The Study Of Volume Rendering Techniques For Medical Data Visualization

In the past two decades, the field of medical visualization has seen unprecedented growth in computational and acquisition technologies. It is widely used in diagnostic, surgery planning and simulating, plastic and artificial limb surgery, radiotherapy planning, and teaching in anatomy.Direct Volume Rendering is one of the most important techniques for visualizing medical volume data. Its application in medical 3D reconstruction is becoming more and more important. In this paper, key techniques for Direct Volume Rendering are studied.In chapter 2 of this thesis we present a family of volume rendering algorithms that are very popular in recent years .We also discussed advantages and disadvantages of these algorithms at the end of the chapter.Ray casting method is one of the most important direct volume rendering algorithms. In chapter 3, we will introduce this method and list some of its acceleration techniques. Then we present a new acceleration algorithm for ray casting to compensate for the shortcomings of current methods.The currently dominant techniques for displaying surfaces for volume data consist of applying a surface detector to the sample array, fitting geometric primitives to the detected surfaces, and then rendering these primitives using conventional surface rendering algorithms. But this kind of algorithm often exhibit spurious surfaces. In chapter 4, we introduce how to use ray casting and splatting techniques to display surfaces of volume data. To reduce the rendering time, we also present two methods to realize this.An important task in volume rendering is the visualization of the regions of interest. But in most volume rendering applications, important regions are often occluded by other unimportant objects. This is typically accomplished using two methods: one method is using transfer functions to increase the opacity of the important region and reduce the opacity of other regions;another method is using pre-segmentation to segment the region of interest before volume rendering. But both of two methods can not solve the problem properly .In this paper, we propose a new method to overcome the problem of occlusion within the volume. Through this method, user can interactively select the occluding region to cut-away.