Showing papers in "IEEE Transactions on Biomedical Engineering in 1979"
TL;DR: The myoelectric signal is the electrical manifestation of the neuromuscular activation associated with a contracting muscle and the lack of a proper description of the ME signal is probably the greatest single factor which has hampered the development of electromyography (EMG) into a precise discipline.
Abstract: The myoelectric (ME) signal is the electrical manifestation of the neuromuscular activation associated with a contracting muscle. It is an exceedingly complicated signal which is affected by the anatomical and physiological properties of muscles, the control scheme of the peripheral nervous system, as well as the characteristics of the instrumentation that is used to detect and observe it. Most of the relationships between the ME signal and the properties of a contracting muscle which are presently employed have evolved serendipitously. The lack of a proper description of the ME signal is probably the greatest single factor which has hampered the development of electromyography (EMG) into a precise discipline.
631 citations
TL;DR: Flat photoetched gold conductors, situated on a glass plate and deinsulated at their tips with single 8 ns UV laser pulses, have been utilized to record single unit extra-cellular activity from brain ganglia of the snail Helix pomatia.
Abstract: Flat photoetched gold conductors 12 ?m wide and 2 ?m thick, situated on a glass plate and deinsulated at their tips with single 8 ns UV laser pulses, have been utilized to record single unit extra-cellular activity from brain ganglia of the snail Helix pomatia. A fixed array of 36 such conductors, terminating in six rows and six columns in a 0.5 mm x 1 mm area, is capable of monitoring simultaneous single unit activity from numerous neurons. Spike amplitudes of 300?500 ?V are generally observed from the predominant 40 ?m diameter cells of these ganglia. Giant neurons usually produce signal amplitudes of over 3 mV that are simultaneously seen by many electrodes. Signals can be monitored by merely resting a locally desheathed ganglion on the recording area under its own weight in a shallow pool of Ringer. A 10 ?m diameter crater in a 3?4 ?m thick insulation layer has an impedance of 2?4 M?at 1 kHz. The capacitance of this metal electrolyte interface is about 0.5 pF/?m2, suggesting that the UV laser produces a partially colloidal gold surface. With this recessed tip design, simultaneous single unit recording from small neurons appears ensured if electrode impedances are below 4 M?, shunt impedances are above 30 M?, and glia cells are not allowed to reinsulate the end of the gold conductor.
332 citations
TL;DR: A method is presented to decide the order a polynomial or Fourier series best represents a set of biomechanical data points, with regard to the calculation of the first and second derivatives of the data.
Abstract: A method is presented to decide the order a polynomial or Fourier series best represents a set of biomechanical data points, with regard to the calculation of the first and second derivatives of the data.
268 citations
TL;DR: A three-dimensional diffuse reflectance equation for a two-layer tissue model was developed using photon diffusion theory to investigate the effects of various tissue and system parameters on the partial reflectance from the second tissue layer.
Abstract: A three-dimensional diffuse reflectance equation for a two-layer tissue model was developed using photon diffusion theory. In this model, tissue was considered to consist of two homogeneous isotropically scattering layers whose scattering and absorption constants were expressed as a linear sum of those of whole blood and a blood-free tissue component; tissue hemoglobin content and oxygen saturation were then expressed in terms of these total tissue parameters. Reflectance predictions given by the two-layer equation were used to investigate the effects of various tissue and system parameters on the partial reflectance from the second tissue layer; among such parameters significantly affecting deep-layer reflectance are the tissues scattering constants, its geometry, and the geometry of the optical transducer. When the penetration depth of the incident photons is small compared with the thickness of the first layer, reflectance contributions from the second layer are negligible, and a single-layer approximation would be adequate; resultant reflectance errors range from 6 to 8 percent of the total reflectance, for source-detector separations in the range from 1 to 4 mm. However, when the photon penetration depth is large with respect to first-layer thickness, the effects of deep layers are both important and strongly dependent on transducer geometry; partial reflectances range to 50 percent of the total when the source-detector separation is 4 mm.
263 citations
TL;DR: In this article, a five-step digital filter was developed which removes components other than those of QRS complex from the recorded electrocardiogram (ECG), and the final step of the filter produces a square wave whose on-intervals correspond to the segments with QRS complexes in the original wave.
Abstract: The five step digital filter has been developed which removes components other than those of QRS complex from the recorded electrocardiogram (ECG). The final step of the filter produces a square wave whose on-intervals correspond to the segments with QRS complexes in the original wave.
205 citations
TL;DR: In this article, the role of internal geometry and inhomogeneities in the "forward problem" of electrocardiography (ECG) was studied. And the integrated effect of the inhomalogeneities on the surface potential distribution was investigated.
Abstract: To study the role of internal geometry and inhomogeneities in the "forward problem" of electrocardiography (ECG), a mathematical model was constructed which permitted manipulation of these variables. The model, which consists of two eccentric systems of concentric spheres, contains all the important torso compartments, namely the blood cavity, the myocardium, the pericardium, the lung region, the surface muscle layer, and the subcutaneous fat. An analytic solution is found in the form of a double series expansion in Legendre polynomials. The integrated effect of the inhomogeneities on the surface potential distribution is investigated. The model demonstrates the importance of interactions between the various torso components in determining the potential distribution at the surface.
127 citations
TL;DR: A new approach to the measurement of muscle fiber conduction velocity by surface electromyography (EMG) is developed, based upon a triple surface-electrode configuration, which is equally suited to a 16-bit microprocessor, without any need for hardware multiplication or floating-point facilities.
Abstract: A new approach to the measurement of muscle fiber conduction velocity by surface electromyography (EMG) is developed, based upon a triple surface-electrode configuration. Unlike previously reported methods, it does not require the Fourier transformation of raw EMG data, and can be implemented on-line on a simple digital computer. Although programmed here on a PDP-11 machine, the algorithms developed are equally suited to a 16-bit microprocessor, without any need for hardware multiplication or floating-point facilities. Accurate conduction velocity estimates may be obtained every few seconds.
110 citations
TL;DR: In a sample of 220 Frank4ead ECG's the removal of signal redundancy by second-order prediction or interpolation with subsequent entropy encoding of the respective residual errors was investigated, finding interpolation provided a 6 dB smaller residual error variance than prediction.
Abstract: Compression of digital electrocardiogram (ECG) signals is desirable for two reasons: economic use of storage space for data bases and reduction of the data transmission rate for compatibility with telephone lines. In a sample of 220 Frank4ead ECG's the removal of signal redundancy by second-order prediction or interpolation with subsequent entropy encoding of the respective residual errors was investigated. At the sampling rate of 200 Hz, interpolation provided a 6 dB smaller residual error variance than prediction. A near-optimal value for the interpolation coefficients is 0.5, permitting simple implementation of the algorithm and requiring a word length for arithmetic processing of only 2 bits in extent of the signal precision. For linear prediction, the effects of occasional transmission errors decay exponentially, whereas for interpolation they do not, necessitating error control in certain applications. Encoding of the interpolation errors by a Huffman code truncated to ±5 quantization levels of 30 ?V, required an average word length of 2.21 bits/sample (upper 96 percentile 3 bits/sample), resulting in data transmission rates of 1327 bits/s (1800 bits/s) for three simultaneous leads sampled at the rate of 200 Hz. Thus, compared with the original signal of 8 bit samples at 500 Hz, the average compression is 9:1. Encoding of the prediction errors required an average wordlength of 2.67 bits/sample with a 96 percentile of 5.5 bits/sample, making this method less suitable for synchronous transmission.
106 citations
TL;DR: From dog aorta investigations, it is concluded that the orientation effect on impedance plethysmography pulse waveforms nearly equals that of blood vessel diameter change, and that waveform analysis must consider both effects.
Abstract: Erythrocyte orientation, deformation, and axial accumulation cause differences in resistance between flowing and resting blood. Through theoretical calculations and experimental measurements, we studied the effects of these factors and of sinusoidal and pulsatile flow on blood resistivity. The effect of axial accumulation is least significant. Frequency characteristics of blood resistance under sinusoidal and pulsatile flow showed that erythrocytes cannot orient in response to rapid flow changes of a few pulses per second. From dog aorta investigations, we conclude that the orientation effect on impedance plethysmography pulse waveforms nearly equals that of blood vessel diameter change, and that waveform analysis must consider both effects.
97 citations
TL;DR: In this paper, the distribution of conduction velocities within the alpha fiber group of an in situ human peripheral nerve trunk was determined based on the analysis of the shape of compound nerve action potentials recorded from surface electrodes.
Abstract: A technique is described which enables the distribution of conduction velocities within the alpha fiber group of an in situ human peripheral nerve trunk to be determined. The technique is based on the analysis of the shape of compound nerve action potentials recorded from surface electrodes and is non-invasive. Velocity distributions calculated for a group of normal adults are presented and represent the first known measurements of this parameter.
94 citations
TL;DR: Brightness measures, gray-level statistics, and a compactness measure are applied in a decision tree to characterize the candidate objects and a verification technique was evaluated to differentiate between significant groups of microcalcifications and isolated objects as well as false alarms.
Abstract: We have considered the problem of computerized picture processing of mammographic images for the early detection of breast cancer by determination of the very significant microcalcifications. Brightness measures, gray-level statistics, and a compactness measure are applied in a decision tree to characterize the candidate objects. A verification technique was evaluated to differentiate between significant groups of microcalcifications and isolated objects as well as false alarms. Feasibility of the microcalcification detection algorithm was demonstrated in experiments using 132 mammogram subareas, each consisting of 512 ×512 picture elements.
TL;DR: Overall, the field of computerized clinical EEG is now a relatively rapidly evolving one in which further progress is likely to be accelerated by the utilization of microprocessors and high-speed arithmetic processing devices.
Abstract: Recent developments in the field of computerized clinical electroencephalography (EEG) are surveyed, with particular reference to techniques of analysis of background (stationary) EEG activity, transient (nonstationary) activity, and to integrated systems for multichannel clinical EEG's. A variety of approaches have been used for the basic EEG analyses. For background activity, the fast Fourier transform (FFT) and autoregressive approaches have predominated. For fast transients, segmentation, double differentiation, and inverse filtering have been prevalent. Some integrated systems, which provide a summary, and in some cases an evaluation of the basic EEG analyses, are limited to processing of only the background activity, whereas others include both background and transient activity. Some systems have been designed primarily to be an aid to the clinical electroencephalographer in the preparation of his report. A very few systems have been designed to provide a printed report similar to the conventional clinical EEG report. Although not considered extensively in this review, artifact rejection and/or compensation will necessarily be a major aspect of any fully computerized system. Overall, the field of computerized clinical EEG is now a relatively rapidly evolving one in which further progress is likely to be accelerated by the utilization of microprocessors and high-speed arithmetic processing devices.
TL;DR: The methodical steps which led towards the construction of a six-channel electrical stimulator are given and a discussion of preliminary experience obtained by using the stimulator clinicaly is also presented and ideas for future work are given.
Abstract: Recent trends in the field of functional electrical stimulation (FES) of stroke patients are presented together with a short history of the development of the field. The methodical steps which led towards the construction of a six-channel electrical stimulator are given. The criteria for detennining the number of stimulation channels are highlighted and FES problems of stance phase active stimulation are discussed. The stimulator described is intended for FES assistance of a patient's gait. Stimulation is synchronized with the gait by means of a shoe-insole heel switch. A review of design principles and functions employed is presented in detail, together with a discussion emphasizing problems of multi-site FES in swing and stance phases during locomotion. A discussion of preliminary experience obtained by using the stimulator clinicaly is also presented and ideas for future work are given.
TL;DR: The differential temperature rise in a spherical region stimulating a potential hot spot in the central region of a human head has been determined, taking into account heat conduction as well as heat convection due to blood flow.
Abstract: The differential temperature rise in a spherical region stimulating a potential hot spot in the central region of a human head has been determined, takdng into account heat conduction as well as heat convection due to blood flow. The results apply in general to ali cases where the dimensions of the model and the frequency of the incident electromagnetic wave is such that a hot spot is formed near the central region. For a heat deposition rate of 10 mW/g in a hot spot of 1 cm radius, a differential temperature rise over the ambient tissues and blood is approximately 0.5°C. This corresponds to the case of a differential absorption cross section of 1 cm-1 for a 5 cm radius sphere exposed to an incident power density of 10 mW/cm2. For larger models of man's head the differential temperature rise is smaller.
TL;DR: A syntactic method for analysing ECG waveforms considered as a multichannel process and a procedure is designed in order to extract the time evolution of the rhythm using the energy of the ECG derivatives.
Abstract: A syntactic method for analysing ECG waveforms considered as a multichannel process is presented. A procedure is designed in order to extract the time evolution of the rhythm using the energy of the ECG derivatives.
TL;DR: A mathematical model for the mucociliary clearance of inhaled particles in the normal human lung is reported, which assumes Weibel's symmetric dichotomously branching system of airways in the lung.
Abstract: We report the development of a mathematical model for the mucociliary clearance of inhaled particles in the normal human lung The model assumes Weibel's symmetric dichotomously branching system of airways in the lung The model is formulated by assuming that the particles residing on the surface of the mucus blanket behave as a fluid and that their concentration is governed by the continuity equation The concentration of particles in each airway generation of the lung is found to depend on the initial deposition pattern and the transport rate of mucus in each airway generation The distribution of particles is determined by a model calculation which takes into account inertial impaction, gravitational sedimentation, and Brownian diffusion as the principal mechanisms of particle deposition The mucus transport rates are found by first assuming that the mucus blanket which lines the airways is uniformly thick throughout the entire lung and that there is no net absorption or secretion of mucus in a given airway generation The only mucociliary transport rate which has been well measured experimentally is in the trachea We adjust the trachael transport rate in the model until a good agreement between predicted and observed clearance of 79?aerodynamic diameter particles from the lung is obtained The tracheal transport rate necessary to achieve a good fit is 55 mm/min which agrees with measured values With an established trachael transport rate we are then able to calculate transport rates in distal airways
TL;DR: The influence of the stimulus parameters on tissue heating was evaluated by the use of a passive model described in the literature, and the desire for a stimulus that was independent of skin resistance resulted in the investigation of biphasic current waveforms.
Abstract: The large number of investigations involving the use of electrocutaneous nerve stimulation as a surrogate sensory channel, and for relief of acute and chronic pain, have raised questions about the effect of the stimulus parameters on both nerve excitation and passive tissue heating. The short and long term influence of the stimulus parameters upon nerve stimulation has formerly been described on the basis of clinical studies. The approach taken here was to examine the effects of stimulus parameters using models. For myelinated nerve the Frankenhaeuser-Huxley model of Xenopus Laevis was used. The influence of the stimulus parameters on tissue heating was evaluated by the use of a passive model described in the literature. Consideration of electrolytic effects led to the selection of a stimulus with zero net charge flow. The desire for a stimulus that was independent of skin resistance resulted in the investigation of biphasic current waveforms.
TL;DR: A new scheme is proposed for the detection of premature ventricular beats, which is a vital function in rhythm monitoring of cardiac patients, and results of application to ECG of two arrhythmia patients are presented.
Abstract: A new scheme is proposed for the detection of premature ventricular beats, which is a vital function in rhythm monitoring of cardiac patients. A transformation based on the first difference of the digitized electrocardiogram (ECG) signal is developed for the detection and delineation of QRS complexes. The method for classifying the abnormal complexes from the normal ones is based on the concepts of minimum phase and signal length. The parameters of a linear discriminant function obtained from a training feature vector set are used to classify the complexes. Results of application of the scheme to ECG of two arrhythmia patients are presented.
TL;DR: A multilayer model for the photoacoustic effect was developed to account for the nonuniform thermal properties of the intact skin arising from the water concentration gradient, and the width of the barrier region was found to correspond to that of the outermost layer of the epidermis, the stratum corneum.
Abstract: The technique of photoacoustic spectroscopy (PAS) was applied in two areas of dermatology research: 1) drug detection and drug diffusion rates in skin, and 2) thermal properties and water content of skin. The drug studies involved detection of the drug tetracycline in the skin and determination of the diffusion rate of the drug through the skin. The water content studies involved determining the thermal properties of the epidermis as a function of water content and the effect of the water concentration gradient across the epidermis. A multilayer model for the photoacoustic effect was developed to account for the nonuniform thermal properties of the intact skin arising from the water concentration gradient. This model was used to determine the width of the region comprising the diffusional barrier in skin. The width of the barrier region was found to correspond to that of the outermost layer of the epidermis, the stratum corneum. This finding coincides with previous research indicating that the stratum corneum comprises the primary barrier to the diffusion of water through the epidermis.
TL;DR: Homomorphic analysis and pole-zero modeling of electrocardiogram (ECG) signals are presented and the pole- zero pattern of the models can give a clue to classify the normal and abnormal signals.
Abstract: Homomorphic analysis and pole-zero modeling of electrocardiogram (ECG) signals are presented in this paper. Four typical ECG signals are considered and deconvolved into their minimum and maximum phase components through cepstral filtering, with a view to study the possibility of more efficient feature selection from the component signals for diagnostic purposes. The complex cepstra of the signals are linearly filtered to extract the basic wavelet and the excitation function. The ECG signals are, in general, mixed phase and hence, exponential weighting is done to aid deconvolution of the signals. The basic wavelet for normal ECG approximates the action potential of the muscle fiber of the heart and the excitation function corresponds to the excitation pattern of the heart muscles during a cardiac cycle. The ECG signals and their components are pole-zero modeled and the pole-zero pattern of the models can give a clue to classify the normal and abnormal signals. Besides, storing only the parameters of the model can result in a data reduction of more than 3:1 for normal signals sampled at a moderate 128 samples/s.
TL;DR: The relative effectiveness of the various possible linear configurations of four electrodes in terms of spatial resolution is discussed, including the accuracy of computed spatial resolution with respect to corresponding experimental ones.
Abstract: The in vivo measurement of specific impedance in brain tissue involves several technical aspects. The most stringent difficulties relate to electrode polarization and spatial resolution of the measuring system. The polarization is solved by usinga four electrode arrangement with a very high impedance preamplifier on the potential electrodes. This paper discusses the relative effectiveness of the various possible linear configurations of four electrodes in terms of spatial resolution. The accuracy of computed spatial resolution with respect to corresponding experimental ones is specified.
TL;DR: The results of a search for low electrical impedance in the areas of acupuncture points show that probing in the immediate area of charted acupuncture points can destroy the integrity of the stratum corneum layer, resulting in the lowered impedance sought for.
Abstract: This communications presents the results of a search for low electrical impedance in the areas of acupuncture points. The method involved placing a search grid on areas of the skin and measuring the impedance in random order using several replications. The data does not support the location of acupuncture points by electrical impedance. In addition, it shows that the stratum corneum layer of the epidermis contributes to most of the impedance and that it is easily broken, resulting in dramatically lowered skdn impedance. This leads to the conclusion that probing in the immediate area of charted acupuncture points can destroy the integrity of the stratum corneum layer, resulting in the lowered impedance sought for.
TL;DR: Potentials within and on the surface of a finite cylindrical volume conductor due to a single active nerve fiber along its center have been calculated by solving Laplace's equation using a relaxation model.
Abstract: Potentials within and on the surface of a finite cylindrical volume conductor due to a single active nerve fiber along its center have been calculated by solving Laplace's equation using a relaxation model. The results have enabled the variation of the potential that would be recorded from a surface electrode to be estimated for differing nerve depths and conduction velocities.
TL;DR: A multielectrode probe structure is described in which several thin-film metal electrodes are defined on the outer surface of a glass micropipette using electron-beam lithography, resulting in electrode recording characteristics which are extremely well matched.
Abstract: A multielectrode probe structure is described in which several thin-film metal electrodes are defined on the outer surface of a glass micropipette using electron-beam lithography. Electrode geometries are controlled to within one micron, resulting in electrode recording characteristics which are extremely well matched. Recording sites are 5 , um wide rings spaced 100 , um apart in depth. Analysis and characterization show the structure to be capable of accurately recording tissue potentials with a minimum of tissue damage. Use of these probes in current source-density (CSD) analysis of extraceliular current flow is described.
TL;DR: A multilayered planar model is used to examine the dependence of whole-body power absorption on the configuration of surface layers, e.g., skin, fat, and muscle which normally occur in biological bodies and it is found that the layering resonance for three-dimensional bodies can be predicted quite accurately by a planar models.
Abstract: A multilayered planar model is used to examine the dependence of whole-body power absorption on the configuration of surface layers, e.g., skin, fat, and muscle which normally occur in biological bodies. It is found that the layering resonance for three-dimensional bodies (as opposed to the geometrical resonance) can be predicted quite accurately by a planar model. Calculations for a multilayered prolate spheroidal model of man predict a whole-body layering resonance at 1.8 GHz with a power absorption 34 percent greater than that predicted by a homogeneous model.
TL;DR: This paper describes initial experiments to determine the feasibility of recording functionally distinct neuroelectric signals from the surface of the rabbit's sciatic nerve.
Abstract: This paper describes initial experiments to determine the feasibility of recording functionally distinct neuroelectric signals from the surface of the rabbit's sciatic nerve. A cuff electrode assembly was constructed; it consisted of two planar arrays, each having four wires equally spaced around the circumference of the electrode. The electrode assembly was placed on the sciatic nerve proximal to the popliteal fossa. A hook electrode was placed on six branches of the sciatic nerve in turn, just proximal to each branch's insertion into a leg muscle. Stimulation of the nerve branches was used to evoke signals in the sciatic nerve.
TL;DR: Two different systems designed to extract sarcomere length and several other variables from the light diffraction pattern in muscle are described, each of which offers better convenience of operation and wider bandwidth.
Abstract: Two different systems designed to extract sarcomere length and several other variables from the light diffraction pattern in muscle are described. One system utilizes a linear photodiode array to detect the intensity distribution of diffracted light from muscle. This system provides computed outputs of sarcomere length, first order width, and time rate of sarcomere length change according to two different algorithms. Another system utlizes a Schottky photo-position sensor and provides sarcomere length and integrated first order intensity. The accuracy (within 1%) and resolution (2 nm) of both systems are comparable. The former system offers better convenience of operation while the latter offers wider bandwidth (2.5 kHz vs. 100 kHz).
TL;DR: A theoretical analysis of Doppler frequency estimators proposed to be used in ultrasonic moving target indicator measurements of velocity profiles in blood flow, finding that all estimators work fairly well for narrow-band Dopples, but errors are found when broad-band spectra are present.
Abstract: A theoretical analysis of Doppler frequency estimators proposed to be used in ultrasonic moving target indicator (MTI) measurements of velocity profiles in blood flow is given. The estimators give an output in the form of a single analog voltage and the relation of the output to the Doppler spectrum is discussed. Three new estimators are also proposed. All estimators work fairly well for narrow-band Doppler spectra, but errors are found when broad-band spectra are present.
TL;DR: Extracellular action potentials from 76 different muscle fibers in the human brachial biceps were recorded, with a 14 lead multielectrode, each leading-off surface being 25 ¿m in diameter.
Abstract: Extracellular action potentials from 76 different muscle fibers in the human brachial biceps were recorded, with a 14 lead multielectrode, each leading-off surface being 25 ?m in diameter. Volume conduction of these action potentials was calculated by representing the low-pass filter characteristics of the muscle tissue by a transfer function with one time constant and an attenuation factor. The radial decline of the action potentials was calculated in steps of 5 ?m, and the pickup radius of the electrode, defined as the distance at which the peak-to-peak amplitude of the action potentials declines to 200 ?V, was computed. The pickup radius for the 25 ?m diameter electrode, assuming an average action potential peak-to-peak amplitude of 6.2 mV was 292 Mm. With this uptake area, a fiber density in the brachial biceps of 1.37 fibers/uptake area (the average number of fibers belonging to one motor unit and included within the electrode uptake area) and a fiber radius of 28 ?m, the electrode "sees" 34 different motor units.
TL;DR: A method is developed for the measurement of the spatio-temporal receptive field (STRF) of neurons in the retina, an extension of existing white-noise identification techniques to include the spatial domain.
Abstract: A method is developed for the measurement of the spatio-temporal receptive field (STRF) of neurons in the retina. The test input is an unsteady visual pattern randomly modulated in both space and time, and the output is the stochastic time course of the intracellular response. The STRF is expressed in terms of the spatio-temporal Wiener kernels calculated through a special cross-correlation algorithm between the response and the stimulus-related information. The method is an extension of existing white-noise identification techniques to include the spatial domain. Consideration is given to the practical implementation of the required stimulus pattern, and has led to several alternative approaches.