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  • 2000-2004  (517)
  • 1920-1924
  • 2000  (517)
  • Schlüsselwörter  (301)
  • Magnetic resonance imaging  (158)
  • ddc:000
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  • 2000-2004  (517)
  • 1920-1924
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  • 1
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    Two-Dimensional Adaptive Simulation of Dopant Diffusion in Silicon (2000)
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    Publication Date: 2014-02-26
    Description: One important step in the fabrication of silicon-based integrated circuits is the creation of semiconducting areas by diffusion of dopant impurities into silicon. Complex models have been developed to investigate the redistribution of dopants and point defects. In general, numerical analysis of the resulting PDEs is the central tool to assess the modelling process. We present an adaptive approach which is able to judge the quality of the numerical approximation and which provides an automatic mesh improvement. Using linearly implicit methods in time and multilevel finite elements in space, we are able to integrate efficiently the arising reaction-drift-diffusion equations with high accuracy. Two different diffusion processes of practical interest are simulated.
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    Language: English
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  • 2
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    An Uncoupling-Coupling Technique for Markov Chain Monte Carlo Methods (2000)
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    Publication Date: 2014-02-26
    Description: Uncoupling-coupling Monte Carlo (UCMC) combines uncoupling techniques for finite Markov chains with Markov chain Monte Carlo methodology. By determining almost invariant sets of the associated Markov operator, the Monte Carlo sampling splits by a hierarchical annealing process into the essential regions of the state space; therefore UCMC aims at avoiding the typical metastable behavior of Monte Carlo techniques. From the viewpoint of Monte Carlo, a slowly converging long-time Markov chain is replaced by a limited number of rapidly mixing short-time ones. The correct weighting factors for the various Markov chains are obtained via a coupling matrix, that connects the samplings from the different almost invariant sets. The underlying mathematical structure of this approach is given by a general examination of the uncoupling-coupling procedure. Furthermore, the overall algorithmic scheme of UCMC is applied to the $n$-pentane molecule, a well-known example from molecular dynamics.
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    Language: English
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  • 3
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    News from the Online Traveling Repairman (2000)
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    Publication Date: 2020-11-13
    Description: The traveling repairman problem (TRP) is a variant of the famous traveling salesman problem (TSP). The objective for the TRP is to minimize the latency, that is the the weighted sum of completion times of the cities, where the completion time of a city is defined to be the time in the tour before the city is reached. In the online traveling repairman problem (OLTRP) requests for visits to cities (points in a metric space) arrive online while the repairman is traveling. We analyze the performance of algorithms using competitive analysis, where the cost of an online algorithm is compared to that of an optimal offline algorithm. An optimal offline algorithm knows the entire request sequence in advance and can serve it with minimum cost. Recently, Feuerstein and Stougie presented a $9$-competitive algorithm for the OLTRP on the real line. In this paper we show how to use techniques from online-scheduling to obtain an $8$-competitive deterministic algorithm which works for any metric space. We also present a randomized algorithm which has a competitive ratio of $\frac{4}{\ln 2}\approx 5.7708$ against an oblivious adversary. All of our results also hold for the ``dial-a-ride'' generalization of the OLTRP, where objects have to be picked up and delivered by a server.
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  • 4
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    The Online-TSP Against Fair Adversaries (2000)
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    Publication Date: 2020-11-13
    Description: In the online traveling salesman problem requests for visits to cities (points in a metric space) arrive online while the salesman is traveling. The salesman moves at no more than unit speed and starts and ends his work at a designated origin. The objective is to find a routing for the salesman which finishes as early as possible. Performance of algorithms is measured through their competitive ratio, comparing the outcome of the algorithms with that of an adversary who provides the problem instance and therefore is able to achieve the optimal offline solution. Objections against such omnipotent adversaries have lead us to devise an adversary that is in a natural way, in the context of routing problems, more restricted in power. For the exposition we consider the online traveling salesman problem on the metric space given by the non-negative part of the real line. We show that a very natural strategy is~$3/2$-competitive against the conventional adversary, which matches the lower bound on competitive ratios achievable for algorithms for this problem. Against the more ``\emph{fair adversary}'', that we propose, we show that there exists an algorithm with competitive ratio $\frac{1+\sqrt{17}}{4}\approx 1.28$ and provide a matching lower bound. We also show competitiveness results for a special class of algorithms (called zealous algorithms) that do not allow waiting time for the server as long as there are requests unserved.
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    Language: English
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  • 5
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    Progress Towards a Combined MRI/Hyperthermia System (2000)
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    Publication Date: 2020-03-09
    Description: Regional hyperthermia, a clinical cancer therapy, is the main topic of the Sonderforschungsbereich Hyperthermia: Scientific Methods and Clinical Applications'' at Berlin. In recent years, technological improvements towards a better concentration of heat to the desired target region have been achieved. These include a rather sophisticated integrated software environment for therapy planning and a new hyperthermia applicator. In a next step, a detailed closed loop monitoring of the actual treatment is to be developed. For this purpose the hyperthermia applicator is combined with an MRI system, which will allow to check the positioning of the patients and to measure individual blood perfusion as well as the 3D temperature distribution. The measurements will then be employed for an on-line control of the whole treatment. In this intended setting, new fast feedback control algorithms will come into play.
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  • 6
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    Kooperativer Bibliotheksverbund Berlin-Brandenburg: Erste Erfahrungen im Produkionsbetrieb (2000)
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    Publication Date: 2020-03-11
    Description: In diesem Artikel wird der Status des Projekts Kooperativer Bibliotheksverbund Berlin-Brandenburg beschrieben, der im November 1999 mit der KOBV-Suchmaschine seinen produktiven Betrieb aufgenommen hat. Die Recherchemöglichkeiten im WWW werden erläutert, Zugriffszahlen genannt und Entwicklungsperspektiven skizziert. Dieser Bericht entspricht der schriftlichen Fassung eines gleichnamigen Vortrages, der auf dem 1. Gemeinsamen Kongreß der Bundesvereinigung Deutscher Bibliotheksverbände e.V. und der Deutschen Gesellschaft für Informationswissenschaft und Informationspraxis e.V. Information und Öffentlichkeit gehalten wurde, der vom 20. bis 23. März 2000 in Leipzig stattfand.
    Keywords: ddc:000
    Language: German
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  • 7
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    Asymptotic Results and a Markovian Approximation for the M(n)/M(n)/s+GI System (2000)
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    Publication Date: 2014-02-26
    Description: In this paper for the $M(n)/M(n)/s+GI$ system, i.e.\ for a $s$-server queueing system where the calls in the queue may leave the system due to impatience, we present new asymptotic results for the intensities of calls leaving the system due to impatience and a Markovian system approximation where these results are applied. Furthermore, we present a new proof for the formulae of the conditional density of the virtual waiting time distributions, recently given by Movaghar for the less general $M(n)/M/s+GI$ system. Also we obtain new explicit expressions for refined virtual waiting time characteristics as a byproduct.
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  • 8
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    Budget Constrained Minimum Cost Connected Medians (2000)
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    Publication Date: 2020-11-13
    Description: Several practical instances of network design problems require the network to satisfy multiple constraints. In this paper, we address the \emph{Budget Constrained Connected Median Problem}: We are given an undirected graph $G = (V,E)$ with two different edge-weight functions $c$ (modeling the construction or communication cost) and $d$ (modeling the service distance), and a bound~$B$ on the total service distance. The goal is to find a subtree~$T$ of $G$ with minimum $c$-cost $c(T)$ subject to the constraint that the sum of the service distances of all the remaining nodes $v \in V\setminus T$ to their closest neighbor in~$T$ does not exceed the specified budget~$B$. This problem has applications in optical network design and the efficient maintenance of distributed databases. We formulate this problem as bicriteria network design problem, and present bicriteria approximation algorithms. We also prove lower bounds on the approximability of the problem that demonstrate that our performance ratios are close to best possible
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  • 9
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    Polyhedral Results for the Edge Capacity Polytope (2000)
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    Publication Date: 2014-02-26
    Description: Network loading problems occur in the design of telecommunication networks, in many different settings. The polyhedral structure of this problem is important in developing solution methods for the problem. In this paper we investigate the polytope of the problem restricted to one edge of the network (the edge capacity problem). We describe classes of strong valid inequalities for the edge capacity polytope, and we derive conditions under which these constraints define facets. As the edge capacity problem is a relaxation of the network loading problem, their polytopes are intimately related. We, therefore, also give conditions under which the inequalities of the edge capacity polytope define facets of the network loading polytope. Furthermore, some structural properties are derived, such as the relation of the edge capacity polytope to the knapsack polytope. We conclude the theoretical part of this paper with some lifting theorems, where we show that this problem is polynomially solvable for most of our classes of valid inequalities. In a computational study the quality of the constraints is investigated. Here, we show that the valid inequalities of the edge capacity polytope are not only important for solving the edge capacity problem, but also for the network loading problem, showing that the edge capacity problem is an important subproblem.
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  • 10
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    Über Suchmaschinen, Verbünde und die Integration von Informationsangeboten (2000)
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    Publication Date: 2014-02-26
    Description: Die Entwicklung einer bibliothekarischen Suchmaschine ist das technisch-organisatorische Herztück des Kooperativen Bibliotheksverbundes Berlin-Brandenburg (KOBV). Auf dem Wege über diese Innovation verfolgen die Länder Berlin und Brandenburg und ihre Bibliotheken das Ziel, ihr Bibliothekswesen zu erneuern und zu reorganisieren. Die Entwicklung der Suchmaschine ist für die Partner im KOBV-Projekt kein Selbstzweck, sondern nur Mittel zum Zweck - insbesondere, um die heterogene Welt der in Berlin und in Brandenburg eingesetzten integrierten Bibliotheksinformationssysteme harmonisch miteinender zu verbinden. Mit der KOBV-Suchmaschine sind informationstechnische Sichtweisen und Methoden entstanden, die sich potentiell auch auf die überregionale Arbeit des KOBV auswirken können und in Kooperation mit den Bibliotheksverbänden auf die Zusammenarbeit der Verbünde insgesamt. Der Artikel konzentriert sich am Beispiel der KOBV-Such¡ma¡schine auch auf diesen Aspekt. Auf die Bibliotheken kommen mit dem Internet und dem World Wide Web für sie neuartige Medien, Mittel und Aufgaben zu, in erster Linie aus dem Bereich der Wissenschaften und der wissenschaftlichen Fachgesellschaften. Die Herausforderung besteht darin, die neuen elektronischen Informationen und Angebote zu integrieren. Das Stichwort hierzu lautet digitale Bibliothek bzw. virtuelle Fachbibliothek. Auch zu der Diskussion um diese aktuelle Entwicklung will der Artikel einen Beitrag leisten.
    Keywords: ddc:000
    Language: German
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  • 11
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    Parallel tempering and decorrelation of topological charge in full QCD (2000)
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    Publication Date: 2014-02-26
    Description: The improvement of simulations of QCD with dynamical Wilson fermions by combining the Hybrid Monte Carlo algorithm with parallel tempering is studied on $10^4$ and $12^4$ lattices. As an indicator for decorrelation the topological charge is used.
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  • 12
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    Re-Optimization of Signaling Transfer Points (2000)
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    Publication Date: 2014-02-26
    Description: In this paper we describe the results of a computational study towards the (re)optimization of signaling transfer points (STPs) in telecommunication networks. The best performance of an STP is achieved whenever the traffic load is evenly distributed among the internal components. Due to the continuously changing traffic pattern, the load of the components has to be re-optimized on a regular basis. Besides the balancing objective also the number of rearrangements have to be taken into account. In this paper we present two alternative formulations to deal with both requirements. Computational results show that for both formulations (near) optimal solutions can be obtained within reasonable time limits.
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  • 13
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    Density functional study of guanine and uracil quartets and of guanine quartet metal/ion complexes (2000)
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    Publication Date: 2014-02-26
    Description: The structures and interaction energies of guanine and uracil quartets have been determined by B3LYP hybrid density functional calculations. The total interaction energy $\Delta$E$^{T}$ of the $\it{C}$$_{4h}$-symmetric guanine quartet consisting of Hoogsteen type base pairs with two hydrogen bonds between two neighbour bases is -66.07 kcal/mol at the highest level. The uracil quartet with C6-H6...O4 interactions between the individual bases has only a small interaction energy of -20.92 kcal/mol and the interaction energy of -24.63 kcal/mol for the alternative structure with N3-H3...O4 hydrogen bonds is only slightly more negative. Cooperative effects contribute between 10 and 25 \% to all interaction energies. Complexes of metal ions with G-quartets can be classified into different structure types. The one with Ca$^{2+}$ in the central cavity adopts a $\it{C}$$_{4h}$-symmetric structure with coplanar bases, whereas the energies of the planar and non-planar Na$^{+}$ complexes are almost identical. The small ions Li$^{+}$, Be$^{2+}$, Cu$^{+}$ and Zn$^{2+}$ prefer a non-planar $\it{S}$$_{4}$-symmetric structure. The lack of co-planarity prevents probably a stacking of these base quartets. The central cavity is too small for K$^{+}$ ions and therefore this ion favours in contrast to all other investigated ions a $\it{C}$$_{4}$-symmetric complex, which is 4.73 kcal/mol more stable than the $\it{C}$$_{4h}$-symmetric one. The distance 1.665 {\AA} between K$^{+}$ and the root mean squares plane of the guanine bases is approximately half of the distance between two stacked G-quartets. The total interaction energy of alkaline earth ion complexes exceeds the ones with alkali ions. Within both groups of ions the interaction energy decreases with an increasing row position in the periodic table. The B3LYP and BLYP methods lead to similar structures and energies. Both methods are suitable for hydrogen-bonded biological systems. Compared with the before mentioned methods the HCTH functional leads to longer hydrogen bonds and different relative energies for two U-quartets. Finally we calculated also structures and relative energies with the MMFF94 forcefield. Contrary to all DFT methods, MMFF94 predicts bifurcated C-H...O contacts in the uracil quartet. In the G-quartet the MMFF94 hydrogen bond distances N2-H22...N7 are shorter than the DFT distances, whereas the N1-H1...O6 distances are longer.
    Keywords: ddc:000
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  • 14
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    Graphentheoretische Konzepte und Algorithmen (2000)
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    Publication Date: 2020-11-13
    Description: Das vorliegende Skript bietet eine Einf{ü}hrung in die Graphentheorie und graphentheoretische Algorithmen. Im zweiten Kapitel werden Grundbegriffe der Graphentheorie vorgestellt. Das dritte Kapitel besch{ä}ftigt sich mit der Existenz von Wegen in Graphen. Hier wird auch die L{ö}suung des ber{ü}hmten K{ö}nigsberger Br{ü}ckenproblems aufgezeigt und der Satz von Euler bewiesen. Im vierten Kapitel wird gezeigt, wie man auf einfache Weise die Zusammenhangskomponenten eines Graphen bestimmen kann. Im Kapitel sechs wird dann sp{ä}ter mit der Tiefensuche ein Verfahren vorgestellt, das schneller arbeitet und mit dessen Hilfe man noch mehr Informationen {ü}ber die Struktur eines Graphen gewinnen kann. In den folgenden Kapiteln werden Algorithmen vorgestellt, um minimale aufspannenden B{ä}ume, k{ü}rzeste Wege und maximale Fl{ü}sse in Graphen zu bestimmen. Am Ende des Skripts wird ein kurzer Einblick in die planaren Graphen und Graphhomomorphismen geboten.
    Keywords: ddc:000
    Language: German
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  • 15
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    Computer-aided design of novel siderophores: Pyridinochelin (2000)
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    Publication Date: 2014-02-26
    Description: Pyridinochelin, a novel catecholate type siderophore, has been designed on the basis of the active analog enterobactin. Growth promotion tests indicate that this synthetic siderophore feeds various pathogenic bacteria effectively with iron even though it lacks one catecholate group compared to enterobactin. The superposition of the siderophore structures suggests that the structure of the skeleton connecting the catecholate groups might be an important factor for the iron transport.
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  • 16
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    Adaptive Linearly Implicit Methods for Heat and Mass Transfer Problems (2000)
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    Publication Date: 2019-05-10
    Description: Dynamical process simulation of complex real-life problems often requires the use of modern algorithms, which automatically adapt both the time and space discretization in order to get error-controlled approximations of the solution. In this paper, a combination of linearly implicit time integrators of Rosenbrock type and adaptive multilevel finite elements based on a posteriori error estimates is presented. This approach has proven to work quite satisfactorily for a wide range of challenging practical problems. We show the performance of our adaptive method for two applications that arise in the study of flame balls and brine transport in porous media.
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  • 17
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    The Essential Spectral Radius and Asymptotic Properties of Transfer Operators (2000)
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    Publication Date: 2014-02-26
    Description: The statistical behavior of deterministic and stochastic dynamical systems may be described using transfer operators, which generalize the notion of Frobenius Perron and Koopman operators. Since numerical techniques to analyze dynamical systems based on eigenvalues problems for the corresponding transfer operator have emerged, bounds on its essential spectral radius became of interest. This article shows that they are also of great theoretical interest. We give an analytical representation of the essential spectral radius in $L^{1}\!(\mu)$, which then is exploited to analyze the asymptotical properties of transfer operators by combining results from functional analysis, Markov operators and Markov chain theory. In particular, it is shown, that an essential spectral radius less than $1$, constrictiveness and some weak form'' of the so--called Doeblin condition are equivalent. Finally, we apply the results to study three main problem classes: deterministic systems, stochastically perturbed deterministic systems and stochastic systems.
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  • 18
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    The Classes of Critically and Anticritically Perfect Graphs (2000)
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    Publication Date: 2014-02-26
    Description: We focus on two new types of extremal graphs with respect to perfectness: critically and anticritically perfect graphs that lose their perfectness by simply deleting and adding an arbitrary edge, respectively. We present examples and study properties in order to compare critically and anticritically perfect graphs with minimally imperfect graphs, another type of extremal graphs with respect to perfectness. We discuss two attempts to characterize the classes of all critically and anticritically perfect graphs and give a brief overview on classes of perfect graphs which contain critically or anticritically perfect graphs.
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  • 19
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    A path-following method for linear complementarity problems based on the affine invariant Kantorovich Theorem (2000)
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    Publication Date: 2014-02-26
    Description: A path following algorithm for linear complementarity problems is presented. Given a point $z$ that approximates a point $z(\tau)$ on the central path with complementarity gap $\tau$, one determines a parameter $\theta\in (0,1)$ so that this point satisfies the hypothesis of the affine invariant Kantorovich Theorem for the equation defining $z((1-\theta)\tau)$. It is shown that $\theta$ is bounded below by a multiple of $n^{-1/2}$, where $n$ is the dimension of the problem. Since the hypothesis of of the Kantorovich Theorem is satisfied the sequence generated by Newton's method, or by the simplified Newton method, will converge to $z((1-\theta)\tau)$. We show that the number of steps required to obtain an acceptable approximation of $z((1-\theta)\tau)$ is bounded above by a number independent of $n$. Therefore the algorithm has $O(\sqrt{n}L)$-iteration complexity. The parameters of the algorithm can be determined in such a way that only one Newton step is needed each time the complementarity gap is decreased.
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  • 20
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    Counting stable solutions of sparse polynomial systems in chemistry (2000)
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    Publication Date: 2014-02-26
    Description: The polynomial differential system modelling the behavior of a chemical reaction is given by graphtheoretic structures. The concepts from toric geometry are applied to study the steady states and stable steady states. Deformed toric varieties give some insight and enable graph theoretic interpretations. The importance of the circuits in the directed graph are emphazised. The counting of positive solutions of a sparse polynomial system by B.\ Sturmfels is generalized to the counting of stable positive solutions in case of a polynomial differential equation. The generalization is based on a method by sparse resultants to detect whether a system may have a Hopf bifurcation. Special examples from chemistry are used to illustrate the theoretical results.
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  • 21
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    Distributed Visualization with OpenGL Vizserver: Practical Experiences (2000)
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    Publication Date: 2020-03-09
    Description: The increasing demand for distributed solutions in computing technology does not stop when it comes to visualization techniques. However, the capabilities of todays applications to perform remote rendering are limited by historical design legacys. Especially the popular X11 protokoll, which has been proven to be extremely flexible and usefull for remote 2D graphics applications, breaks down for the case of remote 3D rendering. In this white paper, we give a short overview of generic remote rendering technologies available today, and compare their performance to the recently released vizserver by SGI: a network extension to the SGI OpenGL rendering engines.
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  • 22
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    Semidefinite Programming for Combinatorial Optimization (2000)
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    Publication Date: 2020-08-05
    Description: This book offers a self-contained introduction to the field of semidefinite programming, its applications in combinatorial optimization, and its computational methods. We equip the reader with the basic results from linear algebra on positive semidefinite matrices and the cone spanned by them. Starting from linear programming, we introduce semidefinite programs and discuss the associated duality theory. We then turn to semidefinite relaxations of combinatorial optimization and illustrate their interrelation. In the second half we deal with computational methods for solving semidefinite programs. First, the interior point approach, its iteration complexity, and implementational issues are discussed. Next, we explain in great detail the spectral bundle method, which is particularly suited for large scale semidefinite programming. One of the most successful techniques in integer linear programming is the cutting plane approach which improves an initial relaxation by adding violated inequalities. We explore possibilities to combine the two solution methods with the cutting plane approach in order to strengthen semidefinite relaxations of combinatorial optimization problems.
    Keywords: ddc:000
    Language: English
    Type: doctoralthesis , doc-type:doctoralThesis
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  • 23
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    Ermittlung von Programmlaufzeiten anhand von Speicherzugriffen, Microbenchmarks und Simulation vonSpeicherhierarchien (2000)
    Details
    Publication Date: 2021-01-21
    Description: \\{\bf Zusammenfassung:} Kostenmodelle dienen der Ermittlung von Programmlaufzeiten, zum Vergleich der Effizienz von Algorithmen und zur Analyse des Verhaltens von Speicherhierarchien. Ein neuartiges Kostenmodell ist das Latency-of-Data-Access (LDA) Modell, das mehrere hierarchische Speicherebenen mit unterschiedlichen Latenzzeiten berü{}cksichtigt. In dieser Diplomarbeit wird ein Simulator fü{}r Speicherhierarchien prä{}sentiert, der die Berechnung von Programmausfü{}hrungszeiten nach dem LDA-Modell erlaubt. Mit Hilfe des Simulators wird die These geprü{}ft, da\ss{} mit diesem Modell die Ausfü{}hrungszeit eines Programms adä{}quat abgeschä{}tzt werden kann. Mit dem Simulator ist es erstmals praktikabel mö{}glich, Programmausfü{}hrungszeiten nach dem LDA-Modell zu bestimmen. Der Simulator kann fü{}r Systeme mit unterschiedlichen Speicherarchitekturen konfiguriert werden und unterstü{}tzt Mehrprozessorsysteme mit gemeinsamem Speicher (SMP-Systeme) mit verschiedenen Kohä{}renzprotokollen. Der Simulator kann mit den Ergebnissen von Microbenchmarks konfiguriert werden, die die Architekturparameter einer Speicherhierarchie messen. Die Ergebnisse bestä{}tigen die These nicht nur fü{}r Einzelprozessorsysteme, sondern auch fü{}r SMP-Systeme, wo gleichzeitig interagierende Prozessoren gegenseitig ihre Zugriffssequenz auf Zwischenspeicher beeinflussen. Zusä{}tzlich wurde eine neue Einsatzmö{}glichkeit des LDA-Modells entwickelt, um die Ausfü{}hrungszeit von Programmteilen zu bestimmen. Einzelne Zugriffskosten kö{}nnen einem mehrerer parallel laufender Modelle zugeordnet werden. Dadurch kö{}nnen Kosten, die Zugriffe auf einzelne Speicherbereiche verursachen, separat bestimmt werden. Diese Profiling-Technik erlaubt Optimierungen an Datenstrukturen und Speicherzugriffsmustern durch prä{}zise und gezielte Informationsproduktion.Cost models are used to determine the execution time of programs, to compare the efficiency of algorithms, and to analyse the behaviour of memory hierarchies. The Latency-of-Data-Access (LDA) model that takes into account multiple hierarchical memory levels with different latencies, is a newly proposed, innovative cost model. In this diploma-thesis, a simulator for memory hierarchies is presented that allows the calculation of execution times using the LDA-model. The simulator is used to prove the claim that the execution time of a program can be accurately estimated with the LDA-model. With the simulator, it is for the first time possible to determine the execution time of programs with this model in a practical way. The simulator can be configured for systems with various cache architectures and supports shared memory (SMP) multiprocessor systems with different cache coherence protocols. The simulator can be configured with the results from microbenchmarks which measure the architectural properties of a memory hierarchy. The results confirm the claim not only for single processor systems, but also for SMP systems, where concurrently interacting processors influence each others cache access sequence. Additionally, a new field of usage of the LDA-model was developed to determine execution times of program parts. Single access costs can be assigned to one of several parallel running models. As an example the costs of accesses to different memory areas can be split and determined separately. This profiling technique allows to optimise data structures and memory access patterns of sequential and parallel SMP programs by precise production of information.
    Keywords: ddc:000
    Language: German
    Type: reportzib , doc-type:preprint
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    SBmethod --- A C++ Implementation of the Spectral Bundle Method. Manual to Version 1.1 (2000)
    Details
    Publication Date: 2014-02-26
    Description: \texttt{SBmethod}, Version 1.1, is an implementation of the spectral bundle method for eigenvalue optimization problems of the form \begin{displaymath} \min_{y\in \mathbf{R}^m}\;\; a\;\lambda_{\max}(C-\sum_{i=1}^{m} A_i y_i)+b^Ty. \end{displaymath} The design variables $y_i$ may be sign constrained, $C$ and and $A_i$ are given real symmetric matrices, $b\in\mathbf{R}^m$ allows to specify a linear cost term, and $a〉0$ is a constant multiplier for the maximum eigenvalue function $\lambda_{\max}(\cdot)$. The code is intended for large scale problems and allows to exploit structural properties of the matrices such as sparsity and low rank structure. The manual contains instructions for installation and use of the program. It describes in detail input format, options, and output. The meaning of the variables and parameters is made precise by relating them to a mathematical description of the algorithm in pseudocode.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
    Format: application/postscript
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  • 25
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    Stable Multi-Sets (2000)
    Details
    Publication Date: 2014-11-10
    Description: In this paper we introduce a generalization of stable sets: stable multi-sets. A stable multi-set is an assignment of integers to the vertices of a graph, such that specified bounds on vertices and edges are not exceeded. In case all vertex and edge bounds equal one, stable multi-sets are equivalent to stable sets. For the stable multi-set problem, we derive reduction rules and study the associated polytope. We state necessary and sufficient conditions for the extreme points of the linear relaxation to be integer. These conditions generalize the conditions for the stable set polytope. Moreover, the classes of odd cycle and clique inequalities for stable sets are generalized to stable multi-sets and conditions for them to be facet defining are determined. The study of stable multi-sets is initiated by optimization problems in the field of telecommunication networks. Stable multi-sets emerge as an important substructure in the design of optical networks.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
    Format: application/pdf
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  • 26
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    SteinLib: An Updated Library on Steiner Tree Problems in Graphs (2000)
    Details
    Publication Date: 2020-02-11
    Description: In this paper we present the {\em SteinLib}, a library of data sets for the Steiner tree problem in graphs. This library extends former libraries on Steiner tree problems by many new interesting and difficult instances, most of them arising from real-world applications. We give a survey on the difficulty of these problem instances by giving references to state-of-the-art software packages that were the first or are currently among the best to solve these instances.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 27
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    Anatomy of a Resource Management System for HPC-Clusters (2000)
    Details
    Publication Date: 2014-02-26
    Description: Workstation clusters are often not only used for high-throughput computing in time-sharing mode but also for running complex parallel jobs in space-sharing mode. This poses several difficulties to the resource management system, which must be able to reserve computing resources for exclusive use and also to determine an optimal process mapping for a given system topology. On the basis of our CCS software, we describe the anatomy of a modern resource management system. Like Codine, Condor, and LSF, CCS provides mechanisms for the user-friendly system access and management of clusters. But unlike them, CCS is targeted at the effective support of space-sharing parallel and even metacomputers. Among other features, CCS provides a versatile resource description facility, topology-based process mapping, pluggable schedulers, and hooks to metacomputer management.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
    Format: application/postscript
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  • 28
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    Autos, Ziegen und Streithähne (2000)
    Details
    Publication Date: 2021-02-01
    Description: Das aus den Medien bekannte umstrittene Ziegenproblem (auch Drei-Türen-Problem genannt) wird vollständig analysiert und gelöst. In der Streitfrage spielen sprachliche Mehrdeutigkeiten der Problemformulierung eine wesentliche Rolle; zudem werden Zufallsereignisse mit willkürlicher Information über deren Ergebnisse verwechselt. Tatsächlich erweisen sich beide strittigen Lösungen als teilweise richtige Bestandteile der Gesamtlösung. Die Argumentation wird in allgemeinverständlicher Sprache geführt und anschliessend durch eine formale mathematische Betrachtung ergänzt.
    Keywords: ddc:000
    Language: German
    Type: reportzib , doc-type:preprint
    Format: application/postscript
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  • 29
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    Kooperativer Bibliotheksverbund Berlin-Brandenburg (KOBV) - Konzept, Erfahrungen, Ausblick - (2000)
    Details
    Publication Date: 2020-11-13
    Description: Der Aufsatz ist die ausgearbeitete Fassung eines Vortrages, gehalten auf dem 2. BSZ-Kolloquium des Bibliotheksservice-Zentrums Baden-Württemberg (BSZ) am 10. Oktober 2000 in Konstanz. Der Kooperative Bibliotheksverbund Berlin-Brandenburg, kurz KOBV, ist ein sehr junger Verbund - genauer gesagt, befindet er sich im Oktober 2000 immer noch in der Aufbauphase. Das KOBV-Projekt hat am 1. April 1997 begonnen und wird am 31. Dezember 2000 enden. Ab 2001 wird der KOBV in eine institutionalisierte Form überführt, die - wie bereits das Projekt - am Konrad-Zuse-Zentrum für Informationstechnik Berlin (ZIB) - angesiedelt wird. Mit dem KOBV wurde ein in technischer wie auch in organisatorischer Hinsicht neuartiger Bibliotheksverbund aufgebaut, der auf der \glqq Internetphilosophie\grqq basiert: Den technischen Kern bildet eine eigens entwickelte Suchmaschine; die Organisation ist dezentral ausgerichtet und gründet sich auf der Kooperation der KOBV-Partner. In dem Vortrag werden das technische und das organisatorische Verbundkonzept vorgestellt, über die Erfahrungen nach einjähriger Betriebsdauer berichtet und ein kurzer Ausblick darüber gegeben, wie es mit dem KOBV weitergeht.
    Keywords: ddc:000
    Language: German
    Type: reportzib , doc-type:preprint
    Format: application/postscript
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  • 30
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    Spezifikation der Schnittstelle zwischen KOBV-Suchmaschine und Lokalsystemen (2000)
    Details
    Publication Date: 2020-11-13
    Description: Die Kommunikation zwischen der KOBV-Suchmaschine und entfernten Bibliotheksinformationssystemen unterschiedlicher Hersteller wird über das Standardprotokoll Z39.50 abgewickelt. Die Suchmaschine ermöglicht Online-Recherchen in lokalen Bibliotheksinformationssystemen, die dazu ein Z39.50 Target (Server) zur Verfügung stellen müssen. Die Suchmaschine liefert ihre Daten ebenfalls über Z39.50 aus. Ein Lokalsystem benötigt hierfür einen Z39.50 Origin (Client). In dem Papier wird die Schnittstelle zwischen der KOBV-Suchmaschine und lokalen Bibliothekssystemen spezifiziert: Es werden die grundlegenden Anforderungen an Lokalsysteme definiert und die Konfigurationsparameter für die Z39.50-Kommunikation zwischen KOBV-Suchmaschine und Lokalsystemen beschrieben.
    Keywords: ddc:000
    Language: German
    Type: reportzib , doc-type:preprint
    Format: application/postscript
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  • 31
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    Implementation von WAP-Diensten für die SGI/CRAY T3E des ZIB (2000)
    Details
    Publication Date: 2014-02-26
    Description: Die zunehmende Verfügbarkeit von mobilen Geräten, die mit einem Internetanschluß ausgerüstet sind, bringt auch eine steigende Nachfrage nach Informationsdiensten für diese Art von Clients mit sich. Das ZIB stellt mit seinem Höchstleistungsrechner vom Typ SGI/CRAY T3E Wissenschaftlern große Rechenkapazitäten zur Verfügung. Im Rahmen dieser Studienarbeit wurde ein WAP-Interface zur T3E entwickelt, das es den Nutzern ermöglicht, über ein mobiles, WAP-fähiges Gerät Informationen zur Betriebsbereitschaft und zur Auslastung des Höchstleistungsrechners, sowie Informationen zu den von ihnen in Auftrag gegebenen Rechenjobs abzurufen. Die Untersuchung der aktuellen Möglichkeiten in der mobilen Kommunikation brachte einige Einschränkungen für das geplante Informationsangebot mit sich. So mußte auf Grund von Sicherheitsbedenken auf eine tatsächliche Interaktionsmöglichkeit (z.B. neue Rechenjobs zu starten) verzichtet werden. Demgegenüber konnte gezeigt werden, daß die Bereitstellung der gleichen Informationen für unterschiedliche Arten von Clients (WWW-Browser $\rightarrow$ HTML, WAP-Browser $\rightarrow$ WML) durch die Verwendung von XML als internes Datenformat problemlos möglich ist. Es hat sich gezeigt, daß die Bereitstellung eines WAP-Informationsdienstes auf Grund verschiedener Inkompatibilitätsprobleme (verschiedene Gateways, verschiedene WAP-Browser) mit erheblichem Aufwand verbunden sein kann. An dieser Stelle besteht noch Handlungsbedarf seitens der Hersteller dieser Softwarepakete.
    Keywords: ddc:000
    Language: German
    Type: reportzib , doc-type:preprint
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  • 32
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    Jahresbericht 1999 (2000)
    Details
    Publication Date: 2019-10-24
    Keywords: ddc:000
    Language: German
    Type: annualzib , doc-type:report
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  • 33
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    Verkehrsplanung: Bessere Lösungen mit Mathematik (2000)
    Details
    Publication Date: 2014-02-26
    Description: Anwendungen der Mathematik in der Verkehrs- und Transporttechnologie haben eine große und bedeutende Tradition. Natürlich wurden die ersten Fahrzeuge mit der ingenieurmäßigen Methode von Versuch, Irrtum und Verbesserung entworfen. Aber schon sehr bald kamen mathematische Berechnungen hinzu, mit denen mechanische Eigenschaften von Fahrzeugteilen ermittelt und zum Teil optimiert wurden. Die hierzu erforderliche Mathematik wurde in diesem Jahrhundert zu einem mächtigen Werkzeugkasten ausgebaut. Mit diesem kann man heute z.B. hocheffiziente Motoren mit geringem Schadstoffausstoß entwerfen, aerodynamisch günstige Fahrzeugprofile ermitteln und Flugzeugflügel berechnen, die die gewünschte Last sicher und mit geringem Treibstoffaufwand tragen. Die Mathematik unterstützt die Technologie des Verkehrs beginnend bei globalen Designfragen bis hin zur Spezifizierung von Materialeigenschaften kleinster Bauteile; sie berechnet mit hoher Präzision energieoptimale Bahnen von Raumflugkörpern oder zeitoptimale Trajektorien für Flugzeuge, steuert automatische Roboteranlagen oder innerbetriebliche Transportsysteme.
    Keywords: ddc:000
    Language: German
    Type: reportzib , doc-type:preprint
    Format: application/postscript
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  • 34
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    Hierarchical Sparsity in Multistage Convex Stochastic Programs (2000)
    Details
    Publication Date: 2021-02-01
    Description: Interior point methods for multistage stochastic programs involve KKT systems with a characteristic global block structure induced by dynamic equations on the scenario tree. We generalize the recursive solution algorithm proposed in an earlier paper so that its linear complexity extends to a refined tree-sparse KKT structure. Then we analyze how the block operations can be specialized to take advantage of problem-specific sparse substructures. Savings of memory and operations for a financial engineering application are discussed in detail.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
    Format: application/postscript
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  • 35
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    Adaptive hierarchical cluster analysis by Self-Organizing Box Maps (2000)
    Details
    Publication Date: 2014-02-26
    Description: The present paper aims at an extension of {\sc Kohonen's} Self-Organizing Map (SOM) algorithm to be called Self-Organizing Box Map (SOBM) algorithm; it generates box codebooks in lieu of point codebooks. Box codebooks just like point codebooks indirectly define a Voronoi tessellation of the input space, so that each codebook vector represents a unique set of points. Each box codebook vector comprises a multi-dimensional interval that approximates the related partition of the Voronoi tessellation. Upon using the automated cluster identification method that has recently been developed by the authors, the codebook vectors can be grouped in such a way that each group represents a point cluster in the input space. Since the clustering usually depends on the size of the SOM, one cannot be sure, whether the clustering comes out to be optimal. Refinement of part of the identified clusters would often improve the results. This paper presents the concept of an adaptive multilevel cluster algorithm that performs such refinements automatically. Moreover the paper introduces a concept of essential dimensions and suggests a method for their identification based on our herein suggested box codebooks. Applications of the algorithm to molecular dynamics will be described in a forthcoming paper.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 36
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    Capacitated Network Design with Multicast Commodities (2000)
    Details
    Publication Date: 2014-02-26
    Description: This paper addresses the problem of designing a minimum cost network whose capacities are sufficiently large to allow a feasible routing of a given set of multicast commodities. A multicast commodity consists of a set of two or mo re terminals that need to be connected by a so called broadcast tree, which consumes on all of its edges a capacity as large as the demand value associated with that commodity. We model the network design problem with multicast commodities as the problem of packing capacitated Steiner trees in a graph. In the first part of the paper we present three mixed-integer programming formulations for this problem. The first natural formulation uses only one integer capacity variable for each edge and and one binary tree variable for each commodity-edge pair. Applying well-known techniques from the Steiner tree problem, we then develop a stronger directed and a multicommodity flow based mixed-integer programming formulation. In the second part of the paper we study the associated polyhedra and derive valid and even facet defining inequalities for the natural formulation. Finally, we describe separation algorithms for these inequalities and present computational results that demonstrate the strength of our extended formulations.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 37
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    Ermittlung von Programmlaufzeiten anhand von Speicherzugriffen, Microbenchmarks und Simulation von Speicherhierarchien (2000)
    Details
    Publication Date: 2021-01-21
    Description: Kostenmodelle dienen der Ermittlung von Programmlaufzeiten, zum Vergleich der Effizienz von Algorithmen und zur Analyse des Verhaltens von Speicherhierarchien. Ein neuartiges Kostenmodell ist das Latency-of-Data-Access (LDA) Modell, das mehrere hierarchische Speicherebenen mit unterschiedlichen Latenzzeiten berücksichtigt. In dieser Diplomarbeit wird ein Simulator für Speicherhierarchien präsentiert, der die Berechnung von Programmausführungszeiten nach dem LDA-Modell erlaubt. Mit Hilfe des Simulators wird die These geprüft, daß mit diesem Modell die Ausführungszeit eines Programms adäquat abgeschätzt werden kann. Mit dem Simulator ist es erstmals praktikabel möglich, Programmausführungszeiten nach dem LDA-Modell zu bestimmen. Der Simulator kann für Systeme mit unterschiedlichen Speicherarchitekturen konfiguriert werden und unterstützt Mehrprozessorsysteme mit gemeinsamem Speicher (SMP-Systeme) mit verschiedenen Kohärenzprotokollen. Der Simulator kann mit den Ergebnissen von Microbenchmarks konfiguriert werden, die die Architekturparameter einer Speicherhierarchie messen. Die Ergebnisse bestätigen die These nicht nur für Einzelprozessorsysteme, sondern auch für SMP-Systeme, wo gleichzeitig interagierende Prozessoren gegenseitig ihre Zugriffsse-quenz auf Zwischenspeicher beeinflussen. Zusätzlich wurde eine neue Einsatzmöglichkeit des LDA-Modells entwickelt, um die Ausführungszeit von Programmteilen zu bestimmen. Einzelne Zugriffskosten können einem mehrerer parallel laufender Modelle zugeordnet werden. Dadurch können Kosten, die Zugriffe auf einzelne Speicherbereiche verursachen, separat bestimmt werden. Diese Profiling-Technik erlaubt Optimierungen an Datenstrukturen und Speicherzugriffsmustern durch präzise und gezielte Informationsproduktion.
    Description: Cost models are used to determine the execution time of programs, to compare the efficiency of algorithms, and to analyse the behaviour of memory hierarchies. The Latency-of-Data-Access (LDA) model that takes into account multiple hierarchical memory levels with different latencies, is a newly proposed, innovative cost model. In this diploma-thesis, a simulator for memory hierarchies is presented that allows the calculation of execution times using the LDA model. The simulator is used to prove the claim that the execution time of a program can be accurately estimated with the LDA model. With the simulator, it is for the first time possible to determine the execution time of programs with this model in a practical way. The simulator can be configured for systems with various cache architectures and supports shared memory (SMP) multiprocessor systems with different cache coherence protocols. The simulator can be configured with the results from Microbenchmarks which measure the architectural properties of a memory hierarchy. The results confirm the claim not only for single processor systems, but also for SMP systems, where concurrently interacting processors influence each others cache access sequence. Additionally, a new field of usage of the LDA model was developed to determine execution times of program parts. Single access costs can be assigned to one of several parallel running models. As an example the costs of accesses to different memory areas can be split and determined separately. This profiling technique allows to optimise data structures and memory access patterns of sequential and parallel SMP programs by precise production of information.
    Keywords: ddc:000
    Language: German
    Type: masterthesis , doc-type:masterThesis
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  • 38
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    Visions of Numerical Relativity 1999 (2000)
    Details
    Publication Date: 2020-03-09
    Description: We present visualizations of recent supercomputer simulations from numerical relativity, exploiting the progress in visualization techniques and numerical methods also from an artistic point of view. The sequences have been compiled into a video tape, showing colliding black holes, orbiting and merging neutron stars as well as collapsing gravitational waves. In this paper we give some background information and provide a glance at the presented sequences.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 39
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    The Symbolic Integration of Exact PDEs (2000)
    Details
    Publication Date: 2014-02-26
    Description: An algorithm is described to decide if a given polynomial differential expression $\Delta$ of multivariate functions is exact, i.e. whether there exists a first integral $P$ such that $D_xP = \Delta$ for any one of a set of variables $x$ and to provide the integral $P$. A generalization is given to allow integration in the case that the exactness is prohibited by terms which contain only functions of not all the independent variables.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 40
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    Algorithmen- und Softwareoptimierung für die Satellitenbahn- und Schwerefeldmodellierung (2000)
    Details
    Publication Date: 2014-02-26
    Description: Dieser Report enthält die Ergebnisse der Untersuchungen, die gemäss dem Forschungs-- und Entwicklungsvertrag Gravity zwischen dem GeoForschungsZentrum Potsdam und dem Konrad--Zuse--Zentrum Berlin vorgenommen wurden. Die damit vereinbarte wissenschaftliche Kooperation hat die folgenden Ziele: \item{die am GFZ vorhandenen Algorithmen und Softwaremodule auf ihre Effizienz hisichtlich Nutzung der Rechnerresourcen zu untersuchen und Lösungen für einen schnelleren Datendurchsatz zu entwickeln und zu implementieren,} \item{Methoden zur Regularisierung und Lösung schlecht konditionierter Normalgleichungssysteme (für Schwerefeldkoeffizienten) kritisch zu untersuchen und eine mathematisch objektive Strategie der Regularisierung zu entwickeln, und} \item{insbesondere im Hinblick auf die Anforderungen bei GRACE, verschiedene Bahnintegrationsverfahren hinsichtlich ihrer numerischen Genauigkeit und Einsatzmöglichkeiten zu untersuchen.}
    Keywords: ddc:000
    Language: German
    Type: reportzib , doc-type:preprint
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  • 41
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    A Projection Method for Two-Phase Incompressible Flow with Surface Tension and Sharp Interface Resolution (2000)
    Details
    Publication Date: 2014-02-26
    Description: We present a fully second order projection method for the simulation of two-phase incompressible flow with surface tension. The Navier-Stokes equations are solved with a projection method on a fixed Cartesian grid. The free interface between the two fluids is tracked with a level set approach. The conditions at the interface for the pressure, the pressure gradient, and the velocity are explicitly incorporated into the scheme leading to a sharp representation of the pressure discontinuity and the interfacial force. The scheme in the presented form does not introduce additional points in the standard finite difference stencils. Computational results are compared with analytic solutions for a static round bubble, damped surface waves, and Rayleigh-Taylor instabilities.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 42
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    Hyperthermia Treatment Planning with HyperPlan - User's Manual (2000)
    Details
    Publication Date: 2020-03-09
    Description: HyperPlan is a software system for performing 3D-simulations and treatment planning in regional hyperthermia. It allows the user to understand the complex effects of electromagnetic wave propagation and heat transport inside a patient's body. Optimized power amplitudes and phase settings can be calculated for the BSD radiowave applicators Sigma 60 and Sigma 2000 (eye-applicator). HyperPlan is built on top of the modular, object-oriented visualization system Amira. This system already contains powerful algorithms for image processing, geometric modelling and 3D graphics display. HyperPlan provides a number of hyperthermia-specific modules, allowing the user to create 3D tetrahedral patient models suitable for treatment planning. In addition, all numerical simulation modules required for hyperthermia simulation are part of HyperPlan. This guide provides a step-by-step introduction to hyperthermia planning using HyperPlan. It also describes the usage of the underlying visualization system Amira.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
    Format: application/postscript
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  • 43
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    Electromagnetic phased arrays for regional hyperthermia -- optimal frequency and antenna arrangement (2000)
    Details
    Publication Date: 2014-02-26
    Description: In this paper we investigate the effects of the three-dimensional arrangement of antennas and frequency on temperature distributions that can be achieved in regional hyperthermia using an electromagnetic phased array. We compare the results of power-based and temperature-based optimization. Thus we are able to explain the discrepancies between previous studies favouring more antenna rings on the one hand and more antennas per ring on the other hand. We analyze the sensitivity of the results with respect to changes in amplitudes and phases as well as patient position. This analysis can be used for different purposes. First, it provides additional criteria for selecting the optimal frequency. Second, it can be used for specifying the required phase and amplitude accuracy for a real phased array system. Furthermore, it may serve as a basis for technological developments in order to reduce both types of sensitivities described above.
    Keywords: ddc:000
    Language: English
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    Kooperativer Bibliotheksverbund Berlin-Brandenburg (KOBV) (2000)
    Details
    Publication Date: 2020-11-13
    Description: Der Kooperative Bibliotheksverbund Berlin-Brandenburg (KOBV) wurde in den Jahren 1997-2000 im Rahmen eines wissenschaftlichen Projektes eingerichtet. Er stellt eine neuartige Form von Bibliotheksverbund dar. Sein technisches Konzept und sein organisatorischer Aufbau basieren auf der Internetphilosophie. Den informationstechnischen Kern bildet eine Suchmaschine, die die heterogenen lokalen Bibliothekssysteme miteinander verbindet. Die KOBV-Organisation ist dezentral. Sie wird getragen von der Kooperation der Bibliotheken in Berlin und Brandenburg; diese werden von einer kleinen Verbundzentrale unterstützt. Die KOBV-Suchmaschine ist zu erreichen unter: {\begin{rawhtml}〈a href="http://www.kobv.de/suche/"〉 〈i〉 http://www.kobv.de/suche/ 〈/i〉 〈/a〉\end{rawhtml}}
    Keywords: ddc:000
    Language: German
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  • 45
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    Mathematik in der Industrie: interessante Branchen und zukünftige Einsatzfelder (2000)
    Details
    Publication Date: 2014-02-26
    Description: Dieser kurze Artikel hat keine umfassende Übersicht zum Ziel. Basierend auf eigenen Erfahrungen durch Projekte mit Industriefirmen möchte ich einige Branchen erwähnen, bei denen nach meiner Einschätzung Mathematik in Zukunft zunehmend Anwendung finden wird. Ich werde das anhand konkreter Beispiele erläutern. Mathematik ersetzt in der Regel traditionelle Analyse-, Planungs- und Entwurfstechniken. Den (nicht leichten) Schritt zum Einsatz mathematischer Methoden macht ein Praktiker nur, wenn es sich für ihn ``lohnt''. Wann sich dies lohnt, ist schwer abzuschätzen. Man kann aber einige Indikatoren dafür finden, ob eine Branche für den Einsatz von Mathematik ``reif'' ist. Ob es dann dazu kommt, hängt von vielen Faktoren ab, nicht zuletzt von der Psychologie und dem sozialen Umfeld der beteiligten Personen sowie der Bereitschaft, sich auf ein so schwieriges Terrain zu begeben und Kompromisse einzugehen. Gerade letzteres fällt Mathematikern gelegentlich schwer.
    Keywords: ddc:000
    Language: German
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  • 46
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    Circuit Admissible Triangulations of Oriented Matroids (2000)
    Details
    Publication Date: 2014-11-10
    Description: All triangulations of euclidean oriented matroids are of the same PL-homeomorphism type by a result of Anderson. That means all triangulations of euclidean acyclic oriented matroids are PL-homeomorphic to PL-balls and that all triangulations of totally cyclic oriented matroids are PL-homeomorphic to PL-spheres. For non-euclidean oriented matroids this question is wide open. One key point in the proof of Anderson is the following fact: for every triangulation of a euclidean oriented matroid the adjacency graph of the set of all simplices ``intersecting'' a segment $[p_-p_+]$ is a path. We call this graph the $[p_-p_+]$-adjacency graph of the triangulation. While we cannot solve the problem of the topological type of triangulations of general oriented matroids we show in this note that for every circuit admissible triangulation of an arbitrary oriented matroid the $[p_-p_+]$-adjacency graph is a path.
    Keywords: ddc:000
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  • 47
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    Triangulierungen von Punktmengen und Polyedern (2000)
    Details
    Publication Date: 2014-11-10
    Description: Dieser Report wurde im Sommersemester 2000 an der TU Berlin in einer Spezialvorlesung über Triangulierungen von Punktmengen und Polyedern als Skriptum verwendet. Nach einem motivierenden Kapitel werden grundlegende Begriffe und Konstruktionen in der Theorie der Triangulierungen von Punktmengen und Polyedern vorgestellt. Danach werden als weiterführende Themen reguläre Triangulierungen, Sekundärpolytope, bistellare Operationen, höhere Stasheff-Tamari-Halbordnungen und Triangulierungen mit wenigen bzw. gar keinen Flips behandelt. Ein Kapitel über Enumeration und Optimierung beschließt die Zusammenstellung.
    Keywords: ddc:000
    Language: German
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  • 48
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    Optimierung in der Planung und beim Aufbau des G-WiN (2000)
    Details
    Publication Date: 2020-02-11
    Description: Ende Juni diesen Jahres wurde das Gigabit-Wissenschaftsnetz offiziell gestartet. In der zweijährigen Vorbereitungsphase wurden nicht nur die technischen Möglichkeiten der neuen Übertragungstechniken und Dienste getestet. Es wurden auch verschiedene Fragestellungen zum effizienten Einsatz der verfügbaren Ressourcen für den Betrieb des G-WiN untersucht. In diesem Artikel beschreiben wir, wie das G-WiN zu seiner jetzigen Struktur und Topologie gekommen ist.
    Keywords: ddc:000
    Language: German
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  • 49
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    Critical and Anticritical Edges in Perfect Graphs (2000)
    Details
    Publication Date: 2014-02-26
    Description: We call an edge $e$ of a perfect graph $G$ critical if $G-e$ is imperfect and say further that $e$ is anticritical with respect to the complementary graph $\overline G$. We ask in which perfect graphs critical and anticritical edges occur and how to find critical and anticritical edges in perfect graphs. Finally, we study whether we can order the edges of certain perfect graphs such that deleting all the edges yields a sequence of perfect graphs ending up with a stable set.
    Keywords: ddc:000
    Language: English
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  • 50
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    Fast Surface Reconstruction Using a Probe Sphere (2000)
    Details
    Publication Date: 2014-02-26
    Description: We introduce a new method for reconstructing a triangular surface from an unorganized set of points in space. It is based on placing a probe sphere on the point set and rolling it around, connecting all triples of points with a triangle that the sphere comes to rest on. Therefore, the algorithm interpolates, rather than approximates, the input points. The method needs considerably less running time than previous algorithms and yields good results on point sets that are reasonably well-behaved.
    Keywords: ddc:000
    Language: English
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  • 51
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    Frequency Planning and Ramifications of Coloring (2000)
    Details
    Publication Date: 2014-11-11
    Description: This paper surveys frequency assignment problems coming up in planning wireless communication services. It particularly focuses on cellular mobile phone systems such as GSM, a technology that revolutionizes communication. Traditional vertex coloring provides a conceptual framework for the mathematical modeling of many frequency planning problems. This basic form, however, needs various extensions to cover technical and organizational side constraints. Among these ramifications are $T$-coloring and list coloring. To model all the subtleties, the techniques of integer programming have proven to be very useful. The ability to produce good frequency plans in practice is essential for the quality of mobile phone networks. The present algorithmic solution methods employ variants of some of the traditional coloring heuristics as well as more sophisticated machinery from mathematical programming. This paper will also address this issue. Finally, this paper discusses several practical frequency assignment problems in detail, states the associated mathematical models, and also points to public electronic libraries of frequency assignment problems from practice. The associated graphs have up to several thousand nodes and range from rather sparse to almost complete.
    Keywords: ddc:000
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  • 52
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    Hadron masses from dynamical, non-perturbatively O(a) improved Wilson fermions (2000)
    Details
    Publication Date: 2014-02-26
    Description: We present results on light hadron masses from simulations of full QCD and report on experiences in running such simulations on a Hitachi SR8000-F1 supercomputer.
    Keywords: ddc:000
    Language: English
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  • 53
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    Automatic Identification of Metastable Conformations via Self-Organized Neural Networks (2000)
    Details
    Publication Date: 2014-02-26
    Description: As has been shown recently, the identification of metastable chemical conformations leads to a Perron cluster eigenvalue problem for a reversible Markov operator. Naive discretization of this operator would suffer from combinatorial explosion. As a first remedy, a pre-identification of essential degrees of freedom out of the set of torsion angles had been applied up to now. The present paper suggests a different approach based on neural networks: its idea is to discretize the Markov operator via self-organizing (box) maps. The thus obtained box discretization then serves as a prerequisite for the subsequent Perron cluster analysis. Moreover, this approach also permits exploitation of additional structure within embedded simulations. As it turns out, the new method is fully automatic and efficient also in the treatment of biomolecules. This is exemplified by numerical results.
    Keywords: ddc:000
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    An Approximation Algorithm for the Non-Preemptive Capacitated Dial-a-Ride Problem (2000)
    Details
    Publication Date: 2020-11-13
    Description: In the Capacitated Dial-a-Ride Problem (CDARP) we are given a transportation network and a finite set of transportation jobs. Each job specifies the source and target location which are both part of the network. A server which can carry at most $C$~objects at a time can move on the transportation network in order to process the transportation requests. The problem CDARP consists of finding a shortest transportation for the jobs starting and ending at a designated start location. In this paper we are concerned with the restriction of CDARP to graphs which are simple paths. This setting arises for instance when modelling applications in elevator transportation systems. It is known that even for this restricted class of graphs CDARP is NP-hard to solve. We provide a polynomial time approximation algorithm that finds a transportion of length at most thrice the length of the optimal transportation.
    Keywords: ddc:000
    Language: English
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  • 55
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    Affine Invariant Convergence Analysis for Inexact Augmented Lagrangian-SQP Methods (2000)
    Details
    Publication Date: 2019-01-29
    Description: An affine invariant convergence analysis for inexact augmented Lagrangian-SQP methods is presented. The theory is used for the construction of an accuracy matching between iteration errors and truncation errors, which arise from the inexact linear system solves. The theoretical investigations are illustrated numerically by an optimal control problem for the Burgers equation.
    Keywords: ddc:000
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  • 56
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    Online Optimierung (2000)
    Details
    Publication Date: 2020-11-13
    Description: Wie soll man einen Aufzug steuern, wenn man keine Informationen über zukünftige Fahraufträge besitzt? Soll man eine Bahncard kaufen, wenn die nächsten Bahnreisen noch unbekannt sind? In der klassischen kombinatorischen Optimierung geht man davon aus, daß die Daten jeder Probleminstanz vollständig gegeben sind. In vielen Fällen modelliert diese \emph{Offline-Optimierung} jedoch die Situationen aus Anwendungen nur ungenügend. Zahlreiche Problemstellungen in der Praxis sind in natürlicher Weise \emph{online}: Sie erfordern Entscheidungen, die unmittelbar und ohne Wissen zukünftiger Ereignisse getroffen werden müssen. Als ein Standardmittel zur Beurteilung von Online-Algorithmen hat sich die \emph{kompetitive Analyse} durchgesetzt. Dabei vergleicht man den Zielfunktionswert einer vom Online-Algorithmus generierten Lösung mit dem Wert einer optimalen Offline-Lösung. Mit Hilfe der kompetitiven Analyse werden im Skript Algorithmen zum Caching, Netzwerk-Routing, Scheduling und zu Transportaufgaben untersucht. Auch die Schwächen der kompetitiven Analyse werden aufgezeigt und alternative Analysekonzepte vorgestellt. Neben der theoretischen Seite werden auch die Anwendungen der Online-Optimierung in der Praxis, vor allem bei Problemen der innerbetrieblichen Logistik, beleuchtet. Bei der Steuerung automatischer Transportsysteme tritt eine Fülle von Online-Problemen auf. Hierbei werden an die Algorithmen oftmals weitere Anforderungen gestellt. So müssen Entscheidungen unter strikten Zeitbeschränkungen gefällt werden (Echtzeit-Anforderungen). Dieses Skript ist aus dem Online-Teil der Vorlesung -Ausgewählte Kapitel aus der ganzzahligen Optimierung- (Wintersemester~1999/2000) und der Vorlesung -Online Optimierung- (Sommersemester~2000) an der Technischen Universität Berlin entstanden.
    Keywords: ddc:000
    Language: German
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    Portale, Search Engines und Math-Net (2000)
    Details
    Publication Date: 2022-04-11
    Description: Wie sucht ein Wissenschaftler im Internet die ben"otigten Informationen für seine Arbeit? Welche relevanten Informationen gibt es überhaupt im Web? Sind dafür solche Suchmaschinen wie AltaVista, Google oder HotBot die richtigen Werkzeuge? Die Antwort der Mathematiker heisst Math-Net, ein Informations- und Kommunikationssystem für die Mathematik. Math-Net besteht zunächst aus den Informationen von Personen und Institutionen, die ihre für die Mathematik relevanten Informationen dort bereitstellen wollen. Das soll i.a. auf den Web-Servern der Personen oder Institutionen geschehen. Hierin unterscheidet sich die Situation im Math-Net nicht von der im WWW insgesamt. Im Math-Net sollen aber die Informationen in einheitlicher Weise erschlossen werden. Dazu gibt es sowohl für Server als auch für die Dokumente Empfehlungen für deren Strukturierung. Die lokalen Informationen werden dann im Math-Net durch automatische Verfahren gesammelt, ausgewertet und indexiert. Diese Indexe sind die Basis für die Math-Net Dienste. Das sind Search Engines und Portale, die einen qualifizierten und effizienten Zugang zu den Informationen im Math-Net bieten. Die Math-Net Dienste sind auf die Mathematik spezialisiert. Im Gegensatz zu den oben erwähnten universellen Suchmaschinen decken sie nur einen winzigen Bruchteil des Web ab, aber dafür den für die Mathematik relevanten Teil. Math-Net ist mehr als nur Search Engine oder Portal zu Informationen in der Mathematik. Es ist auch ein Informations- und Kommunikationssystem sowie ein Publikationsmedium für die Mathematik. Die mathematische Community hat sich in der Math-Net Initiative organisiert. Diese Initiative wird von der International Mathematical Union (IMU), der weltweiten Dachorganisation der mathematischen Gesellschaften, koordiniert. Die Entwicklung des Math-Net wird von dem breiten Konsens der Mathematiker getragen, den Zugang zu der für die Mathematik relevanten Information zu erleichtern und zu verbessern.
    Keywords: ddc:000
    Language: German
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  • 58
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    A Comparison of Transparent Boundary Conditions for the Fresnel Equation (2000)
    Details
    Publication Date: 2022-07-07
    Description: We establish the relationship between the transparent boundary condition (BPP) of Baskakov and Popov [Wave Motion 14 (1991) 121-128] and Pakpadakis et. al. [J. Acoust. Soc. Am. 92 (1992) 2030-2038] and a second boundary condition (SDY) introduced by Schmidt and Deuflhard [Comp. Math. Appl. 29 (1995) 53-76] and Schmidt and Yevick [J. Compu. Phys. 134 (1997) 96-107], that is explicitly tailored to the form of the underlying numerical propagation scheme. Our analysis demonstrates that if the domain is first discretized in the propagation direction, the SDY expression can be obtained by applying the exact sequence of steps used to derive the BPP procedure. The BPP method is thus an approximate realization of the computationally far simpler and unconditionally stable SDY boundary condition.
    Keywords: ddc:000
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  • 59
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    Discrete Nonreflecting Boundary Conditions for the Helmholtz Equation (2000)
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    Publication Date: 2022-07-07
    Description: We derive exact discrete nonreflecting boundary conditions for time-harmonic scattering problems modeled by the Helmholtz equation. The main idea is to consider the exterior problem as an initial value problem with initial data given on the boundary of the computational domain. The solution of the exterior problem is obtained via Laplace transformation techniques which supply the boundary conditions in terms of discrete Dirichlet-to-Neumann operators.
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    Adaptive Multigrid Methods for the Vectorial Maxwell Eigenvalue Problem for Optical Waveguide Design (2000)
    Details
    Publication Date: 2022-07-07
    Description: This paper has been motivated by the need for a fast robust adaptive multigrid method to solve the vectorial Maxwell eigenvalue problem arising from the design of optical chips. Our nonlinear multigrid methods are based on a previous method for the scalar Helmholtz equation, which must be modified to cope with the null space of the Maxwell operator due to the divergence condition. We present two different approaches. First, we present a multigrid algorithm based on an edge element discretization of time-harmonic Maxwell's equations, including the divergence condition. Second, an explicit elimination of longitudinal magnetic components leads to a nodal discretization known to avoid discrete \emph{spurious modes} also and a vectorial eigenvalue problem, for which we present a multigrid solver. Numerical examples show that the edge element discretization clearly outperforms the nodal element approach.
    Keywords: ddc:000
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  • 61
    Electronic Resource
    Electronic Resource
    Imaging of plant-thorn synovitis (2000)
    Springer
    Skeletal radiology 29 (2000), S. 605-608 
    Details
    ISSN: 1432-2161
    Keywords: Keywords Plant-thorn synovitis ; Monoarticular arthritis ; Elbow ; Magnetic resonance imaging ; Ultrasound ; Power Doppler
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  We describe a case of plant-thorn synovitis of the elbow resulting from a thorn injury. This caused recurrent pain and swelling of the elbow over a 3-month period. A magnetic resonance imaging examination was initially requested to exclude septic arthritis, and demonstrated a joint effusion, synovitis, and a 2-cm linear opacity embedded in the synovium. Ultrasound was performed prior to surgery to confirm these findings and provide accurate localization of the thorn fragment, later removed at surgery. To our knowledge this is the first example of this condition that has been confirmed by radiological imaging prior to surgery.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002560000244
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  • 62
    Electronic Resource
    Electronic Resource
    Are magnetic resonance flexion views useful in evaluating the cervical spine of patients with rheumatoid arthritis? (2000)
    Springer
    Skeletal radiology 29 (2000), S. 85-89 
    Details
    ISSN: 1432-2161
    Keywords: Key words Rheumatoid arthritis ; Cervical spine ; Magnetic resonance imaging ; Dynamic imaging ; Flexion views
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Objective. To determine whether MR imaging in flexion adds value relative to imaging in the neutral position with respect to displaying involvement of the subarachnoid space, brainstem and spinal cord. Design and patients. T1-weighted MR images of the cervical spine in 42 rheumatoid arthritis patients with cervical spine involvement were obtained and analyzed prospectively. We assessed changes between images obtained in the neutral position and following active flexion, especially horizontal atlantoaxial and subaxial motion, presence or absence of brainstem compression, subarachnoid space involvement at the atlantoaxial and subaxial level and the cervicomedullary angle. Vertical atlantoaxial subluxation and the amount of pannus were correlated with motion and change in subarachnoid space. Results. The flexion images showed horizontal atlantoaxial motion in 21 patients and subaxial motion in one patient. The flexion view displayed brainstem compression in only one patient. Involvement of the subarachnoid space increased at the atlantoaxial level in eight (19%) patients (P=0.004) and at the level below C2 in five (12%) patients (P=0.03). There were no patients with a normal subarachnoid space in neutral position and compression in the flexed position. The cervicomedullary angle changed significantly with flexion. Vertical atlantoaxial subluxation and the amount of pannus did not show a significant correlation with motion or subarachnoid space involvement. Conclusion. MR imaging in the flexed position shows a statistically significant narrowing of the subarachnoid space at the atlantoaxial level and below C2. Cord compression is only observed on flexion views if the subarachnoid space in neutral position is already decreased. MR imaging in the flexed position might be useful, since subarachnoid space involvement may be an indicator for the development of neurologic dysfunction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002560050015
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  • 63
    Electronic Resource
    Electronic Resource
    Intra-articular membranous interposition detected by MRI in developmental dysplasia of the hip (2000)
    Springer
    Skeletal radiology 29 (2000), S. 726-728 
    Details
    ISSN: 1432-2161
    Keywords: Keywords Developmental dysplasia ; Hip ; Membrane ; Interposition ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Intra-articular membranous interposition was detected by MRI in the hip joint with residual subluxation of a girl aged 5 years 10 months. This structure, which had low signal intensity on both T1- and T2-weighted images, separated the femoral head from the acetabulum. Histological examination revealed chondrometaplasia, which suggested that this interposition might be transformed to a surface cartilaginous tissue of the secondary acetabulum often observed in residual subluxation of the hip.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002560000293
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  • 64
    Electronic Resource
    Electronic Resource
    Dumb-bell-type teratoma in the lumbar spine (2000)
    Springer
    Skeletal radiology 29 (2000), S. 104-108 
    Details
    ISSN: 1432-2161
    Keywords: Key words Adult teratoma ; Dumb-bell type tumor ; Lumbar spine ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  We report a case of a lumbar teratoma in a 50-year-old woman. The teratoma showed a dumb-bell-type expansion at the level of the left L3/4 foramen with massive erosion of the L3 vertebral body. MRI revealed inhomogeneous signal changes in the tumor, which were histologically compatible with a mixture of bone, muscle, fat, and cyst containing sebaceous material. Complete resection of the tumor and spinal arthrodesis with pedicle screw fixation was necessary to obtain stability of the affected spinal segment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002560050020
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  • 65
    Electronic Resource
    Electronic Resource
    Effect of low back posture on the morphology of the spinal canal (2000)
    Springer
    Skeletal radiology 29 (2000), S. 217-223 
    Details
    ISSN: 1432-2161
    Keywords: Key words Spinal canal ; Low back posture ; Morphologic change ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Objective. To define the possible mechanism of posture-dependent symptoms of spinal stenosis by measuring the effect of low back posture on morphologic changes of the intervertebral discs and spinal canal in healthy young people. Design.Twenty healthy young volunteers underwent magnetic resonance imaging while supine with their spine in neutral, flexed, extended, and right and left rotational positions. The axial MR images at the middle of the intervertebral discs of L3–4 and L4–5 were analyzed to measure the difference in the size and shape of the intervertebral discs and spinal canal in each posture. Results.  Extension or rotation decreased the sagittal diameters and cross-sectional areas of the dural sac and spinal canal and increased the thickness of the ligamentum flavum, whereas flexion had the opposite effects. The gap between the convex posterior disc margin and the anterior margin of the facet joint on each side, represented as the subarticular sagittal diameter, increased with flexion and decreased with extension or rotation. The direction of rotation did not result in asymmetry of the subarticular sagittal diameter, but right rotation caused thickening of the right ligamentum flavum, and vice versa. The shape and dimensions of the disc did not change significantly according to the positions of the low back. Conclusions.With extension or rotation, the thickness of the ligamentum flavum increased and the posterior margin of the intervertebral disc was approximated to the facet joint without any change in shape and size of the disc. These phenomena result in a decrease in the size of the spinal canal and dural sac in extension or rotation postures in young healthy people without disc degeneration, and may explain the posture-dependent symptom of spinal stenosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002560050596
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  • 66
    Electronic Resource
    Electronic Resource
    Complete rupture of the distal semimembranosus tendon with secondary hamstring muscles atrophy: MR findings in two cases (2000)
    Springer
    Skeletal radiology 29 (2000), S. 362-364 
    Details
    ISSN: 1432-2161
    Keywords: Key words Hamstring muscles ; Semimenbranosus ; Tear ; mass ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Complete rupture of the hamstring muscles is a rare injury. The proximal musculo-tendinous junction is the most frequent site of rupture. We present two cases of complete rupture of the distal semimenbranosus tendon, which clinically presented as soft-tissue masses. MR imaging permitted the correct diagnosis. There has been only one other such case reported.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002560000216
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    Solid aneurysmal bone cyst in the humerus (2000)
    Springer
    Skeletal radiology 29 (2000), S. 470-473 
    Details
    ISSN: 1432-2161
    Keywords: Key words Aneurysmal bone cyst ; Humerus ; Giant cell reparative granuloma ; Pathological fracture ; Radiography ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  We report on a 69-year-old woman with a solid variant of aneurysmal bone cyst (solid ABC) in the left humerus with a pathological fracture. Radiographically, the lesion exhibited a relatively well-defined osteolytic lesion in the diaphysis of the left humerus. On magnetic resonance (MR) imaging, the medullary lesion exhibited a homogeneous signal intensity isointense with surrounding normal muscles on the T1-weighted images and a mixture of low and high signal intensity on the T2-weighted images. Contrast-enhanced T1-weighted images revealed diffuse enhancement of the entire lesion. The pathological study showed a proliferation of fibroblasts, histiocytes, chronic inflammatory cells and numerous multinucleated giant cells in a collagenous matrix. Abundant osteoid formation in the matrix was observed, but the cells were devoid of nuclear atypia. Aneurysmal cystic cavities were absent. A review of the English literature found 22 cases of solid ABC of the long bones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002560000236
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    Juxta-articular hemangioma of long bone (2000)
    Springer
    Skeletal radiology 29 (2000), S. 535-537 
    Details
    ISSN: 1432-2161
    Keywords: Key words Computed tomography ; Intraosseous hemangioma ; Magnetic resonance imaging ; Epiphysis equivalent ; Tibia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  We report on a rare case of an intraosseous hemangioma involving the proximal tibia in a 70-year-old man. Radiographically, the lesion was a well-defined osteolytic lesion with marginal sclerosis. The CT images demonstrated a well-defined osteolytic lesion with partial cortical breakthrough. T1-weighted MR images showed a hypointense lesion, while T2-weighted images revealed hyperintense areas, with internal, hypointense septa. Gadolinium-enhanced T1-weighted images showed lattice-like enhancement of the lesion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002560000256
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  • 69
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    Pectoralis major muscle and tendon tears: diagnosis and grading using magnetic resonance imaging (2000)
    Springer
    Skeletal radiology 29 (2000), S. 305-313 
    Details
    ISSN: 1432-2161
    Keywords: Key words Pectoralis major muscle ; Magnetic resonance imaging ; Tendons ; injuries ; Tendons ; magnetic resonance imaging ; Muscles ; injuries ; Muscles ; magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Objective. To assess the accuracy and utility of magnetic resonance (MR) imaging in the detection and grading of pectoralis major muscle and tendon tears. Design and patients. A retrospective review was carried out of 10 patients referred for MR imaging for suspected pectoralis muscle injury and possible operative therapy. The pectoralis muscle and tendon were imaged using thin (3–4 mm) axial sections with a variety of sequences combined for anatomical delineation (T1-weighted SE or PD SE) and fluid detection (T2-weighted SE, T2-weighted FSE with fat suppression, or STIR). Surgical correlation was available in six patients. Clinical follow-up was available in four patients treated by nonoperative therapy. Results. MR imaging identified five complete tears, four partial tears and one normal tendon. One complete and one partial tear were at the myotendinous junction. The remaining seven injuries were at the enthesis. Surgical correlation consisted of five complete tears and one partial tear. One complete and one partial tear were at the myotendinous junction with the remaining four complete tears at the enthesis. The MR interpretation and surgical findings were in agreement in all six cases. All four patients treated with nonoperative therapy demonstrated improvement at a clinical follow-up examination, with restoration of function and strength consistent with a healed prior partial injury. Conclusion. MR imaging is accurate and useful in detecting and grading tears involving the pectoralis major muscle and tendon, facilitating the identification of patients with complete tears who are candidates for operative therapy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002560000199
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    Imaging in isolated sacral tuberculosis: a review of 15 cases (2000)
    Springer
    Skeletal radiology 29 (2000), S. 392-396 
    Details
    ISSN: 1432-2161
    Keywords: Key words Sacral ; Tuberculosis ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Objective. To review imaging studies of isolated involvement of the sacrum due to tuberculosis and determine the role of imaging in the diagnosis and management of these patients. Design and patients. A retrospective analysis of 15 cases of isolated sacral tuberculosis imaged with MR imaging was performed. The CT images were also reviewed where available, and the various lesion characteristics were identified. We also reviewed the medical records in an attempt to determine the impact of the imaging studies on the management of these patients. Results. Fifteen patients (5 male, 10 female) presented with symptoms of 3–15 months’ duration. Chronic localized backache with muscle spasm was the commonest presenting symptom; discharging sinuses with abscess formation was found in six patients, five of whom were children. MR imaging of the sacrum revealed a hypointense marrow signal on T1-weighted images and hyperintense signal on T2-weighted images in 14 of 15 patients, the S2 vertebra being always involved. CT revealed osteolytic changes in the sacrum in all the five patients in whom CT was performed. All patients showed marked clinical improvement within 1 year of anti-tuberculous chemotherapy. Conclusion. Isolated tuberculosis of the sacrum is uncommon but should be suspected in patients presenting with chronic low backache or children with discharging sinuses/abscesses and showing sacral destruction on CT or MR imaging. MR imaging can identify cases and enables early institution of anti- tuberculous chemotherapy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002560000229
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    Subcutaneous and musculoskeletal sparganosis: imaging characteristics and pathologic correlation (2000)
    Springer
    Skeletal radiology 29 (2000), S. 402-408 
    Details
    ISSN: 1432-2161
    Keywords: Key words Soft tissue ; Magnetic resonance imaging ; Sparganosis ; Sparganosis ; magnetic resonance imaging ; Sparganosis ; ultrasonography ; Parasitic infection ; Sparganum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Objective. To document the imaging characteristics of subcutaneous and musculoskeletal sparganosis. Design and patients. Ten patients with musculoskeletal sparganosis were examined, with a variety of imaging modalities including MRI (n=6), ultrasonography (n=8), plain radiography (n=7) and CT (n=1). Pathologic correlation was carried out in all cases. Results. Nine lesions involved soft tissues, of which seven were in the thigh, two in the trunk and one involved a vertebral body. The majority of the lesions in soft tissue were confined to the subcutaneous layer but two extended deep into underlying muscles. Sonography revealed low-echoic serpiginous tubular tracts (8/8), and an intraluminal echogenic structure (4/8). MRI revealed multiple serpiginous tubular tracts and peripheral rim enhancement. Two patients showed perilesional soft tissue edema. Pathologically, the lesion consisted of a larva surrounded by three layers of inflammation: an inner epithelioid granulomatous cell layer, middle chronic inflammatory cell layers, and an outer fibrous layer. Conclusion. The study suggests that if serpiginous tubular tracts are seen at imaging studies, musculoskeletal sparganosis should be included in the differential diagnosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002560000206
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  • 72
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    Juxtacortical chondromyxoid fibroma arising in an apophysis (2000)
    Springer
    Skeletal radiology 29 (2000), S. 466-469 
    Details
    ISSN: 1432-2161
    Keywords: Key words Bone neoplasm ; Chondromyxoid fibroma ; Femur ; Apophysis ; Radiography ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  We present a rare case of juxtacortical chondromyxoid fibroma arising in the lesser trochanter of the right femur which corresponds to an apophysis. Radiography showed a well-defined expansive lesion with a sclerotic margin measuring 5×3.5 cm in diameter in the lesser trochanter. On spin echo T1-weighted images, the lesion revealed low signal intensity similar to muscle. On spin echo T2-weighted images, the lesion revealed high heterogeneous signal intensity, which after gadolinium injection showed heterogeneous enhancement. The inner margin of the cortex was intact and adjacent bone marrow was of normal signal intensity. The outer margin of the lesion was also clearly defined and extension into adjacent soft tissue beyond the exophytic cortical outgrowth was not evident.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002560000245
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  • 73
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    Sonographie des Gehirns und Rückenmarks bei Früh- und Neugeborenen (2000)
    Springer
    Der Radiologe 40 (2000), S. 35-42 
    Details
    ISSN: 1432-2102
    Keywords: Schlüsselwörter ; Neugeborenes ; Frühgeborenes ; Ultraschall ; Gehirn ; Rückenmark ; Key words ; Premature infant ; Newborn ; Sonography ; Brain ; Spinal cord
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Examination of the central nervous system in premature and full-term infants requires a sensible selection of the available diagnostic procedures such as ultrasound, MRI and CT to allow sufficient and accurate diagnosis and management. Ultrasound: Ultrasound, including the various Doppler techniques, is a very reliable, safe, noninvasive diagnostic tool that allows evaluation of even severely ill patients in intensive care units. It is especially well suited for the study of intracranial hemorrhage, hypoxic-ischemic encephalopathy, congenital malformations of the brain and lesions produced by intrauterine and acquired infections. Sonography is also very reliable in examination of spinal dysraphism and spinal cord injuries during birth. The necessity of surgical intervention (i.e. shunt implantation) as well as subsequent postoperative follow-up can be provided. MRI: In contrast to ultrasound, MRI is most useful to demonstrate the age-dependent myelinization pattern and clearly discriminates between the white and gray matter of the central nervous system. We therefore use MRI for the detection of complex malformations of the central nervous system in particular disorders of cell migration and for a final estimation of a perinatal brain injury. Conclusion: A precise ultrasound examination performed by an experienced physician who is familiar with the expected pathology and has access to a well-adjusted ultrasound machine should help to minimize the use of confirming CT and MRI investigations and to optimize their optional use in more complex cases.
    Notes: Zusammenfassung Zur Untersuchung des Gehirns und Rückenmarks von Früh- und Neugeborenen müssen die zur Verfügung stehenden Bildmodalitäten – Ultraschall, MR, CT – gemäß ihrer Aussagekraft in Bezug auf klinische Fragestellung und therapeutische Konsequenz angewendet werden. Ultraschall: Der Ultraschall einschließlich der verschiedenen Dopplertechniken ermöglicht ohne Sedierung die rasche, risikoarme und sehr zuverlässige Untersuchung auch schwerkranker Kinder auf der Intensivstation. Es gilt, die Hirnblutungen, die hypoxisch-ischämischen Hirnschädigungen und ihre Folgen, Hirnmissbildungen, Folgen kongenitaler und postnatal erworbener Infektionen, die Dysrhaphien des Rückenmarks und die geburtstraumatischen Rückenmarkschädigungen nachzuweisen oder auszuschließen, die Indikation zu chirurgischen Interventionen (z.B. Drainage eines Hydrozephalus) zu stellen und deren Erfolg zu beurteilen. Für den frühen Nachweis hypoxisch-ischämischer Schädigungen ist der Ultraschall wenig sensitiv. MRT: Da das MR im Gegensatz zum Ultraschall die altersabhängige Myelinisierung zeigt und die Unterscheidung zwischen grauer und weißer Substanz ermöglicht, nützen wir diese anatomische Auflösung bei der Untersuchung von sowohl sehr komplexen Hirnfehlbildungen als auch solchen, die mit Migrationsstörungen einhergehen, und gelegentlich für die abschließende Beurteilung des Ausmaßes einer perinatalen Hirnschädigung. Schlussfolgerung: Nach einer sorgfältig durchgeführten Ultraschalluntersuchung durch einen mit der zu erwartenden Pathologie vertrauten Untersucher mit einem hochauflösenden Ultraschallgerät sollten CT- und MR-Untersuchungen nur zur Bestätigung des Ultraschallbefunds überflüssig sein, zu deren evtl. notwendiger Ergänzung jedoch optimiert erfolgen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001170050006
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    Harntransportstörungen bei Neugeborenen (2000)
    Springer
    Der Radiologe 40 (2000), S. 72-77 
    Details
    ISSN: 1432-2102
    Keywords: Schlüsselwörter ; Kongenitale Anomalien der Nieren ; Neonatale Hydronephrosen ; Ultraschall in der Neonatalperiode ; Key words ; Congenital anomalies of the kidneys ; Neonatal hydronephrosis ; Neonatal ultrasound
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Malformations of the urinary tract are one of the most common types of anomalies in the neonatal period. Approximately 15–20% of all prenatally detected malformations require acute postnatal imaging. Sonography is the primary imaging modality in the evaluation of nephro-urologic problems in infancy. Hydronephrosis represents the most common pathology, followed by multicystic-dysplastic kidney. Discussion: The result of the sonographic examination directs further imaging. An adequate diagnostic algorithm is decisive for accurate diagnosis, for the appropriate therapeutic regimen and for the prognosis of the patients.
    Notes: Zusammenfassung Fehlbildungen der Nieren und der ableitenden Harnwege zählen zu den häufigsten kongenitalen Anomalien in der Neugeborenenperiode. Etwa 15–20% aller pränatal diagnostizierten Fehlbildungen erfordern eine akute postnatale Diagnostik. Die Sonographie ist das initiale bildgebende Verfahren der Wahl in der Abklärung nephrourologischer Fragestellungen im Kindesalter. Hydronephrosen stellen die häufigsten Pathologien dar, die multizystisch-dysplastische Niere steht an 2. Stelle. Diskussion: Das Ergebnis der Sonographie ist richtungsweisend für die Wahl der weiteren bildgebenden Verfahren. Der adäquate diagnostische Algorithmus ist entscheidend für die richtige Diagnose, das geeignete therapeutische Prozedere und letztendlich für die Prognose der Patienten.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001170050011
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  • 75
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    MR-Angiographie der supraaortalen Gefäße (2000)
    Springer
    Der Radiologe 40 (2000), S. 785-791 
    Details
    ISSN: 1432-2102
    Keywords: Schlüsselwörter Zerebrovaskuläre Erkrankung ; Arteriosklerose ; Magnetresonanztomographie ; Magnetresonanzangiographie ; Digitale Subtraktionsangiographie ; A. carotis ; Keywords Cerebrovascular disease ; Arteriosclerosis ; Magnetic resonance imaging ; Magnetic resonance angiography ; Digital subtraction angiography ; Carotid artery
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Abstract Purpose. To compare high resolution contrast-enhanced MR angiography (MRA) and digital subtraction angiography (DSA) in the assessment of supraaortic vessel stenosis. Methods. 14 patients with suspicion of cerebrovascular disease or upper limb ischemia underwent selective DSA and high resolution contrast enhanced MRA employing a new Panoramic-Array coil. Stenosis assessment in comparison to DSA followed NASCET criteria. Additionally signal-/noise ratios (SNR) were evaluated to assess contrast enhancement. Results. Diagnostic image quality was achieved in all patients. Sensitivity and specificity for assessing high-grade stenosis of the supraaortic vessels were 100% and 96% respectively. In the assessment of high-grade common or internal carotid artery stenosis sensitivity and specificity was 100%. Conclusion. High resolution contrast enhanced supraaortic MRA combined with new coil sytems allow for a reliable assessment of stenoses along the whole vessel course including the aortic arch. Previous stent procedures limit its use in post-interventional follow-up.
    Notes: Zusammenfassung Fragestellung. Ziel der Studie war ein Vergleich zwischen hochauflösender kontrastverstärkter MR-Angiographie (MRA) und digitaler Subtraktionsangiographie (DSA) in der Diagnostik von Stenosen der supraaortalen Gefäße. Methoden. 14 Patienten mit Verdacht auf eine zerebrovaskuläre Erkrankung oder Durchblutungsstörung der oberen Extremität wurden mit DSA und hochaufgelöster, kontrastverstärkter MR-Angiographie mit Verwendung einer Panoramic-Array-Spule untersucht. Neben der Beurteilung der Kontrastierung erfolgte die Bestimmung der Stenosegrade im Vergleich zur selektiven DSA nach den NASCET-Kriterien. Ergebnisse. Bei allen Patienten konnte mit der MRA eine diagnostisch ausreichende Bildqualität erzielt werden. In der Diagnostik hochgradiger Stenosen der supraaortalen Gefäße ergab sich eine Sensitivität von 100% und eine Spezifität von 96%. In der Erkennung hochgradiger Stenosen der A. carotis communis oder interna lagen Sensitivität und Spezifität bei 100%. Schlussfolgerung. Die ultraschnelle MRA der supraaortalen Gefäße in Kombination mit einer geeigneten Spulenkombination ermöglicht die zuverlässige Erkennung stenotischer Veränderungen im gesamten Gefäßverlauf einschließlich des Aortenbogens. Stentimplanationen limitieren derzeit den Einsatz in der postinterventionellen Kontrolle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001170050824
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  • 76
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    Diffusionsgewichtete Magnetresonanztomographie in der Diagnostik der Encephalitis disseminata (2000)
    Springer
    Der Radiologe 40 (2000), S. 1057-1063 
    Details
    ISSN: 1432-2102
    Keywords: Schlüsselwörter Diffusion ; Magnetresonanztomographie ; Encephalitis disseminata ; Keywords Diffusion ; Magnetic resonance imaging ; Multiple sclerosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Abstract Magnetic resonance (MR) imaging is one of the best methods in diagnosis of multiple sclerosis, particularly in disclosure of active demyelinating lesions. Aim of this study was to compare diffusion weighted imaging and contrast enhancement in the detection of active lesions. A MR study with a contrast enhanced T1-weighted pulse sequence with magnetization transfer presaturation and a diffusion weighted echoplanar pulse sequence (b=1000 s/mm2) was performed in 17 patients (11 women, 6 men) with multiple sclerosis. 29 of 239 lesions showed an increased signal intensity in diffusion weighted imaging, 24 lesions a contrast enhancement, but only 16 lesions were visible in both pulse sequences. In patients with short clinical symptomatology significant more lesions could be detected with diffusion-weighted pulse sequence in comparison to patients with long standing symptomatology showing more lesions with contrast enhancement. Hence it is likely, that both pulse sequences detect different histopathologic changes. The early detection of demyelinating lesions in diffusion weighted imaging is attributed to the extracellular edema, however the contrast enhancement is caused by a blood brain barrier abnormality. It can be expected that diffusion weighted imaging will have a high impact on imaging of multiple sclerosis not only in therapeutic trials, but also in clinical routine.
    Notes: Zusammenfassung Die Magnetresonanztomograpie ist eine der wichtigsten Untersuchungsmethoden in der Diagnostik der Encephalitis disseminata, insbesondere im Nachweis aktiver Entmarkungsherde. Ziel der Untersuchung war es, diffusionsgewichtete und kontrastverstärkte Untersuchungen bezüglich der Erkennung aktiver Läsionen zu vergleichen. Bei 17 Patienten (11 Frauen, 6 Männer) mit bekannter Encephalitis disseminata wurden sowohl eine kontrastverstärkte T1-gewichtete Sequenz mit Magnetization-Transfer-Sättigung als auch eine diffusionsgewichtete Echoplanar-Sequenz (b=1000 s/mm2) durchgeführt. 29 der 239 Läsionen zeigten eine Signalsteigerung in der diffusionsgewichteten Sequenz, 24 eine Kontrastmittelaufnahme, jedoch waren nur 16 Läsionen in beiden Techniken nachweisbar. Bei Patienten mit kurzzeitig bestehender Symptomatik zeigten sich signifikant mehr Entmarkungsherde mit Signalsteigerung in der Diffusionswichtung im Vergleich zu Patienten mit länger bestehender neurologischer Symptomatik, die mehr kontrastmittelaffine Läsionen aufwiesen. Dies lässt darauf schließen, dass mit beiden Verfahren unterschiedliche histopathologische Veränderungen beobachtet werden. Das sehr frühe Auftreten der Diffusionsänderung in den Entmarkungsherden wird auf das Ödem zurückgeführt, während die Kontrastmittelaufnahme durch eine Blut-Hirnschranken-Störung verursacht wird. Es ist zu erwarten, dass die diffusionsgewichtete Magnetresonanztomographie einen hohen Stellenwert in der Bildgebung der Encephalitis disseminata nicht nur in Therapiestudien, sondern auch in der klinischen Routinediagnostik erlangen wird.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001170050878
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    Optimierung der Zeitauflösung in der CT mittels retrospektivem EKG-Gating (2000)
    Springer
    Der Radiologe 40 (2000), S. 123-129 
    Details
    ISSN: 1432-2102
    Keywords: Schlüsselwörter ; Spiral-CT ; Herz ; Retrospektives Gating ; Zeitauflösung ; Key words ; Spiral CT ; Heart imaging ; Retrospective gating ; Temporal resolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Purpose: Spiral CT of the heart using the established ways of ECG synchronization is hampered by the relatively long acquisition times of 250 to 500 ms. This only allows to acquire diastolic images in patients with moderate heart rates. In this work, algorithms for time-optimized retrospective cardiac gating are presented, and their potential to improve temporal resolution is investigated. Material and methods: These algorithms use data from multiple gantry rotations for image reconstruction, which is possible for multi-scans at fixed slice positions as well as for overlapping spiral scans. Temporal resolution was quantified using computer simulations and compared to experimental data from pigs. Results: Using a conventional sub-second CT scanner, considerably higher temporal resolutions are possible with spiral scanning. A temporal resolution of 170 ms already provides systolic images with little motion artifacts. Higher temporal resolutions of up to 70 ms are demonstrated for multi-scans, which allows to depict ventricle wall movement over the complete cardiac cycle. Discussion: The method of time-optimized retrospective cardiac gating broadens the spectrum of conventional spiral-CT for cardiac imaging. It can be directly transferred to multi-slice scanners. Here it can be used clinically because of reduced scan time. Potential applications are the determination of functional cardiac parameters like ejection fraction and the detection of disorders of ventricle wall movement.
    Notes: Zusammenfassung Zielsetzung: Die Spiral-CT des Herzens ist mit bisherigen Verfahren zur EKG-Synchronisation nur eingeschränkt möglich. Die Aufnahmezeit von ca. 250 bis 500 ms ermöglicht nur diastolische Aufnahmen bei Patienten mit moderater Herzfrequenz. In dieser Arbeit wurden Algorithmen zum zeitoptimierten retrospektiven EKG-Gating entwickelt und untersucht, wie höhere Zeitauflösungen erreicht werden können. Material und Methode: Das Prinzip der Algorithmen ist es, Daten von mehreren Gantry-Umläufen für die Bildrekonstruktion heranzuziehen. Dies ist sowohl in einzelnen Schichten als auch bei Spiralscans mit überlappenden Aufnahmeschichten möglich. Die Zeitauflösung wurde durch Computersimulationen für verschiedene Aufnahmeparameter bestimmt und mit Experimenten an Schweinen verglichen. Ergebnisse: Es zeigt sich, dass mit einem Standard-Subsekunden-CT-Scanner mit überlappenden Spiralen deutlich höhere Zeitauflösungen möglich sind, bereits 170 ms ermöglichen eine Darstellung der Systole mit nur minimalen Bewegungsartefakten. An einzelnen Schichten wurden Zeitauflösungen von bis zu 70 ms demonstriert, womit die Herzwandbewegung über den kompletten Herzzyklus dargestellt werden kann. Diskussion: Die Methode des zeitoptimierten retrospektiven EKG-Gating erweitert die Einsatzmöglichkeiten herkömmlicher Spiral-CTs für die Bildgebung des Herzens. Sie lässt sich direkt auf Multizeilen-CTs übertragen, wo sie wegen der Reduktion der Untersuchungszeit klinisch eingesetzt werden kann. Mögliche Anwendungen sind die Bestimmung von funktionellen Herzparametern wie Ejektionsfraktion und die Detektion von Wandbewegungsstörungen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001170050020
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    Flussquantifizierung in Koronar- und Bypass- gefäßen mit der MR-Phasenkontrasttechnik (2000)
    Springer
    Der Radiologe 40 (2000), S. 143-149 
    Details
    ISSN: 1432-2102
    Keywords: Schlüsselwörter ; Magnetresonanztomographie ; Flussmessung ; Koronararterie ; Koronare Bypassgefäße ; Key words ; MR imaging ; Flow quantification ; Coronary artery ; Coronary bypass grafts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Purpose: To evaluate accuracy of velocity encoded cine MR imaging for determination of blood flow in coronary arteries and coronary bypass grafts. Materials and methods: 12 patients with 22 coronary bypass grafts underwent intraoperative flow quantification using the transit time ultrasound method. These values were compared to postoperative MR phase shift measurements. Flow measurements were performed preoperatively in 28 coronary arteries of 20 patients. For flow measurement, we used a velocity-encoded k-space segmented gradient echo sequence with a temporal resolution of 110 or 125 ms, respectively. 6–8 pase shift images could be acquired during one cardiac cycle. Results: There was a significant correlation between intraoperative and flow measurements using velocity-encoded MR imaging (r=0.74, p〈0.0001, t-test). Flow volumes determined by MR imaging were systemati-cally larger than those determined by the transit time ultrasound method. Mean flow in coronary arteries was reduced in severly stenosed vessels (〉70%) compared to normal vessels. Intra- and interobserver vari-ability were 10.5 and 15% (coronary bypass grafts), and 12.3 and 15.8% (coronary ar- teries), respectively. Conclusions: Velocity-encoded MR imaging enables determination of flow in coronary artery bypass grafts and coronary arteries. Future developments should aim at the improvement of spatial and temporal resolution of the method.
    Notes: Zusammenfassung Ziel: Es sollte die Genauigkeit der MR-Phasenkontrastmethode zur Ermittlung des Flusses in Koronararterien und koronaren Bypassgefäßen bestimmt werden. Material und Methode: Die MRT-Flussmessungen von 12 Patienten mit 22 Bypassgefäßen wurden mit intraoperativ mittels Ultraschalldurchflussmethode bestimmten Flüssen verglichen. Präoperativ wurden zusätzlich Flussmessungen in 28 Koronararterien von 20 Patienten durchgeführt. Zur MRT-Flussmessung wurde eine segmentierte 2D-Flash-Sequenz verwendet, die eine zeitliche Auflösung von 110 bzw. 125 ms aufwies. Dies ermöglichte die Akquisition von 6–8 Bildpaaren pro Herzzyklus. Ergebnisse: Es bestand eine signifikante Korrelation zwischen den Ergebnissen der intraoperativen und denen der postoperativen MRT-Flussmessung (r=0,76, p〈0,0001, t-Test). Das mit der MRT gemessene Flussvolumen lag über dem bei der Ultraschallmessung ermittelten. Die Bestimmung des mittleren Flusses in den Koronararterien zeigte deutliche Unterschiede zwischen Gefäßen mit höhergradiger Stenose (〉70%) und Gefäßen ohne Stenose. Die Intra- und Interbeobachtervariabilitäten betrugen 10,5 und 15% (Bypass) bzw. 12,3 und 15,8% (Koronararterien). Schlussfolgerungen: Die Phasenkontrastmethode ermöglicht – in Kenntnis ihrer Limitationen – eine relativ genaue Bestimmung des Blutflusses in Koronararterien und koronaren Bypassgefäßen. Weiterentwicklungen der Methode müssen eine verbesserte räumliche und zeitliche Auflösung zum Ziel haben.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001170050023
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    Electronic Resource
    Brustkrebsfrüherkennung in Deutschland (2000)
    Springer
    Der Radiologe 40 (2000), S. 177-183 
    Details
    ISSN: 1432-2102
    Keywords: Schlüsselwörter ; Mammakarzinom ; Früherkennung ; Qualitätssicherung ; Key words ; Breast cancer ; Screening ; Quality assessment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary In Germany there is still an urgent need for action in regard to screening for breast cancer. The announcement of research projects for mammography screening proves this. The following reports the results of the Munich field study. In 2 years, 2489 breast cancer cases were registered (status 6/98). Screening data were available for 1319 patients. The reduction in mortality, found in randomized studies, due to mammography in women over 50 years old was confirmed. A relative reduction of 44.8% in 10-year mortality could be estimated through mammography and 25.1% through palpation, in comparison with ”doing nothing”. We could also estimate the participation of screening and the used methods in the Munich region. If the mammographies carried out today were used at 2-year intervals for women aged between 50 and 70 years, then the mammography screening could be performed with no additional costs for 70% of the women. The known facts regarding the population-based mortality and regarding the acceptance of the palpation screening and frequency of mammography are additional aspects for inclusion in the discussion of what research projects in Germany are and what they should fulfill.
    Notes: Zusammenfassung Hintergrund: Bei der Früherkennung des Mammakarzinoms besteht in Deutschland nach wie vor ein dringender Handlungsbedarf. Die Ausschreibung von Modellprojekten zur Einführung des Mammographiescreenings belegt dies. Im folgenden wird – als Diskussionsgrundlage –über erste Ergebnisse der Feldstudie München berichtet. Ergebnisse: In einem Zeitraum von 2 Jahren wurden 2489 Mammakarzinome registriert (Stand Juni 1998). Zu 1319 Patientinnen sind Angaben zur Früherkennung verfügbar. Die durch randomisierte Studien gesicherte Senkung der Mortalität durch die Mammographie im Alter 〉50 Jahre konnte bestätigt werden. Aufgrund der dokumentierten Stadienverteilung beträgt die Schätzung für die relative Senkung der 10-Jahres-Mortalität durch die Mammographie 44,8% und durch die Palpation 25,1% im Vergleich zum „Nichtstun”. Auch die Inanspruchnahme der Früherkennung und die in der Region München eingesetzten Methoden konnten abgeschätzt werden. Schlussfolgerungen: Würden die heute durchgeführten Mammographien bei Frauen im Alter zwischen 50 und 70 Jahren mit einem Abstand von 2 Jahren eingesetzt, so könnte das Mammographiescreening bei etwa 82% der Frauen kostenneutral durchgeführt werden. Die bekannten Fakten zur Mortalität und zur bundesweiten Inanspruchnahme des heutigen Früherkennungsangebots sind weitere Grundlagen für die Diskussion, was Modellprojekte in Deutschland sein und was sie wann leisten sollten.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001170050029
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  • 80
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    Electronic Resource
    Akutbehandlung des episodischen kindlichen Spannungskopfschmerzes mit Flupirtin und Paracetamol (2000)
    Springer
    Der Schmerz 14 (2000), S. 1-4 
    Details
    ISSN: 1432-2129
    Keywords: Schlüsselwörter ; Kopfschmerz ; Kinder ; Akuttherapie ; Flupirtin ; Paracetamol ; Keywords ; Children ; Acute treatment ; Tension-type headache ; Flupirtine ; Paracetamol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Abstract Background: About 10% of all schoolchil- dren are suffering from migraine and 50% from tension-type headache. Headache of acute onset usually will be treated with analgesic substances like paracetamol, acetylsalicylic acid or ibuprofen, the first one being the reference drug for tension-type headache in childhood. In case of lacking improvement or side-effects there is demand for an alternative safe substance for the acute analgesic therapy. Methods: In a double-blind randomised investigation flupirtine and paracetamol were given in two consecutive attacks of episodic tension-type headache. 30 children, 6–12 years old, were included. Dosage was determined according to age and weight. The children documented the acute headache intensity and duration in a special diary. Results: Headache intensity was reduced during 2 h after intake in 89% of the 19 children treated. The reduction was 6,5 to 3,1 for flupirtine and 6,9 to 3,3/10 for paracetamol. There was no statistically significant difference between the two substances. Relevant side-effects could not be observed. Conclusion: Flupirtine has shown a convincing clinical effect treating acute episodic tension-type headache for children. The substance was well tolerated by the patients. In addition, flupirtine provides a high degree of safety.
    Notes: Zusammenfassung Hintergrund: Etwa 10% aller Schulkinder leiden nach neueren deutschen epidemiologischen Untersuchungen zumindest gelegentlich an Migräne und etwa 50% an Kopfschmerzen vom Spannungstyp. Häufig nehmen sie bei Spannungskopfschmerzen analgetische Monosubstanzen wie Paracetamol, Azetylsalizylsäure oder Ibuprofen ein. Bei nicht ausreichender Wirkung bzw. Unverträglichkeit besteht Bedarf nach weiteren Substanzen für die Akutanwendung. Methode: In einer doppelblindrandomisierten und gekreuzten Anordnung wurden Paracetamol bzw. das analgetisch und muskelrelaxierend wirksame Flupirtin 30 6- bis 12jährigen Kindern für 2 episodische Spannungskopfschmerzattacken angeboten. 10 Kinder benötigten nach dem Erstkontakt keine Medikation mehr, 1 Kind lehnte die Einnahme grundsätzlich ab. Ergebnisse: Die Kopfschmerzstärke verringerte sich laut Kopfschmerztagebuch innerhalb von 2 h nach der Einnahme auf einer numerischen Schmerzskala (0–10) von 6,5 auf 3,1 unter Flupirtin und von 6,9 auf 3,3 unter Paracetamol bei 89% der verbliebenen 19 Kinder. Statistisch signifikante Unterschiede zwischen beiden Substanzen bestanden nicht. Als Nebenwirkung trat 1-mal Erbrechen unter Paracetamol auf. Schlussfolgerung: Flupirtin hat sich in der Akutphase von episodischen Spannungskopfschmerzen beim Kind bewährt. Es verfügt über eine gute Verträglichkeit. Im Vergleich zu Paracetamol scheint v.a. bei akzidenteller Überdosierung eine größere Sicherheit zu bestehen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00009797
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  • 81
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    Electronic Resource
    Begutachtung peripherer Nervenschäden (2000)
    Springer
    Der Schmerz 14 (2000), S. 5-9 
    Details
    ISSN: 1432-2129
    Keywords: Schlüsselwörter ; Periphere Nervenläsionen ; Begutachtung ; Neuropathie ; Minderung der Erwerbs- fähigkeit ; Keywords ; Peripheral nerve lesion ; Neuralgia-physiopathology ; Causalgia-physiopathology ; Loss of earning capacity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Abstract Introduction: The loss of functional capacity by peripheral nerve lesion is easy to be estimated: A certain neurologic dysfunction results in a characteristic reduction of the former individual capacity. In contrast, the effect of accompanying pain to every-day life and working ability is not known exactly. In this study, we compared the results of judgement in nerve lesions under the circumstances of additional pain syndromes. Methods: From January 1994 until Dezember 1998 we saw 57 patients with peripheral nerve lesions, part of them with an additional pain syndrome. Beside conventional neurological examination a detailed pain analysis has been done. Results: Lesions of the median or ulnar nerves showed regularly disturbences in neurological functions (10/14 for the mediane nerve, 13/16 for the ulnar nerve). Astonishing is the fact, that serious pain after nerve lesion only occurs in cases of partial nerve lesion. We saw neuralgias in 6 patients with ulnar neuropathy, in three cases of median nerve lesions we could see severe neuralgia (causalgia we found in 3 cases of ulnar neuropathy, in 6 cases after Median Nerve lesion). Patients with a lesion of the central plexus brachialis showed in 10 of 11 cases an additional pain syndrome. Other nerves have been affected more rarely. For the judgement of the loss of earning capacity we saw an additional pain related diminuition of at least 10% compared to those patients without pain problems. Conclusions: The common grading scales for peripheral nerve lesions are not suitable in cases accompanied by an additional pain syndrome. Beside a functional deficit the effect of severe pain in these patients has to be estimated. On an average, patients with addtitional pain-problems get a 10% extended loss of earning capacity, even more in particular cases.
    Notes: Zusammenfassung Fragestellung: Anhand retrospektiver Daten sollten geeignete Bewertungsgrundlagen für die Begutachtung peripherer Nervenläsionen erarbeitet werden. Methode: Von Januar 1994 bis Dezember 1998 wurden insgesamt 57 Patienten (36 männlich, 21 weiblich, Durchschnittsalter 33,9 Jahre) mit dieser Fragestellung im Rahmen einer Begutachtung untersucht. Ursächlich lagen traumatische Ereignisse bei 39 (68%), postoperative Störungen bei 14 und andere Schädigungen bei 4 Patienten zugrunde. Ergebnisse: Beim N. medianus und N. ulnaris (beispielhaft) überwogen die Schmerzzustände bei inkompletten Läsionen. Neuralgien fanden sich bei 3 bzw. 6 Patienten mit N.-medianus- bzw. N.-ulnaris-Läsion. Eine Kausalgie fand sich bei 6 bzw. 3 Patienten. Mit Ausnahme von Armplexusläsionen waren andere Nerven seltener betroffen. Diese Situation wurde mit einer durchschnittlich um 10% höher gelegenen Einschätzung der Leistungseinbuße berücksichtigt, wenn gleichzeitig Schmerzen vorlagen. Schlussfolgerungen: Die für die reine Funktionseinbuße gültigen Skalen zur Bemessung peripherer Nervenläsionen können für die Begutachtung von Schmerzsyndromen nur bedingt herangezogen werden. Meist führen Schmerzen zu einer um durchschnittlich 10% höheren Einschränkung der Erwerbsfähigkeit (MdE), allerdings sind in manchen Fällen auch größere Einbußen denkbar.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004820050002
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  • 82
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    Electronic Resource
    Chronifizierungsausmaß von Schmerzerkrankungen (2000)
    Springer
    Der Schmerz 14 (2000), S. 10-17 
    Details
    ISSN: 1432-2129
    Keywords: Schlüsselwörter ; Schmerzerkrankungen ; Krankheitsschwere ; Chronifizierungsstadien ; Mainzer Stadienmodell ; Keywords ; Chronic pain ; Grading procedure ; Mainz Pain Staging System
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Abstract Introduction: Chronic pain is an individually variable experience, incorporating physical, psychological and social dimensions. Chronic pain occurs in a broad spectrum of severity; therefore, a grading procedure is of crucial importance in clinical research and in epidemiologic studies. The Mainz Pain Staging System is an interview-administered, multi-dimensional measure of chronic pain severity. The system suggests grading chronic pain in terms of 4 axes: time (persistence), spreading of pain site, medication use, and health care utilization. The whole scale consist of 10 items. The resulting score is used to classify the pain problem in three stages (I, II, III). Analysing the broader validity and parametric properties of the staging system is the purpose of the present study. Methods: The staging system and psychosocial data were administered to 542 consecutive patients of different diagnoses who attended one of six pain clinics in the year 1995/96. In a time period of 3 months since first contact, treatment procedures were registered. Three months after first contact patients rated the effectiveness of treatment concerning reduction of pain intensity. Results: According to the criteria of the staging system 25% of the sample belonged to each stage I and stage III, whereas 50% were classified to stage II. As a measure of validity, chronic pain status demonstrated significant correlation with psychological impairment, disability and time off work, whereas there was no correlation to pain intensity and persistence of pain. Surprisingly we found no difference in amount and quality of treatment between patients who were graded as severe pain patients (stage III) and the other stages. Furthermore, effectiveness of treatment also did not differ between the three stages. We made several proposals for optimizing the staging system. Conclusion: Given the high prevalence of recurrent and chronic pain as well as the broadness of severity, an important issue on further research is identification of factors which influence the chronification process. For this purpose improved measures of graded classification of pain status are needed.
    Notes: Zusammenfassung Hintergrund: Die Beschreibung von Schmerzsyndromen ist durch eine Diagnose allein nicht ausreichend gewährleistet; erst die Angabe der Krankheitsschwere ermöglicht sowohl die Indikation der entsprechenden Behandlung als auch eine Vergleichbarkeit von Fällen. Patienten und Methode: In einer multizentrischen Studie wurde bei 542 Patienten das aus der Mainzer Arbeitsgruppe um Gerbershagen 1986 vorgestellte Stadienmodell der Chronifizierung ermittelt und in Abhängigkeit von Patienten- und Diagnosemerkmalen sowie im Hinblick auf seine parametrischen Eigenschaften analysiert. Ergebnisse und Diskussionen: Die Ergebnisse der Untersuchung bestätigen die gute Validität des Verfahrens im Hinblick auf seine Unabhängigkeit von schmerzspezifischen Parametern. Es besteht theoriegemäß eine gute Übereinstimmung zum Ausmaß der emotionalen Befindlichkeit (Depression), zur subjektiven Beeinträchtigung und zum Ausmaß der Arbeitsunfähigkeit. Die Ergebnisse zeigen auch Ansätze für Verbesserungsmöglichkeiten. Einige der berücksichtigten Kriterien sind vermutlich überflüssig, während der zusätzliche Einbezug des subjektiven Beeinträchtigungserlebens notwendig erscheint. Ob ein übergreifendes Graduierungsmodell für verschiedene Schmerzerkrankungen überhaupt valide sein kann, muss eine weitergehende Analyse zeigen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004820050003
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  • 83
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    Electronic Resource
    Langzeitbehandlung mit Flupirtin (2000)
    Springer
    Der Schmerz 14 (2000), S. 29-32 
    Details
    ISSN: 1432-2129
    Keywords: Schlüsselwörter ; Flupirtin ; Langzeitbehandlung ; Keywords ; Flupirtine ; Long-term treatment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Abstract Case report: The worker O.H., born in 1959, had in 1992 an accident as a car driver. His injuries were a severe acceleration trauma of the cervical spine with rupture of the longitudinal ligament, a concussion of the brain, and an eye injury. Therapy: After the emergency treatment, the multidisciplinary management could not resolve the persistent musculoskeletal cervicocephal and -brachial pain syndrome. The long-term application of 100 mg flupirtine tid improved the chronic pain state for 50–60%. Due to this regimen, the patient could be rehabilitated.
    Notes: Zusammenfassung Fallbericht: Der 1959 geborene Arbeiter (O.H.) erlitt im September 1992 als PKW-Fahrer einen Wegeunfall mit schwerem HWS-Trauma, Commotio cerebri, Oberlidverletzung und Augapfelprellung rechts. Danach persistierten zervikozephale und zervikobrachiale Schmerzen. Behandlung: Nach der Evaluation verschiedener Therapieverfahren erfolgte die Einstellung auf durchschnittlich 3-mal 100 mg Flupirtin täglich mit dem Ergebnis einer durchschnittlich 50- bis 60%igen Linderung starker, belastungsabhängiger Dauerschmerzen. Dank dieser Medikation konnte der Betroffene beruflich integriert werden.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004820050006
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  • 84
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    Electronic Resource
    MRT bei Neugeborenen mit Verdacht auf zerebrale Störung (2000)
    Springer
    Der Radiologe 40 (2000), S. 18-27 
    Details
    ISSN: 1432-2102
    Keywords: Schlüsselwörter ; MRT ; Neugeborene ; Cerebrum ; Fetus ; Key words ; MRI ; Neonatal ; Brain ; Fetal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Magnetic resonance tomography (MRT) has become the most important method in the workup of infantile cerebral complications after primary sonography. Cerebral MR examination and image interpretation during the infantile period require extensive knowledge of morphological manifestations, their pathophysiological background, and frequency. The choice of imaging parameters and image interpretation is demonstrated in infarctions and hemorrhages of the mature and immature brain. A review of the main differential diagnoses is also given. The relevance of MR spectroscopy and fetal MRI is discussed.
    Notes: Zusammenfassung Zur Abklärung zerebraler Veränderungen bei Neugeborenen hat sich die Magnetresonanztomographie (MRT) als wichtigste weiterführende Methode nach der Sonographie entwickelt. Die Durchführung und Auswertung der MR-Untersuchungen erfordern jedoch eine genaue Kenntnis der morphologischen Manifestationen, des pathophysiologischen Hintergrunds und der Häufigkeit bestimmter zerebraler Komplikationen in diesem Lebensalter. Resümee: Ausgehend von zerebrovaskulären Erkrankungen werden diese Fragen behandelt, wobei sowohl auf die Auswahl der adäquaten Untersuchungsparameter als auch auf die Bildinterpretation und die wichtigsten Differentialdiagnosen eingegangen wird. Die Bedeutung von MR-Spektroskopie und fetaler MRT wird diskutiert.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001170050004
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  • 85
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    Electronic Resource
    Thoraxröntgen beim neonatologischen Patienten (2000)
    Springer
    Der Radiologe 40 (2000), S. 43-51 
    Details
    ISSN: 1432-2102
    Keywords: Schlüsselwörter ; Thorax ; Neugeborene ; Frühgeborene ; Kongenitale Pathologien ; Erworbene Pathologien ; Key words ; Chest ; Newborn ; Preterm infant ; Congenital pathologies ; Acquired pathologies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary In diagnostic imaging of thoracic pathologies in mature and especially immature neonates, chest X-ray has a leading position. Profound knowledge of the normal chest X-ray and the potential physiological perinatal changes is the basic requirement for interpretation of the X-ray of a neonate. Childhood pathologie: Many congenital and acquired diseases that the radiologist is faced with in neonatology are unknown in the imaging of adults. Many of these changes are life-threatening or may have an impact on the patient’s future quality of life. Therefore early diagnosis in close cooperation with the paediatrician is essential. We give here an overview of the most important pathologic changes that the radiologist may be con- fronted with in daily routine.
    Notes: Zusammenfassung In der bildgebenden Diagnostik thorakaler Pathologien bei reifen und insbesondere unreifen Neugeborenen steht das Thoraxröntgenbild an erster Stelle. Profunde Kenntnisse des normalen Thoraxbilds und der möglichen physiologischen peripartalen Veränderungen sind Voraussetzung für die Interpretation der neonatologischen Thoraxaufnahme. Kindliche Pathologien: Eine Vielzahl von kongenitalen und erworbenen Veränderungen, mit denen der Radiologe in der Neonatologie konfrontiert ist, sind in der Radiodiagnostik des erwachsenen Patienten unbekannt. Viele dieser Veränderungen sind für den Patienten lebensbedrohlich oder können die Lebensqualität in seinem weiteren Leben beeinflussen. Eine frühzeitige Diagnostik in enger Zusammenarbeit mit dem Pädiater ist daher essenziell. Hier wird ein Überblick über die wichtigsten Pathologien, mit denen der Radiologe in der täglichen Routine konfrontiert sein kann, gegeben.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001170050007
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  • 86
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    Electronic Resource
    Gastrointestinaler Notfall im Neugeborenenalter (2000)
    Springer
    Der Radiologe 40 (2000), S. 63-71 
    Details
    ISSN: 1432-2102
    Keywords: Schlüsselwörter ; Gastrointestinaler Notfall ; Neugeborenenalter ; Bildgebende Diagnostik ; Key words ; Gastrointestinal emergency ; Nenoate ; Diagnostic imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Gastrointestinal emergencies in neonates often demand a quick and efficient diagnos-tic imaging. The procedures have to take the special diseases and conditions in these babies and preterm children into account. Conclusion: This paper summarises the most common causes for gastrointestinal neonatal emergencies and discusses the indication and performance as well as the diagnostic value of the commonly used modalities, giving some suggestions for an efficient imaging algorithm. Most of the time conventional plain abdominal films and sonography can answer the clinically important questions, however, in certain conditions fluoroscopy with contrast administration (enema, etc.) is mandatory. Only rarely is CT, MRI or Angiography indicated.
    Notes: Zusammenfassung Der gastrointestinale Notfall im Neugeborenenalter erfordert oft eine rasche, effiziente, den Bedingungen des Neu- und Frühgeborenenalters angepasste bildgebende Diagnostik. Diese Arbeit beschreibt die in diesem Zusammenhang wichtigsten angeborenen und erworbenen Erkrankungen und diskutiert die Durchführung und Indikation bzw. den Stellenwert der zur Verfügung stehenden bildgebenden Methoden. Schlussfolgerung: Zumeist kann mit dem Abdomenübersichtsröntgen und dem Sonogramm eine ausreichende diagnostische Klärung erzielt werden. Bei bestimmten Fragestellungen ist jedoch eine weitergehende Beurteilung durch ein Kontrastmittelröntgen bzw. eine Durchleuchtungsuntersuchung (wie z.B. Schluckakt- und Magenröntgen oder Irrigoskopie) unabdingbar. CT, MRT oder Angiographie werden nur seltenst benötigt.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001170050010
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  • 87
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    Electronic Resource
    Intranetanwendungen in der Radiologie (2000)
    Springer
    Der Radiologe 40 (2000), S. 78-82 
    Details
    ISSN: 1432-2102
    Keywords: Schlüsselwörter ; Intranet ; Internet ; PACS ; Radiologie ; Key words ; Intranet ; Internet ; PACS ; Radiology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary The aim of the paper is to present the conceptual basis and capabilities of intranet applications in radiology. The intranet, which is the local brother of the internet can be readily realized using existing computer components and a network. All current computer operating systems support intranet applications which allow hard and software independent communication of text, images, video and sound with the use of browser software without dedicated programs on the individual personal computers. Radiological applications for text communication e.g. department specific bulletin boards and access to examination protocols; use of image communication for viewing and limited processing and documentation of radiological images can be achieved on decentralized PCs as well as speech communication for dictation, distribution of dictation and speech recognition. Discussion: The intranet helps to optimize the organizational efficiency and cost effectiveness in the daily work of radiological departments in outpatients and hospital settings. The general interest in internet and intranet technology will guarantee its continuous development.
    Notes: Zusammenfassung Ziel dieses Beitrags ist es, konzeptionelle Grundlagen und Möglichkeiten von Intranetanwendungen in der Radiologie aufzuzeigen. Das Intranet, das der lokale Bruder des Internets ist, kann gegenwärtig relativ einfach mit den bestehenden Computerkomponenten und einem Netzwerk realisiert werden. Alle aktuellen Betriebssysteme unterstützen Intranetanwendungen, mit denen sowohl Hardware – als auch Software – unabhängig mit Hilfe von sog. Browsern die Kommunikation von Text, Bild, Video und Ton möglich ist, ohne dass auf den peripheren Rechnern entsprechend spezielle Software vorhanden sein muss. Beispielhafte Anwendungen der Textkommunikation werden vorgestellt, wie z.B. abteilungsspezifische Informationen und Untersuchungsprotokolle, außerdem Anwendungen der Bild- und Tonkommunikation. Diskussion: Das Intranet eröffnet insbesondere im täglichen Einsatz radiologischer Abteilungen im ambulanten und stationärem Bereich neue Möglichkeiten zur organisatorischen Effizienzsteigerung und Kosteneffektivität. Das globale Interesse an der Inter- und Intranettechnologie sichert die kontinuierliche Weiterentwicklung.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001170050012
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    Electronic Resource
    Radiodiagnostik der Lunge (2000)
    Springer
    Der Radiologe 40 (2000), S. 870-877 
    Details
    ISSN: 1432-2102
    Keywords: Schlüsselwörter Lunge ; Perfusion ; Ventilation ; Computertomographie (CT) ; Magnetresonanztomographie (MRT) ; Keywords Lung ; Perfusion ; Ventilation ; Computed tomography ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Abstract Radiological cross-sectional imaging modalities, particularly computed tomography (CT) have become the mainstays for diagnosing lung disease in recent years. These enable morphological visualization of pathological processes with the greatest possible spatial resolution. Modern technical developments and complementary strategies have led to new applications and new functional assessments which need to be reviewed together with state-of-the-art techniques in nuclear imaging. The diagnosis of pulmonary embolism using spiral CT angiography and magnetic resonance (MR) angiography certainly belongs in this category. CT has become the an alternative modality of first choice, and it is also challenging pulmonary angiography as the gold standard. Direct visualization of patent pulmonary arteries and thromboembolic material is complemented by that of effects on the pulmonary parenchyma and right heart function; it also provides perfusion studies and MR-based flow measurement to assess hemodynamic compromise. Ventilation studies have long been a domain of nuclear imaging, and new techniques for the direct visualization of ventilation are emerging from recent developments in the field of MR imaging, for example, using hyperpolarized inert gases. New functional parameters of ventilation can be derived from these studies. For the diagnosis of metabolically active disease, such as tumor and pneumonia, CT offers very high sensitivity, for example, in screening for intrapulmonary nodules using low-dose CT and in the early detection of pulmonary infiltrates in high-risk patients. Especially for characterizing pulmonary nodules there is a need to combine nuclear medicine techniques, such as in positron-emission tomography.
    Notes: Zusammenfassung Die radiologischen Schnittbildverfahren, insbesondere die CT, haben sich innerhalb kurzer Zeit einen herausragenden Stellenwert in der Diagnostik von Lungenerkrankungen erworben. Dies umfasst in erster Linie die morphologische Darstellung pathologischer Prozesse mit hoher räumlicher Auflösung. Moderne technische Entwicklungen und kombinierte Untersuchungsstrategien eröffnen neue Einsatzgebiete und auch funktionelle Aussagen, die nach einer aktuellen Standortbestimmung gemeinsam mit den nuklearmedizinischen Verfahren verlangen. Dazu gehört die Diagnostik der Lungenembolie mittels Spiral-CT-Angiographie und MR-Angiographie der Pulmonalarterien. Hier hat sich mittlerweile die CT als alternatives Verfahren der Wahl etabliert und die Rolle der Pulmonalisangiographie als Goldstandard infrage gestellt. Die reine direkte Darstellung der durchströmten Pulmonalarterien und des thromboembolischen Materials wird durch Diagnostik intrapulmonaler und kardialer Veränderungen, Perfusionsuntersuchungen sowie MR-basierte Flussmessungen zur hämodynamischen Beurteilung erweitert. Nachdem Untersuchungen der Ventilation lange Zeit eine Domäne der Nuklearmedizin waren, eröffnen aktuelle Entwicklungen in der MRT neue Verfahren zur direkten Visualisierung der Lungenbelüftung, z. B. mittels polarisierter Edelgase. Aus diesen Verfahren lassen sich auch neue funktionelle Parameter der Ventilation ableiten. In der Diagnostik von Tumoren und Entzündungen überzeugt die CT insbesondere durch ihre hohe Sensitivität, z. B. beim Screening auf intrapulmonale Rundherde mittels Niedrigdosis-CT oder bei der Früherkennung pneumonischer Infiltrate bei Risikopatienten. Insbesondere bei der Charakterisierung intrapulmonaler Rundherde ist eine Kombination mit nuklearmedizinischen Verfahren (PET) grundsätzlich anzustreben.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001170050846
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    Erste Erfahrungen mit der Mehrzeilendetektorspiral-CT in der Diagnostik der Arteriosklerose der Koronargefäße (2000)
    Springer
    Der Radiologe 40 (2000), S. 118-122 
    Details
    ISSN: 1432-2102
    Keywords: Schlüsselwörter ; Mehrzeilen-CT ; Elektronenstrahl-CT ; Koronar-Screening ; CT Angiographie ; Koronarsklerose ; Keywords ; Multidetector CT ; Electron beam CT ; Coronary screening ; CT angiography ; Coronary atherosclerosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Purpose: Multirow-detector-spiral-CT (MSCT) allows for 250 ms effective exposure time. The purpose of this study was to demonstrate the possibilities and limitations of this CT technology for non enhanced and contrast enhanced investigation of the coronary arteries. Methods: Investigation of the coronary arteries without contrast medium for quantification of coronary calcifications was performed in an obese patient (140 kg) with MSCT and electron beam CT (EBCT). In 56 patients contrast enhanced CT angiography of the coronary arteries was performed to determine image quality depending on the heart rate. Results: In the obese patient superior image quality could be achieved with MSCT allowing for reliable quantification of coronary calcifications. With MSCT angiography of the coronary arteries good image quality was achieved in patients with a heart rate of 59±8 beats per minute. Conclusion: Even if there are limitations in patients with higher heart rates with an effective exposure time of 250 ms MSCT has clear advantage of image quality in the assessment of non enhanced and contrast enhanced coronary arteries.
    Notes: Zusammenfassung Fragestellung: Mit dem Mehrzeilendetektorspiral-CT (MSCT) sind effektive Aufnahmezeiten von 250 ms möglich. Die Möglichkeiten und Grenzen dieser CT-Technologie zur nativen und kontrastverstärkten Untersuchung der Koronargefäße sollen in dieser Arbeit dargestellt werden. Methode: Die native Untersuchung der Koronargefäße zur Quantifizierung von Koronarkalk wurde bei einem Patienten mit Adipositas (140 kg) mit dem Elektronenstrahl-CT (EBCT) und dem MSCT vorgenommen. Bei 56 Patienten wurde eine kontrastverstärkte MSCT-Angiographie der Koronargefäße vorgenommen und festgestellt, bei welcher Herzfrequenz eine diagnostisch ausreichende Bildqualität zu erreichen ist. Ergebnisse: Bei der Untersuchung des Patienten mit Adipositas konnte mit dem MSCT eine erheblich bessere Bildqualität erreicht werden, die eine Quantifizierung von Koronarkalk erheblich erleichterte. Mit der MSCT-Angiographie der Koronargefäße konnte bei einer Herzfrequenz von 59±8 Schlägen/min eine diagnostisch gute Bildqualität erreicht werden. Schlussfolgerung: Auch wenn mit einer effektiven Aufnahmezeit von 250 ms Limitationen bei höheren Herzfrequenzen zu erwarten sind, können mit dem MSCT entscheidende Vorteile in der Bildqualität in der nativen und kontrastverstärkten Untersuchung der Koronargefäße erreicht werden.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001170050019
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  • 90
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    Bestimmung links- und rechtsventrikulärer Volumenejektionsfraktionen (VEF) mittels MRT bei 1,0 T (2000)
    Springer
    Der Radiologe 40 (2000), S. 136-142 
    Details
    ISSN: 1432-2102
    Keywords: Schlüsselwörter ; Herz ; Herz-MR ; Volumen ; Cine MR ; Key words ; Heart ; Cardiac MRI ; Volume ; Cine MR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Purpose: To evaluate method- and user effects as well as the required time in the determination of left- and right ventricular ejection fractions in comparing manual and semiautomatic border detection of the endocardium. Methods: In 22 patients with varying cardiac diseases endocardial borders were detected either manually or semiautomatically (seeded ROI) and subsequently the right and left ventricular volume ejection fractions were computer-calculated. Two investigators defined the endocardial borders for both ventricles using both methods. For statistical analysis two-factorial analyses of variance were performed for the four variables: VEF right ventricle, VEF left ventricle, required time right ventricle, required time left ventricle (SAS, Anova). Results: There was no user or method effect detectable for both ventricles. The required time for both ventricles also did not reveal a user effect, but there was a dramatic method effect concerning a reduction of the required time for analysis for both ventricles 〉50%. Conclusions: The semiautomatic mode for detecting the endocardial borders in determining right and left ventricular ejection fractions did not demonstrate results differing from the results of the manual method, but is significantly superior concerning the time required for analysing ejection fractions of both ventricles with a reduction of over 50%. This might significantly reduce the expenditure for personnel.
    Notes: Zusammenfassung Fragestellung: Die manuelle und semiautomatische Endokarddetektion zur Bestimmung links- und rechtsventrikulärer Volumenejektionsfraktionen (VEF) werden verglichen. Ziel dieser Arbeit ist die Evaluierung des Methoden- und Anwendereffekts sowie der Bearbeitungszeit beider Verfahren. Methode: An 22 Patienten mit unterschiedlichen kardialen Erkrankungen wurden die Endokardgrenzen manuell und mit einem semiautomatischen Verfahren (Seeded-ROI) ermittelt und anschließend die rechts- und linksventrikulären Volumenejektionsfraktionen automatisch berechnet. In allen Fällen wurden von 2 Untersuchern die Endokardgrenzen des rechten und linken Ventrikels manuell und semiautomatisch bestimmt. Zur statistischen Analyse wurden 2-faktorielle Varianzanalysen (Methoden- und Anwendereffekt einschließlich Wechselwirkungen) für die 4 Variablen durchgeführt: VEF rechtsventrikulär, VEF linksventrikulär, Zeitaufwand rechtsventrikulär, Zeitaufwand linksventrikulär (SAS, Anova). Ergebnisse: Bezüglich der Bestimmungen der rechts- und linksventrikulären VEF war weder ein Methoden- (p=0,9613) noch ein Anwendereffekt (p=0,3095) nachweisbar. Bezogen auf die benötigte Bearbeitungszeit fand sich ebenfalls kein Anwendereffekt, aber ein massiver Methodeneffekt (p〈0,0001) im Sinn einer Reduzierung der Bearbeitungszeit um 〉50% sowohl für den rechten als auch für den linken Ventrikel. Schlussfolgerung: Nach unseren Erfahrungen liefert das semiautomatische Seeding-Verfahren zur Festlegung der Endokardgrenzen bei der Bestimmung der links- und rechtsventrikulären Ejektionsfraktionen keine von der manuellen Methode abweichenden Ergebnisse, ist aber bezüglich der Bearbeitungszeit deutlich überlegen. Die über 50%ige Zeitersparnis reduziert den Personalaufwand.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001170050022
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  • 91
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    Myokardperfusion in Ruhe und unter Belastung (2000)
    Springer
    Der Radiologe 40 (2000), S. 155-161 
    Details
    ISSN: 1432-2102
    Keywords: Schlüsselwörter ; Koronare Herzkrankheit ; Magnetresonanztomographie ; Myokardperfusion ; SPECT ; Key words ; Coronary artery disease ; Magnetic resonance imaging ; Myocardial perfusion ; SPECT
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Aim: Performance of combined rest/stress MR perfusion studies and the analysis of qualitative signal intensity parameters in comparison with 99mTc-SestaMIBI SPECT in patients with known coronary artery disease (CAD). Methods: Sixteen patients with CAD underwent MR myocardial perfusion assessment at rest and after dipyridamole-induced hyperemia. Qualitative parameters (SI increase, SI upslope) of the SI time-curves were evaluated and characteristics of normal, reversible and persistent hypoperfused myocardium as assessed by 99mTc-SestaMIBI SPECT were compared. Results: Compared with the rest values, normal myocardium showed a significant increase of the SI upslope during hyperemia (P〈0.001), whereas persistent (P=0.07) and reversible (P=0.15) hypoperfusions showed only minor changes. SI increase over baseline also showed a significant increase only in normal myocardium (P〈0.001). At rest, reversible ischemic areas showed no significant differences from normal myocardium, whereas during hyperemia SI increase was significantly lower (P=0.02). Conclusions: Qualitative SI parameters of a combined rest/stress MR myocardial perfusion study allow to differentiate normal from reversibly or persistently hypoperfused myocardium.
    Notes: Zusammenfassung Fragestellung: Die kombinierte Ruhe- und Belastungsuntersuchung der myokardialen Durchblutung in der MRT sowie die Analyse qualitativer SI-Parameter der MR-Myokardperfusion bei Patienten mit koronarer Herzkrankheit wurden mit der 99mTc-SestaMIBI SPECT verglichen. Methode: Bei 16 Patienten mit koronarer Herzkrankheit (KHK) wurde in der MRT mit einer Mehrschichtgradientenechotechnik die Myokardperfusion unter Ruhe- und Belastungsbedingungen untersucht. Qualitative Signalintensitätsparameter der Kontrastmittelanflutung wurden berechnet und die Parameter in normalen, reversibel und persistierend minderperfundierten Myokardarealen miteinander verglichen. Ergebnisse: Normales Myokard zeigte im Gegensatz zu reversiblen (P=0,15) und persistierenden (P=0,07) Ischämien eine signifikante Zunahme der SI-Anstiegssteilheit unter Belastung (P〈0,001). Die SI-Zunahme zeigte ebenfalls nur in normal perfundierten Arealen eine signifikante Zunahme (P〈0,001) nach Belastung. Unter Belastung zeigte sich bei reversiblen Ischämien eine signifikant niedrigere SI-Zunahme als in normalem Myokard (P=0,02), während sich in Ruhe kein Unterschied zeigte. Schlussfolgerung: Qualitative SI-Parameter der kombinierten MR-Perfusionsuntersuchung des Myokards in Ruhe und unter Belastung erlauben die Differenzierung zwischen normalem sowie reversibel oder persistierend minderperfundiertem Myokard.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001170050025
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  • 92
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    Wertigkeit der diffusionsgewichteten MRT in der Beurteilung von Knochenmarkveränderungen bei Wirbelkörpermetastasen (2000)
    Springer
    Der Radiologe 40 (2000), S. 731-736 
    Details
    ISSN: 1432-2102
    Keywords: Schlüsselwörter Diffusionsgewichtete Kernspintomographie ; Wirbelkörpermetastasen ; Diffusionskoeffizient ; Keywords Diffusion weighted imaging (DWI) ; Magnetic resonance imaging ; Vertebral metastases ; Diffusion coefficient ; ADC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Abstract Aim of the study. The aim of the study was the evaluation of the diffusion coefficient (ADC) of vertebral metastasis and regular vertebral bodies with diffusion weighted MRI (DWI). DWI evaluates the tissue-specific molecular diffusion of protons. In tissues with high cell densities (neoplasm) a decreased ADC can be expected due to restricted diffusion according to an exaggerated amount of intra- and intercellular membranes (i. e. diffusion barriers). Methods. In 5 breast cancer patients the ADC of both known vertebral metastases and of adjacent regular vertebral bodies were measured with DWI (1.0 T; Phased-Array-Body-Coil; b: 880 and 440 s/mm2). Results. The ADC of regular vertebral bodies (1.3±0.23×10–,3s/mm2) was significantly (p≤0.0002) higher than in vertebral metastases (0.39±0.11×10–3s/mm2). Conclusions. These data demonstrate that the ADC can be reliably measured in vertebral bodies. The quantitative evaluation of the ADC in vertebral bodies seems to be an objective and comparable parameter for differentiating malign from benign vertebral tissue.
    Notes: Zusammenfassung Ziel. Ziel der Arbeit war die Messung des Diffusionskoeffizienten (ADC) mittels diffusionsgewichteter (DW) MRT in Wirbelkörpermetastasen und in MR-morphologisch unauffälligen Wirbelkörpern. Die DW-MRT misst den für ein Gewebe spezifischen ADC, welcher der Eigendiffusion von Wasserstoffmolekülen entspricht. In zellreichem Tumorgewebe mit zahlreichen intra- und interzellulären Membranen (d. h. Diffusionsbarrieren) ist ein niedriger, in zellarmen oder nekrotischem Gewebe, ein hoher ADC zu erwarten. Methode. Bei 5 Patientinnen mit Mammakarzinom wurde der ADC von Lendenwirbelkörpermetastasen sowie von angrenzenden, MR-morphologisch unauffälligen Wirbelkörpern ermittelt (1,0 T; Phased-Array-Body-Coil; b: 880 und 440 s/mm2). Ergebnisse. Der ADC in MR-morphologisch unauffälligen Wirbelkörpern (1,3±0,23×10–3s/mm2) war signifikant (p≤0,0002) höher als in Wirbelkörpermetastasen (0,39±0,11×10–3s/mm2). Schlussfolgerung. Anhand dieser Daten konnte gezeigt werden, dass der ADC von Wirbelkörpern verlässlich gemessen werden kann, und dass durch die quantitative Bestimmung des ADC ein objektiv vergleichbarer Parameter zur Verfügung steht, der zur Differenzierung von malignem und benignem Gewebe gut geeignet erscheint.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001170050803
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  • 93
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    Entwicklungen in der Neonatologie (2000)
    Springer
    Der Radiologe 40 (2000), S. 2-7 
    Details
    ISSN: 1432-2102
    Keywords: Schlüsselwörter ; Neugeborenes ; Frühgeborenes ; Bildgebung ; Key words ; Newborn ; Premature infant ; Diagnostic imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Modern neonatology comprises care for a growing number of infants with congenital abnormalities and an increasing number of premature born infants. The survival rates of premature infants have increased dramati- cally during the past decade. This increase in survival rates can be attributed to improved prenatal and obstetric management and to advances in neonatal intensive care medicine. Radiological support: Neonatology has become a pediatric subspeciality of its own resulting in the demand for an equally specialised radiological support. Therefore the availability of a children´s radiologist for radiological and sonographic examinations is mandatory (24 hours a day) for optimal patient care on a neonatal intensive care unit. A good cooperation between radiologist and neonatologist in neonatal intensive care medicine is therefore warranted.
    Notes: Zusammenfassung Die moderne Neugeborenenintensivmedizin umfasst neben den typischen neonatalen Krankheitsbildern eine wachsende Zahl kleiner Frühgeborener mit einem Geburtsgewicht 〈1500 g und eine, durch verbesserte pränatale Diagnostik, zunehmend größer werdende Gruppe von Kindern mit komplexen Fehlbildungen. Anforderungen an den Radiologen: Diese Entwicklungen stellen auch an den Radiologen neue Anforderungen; neben der zunehmenden Zahl an Frühgeborenen und ihren speziellen Krankheitsbildern ist auch die Abklärung von speziellen, beim Intensivpatienten auftretenden Problemen erforderlich. Durch die meist gegebene Dringlichkeit der radiologischen Abklärung ist die Verfügbarkeit eines Kinderradiologen rund um die Uhr unabdingbar. Zudem müssen fahrbare Röntgen- und Ultraschallgeräte zur Verfügung stehen, um eine Diagnostik direkt am Krankenbett zu ermöglichen. Diskussion: An einer Neugeborenenintensivstation ist daher eine enge Zusammenarbeit mit dem Kinderradiologen unbedingt notwendig.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001170050002
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    Bildgebende Diagnostik des Neonatal stroke (2000)
    Springer
    Der Radiologe 40 (2000), S. 28-34 
    Details
    ISSN: 1432-2102
    Keywords: Schlüsselwörter ; Zerebralinfarkt ; Krampfanfall ; Neugeborenes ; Dopplersonographie ; Vasospasmus ; Key words ; Cerebral artery infarction ; Seizure ; Newborn ; Doppler sonography ; Vasospasm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary A cerebral artery infarction is an important differential diagnosis in the newborn with neurological abnormalities. Based on clinical data, its incidence is estimated to be 1 in 4000 newborns. Since the course is often subclininal, the true incidence is probably higher. Diagnosis: Cerebral ultrasound and Doppler sonography as readily available screening tools play a central role in the initial diagnosis of neonatal cerebral infarction. Definitive diagnosis is made by computed tomography or magnetic resonance imaging. Beside symptomatic anticonvulsive therapy, treatment aims at the prevention of secondary ischemic injury. Discussion: Three term infants with different clinical courses of neonatal stroke are presented to sensitize the clinician and the radiologist for this probably underdiagnosed entity. The role of imaging modalities in the diagnosis and follow-up of neonatal cerebral infarction is discussed.
    Notes: Zusammenfassung Ein Infarkt im Stromgebiet der Zerebralarterien stellt eine wichtige Differentialdiagnose bei neurologischen Auffälligkeiten in der Neonatalperiode dar. Die Inzidenz wird anhand von klinischer Daten auf 1:4000 Lebendgeborene geschätzt. Da der Verlauf oft subklinisch ist, liegt die wahre Inzidenz wahrscheinlich höher. Diagnose: Bei der Diagnosestellung kommen dem Schädelultraschall und der Dopplersonographie als leicht verfügbaren Screening-Methoden eine zentrale Rolle zu. Die definitive Diagnose wird, je nach Verfügbarkeit, mittels Computertomographie oder Kernspintomographie gestellt. Die Behandlung ist neben der symptomatischen (antikonvulsiven) Therapie auf die Vermeidung von ischämischen Sekundärschäden gerichtet. Diskussion: Wir wollen mit der vorliegenden Arbeit anhand von 3 Kindern mit verschiedenen klinischen Verläufen eines sog. Neonatal stroke den Stellenwert der bildgebenden Verfahren bei der Diagnostik und Verlaufskontrolle aufzeigen und die Sensibilität für dieses vermutlich unterdiagnostizierte Krankheitsbild erhöhen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001170050005
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  • 95
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    „Lines and Tubes” beim neonatologischen Intensivpatienten (2000)
    Springer
    Der Radiologe 40 (2000), S. 52-57 
    Details
    ISSN: 1432-2102
    Keywords: Schlüsselwörter ; Zentrale Katheter ; Neonatologie ; Radiologie ; Key words ; Central catheter ; Neonatology ; Radiology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Background: Central catheters in neonatological intensive care patients are used for the prolonged application of medicataion or parenteral infusions. Dislocations and septic and thromboembolic complications may occur. Control of position: Radiologically, the correct position of the catheter must be proven. Dislocations or complications associated with central catheters must be diagnosed. For catheter monitoring plain film radiographs are the first line of investigation; however, sonography may be of additional assistance. Angiographic techniques should only be performed when conventional noninvasive methods do not supply satisfactory results. Special knowledge is necessary for monitoring catheters that are set via the umbilical artery or vein. The radiological applications for catheter monitoring in the neonate intensive care unit are discussed in this article.
    Notes: Zusammenfassung Hintergrund: Die im neonatologischen Krankengut am häufigsten verwendeten Zugänge sind Katheter, die eine prolongierte Verabreichung von Antibiotika, höher osmolarer Lösungen oder evtl. Chemotherapeutika gewährleisten. Komplikationen ergeben sich durch Fehllagen oder sind septischer und thrombembolischer Genese. Lagekontrolle: Für den Radiologen gilt es, eine adäquate Lagekontrolle des Katheters durchzuführen, um Fehllagen zu vermeiden, jedoch auch Komplikationen zu diagnostizieren. Für dieses Kathetermonitoring steht zur Lagekontrolle das Nativbild im Vordergrund, des Weiteren erweist sich jedoch die Sonographie als wesentlicher Pfeiler in der Katheterdiagnostik, insbesondere im Hinblick auf die katheterassoziierten Komplikationen. Angiographische Techniken sollten erst nach Ausschöpfen sämtlicher nichtinvasiver diagnostischer Möglichkeiten durchgeführt werden. Besondere Anforderungen ergeben sich durch die in der Neonatologie verwendeten Zugänge über den Nabel, wobei sowohl Kenntnis der exakten Topographie der Katheterlage als auch der speziellen potentiellen Komplikationen von großer Bedeutung ist. Im Folgenden sollen die radiologischen Aufgaben und Möglichkeiten beim Kathetermonitoring unter besonderer Berücksichtigung spezieller Anforderungen bei neonatologischen Intensivpatienten vorgestellt werden.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001170050008
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  • 96
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    Nekrotisierende Enterokolitis (NEC) beim Neugeborenen (2000)
    Springer
    Der Radiologe 40 (2000), S. 58-62 
    Details
    ISSN: 1432-2102
    Keywords: Schlüsselwörter ; Nekrotisierende Enterokolitis ; Pneumatosis intestinalis ; Pneumoportogramm ; Perforation ; Leeraufnahme des Abdomens ; Sonographie ; Key words ; Necrotizing enterocolitis ; Pneumatosis intestine ; Pneumoportogram ; Perforation ; Plain radiography ; Sonography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Necrotizing enterocolitis (NEC) is a disease of the premature neonate that requires early therapy, sometimes even surgery and therefore early diagnosis. In general, plain radiography of the abdomen and sonography are valuable imaging techniques for diagnosis of NEC. Course of NEC: The disease starts with distension of small bowel loops. Furthermore the children develop pneumatosis in the bowel wall, which is a nonspecific pattern. If the NEC persists, the air passes into the portal vein system, causing a pneumoportogram. Finally, the disease can lead to perforation. In doubtful cases, the plain radiogram must be repeated within a period of 6 h. With sonography distension of the bowel, thickening of and pneumatosis in the bowel wall, the pneumoportogram and free intraperitoneal fluid can be easily depicted. The most common complications of NEC are intestinal stenosis and strictures that can lead to ileus. Differential diagnosis: Focal perforation of ileum, volvulus and Hirschsprung’s disease are some of the differential diagnoses.
    Notes: Zusammenfassung Die nekrotisierende Enterokolitis (NEC) ist eine schwere Erkrankung des Abdomens bei Frühgeborenen, die einer raschen, nötigenfalls chirurgischen Therapie zugeführt werden muss. Dazu bedarf es einer frühen Diagnose, die mit einer Leeraufnahme des Abdomens und Sonographie gestellt werden kann. Verlauf von NEC: Die NEC beginnt mit einer Dilatation des Darms, zumeist des Dünndarms, in 2. Linie des Dickdarms. Des Weiteren entwickeln sich stehende Schlingen und eine Pneumatosis intestinalis, die ein unspezifisches Zeichen ist und bei allen ischämischen Darmerkrankungen auftreten kann. Beim Fortschreiten der Erkrankung kommt es zum Pneumoportogramm und im schlimmsten Fall zur Perforation. Bei unklaren Abdomenleerbefunden ist eine engmaschige radiologische Kontrolle notwendig. Sonographisch können sowohl die Distension des Darms als auch die Pneumatosis intestinalis als auch das Pneumoportogramm als auch freie Flüssigkeit hervorragend erfasst werden. Spätkomplikationen sind Stenosen und Strikturen, die zu Subileus und Ileus führen können. Differentialdiagnosen: Die Differentialdiagnosen reichen von fokaler Ileumperforation bis hin zu Volvulus und Morbus Hirschsprung.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001170050009
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    MRI demonstration of intracerebral cryptococcal granuloma (2000)
    Springer
    Neuroradiology 42 (2000), S. 30-33 
    Details
    ISSN: 1432-1920
    Keywords: Key words Granuloma cryptococcal ; Magnetic resonance imaging ; Pulse sequences
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We report an intracerebral cryptococcal granuloma in a patient who presented with recent memory disturbance and deteriorating mental status followed by temporary loss of consciousness. To our knowledge, this is the first reported case of an intracerebral cryptococcal granuloma examined by a combination of conventional MRI, fluid-attenuated inversion-recovery and diffusion-weighted imaging and in which the surgical specimen was analysed histochemically.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002340050006
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  • 98
    Electronic Resource
    Electronic Resource
    MRI of intracranial toxoplasmosis after bone marrow transplantation (2000)
    Springer
    Neuroradiology 42 (2000), S. 14-18 
    Details
    ISSN: 1432-1920
    Keywords: Key words Bone marrow, transplantation ; Toxoplasmosis, cerebral ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Toxoplasma encephalitis was confirmed by biopsy in three patients with bone marrow (BMT) or peripheral blood stem-cell transplantation (PBSCT). All had MRI before antimicrobial therapy. The intensity of contrast enhancement was very variable. One patient had one large, moderately enhancing cerebral lesion and several smaller almost nonenhancing lesions. The second had small nodular and haemorrhagic lesions without any enhancement. The third had late cerebral toxoplasmosis and showed multiple lesions with marked contrast enhancement. The moderate or absent contrast enhancement in the two patients in the early phase of cerebral toxoplasmosis may be related to a poor immunological response, with a low white blood cell count in at least one patient. Both received higher doses of prednisone than the patient with late infection, leading to a reduced inflammatory response. In patients with a low leukocyte count and/or high doses of immunosuppressive therapy, typical contrast enhancement may be absent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002340050003
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  • 99
    Electronic Resource
    Electronic Resource
    Cranial MRI in the Nijmegen breakage syndrome (2000)
    Springer
    Neuroradiology 42 (2000), S. 43-47 
    Details
    ISSN: 1432-1920
    Keywords: Key words Nijmegen breakage syndrome ; Anomalies of brain ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We present the results ¶of MRI examinations in ten patients with documented Nijmegen ¶breakage syndrome (NBS), aged 1.75–19 years. T1-, Proton-Density- and T2-weighted spin-echo sequences were performed in three planes. All patients showed microcephaly with decreased size of the frontal lobes and narrow frontal horns. In four patients agenesis of the posterior part of the corpus callosum was found, with colpocephaly and temporal horns dilatation. In one patient callosal hypoplasia was accompanied by abnormal cerebrospinal fluid spaces and wide cerebral cortex, suspicious of pachygyria. Sinusitis was present in all ten patients, as a result of primary immunodeficiency. As in ataxia teleangiectasia and other breakage syndromes, patients with NBS show an inherited susceptibility to malignancy and hypersensitivity to X- and γ-radiation. CT is therefore contraindicated in these patients and MRI should be the method of choice for diagnostic imaging.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002340050011
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  • 100
    Electronic Resource
    Electronic Resource
    MRI and 18F-fluorodeoxyglucose positron emission tomography in hemimegalencephaly (2000)
    Springer
    Neuroradiology 42 (2000), S. 749-752 
    Details
    ISSN: 1432-1920
    Keywords: Key words Hemimegalencephaly ; Positron emission tomography ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We report hemimegalencephaly in a 44-year-old woman with mental retardation, epilepsy and a mild hemiparesis. In addition to typical findings on MRI, 2-deoxy-2[18F]fluorodeoxyglucose positron-emission tomography (PET) demonstrated glucose hypometabolism of the affected hemisphere. The results of PET have been coregistered with morphological information from the MRI studies by image fusion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002340000398
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