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  • 1
    Publication Date: 2014-11-10
    Description: Graphs with circular symmetry, called webs, are relevant w.r.t. describing the stable set polytopes of two larger graph classes, quasi-line graphs and claw-free graphs. Providing a decent linear description of the stable set polytopes of claw-free graphs is a long-standing problem. However, even the problem of finding all facets of stable set polytopes of webs is open. So far, it is only known that stable set polytopes of webs with clique number $\leq 3$ have rank facets only while there are examples with clique number $〉4$ having non-rank facets.
    Keywords: ddc:000
    Language: English
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  • 2
    Publication Date: 2014-02-26
    Description: The bio-heat transfer equation is a macroscopic model for describing the heat transfer in microvascular tissue. In [{\sl Deuflhard, Hochmuth 2002}] the authors applied homogenization techniques to derive the bio-heat transfer equation as asymptotic result of boundary value problems which provide a microscopic description for microvascular tissue. Here those results are generalized to a geometrical setting where the regions of blood are allowed to be connected. Moreover, asymptotic corrector results are derived.
    Keywords: ddc:000
    Language: English
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  • 3
    Publication Date: 2014-11-10
    Description: Stable multi-sets are an evident generalization of the well-known stable sets. As integer programs, they constitute a general structure which allows for a wide applicability of the results. Moreover, the study of stable multi-sets provides new insights to well-known properties of stable sets. In this paper, we continue our investigations started in [{\sl Koster and Zymolka 2002}] and present results of three types: on the relation to other combinatorial problems, on the polyhedral structure of the stable multi-set polytope, and on the computational impact of the polyhedral results. First of all, we embed stable multi-sets in a framework of generalized set packing problems and point out several relations. The second part discusses properties of the stable multi-set polytope. We show that the vertices of the linear relaxation are half integer and have a special structure. Moreover, we strengthen the conditions for cycle inequalities to be facet defining, show that the separation problem for these inequalities is polynomial time solvable, and discuss the impact of chords in cycles. The last result allows to interpret cliques as cycles with many chords. The paper is completed with a computational study to the practical importance of the cycle inequalities. The computations show that the performance of state-of-the-art integer programming solvers can be improved significantly by including these inequalities.
    Keywords: ddc:000
    Language: English
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  • 4
    Publication Date: 2014-02-26
    Description: In this paper, first solutions of the dust moment equations developed in [{\sl Woitke & Helling 2002}] for the description of dust formation and precipitation in brown dwarf and giant gas planet atmospheres are presented. We consider the special case of a static brown dwarf atmosphere, where dust particles continuously nucleate from the gas phase, grow by the accretion of molecules, settle gravitationally and re-evaporate thermally. Applying a kinetic description of the relevant microphysical and chemical processes for TiO$_2$-grains, the model makes predictions about the large-scale stratification of dust in the atmosphere, the depletion of molecules from the gas phase, the supersaturation of the gas in the atmosphere as well as the mean size and the mass fraction of dust grains as function of depth. Our results suggest that the nucleation occu in the upper atmosphere where the gas is cool, strongly depleted, but nevertheless highly supersaturated ($S\!\gg\!1$). These particles settle gravitationally and populate the warmer layers below, where the in-situ formation (nucleation) is ineffective or even not possible. During their descent, the particles grow up to radii $\approx\!0.3\,\mu{\rm m}\,...\,150\,\mu{\rm m}$, depending gas around the cloud base. The particles finally sink into layers which are sufficiently hot to cause their thermal evaporation. Hence, an effective transport mechanism for condensable elements exi considered solid/liquid material. In the stationary case studied here, this downward directed element transport by precipitating dust grains is balanced by an upward directed flux of condensable elements from the deep interior of the star via convective mixing (no dust without mixing). We find a self-regulation mechanism which leads to an approximate phase equilibrium ($S\!\approx\!1$) around the cloud base. The mass fraction of dust present in the atmosphere results be to approximately given by the mass fraction of condensable elements in the gas being mixed up.
    Keywords: ddc:000
    Language: English
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  • 5
    Publication Date: 2020-03-09
    Description: Analysis of phenomena that simultaneously occur on quite different spatial and temporal scales require adaptive, hierarchical schemes to reduce computational and storage demands. For data represented as grid functions, the key are adaptive, hierarchical, time-dependent grids that resolve spatio-temporal details without too much redundancy. Here, so-called AMR grids gain increasing popularity. For visualization and feature identification/tracking, the underlying continuous function has to be faithfully reconstructed by spatial and temporal interpolation. Well designed interpolation methods yield better results and help to reduce the amount of data to be stored. We address the problem of temporal interpolation of AMR grid data, e.g.\ for creation of smooth animations or feature tracking. Intermediate grid hierarchies are generated by merging the cells on all refinement levels that are present in the key frames considered. Utilizing a clustering algorithm a structure of nested grids is induced on the resulting collection of cells. The grid functions are mapped to the intermediate hierarchy, thus allowing application of appropriate interpolation techniques.
    Keywords: ddc:000
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  • 6
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    Publication Date: 2020-03-09
    Description: An improved general-purpose technique for the visualization of symmetric positive definite tensor fields of rank two is described. It is based on a splatting technique that is built from tiny transparent glyph primitives which are capable to incorporate the full directional information content of a tensor. The result is an information-rich image that allows to read off the preferred directions in a tensor field at each point of a three-dimensional volume or two-dimensional surface. It is useful for analyzing slices or volumes of a three-dimensional tensor field and can be overlayed with standard volume rendering or color mapping. The application of the rendering technique is demonstrated on general relativistic data and the diffusion tensor field of a human brain.
    Keywords: ddc:000
    Language: English
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  • 7
    Publication Date: 2014-11-10
    Description: Graphs with circular symmetry, called webs, are relevant for describing the stable set polytopes of two larger graph classes, quasi-line graphs [{\sl Giles and Trotter 1981, Oriolo 2001}] and claw-free graphs [{\sl Galluccio and Sassano 1997, Giles and Trotter 1981}]. Providing a decent linear description of the stable set polytopes of claw-free graphs is a long-standing problem [{\sl Grötschel, Lov\'asz, and Schrijver 1988}]. However, even the problem of finding all facets of stable set polytopes of webs is open. So far, it is only known that stable set polytopes of webs with clique number $\leq 3$ have rank facets only [{\sl Dahl 1999, Trotter 1975}] while there are examples with clique number $\geq 4$ having non-rank facets [{\sl e.g. Liebling et al. 2003, Oriolo 2001, P\^echer and Wagler 2003}]. In this paper, we provide a construction for non-rank facets of stable set polytopes of webs. We use this construction to prove, for several fixed values of $\omega$ including all odd values at least 5, that there are only finitely many webs with clique number $\omega$ whose stable set polytopes admit rank facets only.
    Keywords: ddc:000
    Language: English
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  • 8
    Publication Date: 2020-11-13
    Description: We present an algorithm that constructs parametrizations of boundary and interface surfaces automatically. Starting with high-resolution triangulated surfaces describing the computational domains, we iteratively simplify the surfaces yielding a coarse approximation of the boundaries with the same topological type. While simplifying we construct a function that is defined on the coarse surface and whose image is the original surface. This function allows access to the correct shape and surface normals of the original surface as well as to any kind of data defined on it. Such information can be used by geometric multigrid solvers doing adaptive mesh refinement. Our algorithm runs stable on all types of input surfaces, including those that describe domains consisting of several materials. We have used our method with success in different fields and we discuss examples from structural mechanics and biomechanics.
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  • 9
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    Publication Date: 2020-08-05
    Description: This article investigates a certain class of combinatorial packing problems and some polyhedral relations between such problems and the set packing problem.
    Keywords: ddc:000
    Language: English
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  • 10
    Publication Date: 2014-02-26
    Description: We construct non-constructible simplicial $d$-spheres with $d+10$ vertices and non-constructible, non-realizable simplicial $d$-balls with $d+9$ vertices for $d\geq 3$.
    Keywords: ddc:000
    Language: English
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  • 11
    Publication Date: 2014-11-11
    Description: We consider the problem of designing a network that employs a non-bifurcated shortest path routing protocol. The network's nodes and the set of potential links are given together with a set of forecasted end-to-end traffic demands. All relevant hardware components installable at links or nodes are considered. The goal is to simultaneously choose the network's topology, to decide which hardware components to install on which links and nodes, and to find appropriate routing weights such that the overall network cost is minimized. In this paper, we present a mathematical optimization model for this problem and an algorithmic solution approach based on a Lagrangian relaxation. Computational results achieved with this approach for several real-world network planning problems are reported.
    Keywords: ddc:000
    Language: English
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  • 12
    Publication Date: 2014-02-26
    Description: We investigate the impact of link and path restoration on the cost of telecommunication networks. The surprising result is the following: the cost of an optimal network configuration is almost independent of the restoration concept if (i) the installation of network elements (ADMs, DXCs, or routers) and interface cards, (ii) link capacities, and (iii) working and restoration routings are simultaneously optimized. We present a mixed-integer programming model which integrates all these decisions. Using a branch-and-cut algorithm (with column generation to deal with all potential routing paths), we solve structurally different real-world problem instances and show that the cost of optimal solutions is almost independent of the used restoration concept. In addition, we optimize spare capacities for given shortest working paths which are predetermined with respect to different link metrics. In comparison to simultaneous optimization of working and restoration routings, it turns out that this approach does not allow to obtain predictably good results.
    Keywords: ddc:000
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  • 13
    Publication Date: 2020-11-13
    Description: In the dial-a-ride-problem (DARP) objects have to be moved between given sources and destinations in a transportation network by means of a server. The goal is to find a shortest transportation for the server. We study the DARP when the underlying transportation network forms a caterpillar. This special case is strongly NP-hard in the worst case. We prove that in a probabilistic setting there exists a polynomial time algorithm which almost surely finds an optimal solution. Moreover, with high probability the optimality of the solution found can be certified efficiently. We also examine the complexity of the DARP in a semi-random setting and in the unweighted case.
    Keywords: ddc:000
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  • 14
    Publication Date: 2019-01-29
    Description: The paper presents a new affine invariant theory on asymptotic mesh independence of Newton's method in nonlinear PDEs. Compared to earlier attempts, the new approach is both much simpler and more natural from the algorithmic point of view. The theory is exemplified at collocation methods for ODE boundary value problems and at finite element methods for elliptic PDE problems.
    Keywords: ddc:000
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  • 15
    Publication Date: 2014-02-26
    Description: In this paper we introduce the notion of smoothed competitive analysis of online algorithms. Smoothed analysis has been proposed by [{\sl Spielman and Teng} STOC 2001] to explain the behaviour of algorithms that work well in practice while performing very poorly from a worst case analysis point of view. We apply this notion to analyze the Multi-Level Feedback (MLF) algorithm to minimize the total flow time on a sequence of jobs released over time when the processing time of a job is only known at time of completion. The initial processing times are integers in the range $[1,2^K]$. We use a partial bit randomization model, where the initial processing times are smoothened by changing the $k$ least significant bits under a quite general class of probability distributions. We show that MLF admits a smoothed competitive ratio of $O(max((2^k/\sigma)^3, (2^k/\sigma)^2 2^K-k))$, where $\sigma$ denotes the standard deviation of the distribution. In particular, we obtain a competitive ratio of $O(2^K-k)$ if $\sigma = \Theta(2^k)$. %The analysis holds for an oblivious as well as for a stronger adaptive %adversary. We also prove an $\Omega(2^{K-k})$ lower bound for any deterministic algorithm that is run on processing times smoothened according to the partial bit randomization model. For various other smoothening models, including the additive symmetric smoothening model used by [{\sl Spielman and Teng}], we give a higher lower bound of $\Omega(2^K)$. A direct consequence of our result is also the first average case analysis of MLF. We show a constant expected ratio of the total flow time of MLF to the optimum under several distributions including the uniform distribution.
    Keywords: ddc:000
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  • 16
    Publication Date: 2014-11-11
    Description: For the general G/G/1 processor sharing (PS) system a sample path result for the sojourn times in a busy period is proved, which yields a relation between the sojourn times under PS and FCFS discipline. In particular, the result provides a formula for the mean sojourn time in G/D/1-PS in terms of the mean sojourn time in the corresponding G/D/1-FCFS, generalizing known results for GI/M/1 and M/GI/1. Extensions of the formula provide the basis for a two-moment approximation of the mean sojourn time in G/GI/1-PS in terms of a related G/D/1-FCFS.
    Keywords: ddc:000
    Language: English
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  • 17
    Publication Date: 2014-02-26
    Description: The paper surveys recent progress in the mathematical modelling and simulation of essential molecular dynamics. Particular emphasis is put on computational drug design wherein time scales of $msec$ up to $min$ play the dominant role. Classical long-term molecular dynamics computations, however, would run into ill-conditioned initial value problems already after time spans of only $psec=10^{-12} sec$. Therefore, in order to obtain results for times of pharmaceutical interest, a combined deterministic-stochastic model is needed. The concept advocated in this paper is the direct identification of metastable conformations together with their life times and their transition patterns. It can be interpreted as a {\em transfer operator} approach corresponding to some underlying hybrid Monte Carlo process, wherein short-term trajectories enter. Once this operator has been discretized, which is a hard problem of its own, a stochastic matrix arises. This matrix is then treated by {\em Perron cluster analysis}, a recently developed cluster analysis method involving the numerical solution of an eigenproblem for a Perron cluster of eigenvalues. In order to avoid the 'curse of dimension', the construction of appropriate boxes for the spatial discretization of the Markov operator requires careful consideration. As a biomolecular example we present a rather recent SARS protease inhibitor.
    Keywords: ddc:000
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  • 18
    Publication Date: 2021-02-01
    Description: The operative planning problem in natural gas distribution networks is addressed. An optimization model focusing on the governing PDE and other nonlinear aspects is presented together with a suitable discretization for transient optimization in large networks by SQP methods. Computational results for a range of related dynamic test problems demonstrate the viability of the approach.
    Keywords: ddc:000
    Language: English
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  • 19
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    Publication Date: 2014-02-26
    Description: This article presents a new computational approach to the three-dimensional (3D) modeling of ribonucleic acid (RNA) sequences with unknown spatial structure. The main concept is a mapping of the query sequence onto the 3D structures of a suitable template RNA molecule. This technique called \textit{threading} has originally been developed for the modeling of protein 3D structures. The application to RNA systems bridges the information gap between the growing mass of RNA sequence data and the relatively limited number of available 3D structures. The new RNA threading method is demonstrated on a tRNA model system because sufficient representative 3D structures have experimentally been elucidated and deposited in the public databases. Nevertheless, the method is in principle transferable on all other RNA species. Algorithms are developed that decompose these template structures into their secondary structure elements and gather this information in a specific template database. The best template is chosen with public alignment and secondary structure prediction tools which are integrated in the RNA modeling module. The structural information gathered from the template and the best alignment is combined to establish a comprehensive 3D model of the query sequence. A range of complete tRNA structures has successfully been modeled with the RNA threading method. The prototype module visualizes the models and provides convenient access to the proposed 3D structures. Therefore, the method could give new insight into a variety of RNA systems which in the recent years have become increasingly important as potential new pharmaceutical agents.
    Keywords: ddc:000
    Language: English
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  • 20
    Publication Date: 2014-02-26
    Description: Collection of abstracts of the Korean-German Bilateral Symposium on Scientific Computing, Berlin January 15/16, 2004
    Keywords: ddc:000
    Language: English
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  • 21
    Publication Date: 2014-11-11
    Description: Beim Entwurf und Ausbau von Informations- und Kommunikationsnetzwerken m{ü}ssen zahlreiche interdependente Entscheidungen getroffen und gleichzeitig mannigfaltige Bedingungen ber{ü}cksichtigt werden. Die verf{ü}gbaren technischen und organisatorischen Alternativm{ö}glichkeiten sind normalerweise so vielf{ä}ltig und komplex, dass eine manuelle Planung praktisch nicht m{ö}glich ist. In diesem Artikel wird das Potential und die Methodik der mathematischen Optimierung bei der kostenoptimalen Planung von Kommunikationsnetzen vorgestellt. Als Ausgangspunkt wird exemplarisch eine typische praktische Aufgabe, die Struktur- und Konfigurationsplanung mehrstufiger Telekommunikationsnetzwerke, dargestellt. Anschließend werden kurz die wesentlichen Modellierungstechniken und Verfahrensans{ä}tze der mathematischen Optimierung skizziert. Abschließend gehen wir auf die Planung einer ad{ä}quaten Informations- und Kommunikations- Infrastruktur f{ü}r ein dezentrales Energieversorgungsnetz ein.
    Keywords: ddc:000
    Language: German
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  • 22
    Publication Date: 2020-08-05
    Description: Point-to-Multipoint systems are one kind of radio systems supplying wireless access to voice/data communication networks. Such systems have to be run using a certain frequency spectrum, which typically causes capacity problems. Hence it is, on the one hand, necessary to reuse frequencies but, on the other hand, no interference must be caused thereby. This leads to the bandwidth allocation problem, a special case of so-called chromatic scheduling problems. Both problems are NP-hard, and there exist no polynomial time approximation algorithms with a guaranteed quality. One kind of algorithms which turned out to be successful for many other combinatorial optimization problems uses cutting plane methods. In order to apply such methods, knowledge on the associated polytopes is required. The present paper contributes to this issue, exploring basic properties of chromatic scheduling polytopes and several classes of facet-defining inequalities.
    Keywords: ddc:000
    Language: English
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  • 23
    Publication Date: 2020-02-11
    Description: The UMTS radio network planning problem poses the challenge of designing a cost-effective network that provides users with sufficient coverage and capacity. We describe an optimization model for this problem that is based on comprehensive planning data of the EU project MOMENTUM. We present heuristic mathematical methods for this realistic model, including computational results.
    Keywords: ddc:000
    Language: English
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  • 24
    Publication Date: 2014-02-26
    Description: Relaying -- allowing multiple wireless hops -- is a protocol extension for cellular networks conceived to improve data throughput. Its benefits have only been quantified for small example networks. For assessing its general potential, we define a complex resource allocation\slash{}scheduling problem. Several mathematical models are presented for this problem; while a time-expanded MIP approach turns out intractable, a sophisticated column generation scheme leads to good computational results. We thereby show that for selected cases relaying can increase data throughput by 30\% on the average.
    Keywords: ddc:000
    Language: English
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  • 25
    Publication Date: 2014-02-26
    Description: Finding conflict-free wavelength assignments with a minimum number of required conversions for a routing of the lightpaths is one of the important tasks within the design of all-optical networks. We consider this problem in multi-fiber networks with different types of WDM systems. We give a detailed description of the problem and derive its theoretical complexity. For practical application, we propose several sequential algorithms to compute appropriate wavelength assignments. We also perform computational experiments to evaluate their performance. For the iterative algorithms, we identify characteristic patterns of progression. Two of these algorithms qualify for application in practice.
    Keywords: ddc:000
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  • 26
    Publication Date: 2014-09-30
    Description: A recently developed algorithm allows Rigid Body Docking of ligands to proteins, regardless of the accessibility and location of the binding site. The Docking procedure is divided into three subsequent optimization phases, two of which utilize rigid body dynamics. The last one is applied with the ligand already positioned inside the binding pocket and accounts for full flexibility. Initially, a combination of geometrical and force-field based methods is used as a Coarse Docking strategy, considering only Lennard-Jones interactions between the target and pharmaceutically relevant atoms or functional groups. The protein is subjected to a Hot Spot Analysis, which reveals points of high affinity in the protein environment towards these groups. The hot spots are distributed into different subsets according to their group affiliation. The ligand is described as a complementary point set, consisting of the same subsets. Both sets are matched in $\mathrm{I\!R}^{3}$, by superimposing members of the same subsets. In the first instance, steric inhibition is nearly neglected, preventing the system's trajectory from trapping in local minima and thus from finding false positive solutions. Hence the exact location of the binding site can be determined fast and reliably without any additional information. Subsequently, errors resulting from approximations are minimized via finetuning, this time considering both Lennard-Jones and Coulomb forces. Finally, the potential energy of the whole complex is minimized. In a first evaluation, results are rated by a reduced scoring function considering only noncovalent interaction energies. Exemplary Screening results will be given for specific ligands.
    Keywords: ddc:000
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  • 27
    Publication Date: 2014-02-26
    Description: We suggest a new model for the design of telecommunication networks which integrates decisions about the topology, configuration of the switching hardware, link dimensioning, and protected routing of communication demands. Applying the branch-and-cut-algorithm implemented in our network planning and optimization tool DISCNET, we demonstrate that real-world based network planning instances of such an enhanced model can be solved.
    Keywords: ddc:000
    Language: English
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  • 28
    Publication Date: 2020-02-11
    Description: Dieser Bericht beschreibt die Erfahrungen und Schlussfolgerungen,die im Rahmen der VDS-Vorstudie bei der Speicherung der vom Friedrich-Althoff-Konsortium lizenzierten Zeitschriften des Kluwer-Verlages gewonnen wurden.
    Keywords: ddc:000
    Language: German
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  • 29
    Publication Date: 2020-11-13
    Description: Der KOBV setzt für die endnutzerbasierte Online-Fernleihe den Sisis ZFL-Server (Zentraler Fernleih-Server) ein. Mit dem Einsatz des ZFL-Servers können in den Bibliotheken echte Rationalisierungseffekte erzielt werden: Der Server ist in der Lage, Fernleih-Bestellungen an lokale Systeme zu übergeben, so dass sie im lokalen System automatisch - ohne Eingreifen von Bibliotheksmitarbeitern - weiterverarbeitet werden können. Im KOBV können derzeit Sisis- und Aleph-Lokalsysteme diese Schnittstelle voll bedienen. Andere Bibliothekssysteme im KOBV, die diese Schnittstelle nicht bedienen können, werden mittels eines E-Mail-Verfahrens in die Online-Fernleihe integriert. Die vorliegende Kurzbeschreibung der Online-Fernleihe im KOBV soll - im Gegensatz zur Spezifikation, die möglichst vollständig sein sollte - einen leicht verständlichen Einblick in die Abläufe der Online-Fernleihe vermitteln. Nach einem Überblick über zu erwartende Rationalisierungseffekte ist der Ablauf einer Online-Fernleih-Bestellung - veranschaulicht durch eine Graphik mit dem technischen Aufbau im KOBV - kurz dargestellt. \vspace{6mm} {\it Hinweis:} Die von einer Arbeitsgruppe des KOBV erstellte Spezifikation zur Online-Fernleihe ist als ZIB Report 02-30 auf dem Preprint-Server des ZIB veröffentlicht. Siehe: Monika Kuberek (Red.) {\begin{rawhtml} 〈a href="http://www.zib.de/Publications/Reports/ZR-02-30.pdf"〉 〈i〉 Spezifikation für eine Verbund-Fernleih-Software im KOBV〈/i〉 〈/a〉 \end{rawhtml}}
    Keywords: ddc:000
    Language: German
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  • 30
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    Publication Date: 2014-02-26
    Description: The problem of clustering data can often be transformed into the problem of finding a hidden block diagonal structure in a stochastic matrix. Deuflhard et al. have proposed an algorithm that state s the number $k$ of clusters and uses the sign structure of $k$ eigenvectors of the stochastic matrix to solve the cluster problem. Recently Weber and Galliat discovered that this system of eigenvectors can easily be transformed into a system of $k$ membership functions or soft characteristic functions describing the clusters. In this article we explain the corresponding cluster algorithm and point out the underlying theory. By means of numerical examples we explain how the grade of membership can be interpreted.
    Keywords: ddc:000
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  • 31
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    Publication Date: 2014-02-26
    Description: Mit der Entwicklung des KOBV-Informationsportals soll den Benutzern in der Region Berlin-Brandenburg ein verbesserter Zugang zu Informationsressourcen geboten werden. Einen wesentlichen Anteil diese Auf der Grundlage der Analyse der Rahmenbedingungen werden Anforderungen an die Zugriffskontrolle im KOBV definiert und Lösungsmöglichkeiten auf der Ebene allgemeiner Modelle diskutiert.
    Keywords: ddc:000
    Language: German
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  • 32
    Publication Date: 2014-02-26
    Description: The KOBV Informationsportal aims to be a universal gateway to the sources of information hosted by the partner libraries from the Berlin-Brandenburg area. Due to the large number of these sources, an intuitive navigation is an essential component of the portal. The navigation-component should preserve the partner libraries? independence and overcome their administrative and technical differences. This paper proposes a collection-level navigation with four dimensions: the sources? subject areas (e.g. the first two levels of DDC), the sources? type (e.g. e-journals, databases, OPACs, etc.), the sources? location (e.g. Berlin, Brandenburg) / the library that hosts that source and the sources? accessing state (e.g. free, restricted, etc.).
    Keywords: ddc:000
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  • 33
    Publication Date: 2014-02-26
    Description: Our main result is that every n-dimensional polytope can be described by at most (2n-1) polynomial inequalities and, moreover, these polynomials can explicitly be constructed. For an n-dimensional pointed polyhedral cone we prove the bound 2n-2 and for arbitrary polyhedra we get a constructible representation by 2n polynomial inequalities.
    Keywords: ddc:000
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  • 34
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    Publication Date: 2020-02-11
    Description: The NETLIB has now served for 18 years as a repository of LP problem instances. From the beginning to the present day there was some uncertainness about the precise values of the optimal solutions. We implemented a program using exact rational arithmetic to compute proofs for the feasibility and optimality of an LP solution. This paper reports the \emph{exact} optimal objective values for all NETLIB problems.
    Keywords: ddc:000
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  • 35
    Publication Date: 2014-02-26
    Description: Based on the knowledge gained from direct numerical simulations which are only possible in the microscale regime, a concept of driven turbulence is presented which allows to enter the mesoscopic scale regime. Here, dust formation under stochastic hydro- and thermodynamic conditions is studied: constructively superimposed stochastic waves initiate dust formation by the creation of singular nucleation events. It, hence, results a varying mean grain size and dust density in space and time. The newly formed dust changes the thermodynamic behavior from almost isotherm to adiabatic and chemically depletes the gas phase.
    Keywords: ddc:000
    Language: English
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  • 36
    Publication Date: 2014-11-11
    Description: Der scharfe Wettbewerb innerhalb der Telekommunikationsbranche zwingt die Netzbetreiber dazu, ihre Investitionen genau zu planen und immer wieder Einsparungsmanahmen durchzuführen. Gleichzeitig ist es jedoch wichtig, die Qualität der angebotenen Dienste zu verbessern, um neue Kunden zu gewinnen und langfristig an sich zu binden. Die mathematische Optimierung bietet sich für viele solcher Aufgabenstellungen als hervorragend geeignetes Planungswerkzeug an. Ziel dieses Artikels ist es, ihre Methodik und ihre Anwendung speziell zur Kosten- und Qualitätsoptimierung in Kommunikationsnetzen vorzustellen. Anhand von vier konkreten Planungsaufgaben aus dem Bereich der Festnetzplanung wird aufgezeigt, wie sich komplexe Zusammenhänge in flexiblen mathematischen Modellen abbilden lassen und welche Verfahren zur automatisierten Bearbeitung der Probleme eingesetzt werden können. Die hier vorgestellten Methoden zeichnen sich insbesondere dadurch aus, dass sie neben hochwertigen Lösungen auch eine Qualittsgarantie liefern, mit der sich die Lsungen fundiert bewerten lassen. Die dokumentierten Ergebnisse aus verschiedenen Industrieprojekten belegen die Eignung und Güte der mathematischen Optimierung für die Praxis.
    Keywords: ddc:000
    Language: German
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  • 37
    Publication Date: 2014-02-26
    Description: Dust formation {in brown dwarf atmospheres} is studied by utilizing a model for driven turbulence in the mesoscopic scale regime. We apply a pseudo-spectral method where waves are created and superimposed {within} a {limited} wavenumber interval. The turbulent kinetic energy distribution follows the Kolmogoroff spectrum which is assumed to be the most likely value. Such superimposed, stochastic waves may occur in a convectively active environment. They cause nucleation fronts and nucleation events and thereby initiate the dust formation process which { continues until} all condensible material is consumed. Small disturbances {are found to} have a large impact on the dust forming system. An initially dust-hostile region, which may originally be optically thin, becomes optically thick in a patchy way showing considerable variations in the dust properties during the formation process. The dust appears in lanes and curls as a result of the interaction with waves, i.e. turbulence, which form larger and larger structures with time. Aiming on a physical understanding of the variability of brown dwarfs, related to structure formation in substellar atmospheres, we work out first necessary criteria for small-scale closure models to be applied in macroscopic simulations of dust forming astrophysical systems.
    Keywords: ddc:000
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  • 38
    Publication Date: 2014-02-26
    Description: Substellar atmospheres are observed to be irregularly variable for which the formation of dust clouds is the most promising candidate explanation. The atmospheric gas is convectively unstable and, last but not least, colliding convective cells are seen as cause for a turbulent fluid field. Since dust formation depends on the local properties of the fluid, turbulence influences the dust formation process and may even allow the dust formation in an initially dust-hostile gas. A regime-wise investigation of dust forming substellar atmospheric situations reveals that the largest scales are determined by the interplay between gravitational settling and convective replenishment which results in a dust-stratified atmosphere. The regime of small scales is determined by the interaction of turbulent fluctuations. Resulting lane-like and curled dust distributions combine to larger and larger structures. We compile necessary criteria for a subgrid model in the frame of large scale simulations as result of our study on small scale turbulence in dust forming gases.
    Keywords: ddc:000
    Language: English
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  • 39
    Publication Date: 2019-01-24
    Description: The solution of scattering problems described by the Helmholtz equation on unbounded domains is of importance for a wide variety of applications, for example in electromagnetics and acoustics. An implementation of a solver for scattering problems based on the programming language Matlab is introduced. The solver relies on the finite-element-method and on the perfectly-matched-layer-method, which allows for the simulation of scattering problems on complex geometries surrounded by inhomogeneous exterior domains. This report gives a number of detailed examples and can be understood as a user manual to the freely accessible code of the solver HelmPole.
    Keywords: ddc:000
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  • 40
    Publication Date: 2020-03-09
    Description: \noindent The size of data sets produced on remote supercomputer facilities frequently exceeds the processing capabilities of local visualization workstations. This phenomenon increasingly limits scientists when analyzing results of large-scale scientific simulations. That problem gets even more prominent in scientific collaborations, spanning large virtual organizations, working on common shared sets of data distributed in Grid environments. In the visualization community, this problem is addressed by distributing the visualization pipeline. In particular, early stages of the pipeline are executed on resources closer to the initial (remote) locations of the data sets. \noindent This paper presents an efficient technique for placing the first two stages of the visualization pipeline (data access and data filter) onto remote resources. This is realized by exploiting the ``extended retrieve'' feature of GridFTP for flexible, high performance access to very large HDF5 files. We reduce the number of network transactions for filtering operations by utilizing a server side data processing plugin, and hence reduce latency overhead compared to GridFTP partial file access. The paper further describes the application of hierarchical rendering techniques on remote uniform data sets, which make use of the remote data filtering stage.
    Keywords: ddc:000
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  • 41
    Publication Date: 2014-02-26
    Description: Relaying is a protocol extension for cellular wireless computer networks; in order to utilize radio resources more efficiently, several hops are allowed within one cell. This paper investigates the principle potential of relaying by casting transmission scheduling as a mathematical optimization problem, namely, a linear program. We analyze the throughput gains showing that, irrespective of the concrete scheduling algorithm, performance gains of up to 30\% on average for concrete example networks are achievable.
    Keywords: ddc:000
    Language: English
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  • 42
    Publication Date: 2014-02-26
    Description: We call an edge $e$ of a perfect graph $G$ critical if $G-e$ is imperfect and call $e$ anticritical if $G+e$ is imperfect. The present paper surveys several questions in this context. We ask in which perfect graphs critical and anticritical edges occur and how to detect such edges. The main result by [{\sl Wagler, PhD thesis 2000}] shows that a graph does not admit any critical edge if and only if it is Meyniel. The goal is to order the edges resp.~non-edges of certain perfect graphs s.t. deleting resp.~adding all edges in this order yields a sequence of perfect graphs only. Results of [{\sl Hayward 1985}] and [{\sl Spinrad & Sritharan 1995}] show the existence of such edge orders for weakly triangulated graphs; the line-perfect graphs are precisely these graphs where all edge orders are perfect [{\sl Wagler 2001}]. Such edge orders cannot exist for every subclass of perfect graphs that contains critically resp.~anticritically perfect graphs where deleting resp.~adding an arbitrary edge yields an imperfect graph. We present several examples and properties of such graphs, discuss constructions and characterizations from [{\sl Wagler 1999, Wagler PhD thesis 2000}]. An application of the concept of critically and anticritically perfect graphs is a result due to [{\sl Hougardy & Wagler 2002}] showing that perfectness is an elusive graph property.
    Keywords: ddc:000
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  • 43
    Publication Date: 2014-02-26
    Description: Hasenbusch has proposed splitting the pseudo-fermionic action into two parts, in order to speed-up Hybrid Monte Carlo simulations of QCD. We have tested a different splitting, also using clover-improved Wilson fermions. An additional speed-up between 5 and 20\% over the original proposal was achieved in production runs.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 44
    Publication Date: 2014-11-10
    Description: A set of vertices $S\subseteq V$ is called a safe separator for treewidth, if $S$ is a separator of $G$, and the treewidth of $G$ equals the maximum of the treewidth over all connected components $W$ of $G-S$ of the graph, obtained by making $S$ a clique in the subgraph of $G$, induced by $W\cup S$. We show that such safe separators are a very powerful tool for preprocessing graphs when we want to compute their treewidth. We give several sufficient conditions for separators to be safe, allowing such separators, if existing, to be found in polynomial time. In particular, every minimal separator of size one or two is safe, every minimal separator of size three that does not split off a component with only one vertex is safe, and every minimal separator that is an almost clique is safe; an almost clique is a set of vertices $W$ such that there is a $v\in W$ with $W-\{v\}$ a clique. We report on experiments that show significant reductions of instance sizes for graphs from proba! bilistic networks and frequency assignment.
    Keywords: ddc:000
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  • 45
    Publication Date: 2019-01-29
    Description: A primal-dual interior point method for optimal control problems is considered. The algorithm is directly applied to the infinite dimensional problem. Existence and convergence of the central path are analyzed, and linear convergence of a short step pathfollowing method is established.
    Keywords: ddc:000
    Language: English
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  • 46
    Publication Date: 2014-02-26
    Description: We explicitly construct small triangulations for a number of well-known $3$-dimensional manifolds and give a brief outline of some aspects of the underlying theory of $3$-manifolds and its historical development.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 47
    Publication Date: 2016-06-30
    Description: Peer-to-Peer (P2P) Systeme werden u.a. zur Verwaltung von großen Datenmengen benutzt, die auf verschiedene Rechner verteilt sind. Benutzern soll damit der Zugriff auf Daten innerhalb des Systems leicht ermöglicht werden. Damit in P2P Systemen die Daten effizient verteilt und gesucht werden können, existieren Distributed Hash Tables. Distributed Hash Tables (DHT) sind eine Methode, um globale Informationen persistent speichern zu können. Der Wertebereich der Hashfunktion, welche die zu veröffentlichenden Einträge auf Werte abbildet, wird in Abschnitte aufgeteilt, die einzelnen Knoten zugeteilt werden. Die meisten DHTs haben aber ein Problem bei der Verteilung der Last. Die verschiedenen DHT Systeme beruhen meist auf einem identischen Ansatz der Lastverteilung. Die Last wird nur mit Hilfe einer Hashfunktion verteilt. Es wird davon ausgegangen, dass diese Funktion die Last gleichmäßig verteilt. Im Rahmen dieser Arbeit wurde ein Verfahren zur Last Verteilung entwickelt, simuliert und implementiert. Bei dem Verfahren wird die Last wie bei der Verteilung von Wärme an die Umgebung abgegeben. Es wird mit existierenden Lastbalancierungsalgorithmen verglichen. Mit diesem neuen Verfahren ist es möglich, Last in DHTs besser zu verteilen ohne große Änderungen an den DHTs vorzunehmen. Es wird gezeigt, wie mit dem Verfahren zusätzlich die Fehlertoleranz des P2P Systems erhöht werden kann.
    Description: One of the many uses of Peer-to-Peer (P2P) systems is the administration of large data sets that are distributed across different computers, with the goal of facilitating user access to files within the system. Distributed Hash Tables (DHT) are designed to enable the efficient distribution and search of files, by allowing global information to be persistently stored. The range of values of the hash function (the possible entries in the published hash table) are assigned to individual nodes. Most DHTs, however, have a problem with load distribution. The various DHT systems usually operate by distributing load equally among nodes. Thus the load is distributed using the help of the hash function. One assumes this function distributes the load evenly. In the context of this work a method of distributing load has been developed, simulated and implemented. With this method load is transferred in a fashion analogous to the dissipation of heat into the environment. Comparisons with existing algorithms for load balancing are drawn. With the new procedure it is possible to better distribute load in DHTs without requiring major changes to the DHTs themselves. It is shown that with the procedure the fault tolerance of P2P systems may also be increased.
    Keywords: ddc:000
    Language: German
    Type: masterthesis , doc-type:masterThesis
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  • 48
    Publication Date: 2014-02-26
    Description: The key to molecular conformation dynamics is the direct identification of metastable conformations, which are almost invariant sets of molecular dynamical systems. Once some reversible Markov operator has been discretized, a generalized symmetric stochastic matrix arises. This matrix can be treated by Perron cluster analysis, a rather recent method involving a Perron cluster eigenproblem. The paper presents an improved Perron cluster analysis algorithm, which is more robust than earlier suggestions. Numerical examples are included.
    Keywords: ddc:000
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  • 49
    Publication Date: 2014-11-11
    Description: In this paper, a new shared protection mechanism for meshed optical networks is presented. Significant network design cost reductions can be achieved in comparison to the well-known 1+1 protection scheme. Demand-wise Shared Protection (DSP) bases on the diversification of demand routings and exploits the network connectivity to restrict the number of backup lightpaths needed to provide the desired level of prorection. Computational experiments approve the benefits of the concept DSP for cost efficient optical network designs.
    Keywords: ddc:000
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  • 50
    Publication Date: 2019-05-10
    Description: The correlation of the inner architecture of bone and its functional loading was already stated by Wolff in 1892. Our objective is to demonstrate this interdependence in the case of the human mandible. For this purpose, stress/strain profiles occuring at a human lateral bite were simulated. Additionally, by a combination of computer graphics modules, a three--dimensional volumetric visualization of bone mineral density could be given. Qualitative correspondences between the density profile of the jaw and the simulated stress/strain profiles could be pointed out. In the long run, this might enable the use of the simulation for diagnosis and prognosis. The solution of the underlying partial differential equations describing linear elastic material behaviour was provided by an adaptive finite element method. Estimates of the discretization errors, local grid refinement, and multilevel techniques guaranteed the reliability and efficiency of the method.
    Keywords: ddc:000
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  • 51
    Publication Date: 2014-02-26
    Description: UMTS is a 3rd generation mobile telecommunication system which enables multi-service and multi-bit rate communication going beyond the possibilities of previous systems. The simulator MoDySim models UMTS in great detail. Characteristics of UMTS such as soft hand-over and the interdependency of load and capacity among neighbouring cells are challenges for the parallelisation of such a system. In this paper we explain how the software was parallelised and present performance results of a UMTS simulation for the city of Berlin.
    Keywords: ddc:000
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  • 52
    Publication Date: 2014-02-26
    Description: We report on a numerical reinvestigation of the Aoki phase in lattice QCD with two flavors of Wilson fermions where the parity-flavor symmetry is spontaneously broken. For this purpose the Hybrid Monte Carlo algorithm was used and an explicit symmetry-breaking source term $h\bar{\psi} i \gamma_{5} \tau^{3}\psi$ was added to the Wilson fermion action. The order parameter $\langle\bar{\psi}i\gamma_{5}\tau^{3}\psi\rangle$ was studied at several values of $(\beta,\kappa,h)$ on lattices of sizes $4^4$ to $12^4$. Our largest lattices can be considered as infintely large allowing to extrapolate to $h=0$. The existence of a parity-flavor-breaking phase can be confirmed at $\beta=4.0$ and $\beta=4.3$ while we find no sign of parity-flavor-breaking at $\beta=4.6$ and $\beta=5.0$.
    Keywords: ddc:000
    Language: English
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  • 53
    Publication Date: 2014-02-26
    Description: In this paper we interpret clustering as a mapping of data into a simplex. If the data itself has simplicial struture this mapping becomes linear. Spectral analysis is an often used tool for clustering data. We will show that corresponding singular vectors or eigenvectors comprise simplicial structure. Therefore they lead to a cluster algorithm, which consists of a simple linear mapping. An example for this kind of algorithms is the Perron cluster analysis (PCCA). We have applied it in practice to identify metastable sets of molecular dynamical systems. In contrast to other algorithms, this kind of approach provides an a priori criterion to determine the number of clusters. In this paper we extend the ideas to more general problems like clustering of bipartite graphs.
    Keywords: ddc:000
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  • 54
    Publication Date: 2016-06-09
    Keywords: ddc:000
    Language: German
    Type: masterthesis , doc-type:masterThesis
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  • 55
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    Publication Date: 2019-10-24
    Keywords: ddc:000
    Language: German
    Type: annualzib , doc-type:report
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  • 56
    Publication Date: 2022-04-11
    Description: The Web of the future will provide a huge amount of information. We need better ways for dealing with and managing the information. A qualified semantic annotation of the information plays a key role for the Web of the future. This article gives an overview about the efforts of the mathematical community to build up a distributed and open information and communication system for mathematics: the Math-Net. The Math-Net Initiative has developed metadata schemas for some classes of Web resources which are relevant in mathematics. Math-Net Services process this information and enable the user to efficiently search and access the information.
    Keywords: ddc:000
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  • 57
    Publication Date: 2022-07-07
    Description: In this paper we propose a new finite element realization of the Perfectly Matched Layer method (PML-method). Our approach allows to deal with arbitrary shaped polygonal domains and with certain types of inhomogeneous exterior domains. Among the covered inhomogeneities are open waveguide structures playing an essential role in integrated optics. We give a detailed insight to implementation aspects. Numerical examples show exponential convergence behavior to the exact solution with the thickness of the PML sponge layer.
    Keywords: ddc:000
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  • 58
    ISSN: 1530-0358
    Keywords: MRI ; Ischiorectal abscess ; Pelvirectal abscess
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract PURPOSE: We evaluated the usefulness of magnetic resonance imaging for the preoperative diagnosis of deep anorectal abscesses. METHODS: Subjects were 21 patients with deep anorectal abscesses. Deep anorectal abscesses were classified into two types, ischiorectal and pelvirectal, according to their location. Patients were also classified into a single abscess group, which showed either an ischiorectal or pelvirectal abscess, and a double abscess group, which showed both ischiorectal and pelvirectal abscesses. The final diagnosis was made from surgical findings, and the types of deep anorectal abscesses determined by digital examination and magnetic resonance imaging were compared. RESULTS: Sensitivity of ischiorectal abscesses (20 lesions) with digital examination and magnetic resonance imaging was 75 and 95 percent, respectively, and that of pelvirectal abscesses (10 lesions) with digital examination and magnetic resonance imaging was 60 and 70 percent, respectively. Sensitivity of the magnetic resonance imaging was significantly higher than that of digital examination in ischiorectal abscesses. Diagnostic accuracy of digital examination and magnetic resonance imaging were both 83 percent in the single abscess group (12 patients), whereas in the double abscess group (9 patients) it was 22 and 78 percent, respectively. The rate of accurate diagnosis of magnetic resonance imaging compared with digital examination in the double abscess group was significantly higher than that in the single abscess group. CONCLUSION: Magnetic resonance imaging was useful for diagnosing and differentiating ischiorectal and pelvirectal abscesses.
    Type of Medium: Electronic Resource
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  • 59
    Electronic Resource
    Electronic Resource
    Springer
    Circuits, systems and signal processing 19 (2000), S. 267-278 
    ISSN: 1531-5878
    Keywords: MRI ; spectroscopic imaging ; sample selection ; k-space ; hexagonal sampling ; reconstruction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Certain types of magnetic resonance imaging (MRI) such as magnetic resonance spectroscopic imaging and three-dimensional (3D) MRI require a great deal of time to acquire the image data. The acquisition time can be reduced if the image has a limited region of support, such as when imaging the brain or a cross section of the chest. Hexagonal sampling of the spatial frequency-domain (k-space) yields a 13.4% sampling density reduction compared to rectangular sampling of thek-space for images with a circular region of support (ROS) without incurring spatial aliasing in the reconstructed image. However, certain nonuniform sampling patterns are more efficient than hexagonal sampling for the same ROS. Sequential backward selection (SBS) has been used in previous work to optimize a nonuniform set ofk-space samples selected from a rectangular grid. To reduce the selection time, we present SBS of samples from a hexagonal grid. A Smith normal decomposition is used to transform the nonrectangular 2D discrete Fourier transform to a standard rectangular 2D fast Fourier transform so that the spatial-domain samples are represented directly on a rectangular grid without interpolation. The hexagonal grid allows the SBS algorithm to begin with a smaller set of candidate samples so that fewer samples have to be eliminated. Simulation results show that a significantly reduced selection time can be achieved with the proposed method in comparison with SBS on a rectangular grid.
    Type of Medium: Electronic Resource
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  • 60
    Electronic Resource
    Electronic Resource
    Springer
    Trauma und Berufskrankheit 2 (2000), S. 249-254 
    ISSN: 1436-6274
    Keywords: Schlüsselwörter ; Schultergelenk ; Basisdiagnostik ; Röntgendiagnostik ; Sonographie ; Computertomographie ; Kernspintomographie ; Arthrographie ; Keywords ; Shoulder joint ; Basic diagnosis ; X-rays ; Sonography ; Computed tomography ; MRI ; Arthrography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: It is its ball-and-socket anatomy that makes the shoulder joint the most flexible of all human joints. This high degree of freedom of movement means, however, on the one hand that early degenerative damage is likely to occur as a result of sports and occupational strains and on the other that it is particularly vulnerable to injuries. Diagnostic radiology from two different perspectives is the basic diagnostic procedure for unexplained shoulder pain and for shoulder injuries. Dislocating osseous injuries or luxations can be detected most precisely or assessed most reliably during follow-up by this means. Intra-articular findings and alterations to the soft tissues (degenerative, traumatic) can be delineated by sonography, computed tomography and magnetic resonance imaging, albeit with differing degrees of reliability and specificity. Sonography is generally available, but not reliably standardized. Computed tomography is the method of choice for diagnosis of osseous and joint injuries. Over the last 10 years magnetic resonance imaging (MRI) has improved in sensitivity and specificity with technical progress (coils, sequences, reconstruction modalities) and has therefore moved into the focus of clinical interest.
    Notes: Das Schultergelenk ist infolge seiner anatomischen Ausbildung als Kugelgelenk das beweglichste Gelenk des menschlichen Körpers. Die sich hieraus ergebenden Bewegungsmöglichkeiten bedingen einerseits bereits frühzeitig degenerative Schädigungen infolge beruflicher oder sportlicher Belastungen und andererseits eine besondere ¶Angriffsfläche für Verletzungen. Die Basisdiagnostik sowohl des unklaren Schulterschmerzes als auch verletzungsbedingter Schädigungen am Schultergelenk ist die Röntgendiagnostik in 2 Ebenen. Dislozierende ossäre Verletzungen bzw. Luxationen sind hiermit treffsicher nachzuweisen bzw. in der Verlaufskontrolle zu beurteilen. Intraartikuläre Befunde und Weichteilveränderungen (degenerativ, traumatisch) sind hingegen mit den Schnittbildverfahren der Sonographie, Computertomographie und Kernspintomographie mit unterschiedlicher Treffsicherheit und Spezifität nachzuweisen. Die klassische Gelenkarthrographie hingegen tritt gegenüber diesen Verfahren deutlich in ihrer Bedeutung zurück. Die Sonographie ist ein ubiquitär verfügbares, jedoch wenig standardisiertes Verfahren. Die Reproduzierbarkeit der Befunde ist fraglich. Die Computertomographie stellt die Methode der Wahl bei der Diagnostik von okkulten ossären bzw. Gelenkverletzungen dar. Die Methode ist breit verfügbar und mit vertretbarem Aufwand durchzuführen. In den letzten 10 Jahren hat die Kernspintomographie infolge der technischen Weiterentwicklung (Spulen, Sequenzen, Rekonstruktionsmöglichkeiten usw.) an Sensitivität und Spezifität gewonnen. In der Summe aller klinischen Fragestellungen stellt sie neben der Basisdiagnostik derzeit die effektivste Untersuchungsmethode des Schultergelenks dar.
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  • 61
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    Rechtsmedizin 10 (2000), S. 90-95 
    ISSN: 1434-5196
    Keywords: Schlüsselwörter Geschosse ; Verletzungen ; MRT ; Beurteilung ; Dokumentation ; Keywords Projectiles ; Injuries ; MRI ; Assessment ; Documentation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Law
    Description / Table of Contents: For the assessment of gunshot injuries, conventional X-ray examination, ultrasound and CT examinations are commonly used imaging techniques. With the exception of some authors, there is agreement that projectiles indicate a contraindication for MRI because of artificial imaging side-effects and the potential of secondary dislocation due to ferromagnetism. MRI testing was carried out on 56 projectiles for ferromagnetism and imaging quality in vitro and in pig carcasses with a 0.2 T and a 1.5T-MRI scanner. The image quality was compared to that of a CT scan. Projectiles with ferromagnetic properties can easily be distinguished from non-ferromagnetic ones by pretesting the motion of an projectile of the same type within the magnetic field of the MR scanner. When ferromagnetic projectiles were excluded, MRI yielded the more precise images compared to other imaging techniques. Projectile localization and associated soft tissue injuries were visualized without artifacts in all cases. When ferromagnetism is excluded MRI gives an excellent imaging procedure for the assessment and documentation of gunshot injuries. Therefore this imaging procedure may be also useful for medico-legal investigations.
    Notes: Zur Beurteilung des Ausmaßes von Schußverletzungen und zur Lokalisationsdiagnostik werden allgemein konventionelle Röntgenübersichtsaufnahmen sowie die Sonographie und die Computertomographie angewendet. Mit Ausnahme weniger Autoren wird generell davon ausgegangen, daß Projektile aufgrund der Generierung von Artefakten in der Bildgebung und der Gefahr einer sekundären Fremdkörperdislokation, bedingt durch den Ferromagnetismus, nicht mit der MRT beurteilt werden dürfen. 56 verschiedene Projektile wurden nach entsprechender Vortestung bezüglich ihrer Ferromagnetizität mit je einem 0,2-T- und 1,5-T-MRT-Gerät in vitro und anschließend in Schweinekadavern untersucht. Die Bildqualität wurde mit denen von CT-Bildern verglichen. Die ferromagnetischen Eigenschaften der Projektile können leicht beurteilt werden, indem man Vergleichsgeschosse desselben Typs in das Magnetfeld des MRT-Gerätes legt. Nach Ausschluß der Ferromagnetizität übertrifft die MRT alle anderen bildgebenden Verfahren. In allen Fällen gelang eine exakte Projektillokalisation sowie eine überlegene Darstellung der Weichteilverletzungen. Aufgrund der Ergebnisse ist die MRT, nach Ausschluß von ferromagnetischen Fremdkörpern, ein exzellentes Verfahren zur Beurteilung und Dokumentation von Schußverletzungen. Abhängig von den Fragestellungen kann dieses bildgebende Verfahren auch in der Rechtsmedizin eingesetzt werden.
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  • 62
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    Mund-, Kiefer- und Gesichtschirurgie 4 (2000), S. 111-117 
    ISSN: 1434-3940
    Keywords: Schlüsselwörter Kiefergelenkfrakturen ; Kernspintomographie ; Achsiographie ; Diskusmobilität ; Diskusposition ; Key words TMJ fractures ; MRI ; Axiography ; Disc mobility ; Disc position
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Magnetic resonance imaging (MRI) assessment of traumatized temporomandibular joints (TMJ) usually focuses on disc position, defining regular joint function by normal, excentric or displaced disc position. So far, there are only few reports regarding disc position after open reduction of diacapitular or high condylar fractures of the TMJ with dislocation. The aim of the present study was to evaluate the role of the disc as regards postoperative functional outcome by electronic axiographic recordings of condylar movements and MRI, displacement of the disc and lesions of TMJ soft tissues being frequent in this type of mandibular fractures. A total of 30 subjects with 37 condylar fractures in whom osteosynthesis was performed using a preauricular approach were imaged postoperatively (mean 24 months) with a 1.5-Tesla MRI system to determine, (a) the position of the disc, (b) the range of mobility of the disc and (c) condylar mobility in closed and open mouth position, comparing fractured sides (FS) vs nonfractured sides (NFS). Linear movements between the two jaw positions in the sagittal plane were measured by superimposing transparencies. The results indicate: (1) more than 70% of the discs (FS) were found to be in normal position; there was no disc displacement without reduction. However, these data stood in contrast to severe limitations of the axiographic tracings as presented by almost 30% of the subjects. (2) Significant correlations were found between fixed (α = 0.05) or highly immobilized (α = 0.01) discs and axiographic limitations, suggesting disc mobility to be a valuable parameter for assessment of the postoperative functional outcome.
    Notes: Zusammenfassung Bei diakapitulären Frakturen bzw. hohen Kollumluxationsfrakturen mit Beziehung zum Lig. laterale sind Verlagerungen des Diskus häufig und werden nach konservativer Therapie mit einer Häufigkeit zwischen 50 und 100% angegeben. Informationen über die Diskusposition nach operativer Versorgung dieser Frakturgruppen liegen bisher nicht vor. Ziel der vorliegenden Studie war es, die Bedeutung von Position und Mobilität des Diskus für das postoperative funktionelle Ergebnis dieser Frakturgruppen zu klären. Die Objektivierung der operativen Ergebnisse bei 30 Patienten mit 37 über einen präaurikulären Zugang versorgten Gelenkfrakturen erfolgte mittels elektronischer Achsiographie und Kernspintomographie (1,5-T-System), im Mittel 24 Monate postoperativ. Erhoben wurden die Position und der Bewegungsumfang des Diskus bzw. des Kondylus im Seitenvergleich. Die linearen Bewegungen zwischen mundoffener und -geschlossener Position wurden durch Folienüberlagerung korrespondierender sagittaler MRT-Schichten ermittelt. Die Ergebnisse zeigten zum einen, dass 〉 70% der Disci auf der Frakturseite orthotop (Position A) lagen und keine fixierten anterioren Dislokationen (C) auftraten. Die achsiographischen Befunde zeigten in Diskrepanz dazu bei immerhin 30% der versorgten Gelenke höhergradige Limitationen der Exkursionsbahnen. Zum anderen bestehen signifikante Zusammenhänge zwischen fixierten (α = 0,05) bzw. hochgradig immobilisierten (α = 0,01) Disken und achsiographisch erfassten Limitationen der Translationsbewegung. Im Gegensatz zu bisherigen Studien sollten nach der operativen Versorgung von Gelenkfrakturen nicht nur die (statische) Diskusposition, sondern in erster Linie die Diskusmobilität als Parameter für das funktionelle Ergebnis berücksichtigt werden.
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  • 63
    ISSN: 1434-3940
    Keywords: Schlüsselwörter Kiefergelenk-MRT ; Diskusdislokation ; Kiefergelenkhistologie ; Keywords Temporomandibular joint (TMJ) ; MRI ; Anterior disk dislocation ; TMJ histology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Abstract Problem. Anterior dislocation of the articular disk of the temporomandibular joint (TMJ) found by MRI tomography often presents a problem. It may persist in MRI despite improvement of articular symptoms and even be found in healthy persons free of any symptoms. Can this be explained by the similarity in structure of the anterior connective tissue of the disk and capsule and their pathological changes? Is a second coronal plane required for MRI investigation? Material and methods. The preauricular regions of 72 patients of the TMJ clinic were examined by oblique-sagittal and oblique-coronal MRI. A Siemens-Vision MRI was used. It was also possible to prepare 10 articular disks of the TMJ with anterior capsular tissue as well as 20 complete TMJs of adults from autopsy material. Sagittal, transversal, and horizontal serial sections were examined histologically. Results. In 49 of the 72 cases examined, an anterior dislocation without reduction found in the sagittal MRI was not confirmed in the oblique-coronal MRI. In the sagittal MRI it was possible to differentiate three, in the coronal MRI six typical forms of magnetic resonance signals, which are represented in figures. They are compared with anatomical and histological connective tissue findings adjacent to the TMJ. The structural similarity of the disk and anterior capsular tissue of the TMJ is demonstrated. The close connection of the disk and connective tissue surrounding the TMJ makes differentiation of MRI findings difficult especially following regressive and adaptive reactions. Conclusions. In MRI, anterior capsular tissue is able to simulate dislocation of the disk. Pathological tissue reactions may alter the MRI signal and lead to the wrong diagnosis of dislocation of the disk. Diagnosis of an anterior disk dislocation cannot be established solely on the basis of oblique-sagittal MRI findings.
    Notes: Zusammenfassung Fragestellung. Der Befund anteriore Diskusdislokation im sagittalen MRT beinhaltet 2 ungeklärte Probleme. Trotz Rückbildung einer Gelenksymptomatik können anteriore Diskusdislokationen im MRT unverändert bestehen, sie wurden sogar bei gesunden Probanden beschrieben. Ist die Ursache in der feingeweblichen Ähnlichkeit der anterioren Diskus- und Kapselbindegewebe und in deren pathologischen Strukturänderungen zu suchen? Kann auf die Befundung in der 2. koronalen Ebene verzichtet werden? Material und Methode. Die präartikulären Regionen im schräg-sagittalen und im schräg-koronalen MRT von 72 Patienten aus der Kiefergelenkspezialsprechstunde wurden befundet. Die Untersuchungen erfolgten mit dem Siemens-Vision-MRT. Bei unselektierten Sektionen konnten 10 Disci articulares mit dem anterioren Kapselgewebe sowie 20 Kiefergelenkpräparate Erwachsener präpariert werden. Sagittale, transversale und horizontale Serienschnitte wurden histologisch untersucht. Ergebnisse. Bei 49 von 72 ausgewählten Fällen gab es für eine anteriore Diskusdislokation ohne Reduktion im sagittalen MRT keine Bestätigung im schräg-koronalen MRT. Es konnten in den sagittalen MRT 3, in den koronalen MRT 6 sich wiederholende Signalformen differenziert werden. Sie sind skizziert. Ihre Zuordnung zu gelenkumgebenden Bindegeweben erfolgte mittels Vergleich dieser Signalformen mit den anatomischen und histologischen Kiefergelenkpräparaten. Die feingewebliche Ähnlichkeit des Discus articularis mit dem anterioren Kapselbindegewebe wird aufgezeigt. Seine enge Verbindung mit den gelenkumgebenden Bindegeweben erschwert die Differenzierung im MRT insbesondere beim Vorliegen regressiver und adaptiver Reaktionen. Schlussfolgerung. Das anteriore Kapselgewebe kann eine Diskusdislokation im MRT vortäuschen. Pathologische Gewebereaktionen ändern das MRT-Signal und tragen dazu bei, falsch-positive Befunde zur Diskusdislokation entstehen zu lassen. Schräg-sagittale MRT sind für die Diagnosefindung „anteriore Diskusdislokation mit und ohne Reposition“ nicht ausreichend.
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  • 64
    ISSN: 1433-0407
    Keywords: Schlüsselwörter Gliomatosis cerebri ; MRT-Diagnose ; Enzephalitis ; Key words Gliomatosis cerebri ; MRI ; Diagnosis ; Encephalitis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary The diagnosis of the rare disease Gliomatosis cerebri requires the correlation of clinical, radiological, and pathological findings. We report on two patients with intravitally diagnosed gliomatosis cerebri. Due to the unusually high malignancy of the tumor cells, diagnosis was complicated by atypical findings such as gadolinium enhancement in MRI and raised intracranial pressure. The clinical course, differential diagnosis, and literature are summarized briefly.
    Notes: Zusammenfassung Die Diagnose der seltenen Gliomatosis cerebri kann nur in Zusammenschau von klinischen, radiologischen und histopathologischen Befunden gestellt werden. Im vorliegenden Artikel berichten wir über 2 Patienten, bei denen intra vitam nach stereotaktischer Hirnbiopsie die Diagnose Gliomatosis cerebri gesichert wurde. Da in beiden Fällen für Gliomatosis cerebri ungewöhnlich hochgradig entdifferenzierte Tumorzellen vorlagen, wurde die Diagnosefindung durch atypische Befunde wie Kontrastmittelaufnahme im MRT und klinische Zeichen der intrakraniellen Drucksteigerung erschwert. Klinischer Verlauf, Differentialdiagnosen und Literatur werden kurz dargestellt.
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  • 65
    ISSN: 1433-0407
    Keywords: Schlüsselwörter Hallervorden-Spatz-Krankheit ; Parkinsonsyndrom ; MRT ; 123J-β-CIT ; 123J-IBZM ; Keywords Hallervorden-Spatz Disease ; Parkinson's syndrome ; MRI ; 123I-β-CIT ; 123I-IBZM
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Abstract Hallervorden-Spatz disease (HSD), a rare extrapyramidal motor illness, is usually only confirmed after death. In vivo diagnosis has relied hitherto on the combination of typical magnetic resonance imaging (MRI) findings (the “eye of the tiger” sign) and heterogeneous clinical symptoms of movement disorder which have been regarded as almost pathognomonic. We report on the diagnostic contribution of 123J-β-CIT single photon emission computed tomography (SPECT) and 123J-IBZM SPECT in akinetic-rigid Parkinson's syndrome occurring in a case of HSD. In contrast to Parkinson's disease and multisystem atrophies, the results of both tests were normal. This constellation of findings shows that the degeneration lies primarily outside the nigrostriatal system, supporting arguments for the nosologic distinction of HSD from other extrapyramidal illnesses.
    Notes: Zusammenfassung Die Diagnose der Hallervorden-Spatz-Krankheit (HSD), einer seltenen extrapyramidal-motorischen Erkrankung, konnte gewöhnlich erst postmortal gesichert werden. Bislang galt der typische MRT-Befund mit dem “Tigerauge-Zeichen” in Kombination mit der heterogen klinischen Symptomatik von Bewegungsstörungen als nahezu pathognomonisch und diente zur Diagnosestellung zu Lebzeiten. In der vorliegenden Kasuistik soll der diagnostische Beitrag von 123J-β-CIT und 123J-IBZM-SPECT bei einem akinetisch-rigiden Parkinsonsyndrom im Rahmen einer HSD dargestellt werden. Für beide Untersuchungen wurden im Gegensatz zum M. Parkinson und Multisystematrophien Normalbefunde gefunden. Diese Befundkonstellation zeigt einerseits, dass die Degeneration primär außerhalb des nigrostriatalen Systems liegt, und andererseits unterstützt sie die Diskussion der nosologischen Abgrenzung der HSD von anderen extrapyramidalen Erkrankungen.
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  • 66
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    Der Nervenarzt 71 (2000), S. 91-95 
    ISSN: 1433-0407
    Keywords: Schlüsselwörter Creutzfeldt-Jakob-Krankheit ; Diagnostik ; Diffussionswichtung ; MRT ; Bildgebung ; Übertragbare spongiforme Enzephalopathien ; Key words Creutzfeldt-Jakob disease ; Diagnosis ; Diffusion-weighted image ; MRI ; Brain images ; Transmissible spongiform encephalopathies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Today the diagnosis of Creutzfeldt-Jakob disease (CJD) is proven only postmortem or by evidence of neuropathology. During the patient's lifetime EEG recordings or cerebrospinal fluid analysis may support the diagnosis. In most cases, T2-MRI scans show hyperintensities of the basal ganglia. A new imaging technique called diffusion-weighted MRI (DWI) has recently been established. The sensitivity of DWI was evaluated in five patients suspected of CJD. All five cases showed hyperintense signal changes in the basal ganglia on DWI sequences. These findings were more pronounced in DWI than in T2, FLAIR, or PD-weighted images. Thus, DWI seems to be the most sensitive sequence for detecting changes in patients with suspected CJD. Moreover, its short scanning time ensures that fewer artifacts occur, especially in the case of myoclonus.
    Notes: Zusammenfassung Die sichere Diagnose der Creutzfeldt-Jakob-Krankheit kann nur bioptisch oder autoptisch durch Untersuchung von Hirngewebe gestellt werden. Die klinische Verdachtsdiagnose erhärten können technische und laborchemische Untersuchungen; hierzu gehört neben dem EEG die Surrogatmarkerbestimmung im Liquor. Nachdem sich bei der Mehrzahl der Patienten Veränderungen der Basalganglien gezeigt haben, gehört das MRT zu den bildgebenden Verfahren, die bei Verdacht auf CJD eingesetzt werden können. Inzwischen ist die Diffusionswichtung (DWI) in die neuroradiologische Diagnostik eingeführt worden. DWI-gewichtete MRTs bei 5 CJD-Patienten wurden von uns untersucht. Alle 5 Fälle zeigten im DWI-MRT signalintense Veränderungen der Stammganglien. Diese Veränderungen waren jeweils deutlicher als in der T2, Flair- oder Protonenwichtung. Das DWI-MRT halten wir für sensitiver zum Nachweis kortikaler und basaler Veränderungen bei CJD-Patienten im Vergleich zu Standardsequenzen. Durch die kurze Untersuchungszeit können besonders bei den häufig vorhandenen Myoklonien andere Wichtungen aufgrund von Bewegungsartefakten oftmals nicht in der gewünschten Qualität durchgeführt werden.
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  • 67
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    Der Unfallchirurg 103 (2000), S. 1079-1085 
    ISSN: 1433-044X
    Keywords: Schlüsselwörter Knie ; MRT ; Arthroskopie ; Meniskus ; Key words Knee ; MRI ; Arthroscopy ; Meniscus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary In order to assure diagnostic accuracy, 172 knee joints were examined prospectively by MRI. After MRI, all knee joints were examined by arthroscopy. Tears of the medial meniscus were found in 102 patients, the lateral meniscus showed a tear in 29 cases. Assuming that arthroscopy represents the golden standard of diagnostic measure concerning the knee joint, it can be stated that false-positive MRI findings on the medial and lateral meniscus were diagnosed in three cases and false-negative MRI findings were diagnosed for two knee joints regarding the medial meniscus and four times regarding the lateral meniscus. For the medial meniscus a sensitivity of 98%, a specificity of 96%, an accuracy of 94%, and the positive and negative value of prediction were calculated at 97% each. Regarding the lateral meniscus, a sensitivity of 85%, a specificity of 98%, an accuracy of 92%, a positive predictive value of 88%, and a negative predictive value of 85% were found. Under the prerequisite that the MRI is carried out correctly and assessed by an experienced radiologist, the accuracy of the MRI for meniscus diagnosis is almost equivalent to the one by arthroscopy. Under these conditions, MRI can be recommended when no safe and sufficient clinical diagnosis can be made. The rate of unnecessary arthroscopies with a pure diagnostic purpose can be lowered significantly by means of MRI.
    Notes: Zusammenfassung Zur Überprüfung der diagnostischen Treffsicherheit wurden prospektiv 172 Kniegelenke mittels Magnetresonanztomographie (MRT) untersucht. Nach der MRT erfolgte bei allen Kniegelenken die arthroskopische Überprüfung der bildgebenden Diagnose. Rissbildungen des Innenmeniskus fanden sich bei 102 Patienten, am Außenmeniskus wurde 29-mal ein Riss befundet. Unter der Annahme, dass die Arthroskopie der “golden standard” diagnostischer Maßnahmen am Kniegelenk darstellt, ergab sich, dass falsch-positive MRT-Befunde am Innen- und Außenmeniskus in jeweils 3 Fällen und falsch-negative MRT-Befunde am Innenmenikus bei 2 Kniegelenken und am Außenmeniskus 4-mal erhoben wurden. Für den Innenmeniskus wurde eine Sensitivität von 98%, eine Spezifität von 96%, eine Genauigkeit von 94% und der positive bzw. negative Vorhersagewert mit jeweils 97% errechnet. Bezüglich des Außenmeniskus ließ sich eine Sensitivität von 85%, eine Spezifität von 98%, eine Genauigkeit von 92%, ein positiver Vorhersagewert von 88% und ein negativer Vorhersagewert von 85% ermitteln. Unter der Voraussetzung, dass die MRT korrekt durchgeführt und von einem erfahrenen Radiologen befundet wird, ergibt sich eine annähernd gleichwertige Treffsicherheit der MRT für die Meniskusdiagnostik wie mit der Arthroskopie. Die MRT kann daher unter diesen Voraussetzungen zur Anwendung empfohlen werden, wenn klinisch keine ausreichend sichere Diagnose zu stellen ist. Die Rate unnötiger rein diagnostischer Arthroskopien kann durch die MRT entscheidend gesenkt werden.
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  • 68
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    Der Nervenarzt 71 (2000), S. 411-415 
    ISSN: 1433-0407
    Keywords: Schlüsselwörter Kufs ; Neuronale Zeroidlipofuszinose ; Demenz ; PET ; MRT ; Key words Kufs disease ; Neuronal ceroid lipofuscinosis ; Dementia ; PET ; MRI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary The case of a 35-year-old man with progressive dementia from the age of 17 is presented. Clinical examination showed mild extrapyramidal and cerebellar signs and rare myoclonus. Neuropsychological evaluation disclosed severe cognitive deficits. Magnetic resonance imaging (MRI) revealed moderate generalized atrophy with abnormal iron deposition in the basal ganglia. Positron emission tomography (PET) with 18-fluorodeoxyglucose (18-FDG) demonstrated clear temporoparietal hypermetabolism. The clinical symptoms and course are typical for the rare adult type of neuronal ceroid lipofusconoses (Kufs' disease). The diagnosis is supported by the electron microscope detection of an abnormal accumulation of lipid vacuoles and lipofuscin in the eccrine sweat glands and the rectal ganglia cells.
    Notes: Zusammenfassung Berichtet wird der Fall eines 35-jährigen Patienten mit langsam progredienter Demenz seit dem 18. Lebensjahr. Zum Zeitpunkt der Untersuchung fielen klinisch eine leichtgradige extrapyramidale und zerebelläre Symptomatik sowie seltene Myoklonien auf, während die neuropsychologische Testung ausgeprägte kognitive Defizite ergab. Die kraniale Magnetresonanztomographie zeigte eine mäßige globale Atrophie und eine abnorme Eisenablagerung in den Basalganglien. In der Positronenemissionstomographie mit 18-FDG war ein deutlicher temporoparietaler Hypometabolismus erkennbar. Klinik und Verlauf sind typisch für die seltene adulte Variante der neuronalen Zeroidlipofuszinosen (Kufs-Typ). Diese Diagnose wird gestützt durch den elektronenmiroskopischen Nachweis abnormer Akkumulationen von Fettvakuolen und Lipofuszinablagerungen in den ekkrinen Schweißdrüsen der Haut und in den rektalen Ganglienzellen.
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  • 69
    ISSN: 1433-0407
    Keywords: Schlüsselwörter Manganintoxikation ; Parkinsonismus ; MRT ; Verlaufskontrolle ; L-Dopa-Therapie ; Key words Manganese intoxication ; Parkinsonism ; MRI ; Follow-up study ; L-dopa treatment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Manganese intoxication is an unusual, severe form of intoxication. This report deals with a patient now 80 years old who accidentally ingested a solution of potassium permanganate for a period of at least 4 weeks 14 years ago. Since then, the patient suffers from a mild parkinsonian syndrome and distally accentuated polyneuropathies. Psychiatric disorders, especially demential or depressive symptoms, were not observed. Manganese analysis of his hair still shows a clear increase in manganese concentration. The MRI of his brain showed no pathological changes, in particular none of those often described with symmetric signal elevation in T1 in the area of the basal ganglia. In this study, we present clinical, laboratory, and neuroradiological findings. Unusual in this case with a short exposition is the long duration and clinical improvement without L-dopa treatment.
    Notes: Zusammenfassung Eine Manganintoxikation ist eine ungewöhnliche, schwere Intoxikationsform. Wir berichten über einen jetzt 80-jährigen Patienten, der vor 14 Jahren über die Dauer von mindestens 4 Wochen versehentlich Kaliumpermanganat eingenommen hatte. Der Patient leidet weiterhin unter einem leichten Parkinsonsyndrom und einer distal betonten Polyneuropathie. Psychiatrische St¨rungen, insbesondere ein dementielles oder depressives Symptom, fanden sich nicht mehr. Die Mangananalysen der Haare zeigen auch jetzt noch deutlich erhöhte Konzentrationen. Das MRT des Gehirns erbrachte keinen pathologischen Befund, insbesondere keine häufig bei Manganintoxikationen beschriebenen Veränderungen mit symmetrischen Signalanhebungen in T1-Wichtung im Bereich der Basalganglien (Globus pallidus). In einer aktuellen Untersuchung werden klinische, laborchemische sowie neuroradiologische Ergebnisse vorgestellt. Die Besonderheit des Falles erklärt sich aus einer kurzen Expositionsdauer mit einer langen Verlaufszeit und klinischer Befundbesserung ohne L-Dopa-Behandlung.
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  • 70
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    International journal of clinical oncology 5 (2000), S. 200-203 
    ISSN: 1437-7772
    Keywords: Key words Small cell carcinoma of the ovary ; Pregnancy Paclitaxel ; MRI ; Facial palsy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Small cell carcinoma of the ovary (SCCO) is a highly aggressive malignancy that affects young females. The disease is fatal in nearly all patients with disease categorized as higher than stage IA. A 30-year-old Japanese woman was diagnosed, while pregnant, as having bilateral small cell carcinoma, pulmonary type, a rare finding. She received three courses of JP chemotherapy (carboplatin, 525 mg; cisplatin, 120 mg) and three courses of PVP chemotherapy (peplomycin, 30 mg; vinblastin, 12 mg; cisplatin, 120 mg). Computed tomography scans were taken during and after the period in which she received chemotherapy showed growing multiple metastatic tumors and massive ascites. Third-line chemotherapy with paclitaxel (225 mg) was then initiated. Although the lymphadenopathy and massive ascites were alleviated, bone marrow suppression intervened. The patient died 18 months after being diagnosed. To our knowledge, this is third reported case of SCCO to be diagnosed during pregnancy, and the first reported case of bilateral disease diagnosed during pregnancy.
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  • 71
    ISSN: 1437-7772
    Keywords: Key words Endometrial carcinoma ; MRI ; Diagnosis ; Minimally invasive therapy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Background. Magnetic resonance imaging (MRI) provides precise staging of endometrial carcinoma. However, we have sometimes experienced patients with microscopic extrauterine extension in whom MRI showed the disease as being limited to the uterus. We studied indirect MRI signs for microscopic extrauterine spread of endometrial carcinoma which outwardly seemed to be limited to within the uterus. Methods. MRI studies and the clinical records of 100 patients with surgically proven endometrial carcinoma were retrospectively reviewed. We evaluated: (1) MRI staging, (2) tumor growing at the orifices of the fallopian tube in the uterine fundus, (3) hydrosalpinx, and (4) ascites, in each MRI study. Results. Surgical specimens showed that 12 of the 100 patients had extrauterine spread, with 1 patient showing both ovarian extension and omental metastasis; there ovarian extension in 3, extension to the fallopian tubes in 3, omental metastasis in 1, and positive peritoneal cytology in 4. Tumor growing at the orifices of the fallopian tubes with deep myometrial invasion showed higher accuracy for predicting microscopic intrauterine spread (82.0%) although it was not significantly different from the accuracy of deep myometrial invasion anywhere within the uterus (75.0%). However, tumor growing at the orifices of the fallopian tubes in a patients with stage Ia disease showed a high negative predictive value (89.7%). Hydrosalpinx had the highest specificity (98.9%) and accuracy (88.0%); however, it did not seem to be practical because it was observed in only 2 patients. Ascites in postmenopausal patients showed higher specificity (93.5%), although it was not considered to be useful in the premenopausal patients. Conclusion. Tumor extension at the orifices of the fallopian tubes in patients with stage Ia disease, and ascites in postmenopausal patients on MRI seemed to be predictive factors for microscopic extrauterine spread.
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  • 72
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    Skeletal radiology 29 (2000), S. 40-44 
    ISSN: 1432-2161
    Keywords: Key words Subchondral insufficiency fracture ; Femoral head ; Medial femoral condyle ; Osteonecrosis ; MRI ; X-ray
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  This case report documents the clinical, radiographic, and histologic findings in a 69-year-old obese man, who had subchondral insufficiency fracture both in the femoral head and medial femoral condyle. On plain radiographs, both lesions underwent subchondral collapse. Magnetic resonance images of the left hip showed a bone marrow edema pattern with associated low-intensity band on T1-weighted images, which was convex to the articular surface. The histopathologic findings in the hip and knee were characterized by the presence of a subchondral fracture with associated callus and granulation tissue along both sides of a fracture line. There was no evidence of antecedent osteonecrosis. To our knowledge, this is the first case report to describe the multiple occurrence of collapsed subchondral insufficiency fracture.
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  • 73
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    Skeletal radiology 29 (2000), S. 45-48 
    ISSN: 1432-2161
    Keywords: Key words Cystic fibrous dysplasia ; Giant cell tumor ; Femur ; X-ray ; MRI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  We report the case of a 43-year-old man who presented with an osteolytic and expansive lesion in the left distal femur mimicking a giant cell tumor. Magnetic resonance imaging (MRI) showed that most of the lesion was cystic, and histological examination revealed fibrous dysplasia with marked cystic degeneration. Radiographic findings of cystic fibrous dysplasia in the end of a long bone may be similar to those of a giant cell tumor, and a biopsy is essential for the final diagnosis.
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  • 74
    ISSN: 1432-2161
    Keywords: Key words Hemangiopericytoma ; Tibia ; MRI ; Angiography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The Magnetic Resonance Imaging (MRI) appearances of primary osseous hemangiopericytoma (HPC) have been rarely described. We report on a 46-year-old Chinese man with primary osseous HPC of the right tibia. The characteristic vascular distribution of this tumor, presenting with a ”spoke-wheel” appearance on MR images and with angiographic correlation, is described. Although not pathognomonic, this MR appearance may be an important finding in suggesting the diagnosis of osseous HPC.
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  • 75
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    Skeletal radiology 29 (2000), S. 555-562 
    ISSN: 1432-2161
    Keywords: Keywords Diffusion ; MRI ; Skeletal system ; Spine ; neoplasms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  This article reviews the principles of diffusion-weighted imaging (DWI) and recent results in DWI of the musculoskeletal system. The potential of DWI in the diagnosis of pathology of the musculoskeletal system is discussed. DWI is a relatively new MR imaging technique that has already been established in neuroradiology, especially in the early detection of brain ischemia. The random motion of water protons on a molecular basis can be measured with DWI. To date DWI of the abdomen and of the musculoskeletal system has only been employed in scientific studies, but first results indicate that it may also be beneficial in these fields. Different diffusion characteristics have been found in normal tissues such as muscle, fat and bone marrow. Also, pathologic entities such as neoplasms, post-therapeutic soft tissue changes and inflammatory processes can be differentiated. Normal muscle shows significantly higher diffusion values than subcutaneous fat and bone marrow, due to a higher mobility of water protons within muscle. Soft tissue tumors exhibit a significantly lower diffusion value compared with post-therapeutic soft tissue changes and inflammatory processes. Necrotic tumor tissue can be distinguished from viable tumor due to significantly higher diffusion of water protons within necrotic tissue.
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  • 76
    ISSN: 1432-2161
    Keywords: Keywords Gaucher disease ; MRI ; Enzyme replacement therapy ; Liver ; Spleen ; Bone marrow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Purpose. To determine whether T1-weighted magnetic resonance (MR) images can demonstrate response in the marrow of patients with type 1 Gaucher disease treated with enzyme replacement therapy (ERT) and to determine whether a relationship exists between liver and spleen volume reductions and visible marrow changes. Patients. Forty-two patients with type 1 Gaucher disease were evaluated on at least two occasions. Thirty-two patients received ERT. Of these patients, 15 had a baseline examination prior to the initiation of ERT. The remaining 10 patients did not receive ERT. Design. T1-weighted and gradient recalled echo (GRE) coronal images of the femurs and hips were obtained. Concurrently, liver and spleen volumes were determined using contiguous breath-hold axial gradient-echo images. T1-weighted images of the hips and femurs were evaluated to determine change or lack of change in the yellow marrow. Results. Of the 32 patients receiving ERT, 14 (44%) demonstrated increased signal on T1-weighted images suggesting an increase in the amount of yellow marrow. If only the 15 patients with a baseline examination were considered, the response rate to ERT was 67%. Using Student’s t-test a highly significant correlation (P〈0.005) was found between marrow response and reduction in liver and spleen volume. Conclusions. Marrow changes in patients receiving ERT can be detected by T1-weighted images. This response correlated with reductions in visceral volumes (P〈0.0005).
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  • 77
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    Skeletal radiology 29 (2000), S. 597-600 
    ISSN: 1432-2161
    Keywords: Keywords Parosteal osteosarcoma ; Telangiectatic osteosarcoma ; Dedifferentiation ; Femur ; Radiography ; MRI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  A unique case of parosteal osteosarcoma (POS) of the proximal femur, with areas of telangiectatic dedifferentiation, in a 28-year-old woman is reported. The patient had a 7-week history of pain and swelling in her right thigh. A biopsy diagnosis of POS was established. The patient was treated with two cycles of intra-arterial chemotherapy, followed by limb salvage surgery. Histological examination of the resected specimen showed POS with areas of dedifferentiation composed of high-grade telangiectatic osteosarcoma with associated secondary aneurysmal bone cyst change.
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  • 78
    ISSN: 1432-2161
    Keywords: Keywords Ewing sarcoma ; Primitive neuroectodermal tumour ; Radiography ; MRI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Objective.To describe the clinical, radiological and MRI features of six atypical cases of histologically proven appendicular Ewing sarcoma/ primitive neuroectodermal tumour (PNET). Design. Retrospective review of case notes and available imaging was carried out. Patients. Six patients (4 male, 2 female; mean age 27years, range 19–44 years), presenting over a 77-month period, were identified from the Bone Tumour Register. All had unusual clinical and imaging features for Ewing sarcoma/PNET. Results and conclusions. Four tumours were centred on the distal femoral metaphysis, one in the proximal tibial metaphysis and one in the distal tibial metaphysis. Plain radiographs were available in four cases and showed minor cortical changes. MRI demonstrated a relatively small, eccentrically located intraosseous component with a large, eccentric extraosseous component. Extension into the epiphysis was seen in three cases and into the adjacent joint in two cases. Intraosseous ”skip” metastases were present in three cases. The clinical and imaging features were atypical for conventional intraosseous Ewing sarcoma/PNET and the exact site of origin (intraosseous, periosteal or soft-tissue) was unclear.
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  • 79
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    Skeletal radiology 29 (2000), S. 656-659 
    ISSN: 1432-2161
    Keywords: Keywords Osteoblastoma-like osteosarcoma ; Osteosarcoma ; Aggressive osteoblastoma ; Fibula ; Radiography ; MRI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  We report an osteoblastoma-like osteosarcoma in the right proximal fibula in a 22-year-old woman. Radiographs showed an irregular osteolytic lesion from the metaphysis to the epiphysis in the proximal fibula with partial destruction of cortical bone. Tissue from a biopsy indicated a typical osteoblastoma. Curettage and bone graft was performed. One year after the surgery, local recurrence occurred, and a wide excision was performed. Histological examination of the en-bloc surgical specimen revealed the tumor had permeated through the host bony trabeculae, although the nuclear atypia was not marked. Immunohistochemical expression of MIB-1 was detected in 9.0% of cells.
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  • 80
    ISSN: 1432-2161
    Keywords: Keywords Acute lymphoblastic leukemia ; Chemotherapy ; Spine ; Tunneling Schmorl’s nodes ; CT ; MRI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  We present a 70-year-old woman with pre-B acute lymphoblastic leukemia in whom serial imaging studies showed the development of multiple vertebral collapse, and communicating superior and inferior Schmorl’s nodes creating a longitudinal channel (”tunneling” Schmorl’s nodes) through the anterior aspect of T12 to L3 vertebral bodies of her osteoporotic thoracolumbar spine. This was observed after achieving complete remission of the disease and during maintenance therapy. The finding is felt to be secondary to iatrogenic exacerbation of osteoporosis.
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  • 81
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    Skeletal radiology 29 (2000), S. 664-667 
    ISSN: 1432-2161
    Keywords: Keywords Giant cell tumor ; Multiple mid-foot bones ; Reconstructive surgery ; Radiography ; MRI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  We report on a patient who had giant cell tumor involving multiple bones of the mid-foot. The tumor originated from the navicular bone, but also destroyed the cuboid, and all cuneiform bones. This unusual presentation of giant cell tumor presented a therapeutic challenge for the surgeons. The patient was treated with en bloc resection and the bony defect replaced with a massive iliac crest graft which united within 9 months and has remained stable for 7 years without local recurrence, and with excellent function of the foot.
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  • 82
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    Skeletal radiology 29 (2000), S. 224-226 
    ISSN: 1432-2161
    Keywords: Key words Intraosseous neurilemmoma (schwannoma) ; Primary bone neoplasm ; Metacarpal ; X-ray ; MRI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Intraosseous schwannoma (neurilemmoma) is an extremely rare, benign neoplasm, constituting less than 0.2% of primary bone tumors. It infrequently involves the bones of the hand. We present a case of intraosseous neurilemmoma of the metacarpal.
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  • 83
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    Skeletal radiology 29 (2000), S. 231-234 
    ISSN: 1432-2161
    Keywords: Key words Hemangioma ; Ulna ; CT ; MRI ; X-ray
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  An 18-year-old woman presented with left elbow joint pain. Radiographs and computed tomographic scan showed a well-defined osteolytic lesion of the left ulna associated with a honeycomb appearance on the radiographs. Magnetic resonance images showed intermediate signal intensity on T1-weighted images and mixed intermediate and high signal intensities on T2-weighted images. Only the periphery of the lesion enhanced with intravenously injected gadolinium-diethylenetriamine pentaacetic acid. The lesion was curetted to avoid pathologic fracture, and a histologic diagnosis of cavernous hemangioma of bone was made. Hemangioma involving the ulna is rare, but should be included in the differential diagnosis of a radiographic osteolytic lesion with a honeycomb appearance.
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  • 84
    ISSN: 1432-2161
    Keywords: Key words Soft tissue neoplasm ; Metastasis ; MRI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Objective. To describe a series of patients with no known primary malignancy who presented with a solitary unsuspected soft tissue metastasis masquerading as a soft tissue sarcoma, and secondarily to describe the imaging appearance of these lesions. Design. Records of two academic hospitals with active orthopedic oncology services were reviewed for patients meeting the above criteria. Clinical charts were examined, and the imaging appearance of the soft tissue lesions retrospectively reviewed. Patients. Of 1421 patients examined for soft tissue lesions, 11 were found who met the above criteria. Results. Of the 11 patients whose initial presentation was a solitary soft tissue metastasis, eight were found to have a primary lung cancer, two were diagnosed with adenocarcinoma of unknown primary, and adenocarcinoma of the colon was discovered in the remaining patient. Conclusions. The clinical presentation of a solitary soft tissue metastasis without a known primary malignancy is a rare occurrence, with an incidence of approximately 0.8%. Lung cancer is the primary neoplasm in a high percentage of these cases.
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    Skeletal radiology 29 (2000), S. 293-297 
    ISSN: 1432-2161
    Keywords: Key words Angiomyolipoma (AML) ; Soft tissue ; Thigh ; MRI ; CT ; Angiography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  A 41-year-old man presented with an asymptomatic mass in the right medial thigh. Magnetic resonance imaging (MRI) revealed a well-demarcated, 10-cm mass in the right adductor muscles. The margins of the mass exhibited high signal intensity and the rest showed low or iso signal intensity on T1-weighted MR images. However, the high signal intensity was decreased on T2-weighted images with fat suppression. The central part of the tumor was of inhomogeneous high signal intensity on T2-weighted images; after Gd-DTPA injection it enhanced inhomogeneously on T1-weighted images with fat suppression. On dynamic computed tomography (CT) in the arterial phase, there were strongly enhancing spotty areas in the tumor. At surgery, a yellow-whitish tumor was resected and a pathological diagnosis of angiomyolipoma (AML) in the thigh was made.
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  • 86
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    Skeletal radiology 29 (2000), S. 346-348 
    ISSN: 1432-2161
    Keywords: Key words Amyloid tumor ; Tibia ; Periosteum ; Bilateral ; MRI ; Bilateral metachronous periosteal tibial amyloid tumors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Localized primary periosteal amyloid tumors are extremely rare. A case of bilateral tibial amyloid tumor is presented. A 62-year-old woman initially presented with a painful mass in the anterior aspect of the right leg. There was no evidence of underlying systemic disease, including chronic infection or malignancy. Based on the results of resistance with Congo red staining to treatment with potassium permanganate and positivity for kappa light chain, we classified this particular case as AL-type amyloidosis. The patient noticed a swelling in the opposite leg 2 years later. The second tumor was also an AL-type amyloidoma. Amyloid tumors are generally solitary. This is the first case of bilateral periosteal amyloid tumors of the AL-type occurring in the tibiae.
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  • 87
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    Skeletal radiology 29 (2000), S. 387-391 
    ISSN: 1432-2161
    Keywords: Key words Trauma ; Hand ; Sonography ; Ultrasound ; Annular pulleys ; MRI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Objective. To evaluate the sonographic (US) appearance of digital annular pulley (DAP) tears in high-level rock climbers. Design and patients. We performed a retrospective analysis of the US examinations of 16 high-level rock climbers with clinical signs of DAP lesions. MRI and surgical evaluation were performed in five and three patients respectively. The normal US and MRI appearances of DAP were evaluated in 40 and three normal fingers respectively. Results. Nine of 16 patients presented a DAP tear. In eight subjects (seven with complete tears involving the fourth finger and one the fifth finger), US diagnosis was based on the indirect sign of volar bowstringing of the flexor tendons. Injured pulleys were not appreciated by US. Tears concerned the A2 and A3 in six patients and the A3 and A4 in two patients. A2 pulley thickening and hypoechogenicity compatible with a partial tear was demonstrated in one patient. MRI and surgical data correlated well with the US findings. Four patients had tenosynovitis of the flexor tendons but no evidence of pulley disruption. US examinations of three patients were normal. In the healthy subjects US demonstrated DAP in 16 of 40 digits. Conclusion. US can diagnose DAP tears and correlates with the MRI and surgical data. Because of its low cost and non-invasiveness we suggest US as the first imaging modality in the evaluation of injuries of the digital pulley.
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  • 88
    ISSN: 1432-2161
    Keywords: Key words Bones ; infection ; Bones ; radionuclide studies ; MRI ; comparative studies ; Bones ; MRI studies ; MRI ; extremities ; Bones ; immunoscintigraphy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Objective. A retrospective study of the validity of combined bone scintigraphy (BS) and immunoscintigraphy (IS) using 99mTc-labelled murine antigranulocyte antibodies (MAB) and magnetic resonance imaging (MRI) in chronic post- traumatic osteomyelitis. Design and patients. The results of MRI and combined BS/IS of 19 lesions in 18 patients (13 men, 5 women; mean age 45 years, range 27–65 years) were independently evaluated by two radiologists and one nuclear medicine physician with regard to bone infection activity and extent. The patient group was a highly selective collection of clinical cases: the average number of operations conducted because of relapsing infection was eight (range 2–27), the average time interval between the last surgical intervention and the present study was 6.5 years (range 3 months to 39 years), and from the first operation was 14 years (range 1.5–42 years). Interobserver agreement on MRI was measured by kappa statistics. Sensitivity, specificity, accuracy, positive predictive value (PPV) and negative predictive value (NPV) were calculated for MRI and the nuclear medicine studies. Results. For MRI/nuclear medicine, a sensitivity of 100%/77%, a specificity of 60%/50%, an accuracy of 79%/61%, a PPV of 69%/58% and a NPV of 100%/71% were calculated. Four MR examinations were false positives because of postsurgical granulation tissue. A high degree of interobserver agreement was found on MRI (κ=0.88). A low-grade infection was missed on two scintigrams, while four were false positive because of ectopic haematopoietic bone marrow, and in one examination the anatomical distortion resulted in an inaccurate assignment of the uptake leading to false positive findings. Image analysis was frequently hindered by susceptibility artefacts due to residual abrasions of metallic implants after removal of orthopaedic devices (15/18 patients); this led to limited assessment in 17% (3/18 patients). Conclusion. Acute activity in a chronic osteomyelitis can be excluded with high probability if the MRI findings are negative. In the first postoperative year fibrovascular scar cannot be distinguished accurately from reactivated infection on MRI and scintigraphy may improve the accuracy of diagnosis. MRI is more sensitive in low-grade infection during the later course than combined BS/IS. Scintigraphic errors due to ectopic, peripheral, haematopoietic bone marrow can be corrected by MRI.
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  • 89
    ISSN: 1432-2161
    Keywords: Key words Tuberculosis ; Sternum ; Clavicle ; CT ; MRI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Objective. To describe the imaging findings in sterno-clavicular tubercular involvement. Design and patients. Fifteen patients with pathologically proven tuberculosis of the sternum and clavicle were retrospectively evaluated. Routine radiography, computed tomography (CT) and magnetic resonance imaging (MRI) were used in some or all of the patients. Clinical information and imaging features were evaluated in each case. Results. Eight patients had sterno-clavicular joint (SCJ) involvement, five had isolated sternal involvement and two had isolated clavicular involvement. Seven patients were evaluated with only CT, six with only MRI and two with both. There were eight male and seven female patients, varying in age between 16 and 78 years. Fever, swelling and pain were common presenting symptoms. Two patients were HIV positive. Radiographs were positive in only eight patients. Destruction and signal intensity (SI) changes of the sternum and clavicle, destruction of the cartilage, soft tissue changes representing granulation tissue/abscess, displacement of the adjacent structures (vessels, trachea, etc.) and inflammatory changes in the adjacent structures in the form of cellulitis and myositis were common imaging features. Conclusions. All imaging methods can provide complementary information regarding sterno-clavicular tubercular involvement that is helpful for determination of the therapy. MRI is useful in determining the extent of the lesion, particularly marrow involvement and soft tissue extent.
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  • 90
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    Skeletal radiology 29 (2000), S. 477-480 
    ISSN: 1432-2161
    Keywords: Key words Diabetes mellitus ; Muscle, infarction ; Short T1 ; Hemorrhage ; MRI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  We describe a case of diabetic muscle infarction which had atypical features of hyperintensity of the affected muscle on T1-weighted images. Biopsy was performed which revealed diffuse extensive hemorrhage within the infarcted muscle. We believe increased signal intensity on T1-weighted images should suggest hemorrhage within the infarcted muscle.
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  • 91
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    Skeletal radiology 29 (2000), S. 481-484 
    ISSN: 1432-2161
    Keywords: Key words Meniscal ossicles ; Ultrasound ; CT-arthrography ; MRI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  A case of meniscal ossicles occurring in the left knee of a 23-year-old woman is presented. Radiographs showed two calcified lesions at the posteromedial aspect of the knee which were interpreted as loose bodies. Sonography, computed tomography arthrography and magnetic resonance imaging showed the fragments within the posterior horn of the medial meniscus permitting a diagnosis of meniscal ossicles. These techniques can detect meniscal ossicles and exclude intra-articular loose bodies.
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  • 92
    ISSN: 1432-2161
    Keywords: Key words Clear cell sarcoma ; Malignant melanoma of soft parts ; MRI ; Magnetic resonance ; Neoplasm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Objective. To evaluate MR imaging and pathology findings in order to define the characteristic features of clear cell sarcoma of the soft tissues (malignant melanoma of the soft parts). Design and patients. MR examinations of 21 patients with histologically proven clear cell sarcoma of the musculoskeletal system were retrospectively reviewed and assessed for shape, homogeneity, delineation, signal intensities on T1- and T2-weighted images, contrast enhancement, relationship with adjacent fascia or tendon, secondary bone involvement, and intratumoral necrosis. In 19 cases the pathology findings were available for review and for a comparative MR-pathology study. Results. On T1-weighted images, lesions were isointense (n=3), hypointense (n=7) or slightly hyperintense to muscle (n=11). Immunohistochemical examination was performed in 17 patients. All 17 specimens showed positivity for HMB-45 antibody. In nine of 11 lesions with slightly increased signal intensity on T1-weighted images, a correlative MR imaging-pathology study was possible. All nine were positive to HMB-45 antibody. Conclusions. Clear cell sarcoma of the musculoskeletal system often has a benign-looking appearance on MR images. In up to 52% of patients, this lesion with melanocytic differentiation has slightly increased signal intensity on T1-weighted images compared with muscle. As the presence of this relative higher signal intensity on T1-weighted images is rather specific for tumors displaying melanocytic differentiation, radiologists should familiarize themselves with this rare entity and include it in their differential diagnosis when confronted with a well-defined, homogeneous, strongly enhancing mass with slightly higher signal intensity compared with muscle on native T1-weighted images.
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  • 93
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    Skeletal radiology 29 (2000), S. 227-230 
    ISSN: 1432-2161
    Keywords: Key words Erdheim-Chester Disease ; Lipogranuloma ; MRI ; Muscle ; Rectus femoris
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  We report on a rare manifestation of Erdheim-Chester disease with intramuscular lipogranuloma. The patient was a 66-year-old man who noted a soft tissue mass in the right quadriceps femoris muscle. Radiographs revealed symmetrical osteosclerosis in the diametaphysis of both femora and tibiae. An open biopsy revealed a proliferation of lipid-laden histiocytes in the femoral bone marrow and the quadriceps femoris muscle. To our knowledge, this is the second case of Erdheim-Chester disease involving muscle.
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  • 94
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    Skeletal radiology 29 (2000), S. 235-238 
    ISSN: 1432-2161
    Keywords: Key words Femur echinococcosis ; MRI ; echinococcosis ; Hydatid cyst surgery ; Hydatid cyst ; anticestodal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Magnetic resonance (MR) findings of a rare case of osseous echinococcosis with involvement of the femur are described. Attention is drawn to the typical MR appearances and therapeutic management.
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  • 95
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    Keywords: Key words Tibial deficiency ; Fibular deficiency ; Congenital hip dislocation ; Transverse limb deficiency ; X-ray ; MRI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  We report two similar, but unrelated, patients with congenital bilateral partial deficiencies of the tibia and fibula associated with intact feet. In both patients, the tibia and fibula were absent on initial radiographs, while the femur and the tarsal bones were well developed and there was bilateral teratologic dislocation of the hips. Ultrasound and magnetic resonance imaging (MRI) studies suggested the presence of cartilaginous remnants of the tibia and fibula. There were multidirectional instabilities in the knees and ankles. The clinical and radiological features of these cases are distinct from those of congenital longitudinal deficiency of the tibia, in which the fibula is always preserved, and from longitudinal deficiency of the fibula, in which the tibia is present and the foot is usually involved. We suggest that the bilateral partial deficiencies of the tibia and fibula associated with the intact foot and teratologic dislocation of the hips is a single-entity disorder, possibly categorized as an intercalary transverse deficiency of the lower limb.
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  • 96
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    Keywords: Key words Metastatic bone tumor ; Knee ; Spontaneous osteonecrosis ; MRI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  We report a case of a metastatic bone tumor that mimicked spontaneous osteonecrosis of the medial condyle of the femur on magnetic resonance imaging.
    Type of Medium: Electronic Resource
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  • 97
    ISSN: 1432-2161
    Keywords: Key words Chronic leg ulcers ; Squamous cell carcinoma ; Malignancy ; Snake bite ; X-rays ; MRI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Chronic ulcers of the leg are common in Brazil, perhaps more common than in the developed world. We report a case of a chronic ulcer of the leg following extensive scarring due to a bite by a venomous snake, which eventually led to a squamous cell carcinoma.
    Type of Medium: Electronic Resource
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  • 98
    Electronic Resource
    Electronic Resource
    Springer
    Skeletal radiology 29 (2000), S. 417-420 
    ISSN: 1432-2161
    Keywords: Key words Arm ; Collagenous fibroma ; Desmoplastic fibroblastoma ; Short T2 ; MRI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  A recently proposed addition to fibrous tumors in soft tissue was first described as desmoplastic fibroblastoma and later renamed collagenous fibroma. This tumor is clinically and morphologically distinct and benign. However, only a few series have been reported, and the clinicopathologic features are not widely recognized. We present two cases of collagenous fibroma of the arm. Both patients presented with an enlarging, well-circumscribed and mobile soft tissue mass. Magnetic resonance imaging showed areas of low signal intensity on both T1- and T2-weighted sequences. Needle aspiration cytology revealed nondiagnostic samples because of the low cellularity of the tumors. Each of the resected tumors was composed of low-cellular spindle- to stellate-shaped cells in a fibrous matrix with clear margination. After the marginal excisions, no recurrences were observed. Clinicians should be aware of this entity to prevent overtreatment, because imaging findings and cytologic features are similar to those of desmoid tumor.
    Type of Medium: Electronic Resource
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  • 99
    Electronic Resource
    Electronic Resource
    Springer
    Skeletal radiology 29 (2000), S. 425-438 
    ISSN: 1432-2161
    Keywords: Key words Muscles ; MRI ; Myositis ; Muscles ; Abscess ; Dermatomyositis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Inflammatory myopathies encompass a group of acquired muscle disorders caused by infectious agents (bacteria, viruses, fungi and parasitic agents) or autoimmune processes (polymyositis, dermatomyositis and other types). In suspected infection sonography, CT and MRI are all able to show edema and fluid collections in soft tissues and muscles; sonography and CT may help guidance of a needle aspiration to establish a correct diagnosis. By offering better tissue differentiation, MRI appears to be more efficient than sonography and CT in diagnosing and managing autoimmune myopathies. MRI is indeed very sensitive to the presence of water and edema, and appears to be a very good indicator for an early diagnosis of diseases. MRI may also help to evaluate the extent and number of lesions, to guide a biopsy in an area of active disease and finally to follow the evolution under therapy.
    Type of Medium: Electronic Resource
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  • 100
    Electronic Resource
    Electronic Resource
    Springer
    Skeletal radiology 29 (2000), S. 354-357 
    ISSN: 1432-2161
    Keywords: Key words Intraosseous meningioma ; Microcystic meningioma ; Parietal bone ; X ray ; CT ; MRI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Extradural ectopic meningioma is a rare tumor. We report on an example of microcystic meningioma arising in the skull of an elderly woman. Radiological examination revealed a localized osteolytic lesion in the left parietal bone. At surgery, it was discovered that the tumor was located within the skull without any evidence of extraosseous extension. The light microscopic, immunohistochemical and ultrastructural features were consistent with a microcystic variant of meningioma. To our knowledge, this is the first case of an intraosseous microcystic meningioma, and we believe that this type of meningioma should be considered in the differential diagnoses of myxoid bone tumors of the calvarium.
    Type of Medium: Electronic Resource
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