Showing papers in "IEEE Transactions on Biomedical Engineering in 1980"
TL;DR: The study shows that the Doppler signal is formed essentially by heterodyne mixing of light beams backscattered in static structures and moving red cells.
Abstract: An instrument for measurement of tissue blood flow based on the laser Doppler principle was evaluated using a fluid model. A unique and linear relationship between flowmeter response and flux of red cells was demonstrated with red cell velocities and volume fractions within the normal physiological range of the microcirculatory network of the skin. Different degrees of oxygenation proved to influence the Doppler signal only to a minor extent. The study also shows that the Doppler signal is formed essentially by heterodyne mixing of light beams backscattered in static structures and moving red cells.
1,141 citations
TL;DR: A new instrument for measurement of regional tissue blood flow based on the laser Doppler principle is reported and a differential detector technique is introduced that reduces common-mode noise to a negligible level, without influencing the blood flow related signal.
Abstract: A new instrument for measurement of regional tissue blood flow based on the laser Doppler principle is reported. The theoretical background of light beating spectroscopy is discussed and a detection technique which makes possible the suppression of the adverse effects of laser-mode interference and wide-band beam amplitude noise is described. Instead of using a single square-law photodetector a differential detector technique is introduced that reduces common-mode noise to a negligible level, without influencing the blood flow related signal. The new instrument has proved to be highly stable and sensitive. Continuous recordings of tissue blood flow can be performed in the laboratory as well as at the bedside.
638 citations
TL;DR: A novel technique for processing the electrical activity of muscle which uses multiple channels of myoelectric activity which encompasses and places in perspective almost all single-channel myoprocessor developments to date, as well as specifying the optimal multiple-channelMyoelectrics signal processor.
Abstract: This paper (Part I of II) describes the development of a novel technique for processing the electrical activity of muscle which uses multiple channels of myoelectric activity. A phenomenological mathematical model of myoelectric activity is formulated. From this model, a mathematical statement of the optimal myoelectric signal processor is derived, and some of its properties are investigated. This mathematical statement encompasses and places in perspective almost all single-channel myoprocessor developments to date, as well as specifying the optimal multiple-channel myoprocessor. An experimental demonstration of the efficacy of this processor is presented in a subsequent paper (Part II).
240 citations
TL;DR: The input¿output relationships for modulation of force by recruitment during intramuscular electrical stimulation were examined for cat sleus muscles and human finger and thumb muscles and the implications of the nonlinearities on the proportional control of orthoses employing electrically stimulated muscles are discussed.
Abstract: The input?output relationships for modulation of force by recruitment during intramuscular electrical stimulation were examined for cat sleus muscles and human finger and thumb muscles. Recruitment was modulated by varying either the pulsewidth or amplitude of a monophasic, rectangular, cathodal current pulse train. Force was a nonlinear function of either pulsewidth or amplitude, and the shape of the nonlinearity was the same regardless of which parameter was modulated. The charge per stimulus pulse was lowest if pulsewidth was modulated with a fixed, high amplitude stimulus. The shape of the nonlinear relationship between pulsewidth and force (recruitment characteristic) depended on stimulus amplitude, electrode location in the muscle and muscle length. In most applications the amplitude and location would be fixed, so force would be a two-dimensional nonlinear function of pulsewidth and muscle length. The results are discussed with respect to possible mechanisns of recruitment during intramuscular stimulation, and the implications of the nonlinearities on the proportional control of orthoses employing electrically stimulated muscles.
211 citations
TL;DR: An expression for the received signal in ultrasonic blood velocity measurements is given and the stochastic properties of the signal are discussed with reference to the information content about the velocity field of the blood.
Abstract: A theoretical treatment of the scattering of ultrasound from blood is given, assuming that the blood behaves essentially as a continuum. The scattering then arises from fluctuations in the mass density and compressibility of the blood, which is caused by a fluctuation in the red cell concentration. An expression for the received signal in ultrasonic blood velocity measurements is given. The stochastic properties of the signal are discussed with reference to the information content about the velocity field of the blood. Since the signal is Gaussian, all available information is contained in the power spectrum, which is a blurred approximation to the velocity distribution in the region of observation.
187 citations
TL;DR: The complex static behavior of accommodation (focusing) and vergence (eye-turn) of the human eye was modeled as an interactive dual-feedback system and responses show good agreement with critical experimental data.
Abstract: The complex static behavior of accommodation (focusing) and vergence (eye-turn) of the human eye was modeled as an interactive dual-feedback system. Accommodative and vergence biases accounted for responses under the no stimulus condition. Analytical expressions were derived for relating the linear parameters in the model such as controller and cross gains to variables whose values could be obtained directly from experimental data. These parameters were incorporated into an interactive computer simulation program of the model. The computer simulation program was also used to obtain by trial and error the nonlinear parameters such as the lens plant saturation, accommodative controller gain for negative accommodative error, and the non-linear portion of vergence controller gain. The model responses show good agreement with critical experimental data.
177 citations
TL;DR: A model for the source of electrical interference and various parameter values are proposed and made use of experimentally obtained data for the model parameters to suggest optimal design for a two-electrode amplifier.
Abstract: ECG recordings normally use three electrodes?two for the differential inputs of the ECG amplifier and the third for ground. We analyze those situations where the ground electrode can be eliminated. We propose a model for the source of electrical interference and determine various parameter values. Making use of experimentally obtained data for the model parameters we suggest optimal design for a two-electrode amplifier. The two-electrode design is useful for biotelemetry, portable Holter monitors, and portable arrhythmia monitors. Under certain circumstances it may be useful for grounded monitoring equipment. The two-electrode technique has the advantage that it improves patient safety by eliminating the ground electrode. Fewer electrodes make patient attachment easier and lower electrode costs.
161 citations
TL;DR: The proposed technique can be used to estimate Pmax from a single ejecting beat by fitting the equation to the isovolumic portions of the pressure curve of ejecting contractions.
Abstract: The relationship between peak isovolumic developed pressure (Pmax) and end-diastolic volume can indicate ventricular contractility. Therefore, we propose a practical method to estimate Pmax from the pressure curve of an ejecting contraction of left ventricle. For the estimation, we first considered the left ventricle a linear time varying hydromotive pressure source (HMP(t)) coupled in series with an internal impedance. To formulate the HMP(t) we Fourier analyzed isovolumic pressure curves obtained under various conditions in six dogs. Since the higher order harmonics were found to be very small, HMP(t) could be described simply as where Pd = end-diastolic pressure and w = 2/T in which T is duration of contraction. Finally, HMP(t) for ejecting contraction was estimated by fitting the equation to the isovolumic portions of the pressure curve of ejecting contractions. The estimated Pmax values correlated well with actually observed Pmax values (r = 0.951, N = 24). We conclude that the proposed technique can be used to estimate Pmax from a single ejecting beat.
160 citations
TL;DR: This paper (Part II of two) presents an experimental demonstration of the performance achieved by implementing the mathematically derived optimal myoprocessor, and excellent agreement of the experimental results with the analytical predictions verifies the mathematical analysis.
Abstract: This paper (Part II of two) presents an experimental demonstration of the performance achieved by implementing the mathematically derived optimal myoprocessor described in Part I. Almost an order-of-magnitude improvement over the common myoprocessor is obtained. Excellent agreement of the experimental results with the analytical predictions verifies the mathematical analysis. The relative contributions of each stage of the optimal myoprocessor are examined. A discussion and comparison of several existing and proposed techniques for myoprocessor improvement are presented.
153 citations
TL;DR: A signal processing procedure is described which estimated the value of an acoustic attenuation coefficient of the liver in vivo from reflected ultrasound signals, and a correlation between the coefficient values and the liver diseases is indicated.
Abstract: Certain diffuse liver diseases, such as hepatitis and cirrhosis, are difficult to diagnose from the information contained in ultrasound images. A signal processing procedure is described which estimated the value of an acoustic attenuation coefficient of the liver in vivo from reflected ultrasound signals. The results of a clinical trial involving 14 patients indicate a correlation between the coefficient values and the liver diseases: inflamed livers produced lower values than cirrhotic livers. A series of 15 examinations on a volunteer indicates that the observed values are repeatable to within the statistical variation predicted by the mathematical model.
143 citations
TL;DR: For the indirect measurement of beat-to-beat systolic and diastolic pressure in the human finger, a new hydraulic servocontrol system was designed to maintain the vascular volume in the unloaded state to evaluate the accuracy of this method.
Abstract: For the indirect measurement of beat-to-beat systolic and diastolic pressure in the human finger, a new hydraulic servocontrol system was designed to maintain the vascular volume in the unloaded state The servocontrol system consists of a compression chamber equipped with an occluding cuff and a photoelectric plethysmograph, an electromagnetic shaker, and a volume servo circuit The shaker connected to a diaphragm actuator is used for controlling the cuff pressure The vascular volume change in the finger is detected by the photoelectric plethysmograph The plethysmographic signal is fed into the servo circuit to control the cuff pressure, which is clamped at a proper value corresponding to the unloaded vascular volume At this state the controlled cuff pressure follows the intraarterial pressure The accuracy of this method was evaluated using an in vitro vascular model of the finger Comparisons with direct measurement were carried out successfully in four normotensive and six hypertensive subjects
TL;DR: Close-loop systems employing closed-loop force feedback to provide regulation of contractions were investigated and were found to be stable and linear and to have good compensation for variations in muscle properties.
Abstract: The control of contractions elicited by electrical stimulation of muscle could be improved if there was a linear repeatable input-output relationship. The input is the command to the controlled stimulator and the output is the evoked contraction. Systems employing closed-loop force feedback to provide regulation of contractions were investigated in these studies. Force was modulated by both recruitment and temporal summation during intramuscular stimulation. Closed-loop systems with combined proportional and integral control were found to be stable and linear and to have good compensation for variations in muscle properties. A low proportional loop gain (approximately unity) was found necessary to prevent oscillation when modulating recruitment. Ratios of integral to proportional gain of about 10 gave the fastest response without compromising stability. The response time of the closed-loop system was as fast as or faster than the open-loop system.
TL;DR: Pulse amplitude and pulse width specifications are considerably broader for successful bidirectional rectangular wave shocks than for unidirectional rectangle wave shocks, and that appreciably higher first-shock successful defibrillation (96-99 percent) can be achieved with biddirectional waveforms.
Abstract: From 2760 fibrillation-defibrillation episodes in 100 kg calves, the effectiveness of reversing ventricular fibrillation of 30 s duration with symmetrical one-cycle bidirectional rectangular-wave shocks was determined. Pulse widths of 0.5-64 ms, pulse amplitudes of 35,50,70,100, and 140 A, and delivered pulse energies in the 93-1567 J range were employed in a primary study involving 39 animals. Families of curves relating percent successful defibrillation and the time intervals required for the return ofventricular activity and of normal sinus rhythm in the postdefibrillation electrocardiograms to the parameters of the delivered shocks were derived. In an eight-calf supplementary study involving 91-110 kg animals, the effectiveness of 50 A, 10 ms bidirectional rectangular wave shocks and 70 A, 6 ms unidirectional rectangular wave shocks were stringently compared by interlacing fibrillation-defibrillation episodes involving 120 bidirectional and 120 unidirectional shocks. When combined with previously published data for unidirectional wave shocks in 100 kg calves, our data suggest that pulse amplitude and pulse width specifications are considerably broader for successful bidirectional rectangular wave shocks than for unidirectional rectangular wave shocks, and that appreciably higher first-shock successful defibrillation (96-99 percent) can be achieved with bidirectional waveforms
TL;DR: Preliminary experimental results suggest that this approach may eventually yield improved clinical procedures, and a four-mass inverted pendulum dynamic model for the body as the basis for processing motion data transmitted directly from television cameras to an on-line computer.
Abstract: Conventional approaches to posturography typically make use of force-plate instrumentation to measure the movement of the center of pressure of ground reaction forces during quiet standing. This paper shows that such information can be obtained indirectly by using a four-mass inverted pendulum dynamic model for the body as the basis for processing motion data transmitted directly from television cameras to an on-line computer. Preliminary experimental results suggest that this approach may eventually yield improved clinical procedures.
TL;DR: The various classes of compartmental structure are presented, their fundamental properties are examined, their practical aspects of identification are considered, and the state of the art in the areas of metabolism, pharmacokinetics, ecology, and chemical kinetics is reviewed.
Abstract: This paper analyzes the reasons for the current marked interest shown by workers in the biosciences to applications of compartmental structures, both in regard to the special analytic properties of compartmental structures and the physiological properties to be attached to the compartments and intercompartmental flows. This paper presents the various classes of compartmental structure (perturbation and tracer, time varying, nonlinear, and stochastic), examines their fundamental properties (realizability, stability, observability and controllability, identifiability, and decomposability), considers practical aspects of identification, including computer programs, and reviews the state of the art in the areas of metabolism, pharmacokinetics, ecology, and chemical kinetics. The object of the review is to highlight the main streams of work via key references.
TL;DR: A new approach to the quantification of myocardial strain is introduced that utilizes the theoretical frame work of kinematics and can account for the large time-varying displacements present in the intact beating heart.
Abstract: We introduce a new approach to the quantification of myocardial strain. It utilizes the theoretical frame work of kinematics and can thus account for the large time-varying displacements present in the intact beating heart. For arbitrary small segments of myocardium, we show how these displacements can be described completely by a rotation tensor and a stretch tensor. We demonstrate the physiologic meaning of this analysis in an anesthetized dog. An epicardial region was seen to exhibit a local twist quantified by the rotation tensor and a segmental shortening quantified by the stretch tensor.
TL;DR: Polymeric coatings have been investigated to serve as a secondary moisture barrier in this work as discussed by the authors, where the electronic circuitry contacts infiltrating tissue fluids due to a corrosive breach in the hermeticity, failure of the device is almost immediate.
Abstract: Long-term implantable devices such as cardiac pacemakers are protected from corrosive tissue fluids by means of a metallic, hermetically sealed enclosure. When the electronic circuitry contacts infiltrating tissue fluids due to a corrosive breach in the hermeticity, failure of the device is almost immediate. Polymeric coatings have been investigated to serve as a secondary moisture barrier in this work.
TL;DR: If the geometry of the EEG generators is known, the smoothing process can be described quantitatively, and the spatial patterns of underlying neural activity can be restored within limits imposed by noise and instrumental imprecision.
Abstract: EEG waves recorded with electrode arrays on the brain surface give spatial patterns of cortical neural activity that are smoothed by the volume conductor properties of brain tissue. If the geometry of the EEG generators is known, the smoothing process can be described quantitatively, and the spatial patterns of underlying neural activity can be restored within limits imposed by noise and instrumental imprecision.
TL;DR: In this paper, a dimensionless solution of the heat conduction equation for laser irradiation of tissue has been extended to include transport of heat owing to blood flow and the importance of heat loss term is discussed in relation to the perfusion rate and exposure duration.
Abstract: A dimensionless solution of the heat conduction equation for laser irradiation of tissue has been extended to include transport of heat owing to blood flow The importance of the heat loss term is discussed in relation to the perfusion rate and exposure duration
TL;DR: The results indicate that the dielectric behavior of fluid-saturated compact bone in vitro, and, hence, possibly also of in vivo bone, is determined mostly by the fluid-fllled pores.
Abstract: The dielectric relaxation of bovine femoral compact bone specimens in vitro, saturated with 0.9 percent NaCI solution is determined by applying a constant current pulse and measuring the change in voltage with time. For specimens in which the current is in the plane perpendicular to the length of the whole bone and along the radial direction (radial specimens), the relaxation is confined to the time domain, t50 ?s; for longitudinal specimens, the relaxation, if any, would be for t1 ?s. The long-time resistivity of the latter is ?45 to 48 ?m; for the radial specimens, it is ?3 to 4 times greater. The resistivity of the fluid is 0.72 ?m. The results indicate that the dielectric behavior of fluid-saturated compact bone in vitro, and, hence, possibly also of in vivo bone, is determined mostly by the fluid-fllled pores. This has implications that contradict some of the commonly accepted views on the electromechanical effect in bone.
TL;DR: A volume algorithm is established which uses the data generated by computed tomography (CT) or ultrasound scans to calculate volume, based on a polyhedral reconstruction of an object of interest.
Abstract: A volume algorithm is established which uses the data generated by computed tomography (CT) or ultrasound scans. The algorithm is based on a polyhedral reconstruction of an object of interest. Phantom studies indicate that the algorithm calculated volume is accurate within 3 percent. In a controlled clinical experiment on a laboratory animal, the algorithm calculated volume showed a maximum error of about 5 percent. In less controllable applications to human clinical data, volume calculations showed variations ranging up to 16 percent.
TL;DR: It is shown that the minimum magnetic field required to produce observable effects is quite large, and for the best case, the rield required for a 10 percent reduction in conductivity is roughly 24 T.
Abstract: The effects of steady magnetic fields upon the conduction of a nerve impulse are considered. Microscopic chemical effects as well as those due to induced fields are ignored. Arguing from an analysis of transport properties, we show that the minimum magnetic field required to produce observable effects is quite large. For the best case, the rield required to produce a 10 percent reduction in conductivity is roughly 24 T.
TL;DR: A diagnostic system for ECG rhythm monitoring based on syntactic approaches to pattern recognition and context-free languages are used for describing the classes of abnormal and normal ECG patterns considered here.
Abstract: A diagnostic system for ECG rhythm monitoring based on syntactic approaches to pattern recognition is presented here. The method proposed exploits the difference in shape and structure between arrhythmic and normal ECG patterns to generate distinctly different descriptions in terms of a chosen set of primitives. A given frame of signal is first approximated piecewise linearly into a set of line segments which are completely specified in terms of their length and slope values. The slope values are quantized into seven distinct levels and a unit-length line segment with a slope value in each of these levels is coded as a slope symbol. Seven such slope symbols constitute the set of primitives. The given signal is represented as a string of such symbols based on the length and angle of the line segments approximating the signal. Context-free languages are used for describing the classes of abnormal and normal ECG patterns considered here. Analysis of actual ECG data shows efficiency comparable with that of existing methods and a saving in processing time.
TL;DR: A comprehensive analytical quantified derivation of the nonlinearity based upon an optimum processor approach to visual perception is presented, which follows optimum decision rules described by likelihood ratio tests applied to Poisson processes.
Abstract: Many visual phenomena, in particular, visual discrimination performance as a function of light intensity, have been attributed to a, nonlinearity in the retinal stages of the visual system. A comprehensive analytical quantified derivation of the nonlinearity based upon an optimum processor approach to visual perception is presented. The account follows optimum decision rules described by likelihood ratio tests applied to Poisson processes. The processor is constrained in ways inferred from empirical phenomena, particularly visual discrimination performance. A nonlinearity of the type y(x) = [log (x)]2, x 1, is mathematically derived applying rigorous engineering principles from statistical communications and signal detection theory. It is shown that this nonlinearity is in full conformity with known visual performance and the ideal detection hypothesis. The results are then confronted with actual physiological data to fimd a visual-system mechanistic correlate.
TL;DR: The IL 282 CO-Oximeter is a completely automated instrument for the simultaneous analysis of total hemoglobin (THb), oxyhemoglobin (O2Hb), % carboxyhemoglobin, and oxygen content (02 content) in a sample of blood.
Abstract: The IL 282 CO-Oximeter is a completely automated instrument for the simultaneous analysis of total hemoglobin (THb), % oxyhemoglobin (O2Hb), % carboxyhemoglobin (COHb), % methemoglobin (MetHb), and oxygen content (02 content) in a sample of blood.
TL;DR: An eight channel stimulation electrode has been developed which can be inserted into the human scala tympani via the round window as part of a neuroprosthesis aiming at the restoration of some hearing in cases of sensorineural deafness by electrical stimulation of the auditory nerve.
Abstract: An eight channel stimulation electrode has been developed which can be inserted into the human scala tympani via the round window. This electrode is part of a neuroprosthesis aiming at the restoration of some hearing in cases of sensorineural deafness by electrical stimulation of the auditory nerve.
TL;DR: Several digital signal processing techniques by which the detection of fetal R-waves is improved are theoretically developed and measured and analyzed for two sample fetal ECG inputs.
Abstract: The reliability of fetal heart rate (FHR) from external abdominal-lead electrocardiographic waveforms depends upon the R-wave detection capability of the monitoring device. Assuming that the maternal component of the ECG is canceiled by techniques described elsewhere [1]-[4], we are left with a fetal electrocardiogm (FECG) which may be conrupted by high noise levels. This paper describes several digital signal processing techniques by which the detection of fetal R-waves is improved. These techniques-narrow band-pass filtering, local peak differencing, autoregressive filtering, and matched filtering-are theoretically developed. The performance of each technique is measured and analyzed for two sample fetal ECG inputs.
TL;DR: The parameter values for this model are specific to the human eye movement systems; however, the form of the model is applicable to other neurological motor control systems.
Abstract: The parameter values for this model are specific to the human eye movement systems; however, the form of the model is applicable to other neurological motor control systems. The muscle length-tension diagram was modeled with an ideal spring. The muscle force-velocity relationship was linearized in a manner that produced a linear model. Initial parameter estimates were based on physiological data, human when possible. Then a function minimization program was used to fine tune model parameters. These parameter values were compared to the original physiological data to ensure that they were within the range of variability of the data. The antagonist dashpot value was selected to minimize the mean squared error between human and model responses; the value produced suggested a unique simplified representation for the original physiological data. The parameter estimation routine was applied to make the model match atypical human eye movements; these simulations suggested that glissades in normals are caused by pulsewidth, not pulse height errors.
TL;DR: The Geselowitz relationship, valid only for volumes of fixed geometry and static or quasi-static sources, is extended to volumes of fluctuating geometry and nonquasi-static sinusoidal sources.
Abstract: The Geselowitz relationship, valid only for volumes of fixed geometry and static or quasi-static sources, is extended to volumes of fluctuating geometry and nonquasi-static sinusoidal sources. The special case of filamentous sinusoidal sources is considered and the Geselowitz relationship is regained for the case of a fixed volume conductor in a quasi-static or static field.
TL;DR: An automated drug administration system is proposed to control the decrease in the mean arterial blood pressure of dogs by identifying a model for the open loop system consisting of a syringe pump and a dog.
Abstract: An automated drug administration system is proposed to control the decrease in the mean arterial blood pressure of dogs. It is accomplished by identifying a model for the open loop system consisting of a syringe pump and a dog. A linear feedback controller is then determined by solving an inverse optimum control problem. The chosen controller is optimal relative to a quadratic critexion. The controller is designed so that the mean arterial blood pressure is maintained at a desired level.