Showing papers in "Medical & Biological Engineering & Computing in 1967"
TL;DR: The paper traces the history of, and tabulates determinations of the electrical resistivity of blood, other body fluids, cardiac muscle, skeletal muscle, lung, kidney, liver, spleen, pancreas, nervous tissue, fat, bone, and other miscellaneous tissues.
Abstract: The paper traces the history of, and tabulates determinations of the electrical resistivity of blood, other body fluids, cardiac muscle, skeletal muscle, lung, kidney, liver, spleen, pancreas, nervous tissue, fat, bone, and other miscellaneous tissues. Where possible, the conditions of measurement are given.
1,645 citations
TL;DR: In this paper, an adaptive filter system has been developed whereby variable latency neuroelectric signals may be detected and separated from associated noise, based on correlation-averaging techniques which are described in detail.
Abstract: An adaptive filter system has been developed whereby variable latency neuroelectric signals may be detected and separated from associated noise. The system is based on correlation-averaging techniques which are described in detail. The adaptive property of the system derives from iterative correlation and averaging of the data signals and permits the recognition of signals the specific waveshapes of which are not known in advance. The system consitutes a general pattern recognition device. It has been shown to be applicable to the analysis of evoked potentials of variable latency as well as to the analysis of patterns of EEG activity. Further applications include the analysis of multiple, complex signals such as miniature potentials from single motor units in the spinal cord. The use of an adaptive filter such as this with convergence properties based on broad statistical considerations appears to have greater analytic power than have previous methods.
610 citations
TL;DR: It was found that the tendon stress-strain curve for successive cycles was reporducible provided that strain on the specimen did not exceed 2·0–4·0%.
Abstract: The mechanical behaviour of horse and human tendon, as characterised by the stress-strain curve, has been examined with respect to load-strain cycling and strain rate. It was found that the tendon stress-strain curve for successive cycles was reporducible provided that strain on the specimen did not exceed 2·0–4·0%. If this strain level was exceeded, a permanent deformation occurred. This phenomenon was verified by histological studies on strained tendon which showed that some of the collagen fibres did not return to their original orientation. Variation in the rate of strain was found to affect both the magnitude and the shape of the stress-strain curve. Additionally, it was found that the stress relaxation phenomenon for tendon was essentially the same as that found for other connective tissues.
320 citations
TL;DR: The possibility of restoring controlled movements to a paralysed arm, by means of electrical stimulation of skeletal muscle, is investigated, indicating that the method is feasible, but that more basic data is needed before an optimal control is attained.
Abstract: The possibility of restoring controlled movements to a paralysed arm, by means of electrical stimulation of skeletal muscle, is investigated. The concept is applied to the elbow joint of the human arm, by surface stimulation of the biceps and triceps muscles, in a closedloop position-control system. The results indicate that the method is feasible, but that more basic data is needed before an optimal control is attained.
92 citations
77 citations
TL;DR: The present paper discusses the practical aspects of numerical spectrum analysis of EEG data using this new procedure and includes for practical purposes a proposal for an ALGOL program of the Fast Fourier Algorithm and two illustrative examples of cross-spectral analyses are presented.
Abstract: Digital auto- and cross-spectral analysis of multichannel EEG data, although promising an important insight into the nature of the EEG generating process, has been hindered in its broader application by the prohibitive amount of computer time consumed by the classical procedures. However, the recent introduction of a high speed Fourier transform method byCooley
et al. (1965) has most favourably changed this situation. The present paper discusses the practical aspects of numerical spectrum analysis of EEG data using this new procedure and includes for practical purposes a proposal for an ALGOL program of the Fast Fourier Algorithm. In addition some important aspects of spectral windows are discussed and two illustrative examples of cross-spectral analyses are presented.
75 citations
TL;DR: The work described in this paper represents some of the first steps taken in a broad research program toward controlled electrical stimulation of muscles in human beings.
Abstract: In many forms of disability in humans due to paralysis, it appears possible to regain some measure of function through direct electrical stimulation of paralysed muscles. The work described in this paper represents some of the first steps taken in a broad research program toward controlled electrical stimulation of muscles in human beings. From an engineering point of view, it is important to characterize the muscle as an operational element. This means that the force and movement responses to input stimuli must be analysed and modeled so that effective control systems can be designed. Such analytic models must take into account physiologic factors such as metabolic capability, maintenance and regeneration of muscle tissue, and comfort and fatigue factors. Most of the data reported herein have been obtained from normal human beings. In general, comfort and pain have been used to define limits which are assumed to be equally applicable to involved persons. Initial studies have been directed to determine the nature of electrical signals which produce the maximum stimulation effects with minimum discomfort and pain. Constant current stimulation was chosen as an optimum mode. Studies were made to determine the nature and location of motor points. Plots showing isometric torque developed about the elbow as a function of stimulation frequency and intensity have been made. Single muscle twitch responses were recorded and a mathematical model derived for a single muscle twitch. Tetanic torque was predicted from single muscle twitch response. A mathematical model for a total muscle which is consistent with the concept of a summation of muscle twitches to produce tetanic contraction has been proposed.
67 citations
TL;DR: Average resistivity values of the lung were determined from measurements made on the surface of canine lungin vivo at 100 kHz, assuming the lung to be a homogeneous, isotropic, and primarily resistive medium at this frequency.
Abstract: Average resistivity values of the lung were determined from measurements made on the surface of canine lungin vivo at 100 kHz. Data were taken at various levels of expiration with several different electrode configurations on each of seven dogs. Theoretical considerations assumed the lung to be a homogeneous, isotropic, and primarily resistive medium at this frequency. The linear regression equation for resistivity as a function of lung air volume representing all data was calculated to be
$$\rho _{ave} = 705 + 1608 X$$
where ρave is in Ω-cm, andX is the level of inflation such thatX=0 for a collapsed lung andX=1 for a total of 700 cm3 of inspired air. The variation of resistivity is characterized by a standard deviation of 180 Ω-cm for the distribution of individual experimental averages about the average of all data, at one half expiration level. Comparison of the data taken with the various measurement techniques on an individual animal indicated no discrepancy.
58 citations
53 citations
TL;DR: Study of the circularity of the eburnated parts of arthritic femoral heads suggests that the process which keeps the normal femoral head spherical is well-known in production engineering, and is of such a nature that the attainment of high degrees of sphericity is not at all surprising.
Abstract: Ten femoral heads, three of them grossly pathological, have been examined to determine their shape, employing seven types of testing. We found the sagittal section of the normal femoral head to be remarkably circular, with very close concentricity of the surface of the articular cartilage and the underlying bone. The surface of the cartilage seen in the sagittal section was even more truly circular than the surface of the underlying bone. Comparing the circularity of sections in three planes the greatest deviation from true circularity was found in the section seen in the frontal plane. We found no position of the hip joint in which the femoral head protrudes from the acetabulum more than in any other, nor have our observations revealed any inherent stability of the hip joint attributable to peculiarities in the shape of the opposed surface, enabling these to lock one into the other. Study of the circularity of the eburnated parts of arthritic femoral heads suggests that the process which keeps the normal femoral head spherical is well-known in production engineering, and is of such a nature that the attainment of high degrees of sphericity is not at all surprising.
51 citations
TL;DR: A mechanical hand with automatic proportional control of prehension has been developed that requires only single switching by the amputee for opening or closing.
Abstract: A mechanical hand with automatic proportional control of prehension has been developed. Hand operation requires only single switching by the amputee for opening or closing. Once contact pressure has been made on the object, attempts to lift it result in slippage. Slippage is detected between the thumb, which contains the control sensor for automatic proportional control of grasp and the first and second fingers. This control is contained in a closed loop system incorporating the hand, motor, piezoelectric crystal, and associated electronics, and is independent of the amputee. The amputee, however, may override this system at any time, simply by activating the single opening and closing switch.
TL;DR: The model incorporates monitoring of the size of the main body-fluid compartments, and proposes that these compartment volumes are the two relevant variables used to regulate the amount of water drunk.
Abstract: The model presented is basically a servo-regulator containing an input-controlled sampling device and is intended for use as a tool in research on the control of water-intake in rats; a problem in the field of animal motivation. The model incorporates monitoring of the size of the main (extra-cellular and intra-cellular) body-fluid compartments, and proposes that these compartment volumes are the two relevant variables used to regulate the amount of water drunk. It is further argued that sodium chloride intake is controlled using information from the same receptor system. The sampling mechanism of the model accounts for competition among different motivations. Explanations of the interacting relationship between eating and drinking, and between water-intake control and renal control are also included.
TL;DR: A digital computer system has been developed to repetitively measure cardiac output on-line and derives the values for stroke volume, vascular resistance, appearance and mean circulation time of dye, central blood volume, and cardiac work.
Abstract: A digital computer system has been developed to repetitively measure cardiac output on-line. This system, which also monitors arterial pressure, heart rate, and other physiological variables, derives the values for stroke volume, vascular resistance, appearance and mean circulation time of dye, central blood volume, and cardiac work. Measurements, computation and print-out are accomplished within a 5-min period. Summary reports of these variables are generated by a typewriter. A complete set of data is recorded on punched cards for detailed analysis.
TL;DR: Some of the factors are considered upon which the presentation of intracranial tomograms by the ultrasonic pulse-echo technique depend, and the limitations imposed by these factors on the angle of scan and dynamic range of the receiver system are estimated.
Abstract: Some of the factors are considered upon which the presentation of intracranial tomograms by the ultrasonic pulse-echo technique depend. Range resolution is degraded by the increased velocity of the ultrasonic beam in the skull. Azimuth resolution is degraded by refraction when the beam does not strike the skull at normal incidence. Both range and azimuth resolution are degraded for strong reflectors when receiver sensitivity is high. The limitations imposed by these factors on the angle of scan and dynamic range of the receiver system are estimated.
TL;DR: A digital computer system has been developed for clinical use to repetivively measure intra-arterial pressure to monitor arterial pressure in over 160 patients in the Shock Research Unit of the University of Southern California at the Los Angeles County Hospital.
Abstract: A digital computer system has been developed for clinical use to repetivively measure intra-arterial pressure. Measurements are taken and reported at intervals of 5 min or more frequently. Summary reports are generated on request and a complete set of data is recorded on punched cards. The system has been used to monitor arterial pressure in over 160 patients in the Shock Research Unit of the University of Southern California at the Los Angeles County Hospital.
TL;DR: By analogue computer modelling, the method of simulation is extended to fast and slow limb muscles of the cat to illustrate the form of the muscle twitch to be expected from such mixtures, and the validity of the model and its extension to populations of motor units are discussed.
Abstract: There are differences amongst various reports of the speeds of contraction of cat intercostal muscles. By analogue computer modelling it is shown that the differences are largely resolved if the muscle consists of mixtures of two types of motor unit, fast and slow. The method of simulation is extended to fast and slow limb muscles of the cat to illustrate the form of the muscle twitch to be expected from such mixtures. The validity of the model and its extension to populations of motor units, are discussed.
TL;DR: In this article, the relationship between metal microelectrode area and amplifier input impedance required to record faithfully the action potential of frog skeletal muscle was investigated and the distortion of the EMG was quantitated in terms of the resultant per cent tilt of a square wave inserted along with the action-potential.
Abstract: The high impedance of glass micropipettes is widely recognized and appropriate attention is given to the amplifier input impedance required to reproduce bioelectric events recorded with these electrodes. However, similar precautions are often ignored when using metal microelectrodes, because it is often assumed that their impedance is much lower than micropipettes of comparable size. This paper reports on studies of the relationship between metal microelectrode area and amplifier input impedance required to record faithfully the action potential of frog skeletal muscle. The distortion of the EMG, as the amplifier input impedance was intentionally lowered in discrete steps, is quantitated in terms of the resultant per cent tilt of a square wave inserted along with the action potential. In addition, the impedance vs. frequency relationship is plotted for two metal microelectrodes of 100 and 1600 μ2 in area. This relationship shows the increased impedance at lower frequencies resulting from the capacitance produced by the electrical double layer. Results show that the minimum input impedance required for proper EMG recording ranges from 88 MΩ for steel electrodes of 500 μ2 in area to 1 megohm for electrodes of 125,000 μ2.
TL;DR: The assessment of the relative contributions of various tissues to the total impedance measured by surface electrodes in impedance pneumography is discussed.
Abstract: The impedance measured by surface electrodes in impedance pneumography is partly that of lung and partly that of other tissues, notably the skin. The paper discusses the assessment of the relative contributions of these various tissues to the total impedance.
TL;DR: If the electrode is small enough (so that its oxygen consumption is negligible compared with that of the nearby tissue), the current is proportional to the mean value over the electrode surface of the values that the oxygen tension would have taken if the potential had not been applied.
Abstract: The usefulness of the flush-ended electrode forin vivo measurements of oxygen tension in tissue has been restricted by the lack of a satisfactory theoretical or empirical relationship between the polarographic current and the oxygen tension in the tissue. It is shown here that, if the electrode is small enough (so that its oxygen consumption is negligible compared with that of the nearby tissue), the current is proportional to the mean value over the electrode surface of the values that the oxygen tension would have taken if the potential had not been applied. The proportionality factor depends on the capillary-tissue structure in the neighbourhood of the probe. However, a membrane covering the surface of the electrode can be constructed so as to eliminate this effect and so enable comparisons between the levels of oxygen tension to be made at different points in the tissue. At the same time, the loss of sensitivity to variations of oxygen tension in time can be reduced to negligible proportions. The current, in this case, is proportional to the mean undisturbed value of the oxygen tension over the surface of the membrane.
TL;DR: It is found that the cadaver skull attenuates the ultrasonic beam to a greatly varying degree and may introduce another type of false localization of echoing interfaces when receiver sensitivity is restricted.
Abstract: It is found that the cadaver skull attenuates the ultrasonic beam to a greatly varying degree. Variations in attenuation of up to 60 dB for echoes returned to the transducer may result from quite small movements of the transducer relative to the skull. Such variations in attenuation may introduce another type of false localization of echoing interfaces when receiver sensitivity is restricted.
TL;DR: The isolator output circuit should have minimum stray capacitance to ground and no conductive path to ground at all other than the path through the preparation.
Abstract: WHEN passing an electrical current through a biological preparation, either for measuring cell membrane impedance or to produce action potentials, it is often desirable to electrically isolate the stimulus source from ground. In the most obvious instance, when a bath containing a preparation is at ground potential (one side of the \" load\" at ground) a floating source is convenient in monitoring stimulus current (Fig. 1). Ideally, the isolator output circuit should have minimum stray capacitance to ground and no conductive path to ground at all other than the path through the preparation (DONALDSON, 1958). Two of the most widely accepted methods of achieving isolation have involved the use of either audioor radio-
TL;DR: An analog computer is described for measurement of the absolute value of arterial oxygen saturation from photoelectric readings taken from the ear, particularly suitable for on-line computation of the arteriallen Sauerstoffkonzentration in subjects performing various physiological activities.
Abstract: An analog computer is described for measurement of the absolute value of arterial oxygen saturation from photoelectric readings taken from the ear. The system provides a high degree of automatic compensation even for considerable changes in the ear blood volume. Therefore, in addition to its usefuness as a clinical tool, it is particularly suitable for on-line computation of the arterial oxygen concentration in subjects performing various physiological activities.
TL;DR: The equipment, which is capable of collecting measurement data from a particular scan line and/or any point within a scan line of the television image, is discussed from the standpoint of design and operation.
Abstract: Measurement instrumentation is presented that has been designed for use with the Intra-oral Television Microscope and Television Micro and Macrodensity Instrumentation. It can also be applied to any television display from other input sources. The equipment, which is capable of collecting measurement data from a particular scan line and/or any point within a scan line of the television image, is discussed from the standpoint of design and operation. Identification of the area measured, along with illuminated reference marker dots within the scan line being measured, make it possible to calibrate the instrumentation, regardless of the magnification of the televised image.