Abstract: Quantitative measurements of perfusion and molecular diffusion were made in human white matter in two orientations of the motion-sensitization gradient to document anisotropy of these parameters. Measurements were localized to a 10 X 10-mm tissue column oriented in an anterior-to-posterior direction in the left cerebral hemisphere just above the body of the left ventricle. This region was selected because of the relatively high directionality of white matter fibers. In this study of five healthy volunteers, strong diffusion anisotropy was observed in all cases. Twofold or greater anisotropy was commonly observed, with the higher diffusion value associated with motion sensitivity along the fiber directions. By combining data from both gradient orientations in all cases, diffusion values of solid tissue ranged from 0.38 X 10(-3) mm2/sec to 1.12 X 10(-3) mm2/sec, and measured perfusion fractions were in the range of 2%-5% (excluding areas highly contaminated by cerebrospinal fluid). Little or no perfusion-fraction anisotropy was observed; however, perfusion measurements were limited by noise. Data were collected without cardiac gating by using a technique that offers good immunity to bulk tissue motion artifacts.

Abstract: We present a global edge detection algorithm based on variational regularization. The algorithm can also be viewed as an anisotropic diffusion method. We thereby unify these two from the original outlook quite different methods. The algorithm to be presented moreover has the following attractive properties: 1) It only requires the solution of a single boundary value problem over the entire image domain—almost always a very simple (rectangular) region. 2) It converges to a solution of interest.

Abstract: The use of magnetic resonance imaging to detect normal and pathological problems of perfusion and diffusion is reviewed. Motion sensitised spin-echo images can be used to detect changes in slow flow velocity within a voxel (intravoxel coherent motion (IVCM) as well as intravoxel incoherent motion (IVIM) effects attributable to both diffusion and perfusion. Changes have been identified in a variety of brain diseases in the absence of changes in conventional images but the techniques are very vulnerable to motion artefact of all types. More rapid and more sensitive approaches using steady state free precision and echo-planer imaging are being investigated. Anisotropic diffusion imaging enables white matter tracts to be demonstrated within the brain and spinal cord as a function of their direction because diffusion of water across axons is much more restricted than it is along them. This technique provides a unique method for localisation of lesions and displays obvious changes in disease in which diffusion becomes less restricted.

Abstract: A method of coding digital image data of an original image for transmission and reproduction. The original image is subdivided into partial image regions whose shapes are adapted to local image structures. For each partial image region, a set of two-dimensional, lineraly independent basis functions is provided. The areal expanse of the basis functions approximately corresponds to the size of a rectangle circumscribing the partial image region to be coded and the raster of the sampled values of the basis functions corresponds to the pixel raster of the original image. The sampled values of the basis functions disposed within the area defined by the partial image region are orthogonalized in order to obtain a set of new, orthogonal basis functions, with the set including as many orthogonal basis functions as there are pixels within the partial image region. Coefficients of the orthogonalized basis functions describing the partial image region are then calculated. The coefficients correspond to the rectangular image regions in the partial image region and represent the gray scale values of the partial image region and thus an approximation of the original image. In a preferred embodiment, the contour of the partial image region is coded and transmitted along with the coefficients to a receiving location, where the orthogonal basis functions are generated based on the contour and the image is reproduced with the orthogonal basis functions and the coefficients.

Abstract: According to the present invention, when image data are subjected to quantization processing using an error diffusion method, the generation of a striped pattern which is a cause for deterioration of picture quality in the error diffusion method is prevented. In the present invention, an original image is read and image data are generated. The image data obtained by reading the original image are quantized using an error diffusion method, and the quantized image data can be output and recorded by a thermal-head printer. Furthermore, according to the present invention, an error between the density of an input image and the density of an output image after being subjected to a quantization processing using an error diffusion method is perfectly preserved. In an image processing apparatus for performing a quantization by dispersing an error between input image data and output image data which arises when the input image data are quantized, to image data of surrounding picture elements, the error between the input image data and the output image data is computed or otherwise determined, the error is subjected to a predetermined weighting processing, the error subjected to the weighting processing is dispersed to surrounding picture elements, and a surplus of the error generated in the weighting processing is corrected.

Abstract: A system and the related software package for interactive echocardiographic image analysis and visualization are illustrated and discussed. The full model for smoothing, edge enhancement, and contour detection is discussed, and a new technique based on the heat anisotropic diffusion model is presented. The results of automatic detection of the left ventricle contours are presented and discussed. >

Abstract: Decomposing each term in the transport equation of the turbulent kinetic energy, an anisotropic k-e model, which is valid right up to the wall, is proposed. The deviation of the Reynolds stress tensor from the common isotropic representation is given as a function of nonlinear quadratic terms of mean velocity gradients as well as anisotropic diffusion terms of turbulent kinetic energy. Trial calculations carried out for two-dimensional turbulent channel flows demostrate that this anisotropic k-e model is able to predict reasonably well the strong anisotropic limiting behavior of the normal Reynolds stresses towards the wall, which cannot be dealt with by the previous isotropic and anlsotropic k- E models.

Abstract: A 2-dimensional steady state latitude/depth advective-diffusive ocean model is formulated. The advecting flow is an idealized thermohaline circulation with upwelling at the low latitudes and downwelling at the high latitudes. Diffusion may occur along geopotential co-ordinates, or along isopycnal surfaces with a constant slope. The latter introduces an anistropy in the governing advection-diffusion equation for a passive tracer. The model is forced at the top with a specified tracer distribution. The sides and bottom are insulating. The equation is scaled to yield two non-dimensional parameters: the Peclet number(Pe), and an isopycnal slope parameter(γ). General results are derived analytically for the diffusive limit(Pe→0). A parameter study is carried out using numerical integration for the non-diffusive cases(Pe≠0). The results are interpreted in terms of the diffusive and advective fluxes, and the homogenization properties of the tracer field.

Abstract: It was investigated the contribution of diffusion-induced structural changes on the anisotropy of P diffusion into the monocrystalline Si. Generation and distribution of dislocations by solute diffusion of phosphorus in silicon (100) and (111) provides for further different depth penetration of diffusion precipitation up to anisotropic diffusion in cubic crystals. [Russian Text Ignored].

Abstract: A simple anisotropic diffusion model, according to semiphenomenological arguments, exhibits long-ranged spatial correlations in uniform stationary states.

Abstract: Motion of a passive component in a periodic incompressible steady flow is studied in the presence of intrinsic diffusivity of a medium. It is rigorously proven that for large distance and time the transport can be described as an effective anisotropic diffusion. Analytical properties of the effective diffusivity Dn* for a given direction n as a function of complex P2 (P is the Peclet number) are discussed. It is shown that the function Dn*(P2) is meromorphic and both poles and zeroes of Dn*(P2) are real and negative. It is proven that Dn* < D(1 + const P2) for any real P. New algorithm based on the continued fractions is given to compute Dn*(P2).