Modeling of the Lap-Band® for Laparoscopic Adjustable Gastric Banding Operation

This paper presents a physics-based model of the Lap-bandreg (Inamed Health) system for simulation of laparoscopic gastric banding (LAGB) operation. The Lap-bandreg has different mechanical properties along the centerline due to different thickness and curvature which makes the task of simulating its dynamics in a stable manner within a multimodal virtual environment rather challenging. A hybrid modeling technique is adopted with a mass-spring model being used for the less stiff portion and a quasi-static articulated rigid link model for the stiffer and relatively more inextensible portion. To allow the trainee for interactive bimanual manipulation of the Lap-bandreg with two graspers, we propose an efficient method to compute exact constraint forces based on velocity constraint in the quasi- static articulated rigid link systems. The performance of the proposed method is compared with the penalty force approach. The virtual Lap-bandreg model has been implemented into a complete graphics-haptics-physics-based system with two PHANToM Omni devices (from Sensible Technologies) being used for real-time bimanual interaction with force feedback.