Ein implantierbares Telemetriesystem zur Impedanzspektroskopie

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.Die kontinuierliche Überwachung des intrakorporalen Zustandes von Geweben beispielsweise zur Erkennung ischämischer Vorgänge nach gefäßchirurgischen Eingriffen oder im Rahmen der Rejektionsdiagnostik läßt sich durch bisher vorhandene Meßsysteme nur bedingt erreichen. Speziell die direkte Erfassung sensitiver Gewebeparameter über einen längeren Zeitraum ohne Belastung für den Patienten stellt in diesem Zusammenhang ein Problem dar. In der nachfolgenden Arbeit wird das Konzept eines implantierbaren Telemetriesystems vorgestellt, das die Bewertung des Gewebezustandes über die Messung der frequenzabhängigen Bioimpedanz ermöglicht. Besondere Beachtung wird der Auslegung und Umsetzung der einzelnen Systemkomponenten sowie der Vorstellung erster in vitro Messungen zur Evaluierung des Meßsystems geschenkt

Indirect Fourier transform in the context of statistical inference

Inferring structural information from the intensity of a small-angle scattering (SAS) experiment is an ill-posed inverse problem. Thus, the determination of a solution is in general non-trivial. In this work, the indirect Fourier transform (IFT), which determines the pair distance distribution function from the intensity and hence yields structural information, is discussed within two different statistical inference approaches, namely a frequentist one and a Bayesian one, in order to determine a solution objectively From the frequentist approach the cross-validation method is obtained as a good practical objective function for selecting an IFT solution. Moreover, modern machine learning methods are employed to suppress oscillatory behaviour of the solution, hence extracting only meaningful features of the solution. By comparing the results yielded by the different methods presented here, the reliability of the outcome can be improved and thus the approach should enable more reliable information to be deduced from SAS experiments.</jats:p

SASET A program for series analysis of small angle scattering data

This article presents a new program that allows highly automatized analyses of series of, especially, anisotropic two-dimensional neutron and X-ray small-angle scattering data as well as one-dimensional data series. The main aim of this work was to reduce the effort of the analysis of complex scattering systems, which remains an essential burden in the evaluation process of complex systems. The program is built in a modular manner to support a stepwise analysis of small-angle scattering data. For example, from a two-dimensional data series, features such as anisotropy or changes of the preferred scattering direction or intensities along the radial or azimuthal directions as well as along the series axis (e.g. time axis) can quickly be extracted. Different anisotropy measurement methods are available, which are described herein. In a second step, physical scattering models can be fitted to the extracted data. More complex models can be easily added. The fitting procedure can be applied with nearly every possible constraint and works automatically on whole scattering data series. Furthermore, simultaneous fitting can be used to analyze coupled series, and parallel working methods are implemented to speed up the code execution. Finally, results can be easily visualized. The name of the program isSASET, which is an acronym standing for small-angle scattering evaluation tool.SASETis based on MATLAB.</jats:p