals, in a bench top setup. First, maximal tip bending was determined manually. Next, the endoscope navigation wheels were rotated individually in a motor setup. Tip angulation was recorded with a USB camera. Cable slackness was derived from the resulting hysteresis plot.


RESULTS
Only two of the 20 colonoscopes (10 %) and none of the five gastroscopes reached the maximal tip angulation specified by the manufacturer. Four colonoscopes (20 %) and none of the gastroscopes demonstrated the recommended cable tension. Eight colonoscopes (40 %) had undergone a maintenance check 1 month before the measurements were made. The tip responses of these eight colonoscopies did not differ significantly from the tip responses of the other colonoscopes.


CONCLUSIONS
This study suggests that the majority of clinically used endoscopes are not optimally tuned to reach maximal bending angles and demonstrate adequate tip responses. We suggest a brief check before procedures to predict difficulties with bending angles and tip responses.
Department of Robotics and Mechatronics, University of Twente, Enschede, the Netherlands.
Esther D
ED
Rozeboom
DEMCON Advanced Mechatronics, Enschede, the Netherlands.
Rob
R
Reilink
Department of Gastroenterology and Hepatology, Meander Medical Center, Amersfoort, the Netherlands.
Matthijs P
MP
Schwartz
Department of Gastroenterology and Hepatology, Academic Medical Centre, University of Amsterdam, Amsterdam, the Netherlands.
Paul
P
Fockens
Department of Robotics and Mechatronics, University of Twente, Enschede, the Netherlands; Department of Surgery, Meander Medical Center, Amersfoort, the Netherlands.
Ivo A M J
IA
Broeders