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Supratentorial diffuse astrocytic tumours: proposal of an MRI classification (1997)

Pierallini, A. ; Bonamini, M. ; Bozzao, A. ; [et al.]

Springer

European radiology 7 (1997), S. 395-399

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ISSN: 1432-1084

Keywords: Key words: MRI ; Glioblastoma ; Astrocytoma ; Grading ; Classification

Source: Springer Online Journal Archives 1860-2000

Topics: Medicine

Notes: Abstract. The aim of this study was to obtain an MRI severity-related classification of diffuse astrocytic tumours able to integrate the histological data in the grading of such tumours. We studied presurgical MR images of 91 patients with a histological diagnosis of astrocytoma, anaplastic astrocytoma and glioblastoma. A score ranging from 1 to 3 was assigned by two independent readers to each of the following MR features: oedema, mass effect, contrast enhancement, borders, signal homogeneity, necrosis, haemorrhage and flow void. Statistical analysis showed significant differences in the mean MRI scores between the three histological grades. Contrast enhancement was found to be the best predictor of the histological grade followed by necrosis, signal homogeneity and border scores. This classification represents a simple and reproducible means of carefully evaluating some macroscopic characteristics of these tumours. It could be used to integrate histological data especially in cases in which tissue sampling defects may affect the validity of this examination.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s003300050173

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General considerations of numerical stability and accuracy in inviscid, compressible flow calculations employing primitive variables (1982)

Bosman, C. ; Ahrabian, D. ; Kahrom, M.

Chichester : Wiley-Blackwell

International Journal for Numerical Methods in Fluids 2 (1982), S. 123-149

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ISSN: 0271-2091

Keywords: Three-dimensional ; Flow ; Computation ; Scheme ; Time ; Marching ; Conventional ; Damping ; Old Time Level ; Current Time Level ; Fourier Perturbation ; Staggered Grid ; 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 numerical stability of a number of computation schemes currently used for three-dimensional, inviscid, compressible flow is analysed using one-dimensional Fourier analysis. Whereas Reference 1 analysed schemes which were modified to render them amenable to simple analysis, the present work analyses the stability of schemes as actually used by Highton,3 Ahrabian,1 Denton2 and Spalding.6 The use of current values of the variables as they become available is shown to bring a general improvement to stability margin. The manner of damping introduced by the time marching formulation is shown to be deleterious to modifications which reduce truncation error. Staggered grid schemes can be formulated to second order accuracy with better stability margin than the corresponding first order scheme. While unstaggered grid schemes can be formulated to second order error and remain stable, their stability margin becomes very small. Agreement of the theory with numerical experiments continues to be of a high order for both one and three-dimensional disturbances.

Additional Material: 12 Ill.