Research On Volume Rendering And Its Application In Dental Clinic

Along with the development of the 3-Dimasional image technology, lots of 3D images have been generated, since then, how to deal with them, understand them and display them has become a huge and vibrant area of research. As one important branch of 3D visualization technologies, DVR (direct volume rendering) has been widely used among medical diagnosis and treatment, industrial equipment testing, space exploration, etc. The essential step of volume rendering is the transfer function design, it maps the original values of 3D volume dataset to optical properties, such as color and opacity, so as to extract and display the interested objectives and structures. However, since the complexity and uncertainty of the volume data, finding a universal and intuitive transfer function remains a challenging work.Traditional ways for volume rendering simulate the principle of human vision, using the plane rendering method, the rendering results are all viewing the objective from special angles, since the limitation of vision, only part of the whole objective can be viewed at a time. But in reality, we often meet the requirements of viewing the whole picture of the interested objectives, the needs for panoramic images. In this thesis, a method for generating dental panoramic radiographs from 3D CT sectional data is presented, which based on the physical demand of the dental clinic. In the method presented, we enroll the concept of curve surface rendering, with curve surface ray-casting volume rendering, we can generate the panoramic radiographs with CT sectional data. From the radiographs generated, we can view the global status of all the teeth in mouth, the structure overlap problem in the result generated by traditional volume rendering has been well solved.For the panoramic radiographs generation method, we need to set the rendering curve surface, which relies on the dental arch curve. In the thesis, the drawback of the existing method for dental arch curve fitting has been analysed, which based on the image corrosion theory, and a new way which based on drawing points manually and fit the dental arch curve with three order B-spline method was designed, it solves the problem of structure distortion caused by former method. The panoramic radiographs generated by volume rendering not only can achieve the effect of the images generated by the very panoramic machine, with proper transfer function, it can extract the interested regions and structures in dental clinic. In the thesis, the roots of teeth were extracted by the enhancement window. The location and size of jaw neural tube is very important in dental clinic, however, both in the images created by panoramic machine and by the method proposed in our thesis, the structure is very fuzzy. Since the complex composition of jaw neural tube, it's not possible to extract it by adjusting the parameters of the transfer function. By considering importing the spatial information to the process of transfer function design, and extract the jaw neural tube by obtaining the spatial constraint conditions of the tube firstly.In order to better assist diagnosis and treatment in dental clinic, a computer-assisted dental diagnosis system was designed and realized. The system adopts the modular design, it supplies functions that are useful for diagnosis with good user interface, such as virtual slice analysis, 3D reconstruction for the collected data, generation of panoramic radiographs, etc.