说明：  通过两个距离场的共同约柬来快速地提取出一条连接起点和终点的中心路径．同时为了保证褪游的效果．还采用3次B样条曲线对所获取的路径进行了光滑
(As compared with onion peeling algorithm and Dijkst ra’s Single Source Shortest Path Algorithm、the result shows that the algorithm not only cart get last speed and high quality result， but also has more flexibility．’l he application in Virtual endoscopy is also shown in the end of the paper．)