Virtual Endoscopy System Based On Surface Rendering

Virtual Endoscopy is a unique technique which gradually forms by the development of Computer Graphics, Image Processing, Medical Visualization, Virtual Reality, etc. It is a completely untouched diagnoses method and avoids the risk of invading body when the actual endoscopy is used.In this thesis, the origin, principle, excellence, development and application of Virtual endoscopy are completely surveyed. The technical modules are also introduced. Based on these, several key techniques existing in virtual endoscopy system are studied in the thesis work.Marching Cubes is a classical algorithm about 3D surface reconstruction. In this thesis, the principle and process of Marching Cubes are described in detail. Extended Marching Cubes algorithm is used to solve the ambiguity problem. To improve the algorithm's efficiency, this thesis presents an optimised method using a look-up table on basis of region growing. As 3D surface model reconstructed with Marching Cubes algorithm contains huge number of triangles, it is quite difficult to render them in real time. So, a mesh simplification algorithm based on vertices deleting has been used in the thesis. Running examples show that the model still maintains the feature of the original, even significant number of triangles has been reduced.In path planning, this thesis studies the Topological Thinning algorithm and proposes a fast algorithm using a look-up table based on min-heap and region growing. In order to maintain the continuity when flying through, this thesis uses a cardinal cubic spline curve to smooth the center path.In navigation, a virtual camera is defined to simulate the actual endoscopy. Manual navigation, automatic navigation and guided navigation are realized in this thesis. In order to simulate the restriction of the actual endoscopy in medical diagnoses, this thesis proposes a simple, fast and efficient surface collision detecting algorithm using the distance values from voxel points to apparatus's surface which are obtained during path planning.