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Biomedical Engineering, IEEE Transactions on

Issue 3 • Date May 1978

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Displaying Results 1 - 25 of 30
  • 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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    Freely Available from IEEE
  • Pattern Recognition Techniques for the Detection of Epileptic Transients in EEG

    Page(s): 213 - 217
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    Epileptic transients (ET) in EEG, characterized by their amplitude and duration, are compared to background activity by means of cluster analysis in a two-dimensional amplitude-duration sample space. Decisions between ET and background are then carried out by assigning an optimum boundary between the clusters. By filtering the EEG signal using linear prediction followed by second differentiation, a useful degree of cluster separation is achieved. The probability of correct decisions is thus enhanced. Data for several patients are shown. View full abstract»

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  • Use of Gas Jet Appositional Pressurization in Endoscopic Laser Photocoagulation

    Page(s): 218 - 224
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    A hybrid optical fiber catheter has been developed which is capable of simultaneously emitting from its distal end 20 W of continuous laser radiation and a jet stream of CO2 gas. The catheter can be readily inserted into the biopsy channel of conventional flexible endoscopes for control of gastric bleeding. Experiments on bleeding animal ulcers and an artificial bleeding vessel model show that a catheter which delivers a simultaneous jet of gas with laser radiation is much more effective in achieving hemostasis than laser radiation alone. The laser/gas catheter also incorporates other improvements in device durability. Results of controlled animal trials are discussed. View full abstract»

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  • Analysis of Interactions Between Central and Vagal Respiratory Control Mechanisms in Cats

    Page(s): 225 - 235
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    In anesthetized cats, regulation of the duration of inspiration (Ti) and expiration (Te) has been investigated by analyzing the operation of central inspiratory on-and off-switch mechanisms. Using the tracheal pressure (P) generated during airway occlusion at FRC as a measure of central inspiratory activity, and the end-inspiratory pressure (P0ax) as the setting of the off-switch threshold, we considered two indices in the central and lung volume-related control of Ti: (a) P/P0max, an index of central inspiratory contribution to inspiratory off-switching, and (b) 1¿P/P0 max' an index of the additional vagal input needed to terminate inspiration. Both indices were found to be independent of PaCO2, varying solely as a function of time from the onset of inspiration. Changes in the relationship between tidal volume (VT) and Ti with variation in body temperature and unilateral vagotomy were attributed to separate effects on the 1¿P/P0max vs Ti and 1¿P/P0max vs VT relations, respectively. The rapid shallow breathing pattern observed with continuous negative pressure breathing has been explained on the basis of early activation of an inspiratory on-switch mechanism by lung deflation receptors. View full abstract»

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  • On Modeling the Single Motor Unit Action Potential

    Page(s): 236 - 243
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    A model has been proposed for the generation of single motor unit potentials routinely observed in the clinical EMG examination of the normal biceps brachii muscle. A dipole representation was chosen for the single fiber activity. The motor unit was constructed from a uniform random array of single fibers. Motor unit potentials generated by this array have been observed at various distances both inside and outside the array. The effects of single fiber dipole axial dispersions on the potentials observed at increasing distances from the array have also been investigated. Motor unit potentials generated by the model have been compared with existing data from multielectrode studies in the biceps brachii. View full abstract»

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  • Ultrasonic Blood Flow Spectral Analysis Using Coherent Optics

    Page(s): 243 - 249
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    It has been shown that ultrasonic Doppler signals can be obtained easily and transcutaneously from many blood vessels in both normal and atherosclerotic subjects. The Doppler spectrum changes with time, giving rise toa distnbution of frequencies whose envelope has a waveform that is characteristic of the vessel site and closely folows the events of the cardiac cycle. This makes it very useful in diagnosing lesions of the arterial system. The paper presents a coherent optical technique for displaying and analyzing a blood-flow-generated ultrasonic Doppler spectrum. The system is highly cost-effective and produces spectrograms on-line. Other advantages include a large, continuously variable bandwidth, an instantaneous display of velocity profile, and simultaneous display of temporal spectra. The system makes use of the Fourier transformation property of converging lens and its use of processing time signals. The spectrum obtained from the brachial artery of a normal subject compares favorably with the spectrograms obtained using electronic spectrum analyzers. View full abstract»

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  • An Impedance Camera for Spatially Specific Measurements of the Thorax

    Page(s): 250 - 254
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    We have designed and built an impedance camera to generate electrical impedance images of the thorax. Our instrument makes 100 spatially specific admittance measurements per frame at rates up to 32 frames per second. An on-line raster-scan display provides direct visualization while recording of data allows off-line quantitative analysis. We have found that some of the admittance measurements change 25% in humans with forced respiration. We discuss the principle of a mutually guarding electrode array and its limitations and present ideal instrument specifications and a working design. Continuing development may allow noninvasive measurement of localized ventilation and perfusion. View full abstract»

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  • Optimal System Design for an Implantable CW Doppler Ultrasonic Flowmeter

    Page(s): 255 - 264
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    A totally implantable telemetry system utilizing custom micropower monolithic integrated circuits has been developed to measure instantaneous pulsatile blood flow in the major arteries of animals. The device utilizes the Doppler effect at ultrasonic frequencies to achieve a flowmeter possessing small size and weight, low power consumption, inherent accuracy, and long-term stability. The integrated circuit electronics package occupies a volume of 3.8 cc and requires a power consumption of 10 mW from a single 135 volt mercury cell. The volume of the entire implantable flowmeter package is less than 36 cc. As a micro-miniature radio-telemetry system, the flow-meter can be totally implanted within the body, thereby eliminating the need for wires penetrating the skin, a serious problem with "back-pack" flowmeters due to danger of infection. The implantable flow-meter system provides a new and necessary tool for accurate quantitative measurements in the study of cardiovascular disease. It has been used in the study of transplanted heart rejection to monitor blood velocity in the major arteries of doB View full abstract»

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  • New Interference Sensing Demand Pacemaker Functions

    Page(s): 264 - 269
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    Demand cardiac pacemaker functions are under study that provide new methods to distinguish between cardiac activity and pulsatile electromagnetic interference (PEMI). All known forms of currently marketed ventricular inhibited demand pacemaker (VVI) functions can be inhibited by high level pulsatile electromagnetic interference. The recent introduction of shielded circuitry to protect against disruptive (inhibiting) EMI has reduced pacemaker sensitivity to interference. However, EMI received via the cardiac lead/electrode can still mimic cardiac activity. This mimicing occurs as a consequence of detection by defribrillator protection structures or by amplifier saturation from RF artifacts insufficiently suppressed by input QRS bandpass filters. The new functions under development employ a separate EMI detection receiver for controlling the pacemaker mode to minimize inhibition by PEMI. View full abstract»

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  • Limited Lead Selection for Estimation of Body Surface Potential Maps in Electrocardiography

    Page(s): 270 - 276
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    Body surface potential mapping has shown promise as a technique to improve the resolution and accuracy of diagnostic electrocardiography, but the cost and effort required to obtain maps have made wide spread use impractical. As a step toward a practical system, the problems of redundancy and uniqueness of electrocardiographic signal information contained in large numbers of leads were investigated. An algorithm for optimal selection of a limited number of leads was developed. Data obtained from 132 human subjects including some with normal electrocardiograms (ECG) as well as some with abnormal ECGs, were used in the study. Estimation of body surface potentials from limited leads was evaluated using three criteria, including rms error, mean correlation coefficient between limited lead and total lead maps, and error to signal power ratio. Using 30 leads the average rms error was 32 ¿V, average correlation coefficient was .983 and noise to signal power was 3.5% in the presence of 20 ¿V rms noise. Another finding was that optimal sites are not unique, i.e., different sets of optimal sites may be found which perform equally well. This result has practical implications for the design of lead systems for estimating maps on the critically ill and on patients undergoing stress tests. View full abstract»

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  • A Method for the Exposure of Miniature Swine to Vertical 60 Hz Electric Fields

    Page(s): 276 - 283
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    A Plexiglas enclosure was built to hold Hanford miniature swine for exposure to vertical 60 Hz, single-phase electric fields; water was provided through a grounded metal drinking nozzle. The field at the top of a pig's back was increased over the field in the empty enclosure by a factor of 7. A pig's impedance to ground, while standing on a grounded metal plate, was about 2-3 kohms. The average normalized short circuit current for four swine was 6.8 ¿A/(kV/m). All of the swine were able to drink with no evidence of shocks at the maximum attainable unperturbed field strength of 55 kV/m. The current between the grounded nozzle and the drinking pig was 1-3 ¿A/(kV/m). The threshold of perception of a mouth-to-nozzle current averaged 275 AA. Two swine exhibited ear flicking above 50 k/m, and visible hair motion was observed on the ear of one anesthetized pig at fields larger than 40 kV/m. A behavioral test suggested that swine were able to perceive fields greater than 30 kV/m. Photographic tests detected no corona discharge from an anesthetized pig or the test enclosure. View full abstract»

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  • Relationships Among Green's Theorem, Helmholtz' Theorem, and Integral Equation Methods of Solving the Forward EGG Problem

    Page(s): 283 - 287
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    Recent attempts to solve the forward problem of electrocardiography using approximation methods have proceeded from two distinct theoretical derivations, the Gelernter-Swihart procedure based on a Helmholtz Theorem approach and that of Barr et al. based on Green's Theorem. The Green's Theorem approach has not yet been satisfactorily placed on a physical basis, nor has it been interpreted in terms of what is acknowledged to be the most general formulation of time-invariant fields, Helmholtz's Theorem. View full abstract»

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  • Mammalian Auditory Responses to 3.0 GHz Microwave Pulses

    Page(s): 288 - 293
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    A study of the effects of 3.0 GHz microwave pulses on the auditory systems of a number of mammalian species was conducted. Some human subjects heard a distinct "click" when irradiated with a sufficiently intense individual microwave pulse. Microwave induced auditory evoked responses were measured in the cat, dog, and chinchilia. The microwave peak power density levels at the threshold of producing an auditory response were determined for a number of human subjects in addition to the smaller animals. The inability of some of the human subjects to bear short microwave pulses was correlated with hearing losses above 8 kHz in frequency. View full abstract»

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  • Some Observations on the Physical Realizability of Compartmental Models with Delays

    Page(s): 294 - 295
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    Often a compartmental model must include delays to fit the experimental observations. The resulting dynamical equations are difference-differential equations and must satisfy certain conditions if they represent a physically realizable system. The physical realizability of two compartmental models with delays is discussed. View full abstract»

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  • A Video System for Measuring the Blood Flow Velocity in Microvessels

    Page(s): 295 - 297
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    A video correlating system has been developed to measure the velocity of flowing blood in a microvessel. As the velocity of a red blood cell in a microvessel is given by the ratio of distance moved ¿L to the incremental time At, we fix At in our system according to the framing rate of the video system and employ the video signal to find ¿L by cross correlation. View full abstract»

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  • EEG Phasic Event Detection by Microcomputer

    Page(s): 297 - 299
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    This communication describes results of preliminary testing of a new method of implementing EEG waveform detection. The circuit described is capable of detecting EEG alpha, beta, delta, sleep spindles, muscle artifact, etc., on three separate channels simultaneously when operating at 32: 1 time compression. Microprocessor implementation allows for adaptive control of detection parameters, making hardware changes unnecessary. View full abstract»

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  • Slew Rates for Electrocardiographic Signals

    Page(s): 299 - 301
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    Frank lead electrocardiograms from 100 adults and 61 infants were recorded on magnetic tape and digitized at 2 ms intervals after bandwidth limiting fmst at 200 Hz and then at 100 Hz. Slew rates based on voltage differences between successive sampled values during QRS were computed for one cardiac cycle for each lead. Considered as a group, 200 ¿V/ms rates occur about 1% of the time in adult records, and 400 ¿V/ms rates occur about 1% of the time in infants' records. In extreme individual records, 300 ¿V/ms rates were exceeded 2% of the time in an adult record, and 400 ¿V/ms rates were exceeded 6.5% of the time in an infant's record. No significant differences in slew rates were observed to be caused by variation in bandwidth from 100 Hz to 200 Hz. It is recommended that ECG instruments be designed to be capable of faithfully reproducing at least 400 ¿V/ms slew rates. View full abstract»

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  • A Fluidic Drive System for Intra-Aortic Balloon Heart Assist Device

    Page(s): 301 - 303
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    Intra-aortic balloon pumping is a counter pulsation technique for temporary circulatory assistance in cardiogenic shock and other low cardiac output conditions. Conventional systems use a balloon at the end of a catheter driven by a solenoid valve, controlled by patient's ECG or ventricular pressure signal. This results in time delay introducted by solenoid spool inertia, gas inertia, and hysteresis effects of the solenoid. Fluidics, because of their non-moving part operation and high switching speeds, minimizes the inertial effects while contributing high reliability. This communication describes a fluidic system developed for driving the balloon accepting electric control signals. View full abstract»

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  • Electromagnetic Syringe

    Page(s): 303 - 304
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    A device is described which can be used as a "hyperdermic syringe" to inject electromagnetic energy into deep-lying tissues. View full abstract»

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  • A Method for Measuring Functional Residual Capacity in Neonates with Endotracheal Tubes

    Page(s): 304 - 307
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    This study evaluates a new 60-s closed circuit helium (He) dilution technique for determination of functional residual capacity (FRC) in intubated neonates independent of snall gas leaks present around uncuffed endotracheal (ET) tubes. By analyticaly relating the fall in He concentration due to mixing with that due to leakage it is possible to predict the final equflibration concentration of He and, therefore, correct for ET tube leaks. The system (120 ml) contains an air pump, He meter, breathing bag in cylinder, a strip chart readout, and solenoid value. Continuous positive airway pressure (CPAP) or ventilator pressure can be applied during testing. One hundred in vitro measurements of FRC ranging from 5-100 cc in both leak and nonleak models were performed and were accurate to within ±7.8% standard deviation. Functional residual capacity measurements were also performed in 30 infants (weight 600-4400 gm). View full abstract»

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  • A Sequential Stimulator for Electrical Restoration of the Micturition Reflex

    Page(s): 307 - 311
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    Numerous attempts at electrical stimulation of the detrusor muscle of the urinary bladder to evoke contraction and evacuation have been carried out over the past decade. Problems encountered include pain and increased urethral resistance due to current spread to the surrounding pelvic structures and the sphincter of the bladder. The development of a three-channel vesical stimulator to realize sequential pulsing is described. The inductively coupled device is externally controlled and totally implantable. The successful trial of the stimulator in an animal and the good current restricting properties of the system indicate a feasible method for the treatment and control of urinary retention following paraplegia View full abstract»

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  • A Pressure Regulator for Proportional Regulation of Two Gas Pressures

    Page(s): 311 - 313
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    A pressure regulator which maintains a constant ratio of pressures at two gas outlets is described. The device consists of three chambers, a central reference chamber; and two side chambers, each one separated from the central one by a double diaphragm. The two double diaphragms are connected to two valves that control the respective gas flows into the side chambers. In this way, the pressures in the side chambers are governed by the pressure in the central reference chamber. The individual diaphragms of one double diaphragm are of identical diameter; whereas, the other double diaphragm consists of two single diaphragms of different diameters. The areas of these diaphragms determine the constant ratio of the outlet pressures from the side chambers. View full abstract»

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  • Effect of Surface Cooling and Blood Flow on the Microwave Heating of Tissue

    Page(s): 313 - 316
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    The one-dimensional heat transport equation has been solved for a semi-infinite plane of tissue irradiated by microwave radiation, to determine the effects of thermal convection due to blood flow and transfer of heat from the tissue surface into space on the steady-state temperature distribution in the tissue. For microwaves in the 1 to 10-GHz range, the effective heating depth is 1 to 2 cm, and can be much deeper than the penetration depth of the radiation in the tissue. The position of the maximum tissue temperature can be varied by a centimeter or so by cooling the surface. The results suggest that microwave irradiation of simulated biomaterials is not likely to provide accurate estimates of the actual microwave-induced temperature distribution in tissue. View full abstract»

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  • Announcement

    Page(s): 317
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    Freely Available from IEEE

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