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Biomedical subjects

B Pflesser

Publications and source records attributed to B Pflesser.

8 recordsLinked to original sources
PubMed2001

Creating a high-resolution spatial/symbolic model of the inner organs based on the Visible Human.

Computerized three-dimensional models of the human body, based on the Visible Human Project of the National Library of Medicine, so far do not reflect the rich anatomical detail of the original cross-sectional images. In this paper, a spatial/symbolic model of the inner organs is developed, which is based on more than 1000 cryosections and congruent fresh and frozen CT images of the male Visible Human. The spatial description is created using color-space segmentation, graphic modeling, and a matched volume visualization with subvoxel resolution. It is linked to a symbolic knowledge base, providing an ontology of anatomical terms. With over 650 three-dimensional anatomical constituents, this model offers an unsurpassed photorealistic presentation and level of detail. A three-dimensional atlas of anatomy and radiology based on this model is available as a PC-based program.

Anatomy, Cross-Sectional↗
PubMed2001

[Stereoscopic simulation of ear surgery intervention with a novel 3D computer models].

INTRODUCTION: The presentation of the surgical anatomy of the temporal bone by standard anatomical figures is not suitable for otosurgical training. For the comprehension of its complex morphology temporal bone drilling is inalienable. Aim of the present cooperation was to gain an interactive real-3D program for the simulation of specific laterobasal surgical approaches. METHODS: The program was derived from a standard horizontal section of a human temporal bone using a Siemens Somatom Plus 4 Tomograph. The slice thickness was 1 mm, the image matrix was 512. The Voxel-Man-system was used to built up the application for unix workstations. RESULTS: Each step of a surgical approach to the temporal bone can be performed by the present computer model. Calculation in a stereo mode even allows spatial 3D-perception when using red/green glasses. CONCLUSIONS: This program is a novel tool to simulate critical aspects of otosurgical procedures on a computer. Up to now the lack of tactile and kinesthetic information does not allow to renounce individual temporal bone drilling.

Computer Simulation↗
PubMed2001

A realistic model of human structure from the visible human data.

The computer-based 3D models of the human body reported to date suffer from poor spatial resolution. The Visible Human project has delivered high resolution cross-sectional images that are suited for generation of high-quality models. Yet none of the 3D models described to date reflect the quality of the original images. We present a method of segmentation and visualization which provides a new quality of realism and detail. Using the example of a 3D model of the inner organs, we demonstrate that such models, especially when combined with a knowledge base, open new possibilities for scientific, educational, and clinical work.

Anatomy, Cross-Sectional↗
PubMed2000

Planning and rehearsal of surgical interventions in the volume model.

Visualization of 3D medical data is routinely used in a wide range of applications. However, for the planning and rehearsal of surgical interventions more sophisticated techniques for interaction have to be developed. The realistic specification and visualization of free form cuts is needed to allow the 'look and feel' close to a real dissection. The problem here is, since these cuts are not represented by intensity changes, that the gray-level-gradient-method can not be used for the estimation of surface normals. In addition, the interactive repositioning of dissected fragments has to be simulated. We have developed an extended ray-casting algorithm for visualization of object motion in the volume model. We implemented new methods for the representation, modeling and high quality rendering (subvoxel resolution) of arbitrarily shaped cut regions within the volume model. The representation is done using a dynamic data structure. This way, all operations can easily be reversed and the original object information is preserved. The modeling of cut surfaces is done in an independent data volume where the partial-volume-effect, which is the prerequisite for the gray-level-gradient method, is calculated as it would be generated by an imaging system. This way, the localization of cut surfaces at subvoxel resolution and an accurate estimation of the surface normals is achieved. The key point here is to detect if a cut surface really truncates an object or if the object has not been affected by a cutting operation. We will present an new method, called adaptive sampling which allows to determine the situation by the generation of additional sample points (when necessary) during the ray casting process. The described techniques provides the basis for simulation of surgical interventions in the voxel-model which could not be achieved with any surface-based method. We present a system for simulation and rehearsal of otosurgical approaches, where we implemented a drill-like tool with which the student lays off the route to the operating area. The key point is to not injure structures of risk such as the facial nerve. For applications like the simulation of craniofacial surgery we developed a gradual cutting tool ("virtual scalpel").

Computer Graphics↗
PubMed1999

Interactive volume visualization using "intelligent movies".

High quality visualization of medical volume models as performed by the VOXEL-MAN and similar systems is still too time consuming and the interaction complicated when sophisticated tools like dissection are used. We hence developed a new paradigm allowing to create simpler derivatives of the model, called "intelligent movies". These are in QuickTime or QuickTime VR format which allow interactive exploration with two degrees of freedom. As a decisive novelty, we extended it by a pixelwise link to the knowledge base which may be queried in the image context. Thus scenes emphasizing a selected aspect of the volume model may be created as intelligent movies, which a user (referring physician, student) can explore largely with the functionality of VOXEL-MAN, but in real time--on any standard PC--and also via a JAVA applet within web browsers. This is shown with the example of 3D interactive anatomical atlases and clinical cases.

Anatomy, Cross-Sectional↗
PubMedDate not supplied

Exploring the Visible Human using the VOXEL-MAN framework.

In principle the Visible Human data sets are an ideal basis for building electronic atlases. While it is easy to construct such atlases by just offering the possibility of browsing through the 2D slices, constructing realistic 3D models is a huge project. As one rather easy way to establish 3D use, we have registered the Visible Human data to the already existing 3D atlas VOXEL-MAN/brain. This procedure enables one to lookup anatomical detail in an atlas based on radiological images. Concerning the segmentation problem, which is the prerequisite for a real 3D atlas, we have developed an interactive classification method that delivers realistic perspective views of the Visible Human. As these volume based methods require high-end workstations, we finally have developed a multimedia program that runs on standard PCs and uses Quicktime VR movies.

Anatomy, Cross-Sectional↗