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Digitized X-ray angiograms of the left ventricle were clustered using a weighted Euclidean distance criterion with the constraint that the pixels in a cluster are spatially coherent. A three-dimensional feature space was used: position along x and y coordinates and image intensity. The spatial coherence constraint is based upon the belief that pixels within a cluster should be coherent in a spatial...
A novel thresholding method to separate the myocardium of correct thickness from a sequence of two-dimensional echocardiograms is presented. The threshold is made adaptive by maintaining a constant wall width ratio throughout the image sequence. The width ratio is computed at an interactively indicated wall section where the wall width is known a priori. The method is well suited for detecting the...
The Hurst coefficient H can be interpreted as a measure of the texture contained within an image. In this work, the analysis of texture is applied to bone sections in an attempt to quantify calcification. Because the bone structure is generally nonisotropic, a radially oriented implementation of a maximum likelihood estimator for the Hurst coefficient H is proposed to determine a directionally dependent...
The authors studied certain characteristics of the expectation-maximization (EM) algorithm for image reconstruction in positron emission tomography (PET). They have attempted to speed up the algorithm by performing some time-consuming computation only once, at the initiation stage. They have studied the resulting memory size, disk space, and CPU requirements versus the number of pixels in the reconstructed...
A framework for automatically tracking tag lines from a sequence of magnetic resonance (MR) images is described. MR tagging is used to create a spatial pattern of varying magnetization so that objects which may otherwise have small intensity variation are textured. The algorithm presented here uses a dynamic programming solution to a variational integral for energy minimization of curves, where the...
The problem of tracking left-ventricular (LV) endocardial motion from medical images is addressed. This approach accounts for information over two spatial dimensions and time in formulating a displacement flow field of the LV wall viewed as a deformable contour. A two-stage approach consisting of shape-based matching followed by smoothing of the resultant vectors over pairs of successive contours...
A computationally intensive approach to three-dimensional cardiac magnetic resonance (MR) reconstruction is described. This technique used semitransparent surface rendering to give a view of human left and right blood pools within the cardiac structure. Blood was given a colored solid surface, while the cardiac wall was semitransparent.<<ETX>>
An extension to a probability density function (PDF)-based analysis of medical images is discussed. The PDF of interest is that of fractional Brownian motion, and the extension is a reformulation of the problem to explicitly exploit two-dimensional data. It is found that the resulting segmentation can be much more accurate than previous methods. However, due to the computational intensity of the problem,...
The segmentation process is formulated as a configurational optimization problem that is solved using simulated annealing optimization methods. This allows information about the degree of correspondence between a candidate segment and an assumed textural model, as well as morphological information about the candidate segment to be used in the segmentation process. To apply this optimization method,...
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