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Biomedical subjects

Thomas Ertl

Publications and source records attributed to Thomas Ertl.

6 recordsLinked to original sources
PubMed2005

Reduced cytokine induction and removal of complement products with synthetic hemodialysis membranes.

The increasing use of high-flux membranes for hemodialysis (HD) has raised concerns that these membranes may confer a higher risk of exposure to cytokine-inducing, bacterial substances (CIS) in the dialysate. Several studies, however, reported higher transfer of CIS through low-flux cellulosic than high-flux synthetic membranes. This surprising paradox was explained by adsorption of CIS to certain high-flux membranes. In order to investigate flux and membrane type independently, we studied two synthetic Polyflux (PF) membranes of the same type but with different flux properties and compared them to a cellulosic membrane (Cuprophan). Three different approaches were employed: (1) cytokine induction in whole blood during in vitro HD contaminated with bacterial filtrates, (2) removal of recombinant C5a, and (3) transfer of purified lipopolysaccharide (LPS). After 90 min recirculation of whole blood, the appearance of IL-6-inducing substances on the blood side was lowest with high-flux PF (1.1 +/- 0.2 ng/ml), slightly higher with low-flux PF (1.9 +/- 0.7 ng/ml) and highest with Cuprophan (4.1 +/- 1 ng/ml). Recombinant C5a added to plasma on the blood side was markedly removed by high-flux PF (by 83%), to a lesser degree and only in the presence of ultrafiltration with low-flux PF (by 54%) and not significantly with Cuprophan (by 11%). Significant transfer of purified LPS from the dialysate onto the blood side was only observed with the cellulosic membrane. We conclude that in contrast to cellulosic membranes, certain synthetic membranes do not permit transfer of LPS. Cytokine induction on the blood side is further reduced by the use of high-flux membranes due to removal of activated complement factors.

Adsorption↗
PubMedDate not supplied

Visual signatures in video visualization.

Video visualization is a computation process that extracts meaningful information from original video data sets and conveys the extracted information to users in appropriate visual representations. This paper presents a broad treatment of the subject, following a typical research pipeline involving concept formulation, system development, a path-finding user study, and a field trial with real application data. In particular, we have conducted a fundamental study on the visualization of motion events in videos. We have, for the first time, deployed flow visualization techniques in video visualization. We have compared the effectiveness of different abstract visual representations of videos. We have conducted a user study to examine whether users are able to learn to recognize visual signatures of motions, and to assist in the evaluation of different visualization techniques. We have applied our understanding and the developed techniques to a set of application video clips. Our study has demonstrated that video visualization is both technically feasible and cost-effective. It has provided the first set of evidence confirming that ordinary users can be accustomed to the visual features depicted in video visualizations, and can learn to recognize visual signatures of a variety of motion events.

Algorithms↗
PubMedDate not supplied

Explanatory and illustrative visualization of special and general relativity.

This paper describes methods for explanatory and illustrative visualizations used to communicate aspects of Einstein's theories of special and general relativity, their geometric structure, and of the related fields of cosmology and astrophysics. Our illustrations target a general audience of laypersons interested in relativity. We discuss visualization strategies, motivated by physics education and the didactics of mathematics, and describe what kind of visualization methods have proven to be useful for different types of media, such as still images in popular science magazines, film contributions to TV shows, oral presentations, or interactive museum installations. Our primary approach is to adopt an egocentric point of view: The recipients of a visualization participate in a visually enriched thought experiment that allows them to experience or explore a relativistic scenario. In addition, we often combine egocentric visualizations with more abstract illustrations based on an outside view in order to provide several presentations of the same phenomenon. Although our visualization tools often build upon existing methods and implementations, the underlying techniques have been improved by several novel technical contributions like image-based special relativistic rendering on GPUs, special relativistic 4D ray tracing for accelerating scene objects, an extension of general relativistic ray tracing to manifolds described by multiple charts, GPU-based interactive visualization of gravitational light deflection, as well as planetary terrain rendering. The usefulness and effectiveness of our visualizations are demonstrated by reporting on experiences with, and feedback from, recipients of visualizations and collaborators.

Computer Graphics↗
PubMedDate not supplied

Standardized evaluation of CT angiography with remote generation of 3D video sequences for the detection of intracranial aneurysms.

Computed tomography (CT) angiography is a well-known imaging technique commonly applied to both the detection and therapy planning of intracranial aneurysms. For this purpose, current studies predominantly focus on three-dimensional (3D) representations of CT angiographic volumes obtained with varying visualization approaches on different computers. Interactive manipulation performed by users individually is an important prerequisite for data analysis. However, this leads to inconsistent and barely reproducible 3D visualization results. Furthermore, the quality of any 3D representation depends on the applied visualization strategy (eg, maximum-intensity projection, shaded-surface display, direct volume rendering). To overcome these limitations, the authors present a novel method for standardized visualization of CT angiographic volumes, consisting of three steps: (a) transfer of the image data to a remote high-end graphics workstation, (b) automatic 3D visualization with high-resolution direct volume rendering, and (c) consecutive video generation performed according to a standardized protocol. The recorded video sequences are transferred for evaluation to a local desktop computer. In the experimental setup, high-quality videos based on 3D visualizations were produced in less than 60 minutes per patient. Although aneurysms above the skull base are usually visualized with excellent quality, the analysis of aneurysms at the skull base is still difficult.

Angiography↗