Model of cutting and deformation by electrical instruments for ERCP (endoscopic retrograde cholangiopancreatography) simulation

Abstract

Sphincterotomy is a surgical procedure in Endoscopic Retrograde Cholangiopancreatography (ERCP). Doctors use an electrical device called sphincterotome to cut and enlarge major papilla of duodenum for cannulation (insertion of catheter into the bile duct) in this procedure. Sphincterotomy is challenging, therefore, it requires many practices from doctor before he performs in real ERCP. Previous research shows that to achieve 90% success rate, doctors must perform at least 200 ERCP procedures. This thesis studies a computer-based simulation of sphincterotomy for training purpose. The major goal of the thesis is to develop a simulation of electrical cutting on the soft tissue model. The method must overcome the problem of performance, which cannot be achieved by previous research while maintaining the non-penetration surfaces between objects. The objectives of the thesis are:o Develop deformable models of sphincterotome and major papilla of duodenumo Develop contact model between these two deformable objectso Develop cutting algorithm for simulation of cutting major papilla of duodenumFor deformable objects, we utilize meshfree methods to model major papilla of duodenum and develop a mass-spring system for model of sphincterotome. For contact problem, this thesis proposes a hybrid collision response model that divides contact cases into visible and invisible contacts. Signorini’s contact model is employed for visible contacts, and a centerline based model was developed for invisible contacts. The proposed contact model reduces computation time of collision response up to 80%, in compare to conventional methods. For cutting problem, this thesis proposed a mesh generation algorithm for meshing the new cut surface. The proposed meshing-algorithm is simpler and more stable than previous cutting method. The thesis also proposes new method for intersect test in cutting component. The proposed algorithm performs the test in original coordinate of the deformable model ...