A Research On Automatic Roaming Technology Of Virtual Endoscopy System Based On Volume Rendering

Virtual Endoscopy is a technology using computer graphics, virtual reality, imageprocessing and scientific visualization information to process simulation of opticalendoscopic technique for the diagnosis of patients, and it is the practical application ofvirtual reality technology in medical clinical diagnosis. Because the technology justprocesses medical CT or MRI tomographic images, and complete the examination anddiagnosis of the human body, so this technique is different from the conventional opticalendoscopic diagnosis pattern. It is a non-invasive means, which do not entity to be intrudedinto the physical body to be checked. Compared with conventional optical endoscope, thetechnology can avoid invasive treatment taking risk of pain and perforation to patients, andcan check tissues and organs that some physical entity can’t enter. This technology is morewidely used in the field of medical diagnostics scope. Besides, it can provide doctors withthe basis for the diagnosis in the treatment process, and play a supporting role for thedoctors in surgical planning and implementation of precise positioning.This paper focused on in-depth study of the four key technologies of theimplementation of virtual endoscope system: image segmentation,3D reconstruction, thecentral path extraction and virtual roam. In the image segmentation process, a regiongrowing algorithm for image segmentation was realized, and the human colon data wasaccurately and efficiently extracted from the original medical image which was the dataportion of the entire paper. In the3D reconstruction, this paper introduced the methods andprinciples of surface rendering and volume rendering, and it focused on the ray-castingvolume rendering algorithm and completes the3D reconstruction using this method in thepaper. In the process of extraction center path, this paper used the boundary distancetransform algorithm, in the implementation process need to establish boundary distancefield and source distance field from the field, through the joint action of the two fields tomake the extracted path have good centrality, have a maximum radial angle in roaming,and solve more difficult problem to extract the center of the curve path. Aimed at the low time efficiency of the algorithm in extracting the path, this paper put forward a methodthrough calculating voxel point ID value, increasing mark variables, setting up structuresarrays and using large arrays to establish ID values corresponding with the point’s locationin point set, and improved the time efficiency of the extraction path. In the virtual roam,the paper firstly introduced conversion among virtual endoscope system in the worldcoordinate system, the camera coordinate system and the image plane coordinate system indetail, and analyzed the settings of the origin, the focal length of the virtual camera indetail. Secondly, it focused on defects of the extracted path curvature and distance betweenpoints are relatively large, roaming jitter obvious, and uses Bezier curve algorithm tosmooth path. Finally, colon virtual roaming examination was performed using automaticroaming method.