Showing papers in "IEEE Transactions on Biomedical Engineering in 1975"
TL;DR: An electrically calibrated plethysmograph which may be used with all lengths of mercury-in-rubber strain gauges and linearity of the output for large changes in gauge resistance has been insured by the incorporation of a constant-current bridge supply.
Abstract: This paper describes an electrically calibrated plethysmograph which may be used with all lengths of mercury-in-rubber strain gauges. Due to the very low resistance of these strain gauges, electrical calibration of previously available plethysmographs has suffered from errors caused by lead-wire resistance. The present instrument eliminates lead-wire errors by a design which effectively places the strain gauge at the corners of the measurement bridge. Linearity of the output for large changes in gauge resistance has been insured by the incorporation of a constant-current bridge supply.
342 citations
TL;DR: A multielectrode structure containing integrated junction-FET input stages is described, and simultaneous recording and stimulation from closely adjacent areas of brain should be possible with virtually no stimulus artifact.
Abstract: A multielectrode structure containing integrated junction-FET input stages is described. Photoengraved microelectrodes are utilized to obtain high dimensional precision, small size, and extremely low capacitive coupling between electrodes. The interelectrode capacitance is less than 0.01 pf. The integrated input devices (JFET's) reduce the impedance levels on the recording channels to less than 500 ohms, virtually eliminating crosstalk and stray noise pickup from the system. The n-channel JFET's operate as source-followers from a common 2.5 volt drain supply and have input impedances greater than 100 megohms at 1 kHz. A simple external preamplifier ensures stable operation and easy interfacing with conventional recording and display equipment. Special considerations in the design of low-noise completely integrated input stages for use with metal microelectrodes are discussed in detail. As a result of the low interelectrode coupling in this structure, simultaneous recording and stimulation from closely adjacent areas of brain should be possible with virtually no stimulus artifact.
184 citations
TL;DR: A critical relation was demonstrated between percent stenosis and the minimum coronary perfusion pressure necessary to maintain a given Q, a contributing factor toward effort angina.
Abstract: Human coronary artery stenosis can have dramatic hemodynamic effects on coronary flow rate and perfusion. To quantitatively investigate these relationships, nineteen proximal coronary arteries with varying focal stenoses (2%-98%) were dissected from fresh post mortem adult hearts and perfused with isotonic glycerol saline (n = 2.7 centipoise) at constant pressures of 30, 50, 75, 100, 150 and 200 mm Hg, while varying the distal bed resistance (r b ) over the range 0.1 to 5 mm Hg/ml/min. Flow rate (Q) and arterial segment pressure drop (?P) were measured at each perfusion pressure and r b , and a permanent cast of silicone rubber was made under 100 mm Hg pressure following perfusion. Hydraulic resistance (R = ?P/Q) tended to be constant at low Q (10-30 ml/min), with resistance increasing 2 or 3 times at higher Q (30-100 + ml/min). Curves of Q vs. % stenosis showed that Q was relatively constant with stenoses less than 70-80%. With a small further increase in stenosis, however, Q decreased dramatically. Furthermore, significant reductions occurred at lower % stenoses for greater demands (lower r b ), a contributing factor toward effort angina, as less severe stenoses became increasingly significant under flow demand. Elastic effects in eccentric lesions produced additional flow losses at lowered perfusion pressures. In addition, a critical relation was demonstrated between percent stenosis and the minimum coronary perfusion pressure necessary to maintain a given Q.
160 citations
TL;DR: A technique is proposed for estimating the degree of wide-sense stationarity and thedegree of Gaussianity of an ensemble of EEG records and results which have been obtained by applying this technique to three relatively large ensembles of multichannel EEG data.
Abstract: Considerable motivation exists for the development of an adequate statistical model for spontaneous electroencephalographic (EEG) activity. At present, almost all methods of time-domain and frequency-domain EEG analysis are based on implicit assumptions regarding the statistical characteristics of the underlying random process, particularly with respect to the extent of stationarity and Gaussianity of the process. However, the actual characteristics of specific EEG ensembles have not been extensively investigated. In this paper, a technique is proposed for estimating the degree of wide-sense stationarity and the degree of Gaussianity of an ensemble of EEG records. Results which have been obtained by applying this technique to three relatively large ensembles of multichannel EEG data are also described. In addition, the comparative advantages of employing alternate methods of EEG analysis are discussed in relation to the estimated degree of stationarity and Gaussianity of the particular EEG ensembles under consideration.
157 citations
TL;DR: Employing a Wheatstone bridge, skin conductance was measured over those putative acupuncture points on the large intestine and pericardium meridians lying between the metacarpophalangeal joints and the elbow to demonstrate the presence of acupuncture points at most acupuncture points.
Abstract: Employing a Wheatstone bridge, skin conductance was measured over those putative acupuncture points on the large intestine and pericardium meridians lying between the metacarpophalangeal joints and the elbow Results were compared to those from anatomically similar locations devoid of acupuncture points At most acupuncture points on most subjects, there were greater electrical conductance maxima than at control sites
147 citations
TL;DR: Electrocardiographic data compression via orthogonal transform processing is studied using canine ECG data using the Haar transform and the discrete cosine transform.
Abstract: Electrocardiographic data compression via orthogonal transform processing is studied using canine ECG data. The Haar transform and the discrete cosine transform are considered. While the basis vectors for the Haar transform are sampled rectangular waves, those for the discrete cosine transform are sampled sinusoids.
146 citations
TL;DR: A detailed analysis shows how electrosurgical r-f power is localized in the vicinity of the cutting electrode, and supports the supposition that evolving steam bubbles in the tissue at the surgical tip continuously rupture the tissue and are responsible for the cutting mechanism.
Abstract: A detailed analysis shows how electrosurgical r-f power is localized in the vicinity of the cutting electrode. This localization requires a small radius of curvature for the surgical tip, relatively high r-f voltages, and rapid surgical tip motion. The erratic results sometimes encountered in electrosurgery may be due to a deficiency in the above procedures as well as a lack of care in the use of the r-f leads and ground plates. A further analysis supports the supposition that evolving steam bubbles in the tissue at the surgical tip continuously rupture the tissue and are responsible for the cutting mechanism.
130 citations
TL;DR: The interaction of electromagnetic plane waves with multilayered spherical models composed of lossy dielectric media that represent different biological tissues found in human and animal heads is examined in the frequency range 0.1 to 10 GHz.
Abstract: The interaction of electromagnetic plane waves with multilayered spherical models composed of lossy dielectric media that represent different biological tissues found in human and animal heads is examined in the frequency range 0.1 to 10 GHz. The model ranges in size from 2 to 12.5 cms outer radius and consists of a core of brain-like material surrounded by five outer layers of CSF, bone, fat and skin-dura tissues. The absorption properties of the model have been analyzed throughout this range of size and frequency. The distribution of internally deposited energy has also been investigated in detail for three basic spheres of 3.3, 6 and 10 cms radii, with emphasis on the creation of localized regions of strong heating (hot-spots). Based on these results, some generalized conclusions are presented on the interaction of microwaves with different sized biological objects.
125 citations
TL;DR: The theoretical analysis shows that theabsolute value of the ensemble average of the Fourier transform of the simulated EMG approaches the absolute value ofThe Fourier Transform of the motor unit potential.
Abstract: The electromyogram of a single motor unit is studied by considering it as a time function defined by a convolution integral where a point process input passes through a filter whose impulse response is the shape of a single motor unit action potential. The interspike intervals are assumed to be normally distributed, independent random variables. Simulation is performed on a digital computer. The theoretical analysis shows that the absolute value of the ensemble average of the Fourier transform of the simulated EMG approaches the absolute value of the Fourier transform of the motor unit potential. This has been confirmed by simulation except at the very low end of the spectrum. These results are compared with the Fourier transforms of the recorded surface EMG data from human muscles.
107 citations
TL;DR: A percutaneous wire electrode has been developed which permits long-term recording of intramuscular EMG signals and has demonstrated reliable EMG recording for periods of up to thirteen months.
Abstract: A percutaneous wire electrode has been developed which permits long-term recording of intramuscular EMG signals. The electrode consists of a small coil wound from 0.0011 inch diameter wire and filled with silicone rubber. Easily inserted by means of a hypodermic needle, it has demonstrated reliable EMG recording for periods of up to thirteen months.
83 citations
TL;DR: It was found that the heating potential is always non-uniformly distributed, and in cases where it was maximum inside the sphere it was larger by a factor of approximately ten to the values calculated by the plane slab or the average cross section model.
Abstract: The distribution of the heating potential inside a lossy sphere having the same electrical characteristics as those of brain tissue was investigated in the frequency region of 10 MHz to 12 GHz. The conditions under which a potential hot spot appears inside the sphere and its shape were determined and were displayed in a radius vs. frequency diagram. The results show that hot spots appear inside only for spheres with radii 8 cm > R > 0.1 cm and only in the frequency range of 300 < f < 12,000 MHz. It was found that the heating potential is always non-uniformly distributed, and in cases where it was maximum inside the sphere it was larger by a factor of approximately ten to the values calculated by the plane slab or the average cross section model.
TL;DR: The results of the present work indicate that with the use of approximate signal and noise covariance matrices, it is possible to achieve estimates of this potential distribution with an average sum squared error of twenty-five percent.
Abstract: This paper examines the feasibility of utilizing statistical constraints on the inverse potential model to determine the potential distribution over a 4 cm sphere surrounding the heart from perturbed torso potentials. These perturbed torso potentials reflect instrumentation, quadrature, electrode placement, and heart position uncertainties. This work is an extension of the authors' previous work which concluded that it is not feasible to determine this same potential distribution using unconstrained solutions. However, the results of the present work indicate that with the use of approximate signal and noise covariance matrices, it is possible to achieve estimates of this potential distribution with an average sum squared error of twenty-five percent. Further, the estimation of the signal and noise covariance matrices can be accomplished with a knowledge of heart geometry, torso geometry, The approximate measurement error, and a rough estimate of the time an average section of myocardium is depolarized, but without an a priori specification of the activation sequence.
TL;DR: The body current activated circuit breaker (BAB), provides a new means of protection from accidental electric shock by senses the current flowing in the body and reacts to, a dangerous situation by interrupting the power source.
Abstract: The body current activated circuit breaker (BAB), provides a new means of protection from accidental electric shock. It senses the current flowing in the body and reacts to, a dangerous situation by interrupting the power source. An experimental model using a toroidal coil sensor was built and tested successfully.
TL;DR: The nuclear magnetic relaxation time T1 of protons in human blood has been measured as a function of frequency, pH, and hematocrit, and qualitative agreement is found.
Abstract: The nuclear magnetic relaxation time T 1 of protons in human blood has been measured as a function of frequency, pH, and hematocrit. For whole blood at 25°C, T 1 is approximately 0.1 s at 20 kHz, increasing to approximately 1 s at 50 MHz. T 1 of whole blood is analyzed in terms of the exchange of water molecules between plasma and erythrocyte cytoplasm. A cellular residence time of 19 ms provides the best fit to the data. The T 1 values for plasma and cytoplasm are explained in terms of their protein content, using the well-established theory of nuclear relaxation in macromolecular solutions. The plasma and cytoplasm data are compared with previous T 1 results for apotransferrin and hemoglobin solutions, respectively, and qualitative agreement is found. The T 1 values increased with decreasing pH, as is expected from existing data on hemoglobin solutions.
TL;DR: The feasibility of computer classification of profusion was investigated and an alternative or supplement to the presently used visual analysis is demonstrated, providing positive evidence for a quantitative approach to the classification ofprofusion.
Abstract: The accurate categorization of profusion of opacities in radiographs of coal workers is a significant medical problem. In this study, the feasibility of computer classification of profusion was investigated. Standard pattern recognition techniques were used except for the spatial moments which were computed as measurements of the texture patterns. A normal-abnormal classification was performed on 178 zonal samples and resulted in a training classification rate of 99% and a testing rate of 97%. A four category classification was also performed for the zonal samples with a correct classification rate of 84%. The zonal decisions were used to obtain overall film profusion. The results of this classification compared favorably with readings by radiologists. This study provides positive evidence for a quantitative approach to the classification of profusion. The significance of this study with respect to the understanding and measurement of lung pathology from radiographs is that an alternative or supplement to the presently used visual analysis is demonstrated.
TL;DR: The algorithms by which fast phases are detected, and by which slow phase cumulative eye position is extrapolated across the fast phase interval are described.
Abstract: A digital computer program, MITNYS-II, has been developed for on-line analysis of nystagmus which results from visual, vestibular or caloric stimulation. The program accepts sampled records of eye position and yields cumulative slow phase position, slow phase velocity, instantaneous fast phase frequency and other parameters in 25 ms. In this paper the algorithms by which fast phases are detected, and by which slow phase cumulative eye position is extrapolated across the fast phase interval are described. Extensive tests with vestibular, optokinetic and caloric nystagmus yield reliability figures of the order of 2% for false identification of fast phases and missed fast phases. MITNYS-II has been successfully employed to interpret clinical EOG records, examples of which are presented.
TL;DR: The feasibility of developing a computer-based EEG pattern recognition system capable of continuously estimating the level of anesthesia of patients during surgical operations is investigated in this paper.
Abstract: Recent advances in the fields of automatic EEG analysis and pattern recognition provide a valuable new perspective for reconsidering the question of whether or not the level of anesthesia can be reliably estimated by analyzing spontaneous EEG activity. The feasibility of developing a computer-based EEG pattern recognition system capable of continuously estimating the level of anesthesia of patients during surgical operations is investigated in this paper. Anesthetists were asked to define five clinically significant levels of anesthesia for a commonly used anesthetic in terms of meaningful non-EEG criteria. The subsequent development of various EEG pattern recognition systems in an attempt to reliably estimate the levels of anesthesia as determined by the non-EEG criteria is described. All such systems employ Bayes decision rule under the assumption that pattern features are statistically independent. System performance is evaluated in terms of the estimated probability of misclassification error. Systems based on the recognition of spectral or frequency-domain EEG patterns are compared to those based on the recognition of time-domain EEG patterns.
TL;DR: The Choroidal Eye Oximeter is an electro-optical instrument that non-invasively measures the oxygen saturation of choroidal blood in the back of the human eye by a spectrophotometric method.
Abstract: The Choroidal Eye Oximeter is an electro-optical instrument that non-invasively measures the oxygen saturation of choroidal blood in the back of the human eye by a spectrophotometric method. Since choroidal blood is characteristic of blood which is supplied to the brain, the Choroidal Eye Oximeter is essentially using the eye as a ``window'' to look into the brain. The instrument can thus be used to monitor the amount of oxygen which is supplied to the brain under varying external conditions. The instrument consists of two basic systems: the Optical System and the Electronic System. The Optical System produces a suitable bi-chromatic beam of light, reflects this beam from the fundus of the subject's eye, and onto a low-noise photodetector. The Electronic System amplifies the weak composite signal from the photodetector, separates the two spectral components, computes the average oxygen saturation from the area of the fundus that was sampled, and displays the value of the computed oxygen saturation on a panel meter. The instrument may be used with a chart recorder to continuously record the kinetic changes of either the oxygen saturation or the fundus reflectivity at each of the two measuring wavelengths.
TL;DR: It is demonstrated that two important physical constraints are operating which require the flow and vortex sources to be, in effect, one-to-one with each other.
Abstract: Recent papers have shown that the ECG depends on the flow sources of the impressed field in the heart while the MCG is a function of its vortex source distribution. It has consequently been suggested that body surface electric and magnetic recordings yield completely independent information about the physiological generators. Such independence would be of enormous significance wherever present diagnostic procedures rely heavily on the ECG or EEG. This paper points out that the independence of the flow and vortex sources is only a mathematical possibility. It demonstrates that two important physical constraints are operating which require the flow and vortex sources to be, in effect, one-to-one with each other. Consequently, the electric and magnetic fields arising from excitable tissue in an assumed homogeneous volume conductor are fundamentally interdependent.
TL;DR: This study shows that currents produced during the generation or discharge of static electricity can be easily and accurately measured, and the technique used may be applicable to other areas of investigation.
Abstract: Triboelectric noise resulting from motion in the patient vicinity has been observed to occasionally interfere with the ECG. Experiments were performed to verify the nature of the interference and to define the factors which enable this ever-present phenomenon to interfere with ECG acquisition. No instances have been observed that could not be corrected by good electrode placement technique. This study shows that currents produced during the generation or discharge of static electricity can be easily and accurately measured, and the technique used may be applicable to other areas of investigation.
TL;DR: An on-line focusing procedure for a computer-controlled microscope employed in the measurement of human chromosome images is discussed and has proved insensitive to imperfections in the scanner photocathode.
Abstract: An on-line focusing procedure for a computer-controlled microscope employed in the measurement of human chromosome images is discussed. The method is based on an algorithm proposed by Mendelsohn and Mayall. A focusing accuracy of standard deviation less than 1/20th micron in the slide-objective distance has been achieved. Changes of the focus position with time, and for individual chromosomes within a metaphase, have been investigated. The method has proved insensitive to imperfections in the scanner photocathode. The method has also been used to determine the autofocusing accuracy of an analog metaphase-finding apparatus.
TL;DR: The problems associated with measuring the local electric field in a medium with spatally inhomogeneous electrical constitutive parameters like biological tissue are discussed and a systematic experimental study of both types of probes is presented.
Abstract: The problems associated with measuring the local electric field in a medium with spatally inhomogeneous electrical constitutive parameters like biological tissue are discussed. Simple theoretical analyses that describe the operation of electrically short bare and insulated electric field probes in a dissipative medium are presented. The conditions that must be satisfied for each of these probes to have an electric field response that is independent of the electrical constitutive parameters of the surrounding tissue are determined. The results of a systematic experimental study of both types of probes are presented. In the study the probes were immersed in a succession of liquids with dielectric properties similar to those for biological tissues at radio frequencies.
TL;DR: The electronic implementation of the detection procedure is dedicated to the extraction of the left ventricular contour out of angiographs, and will lead to a considerable time saving and improved reproducibility.
Abstract: Structures characterized by a brightness contour can be automatically detected when the information is carried by a video signal. The detection system described here processes the available position and brightness information of the picture in a way closely related to the features of such structures. Real time processing of the picture information is made possible by the use of very simple memories. The electronic implementation of the detection procedure is dedicated to the extraction of the left ventricular contour out of angiographs. Compared with manual contour tracking the application in diagnostic cardiology will lead to a considerable time saving and improved reproducibility.
TL;DR: The influences of phase shifts are extremely important in the determination of filtered waveforms and therefore in the interpretation of many biosignals, and are significant because large time displacements result from small phase deviations in the vicinity of the corner frequency.
Abstract: The influences of phase shifts are extremely important in the determination of filtered waveforms and therefore in the interpretation of many biosignals. Low frequency shifts from high pass filtering, for example, are significant because large time displacements result from small phase deviations in the vicinity of the corner frequency. If a filter with a symmetric time response is employed, no phase shift will ensue. The time symmetry in this example is achieved with a tape recorder, first recording a high pass filtered signal and then playing back with time reversal to a second recorder through the high pass filter again. Real time processing is not achievable.
TL;DR: A switched gain technique is developed which allows both wall surfaces of the left ventricular posterior wall to be visualized in real time and echograms are generated with high and low gain portions closely mixed.
Abstract: Pulse-echo ultrasound, a valuable tool for noninvasive cardiac examination, has been used extensively to determine left ventricular volume and wall thickness. It is often difficult, however, to visualize simultaneously the endocardial and epicardial surfaces of the left ventricular posterior wall because of dynamic range and grey scale limitations. Although the signal reflected at the epicardial-lung interface is much stronger than the signal from surrounding myocardium and lung, it is often obliterated when the receiver gain is increased sufficiently to record the endocardial echo. We have developed a switched gain technique which allows both wall surfaces to be visualized in real time. An oscillator rapidly switches the receiver gain between two levels that are independently set to display the two wall surfaces; thus, echograms are generated with high and low gain portions closely mixed. The endocardial surface is seen best at high gain; the epicardial surface at lower amplification.
TL;DR: A technique for the localization of cytoplasmic and nucleic material in Wrights and Wrights-Giemsa strained blood cells is described, which is easy to implement either in hardware or software, and execute very rapidly in either environment.
Abstract: A technique for the localization of cytoplasmic and nucleic material in Wrights and Wrights-Giemsa strained blood cells is described. The microscopic field of view is first scanned with three different wavelengths of light and then digitized with the aid of a microscopic/vidicon/computer. Each of the three pictures is then converted to a binary color picture by comparison with three calculated clipping levels. The three binary color pictures are then logically combined to generate ``masks'' or sets of points which correspond to 1)nucleic points in the picture, 2) cytoplasmic points in the picture, and 3)red-cell points in the picture. The algorithms involved are easy to implement either in hardware or software, and execute very rapidly in either environment.
TL;DR: The variables necessary for gait evaluation are defined and two quantitative methods for their interpretation are given and the results show the applicability of the described techniques of evaluation.
Abstract: Although the functional electrical stimulation orthosis is one of the most recent approaches to the rehabilitation of hemiplegic patients, the quantitative estimate of its influence on the patients walking is not satisfactorily solved. In this communication the variables necessary for gait evaluation are defined and two quantitative methods for their interpretation are given. The second method was tested on eight hemiplegic patients. The results show the applicability of the described techniques of evaluation.
TL;DR: A commercial transducer combining a gallium arsenide infrared emitting diode and silicon phototransistor has been adapted for use as a photoelectric plethysmograph that is superior to the tungsten lamp-photoconductive cell plethYSmograph generally available.
Abstract: A commercial transducer combining a gallium arsenide infrared emitting diode and silicon phototransistor has been adapted for use as a photoelectric plethysmograph. This device is superior to the tungsten lamp-photoconductive cell plethysmograph generally available.
TL;DR: A new method of manufacturing tungsten microelectrodes with finer tip size and more reproducible exposed recording area than has been previously achieved is described.
Abstract: This communication describes a new method of manufacturing tungsten microelectrodes with finer tip size and more reproducible exposed recording area than has been previously achieved. The tips are dc electroetched to diameters below 500 A and completely covered with polymethyl methacrylate. An electron beam from a scanning electron microscope is then used to expose a precise area on the tip for later removal by chemical methods. Recording results with these electrodes suggest very good isolation properties.
TL;DR: The in vitro measurements indicate that mammalian brains exhibit very little dispersion within the frequency range of 2.25 to 3.95 GHz.
Abstract: The complex dielectric constant of human, primate, canine, ovine, and swine brain tissues at 37°C was measured in S band using a slotted waveguide section. The in vitro measurements indicate that mammalian brains exhibit very little dispersion within the frequency range of 2.25 to 3.95 GHz. The dielectric constant was found between 30 and 35 and the conductivity varied from 1.1 to 3.1 mho/m.