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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Der Radiologe 38 (1998), S. 492-501 
    ISSN: 1432-2102
    Keywords: Schlüsselwörter Osteosarkom ; MR-Bildgebung ; Röntgen ; Key words Osteosarcoma ; MR imaging ; X-ray
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary Osteosarcoma is the most common primary malignant bone tumour with the exception of myeloma. The majority of osteosarcoma cases arise within bone and are called conventional osteosarcoma. Intraosseous variants include telangiectatic, small-cell, low-grade intraosseous and cortical osteosarcoma. Less than 10% of osteosarcomas arise on the surface of bone and are subdivided into periosteal, high-grade surface and parosteal varieties. The imaging features of these subtypes of osteosarcoma are described and the impact on diagnosis highlighted. Using material from over 750 osteosarcomas treated at the author’s centre, this article reviews the role of imaging in the management of this condition. Detection still relies principally on the conventional radiograph with bone scintigraphy and MR imaging useful in occult tumours. Establishing the radiological diagnosis depends on careful analysis of the radiographs, with particular attention paid to the nature and extent of bone destruction, periosteal new bone formation and matrix mineralization. The prudent radiologist will be wary of those bone conditions, such as stress fractures and osteomyelitis, which are frequently mistaken for osteosarcoma. Appropriate surgical staging requires MR imaging of the primary tumour to show the bony and soft tissue extent of the lesion and to confirm/exclude skip metastases and local lymph-node involvement. Staging should also include bone scintigraphy to confirm/exclude multiple lesions and chest CT to confirm/exclude pulmonary metastases. Following definitive surgery, imaging is used in the follow-up to monitor potential local recurrence and the development of pulmonary or osseous metastases.
    Notes: Zusammenfassung Das Osteosarkom ist abgesehen vom Myelom der häufigste primäre bösartige Knochentumor. Die überwiegende Mehrzahl der Osteosarkome kommen innerhalb des Knochens vor und werden „konventionelle Osteosarkome” genannt. Die im Knochen vorkommenden Varianten beinhalten teleangiektatische, kleinzellige, niedrig differenzierte intraossäre und kortikale Osteosarkome. Weniger als 10% der Osteosarkome treten an der Knochenoberfläche auf. Diese werden in periosteale, hochgradig differenzierte, oberflächliche und paraostale Varianten unterteilt. Im folgenden werden Osteosarkom-Bildgebungsmethodik und ihr Einfluß auf Diagnose und Therapie diskutiert. Basis dafür sind 750 Osteosarkomen, die am klinischen Zentrum des Autors behandelt wurden. Die Erkennung des Tumors beruht immer noch auf konventionellen Röntgenaufnahmen, während Knochenszintigraphie und Kernspintomographie helfen, diskrete Tumoren aufzuspüren. Die radiologische Diagnose gründet sich auf sorgfältigen Röntgenbildanalysen, unter spezieller Berücksichtigung von Natur und Ausdehnung der Knochendestruktionen, periostalen Knochenneubildungen und Matrixverkalkungen. Streßfrakturen und Osteomyelitiden können differentialdiagnostische Probleme aufwerfen. Die chirurgische Stadieneinteilung beruht auf der kernspintomographischen Darstellung des Primärtumors. Mit ihrer Hilfe kann das Ausmaß des Tumors in Knochen und Weichteilen erkannt, Metastasen bestätigt oder ausgeschlossen sowie der Befall regionärer Lymphknoten abgegrenzt werden. In die Stadieneinteilung sollte auch Knochenszintigraphie sowie Thoraxcomputertomographie mit einbezogen werden, um multiple Läsionen bzw. Lungenmetastasen auszuschließen. Anschließend an die chirurgische Behandlung wird die Bildgebung in Nachsorgeuntersuchungen eingesetzt, um Lokalrezidive und Lungen- bzw. Knochenmetastasen zu erfassen.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Skeletal radiology 29 (2000), S. 713-716 
    ISSN: 1432-2161
    Keywords: Keywords Synovial sarcoma ; Popliteal cyst ; MR imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Synovial sarcoma is a relatively common soft tissue sarcoma particularly in the adolescent and young adult. We report an unusual case of a synovial sarcoma arising within a popliteal cyst in a 13-year-old female presenting with bilateral popliteal cysts. MR imaging demonstrated the cyst with evidence of subacute haemorrhage and a discrete nodule of tumour.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 18 (1994), S. 163-188 
    ISSN: 0271-2091
    Keywords: Non-linear interaction ; Hydrodynamic ; Spectral ; Finite difference ; Tidal current ; Wind-driven current ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A single-point model in the vertical is used to examine the coupling between tidal currents and wind-driven flows in shallow near-coastal regions. Calculations using both a linear slip and a no-slip condition at the sea bed clearly show that coupling between tidal and wind-driven currents cannot occur in a linear model with a time-independent eddy viscosity. However with a physically more realistic time-varying viscosity related to the flow field, coupling does occur, the magnitude of this non-linear interaction depending upon the change in eddy viscosity over a tidal cycle and the intensity of shear in the vertical. A point model in the vertical with flow induced by an oscillatory pressure gradient and an additional constant wind stress is used to examine the influence of viscosity parametrization and water depth upon this coupling.The solution in the vertical is accomplished using both a functional approach and a finite difference method. Some conclusions as to the relative merits of these approaches, particularly the use of a transformed grid in the case of high-shear surface and bed boundary layers, are made in the paper.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 3 (1983), S. 33-60 
    ISSN: 0271-2091
    Keywords: Vertical ; Eddy ; Viscosity ; Galerkin ; Method ; Hydrodynamic ; Model ; Eigenfunction ; Currents ; Roughness length ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The three dimensional linear hydrodynamic equations which describe wind induced flow in a sea are solved using the Galerkin method. A basis set of eigenfunctions is used in the calculation. These eigenfunctions are determined numerically using an expansion of B-splines.Using the Galerkin method the problem of wind induced flow in a rectangular basin is examined in detail. A no-slip bottom boundary condition with a vertically varying eddy viscosity distribution is employed in the calculation. With a low (of order 1 cm2/s) value of viscosity at the sea bed there is high current shear in this region. Viscosities of the order of 1 cm2/s) value of viscosity at the sea bed there is high current shear in this region. Viscosities of the order of 1 cm2/s near the sea bed together with high current shear in this region are physically realistic and have been observed in the sea.In order to accurately compute the eigenfunctions associated with large (of order 2000 cm2/s at the sea surface to 1 cm2/s at the sea bed) vertical variation of viscosity, an expansion of the order of thirty-five B-splines has to be used. The spline functions are distributed through the vertical so as to give the maximum resolution in the high shear region near the sea bed.Calculations show that in the case of a no-slip bottom boundary condition, with an associated region of high current shear near the sea bed, the Galerkin method with a basis set of the order of ten eigenfunctions (a Galerkin-eigenfunction method) yields an accurate solution of the hydrodynamic equations. However, solving the same problem using the Galerkin method with a basis set of B-splines, requires an expansion of the order of thirty-five spline functions in order to obtain the same accuracy.Comparisons of current profiles and time series of sea surface elevation computed using a model with a slip bottom boundary condition and a model with a no-slip boundary condition have been made. These comparisions show that consistent solutions are obtained from the two models when a physically relistic coefficient of bottom friction is used in the slip model, and a physically realistic bottom roughness length and thickness of the bottom boundary layer are employed in the no-slip model.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 12 (1991), S. 17-41 
    ISSN: 0271-2091
    Keywords: Finite difference ; Hydrodynamic ; Turbulence energy ; Tidal ; Wind wave ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: This paper deals with the numerical solution, using finite difference methods, of the hydrodynamic and turbulence energy equations which describe wind wave and tidally induced flow.Calculations are performed using staggered and non-staggered finite difference grids in the vertical, with various time discretizations of the production and dissipation terms in the turbulence energy equations. It is shown that the time discretization of these terms can significantly influence the stability of the solution. The effect of time filtering on the numerical stability of the solution is also considered. The form of the mixing length is shown to significantly influence the bed stress in wind wave problems.A no-slip condition is applied at the sea bed, and the associated high-shear bottom boundary layer is resolved by transforming the equations onto a logarithmic or log-linear co-ordinate system before applying the finite difference scheme.A computationally economic method is developed which remains stable even when a very fine vertical grid (over 200 points) is used with a time step of up to 30 min.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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