With the development of Medical Imaging techniques together with Virtual Reality and Computer Graphics, computer-aided diagnosis is attracting more and more attention. Hence Virtual Endoscopy techniques were produced. While endoscopy is a normal clinical examination method, Virtual Endoscopy is a good simulation to the real endoscopy based on techniques such as graphics, and on medical imaging techniques. Compared with real endoscopy, VE exainination is less time-consuming, cheaper and not invasive, which can greatly reduce the risk of examination. In some applications it can replace the real endoscopy. Virtual Endoscopy System can be divided into two categories based on the adopted rendering techniques: Volume Rendering and Surface Rendering. Volume rendering method can give a high resolution, but the computing time is very long with ordinary hardware. We constructed a Virtual Bronchus Endoscopy System based on Surface Rendering. The advantage of Surface Rendering is that it can be real-time navigated on a PC. In the meantime, important details are preserved. This system can be divided into the following parts: Data Retrieval, Segmentation of Bronchus, Surface Reconstruction, Real-time Rendering, and Camera Control. The work in this article includes: 1. In segmentation, a 3D Scanline-Filling Region Growing Algorithm based on auto-adapted threshold is presented. The segmentation result is pretty good. 2. The surface of bronchus is reconstructed with Marching Cubes algorithm. Mesh Simplification algorithm is adopted to meet the need of real-time navigation.3. In rendering, techniques such as Gouraud shading model and Z-buffer are adopted, and the results are displayed with pseudo-color by RGB-HSI transform. 4. In navigation, a simplified approximate Median Axis extraction algorithm is presented. The camera (View Point) is restricted on the median axis. The camera has for freedom degree: moving forward and backward, turning upward and downward, turning leftward and rightward, zooming in and out. These four freedom degrees can simulate the movement of camera perfectly.
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