Computational Analysis of Design Parameters for a Bimanual Concentric Push-Pull Robot

Colorectal cancer is a pervasive disease: an estimated 4.6% of men and 4.2% of women will suffer from it in their lifetime [1]. Precancerous polyps can be small (<5 mm) medium (6-9 mm) or large (>10 mm) [2]. Small polyps are most frequent, but polyps too large for immediate endoscopic removal during screening occur 135,000 times per year in the US alone [1]. There are two primary options for removing these polyps: endoscopic removal or partial colectomy. Endoscopic procedures, such as endoscopic submucosal dissection (ESD), are less invasive and reduce the risk of infection, reoccurence, and other adverse events [3]. Despite this, approximately 50,000 patients each year undergo partial colectomies for polyps which could have been removed endoscopically [4]. A primary obstacle to wider use of endoscopic pro- cedures is how challenging they are for physicans to perform, due to the limited dexterity of existing trans- endoscopic tools [5]. Currently tools come straight out the tip of the colonscope and moving them requires moving the tip of the colonoscope [6]. To enable tools to move independent of the colonoscope, we propose an endoscopically deployable, flexible robotic system, as shown in Fig. 1. This system deploys a flexible robotic arm through each channel of a standard 2-channel colonoscope. Each arm is composed of a setup sheath followed by a steerable sheath, with each sheath built using a concentric push-pull robot (CPPR) [7]. Each arm has a hollow central lumen through which tools (e.g. forceps, electrosurgery probes, etc.) can be passed. This design adds dexterity and provides the physician with two independent manipulators, with the goal of making ESD easier to perform.