112 research outputs found
Rodenacker, Wolf Georg
No full textProf. Dr.-Ing. Wolf Georg Rodenacker, der 1965 auf den neu gegründeten Lehrstuhl für Konstruktionstechnik an der damaligen TH München berufen wurde, war in der Bundesrepublik Deutschland Pionier der strikten Methodiker und damit einer der Urheber für die raschen Entwicklungen in der Konstruktionsmethodik seit den späten 1960er Jahren
Intensity Segmentation of the Human Brain with Tissue dependent Homogenization
Get PDFHigh-precision segmentation of the human cerebral cortex based on T1-weighted MRI is still a challenging task. When opting to use an intensity based approach, careful data processing is mandatory to overcome inaccuracies. They are caused by noise, partial volume effects and systematic signal intensity variations imposed by limited homogeneity of the acquisition hardware. We propose an intensity segmentation which is free from any shape prior. It uses for the first time alternatively grey (GM) or white matter (WM) based homogenization. This new tissue dependency was introduced as the analysis of 60 high resolution MRI datasets revealed appreciable differences in the axial bias field corrections, depending if they are based on GM or WM. Homogenization starts with axial bias correction, a spatially irregular distortion correction follows and finally a noise reduction is applied. The construction of the axial bias correction is based on partitions of a depth histogram. The irregular bias is modelled by Moody Darken radial basis functions. Noise is eliminated by nonlinear edge preserving and homogenizing filters. A critical point is the estimation of the training set for the irregular bias correction in the GM approach. Because of intensity edges between CSF (cerebro spinal fluid surrounding the brain and within the ventricles), GM and WM this estimate shows an acceptable stability. By this supervised approach a high flexibility and precision for the segmentation of normal and pathologic brains is gained. The precision of this approach is shown using the Montreal brain phantom. Real data applications exemplify the advantage of the GM based approach, compared to the usual WM homogenization, allowing improved cortex segmentation
Does digital analysis of micro image data improve understanding of reality? Contradictions-Challenges.
No full textUnderstanding of reality means among many others the ability to recognize, to predict reliably behaviours and properties of certain entities, and to describe. Besides verbal, often metaphorical descriptions, models are frequently used to formalize this understanding. In science the validity of models (hypotheses) has to be proven by experiments. Model parameters like start values, constraints and boundary conditions are often extracted from image data. Qualitative terms like shape, surface, structure (density, texture) and arrangement (spatial relationship) are explored and their possible measurements are outlined. They are also related to underlying experimental questions and intuitive understanding. Particular emphasis is given to properties without a commonly accepted quantitative counter part or which pose difficulties in perception and discrimination. Image analysis in methodologies and results from eco- and geobiology are presented and discussed. Namely, measurements of bacteria in biofilm and in the rhizosphere, characterization of biofilm growth, bacterial impact on surfaces, and automated phytoplankton analysis are outlined and iconographically related. (c) 2007 Elsevier B.V. All rights reserved
Semi-automated statistical quantification of initial colonization of bacteria on different materials under standardized conditions
No full textThe formation of biofilms on different materials provokes high costs in industrial processes, as well as in medical applications. Therefore, the interest in development of new materials with improved surfaces to reduce bacterial colonization rises. In order to evaluate the quality and safety of these new materials, it is highly important to ensure world-wide comparable tests that are relying on statistical evidence. The only way to reach this statistical safety is through a high-throughput Screening under standardized test conditions.
We developed a flow through system for cultivation of biofilm-forming bacteria under controlled conditions with a total capacity for testing up to 32 samples in parallel. Quantification of the surface colonization was done by staining the bacterial cells with a fluorescence marker, followed by epifluorescence microscopy. More than 100 images of each sample were automatically taken and the surface coverage was estimated with the free open source software gmic (http://gmic.eu), followed by a precise statistical evaluation. Overview images of all gathered pictures of the whole material coupon were generated to illuminate the colonization characteristics of the selected bacteria on certain materials.
With this method, differences in bacterial colonization on different materials can be quantified in a statistically validated manner. The innovative and solid test procedure will support the design of improved materials for medical and industrial applications such as implants, ship hulls, pipelines, heat exchangers, aquaculture equipments, photovoltaic-panels and fundaments of wind power plants
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