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The authors describe the coordinate system transformations necessary to reformat published anthropometric data for inclusion in a predefined 3-D body model. A 3-D dynamic model requires input from several sources that often have different frames of reference. Through a series of coordinate transformations and data manipulations, the various frames of reference can be brought into coincidence. This...
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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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Summary form only given. Burn wounds are imaged with an infrared charge-coupled device camera. The camera is composed of an 320*244 array of platinum silicide Schottky-barrier infrared detectors, operating at liquid nitrogen temperature. The system operates in the medium wavelength infrared range of 3-5 mu m. With careful calibration and adjustments, a black-and-white image composed of 256 gray levels...
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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,...
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Summary form only given. An attempt has been made to construct a mathematical model of the cardiovascular system which will allow one to simulate the effects of changes in one or more hemodynamic parameters on myocardial oxygen supply and demand. The model used is a combination of several models which have been reported in the literature, along with the authors' own modifications.<<ETX>>
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The authors describe a 3-D computer animation of kinematic data with superimposed center of gravity and force vectors on a wire-like figure. This animation is used to provide ease in visualizing kinematic and kinetic data obtained by the motion analysis system at the Biomotion Laboratory at Massachusetts General Hospital. The animation permits qualitative assessment of data validity. In conjunction...
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A system was developed to simulate the operation of an intra-aortic balloon pump (IABP) console, and the corresponding patient response. It displays aortic pressure and left ventricular pressure as sliding waveforms in real-time, as well as all of the IABP controls. The system is designed to execute in a PC architecture. The embedded arterial model is based on a multiple-order nonlinear system model...
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An investigation is being pursued to determine the best pH sensor for assessing tissue viability during the process of reconstructive surgery. Two different pH sensors are being evaluated in a preliminary study designed to improve upon the standard glass pH electrode: an ion-selective field effect transistor (ISFET) sensor and a conventional glass electrode. Preliminary test results show that the...
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Summary form only given. The authors review the properties and functional characteristics of the H/sub 1/ receptor and postulate the nature of the ligand-receptor activation site using molecular modeling techniques. A model of the surface of the active site on the receptor was postulated and constructed using Sybyl software on a personal Iris workstation. The surface properties were inferred using...
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The authors examined the dynamics of an intra aortic balloon (IAB) in the aorta and its effect on the hemodynamic response of the cardiovascular system. A mathematical model was developed and in vivo animal experiments were performed. The model describes the balloon inflation and deflation as an aortic-pressure-dependent wavefront. To validate the model, X-ray images and hemodynamic waveforms were...
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The utility of scanning acoustic microscope (SAM) techniques in developing acoustic impedance maps of bone cross sections has been demonstrated experimentally. The relatively inexpensive acoustic scanner has a resolution suitable for detecting subtle local changes in acoustic impedance and, hence, elastic properties. For instance, the significantly lower C33 properties in the posterior region of the...
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An oscillating tribometer was used to investigate the wear mechanisms of TiN (titanium nitride) on UHMWPe (ultra high-molecular-weight polyethylene), oscillating either a coating/substrate system (TiN/Ti-6Al-4V) or a CoCr (cobalt chromium) coupon, for control, on three pins of UHMWPe in a planar configuration. Oscillations were carried out to 10-million cycles in order to discover and evaluate long-term...
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The characteristics of physical manual dexterity are defined and analyzed to provide the basis for a numerical rating system. Physical manual dexterity is based on the actual functionality and fitness of the hand and is assessed independently of higher neural ability. A method has been developed to test and analyze define characteristics. This method is expanded and integrated into a quantitative...
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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...
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A noninvasive, psychophysiologic measurement paradigm was used to examine the effects of autonomic activity on electrocardiographic T-wave amplitude and heart rate. Sympathetic nervous system activity was manipulated by having subjects perform a difficult mental arithmetic task. Parasympathetic influences were inferred by measuring respiratory sinus arrhythmia. Preliminary results suggest that both...
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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...
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Sounds created by a controlled occlusion in the femoral artery of dogs were detected and analyzed by using the fast Fourier transform and autoregressive methods after adaptive filtering. The femoral vessel size and flow were chosen to approximate coronary artery conditions in patients. This work was done to confirm the hypothesis that coronary stenosis produces a detachable auditory correlate. Results...
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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>>
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The elastic mechanical properties of the cardiac myocyte membrane has been evaluated in terms of membrane stiffness and elastic moduli defined by area compressibility and shear strain. The method employed incorporates a membrane patch clamp system and micropipette aspiration, whereby negative pressure is applied to the membrane in the 10-60 mm Hg range. Calibration of the micromanipulation technique,...
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Increased afterload is normally associated with vasoconstriction. The heart has to increase its work to overcome this load, which can be reduced with vasodilators. The forward and reflected waves are computed for the vasoconstriction-induced hypertension and subsequent vasodilation conditions. Results show that the increased and decreased work output by the left ventricle is principally modulated...
