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Biomedical Engineering, IEEE Transactions on

Issue 12 • Date Dec. 1983

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Displaying Results 1 - 21 of 21
  • IEEE Transactions on Biomedical Engineering - Table of contents

    Page(s): c1
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  • IEEE Engineering in Medicine and Biology Society

    Page(s): c2
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  • A Quantitative Model for the Ventricular Response During Atrial Fibrillation

    Page(s): 769 - 781
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    We review the principal statistical properties of the RR interval sequence during atrial fibrillation. A simple quantitative electrophysiologic model is presented which successfully accounts for these statistical features. In this model the atrioventricular junction (AVJ) is treated as a single cell equivalent characterized by a refractory period and spontaneous rate of phase 4 depolarization. The atria are presumed to bombard the AVJ with impulses that arrive randomly in time; each impulse induces a partial depolarization of the AVJ equivalent cell. We show that other models for the ventricular response during atrial fibrillation (e. g., concealed conduction models) do not adequately account for the salient statistical features of the RR interval sequence. The present model may be utilized to characterize a sequence of RR intervals recorded from a given individual in terms of the numerical magnitudes of the model's four parameters: the mean rate at which atrial impulses bombard the AVJ, the relative amplitude of the impulses, the relative rate of spontaneous phase 4 depolarization of the AVJ equivalent cell, and the refractory period of the AVJ equivalent cell. Such a characterization may be useful in studying mechanisms of drug action and interaction, as well as potentially offering a quantitative means for optimizing pharmacologic manangement of chronic atrial fibrillation. View full abstract»

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  • Predicting Final Eye Position Halfway Through a Saccade

    Page(s): 781 - 786
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    When the visual environment is to be changed during a saccadic eye movement, it is useful to predict the final eye position before the eye comes to rest. We have built a microcomputer-based instrument to make such predictions. Two techniques were used: one based on the saccadic peak-velocity versus magnitude relationship, and the second based on peak-velocity occurring in the middle of the saccade. The second technique has been tailored to take advantage of the differences between temporal and nasal saccades. Depending on saccade duration, final eye position was predicted 4 to 60 ms before the end of the saccade. View full abstract»

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  • A Recursive Free-Body Approach to Computer Simulation of Human Postural Dynamics

    Page(s): 787 - 792
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    A recursive, free-body approach to the estimation of joint torques associated with observed motion in linkage mechanisms has recently been shown to be computationally more efficient than any other known approach to this problem. This paper applies this method to the analysis of human postural dynamics and shows how it can also be used to compute accelerations for specified joint torques. The latter calculation, referred to here as the direct dynamics problem, has until now involved symbolic complexity to such an extent as to generally limit computer simulation studies of postural control to very simple models. The model presented in this paper is both straightforward and general, and removes this obstacle to the investigation of possible neural control mechanisms by means of computer simulation. A computationally oriented linearization procedure for the direct dynamics problem is also included in the paper. Finally, example simulation results and corresponding measured body motions for human subjects are presented to validate the method. View full abstract»

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  • A Cardiac Hypothesis for the Origin of EEG Alpha

    Page(s): 793 - 796
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    Major hypotheses for the origin of EEG alpha suggest a neural basis, but omit to consider other electrical and mechanical aspects. A cardiac electromechanical hypothesis is proposed. This hypothesis suggests that the natural mechanical frequency of the skull-brain mass is approximately 10 Hz. This has been determined by model and direct measurement. Membrane, liquid junction, electrode, and static charges exist as nonneural sources of potential in EEG recording. These standing potentials can be modulated by pressure and movement. It is postulated that the arterial pulse shocks the brain mass into oscillation at its natural frequency modulating the nonneural potentials. The arterial pulse has a jitter as great as ±720 electrical degrees at 10 Hz and amplitude jitter of approximately ±10 mmHg. Because of cardiac jitter, the differential aspect of amplification, and mixing of waves in the skull, coherence of alpha with phase of the cardiac cycle could not be demonstrated. The cardiac electromechanical hypothesis may assist others in designing experiments that will establish a valid explanation for the origin of EEG alpha. View full abstract»

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  • A Computational Model of the Electromagnetic Heating of Biological Tissue with Application to Hyperthermic Cancer Therapy

    Page(s): 797 - 805
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    To investigate the potentialities of hyperthermia as a cancer therapy, computer simulations have been performed. This simulation consists of two tuccessive steps. First, the heat generated in a distribution of biological tissue when irradiated by a source of electromagnetic radiation is computed. The mathematical tool for determining the disbution of generated heat is the domain-integral-equation technique. This technique enables us to determine in a body with arbitrary distribution of permittivity and conductivity the electromagnetic field due to prescribed sources. The integral equation is solved numerically by an iterative minimization of the integrated square error. From the computed distribution of generated heat, the temperature distribution follows by solving numerically the pertaining heat transfer problem. The relevant differential equation together with initial and boundary conditions is solved numerically using a finite-element technique in space and a finite-difference technique in time. Numerical results pertaining to the temperature distribution in a model of the human pelvis are presented. View full abstract»

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  • Geometric Deconvolution: A Meta-Algorithm for Limited View Computed Tomography

    Page(s): 806 - 810
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    Images reconstructed using a limited number of projections spanning a narrow angular range suffer from a systematic geometric distortion due to the two-dimensional point spread function of the reconstruction process. Applying the projection theorem, we show that the problem of removing this distortion reduces to that of estimating the one-dimensional spread function and deconvolving projections computed for a complementary set of new angles from the initial reconstruction. A second reconstruction is performed using the deconvolved projections along with the original set of projections, thus incorporating wider angular coverage. We present here initial results of such geometric deconvolution performed via inverse filtering using fast Fourier transform techniques. While the results are noisy due to well-known problems associated with inverse filtering, they illustrate the plausibility of the underlying ideas. View full abstract»

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  • Application of Phase Analysis of the Frankenhaeuser - Huxley Equations to Determine Threshold Stimulus Amplitudes

    Page(s): 810 - 818
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    Applications of the Frankenhaeuser-Huxley model of myelinated nerve have been presented in the literature which involve the determination of threshold amplitudes of current stimuli as a function of various physical parameters. There is no known analytic solution to the equations describing the model, and so threshold amplitudes must be determined by repeated numerical solution of the five-equation model. Previous definitions of threshold rely upon a stimulus-response curve to define threshold stimulus amplitude. It is shown that knowledge of the phase behavior of the model leads to a threshold definition based upon the phase trajectories in a reduced phase plane. This phase-based definition is shown to have advantages in terms of lack of ambiguity and markedly increased computational efficiency. The model is shown to be a member of the quasi-threshold phenomenon class of excitable systems. View full abstract»

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  • Dual Microcomputer Analysis of Cardiac Transmembrane Action Potentials

    Page(s): 819 - 825
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    A dual microcomputer system has been developed for automating the analysis of cardiac transmembrane action potentials. This system consists of two microcomputers and supporting function modules which digitize, detect, analyze, and plot the transmembrane action potentials from a cardiac cell impaled with a microelectrode. The action potentials are digitized at two sampling rates for computer processing; a sampling rate of 10 kHz is used to obtain the rapid initial upstroke, while a rate of 100 Hz is used to obtain the slower repolarization phase. The action potentials are characterized by graphic displays using the derived measurements. The system measures the resting potential, overshoot amplitude, dV/dtmax and time for 50, 70, and 95 percent repolarization of the action potential. View full abstract»

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  • Standard Errors on Respiratory Mechanical Parameters Obtained by Forced Random Excitation

    Page(s): 826 - 832
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    Equations describing the standard errors of forced random impedance data and derived parameters in terms of various data collection and data processing factors were developed and verified. The equation indicate that to obtain reliable estimates: 1) 16 ensembles are adequate when coherence is greater than 0.9, and that 32 ensembles are adequate when the coherence is between 0.8 and 0.9; 2) the impedance of the bias tube should be at least two times the impedance of the respiratory system in the bandwidth of the applied noise; and 3) the spectrum should include at least 20 frequencies with at least 2 and preferably more below 10 Hz. Fortunately, all of these constraints can be satisfied with most subjects. This analysis also provides a basis for using weighted regression in estimating resistance, inertance, and compliance parameters, and for separating observed parameter variability into methodological and physiological components. View full abstract»

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  • Weak Electric Fields Affect Plant Development

    Page(s): 833 - 834
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    High-strength electric currents and fields can alter plant physiology by the production of heat within the plant tissue and by the ionization of air molecules at the plant tips. It has been suggested that weak low-frequency electric and magnetic filelds may alter germination and early plant development [4], [5], but the question has not been resolved. Our aim was to determine the possible existence of weak electric-field effects on sunflower germination and to calculate the electric-field threshold inside the seed for any such effects. We found that an applied electric field of 5 kV/m, 60 Hz, produced an internal electric field of 7.5 ×10-4 V/m in a seed in moist soil and resulted in a statistically significant decrease of about 5 percent in germination rate. No effect was found for an applied field of 1 kV/m (1.5 ×10-4 V/m inside the seed). These results established for the first time that electric fields can affect plants by a nonthermal mechanism other than air ionization. View full abstract»

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  • Microwave Coagulating Scalpel

    Page(s): 834 - 836
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    We present an initial report on the design and performance of a device which combines the heating and coagulating effects of a microwave field with the surgical scalpel. The device is intended to control hemorrhage in the surgical treatment of highly vascular organs such as the spleen and liver. Preliminary experiments in splenic surgery using dogs have indicated the utility of this technique. View full abstract»

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  • Generation of the State Sensitivity Functions of a Systemic Arterial Model

    Page(s): 836 - 838
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    Five third-order sensitivity models have been used in [2] to generate the state sensitivity functions of a third-order lumped-parameter system of the modified "Windkessel" systemic arterial model. It is shown under reasonable assumptions that only one sensitivity model of the same order is actually needed to generate the state sensitivity functions with respect to all parameters for the class of systems to which the systemic arterial model belongs. View full abstract»

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  • Image Reconstruction from Incomplete Projection Data: Iterative Reconstruction-Reprojection Techniques

    Page(s): 838 - 841
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    This paper addresses the task of image reconstruction from an incomplete set of projection data. Several methods which first estimate the missing data and then utilize standard reconstruction algorithms to obtain an image are investigated. Results from simulations are presented which illustrate the difficulty in comparing algorithms objectively, particularly when a simple test phantom is chosen. The incorporation of a priori information into the algorithm, an approach which has previously been discussed in the literature, is shown to produce faster convergence. View full abstract»

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  • Announcement Applications Invited for Transactions Editor

    Page(s): 12-a
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  • Call for Papers

    Page(s): 12-b
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  • Call for Papers Special Issue on Software for Medical Care and Medical Science

    Page(s): 12-c
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  • IEEE Transactions on Biomedical Engineering Statement of Editorial Policy

    Page(s): 12-d
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  • Institutional listings

    Page(s): 12e
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Aims & Scope

IEEE Transactions on Biomedical Engineering contains basic and applied papers dealing with biomedical engineering. Papers range from engineering development in methods and techniques with biomedical applications to experimental and clinical investigations with engineering contributions.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Bin He
Department of Biomedical Engineering