Medizinische Bildgebung. [Volume 7: Medical Imaging]. Ed. by Dössel, Olaf / Buzug, Thorsten M. Die bildgebenden Verfahren in der Medizin. Dössel, Olaf. Olaf Dössel. Prof. Dr. rer. nat. Olaf Dössel. Sprecher der kollegialen Bildgebende Verfahren in der Medizin II · Vorlesung. Lichttechnik-Hörsaal (LTI) External. – Buy Bildgebende Verfahren in der Medizin: Von der Technik zur medizinischen Anwendung book online at best prices in Olaf Dössel (Author).

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Computerized modeling of the human heart. Seemannand T. In Technisches Messenvol. Cardiologists measure electric signals inside the human heart aiming at a better diagnosis and optimized therapy of atrial arrhythmias like atrial flutter and atrial fibrillation.

The catheters that are used for this purpose are improving: The patterns of electric depolarization are sometimes very simple, comparable to plane waves. But in case of patients with severe atrial arrhythmias they can be quite complex: U-turns around a line of block, ectopic centres, break throughs, reentry circuits, rotors, fractionated signals and chaotic patterns are often observed. Methods of biosignal analysis can support the cardiologists in classifying the signals and extract information of high diagnostic relevance.

Computer models of the electrophysiology of the human heart can serve to design better algorithms for data analysis and to test algorithms, because the ground truth is known. Gildgebende Magnetic particle verfarhen MPI is a new imaging modality using oscillating magnetic fields in the frequency range of 10 kHz to kHz.

The duration of data acquisition becomes smaller, and signal-to-noise ratio improves if the amplitude of these fields is increased – technically amplitudes of up to mT might be feasible for human-sized systems. On the other hand, with bildgebendf field strength, adverse health effects must be expected: Thresholds for stimulation with bilxgebende fields in this frequency range are not precisely known, neither cssel the local temperature rise following exposure.

The ICNIRP guidelines define reference levels for magnetic field exposure for the general public that contain large safety factors – for medical ddr, they might be exceeded for a short time. In this article, research and guidelines in this field are briefly reviewed, and new results are presented in order to contribute to a future definition of safety limits for oscillating magnetic fields in MPI.

This review article gives a comprehensive survey of the progress made in computa- tional modeling of the human atria during the last 10 years. Modeling the anatomy has emerged from simple peanut-like structures to very detailed models including atrial wall and fiber di- rection.

Electrophysiological models started with just two cellular models in Today, five models exist considering e. On the pathological side, modeling atrial remodeling and fibrotic tissue are other important mexizin. The bridge to data that are measured in the catheter laboratory and on the body surface ECG is under construction. Every measurement can be used either for model personalization or for validation. Potential clinical applications are briefly outlined and future research perspectives are suggested.

The message of this article is that patient safety must be an essential part of thinking and planning in research for medical technology. Which aspects must verfahreh considered already in an early phase dsr any project are presented. The most important standards are listed briefly.

Band 7 Medizinische Bildgebung

Then the topics technical safety and electromagnetic compatibility EMCclinical evaluation, risk analysis, biological evaluation of materials, ergonomics, the special aspects of medical devices that include pharmacological components, and the requirements of software packages and implemented algorithms are discussed. Die wichtigsten Normen werden nur kurz angesprochen.

Cardiac arrhythmia is currently investigated from two different points of view. One considers ECG bio-signal analysis and investigates heart rate variability, baroreflex control, heart rate turbulence, alternans phenomena, etc.

The other involves building computer models of the heart based on ion channels, bio-domain models and forward calculations to finally reach ECG and body surface potential maps. Both approaches aim to support the cardiologist in better understanding of arrhythmia, improving diagnosis and reliable risk stratification, and optimizing therapy.


This article summarizes recent results and aims to trigger new research to bridge the different views. Computer models of the electrophysiological processes in the human heart become increasingly precise and detailed.

The dream of supporting diagnosis of arrhythmias and planning of therapeutic interventions comes into reach. Recent progress in the field of cellular models including e. Computer models of the heart can improve the understanding of the electrophysiological processes in healthy and diseased heart. They become more and more important for detailled diagnosis of arrhythmias and for optimization of therapy.

Models of myocardium cells known today are described – they are based on the properties of all relevant ion channels in the cell membrane. Then it is demonstrated, how many cells can be joined to form a cell patch and how finally the complete heart can be modelled. A simpler approach is using a so called cellular automaton that allows for a significant reduction of calculation time while sacrifying some accordance to reality. Adaptive cellular automatons allow for a fast simulation with acceptable accuracy.

Using them some results were gained for the simulation of typical arrhythmias, in the field of validation using an animal model and for therapy planning with RF-ablation. More than 20 years of research in imaging of bioelectric sources in the human heart have passed and a lot of effort has been devoted to the topic. In spite of that the method is not established in clinical practice but still just an interesting research topic of enthusiastic scientist.

A review together with a comprehensive literature survey is given in this article. Recent developments and new trends are outlined. A modular multichannel SQUID-system, in which every single channel can be optimized or replaced individually, is presented. A simplified way of coupling the modulation and feedback current directly to the coupling coil is realized The complete SQUID module including the superconducting shield was miniaturized down to a diameter of 5mm.

The cryogenic system was optimized with respect to low vibrations and low helium boil off rate. Simple conductive paint with precisely adjusted surface resistivity is used for RF-shielding. Biomagnetic measurements of the human heart and brain are presented. Single current dipole reconstructions and current density imaging techniques can be used to find the underlying sources.

Using a special coil positioning system an overlay of the functional current images with morphological MR-images can be carried out. Current sources in the human body can be localized by measuring the biomagnetic fields with multichannel SQUID systems. Important system aspects are the noise level, the ambient field suppression, the dynamic range, the reliability, the number of channels, and the arrangement of gradiometers. From the users point of view the most important quality factor is the accuracy with which a current dipole can be localized.

A test procedure is proposed to determine the localization power of the system. The crucial parts of the system determining the accuracy are pointed out.

Medizinische Bildgebung

This system differs from standard instruments in its modular approach. Various gradiometers can be coupled to the SQUIDs, the cryogenic system allows the exchange mwdizin single channels and the electronics is based on a cassette system.

Problems with thermal insulation, vibrations of the gradiometers and tilted gradiometer geometries are discussed and solutions are presented. The gauge factor medizij strain gauges is calculated considering the longitudinal and transverse strain sensitivity of the resistivity. The general result bilvgebende applied to free wire strain gauges, adhered foil strain gauges and thin film strain gauges.

The relation between the gauge factor and the piezoresistive constant. In time resolved luminescence spectra, taken within the temperature range of K, the two lowest excited states of rare gas crystals are observed. One of them, the long lived 3 state is identified as the initial state for transient absorption.

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The transient absorption spectra K indicate strong similarities between self-trapped excitons in the crystals and free excimers, but only in the energy region up to 1.

Higher energy levels and the continuum states of the self-trapped exciton are strongly influenced by solid state effects. Aims Chronic left atrial enlargement LAE increases the risk of atrial bildgebnde.

Electrocardiogram ECG criteria might provide a means to diagnose LAE bildgehende identify patients at risk; however, current criteria perform poorly. We seek to characterize the potentially differential effects of atrial dilation vs. We performed a computational study in a cohort of 72 anatomical variants, derived from four human atrial anatomies. P-waves were derived by simulating atrial excitation propagation and computing the body surface ECG.

Left verfahrrn dilation prolonged P-wave duration PWd in two of four subjects; in one subject a shortening, and in the other a variable change were seen. Left atrial concentric hypertrophy, in contrast, consistently increased Nildgebende terminal force in lead V1 PTF-V1 in all subjects through an enlarged amplitude while PWd was unaffected.

Combined hypertrophy essel dilation generally enhanced the effect of hypertrophy on PTF-V1. Electrocardiographic imaging ECGI reconstructs the electrical activity of the heart from a dense array of body-surface electrocardiograms and a patient-specific heart-torso geometry. Despite considerable development over the last decades, validation of ECGI is challenging. Secondly, it is challenging to obtain invasive ground truth data of high quality.

In this review, we discuss the current status of ECGI validation as bildgebene as the major challenges remaining for complete adoption of ECGI in clinical practice. Specifically, showing clinical benefit is essential for the adoption of ECGI. Such benefit may lie in patient outcome improvement, workflow improvement, or cost verfahrn. Continued interaction between engineers, basic scientists and physicians remains essential to find a hybrid between technical achievements, pathological mechanisms insights, and clinical benefit, to evolve this powerful technique towards a useful role in clinical practice.

Electrocardiographic imaging ECGI strongly relies on a priori assumptions and additional information to overcome ill-posedness.

The major challenge of obtaining good reconstructions consists in finding ways to add information that effectively restricts the solution space without violating properties of the sought solution.

In this work, we attempt to address this problem by constructing a spatio-temporal basis of body surface potentials BSP from simulations of many focal excitations. Measured BSPs are projected onto this basis and reconstructions are expressed as linear combinations of corresponding transmembrane voltage TMV basis vectors. The novel method was applied to simulations of atrial ectopic foci with three different conduction velocities.

Three signal-to-noise ratios SNR and bases of six different temporal lengths were considered. Reconstruction quality was evaluated using the spatial correlation coefficient of TMVs as well as i local activation times LAT.

The focus localization error was assessed by computing the geodesic distance between true and reconstructed foci. In conclusion, the new method improved reconstructions of atrial ectopic activity especially for low SNRs.

Localization of ectopic foci turned out to be more robust and more accurate. Preliminary experiments indicate that the basis generalizes to some extent from the training data and may even be applied for reconstruction of non-ectopic activity.

Optical mapping is widely used as a tool to investigate cardiac electrophysiology in ex vivo preparations. Digital filtering of bilgdebende data is an important requirement for robust subsequent data analysis and still a challenge when processing data acquired from thin mammalian myocardium. Therefore, we propose and investigate deer use of an adaptive dasel Gaussian filter for processing optical mapping signals from these kinds of tissue verfarhen having low signal-to-noise ratio SNR.