Research On The Key Techniques In Interactive Virtual Endoscopy System

Virtual Endoscopy is an application of virtual reality in modern medicine. It simulates optics endoscopy with medical images. Virtual Endoscopy incorporates Computer Graphics, Image Processing, Scientific Computing Visualization, and Virtual Reality, etc. Users can obtain the sense of immersion, realism, and real-time interaction, and change the status of the objects in the virtual environment. Virtual Endoscopy is a complete untouched medical diagnoses method and avoids the risks associated with actual optical endoscopy. The object of virtual endoscopy system research is to provide trusty means for medical examinations, and to spread the new application fields as assistant diagnoses, surgery planning and training. So, the research of Virtual Endoscopy has high value in clinical diagnosis.This thesis surveys the current status of virtual endoscopy system, outlines its structure and modules. Several key techniques which include visualization, centerline abstraction, navigation in virtual endoscopy system are studied and the system is clinically tested in the thesis work.The following work is based on the processed binary images which were provided by Computer Vision and Image Processing lab of University of Louisville. In this paper, surface rendering is used for automatic navigation display, volume rendering is used for interactive navigation display, nice results are achieved. Meanwhile, a medical image visualization system based VTK and MFC is developed, which provides an operating platform for virtual endoscopy.In the aspect of path planning, we summarize the methods to generate the central path in recent years. An automatic centerline extraction algorithm based on bidirectional voxel coding for colon and other single branch organs is proposed in this paper. The bidirectional source distance field is built by encoding the discrete voxel in three-dimensional data field. The begin-point and end-point of the centerline are abstracted automatically. We propose an interactive method to extract navigation path for trachea and other low curvature organs. The real-time navigation path is generated with the method which improves the speed obviously.In processing of navigation, two means are under consideration:manual interactive navigation and automatic navigation. Interactive navigation provides full freedom to doctors. They can reach anywhere they want to be and have a close look at it. Automatic navigation takes great advantage of the smoothed centerline. Let the virtual camera walk along the centerline controlling both the direction and the angle of the virtual camera. We research common navigation technique and propose an interactive fly-over navigation method which results in higher surface visibility coverage to examine intestine. Potential polyps hidden behind haustral folds can be found easily. By controlling the elevation of the camera, there are not blind corners any more, and the maximized visual surface area can be obtained. Finally, our virtual colonoscopy system is validated on abdominal image data including lesions. Colorectal polyps and other lesions are shown clearly.Future researches are pointed out considering the shortcomings and experiences of our system and the development trend.