Virtual dental surgery as a new educational tool in dental school.

PURPOSE: The virtual environment of the Voxel-Man simulator that was originally designed for virtual surgical procedures of the middle ear has been adapted to intraoral procedures. To assess application of the simulator to dentistry, virtual apicectomies were chosen as the pilot-test model. METHODS: A group of 53 dental students provided their impressions after virtual simulation of apicectomies in the Voxel-Man simulator. RESULTS: Fifty-one of the 53 students recommended the virtual simulation as an additional modality in dental education. The students indicated that the force feedback (e.g. simulation of haptic pressure), spatial 3D perception, and image resolution of the simulator were sufficient for virtual training of dental surgical procedures. CONCLUSION: The feedback from dental students involved in this pilot-test has encouraged our interdisciplinary group to continue further development of the simulator with the goal of creating new training strategies in dental and medical education.

Virtual reality: a new paranasal sinus surgery simulator.

OBJECTIVES/HYPOTHESIS: Virtual surgical training systems are of growing value. Current prototypes for endonasal sinus surgery simulation are very expensive or lack running stability. No reliable system is available to a notable number of users yet. The purpose of this work was to develop a dependable simulator running on standard PC hardware including a detailed anatomic model, realistic tools and handling, stereoscopic view, and force feedback. STUDY DESIGN: Descriptive. METHODS: A three-dimensional voxel model was created based on a high-resolution computed tomography study of a human skull, from which the bony structures were segmented. The mucosa and organs at risk were added manually. The model may be manipulated with virtual surgical tools controlled with a low-cost haptic device, which is also used to adjust microscopic or endoscopic views. Visualization, haptic rendering, and tissue removal are represented with subvoxel resolution. RESULTS: The handling of the model is convincing. The haptic device provides a realistic feeling regarding the interaction between tool tip and anatomy. Three-dimensional orientation and the look and feel of virtual surgical interventions get close to reality. CONCLUSIONS: The newly developed system is a stable, fully operational simulator for sinus surgery based on standard PC hardware. Besides the limitations of a low-cost haptic device, the presented system is highly realistic regarding anatomy, visualization, manipulation, and the appearance of the tools. It is mainly intended for gaining surgical anatomy knowledge and for training navigation in a complex anatomical environment. Learning effects, including motor skills, have yet to be quantified.

Three-dimensional atlas of lymph node topography based on the visible human data set.

Comprehensive atlases of lymph node topography are necessary tools to provide a detailed description of the lymphatic distribution in relation to other organs and structures. Despite the recent developments of atlases and guidelines focusing on definitions of lymphatic regions, a comprehensive and detailed description of the three-dimensional (3D) nodal distribution is lacking. This article describes a new 3D atlas of lymph node topography based on the digital images of the Visible Human Male Anatomical (VHMA) data set. About 1,200 lymph nodes were localized in the data set and their distribution was compared with data from current cross-sectional lymphatic atlases. The identified nodes were delineated and then labeled with different colors that corresponded to their anatomical locations. A series of 2D illustrations, showing discrete locations, description, and distribution of major lymph nodes, was compiled to form a cross-sectional atlas. The resultant contours of all localized nodes in the VHMA data set were superimposed to develop a volumetric model. A 3D reconstruction was generated for the lymph nodes and surrounding structures. The volumetric lymph node topography was also integrated into the existing VOXEL-MAN digital atlas to obtain an interactive and photo-realistic visualization of the lymph nodes showing their proximity to blood vessels and surrounding organs. The lymph node topography forms part of our whole body atlas database, which includes organs, definitions, and parameters that are related to radiation therapy. The lymph node topography atlas could be utilized for visualization and exploration of the 3D lymphatic distribution to assist in defining the target volume for treatment based on the lymphatic spread surrounding the primary tumor.

Computer-based anatomy a prerequisite for computer-assisted radiology and surgery.

RATIONALE AND OBJECTIVES: The aim of the study is to show the possibilities opened up by three-dimensional (3D) computer-based models of the human body for education in anatomy, training of radiological and endoscopic examinations, and simulation of surgical procedures. MATERIALS AND METHODS: Based on 3D data sets obtained from the Visible Human and/or clinical cases, virtual body models are created that provide an integrated spatial and symbolic description of the anatomy by using interactive color/intensity-based segmentation, ray casting visualization with subvoxel resolution, a semantic network for knowledge modeling, and augmented QuickTime VR (Apple Computer, Inc, Cupertino, CA) movies for presentation. RESULTS: From these models, various radiological, endoscopic, or haptic manifestations of the body can be derived. This is shown with examples from anatomy teaching, correlation of x-ray images with 3D anatomy for education in radiology, gastrointestinal endoscopy, correlation of ultrasound images with 3D anatomy in endoscopic ultrasonography, and simulation of drilling in temporal bone surgery. CONCLUSION: The presented models provide a means for realistic training in interpretation of radiological and endoscopic images of the human body. Furthermore, certain surgical procedures may be simulated realistically. Used as a complement to the current curriculum, these models have the potential to greatly decrease education times and costs.

Interactive Segmentation of Muscles and 3D Representation of Meridians Based on Visible Human.

Based on VOXEL-MAN software and our previous work on merging acupoint information with the dataset of the male Visible Human, we have refined the segmentation method for muscles and visualized the anatomical structure of meridians. In interactive segmentation, we obtain additional information on connectivity and texture. We also apply surface fitting to track muscle contours on data slices where the threshold segmentation method is hard or impossible to apply. With these processes, the original segmentation method, mainly via threshold, is improved to deal with more complex situations. We also constructed meridians, which are supposed to be composed by groups of acupoints. For that we used the location of these acupoints and interpolation methods.

Segmentation of muscles for 3D representation of acupoints.

Based on the dataset of the male Visible Human and the VOXEL-MAN software, original work for 3D representation of acupoints and acupuncture treatment has been reported. To get a realistic model, segmentation is one of the most important procedures in the whole process. The interactive segmentation of objects on the basis of ellipsoidal regions in RGB-space greatly enhances the realism of 3D reconstructions of the Visible Human datasets. Furthermore, this article describes a double-ellipsoids method in RGB-space for the specific segmentation of muscles originally from our mass of work. The whole process can be interactively controlled by an operator via the tools developed by VOXEL-MAN. Some ideal results have been achieved in a short time.

Volume cutting for virtual petrous bone surgery.

A profound knowledge of anatomy and surgical landmarks of the temporal bone is a basic necessity for any otologic surgeon. Because this knowledge, so far, has been mostly taught by limited temporal bone drilling courses, our objective was to create a system for virtual petrous bone surgery that allows the realistic simulation of specific laterobasal surgical approaches. A major requirement was the development of an interactive drill-like tool, together with a new technique for realistic visualization of simulated cut surfaces. The system is based on a volumetric, high-resolution model of the temporal bone, derived from CT. Interactive volume cutting methods using a new multivolume scheme have been developed. In this scheme, cut regions are modeled independently in additional data volumes using voxelization techniques. The voxelization is adapted to successive cutting operations as needed for the simulation of a drill-like tool. A new visualization technique was developed for artifact-free rendering of sharp edges, as formed by the intersection of a cut and an object surface. The new multivolume visualization technique allows high-quality visualization of interactively generated cut surfaces. This is a necessity for a realistic simulation of petrous bone surgery. Our system therefore facilitates comprehension of the complex morphology, and enables the recognition of surgical landmarks, which is most important if injury to delicate organs (e.g., the facial nerve or auditory ossicles) is to be avoided. The system for virtual petrous bone surgery allows the simulation of specific surgical approaches with high-quality visualization. The user can learn about the complex three-dimensional anatomy of the temporal bone from the viewpoint of a real otosurgical procedure.

Virtual endoscopy using spherical QuickTime-VR panorama views.

Virtual endoscopy needs some precomputation of the data (segmentation, path finding) before the diagnostic process can take place. We propose a method that precomputes multinode spherical panorama movies using Quick-Time VR. This technique allows almost the same navigation and visualization capabilities as a real endoscopic procedure, a significant reduction of interaction input is achieved and the movie represents a document of the procedure.