A Novel Endoscope Design Using Spiral Technique for Robotic-Assisted Endoscopy Insertion Wei Li 1 , Ya-Yen Tsai 1 , Guang-Zhong Yang 2 , Fellow, IEEE and Benny Lo 1 , Senior Member, IEEE Abstract— Gastrointestinal (GI) endoscopy is a conventional and prevalent procedure used to diagnose and treat diseases in the digestive tract. This procedure requires inserting an off- the-shelf endoscope equipped with a camera and instruments inside a patient to the target of interest. To maneuver the endoscope, an endoscopist would rotate the knob at the handle to change the direction of the distal tip and apply the feeding force to advance the endoscope. However, due to the nature of the design, this often causes a looping problem during insertion making it difficult to be further advanced to the deeper section of the tract such as the transverse and ascending colon. To this end, in this paper, we proposed a novel robotic endoscope which is covered by a rotating screw-like sheath and uses a spiral insertion technique to generate ’pull’ forces at the distal tip of the endoscope to facilitate insertion. The whole shaft of the endoscope can be actively rotated, providing the crawling ability from the attached spiral sheath. With the redundant control on a spring-like continuum joint, the bending tip is capable of maintaining its orientation to assist endoscope navigation. To test for its functionality and feasibility to address the looping problem, we ran three experiments in total. The first two experiments were to analyse the kinematic of the device and test the ability of the device to hold its distal tip at different orientation angles during spiral insertion. In the third experiment, we inserted the device in the bent colon phantom to evaluate the effectiveness of the proposed design against looping when advancing through a curved section of a colon. Results show the moving ability using spiral technique and verify the potential of clinical feasibility. I. INTRODUCTION Gastrointestinal (GI) endoscopy is a common procedure to diagnose and treat diseases in the digestive tract. During the procedure, a long flexible endoscope is served for the purpose and is inserted through a natural pathway, such as oesophagus or colon to the target of interest. The integrated stereo camera and instrument channels can provide vision and access to surgical instruments to facilitate diagnosis and treatment procedures. Conventional flexible endoscopes often have limited for- ward progression ability and Depth of Maximum Insertion (DMI) because the endoscopes are inserted passively into the GI tract. Looping often occurs when the distal tip of the endoscope cannot pass beyond the colon region where there is a large curvature or folding. When this happens, the endo- scopist would apply counter pressure, move the patent’s body or even attempt for re-insertion. This may expose the patient to higher levels of anaesthesia due to longer procedure and 1 Wei Li, Ya-Yen Tsai and Benny Lo are with the Hamlyn Centre for Robotic Surgery, Imperial College London, SW7 2AZ, London, UK {wei.li16, y.tsai17, benny.lo}@imperial.ac.uk 2 Guang-Zhong Yang is with the Institute of Medical Robotics, Shanghai Jiao Tong University, Shanghai, P.R. China. gzyang@sjtu.edu.cn Fig. 1. Gastrointestinal endoscopy for disease diagnosis and treatment in digestive systems. cause discomfort, internal bleeding or even perforation to the patient. Recent research has indicated that colorectal cancer is ranked as the fourth of the most common cancers and the fifth in cancer-related deaths [1]. Due to its leading cause of morbidity and mortality, there is an increasing demand in the diagnosis of colorectal cancer which involves colon biopsies at deep colon locations such as ascending colon, cecum, etc. As such, in the last decades, these have fueled and driven the development of novel endoscopic devices with advanced manoeuvrability. Particularly, there has been a growing interest in developing snake-like or flexible robotic endoscopes whose shape can adapt to anatomical structures to avoid collisions to the inner colon wall and resolve looping problem [2], [3]. A variety of research and commercial robotic systems have been conducted on and developed for endoscopic interventions. The insertion mechanisms of those systems can be broadly divided into two main streams. One type of endoscopes is the snake-like robot composed of multiple segment structures and hence possesses multiple degrees of freedom (DOFs). Examples to such design include the i 2 Snake system [4] which used multiple tendon-driven artic- ulated joints for Ear-Nose-Throat surgery; the 5mm diameter customized resectoscope prototype which has three stacked continuum joints by Sarli et al. [5] for trans-urethral surgery; and the snake-like robot, which is based on variable neutral- line mechanism to continuously adjust the stiffness of the continuum joints by varying tensions, proposed by Kim et al. [6]. On the commercial side, the Flex R  Robotic System (Medrobotics, Raynham, MA, USA), translated from the HARP system [7], is featured with the design of multi-