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  • 2025-2025
  • 2010-2014
  • 2005-2009
  • 2000-2004  (237)
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  • 1
    Publication Date: 2014-02-26
    Description: Zeitschriften und andere Medien werden in wachsendem Maße elektronisch publiziert. Hier entsteht für die Bibliotheken, welche diese Online-Publikationen ihren Lesern zur Verfügung stellen, ein neuer Bereich der Informationsvermittlung. Mit dem aufkommenden Standard der OpenURL ergeben sich neue Möglichkeiten, dem Benutzer weiterführende Links und Dienste anzubieten. Das Document-Linking-System SFX der Firma Ex Libris ist die erste und bekannteste Anwendung, die ein Managementsystem fr die Auswertung der OpenURL implementiert. Im Rahmen eines Projektes hat die Zentrale des Kooperativen Bibliotheksverbundes Berlin-Brandenburg (KOBV) eine Evaluation von SFX durchgeführt. Als Ergebnis der Evaluation sollten Einsatzmöglichkeiten von SFX für die KOBV-Suchmaschine und in den lokalen Bibliothekssystemen und Informationsportalen aufgezeigt werden. Im Verlauf des Projektes hat sich das Produkt SFX als eine stabile Anwendung erwiesen, die dem Benutzer interessante zusätzliche Dienste bieten kann.
    Keywords: ddc:000
    Language: German
    Type: reportzib , doc-type:preprint
    Format: application/postscript
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  • 2
    Publication Date: 2014-02-26
    Description: In this work we present an approach for the sensitivity analysis of linearly-implicit differential-algebraic equation systems. Solutions for both, states and sensitivities are obtained by applying an extrapolated linearly implicit Euler discretization scheme. This approach is compared to the widely used sensitivity extensions of multi-step BDF methods by means of case studies. Especially, we point out the benefit of this method in the context of dynamic optimization using the sequential approach.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 3
    Publication Date: 2014-09-30
    Description: Decomposition of the high dimensional conformational space of bio-molecules into metastable subsets is used for data reduction of long molecular trajectories in order to facilitate chemical analysis and to improve convergence of simulations within these subsets. The metastability is identified by the Perron-cluster cluster analysis of a Markov process that generates the thermodynamic distribution. A necessary prerequisite of this analysis is the discretization of the conformational space. A combinatorial approach via discretization of each degree of freedom will end in the so called ''curse of dimension''. In the following paper we analyze Hybrid Monte Carlo simulations of small, drug-like biomolecules and focus on the dihedral degrees of freedom as indicators of conformational changes. To avoid the ''curse of dimension'', the projection of the underlying Markov operator on each dihedral is analyzed according to its metastability. In each decomposition step of a recursive procedure, those significant dihedrals, which indicate high metastability, are used for further decomposition. The procedure is introduced as part of a hierarchical protocol of simulations at different temperatures. The convergence of simulations within metastable subsets is used as an ''a posteriori'' criterion for a successful identification of metastability. All results are presented with the visualization program AmiraMol.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 4
    Publication Date: 2019-05-10
    Description: The adaptive finite element code {\sc Kardos} solves nonlinear parabolic systems of partial differential equations. It is applied to a wide range of problems from physics, chemistry, and engineering in one, two, or three space dimensions. The implementation is based on the programming language C. Adaptive finite element techniques are employed to provide solvers of optimal complexity. This implies a posteriori error estimation, local mesh refinement, and preconditioning of linear systems. Linearely implicit time integrators of {\em Rosenbrock} type allow for controlling the time steps adaptively and for solving nonlinear problems without using {\em Newton's} iterations. The program has proved to be robust and reliable. The user's guide explains all details a user of {\sc Kardos} has to consider: the description of the partial differential equations with their boundary and initial conditions, the triangulation of the domain, and the setting of parameters controlling the numerical algorithm. A couple of examples makes familiar to problems which were treated with {\sc Kardos}. We are extending this guide continuously. The latest version is available by network: {\begin{rawhtml} 〈A href="http://www.zib.de/Numerik/software/kardos/"〉 〈i〉 Downloads.〈/i〉〈/a〉 \end{rawhtml}}
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 5
    Publication Date: 2016-06-09
    Description: This article studies the relation of the two scientific languages Chemistry and Mathematics via three selected comparisons: (a) QSSA versus dynamic ILDM in reaction kinetics, (b) lumping versus discrete Galerkin methods in polymer chemistry, and (c) geometrical conformations versus metastable conformations in drug design. The common clear message from these comparisons is that chemical intuition may pave the way for mathematical concepts just as chemical concepts may gain from mathematical precisioning. Along this line, significant improvements in chemical research and engineering have already been possible -- and can be further expected in the future from the dialogue between the two scientific languages.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 6
    Publication Date: 2014-11-10
    Description: Several sets of reductions rules are known for preprocessing a graph when computing its treewidth. In this paper, we give reduction rules for a weighted variant of treewidth, motivated by the analysis of algorithms for probabilistic networks. We present two general reduction rules that are safe for weighted treewidth. They generalise many of the existing reduction rules for treewidth. Experimental results show that these reduction rules can significantly reduce the problem size for several instances of real-life probabilistic networks.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 7
    Publication Date: 2014-02-26
    Description: Signaling is crucial to the operation of modern telecommunication networks. A breakdown in the signaling infrastructure typically causes customer service failures, incurs revenue losses, and hampers the company image. Therefore, the signaling network has to be highest reliability and survivability. This in particular holds for the routers in such a network, called \textit{signaling transfer points\/} (STPs). The robustness of an STP can be improved by equally distributing the load over the internal processing units. Several constraints have to be taken into account. The load of the links connected to a processing unit changes over time introducing an imbalance of the load. In this paper, we show how integer linear programming can be applied to reduce the imbalance within an STP, while keeping the number of changes small. Two alternative models are presented. Computational experiments validate the integer programming approach in practice. The GSM network operator E-Plus saves substantial amounts of time and money by employing the proposed approach.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 8
    facet.materialart.
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    Publication Date: 2019-10-24
    Keywords: ddc:000
    Language: German
    Type: annualzib , doc-type:report
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  • 9
    Publication Date: 2020-11-13
    Description: In the problem of \emph{Online Call Admission in Optical Networks}, briefly called \textsc{oca}, we are given a graph $G=(V,E)$ together with a set of wavelengths~$W$ and a finite sequence $\sigma=r_1,r_2,\dots$ of calls which arrive in an online fashion. Each call~$r_j$ specifies a pair of nodes to be connected and an integral demand indicating the number of required lightpaths. A lightpath is a path in~$G$ together with a wavelength~$\lambda \in W$. Upon arrival of a call, an online algorithm must decide immediately and irrevocably whether to accept or to reject the call without any knowledge of calls which appear later in the sequence. If the call is accepted, the algorithm must provide the requested number of lightpaths to connect the specified nodes. The essential restriction is the wavelength conflict constraint: each wavelength is available only once per edge, which implies that two lightpaths sharing an edge must have different wavelengths. Each accepted call contributes a benefit equal to its demand to the overall profit. The objective in \textsc{oca} is to maximize the overall profit. Competitive algorithms for \textsc{oca} have been known for the special case where every call requests just a single lightpath. In this paper we present the first competitive online algorithms for the general case of larger demands.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 10
    Publication Date: 2020-11-13
    Description: Traditional optimization techniques assume, in general, knowledge of all data of a problem instance. There are many cases in practice, however, where decisions have to be made before complete information about the data is available. In fact, it may be necessary to produce a part of the problem solution as soon as a new piece of information becomes known. This is called an \emph{online situation}, and an algorithm is termed \emph{online}, if it makes a decision (computes a partial solution) whenever a new piece of data requests an action. \emph{Competitive analysis} has become a standard yardstick to measure the quality of online algorithms. One compares the solution produced by an online algorithm to that of an optimal (clairvoyant) offline algorithm. An online algorithm is called $c$-competitive if on every input the solution it produces has cost'' at most $c$~times that of the optimal offline algorithm. This situation can be imagined as a game between an online player and a malicious adversary. Although competitive analysis is a worst-case analysis and henceforth pessimistic, it often allows important insights into the problem structure. One can obtain an idea about what kind of strategies are promising for real-world systems and why. On the other hand there are also cases where the offline adversary is simply too powerful and allows only trivial competitiveness results. This phenomenon is called hitting the triviality barrier''. We investigate several online problems by means of competitive analysis. We also introduce new concepts to overcome the weaknesses of the standard approach and to go beyond the triviality barrier.
    Keywords: ddc:000
    Language: English
    Type: doctoralthesis , doc-type:doctoralThesis
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  • 11
    Publication Date: 2014-02-26
    Description: The paper deals with the two-class priority M/M/1 system, where the prioritized class-1 customers are served under FCFS preemptive resume discipline and may become impatient during their waiting for service with generally distributed maximal waiting times but finite expectation. The class-2 customers have no impatience. The required mean service times may depend on the class of the customer. As the dynamics of class-1 customers are related to the well analyzed M/M/1+GI system, our aim is to derive characteristics for class-2 customers and for the whole system. The solution of the balance equations for the partial probability generating functions of the detailed system state process is given in terms of the weak solution of a family of boundary value problems for ordinary differential equations. By means of this solution formulae for the joint occupancy distribution and for the sojourn and waiting times of class-2 customers are derived generalizing results recently obtained by Choi et al. in case of deterministic maximal waiting times. For deterministic maximal waiting times partially new explicit formulae are given.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 12
    Publication Date: 2016-06-09
    Description: The bio-heat transfer equation is a macroscopic model for describing the heat transfer in microvascular tissue. So far the deduction of the Helmholtz term in the bio-heat transfer equation is not co role. In view of a future numerical application of this new mathematical model to treatment planning in hyperthermia we derive asymptotic estimates for first and second order correctors.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 13
    Publication Date: 2021-08-05
    Description: Mixed integer programs ($MIPs$) are commonly solved with branch and bound algorithms based on linear programming. The success and the speed of the algorithm strongly depends on the strategy used to select the branching variables. Today's state-of-the-art strategy is called \emph{pseudocost branching} and uses information of previous branchings to determine the current branching. We propose a modification of \emph{pseudocost branching} which we call \emph{history branching}. This strategy has been implemented in $SIP$, a state-of-the-art $MIP$ solver. We give computational results that show the superiority of the new strategy.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 14
    Publication Date: 2020-11-13
    Description: We consider the design of transparent optical networks from a practical perspective. Network operators aim at satisfying the communication demands at minimum cost. Such an optimization involves three interdependent planning issues: the dimensioning of the physical topology, the routing of lightpaths, and the wavelength assignment. Further topics include the reliability of the configuration and sparse wavelength conversion for efficient use of the capacities. In this paper, we investigate this extensive optical network design task. Using a flexible device-based model, we present an integer programming formulation that supports greenfield planning as well as expansion planning on top of an existing network. As solution method, we propose a suitable decomposition approach that separates the wavelength assignment from the dimensioning and routing. Our method in particular provides a lower bound on the total cost which allows to rate the solution quality. Computational experiments on realistic networks approve the solution approach to be appropriate.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 15
    Publication Date: 2020-11-13
    Description: Today's telecommunication networks are configured statically. Whenever a connection is established, the customer has permanent access to it. However, it is observed that usually the connection is not used continuously. At this point, dynamic provisioning could increase the utilization of network resources. WDM based Optical Transport Networks (OTNs) will shortly allow for fast dynamic network reconfiguration. This enables optical broadband leased line services on demand. Since service requests competing for network resources may lead to service blocking, it is vital to use appropriate strategies for routing and wavelength assignment in transparent optical networks. We simulate the service blocking probabilities of various dynamic algorithms for this problem using a well-founded traffic model for two realistic networks. One of the algorithms using shortest path routings performs best on all instances. Surprisingly, the tie-breaking rule between equally short paths in different wavelengths decides between success or failure.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 16
    Publication Date: 2020-11-13
    Description: Nachdem mit der KOBV-Suchmaschine die Online-Recherche in den wichtigsten Berliner und Brandenburgischen Bibliotheken realisiert ist, gehört der Aufbau der Online-Fernleihe als einer neuen, nutzerfreundlichen Dienstleistung zu den drängendsten Desideraten des KOBV. Dem Nutzer soll ein komfortabler Service geboten werden, der ihm im Anschluss an eine erfolgreiche Recherche die nahtlose - per Knopfdruck ausgelöste - Fernleih-Bestellung auf das gewünschte Medium erlaubt. Gleichzeitig trägt die Ablösung des traditionellen, per Post und Bücherauto versandten Roten Fernleihscheines durch eine sekundenschnelle Online-Kommunikation zu einer erheblichen Beschleunigung des Fernleih-Verfahrens bei. Der KOBV beteiligt sich an der Initiative der deutschen Bibliotheksverbünde zur Automatisierung und Beschleunigung der Fernleihe. Die Realisierung soll im KOBV in einem zweistufigen Verfahren erfolgen: (1) verbundinterne Fernleihe im KOBV und (2) verbundübergreifende Fernleihe in der Zusammenarbeit mit den anderen Verbünden. Eine Verbund-Fernleih-Software für den KOBV muss insbesondere den KOBV-spezifischen Gegebenheiten genügen, die in dieser Form in den anderen deutschen Verbünden nicht anzutreffen sind. Im Jahre 2001 hat eine KOBV-Arbeitsgruppe Spezifikationen für eine Verbund-Fernleih-Software erarbeitet, in der die Besonderheiten des KOBV mit berücksichtigt sind. Beim Aufbau der automatisierten Fernleihe als einer regulären KOBV-Dienstleistung geht es nicht allein darum, einen schnellen, komfortablen Service für Nutzer einzurichten, sondern darüber hinaus um eine weitreichende Rationalisierung innerhalb der Bibliotheken. Das vorliegende Spezifikationspapier zielt auf beide Faktoren ab, indem es die Fernleihe als integrierten Dienst entwirft, der von der Bestellung bis zur Bereitstellung des Mediums in der gebenden Bibliothek automatisiert - ohne manuelles Eingreifen der Fernleihstelle - abläuft: die jetzige manuell durchgeführte Fernleihe wird durch die automatisierte Fernleihe abgelöst.
    Keywords: ddc:000
    Language: German
    Type: reportzib , doc-type:preprint
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  • 17
    Publication Date: 2020-12-14
    Description: In the online traveling salesman problem $OLTSP$ requests for visits to cities arrive online while the salesman is traveling. We study the $F{\_max}-OLTSP$ where the objective is to minimize the maximum flow time. This objective is particularly interesting for applications. Unfortunately, there can be no competitive algorithm, neither deterministic nor randomized. Hence, competitive analysis fails to distinguish online algorithms. Not even resource augmentation which is helpful in scheduling works as a remedy. This unsatisfactory situation motivates the search for alternative analysis methods. We introduce a natural restriction on the adversary for the $F{\_max}-OLTSP$ on the real line. A \emph{non-abusive adversary} may only move in a direction if there are yet unserved requests on this side. Our main result is an algorithm which achieves a constant competitive ratio against the non-abusive adversary.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 18
    Publication Date: 2016-06-30
    Description: While attribute-value pairs are a popular method to name objects, information retrieval from those attribute-based namespaces is not an easy task. The user has to recall correct attribute names and values and master the syntax and semantics of query formulation. This paper describes hierarchical structures in attribute-based namespaces, shows how to extract them efficiently and evaluates the quality of these structures in an user experiment. It proposes an user interface for browsing attribute-named object sets which makes this task resemble todays file-system browsers and compares the usability of this interface to normal form-based methods in an user study.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 19
    Publication Date: 2014-02-26
    Description: In this paper, we quantify and discuss the physical and surface chemical processes leading to the formation, temporal evolution and sedimentation of dust grains in brown dwarf and giant gas planet atmospheres: nucleation, growth, evaporation and gravitational settling. Considering dust particles of arbitrary sizes in the different hydrodynamical regimes (free molecular flow, laminar flow, turbulent flow), we evaluate the equilibrium drift velocities (final fall speeds) and the growth rates of the particles due to accretion of molecules. We show that a depth-dependent maximum size of the order of $a_{\rm max}\!\approx\!1\,\mu{\rm m\,(upper\ regions)} \ldots 100\,\mu{\rm m\,(lower\ regions)}$ exists, which depends on the condensate and the stellar parameters, beyond which gravitational settling is faster than growth. Larger particles can probably not be formed and sustained in brown dwarf atmospheres. We furthermore argue that the acceleration towards equilibrium drift is always very fast and that the temperature increase of the grains due to the release of latent heat during the growth process is negligible. Based on these findings, we formulate the problem of dust formation coupled to the local element depletion/enrichment of the gas in brown dwarf atmospheres by means of a system of partial differential equations. These equations state an extension of the moment method developed by Gail\plus Sedlmayr\,(1988) with an additional advective term to account for the effect of size-dependent drift velocities of the grains. A dimensionless analysis of the new equations reveals a hierarchy of nucleation $\to$ growth $\to$ drift $\to$ evaporation, which characterises the life cycle of dust grains in brown dwarf atmospheres. The developed moment equations can be included into hydrodynamics or classical stellar atmosphere models. Applications of this description will be presented in a forthcoming paper of this series.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 20
    Publication Date: 2021-01-21
    Description: Global grid environments do not only provide massive aggregated computing power but also an unprecedented amount of distributed storage space. Unfortunately, dynamic changes caused by component failures, local decisions, and irregular data updates make it difficult to efficiently use this capacity. In this paper, we address the problem of improving data availability in the presence of unreliable components. We present an analytical model for determining an optimal combination of distributed replica catalogs, catalog sizes, and replica servers. Empirical simulation results confirm the accuracy of our theoretical analysis. Our model captures the characteristics of highly dynamic environments like peer-to-peer networks, but it can also be applied to more centralized, less dynamic grid environments like the European {\em DataGrid}.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 21
    Publication Date: 2021-01-22
    Description: Das Management von großen Datenmengen spielt eine immer wichtigere Rolle, wie aktuelle Entwicklungen in der Hochenergiephysik [2] zeigen. Für das DataGrid-Projekt zum Beispiel ist es notwendig, große Datenmengen auf mehrere Rechenzentren in Europa zu verteilen und die Daten untereinander zu synchronisieren. Auch innerhalb von Clustern gewinnen mit zunehmender Anzahl der Knoten Werkzeuge zur effizienten Synchronisation und Verteilung von Daten an Bedeutung. Im Rahmen dieser Arbeit wurde ein effizientes Verfahren zur Synchronisation von verteilten Verzeichnisstrukturen entwickelt und implementiert. Mit diesem Verfahren ist es möglich, unabhängige Änderungen an beliebigen Repositories gleichzeitig durchzuführen. Das Verfahren benötigt keine zentrale Instanz, wodurch eine gegenüber vielen existierenden Verfahren verbesserte Skalierbarkeit erreicht werden konnte. Dabei wurden Erkenntnisse aus der Graphentheorie eingesetzt und weiterentwickelt, um die Netzwerktopolo-gie und -handbreiten zwischen den Rechnern zu berücksichtigen. Durch die Verwendung einer Offline-Synchronisation werden Änderungen erst dann an andere Rechner propagiert, wenn der Nutzer dies anstößt. Das kann zum Beispiel nach einer abgeschlossenen Transaktion, die Änderungen an mehreren Dateien beinhaltet, angemessen sein.
    Description: Current developments in high energy physics [2] show that the management of large datasets plays an important role. For the DataGrid project it is necessary to distribute large datasets over several computing centers all over Europe and to synchronize these datasets. Within clusters tools for efficient synchronization and distribution of data become more important, too. In this thesis, a method to synchronize distributed directory structures was developed and implemented which makes it possible to perform independent changes to arbitrary repositories simultaneously. This method needs no central instance and therefore the presented system achieves a better scalability than many existing systems. Knowledge from graph theory was used and improved to take the network topology and the network bandwidth between the computers into account. By using offline synchronization, changes will only be propagated when the user initiates it. This can be reasonable after a completed transaction which consists of changes on several files.
    Keywords: ddc:000
    Language: German
    Type: masterthesis , doc-type:masterThesis
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  • 22
    Publication Date: 2020-11-17
    Description: An instance of the \emph{maximum coverage} problem is given by a set of weighted ground elements and a cost weighted family of subsets of the ground element set. The goal is to select a subfamily of total cost of at most that of a given budget maximizing the weight of the covered elements. We formulate the problem on graphs: In this situation the set of ground elements is specified by the nodes of a graph, while the family of covering sets is restricted to connected subgraphs. We show that on general graphs the problem is polynomial time solvable if restricted to sets of size at most~$2$, but becomes NP-hard if sets of size~$3$ are permitted. On trees, we prove polynomial time solvability if each node appears in a fixed number of sets. In contrast, if vertices are allowed to appear an unbounded number of times, the problem is NP-hard even on stars. We finally give polynomial time algorithms for special cases where the subgraphs form paths and the host graph is a line, a cycle or a star.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 23
    facet.materialart.
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    Publication Date: 2014-02-26
    Description: Hinter der für den Uneingeweihten etwas kryptischen Frage "P = NP?" verbirgt sich das derzeit wichtigste Problem der Komplexitätstheorie. Dieser Artikel erläutert einige Aspekte der Theorie und erklärt informell, was "P = NP?" bedeutet. Es geht nicht nur um komplizierte algorithmische Mathematik und Informatik, sondern um grundsätzliche Fragen unserer Lebensumwelt. Kann man vielleicht beweisen, dass es für viele Probleme unseres Alltags keine effizienten Lösungsmethoden gibt?
    Keywords: ddc:000
    Language: German
    Type: reportzib , doc-type:preprint
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  • 24
    Publication Date: 2020-03-11
    Description: The Cooperative Library Network Berlin-Brandenburg (KOBV) has set the development of a genuine library information portal for the two German Lander (federal states) Berlin and Brandenburg as its main task for the next years. This joined effort is driven by the vision of an user friendly Internet information portal which is accessible anytime, from anywhere in the world. The idea of a regional information portal can be understood as the logically consistent development of the basic ideas of the KOBV. Starting in 1997, the consortia has set the implementation of a virtual OPAC instead of a physical union catalogue as its goal. The result was the KOBV-Search Engine which already has some qualities of a portal itself. The paper begins with initial remarks about the German library world, which do form the background for the project and its initiator - the KOBV consortia. After this preliminary part, different types of portals are introduced. The basic features of the KOBV-Search Engine as one of the cornerstones of the future portal are discussed in the following. The information portal will be much richer in content and services for the end-user. Two aspects are focused on in more detail: the presentation of resources, which becomes a compelling requirement because of the broader range of content and the personalization of services, as one important feature to suit user's individual needs.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 25
    Publication Date: 2019-01-29
    Description: The paper presents a particle method framework for resolving molecular dynamics. Error estimators for both the temporal and spatial discretization are advocated and facilitate a fully adaptive propagation. For time integration, the implicit trapezoidal rule is employed, where an explicit predictor enables large time steps. The framework is developed and exemplified in the context of the classical Liouville equation, where Gaussian phase-space packets are used as particles. Simplified variants are discussed shortly, which should prove to be easily implementable in common molecular dynamics codes. A concept is illustrated by numerical examples for one-dimensional dynamics in double well potential.
    Keywords: ddc:000
    Language: English
    Type: reportzib , doc-type:preprint
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  • 26
    Publication Date: 2019-01-29
    Description: The paper deals with three different Newton algorithms that have recently been worked out in the general frame of affine invariance. Of particular interest is their performance in the numerical solution of discretized boundary value problems (BVPs) for nonlinear partial differential equations (PDEs). Exact Newton methods, where the arising linear systems are solved by direct elimination, and inexact Newton methods, where an inner iteration is used instead, are synoptically presented, both in affine invariant convergence theory and in numerical experiments. The three types of algorithms are: (a) affine covariant (formerly just called affine invariant) Newton algorithms, oriented toward the iterative errors, (b) affine contravariant Newton algorithms, based on iterative residual norms, and (c) affine conjugate Newton algorithms for convex optimization problems and discrete nonlinear elliptic PDEs.
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  • 27
    Publication Date: 2014-02-26
    Description: In Analogie zu den Elektrizitätsnetzen electricity grid), von denen die technische Revolution ausging, wurde der Begriff Computational Grid (kurz Grid) geprägt. Ein wichtiger Bestandteil des Systems liegt im benutzerfreundlichen Zugang und der koordinierten Nutzung der weltweit verteilten Speicherressourcen und Rechnerkapazitäten. Bei der Entwicklung dazu notwendiger Technologien und Software (Middleware) profitiert man von Kenntnissen und Erfahrungen bei der Entwicklung verteilter Algorithmen, dem Software-Engineering und dem Supercomputing.
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    Language: German
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  • 28
    Publication Date: 2020-02-11
    Description: In this article we study the problem of designing a nation-wide communication network. Such networks usually consist of an access layer, a backbone layer, and maybe several intermediate layers. The nodes of each layer must be connected to those of the next layer in a tree-like fashion. The backbone layer has to satisfy certain survivability and routing constraints. Given the node locations, the demands between them, the possible connections and hardware configurations, and various other technical and administrational constraints, the goal is to decide, which node is assigned to which network level, how the nodes are connected, what hardware must be installed, and how traffic is routed in the backbone. Mixed integer linear programming models and solution methods are presented for both the access and the backbone network design problem. The focus is on the design of IP-over-SDH networks, but the access network design model and large parts of the backbone network design models are general and also applicable for other types of communication networks. Results obtained with these methods in the planning of the German research network are presented.
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  • 29
    Publication Date: 2021-02-19
    Description: We present an online algorithm for a real-world vehicle dispatching problem at ADAC, the German Automobile Association.
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  • 30
    Publication Date: 2020-03-11
    Description: Eine fremddatengestützte Katalogisierung bedeutet für die einzelne Bibliothek unbestritten eine Zeit- und Kostenersparnis. Dieser Report beleuchtet die unterschiedlichen Faktoren technischer und organisatorischer Natur, die die Fremddatennutzung in der dezentralen Struktur des Kooperativen Bibliotheksverbundes Berlin-Brandenburg (KOBV) beeinflussen. Die Ausführungen stützen sich im Wesentlichen auf eine Umfrage, die die Autoren im Mai / Juni 2002 unter KOBV-Mitgliedsbibliotheken zum Thema Fremddatennutzung durchgeführt haben. Dargelegt wird, wie komfortabel die in den KOBV-Bibliotheken eingesetzten Bibliotheksinformationssysteme eine fremddatengestützte Katalogisierung erlauben. Diskutiert wird zudem die Software ZACK, die sich als Alternative zu einem eigenen Z39.50-Client zur Datenübernahme anbietet. Erstmals seit Bestehen des Verbundes werden Zahlen veröffentlicht über den Anteil der Bibliotheken, die Fremddaten nutzen und denjenigen, die dieses Angebot nicht wahrnehmen. Dabei wird die Fremddatenutzung differenziert sowohl für den Bereich der Neuaufnahmen als auch für die Retrokatalogisierung. In der weiteren Analyse werden zusätzliche Aspekte betrachtet wie z.B. die verfügbaren bzw. gewünschten Datenbanken im Verhältnis zum sprachlichen Spektrum des erworbenen Katalogisierungsgutes. Eingegangen wird auch auf die von den Bibliotheken genannten Hauptproblemen und die gewünschten zusätzlichen Serviceleistungen auf Seiten der KOBV-Verbundzentrale. Als Ergebnis dieses Status-Quo-Berichts legt das Autorenteam eine Reihe von Empfehlungen vor, die darauf abzielen, auch für KOBV-Bibliotheken in Zukunft eine Fremddatennutzungsquote von 70 - 75 % zu erreichen.
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  • 31
    Publication Date: 2014-02-26
    Description: Substellar atmospheres are cool and dense enough that dust forms very efficiently. As soon as these particles are formed, they sizedependently precipitate due to the large gravity of the objects. Arriving in hot atmospheric layers, the dust evaporates and enriches the gas by those elements from which it has formed. The upper atmospheric layers are depleted by the same elements. Non-continuous and spatially inhomogeneous convective element replenishment, generating a turbulent fluid field, completes the circuit of dust. The formation of dust in substellar atmosphere is described by extending the classical theory of Gail\plus Sedlmayr for the case of different gas and dust velocities. Turbulence is modeled in different scale regimes which reveals turbulence as trigger for dust formation in hot environments. Both mechanisms cause the dust to be present in else wise dust-hostile region: precipitation transports the dust into hot regions, and turbulence allows the formation of dust in there.
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  • 32
    Publication Date: 2014-02-26
    Description: The talk given by the author at the CRM workshop on Superintegrability in Sep.\ 2002 and this related paper report on work in two subjects. One is the collaboration with Vladimir Sokolov and Takayuki Tsuchida in an effort to classify polynomial integrable vector evolution equations. The other is the computer algebra package {\sc Crack} which did the main computations in solving large bi-linear algebraic systems. Although originally designed to solve over-determined systems of partial differential equations a number of extensions made {\sc Crack} a powerful tool for solving systems of bi-linear algebraic equations. Such systems turn up in many different classification problems some of which were investigated by other participants of this workshop. Two additional applications are outlined. In the talk on which this article is based a method to reduce the length of equations was presented which proved to be useful in solving the bi-linear algebraic systems. Due to numerous asked questions about the computer program, a more complete overview is given in the appendix.
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  • 33
    Publication Date: 2020-11-13
    Description: Die KOBV-Suchmaschine hat seit ihrer Inbetriebnahme Ende 1999 entscheidend zur Verbesserung der Informationsinfrastruktur in Berlin und Brandenburg beigetragen. Auf der Basis der offenen Plattform KOBV-Suchmaschine wird die KOBV-Zentrale gemeinsam mit den Bibliotheken in den nächsten Jahren das Dienstleistungsangebot des KOBV und seiner Bibliotheken kontinuierlich erweitern. Dabei sollen die Prinzipien des KOBV - Offenheit, Heterogenität und Dezentralität auf technischer und organisatorischer Ebene - gewahrt bleiben. Die einzelnen KOBV-Bibliotheken werden sich mit ihren Angeboten in unterschiedlicher Weise im Web positionieren. Die Integration auf regionaler Ebene kann und soll die lokalen Angebote nicht künstlich vereinheitlichen. Das kooperative Portal, das in der Region aufgebaut wird, ist als System geplant, in dem zentrales Portal und lokale Portale nicht hierarchisch einander zugeordnet, sondern miteinander vernetzt sind. Das \glqq KOBV-Informationsportal \grqq soll in der KOBV-Zentrale im Rahmen eines wissenschaftlichen Projektes von Mitte 2001 bis Ende 2003 aufgebaut werden. Das vorliegende Papier gibt einen ersten allgemeinen Einblick, welche Funktionen das \glqq KOBV-Informationsporta \grqq umfassen soll und stellt die Teilprojekte der 1. Stufe vor.
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  • 34
    Publication Date: 2014-11-10
    Description: Oriented matroids are combinatorial structures that encode the combinatorics of point configurations. The set of all triangulations of a point configuration depends only on its oriented matroid. We survey the most important ingredients necessary to exploit oriented matroids as a data structure for computing all triangulations of a point configuration, and report on experience with an implementation of these concepts in the software package TOPCOM. Next, we briefly overview the construction and an application of the secondary polytope of a point configuration, and calculate some examples illustrating how our tools were integrated into the {\sc polymake} framework.
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  • 35
    Publication Date: 2014-11-10
    Description: For all perfect graphs, the stable set polytope STAB$(G)$ coincides with the fractional stable set polytope QSTAB$(G)$, whereas STAB$(G) \subset$ QSTAB$(G)$ holds iff $G$ is imperfect. Padberg asked in the early seventies for ``almost'' perfect graphs. He characterized those graphs for which the difference between STAB$(G)$ and QSTAB$(G)$ is smallest possible. We develop this idea further and define three polytopes between STAB$(G)$ and QSTAB$(G)$ by allowing certain sets of cutting planes only to cut off all the fractional vertices of QSTAB$(G)$. The difference between QSTAB$(G)$ and the largest of the three polytopes coinciding with STAB$(G)$ gives some information on the stage of imperfectness of the graph~$G$. We obtain a nested collection of three superclasses of perfect graphs and survey which graphs are known to belong to one of those three superclasses. This answers the question: which graphs are ``almost'' perfect?
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  • 36
    Publication Date: 2020-11-13
    Description: Die Automatisierung von innerbetrieblicher Logistik erfordert -- über die physikalische Steuerung von Geräten hinaus -- auch eine effiziente Organisation der Transporte: ein Aufgabenfeld der kombinatorischen Optimierung. Dieser Artikel illustriert anhand von konkreten Aufgabenstellungen die Online-Problematik (unvollständiges Wissen) sowie die Echtzeit-Problematik (beschränkte Rechenzeit), auf die man in der innerbetrieblichen Logistik trifft. Der Text gibt einen Überblick über allgemeine Konstruktionsprinzipien für Online-Algorithmen und Bewertungsmethoden, die bei der Entscheidung helfen, welche Algorithmen für eine vorliegende Problemstellung geeignet sind.
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    Language: German
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  • 37
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    Publication Date: 2014-11-10
    Description: \We discuss a nested collection of three superclasses of perfect graphs: near-perfect, rank-perfect, and weakly rank-perfect graphs. For that, we start with the description of the stable set polytope for perfect graphs and allow stepwise more general facets for the stable set polytopes of the graphs in each superclass. Membership in those three classes indicates how far a graph is away from being perfect. We investigate for webs and antiwebs to which of the three classes they belong. We provide a complete description of the facets of the stable set polytope for antiwebs (with help of a result due to Shepherd on near-bipartite graphs). The main result is that antiwebs are rankperfect.
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  • 38
    Publication Date: 2021-01-21
    Description: \textsf{\itshape{GuiGen}} is a comprehensive set of tools for creating customized graphical user interfaces (GUIs). It draws from the concept of computing portals, which are here seen as interfaces to application-specific computing services for user communities. While \textsf{\itshape{GuiGen}} was originally designed for the use in computational grids, it can be used in client/server environments as well. Compared to other GUI generators, \textsf{\itshape{GuiGen}} is more versatile and more portable. It can be employed in many different application domains and on different target platforms. With \textsf{\itshape{GuiGen}}, application experts (rather than computer scientists) are able to create their own individually tailored GUIs.
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  • 39
    Publication Date: 2014-02-26
    Description: The purpose of the paper is to formulate and use syzygies for systems of linear PDEs. The computation of an equivalent of a GCD for linear partial differential operators will save us their factorization which is otherwise only possible algorithmically in special cases. After showing the computation with the new and the traditional method and comparing both in the next three sections, the algorithm is explained in general and an overview is given.
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  • 40
    Publication Date: 2020-11-13
    Description: Telekommunikation ist seit Jahren \glqq in\grqq. Zunächst gab es einen enormen Aufschwung; neue Technologien und Dienste haben eine überwältigende, nicht vorhersehbare Akzeptanz gefunden. Derzeit ist -- ausgelöst durch die UMTS-Lizenzversteigerungen, Rezessions- und Sättigungstendenzen -- eine Krise zu verzeichnen. Viele (auch wir) sind davon überzeugt, dass technischer Fortschritt und nützliche Dienste demnächst die Stimmung wieder ändern werden. Wenigen ist allerdings bewusst, welche Rolle Mathematik bei der Entwicklung und dem effizienten Einsatz vieler der neuen Kommunikationstechnologien spielt. In diesem Artikel soll kein Überblick über diesen umfangreichen Themenkreis gegeben werden. Wir zeigen lediglich an einem konkreten Beispiel aus dem Mobilfunk, der Frequenzplanung in GSM-Funknetzen, was man durch geeignete Modellierung der praktischen Fragestellung und den Einsatz problemadäquater Algorithmen erreichen kann.
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    Language: German
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  • 41
    Publication Date: 2020-03-09
    Description: Wir beschreiben einen Ansatz zur integrierten Umlauf- und Dienstplanung im öffentlichen Nahverkehr. Der Ansatz zielt auf die Verbesserung des Gesamtwirkungsgrades dieser beiden Planungsschritte und auf die besondere Planungsproblematik im Regionalverkehr. Wir entwickeln dazu mathematische Optimierungstechniken für den Einsatz in den Planungssystemen MICROBUS II und DIVA.
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  • 42
    Publication Date: 2014-02-26
    Description: A graph property is called elusive (or evasive) if every algorithm for testing this property has to read in the worst case $n\choose 2$ entries of the adjacency matrix of the given graph. Several graph properties have been shown to be elusive, e.g. planarity (Best et al) or $k$-colorability (Bollobas). A famous conjecture of Karp says that every non-trivial monotone graph property is elusive. We prove that a non-monotone but hereditary graph property is elusive: perfectness.
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  • 43
    Publication Date: 2014-02-26
    Description: Recently, a novel approach for the analysis of molecular dynamics on the basis of a transfer operator has been introduced. Therein conformations are considered to be disjoint metastable clusters within position space of a molecule. These clusters are defined by almost invariant characteristic functions that can be computed via {\em Perron Cluster} analysis. The present paper suggests to replace crisp clusters with {\em fuzzy} clusters, i.e. to replace characteristic functions with membership functions. This allows a more sufficient characterization of transiton states between different confor conformations and therefore leads to a better understanding of molecular dynamics. Fur thermore, an indicator for the uniqueness of metastable fuzzy clusters and a fast algorithm for the computation of these clusters are described. Numerical examples are included.
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  • 44
    Publication Date: 2019-01-29
    Description: The paper provides a detailed analysis of a short step interior point algorithm applied to linear control constrained optimal control problems. Using an affine invariant local norm and an inexact Newton corrector, the well-known convergence results from finite dimensional linear programming can be extended to the infinite dimensional setting of optimal control. The present work complements a recent paper of Weiser and Deuflhard, where convergence rates have not been derived. The choice of free parameters, i.e. the corrector accuracy and the number of corrector steps, is discussed.
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  • 45
    Publication Date: 2017-02-21
    Description: Pseudo--transient continuation methods are quite popular for the numerical solution of steady state problems, typically in PDEs. They are based on an embedding into a time dependent initial value problem. In the presence of dynamical invariants the Jacobian matrix of the nonlinear equation system is bound to be singular. The paper presents a convergence analysis which takes this property into account -- in contrast to known approaches. On the basis of the new analysis adaptive algorithms are suggested in detail. These include a variant with Jacobian approximations as well as inexact pseudo--transient continuation, both of which play an important role in discretized PDEs. Numerical experiments are left to future work.
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  • 46
    Publication Date: 2014-02-26
    Description: A beautiful result of Bröcker and Scheiderer on the stability index of basic closed semi-algebraic sets implies, as a very special case, that every $d$-dimensional polyhedron admits a representation as the set of solutions of at most $d(d+1)/2$ polynomial inequalities. Even in this polyhedral case, however, no constructive proof is known, even if the quadratic upper bound is replaced by any bound depending only on the dimension. Here we give, for simple polytopes, an explicit construction of polynomials describing such a polytope. The number of used polynomials is exponential in the dimension, but in the 2- and 3-dimensional case we get the expected number $d(d+1)/2$.
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  • 47
    Publication Date: 2014-11-10
    Description: TOPCOM is a package for computing triangulations of point configurations and oriented matroids. For example, for a point configuration one can compute the chirotope, components of the flip graph of triangulations, enumerate all triangulations. The core algorithms implemented in TOPCOM are described, and implentation issues are discussed.
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  • 48
    Publication Date: 2020-11-13
    Description: A model for the optimisation of the location and configuration of base stations in a UMTS network is described. The focus is primarily on modelling the configuration problem sufficiently accurate using mixed-integer variables and (essentially) linear constraints. These constraints reflect the limited downlink code capacity in each cell, the interference limitations for successful up- and downlink transmissions, the need for sufficiently strong (cell) pilot signals, and the potential gain for mobiles from being in soft(er) hand-over. It is also explained how to use the model as a basis for rating network configurations.
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  • 49
    Publication Date: 2016-06-09
    Description: Computational drug design studies molecular recognition in the {\em virtual lab}. The arising Hamiltonian dynamics is known to be chaotic and ill-conditioned already after picoseconds, whereas times are $msec$ up to $min$. Classical molecular dynamics with long term trajectory computation gives, at best, information about time and statistical ensemble averages. The present paper surveys a recent new modeling approach called {\em conformational dynamics}, which is due to the author and Ch. Schütte. This approach achieves information about the dy time scales by telescoping a short term deterministic model with a statistical model. Examples of small biomolecules are included.
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  • 50
    Publication Date: 2021-02-19
    Description: Combinatorial online optimization is an area with lots of applications and potential for significant progress, both in theory and practice. In this short note we sketch the ADACproblem, a typical large-scale online optimization problem, discuss some theoretical and pratical issues coming up, and explain, very briefly, how we approach this problem mathematically. Online problems are a battlefield of heuristics with many strong claims about their solution quality. We indicate that a stronger problem orientation and the use of a little more mathematics may yield.
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  • 51
    Publication Date: 2014-02-26
    Description: A subset ${\cal C}$ of the power set of a finite set $E$ is called cardinality homogeneous if, whenever ${\cal C}$ contains some set $F$, ${\cal C}$ contains all subsets of $E$ of cardinality $|F|$. Examples of such set systems ${\cal C}$ are the sets of circuits and the sets of cycles of uniform matroids and the sets of all even or of all odd cardinality subsets of $E$. With each cardinality homogeneous set system ${\cal C}$, we associate the polytope $P({\cal C})$, the convex hull of the incidence vectors of all sets in ${\cal C}$, and provide a complete and nonredundant linear description of $P({\cal C})$. We show that a greedy algorithm optimizes any linear function over $P({\cal C})$, give an explicit optimum solution of the dual linear program, and provide a polynomial time separation algorithm for the class of polytopes of type $P({\cal C})$.
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  • 52
    Publication Date: 2014-02-26
    Description: Die Bibliotheken des KOBV haben im Jahr 2001 die Entwicklung der KOBV-Suchmaschine zu einem gemeinsamen Informationsportal Berlin-Brandenburg und den Aufbau lokaler Bibliotheksportale als Hauptentwicklungsziele des KOBV definiert. Diese Informationsportale sollen mit Standardsoftware realisiert werden. Um die Auswahl eines Systems zu unterstützen, wurde in der Zentrale des KOBV ausgewählte Systeme untersucht. In der Arbeit werden zahlreiche Kriterien vorgestellt, auf Grund derer die betreffenden Systeme beurteilt werden. Die Kriterien umfassen sowohl Aspekte aus der Sicht der Benutzer als auch Kriterien aus der Sicht der Betreiber eines solchen Systems. Wesentliche Funktionen und die Realisierung von verschiedenen Merkmalen werden im Bericht ausführlich beschrieben. Daneben liefert eine Tabelle mit allen betrachteten Kriterien eine Übersicht über vorhandene Merkmale und der Art der Realisierung.
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  • 53
    Publication Date: 2021-03-16
    Description: In the cake cutting problem, $n\ge2$ players want to cut a cake into $n$ pieces so that every player gets a ``fair'' share of the cake by his own measure. We describe a protocol with $n-1$~cuts in which each player can enforce to get a share of at least~$1/(2n-2)$. Moreover we show that no protocol with $n-1$~cuts can guarantee a better fraction.
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  • 54
    Publication Date: 2022-07-07
    Description: We present a new efficient algorithm for the solution of direct time-harmonic scattering problems based on the Laplace transform. This method does not rely on an explicit knowledge of a Green function or a series representation of the solution, and it can be used for the solution of problems with radially symmetric potentials and problems with waveguides. The starting point is an alternative characterization of outgoing waves called \emph{pole condition}, which is equivalent to Sommerfeld's radiation condition for problems with radially symmetric potentials. We obtain a new representation formula, which can be used for a numerical evaluation of the exterior field in a postprocessing step. Based on previous theoretical studies, we discuss the numerical realization of our algorithm and compare its performance to the PML method.
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  • 55
    Publication Date: 2022-07-07
    Description: The aim of this paper is to develop fast methods for the solution of nonlinear Schrödinger type equations in fiber optics. Using the method of lines we have to solve a stiff system of ordinary differential equations where the eigenvalues of the Jacobian are close to the imaginary axis. This is usually done by a Split Step method. Here we consider the extrapolation of Split Step methods with adaptive order and step size control. For more complicated nonlinearities, in particular stimulated Raman scattering, Split Step methods are less efficient since symmetry is either destroyed or requires much additional effort. In this case we use implicit Runge Kutta formulas of Gauß type. The key point for the efficient implementation of these methods is that the system of nonlinear algebraic equations can be solved without setting up the Jacobian. The proposed methods are compared to other methods, in particular exponential integrators, the method of Marcuse, and the method of Blow and Wood.
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  • 56
    Publication Date: 2022-07-07
    Description: The work presents a new approach to the numerical solution of time-harmonic and time-dependent scattering problems. We replace Sommerfeld's radiation condition valid for the Helmholtz equation by a more general concept called pole condition. The pole condition is based on the Laplace transform of the exterior solution and allows a characterization of outgoing waves. Both new insight into the analysis of scattering problems as well as new numerical algorithms are obtained.
    Keywords: ddc:000
    Language: English
    Type: doctoralthesis , doc-type:doctoralThesis
    Format: application/postscript
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  • 57
    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.
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  • 58
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    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.
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  • 59
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    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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  • 60
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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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  • 61
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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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  • 62
    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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  • 63
    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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  • 64
    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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  • 65
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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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  • 66
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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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  • 67
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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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  • 68
    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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  • 69
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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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  • 70
    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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  • 71
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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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  • 72
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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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  • 73
    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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  • 74
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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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  • 75
    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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  • 76
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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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  • 77
    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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  • 78
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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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  • 79
    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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  • 80
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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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  • 81
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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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  • 82
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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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  • 83
    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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  • 84
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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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  • 85
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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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  • 86
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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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  • 87
    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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  • 88
    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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    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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  • 90
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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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  • 91
    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.
    Type of Medium: Electronic Resource
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  • 92
    Electronic Resource
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    Springer
    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.
    Type of Medium: Electronic Resource
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  • 93
    Electronic Resource
    Electronic Resource
    Springer
    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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  • 94
    ISSN: 1432-2161
    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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  • 95
    ISSN: 1432-2161
    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.
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  • 96
    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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  • 97
    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.
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  • 98
    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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  • 99
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    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.
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  • 100
    ISSN: 1432-2161
    Keywords: Key words Chondrolipoma ; Liposarcoma ; Mesenchymoma ; Cartilage ; Metaplasia ; MRI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Chondro-osseous differentiation of three benign or malignant fat tissue tumors – two chondrolipomas and a liposarcoma with cartilaginous metaplasia – was studied with magnetic resonance (MR) imaging and compared with their pathological findings. The results suggest that demarcation of cartilage tisssue can be clearly defined on MR imaging when the size of the cartilaginous area is large. Myxoid matrix, degenerative fat tissue and lipodystrophic change may decrease the delineation of the cartilage tissue.
    Type of Medium: Electronic Resource
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