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Showing papers in "IEEE Transactions on Biomedical Engineering in 1973"


Journal ArticleDOI
TL;DR: The procedure for isolating the source of interference is applied to an exposition display in which each visitor could rapidly view his own ECG and possible equipment imperfections and guidelines for amplifier design are looked at.
Abstract: One of the major problems encountered in recording ECG's is the appearance of unwanted 60-Hz interference in the output. This paper examines the many possible sources of interference, and for each provides a description, an identifying test, and a remedy. Then we look at possible equipment imperfections and guidelines for amplifier design to aid in the evaluation of new developments in the field of electrocardiography. As an illustrative example, we apply the procedure for isolating the source of interference to an exposition display in which each visitor could rapidly view his own ECG.

399 citations


Journal ArticleDOI
TL;DR: A thin-diaphragm piezoresistive pressure sensor for biomedical instrumentation has been developed using monolithic integratedcircuit (IC) techniques because it provides an observable resistance change that is a linear function of pressure and is observable at low stress levels.
Abstract: A thin-diaphragm piezoresistive pressure sensor for biomedical instrumentation has been developed using monolithic integratedcircuit (IC) techniques. The piezoresistive effect has been chosen for this device because it provides an observable resistance change that is a linear function of pressure and is observable at low stress levels. A diaphragm is used as a stress magnifying device; its magnification is proportional to the square of the ratio of the diaphragm diameter to its thickness. The pressure-induced stresses in the diaphragm are sensed by properly oriented piezoresistors interconnected to form a bridge.

175 citations


Journal ArticleDOI
TL;DR: Synchronous excitation of an ensemble of elements in the nervous system generates field potentials in and around the ensemble that can provide information about neuronal function.
Abstract: Synchronous excitation of an ensemble of elements in the nervous system generates field potentials in and around the ensemble. Experimental analysis of these potentials can provide information about neuronal function.

134 citations


Journal ArticleDOI
TL;DR: A system for doing rapid and accurate measurements of neuronal processes in Golgi preparations, using a small digital computer which controls stepping motors attached to the stage and fine focus of a microscope is described.
Abstract: Rapid and accurate measurements of neuronal processes in Golgi preparations are possible with the aid of a small computer (Glaser and Van der Loos, 1965). This paper describes a system for doing this, using a small digital computer which controls stepping motors (0.5-?m steps) attached to the stage (x, y axes) and fine focus (z axis) of a microscope. The observer tracks the processes, topological information, such as the location of the soma, dendritic origins, branch points, and ends of processes, is signaled to the computer by special controls, and the x, y, and z coordinates of each are stored in digital format. The computer printout yields 1) individual x, y, and z coordinates with associated topological identifiers; 2) quantitative data for each dendritic segment in order (i.e., primary and secondary branches, etc.); and 3) computes the actual linear dimensions of each segment in microns. An associated oscilloscope display can 1) display the whole neuron, or individual processes, by connecting recorded points by vectors; 2) identify each dendrite; 3) rotate (continuously or by a specified angle) the whole cell, or individual dendrites, around any selected point or axis; and 4) indicate spatial relationships by dynamic rotation, intensity modulation, or stereo pairs. The performance of this system has been evaluated for accuracy and the repeatability of measurements.

128 citations


Journal ArticleDOI
TL;DR: A new formulation is presented for surface potentials produced on a homogeneous spherical volume conductor by an eccentric current dipole contained therein, free of interminancies for all relevant dipole locations and leads directly to the solution ofsurface potentials due to an eccentric quadripole.
Abstract: A new formulation is presented for surface potentials produced on a homogeneous spherical volume conductor by an eccentric current dipole contained therein. The formulation is free of interminancies for all relevant dipole locations and leads directly to the solution of surface potentials due to an eccentric quadripole.

115 citations


Journal ArticleDOI
TL;DR: To investigate the effects of band-limiting on the ECG, an ideal digital filter was implemented using the FFT and it was found that waveform notching is caused by frequencies over a wide passband, waveform amplitude information extends only to 200 Hz, and waveform duration information lies below 60 Hz.
Abstract: Electrocardiographic (ECG) signals were recorded from ten normal resting male subjects using two bipolar lead configurations: sternal and axillary. The recordings were made under low-noise conditions with a recording system bandpass extending from dc to 10 kHz. The ECG data were digitized and spectrally analyzed using a fast Fourier transform (FFT). The spectral analysis included both single ECG cycles and averaged ECG cycles. Slight differences were found between the averaged sternal and axillary ECG spectra in the low-frequency highamplitude range. An overall mean spectrum was produced as a bound for the normal resting male ECG spectrum as encountered in this study. The maximum value of this spectrum occurred at the fundamental (1.22 Hz); it had a -20-dB point at 36 Hz, -40-dB at 105 Hz, and -60-dB at 300 Hz. To investigate the effects of band-limiting on the ECG, an ideal digital filter was implemented using the FFT. It was found that waveform notching is caused by frequencies over a wide passband, waveform amplitude information extends only to 200 Hz, and waveform duration information lies below 60 Hz.

109 citations


Journal ArticleDOI
TL;DR: The authors have been able to differentiate between 12 dyslexic children and 13 normal age- and sex-matched children on the basis of spectral estimates of their electroencephalograms (EEG's).
Abstract: We have been able to differentiate between 12 dyslexic children and 13 normal age- and sex-matched children on the basis of spectral estimates of their electroencephalograms (EEG's). The children were monitored during various mental tasks and rest situations. Data dimensionality was reduced by ``banding'' various spectral components and eliminating others. The reduced spectral vectors were used as an input to a stepwise discriminant analysis program which, in effect, selected the variables most disparate between the two groups (dyslexic and normal).

67 citations


Journal ArticleDOI
TL;DR: The instantaneous power spectra of certain transition processes in the EEG (the evolution and blocking of the alpha wave) are calculated and described on the time-frequency plane.
Abstract: A statistical technique is described which allows description of the statistical characteristics of nonstationary electroencephalograms (EEG's) The EEG is investigated in terms of its nonstationary power spectrum The instantaneous power spectra of certain transition processes in the EEG (the evolution and blocking of the alpha wave) are calculated and described on the time-frequency plane

60 citations


Journal ArticleDOI
TL;DR: An apparatus is described which utilizes the above principle for mixing oxygen and nitrogen and the limitations of the applicability of tubler resistors due to nonlinear phenomena are discussed.
Abstract: A digital principle is described which permits a linear regulation of gas flow rate. The regulator unit consists of a set of on-off valves connected to parallel flow resistors. The conductivities of the resistors are 1, 2, 4, 8,...,n and combinations of the resisters give the flow rates 1, 2, 3, 4,..., 2 n -1. thus a stepwise regulation with a unit step of less then 1 percent of the maximal flow rate can be obtained by a step of 7 values and resisters. By using two ways valus and complementing with a second gas, binary mixtures of controlled composition (molor fraction) are produced. An apparatus is described which utilizes the above principle for mixing oxygen and nitrogen. The flow resisters are made of plastic tubing, and magentic values are used to permit electric control. The limitations of the applicability of tubler resistors due to nonlinear phenomena are discussed.

59 citations


Journal ArticleDOI
TL;DR: A platinum-glass microelectrode has been developed that permits chronic recording from single cortical neurons in unrestrained animals and without benefit of external manipulation.
Abstract: A platinum-glass microelectrode has been developed that permits chronic recording from single cortical neurons in unrestrained animals and without benefit of external manipulation. Details of fabrication and the surgical technique involved are presented. A discussion of the relevant mechanical considerations is also included. A prime advantage of the method is the ease with which it may be realized in the standard neurophysiologic laboratory.

58 citations


Journal ArticleDOI
TL;DR: An engineering analysis is presented to estimate motions of the microelectrode tip with respect to the adjacent neural tissue in terms of the geometry and material properties of the electrode, its lead wire, and the cortex to gain understanding of a recently reported successful recording system.
Abstract: To obtain chronic recordings from single nerve cells in the cerebral cortex it is necessary to prevent motion of the microelectrode tip with respect to the adjacent neural tissue. This paper presents an engineering analysis to estimate these motions in terms of the geometry and material properties of the electrode, its lead wire, and the cortex. The results are used to gain an understanding of a recently reported successful recording system, and to thereby provide a design guide for future systems. In addition, a buckling analysis is presented for a class of microelectrodes to enable a minimum size to be achieved with an adequate safety margin.

Journal ArticleDOI
TL;DR: Electrode tip size as well as location is found to be critical in recording high spike amplitudes, suggesting that the paths for current flow in central nervous system (CNS) tissue may be extremely small.
Abstract: Microelectrodes fabricated using integrated-circuit technology are shown to be suitable for extracellular single-unit recording, and the factors influencing electrode-cell coupling are discussed. Electrode tip size as well as location is found to be critical in recording high spike amplitudes, suggesting that the paths for current flow in central nervous system (CNS) tissue may be extremely small.

Journal ArticleDOI
TL;DR: A mathematical model has been derived that describes the pressure-flow relationship in the ventilatory system under conditions of constant lung volume and a collapsible airway segment is included to model compression of the airways during expiration.
Abstract: A mathematical model has been derived that describes the pressure-flow relationship in the ventilatory system under conditions of constant lung volume. The parameters of the model include small airway resistance, large airway resistance, and lung elastic recoil. A collapsible airway segment is included to model compression of the airways during expiration.

Journal ArticleDOI
TL;DR: A unity-gain buffer amplifier with an input capacity below 0.01 pF and an input resistance above 10 12 ?
Abstract: A unity-gain buffer amplifier with an input capacity below 001 pF and an input resistance above 10 12 ? is described Low input capacity is achieved without the necessity of feedback adjustments by bootstrapping the entire input stage, including power sources and shielding The amplifier is of simple design and is based around commercially available operational amplifiers

Journal ArticleDOI
TL;DR: Several powered prosthetic systems that are in practical use are reviewed and put in perspective with respect to body-powered systems and an appraisal is made of development trends in the field.
Abstract: The clinical importance of existing powered prosthetic devices is investigated. In this regard, several powered prosthetic systems that are in practical use are reviewed and put in perspective with respect to body-powered systems. The unique problems of delivery and maintenance of these systems are discussed as are practical design limitations. An appraisal is made of development trends in the field and the author's viewpoint on the optimal environment for practical advances in the field is presented.

Journal ArticleDOI
TL;DR: A numerical approach to obtain the temperature distribution in layered tissues with thermal source and cooling inside the tissues is presented and the results obtained agree well with six available experiments.
Abstract: A numerical approach to obtain the temperature distribution in layered tissues with thermal source and cooling inside the tissues is presented in this paper. This approach can be applied to problems with a distributed internal thermal source produced by external radiation such as microwave, ultrasound, and shortwave, or by internal increase of metabolic rate in live subjects. The exact mechanism of cooling is not discussed here, but it is assumed to be due to blood flow in vivo. The calculation of the temperature distribution in layered tissues is based on a linear model of the tissues that consists of several layers of different kinds of tissues separated by parallel boundaries. Some simple mathematical forms of the cooling functions are also assumed in this paper. The results obtained agree well with six available experiments.

Journal ArticleDOI
TL;DR: A capacitive-type electrode using barium titanate ceramics is described, especially suitable for EEG recording because its surface is chemically inactive and mechanically strong, and its noise voltage is minimum from the beginning of its installation.
Abstract: A capacitive-type electrode using barium titanate ceramics is described. This electrode is not affected by the polarization potential. Because its surface is chemically inactive and mechanically strong, its noise voltage is minimum from the beginning of its installation. This device is especially suitable for EEG recording.

Journal ArticleDOI
TL;DR: This paper attempts to indicate the feasibility of closed-loop control of balloon pumping, and particularly its flexibility in achieving both diastolic augmentation of mean aortic pressure and control of the level of end-diastolic pressure (EDP) -an important factor in reducing heart work.
Abstract: A closed-loop control scheme for the control of intra-aortic balloon pumping has been developed and tested in dog experiments. A performance index reflecting the general objectives of balloon-assist pumping is developed and a modified steepest ascent control algorithm is utilized for the selection of a proper operating point for the balloon during its pumping cycle. This paper attempts to indicate the feasibility of closed-loop control of balloon pumping, and particularly its flexibility in achieving both diastolic augmentation of mean aortic pressure and control of the level of end-diastolic pressure (EDP)-an important factor in reducing heart work.

Journal ArticleDOI
TL;DR: The specific resistance (?) of canine blood, having a hematocrit (H) range extending from 0 to 70 percent, was measured at 37°C and 25 kHz using a variable-length conductivity cell connected to a constant-current impedance bridge.
Abstract: The specific resistance (?) of canine blood, having a hematocrit (H) range extending from 0 to 70 percent, was measured at 37°C and 25 kHz using a variable-length conductivity cell connected to a constant-current impedance bridge. A least-squares exponential fit for the experimentally determined dataprovided the relationship ?= 56.8e 0.025H with a correlation coefficient of 0.989. The data obtained were also fitted to the Maxwell-Fricke equation; an excellent fit was obtained in the range of 0-50 percent hematocrit using a form factor of 2.5.

Journal ArticleDOI
TL;DR: Reevaluation over 1-3-week intervals indicates that the quantitative measures of tremor scores are reliable, and the predominant tremor frequency as measured from the tremor-power spectra is found to be independent of learning effects.
Abstract: A compensatory tracking task using a visual display and augmented auditory feedback and requiring subjects to maintain a 500-gm force on a control stick has been modified for clinical use. Integrated absolute values of the subjects' force error/second (tremor scores) have been used as a measure of steadiness, and power spectra of the force error have been used to establish the predominant tremor frequencies. Twenty parkinsonian patients, 7 age-matched controls, and 20 young controls have been evaluated, and representative tremor-time records, tremor scores, and tremor-power spectra are presented. The quantitative measures have proven sensitive to individual differences among normals, yet having a dynamic range sufficient to include the most severely afflicted patient tested. Normative values of both tremor scores and predominant tremor frequencies have been established and are significantly different from the parkinsonian values, the parkinsonian patients having a higher average tremor score [8.31 versus 3.76 (gram . seconds/second)] and a lower mean predominant tremor frequency (6.6 Hz versus 7.9 Hz). Representative tremor-power spectra have proven useful in describing physiological and parkinsonian tremors. Reevaluation over 1-3-week intervals indicates that the quantitative measures of tremor scores are reliable (r= 0.83, p < 0.01 for control subjects; r = 0.87, p < 0.01 for parkinsonian patients). In addition, the predominant tremor frequency as measured from the tremor-power spectra is found to be independent of learning effects. It is emphasized that such tests are not designed as diagnostic tools in themselves.

Journal ArticleDOI
TL;DR: The rectified second derivative of the original EEG tracing is utilized for this purpose and has proven satisfactory in connection with the type of question asked and is inexpensive and easy to carry out.
Abstract: A method of semiautomatic quantification of sharpness of EEG phenomena is described. The rectified second derivative of the original EEG tracing is utilized for this purpose and has proven satisfactory in connection with the type of question asked. The method is inexpensive and easy to carry out.

Journal ArticleDOI
TL;DR: A microminiature pressure transducer is described utilizing a variable air capacitor driven by a pressure-sensitive deflectible silicon membrane as the detection mechanism and initial test results under static pressure conditions are reported.
Abstract: A microminiature pressure transducer is described utilizing a variable air capacitor driven by a pressure-sensitive deflectible silicon membrane as the detection mechanism. Silicon integrated circuit technology is used throughout for economical batch fabrication of the device. Prototype devices have been fabricated and initial test results under static pressure conditions are reported. Equivalent gauge factors of over 500 for this variable capacitance device are about a factor of 5-10 better than the best theoretically designed silicon strain gauges in the size range necessary for catheter insertion. Temperature independence and increased linearity are also important advantages of this variable capacitance sensor head.

Journal ArticleDOI
TL;DR: The novel solution to this problem is to maximize the integral of the video light-loss signal above a threshold, when the threshold is arbitrarily set above background and within the range of grayness of the image.
Abstract: Uncertainty in locating optimum focus can be a major problem when a scanning microscope is used as an input to a quantitative image-analysis system Our novel solution to this problem is to maximize the integral of the video light-loss signal above a threshold, when the threshold is arbitrarily set above background and within the range of grayness of the image This algorithm has been incorporated into a real-time analog device to monitor the quality of focus The focus-assist device uses IC operational amplifiers and has a bandpass of 05 MHz When the device is used with images of metaphase chromosomes, the standard deviation of optimum focus is reduced to 009 ?m as contrasted to the unassisted value of 037 ?m The device is simple, fast, reliable, and extremely sensitive It should have general application to both macro- and microscopic scanning systems

Journal ArticleDOI
TL;DR: For a 5-s exposure, the threshold current for fibrillation varies almost as the square root of body weight (W), the general expression being I = KW ?
Abstract: This paper reports the threshold 60-Hz alternating-current values required to induce ventricular fibrillation when the current is applied to electrodes at different sites on the surface of the bodies of rabbits, puppies, one monkey, dogs, goats, and ponies. It is shown that for a given body weight, the duration of exposure to current influences the fibrillation threshold; exposure times shorter than 1 s require more current. For a given duration of current flow, the threshold current for fibrillation is a function of body weight and electrode location. The lowest current for fibrillation was required with lead III (left forelimb-left hindlimb) and lead I (right-left forelimbs) required the highest current. For a 5-s exposure, the threshold current for fibrillation varies almost as the square root of body weight (W), the general expression being I = KW ? , where ? is nearly 0.5. Values for K and ? are presented for leads I, II, and III.

Journal ArticleDOI
Toyohisa Kaneko1, Paolo Mancini
TL;DR: The method described takes advantage of the known location of the boundary on previous frames and is a fast computing algorithm and relatively insensitive to white noise because the resultant positive and negative weights tend to cancel this effect.
Abstract: A cardiac cineangiogram is an X-ray motion picture of the heart. Boundary detection is an essential task to compute valuable quantitative information such as the temporal volume change and the wall velocity. Previously, boundary detection methods treated frames independent of each other. Consecutive frames of a motion picture are, however, highly correlated and therefore this property can be exploited. The method described takes advantage of the known location of the boundary on previous frames. The previous boundary is divided into a set of segments along which local rectangular regions are set up on the present frame. This boundary is approximated by a set of straight lines which minimize the square error in each rectangular region with the spatial derivative as its weight. The method is a fast computing algorithm and relatively insensitive to white noise because the resultant positive and negative weights tend to cancel this effect. An experiment was carried out, and good agreement with boundaries detected by humans was obtained.

Journal ArticleDOI
TL;DR: An algorithm for the automatic computation of the cardiothoracic ratio is presented and in experiments using 100 sheets of 14-by 14-in postero-anterior chest radiographs, a tolerable error of ±4 percent was satisfied in 86 percent of all trials.
Abstract: An algorithm for the automatic computation of the cardiothoracic ratio is presented. In experiments using 100 sheets of 14-by 14-in postero-anterior chest radiographs, a tolerable error of ±4 percent was satisfied in 86 percent of all trials. The processing time is about 1 s. The goal of this study is to provide radiologists with practical Instruments for the automated mass screening of heart disease. A minicomputer and a conventional vidicon camera are used in the experimental system.

Journal ArticleDOI
TL;DR: A network model of ventricular function consisting of a source of pressure with a series internal resistance that is coupled to a load resistance is presented as an analog of left ventricular (LV) function during the ejection phase of the cardiac cycle to quantitate the interaction of ventricle and load.
Abstract: A network model of ventricular function consisting of a source of pressure with a series internal resistance that is coupled to a load resistance is presented. It is used as an analog of left ventricular (LV) function during the ejection phase of the cardiac cycle in order to quantitate the interaction of ventricle and load.

Journal ArticleDOI
TL;DR: Using pacemakers implanted in canines with surgically induced atrioventricular blocks, the effects of the microwave-oven frequencies and two radar frequencies were evaluated and a narrow zone of inhibition during some exposures is reported.
Abstract: Using pacemakers implanted in canines with surgically induced atrioventricular blocks, the effects of the microwave-oven frequencies (915 and 2450 MHz) and two radar frequencies (2810 and 3050 MHz) were evaluated. Quantitative evaluation of these fields with respect to complete inhibition of pacemakers can be made. A narrow zone of inhibition during some exposures-a ``window'' effect-not previously described is reported. The following field parameters would be regarded as potential situations for complete pacemaker inhibition: 1) 915-MHz-fields continuous- and sine-wave modulation at 120 Hz in field strengths over 75 V/m, and 2) fields at either 2810 or 3050 MHz pulsed at a rate of 40 pulses per second (pps) or less with a field strength greater than 250 V/m.

Journal ArticleDOI
TL;DR: Control functions, system motions, and other characteristics which are obtained from the mathematical synthesis of ``optimal'' bipedal locomotion gaits with respect to locomotion criteria (to be minimized) defined in the paper are considered.
Abstract: The control functions, system motions, and other characteristics which are obtained from the mathematical synthesis of ``optimal'' bipedal locomotion gaits with respect to locomotion criteria (to be minimized) defined in the paper are considered. Results are presented for three mathematical biped models and several locomotion criteria (objective functions). Optimal walking trajectories and associated control functions are synthesized using the optimal programming method of [1]. In the synthesis approach, the model structure and locomotion criterion determine the optimal controls motion and foot placement parameters. These effects are examined, and qualitative comparisons to human walking patterns are suggested. These studies also provide quantitative information for the design of prostheses and walking machines, for example: ranges of suitable motion patterns (as functions of time) and magnitudes of controlling efforts and energy requirements.

Journal ArticleDOI
TL;DR: The theory indicates that simple rules for correction exist and that a bestguess conversion from damaged pulse train to undamaged version can be performed by graphical means.
Abstract: The serial correlogram (SCG) is used to determine the amount of dependence in spike-interval sequences. This communication demonstrates the effects of measurement errors [i.e., false alarms (FA's) and false dismissals (FD's) in spike-detection algorithms] on correlation coefficients when the sequence has a practical sample size.