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Biomedical Engineering, IEEE Transactions on

Issue 9 • Date Sept. 1986

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Displaying Results 1 - 20 of 20
  • IEEE Transactions on Biomedical Engineering - Table of contents

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

    Page(s): c2
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  • FNS Parameter Selection and Upper Limb Characterzation

    Page(s): 809 - 817
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    The design of a controller for functional neuromuscular stimulation requires characterization of the plant, i. e., the neuromuscular system involved. The present paper is concerned with the modeling and identification of the elbow flexion/extension and wrist pronation/supination systems. These movements can be performed successfully by the surface stimulation of the biceps, triceps, and pronator teres. The scatter in the plant parameters between subjects and for a given subject as a function of time, electrode placement, etc., is outlined. The nonlinear muscle gain is approximated by a threshold below which the torque is zero, followed by a linear region. A least squares identification technique using a pseudorandom binary sequence input returned best fit for a third-order model for both the elbow and wrist dynamics. The dependence of the complex poles on the input signal bandwidth and level of coactivation is examined. The differences in parameters between the wrist and elbow systems are calculated. The results are used to establish design requirements for an appropriate controller. View full abstract»

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  • FNS Control Schemes for the Upper Limb

    Page(s): 818 - 828
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    This paper is concerned with the problems of control associated with the application of functional neuromuscular stimulation of the upper limb, concentrating on elbow flexion/extension and wrist pronation/supination. A closed-loop controller is needed in order to overcome the gain nonlinearities and plant dynamic parameter variations. Controllers were developed based on models and parameters previously established. Two controllers are discussed in detail, a thirdorder feedforward controller and a model reference adaptive controller. There were no striking differences in the performances of the thirdorder controllers. The conventional controllers, however, required a lengthy a priori identification procedure each time they were used. This was performed implicitly by the adaptive controller within a few seconds, making it a practical proposition for an FNS controller. View full abstract»

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  • A Discrete-Time Model of Electrcally Stimulated Muscle

    Page(s): 829 - 838
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    A model describing the input/output properties of electrically stimulated isometric muscle is developed and experimentally tested. A discrete-time model gives the force output at the times of stimulation during pulse width modulation of recruitment at fixed stimulus amplitudes and periods. Two elements are necessary in the model: a static nonlinear element followed by a linear dynamic element. The static nonlinearity describes the relationship between pulse width and steady-state force. The dynamic properties are described with less than 10 percent error by a second-order discrete-time deterministic autoregressive moving average (DARMA) model. Exponentially weighted recursive least squares methods allow efficient parameter estimation. Model parameters are found to vary systematically with muscle length and stimulus frequency. Tests comparing actual and simulated feedback control of electrically stimulated muscle indicate that the model is adequate for digital controller design for applications in functional electrical stimulation. View full abstract»

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  • Adaptive Control Technique for Artificial Hearts

    Page(s): 839 - 844
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    This paper is concerned with an adaptive control technique for artificial hearts. The design control strategy is multiobjective: aortic pressure control, atrial pressure control, and pump output flow rate control. A desired control mode can be chosen frQm a console. View full abstract»

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  • Optimal Electrode Designs for Electrosurgery, Defibrillation, and External Cardiac Pacing

    Page(s): 845 - 853
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    We have developed a simple and easily modifiable two-dimensional finite element computer model of the human torso, which allows us to predict current delivery from arbitrarily placed and designed electrodes. Using this model, the performance of many variations from the commonly used gelled-pad electrode, applied to a torso of uniform and isotropic resistivity, has been examined by independently varying the thickness, width, and resistivity of the gel layer, as well as the width of the conducting plate. We compared the electrode performances on the basis of their ability to maintain a uniform current density at the electrode-body interface, which is thought to be of critical concern in avoiding burn, pain, and other complications in electrosurgery, external cardiac pacing, and defibrillation. In addition to studying the effects of geometric and electrical design variations, we have isolated two electrode designs of particular importance: 1) a simple plate electrode with a uniformly high resistivity gel layer and intermediate conducting plate width, which could be used for low-energy applications such as external cardiac pacing, and 2) an annular electrode in which the resistivity of the gel varies as a function of distance to the electrode center, which could be used for high-energy applications such as electrosurgery and defibrillation, as well as for external cardiac pacing. View full abstract»

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  • Effects of Measurement Errors and Noise on MEG Moving Dipole Inverse Solutions

    Page(s): 854 - 861
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    Magnetoencephalograms (MEG's) are increasingly being used with the moving dipole method to localize electrical sources in the brain. In this method, also known as the dipole location method, a dipolar source is moved about in a model of the head while its amplitude and orientation are also adjusted to obtain a solution dipole which gives the least squares error fit between the measured MEG's and those produced by the dipolar source. The accuracy of this solution is affected by various measurement errors such as errors in the size of the measurement grid, size of the head model, etc., and by noise in the measured MEG's. This study uses computer modeling methods to investigate the effects of these factors on the localization accuracy of sources in the cortical region of the brain for several different ways of making MEG measurements using single channel and/or multichannel detectors. View full abstract»

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  • Computer Simulation of the Wolff-Parkinson-White Preexcitation Syndrome with a Modified Miller-Geselowitz Heart Model

    Page(s): 862 - 873
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    The implementation of element-to-element propagation into the Miller-Geselowitz heart model, so as to automatically generate activation isochrones, is described. This implementation was achieved from initiation sites on the endocardial surface of the model via a Huygens' construction, utilizing ellipsoidal propagation wavelets to reflect anisotropic propagation in the myocardium. Isochrones similar to those specified for normal activation of the original Miller-Geselowitz model were obtained, using propagation velocities derived from published propagation velocities measured in isolated tissue. Futther validation of the new model was sought by simulating the Wolff-Parkinson-White syndrome, in which preexcitation of the ventricles of the heart occurs due to an accessory pathway connecting atria and ventricles, resulting in an initial delta wave in the QRS complex of the electrocardiogram. The approximate site of the accessory pathway may be deduced from the subject's body surface potential map pattern during the delta wave, or from the polarities of the delta wave in the 12-lead electrocardiogram, or again from the orientation of the spatial vector-cardiogram during the delta wave. By specifying eight separate accessory pathway initiation sites, followed 40 ms later by normal activation, the isochrones corresponding to preexcitation were simulated. The body surface potential maps, electrocardiograms, and vectorcar-diograms were calculated using an inhomogeneous torso model. View full abstract»

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  • 1/f-Like Scaling in Normal Neutrophil Dynamics: Implications for Hematologic Monitoring

    Page(s): 874 - 876
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    Daily neutrophil counts show considerable variability in normal subjects. The dynamics of these apparently erratic fluctuations have not been characterized. We hypothesized that this variability might reflect the kind of 1/f-like (inverse power-law) spectrum seen in other physiologic processes. Fast Fourier transform analysis of neutrophil count data over 64 consecutive days from four previously reported normal volunteers showed a good fit (r = 0.84; p 0.001) to the predicted power-law regression line (y = ¿1.14x ¿1.05). Further characterization of normal and pathologic neutrophil spectra may have diagnostic value. View full abstract»

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  • A Reliable Myoelectric Signal Detector Based on the Propagation Characteristics of Motor Unit Action Potentials

    Page(s): 876 - 878
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    A method was proposed for detecting and rejecting motion artifacts superimposed on myoelectric (ME) signals which are used in the estimation of muscular activity, in the control of powered prostheses, and in other applications. The method is based on the propagation characteristics of motor unit action potentials derived with multiple surface electrodes placed along the muscle fibers. The contamination of artifacts was detected by the decrease of the normalized correlation coefficient calculated at the time shift corresponding to the potential propagation. The product of two correlated signals was found to be less affected by the artifacts and was a better estimate of muscular activity than the root mean square of the ME signal which is conventionally used in the applications of ME signals. View full abstract»

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  • Estimation of Mechanical Parameters in Multicompartment Models Applied to Normal and Obstructed Lungs During Tidal Breathing

    Page(s): 878 - 887
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    A technique is presented which allows quantitative assessment of the use of parallel compartment models for characterizing pulmonary mechanical function during tidal breathing. A model consisting of a conducting airway leading to two parallel parenchymal regions is used. Numerical simulation and sensitivity analysis indicated that a) the compliance of the conducting airway was not significant under the experimental conditions of interest and that b) estimates of the distribution of central and peripheral resistances would not be precise. The techniques were demonstrated using measurements of transpulmonary pressure, flow, and volume changes during tidal breathing obtained from a human subject with normal lungs and a human subject with obstructed lungs. Optimal estimates of the parameters were obtained by minimizing the difference between the model output and experimental data combined from two breathing frequencies. In the estimation procedure, the sum of the peripheral compliances was constrained to equal the independently measured static lung compliance. This constraint was critical for correct evaluation of nonuniform mechanical lung function. From the parameter estimates, the ratio of parenchymal time constants was about five in the subject with normal lungs and 60 in the subject with obstructed lungs. These results suggest that a full study with several normal and obstructed lung subjects is warranted. View full abstract»

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  • A Microprocessor-Based Two-Channel Thromboelastograph

    Page(s): 887 - 890
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    This paper presents a design for a digital thromboelastograph (TEG). The instrument design is based on the principle of a couette viscometer. The device measures shear elasticity of blood during clot formation. The recording mechanism comprises a two-channel light-beam deflection system and a recording system based on a charge-coupled-device (CCD) array. An 8-bit CMOS microprocessor (NSC800) supervises data acquisition from the CCD array. The two-channel system produces a record on a thermal printer allowing one to observe the time course of coagulation and simultaneously compare two different blood specimens. View full abstract»

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  • A Venturi Suction Electrode Array for Clinical Body Surface Mapping

    Page(s): 891 - 894
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    In order to extend the clinical use of body surface mapping, we developed an efficient lead system which can be used under intensive care circumstances. The array consists of flexible straps with electrodes which are sucked onto the thorax by running pressurized air through venturi ejectors. Major features are: rapid application and removal, high reliability, easy handling, and suitability for repeated use with minimal discomfort to the patient. View full abstract»

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  • Torsades de Pointes: A Characteristic Spectral Pattern in Sudden Cardiac Death

    Page(s): 894 - 896
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    Torsades de pointes type of ventricular tachycardia is represented by a power spectrum with multiple discrete frequency bands. The lowest apparent peak (at 1 Hz) corresponds to the envelope frequency of the oscillating QRS vector. Additional peaks corresponding, respectively, to the heart rate (~4 Hz) and its higher harmonics show a characteristic power scaling which was remarkably similar in three subjects with torsades. The consistency of this spectral pattern may be of diagnostic utility and also suggests, contrary to prevailing theory, that torsades is due to a single process, rather than to multiple ectopic foci. View full abstract»

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  • A Multibus-Compatible Interface to Selected Reading Displays for the Blind

    Page(s): 896 - 898
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    A custom microprocessor-based output interface board for use in a reading aid for the visually impaired is described. The board drives the Optacon, the Stereotoner, and an enlarged Optacon-style LED display in real time under host microprocessor control. It is a versatile tool for simulating and evaluating operational features in blind reading aids. View full abstract»

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  • Experimental Measurement of Impact Pressures Delivered by Oral Water Irrigation Devices

    Page(s): 898 - 900
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    Water irrigation devices (WID's) are widely used in homes and dental clinics across the country for oral hygiene. There have been several reported cases of tissue damage with the use of these devices. In the present investigation, two commercially available oral water irrigation devices were evaluated using engineering techniques. The impact thrusts delivered by these devices were measured at different control settings. Both of the tested commercial oral water irrigation devices were found to exert abnormally high thrust which could cause serious damage to the sulcular epithelium and the underlying tissues. These pressures are far in excess of the pressure intensity necessary to perform the cleaning action. Moreover, the existing designs using reciprocating pumps are unsafe and are potentially dangerous, particularly with small diameter tips. View full abstract»

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  • An Efficient Algorithm for Spectral Analysis of Heart Rate Variability

    Page(s): 900 - 904
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    We present a simple efficient algorithm for the derivation of a heart rate signal from the electrocardiogram. We demonstrate that the amplitude spectrum of this heart rate signal more closely matches that of the input signal to an integral pulse frequency modulation (IPFM) model of the heart's pacemaker than do the spectra of other ECG-derived heart rate signals. The applicability of this algorithm in cross-spectral analysis between heart rate and other physiologic signals is also discussed. View full abstract»

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  • IEEE Transactions on Biomedical Engineering Statement of Editorial Policy

    Page(s): 904-a
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    Freely Available from IEEE
  • Institutional listings

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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