Autonomous Local Navigation of Spring-Based Continuum Choledochoscopes for Cholecystolithotomy

Choledochoscopy, a natural orifice transluminal endoscopic surgery, represents an alternative to cholecystolithotomy in comparison to cholecystectomy and open gallbladder-preserving surgery. To reduce surgeon fatigue and increase surgical autonomy, this paper presents an autonomous local navigation (ALN) system for cholecystolithotomy, comprising a novel spring-based choledochoscope (CDS) with a monocular camera, a dataset-independent dynamic adaptive threshold segmentation (DATS) algorithm, and an ALN strategy. During navigation, the DATS detects bile duct bifurcations from the CDS view, selecting the target bifurcation based on bile duct anatomy with a wall-following mechanism. The CDS control method including bending and rotation control is then proposed based on the relationship between the position and direction of the bile duct center and the CDS characteristics. To ensure precise navigation, a closed-loop ALN strategy utilizing three interchangeable proportional controllers is developed, with task-specific proportionality factors. The efficacy of the DATS and CDS is validated through series experiments. Finally, both rigid and soft phantom experiments demonstrate the potential of the ALN system for cholecystolithotomy.