MSc Assignment

Modelling and Performance Analysis of Flexible Surgical Instrument and its Validation

1. Introduction

Surgical robotics is one of the fast emerging areas in healthcare and medical science. The da Vinci surgical system (Figure.1) is one of the most successful and commercialized surgical systems used for robotic-assisted minimally invasive surgery.

The focus is now on scarless surgery. Natural Orifice Transluminal Endoscopic Surgery (NOTES) involves passing surgical instruments, a tiny camera, through a natural orifice of the body to the desired organ (Figure.2). By avoiding major incisions through the skin, muscle, and nerves of the abdomen, for instance, patients may experience a quicker recovery with less pain and scarring while reducing the risk of post operative hernias.

TeleFLEX project is one of the initiatives from University of Twente to achieve that goal. The objective of this project is to design and develop tele-manipulation system with intuitive control for endo-/transluminal endoscopic surgery based on master-slave approach. The slave side includes an endoscope/ endoscopic platform, which provides access channels for the flexible surgical instruments and other accessories required for the particular intervention. Figure.3 shows a typical endoscope with instruments.

2. Problem Definition

Typical endoscopic interventions are biopsy, polypectomy, mucosectomy, etc. These procedures are carried out manually by the surgeons and the assistants. As the endoscopic procedures are becoming more therapeutic than diagnostic, the surgical instrument requires complex manipulations. Unlike conventional endoscopic interventions, it requires motion and force inputs. The instrument tip may need to deliver certain amount of force or to orientate in particular way. The actuators and sensors are placed outside the body. The motion/force fidelity of the instrument is of paramount importance as it is critical for the overall performance of the master-slave system. The mechanical properties, like the rotational and bending stiffness, coupled with the friction between the surfaces are the governing parameters. Modelling and simulation of the flexible instrument can provide us the essential design parameters which are necessary for predictable input/output relationship for the instrument. It also provides the design specifications for the future instrument developments required for such interventions.

Therefore, the main objective of the master assignment is:

§to model the flexible instrument using SPACAR,

§to carry out the performance analysis for different mechanical properties of the instrument and friction properties of the surfaces,

§to design and fabricate the experimental set-up,

§to validate the results

3. Methodology

Firstly, SPACAR model will be developed for the flexible instrument using 3D beam elements with varying mechanical properties, like bending stiffness, rotational stiffness, damping, etc. Simulation will be carried out for the insertion, rotation, or for combinations of motion in undeformable constrained space with different friction and contact parameters. The design parameters will be optimized for performance in terms of motion/force delivery at the tip.

Subsequently, an experimental set-up will be designed and fabricated to validate the simulation results. Experiments can be performed with different kinds of flexible cables or shafts together with different kinds of tubes with variable frictional properties.

In summary, the research plan would be as follows:

§Build SPACAR model for the flexible instrument

§Define appropriate contact model

§Simulate under different contact conditions

§Design of experimental set-up and fabrication

§Experimental validation

§Writing Master thesis, journal papers, etc.



2.NOTES white paper, February 2006,

3.Tele-manipulation System with Intuitive Control for Transluminal Endoscopic Surgery,