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Showing papers in "IEEE Transactions on Biomedical Engineering in 1974"


Journal ArticleDOI
TL;DR: In this paper, it was shown that the description of thermal convection by blood is inconsistent in this equation, and that results are in error by the same order of magnitude as the convective energy transport itself.
Abstract: The widely used bio-heat transfer equation is examined regarding its term describing the thermal effects of blood perfusion. It is demonstrated, both by physical arguments and numerical results, that the description of thermal convection by blood is inconsistent in this equation, and that results are in error by the same order of magnitude as the convective energy transport itself.

241 citations


Journal ArticleDOI
TL;DR: This paper considers the quantitative description of intracellular and extracellular fields of a single circular cylindrical fiber resulting from the propagation of an action potential and a convolution integral formulation to field patterns is presented.
Abstract: This paper considers the quantitative description of intracellular and extracellular fields of a single circular cylindrical fiber resulting from the propagation of an action potential (AP). Several formulations are noted, but one, which permits identification of free-space source-sink relationships, is examined in some detail; the physical models which it gives rise to are described and developed. Desirable approximations are considered and the conditions of their validity are discussed. A convolution integral formulation to field patterns (from their sources) is presented. Axially symmetric anisotropic media are also considered.

211 citations


Journal ArticleDOI
TL;DR: In this article, an integrated liquidoxide-semiconductor FET structure is described, which is similar to a conventional n-channel depletion mode MOSFET except the gate metal is omitted.
Abstract: An integrated liquid-oxide-semiconductor FET structure is described. The structure is similar to a conventional n-channel depletion mode MOSFET except the gate metal is omitted. Immersing the device in a saline solution, the drain current is controlled by the potential between the source and the solution. Operated as an active recording electrode, the structure has several properties useful in neurological research.

211 citations


Journal ArticleDOI
TL;DR: It is concluded that superposition of images of both tissue and blood decreases the uncertainties inherent in the display of either image alone.
Abstract: Ultrasonic B-mode displays are produced by a new diagnostic scanner that yields dynamic Doppler information from blood flow in addition to both static and dynamic echo information from stationary and more slowly moving tissues. The effect is produced by combining the flow imaging capability of a multigate pulse-Doppler flow detector with a fast rotational pulse-echo B-mode scanner. The duplex system was designed for performing ultrasonic echo-Doppler arteriography where the location and geometry of the interface between occlusive atherosclerotic tissue and blood is of prime concern. Initial results on normal arteries in vivo are illustrated. Spatial alignment of echo and Doppler images is obtained by using the same transducer and scanning mechanism for both. However, clinical trials on patients with verified occlusive arterial disease indicated a two-transducer system would be more desirable. It is concluded that superposition of images of both tissue and blood decreases the uncertainties inherent in the display of either image alone.

201 citations


Journal ArticleDOI
TL;DR: The hypothetical biped possesses one rotational degree of freedom and two translational degrees, leading to a sixth-order system of nonlinear differential equations that is linearized and feedback control laws derived to produce the desired stable forward motion.
Abstract: While biped locomotion involves very complicated dynamical processes, a good deal can be learned about stability and feedback control from an analysis of simplified mathematical models. This paper treats locomotion dynamics relative to planar motion under an assumption that leg mass can be ignored in comparison to body mass. Thus the hypothetical biped possesses one rotational degree of freedom and two translational degrees, leading to a sixth-order system of nonlinear differential equations. These equations are linearized and feedback control laws are then derived to produce the desired stable forward motion. The feedback laws proposed involve a combination of continuous and discrete concepts to produce both step length and step period control as well as control of body attitude and altitude. The applicability of the control laws to the nonlinear system in the presence of large disturbances is verified by computer simulation. Hopefully, the results presented are significant relative to control processes arising in lower extremity prostheses and orthoses as well as to the design of biped robots.

195 citations


Journal ArticleDOI
TL;DR: The remote oculometer is a new instrument for the remote measurement of eye direction and pupil diameter, located several feet from the subject, who is free to move the eye being sensed throughout 1 ft 3 of space.
Abstract: The remote oculometer is a new instrument for the remote measurement of eye direction and pupil diameter. The electrooptical sensor unit is located several feet from the subject, who is free to move the eye being sensed throughout 1 ft 3 of space. The video processing is performed in real time by a standard minicomputer. The oculometer processor (minicomputer) provides automatic calibration and linearization to each subject and can, supply the output eye-direction information in the form of either fixation-point coordinates on any specified fixation plane, azimuth and elevation, or direction cosines.The oculometer measures line-of-sight to an accuracy of 1° for eye rotation angles, relative to the sensor unit, of from 0° to + 30° elevation and from -30 ° to + 30 ° azimuth.

186 citations


Journal ArticleDOI
TL;DR: A general model for the Doppler flowmeter based upon stochastic considerations of the scattering of ultrasound by blood is introduced, which characterizes the back- scattered ultrasound as a Gaussian random process and the expression for the autocovariance function is derived.
Abstract: The widespread application of ultrasonic techniques for the measurement of pulsatile blood flow has been hampered by the lack of a detailed theoretical understanding of the Doppler ultrasonic flowmeter. A general model for the Doppler flowmeter based upon stochastic considerations of the scattering of ultrasound by blood is introduced in this paper. The model characterizes the back- scattered ultrasound as a Gaussian random process and the expression for the autocovariance function is derived. For the CW Doppler flowmeter, the power spectral density function is computed, and its significance is emphasized: measurement of blood flow velocity corresponds to estimation of the average frequency of the Doppler power spectrum.

158 citations


Journal ArticleDOI
TL;DR: The Wiener theory of nonlinear system identification is extended to multi-input-output systems and experimentally applied and it is shown that the method is well suited for the treatment of the idiosyncratic features of such systems: nonlinearities, short lifetimes of experimental preparations, and high noise content.
Abstract: The Wiener theory of nonlinear system identification is extended to multi-input-output systems and experimentally applied. The experimental applicability of the method is discussed with regard to biological systems. It is shown that the method is well suited for the treatment of the idiosyncratic features of such systems: nonlinearities, short lifetimes of experimental preparations, and high noise content. A preliminary analysis is outlined, taking into account the characteristics of the system under study, which results in the determination of the parameters of the identifying experiment. An error analysis is made which can be used to increase the accuracy of the derived model within certain constraints. Several examples are given of the experimental application of the method to certain neural networks in a vertebrate retina (the catfish, Ictalurus punctatus, retina was used for these experiments). In addition to functional identification through white-noise stimulation, these same retinal neurons are identified morphologically through intracellular dye injection. The performance of the derived functional models, as compared to the physical system, is evaluated through a variety of tests and it is found to be very satisfactory.

114 citations


Journal ArticleDOI
TL;DR: In this paper, the distribution of power in the alpha rhythm over frequency and spatial wavelength is measured in several subjects by means of spatial-temporal Fourier analyses of scalp surface potentials using multichannel recordings from electrodes placed along the midline.
Abstract: Apparent similarities between brain waves and physical waves are considered. The distribution of power in the alpha rhythm over frequency and spatial wavelength is measured in several subjects. This is accomplished by means of spatial-temporal Fourier analyses of scalp surface potentials using multichannel recordings from electrodes placed along the midline. It is found that the spectrum of midline alpha oscillations peaks for long wavelengths (?20 cm). A dispersion relation relating frequency to spatial wavelength apparently exists for frequencies near the peak alpha frequency. That is, in all 13 records, frequency components just above the peak alpha frequency have shorter midline wavelengths than low alpha frequency components. The relationship of these results to theoretical descriptions of the EEG and to other experiments is discussed.

93 citations


Journal ArticleDOI
TL;DR: A miniaturized radio telemetry device has been developed which can monitor the magnitude and distribution of pressure generated between the cartilage-covered surface of the human hip socket and the surface of a hip prosthesis which replaces the spherical head of the femur in the hip.
Abstract: A miniaturized radio telemetry device has been developed which can monitor the magnitude and distribution of pressure generated between the cartilage-covered surface of the human hip socket and the surface of a hip prosthesis which replaces the spherical head of the femur in the hip. The pressure distribution is sensed by an array of 14 pressure transducers mounted inside the hollow ball of the prosthesis, and the signals from the transducers are transmitted to external receiving and recording equipment by a radio telemetry device also located inside the hollow ball.

84 citations


Journal ArticleDOI
TL;DR: In this paper, the authors examined the absorption of microwaves by the human skull by making computerized calculations of theoretical models of the skull and compared the calculated relative absorption versus frequency for homogeneous and inhomogeneous skull models.
Abstract: Resonance absorption of microwaves by the human skull is examined by making computerized calculations of theoretical models of the skull. The calculated relative absorption versus frequency is plotted and compared for homogeneous and inhomogeneous skull models. At a frequency of maximum power absorption, the spatial distribution of intracranial field intensity (based upon the theoretical model) is also calculated and plotted.

Journal ArticleDOI
TL;DR: In this article, an approximate 90-min biorhythm in resting human heart rate was assessed and described using the techniques of periodogram analysis and complex demodulation, and it was found that the amplitude of the 90-minute ultradian rhythm was modulated by a circadian (24-h) rhythm.
Abstract: Since the discovery of an approximate 90-min oscillation in rapid eye movement (REM) or dream sleep, much interest has been expressed in the physiological and behavioral parameters associated with this phenomenon. One of the often stated theories is that this 90-min rhythm is an endogenous biorhythm present throughout the 24-h day, perhaps representing a rest-activity cycle of the nervous system. An approximate 90-min biorhythm in resting human heart rate is assessed and described using the techniques of periodogram analysis and complex demodulation. The techniques employed found evidence for this rhythm in all subjects; in-addition, the amplitude of the 90-min ultradian rhythm seemed to be modulated by a circadian (24-h) rhythm. However, the modulating circadian rhythm was not usually phase locked to the circadian rhythm fixed by the waking/sleeping cycle of each subject.

Journal ArticleDOI
John Smith1
TL;DR: A digital computer is used to perform a detailed analysis of abnormal spikes to obtain quantitative values for spike characteristics and to determine the parameter values to be used in a special-purpose spike detector.
Abstract: A method for detecting spikes in the EEG is described. A digital computer is used to perform a detailed analysis of abnormal spikes to obtain quantitative values for spike characteristics and to determine the parameter values to be used in a special-purpose spike detector. This detector is described together with application results.

Journal ArticleDOI
TL;DR: Experimental results show that the static and dynamic properties of regulated movements are not essentially inferior to the properties of voluntary movements.
Abstract: We report about the results on positioning of the ankle joint of a hemiplegic patient and of normal experimental subjects, using functional electrical stimulation (FES) of antagonistic muscle groups and position feedback. Such a controller is intended to be used as the execution level of a multilevel orthotic system. The synthesis of the controller has been made with the aid of the components of an analog hybrid computer. Experimental results show that the static and dynamic properties of regulated movements are not essentially inferior to the properties of voluntary movements. There are stated technological problems that will have to be solved before the controller can be clinically applied for rehabilitation purposes. At the present state of the art, the poor technology of FES, the unsolved problem of fatigue with FES muscles, size, price, and bad cosmetic effect prevent the position controller from being clinically applicable.

Journal ArticleDOI
TL;DR: Electrical stimulation applied to the skin has been observed to relieve pain and certain constraints must be met, particularly in electrode design, in order to maximize effectiveness.
Abstract: Electrical stimulation applied to the skin has been observed to relieve pain. Although transcutaneous nerve stimulation devices are quite simple, certain constraints must be met, particularly in electrode design, in order to maximize effectiveness.

Journal ArticleDOI
TL;DR: A general class of nonlinear electromyographic (EMG) processors has been evaluated for their signal-to-noise ratio (SNR) properties and versions in which the smoothing filter is followed by an element with the inverse detector characteristics were also evaluated.
Abstract: A general class of nonlinear electromyographic (EMG) processors has been evaluated for their signal-to-noise ratio (SNR) properties. These filters incorporate as the detector element either a power-law (x n ) or root-law (x 1/n ) transformation (detector) followed by a linear low-pass smoothing filter. ``Linearized'' versions of these processors in which the smoothing filter is followed by an element with the inverse detector characteristics were also evaluated.

Journal ArticleDOI
TL;DR: In this article, the authors show that iridium, rhodium, platinum and palladium are extremely resistant to electrolysis under these conditions and electrolysis made of such materials should have lifetimes on the order of decades.
Abstract: Electrolysis measurements have been made on electrodes of platinum, stainless steel, tungsten, iridium, palladium, rhodium, rhenium, gold, tantalum, titanium, zirconium, and some conducting oxides of the tungsten bronze family. Electrodes were immersed in physiologic saline solution and subjected to biphasic rectangular current pulses of various current densities at 50 pps, 24 hours per day for periods up to nine months. Weight loss was recorded at intervals during this time. We conclude that iridium,rhodium, platinum and palladium are extremely resistant to electrolysis under these conditions and electrolysis under 5? thick, made of such materials should have lifetimes on the order of decades. Gold is somewhat poorer but probably acceptable; all the other materials tested, including tungsten and stainless steel, are unacceptable as chronic microelectrode materials.

Journal ArticleDOI
TL;DR: A three-sphere model is used to investigate the effects of inhomogeneities introduced by the scalp and the skull on the apparent location and magnitude of a current dipole representing local activity in the brain.
Abstract: A three-sphere model is used to investigate the effects of inhomogeneities introduced by the scalp and the skull on the apparent location and magnitude of a current dipole representing local activity in the brain. The magnitude of the dipole is found to decrease by a proportion of 40 percent, whereas the location of the dipole appears 35 percent more centric.

Journal ArticleDOI
TL;DR: In this article, an analytical approach to obtain the relative heating pattern due to the propagation of ultrasonic waves in a fat-muscle-bone layered tissue system is presented, and the contribution to heating due to mode conversion at the bone surface is also discussed.
Abstract: An analytical approach to obtain the relative heating pattern due to the propagation of ultrasonic waves in a fat-muscle-bone layered tissue system is presented. The effects on the relative heating pattern due to the change of incident angle and the change of frequency are discussed in this paper. The contribution to heating due to mode conversion at the bone surface is also discussed.

Journal ArticleDOI
TL;DR: A practical method for analyzing the biological effects of nontherapeutic ultrasound was applied to the data of 21 different principal investigators and suggested that exposures of minimal hazard lie below a log/log line connecting 100 ?
Abstract: A practical method for analyzing the biological effects of nontherapeutic ultrasound was applied to the data of 21 different principal investigators. The data were compiled so that individual investigators could develop tentative guidelines of their own regarding the hazards of diagnostic ultrasound in human beings. One set of guidelines developed suggested that exposures of minimal hazard lie below a log/log line connecting 100 ?s of 100 W/cm 2 ultrasound with 200 s of 100 mW/cm 2 ultrasound. An ultrasonic intensity of 100 mW/cm 2 or less was of little or no hazard for at least 10 000 s. These guidelines applied to both continuous- and pulsed-wave ultrasound doses that were described by average intensity multiplied by total exposure time. The proposed schedule was valid for 0.5-15 MHz and for all anatomic sites except the eyes.

Journal ArticleDOI
TL;DR: The time course of the cell-size distribution of labeled cells under flash labeling is investigated by computer simulation and favorably evaluated with the experimental results obtained for spontaneous AKR leukemia-cell population.
Abstract: The dynamics of cell cycle and proliferating kinetics are characterized by the state equations, which are linear difference matrix equations with their state vectors consisting of variables representing cells in a particular compartment for cell-age, cell-size, and cell-DNA content. The transformation required from the cell-age distribution to the cell-size and DNA distributions in this discrete-time model under various assumptions is derived. The asymptotic behavior (as the time approaches infinity) of the cell age, cell size, and cell DNA is studied. The time course of the cell-size distribution of labeled cells under flash labeling is investigated by computer simulation and favorably evaluated with the experimental results obtained for spontaneous AKR leukemia-cell population.

Journal ArticleDOI
TL;DR: A nondestructive technique to continuously monitor diameter and blood flow at the same point along the descending thoracic aorta has been developed and helped to avoid measurement artifacts such as the inclusion of other arteries, veins, or moving structures.
Abstract: The authors are with the Applied Physiology Branch. Environmental Science Division. U.S. Air Force School of Aerospace Medicine, Brooks AFB, Tex. 78235. A nondestructive technique to continuously monitor diameter and blood flow at the same point along the descending thoracic aorta has been developed. A probe was passed down the esophagus to a level 1 to 2 cm distal to the aortic arch. On its distal end were Doppler-shift velocity-detecting and pulse-echo position- sensing crystals. The pulse-echo system was used not only to measure the diameter of the aorta, but also to aim all of the probe crystals directly across the axis of the aorta. Information supplied by this system aided in the identification of the aorta and helped to avoid measurement artifacts such as the inclusion of other arteries, veins, or moving structures.

Journal ArticleDOI
TL;DR: A differential equation is developed to represent the dynamics of afferent temporal dispersion and positive feedback in a neural population and implies that the particular properties of neurons in the population arise-from the topology of connections and not from the single neurons.
Abstract: The glomerular neurons are small cells in the olfactory bulb which form numerous synaptic connections with each other and with the output neurons of the bulb, the mitral-tufted cells. They form in the mass two anatomical feedback loops, one within the population, the other between the populations of glomerular and mitral-tufted cells. The poststimulus time (PST) histograms of single glomerular neurons on afferent electrical stimulation are monotonic, always with initial increase in induced pulse probability at varying latency of onset, implying that interactions are mutually excitatory. A differential equation is developed to represent the dynamics of afferent temporal dispersion and positive feedback in a neural population. The solutions of the equation are used to generate curves fitted to the PST histograms. The required numerical values for the coefficients are similar to those found for other bulbar neurons, which implies that the particular properties of neurons in the population arise-from the topology of connections and not from the single neurons.

Journal ArticleDOI
TL;DR: In this paper, the problem of filtering artifact from QRST complexes of ECG records has been approached by the use of a digital, time-varying filter, and the optimum form of this filter assuming uncorrelated, zero-mean, additive noise is presented and shown to be equivalent to estimating the coefficients of an intrinsic component expansion of the complex.
Abstract: The problem of filtering artifact from QRST complexes of ECG records has been approached by the use of a digital, time-varying filter The optimum form of this filter assuming uncorrelated, zero-mean, additive noise is presented and shown to be equivalent to estimating the coefficients of an intrinsic component expansion of the complex Results are reported showing that QRST complexes in limb leads of normals may be accurately represented by only eight terms of the intrinsic component expansion A suboptimum filter is presented and results reported which show that an order of magnitude reduction of the 005 to 100 Hz artifact energy in the filtered complex can be achieved

Journal ArticleDOI
TL;DR: The change in the electrical conductivity of blood observed in Couette and Poiseuille flow is discussed and the cell orientation distribution is used to calculate the change in conductivity with flow.
Abstract: The change in the electrical conductivity of blood observed in Couette and Poiseuille flow is discussed. Theoretical calculations considering the motion of red cells in Couette flow are presented. The red cells are considered as insulating ellipsoids in a conducting medium (plasma). The cell orientation distribution is used to calculate the change in conductivity with flow.

Journal ArticleDOI
TL;DR: The experiment suggests that the nuclear power source can be used to extend the working life of implanted medical instruments.
Abstract: In order to evaluate nuclear power sources for biomedical applications, a nuclear battery, Betacel, was used to power two telemetry transmitters designed with a very low power consumption. The transmitters were implanted in a dog to measure the voltage of the battery and the deep body temperature. Special care was given to the glass packaging to prevent possible damage from body fluids. The experiment ran continuously for a 6-month period before termination. At that time, the animal was sacrificed to examine the radiation damage of tissues in the vicinity of the transmitters as well as the effects on vital organs. No measurable abnormality was detected. The experiment suggests that the nuclear power source can be used to extend the working life of implanted medical instruments.

Journal ArticleDOI
TL;DR: The technology of producing cardiorespiratory synchrograms (CRSG), a sequence of VCG-ECG patterns highly reproducible and highly characteristic of the individual as his heart responds to normal respiratory influences, is discussed with a brief outline of their medical and research utility.
Abstract: Ordinary respiration produces surprisingly large and highly variable changes in the electrocardiogram of many subjects, healthy as well as diseased. By responding voluntarily to a visual signal developed by special but simple electronic circuitry, or by a small computer, the subject can ``breathe with the lights'' and thus pace his breathing to an exact submultiple of his own heart rate without requiring forced breathing or constant respiratory rate. The flexible stationarity introduced by this technique allows two goals to be approached. One is the ``epitome'' electrocardiogram, a sequence of VCG-ECG patterns highly reproducible and highly characteristic of the individual as his heart responds to normal respiratory influences. The other is a set of indices characterizing quantitatively the physiological dynamics of the cardiorespiratory interaction in the individual. This pattern, expressed as respiratory heart-rate modulation index and pattern dynamics indices, may contain important medical indicators of autonomic and cardiovascular systems response status. The technology of producing these cardiorespiratory synchrograms (CRSG) is discussed with a brief outline of their medical and research utility.

Journal ArticleDOI
TL;DR: Electroencephalographic data consisting of visual evoked responses monitored via an array of electrodes from humans and penicillin-induced focal epileptic discharge data recorded from rat neocortex are analyzed, and high-resolution vector velocity and, thus, direction and speed of propagating wavefronts can be estimated.
Abstract: Electroencephalographic (EEG) data consisting of visual evoked responses monitored via an array of electrodes from humans and penicillin-induced focal epileptic discharge data recorded from rat neocortex are analyzed. This procedure, previously applied to seismic array data, offers a method by which high-resolution vector velocity and, thus, direction and speed of propagating wavefronts can be estimated.

Journal ArticleDOI
TL;DR: Dynamic as well as static temperature measurements are now possible in biological tissue using thin-film Cu-Ni microthermocouples, which exhibit response times of less than a millisecond with thermal properties similar to tissue.
Abstract: Dynamic as well as static temperature measurements are now possible in biological tissue using thin-film Cu-Ni microthermocouples. These probes which use a quartz substrate exhibit response times of less than a millisecond with thermal properties similar to tissue. Their thermoelectric EMF of 21 , ?m V/°C is linearly dependent on temperature over the range normally encountered in biological measurements. Probe-tip diameters as small as 10 ?m are being fabricated.

Journal ArticleDOI
TL;DR: Results from eight animal experiments indicate that this formulation predicts stroke volume to about ten-percent (10-percent) error over successive beat-to-beat changes of severalfold during episodes of mechanically induced beats and during control, isoproterenol, and angiotensin administration.
Abstract: A formulation for determining stroke volume from arterial pressure is presented which differs from previous methods in both scope of application and theoretical basis. The formulation is specifically applicable in the presence of large successive beat-to-beat variations which occur with premature contractions and other arrhythmias. Its derivation is based upon Windkessel theory, as are most others, but special emphasis is placed upon analysis of diastolic pressure (when arterial dynamics most nearly approach characteristics assumed in Windkessel theory). The formulation contains no ad hoc parameters although mean peripheral vascular resistance must be known and redetermined when changes in resistance occur. Results from eight animal experiments are presented which indicate that this formulation predicts stroke volume to about ten-percent (10-percent) error over successive beat-to-beat changes of severalfold during episodes of mechanically induced beats and during control, isoproterenol, and angiotensin administration.