Showing papers in "Medical & Biological Engineering & Computing in 1970"
TL;DR: In this article, an integrated CO2 laser and beam manipulator designed specifically for surgical research work is descirbed, and operational characteristics of the instrument relevant to such work are reported.
Abstract: The characteristics of CO2 lasers that render them interesting for surgical applications are reviewed. An instrument consisting of an integrated CO2 laser and beam manipulator, designed specifically for surgical research work, is descirbed. Operational characteristics of the instrument relevant to such work are reported. An accessory for endoscopic surgery is described and instrumentation for microsurgery is discussed. Surgical researches now in progress with this instrument are mentioned.
126 citations
TL;DR: Rapid cleaning of infected, scarred decubitus ulcers, followed by immediate placement of free or pedicle grafts is suggested as a means for eliminating the weeks of pre-operative preparation ordinarily necessary in such cases, especially in neurosurgery.
Abstract: In preliminary studies, the carbon dioxide laser with a specially devised surgical manipulator has been shown to have a great potential for surgical application, especially in neurosurgery. It can incise nearly all tissues, bore or drill, excise and vaporize as needed. Cancers, even when ulcerated and infected, can be made to disappear by vaporization or portions of neoplasms can be excised with the laser beam. Experimental, transplantable animal tumours and one human brain tumour have already been treated with this laser. Rapid cleaning of infected, scarred decubitus ulcers, followed by immediate placement of free or pedicle grafts is suggested as a means for eliminating the weeks of pre-operative preparation ordinarily necessary in such cases. Minimal lesions can likewise be made for functional neurosurgery or for other purposes. When used in conjunction with the operating microscope control is correspondingly increased. Action by the laser is swift, gentle and easily controlled. Damage from the beam can be confined to within a millimetre of its application. Small blood vessels are readily coagulated by the CO2 laser making oozing surfaces easier to handle. The disadvantages include the inability of the CO2 laser beam to traverse any tissue, including the transparent media of the eye, without damage. Deep structures must, therefore, be surgically exposed. Ignition of flammable materials, such as drapes, and damage to personnel must be prevented but this can be done quite simply. Among the many problems which remain are those related to the total removal of cancers without causing undue damage to surrounding structures and those related to wound healing especially for skin. The problem of bleeding from large vessels needs further study. A method for controlling the vaporization of neoplasms, using radioactive monitoring of the smoke produced, is suggested.
103 citations
TL;DR: The results demonstrate that the method can be effectively used for the design of prosthetic-orthodic equipment and for the analysis of human locomotion.
Abstract: A method for the design of a dynamic biped machine is presented. Initially a minimum energy criteria is assumed. The design of a machine which satisfies this criteria follows. A conflict between this minimum energy design and stability is shown. The design of a more stable dynamic biped machine is then discussed. A set of control laws necessary for the biped's locomotion is derived. This machine is then simulated on a digital computer. The results demonstrate that the method can be effectively used for the design of prosthetic-orthodic equipment and for the analysis of human locomotion.
52 citations
50 citations
TL;DR: An on-line parameter tracking algorithm, implemented on an analogue computer, is used to obtain parameter values in an assumed mathematical relation between the full-wave rectified EMG and the force produced by the human triceps muscle in an isometric task.
Abstract: An on-line parameter tracking algorithm, implemented on an analogue computer, is used to obtain parameter values in an assumed mathematical relation between the full-wave rectified EMG and the force produced by the human triceps muscle in an isometric task. The relation between the actual force produced by human subjects and the computed force predicted by the model is discussed.
49 citations
TL;DR: Manipulations of the model and comparisons with rats indicate the necessity for short term oral and gastric feedback, and for a thirst threshold, in the regulation of body water.
Abstract: The body water, alimentary exchange, renal control, and drinking sub-systems involved in water regulation in the rat were simulated using a digital computer. For each subsystem, coefficients and time constants were fitted to published data, and the calculations closely followed a physiological understanding of the mechanisms in question. Experimental data were then obtained for the drinking and renal response to injections and continuous infusions of hypertonic saline in rats, and the overall performance of the model was tested by comparing its response to these experimental results. Agreement was good for these and other results, indicating that the model adquately takes account of the major variables in the regulation of body water. Manipulations of the model and comparisons with rats indicate the necessity for short term oral and gastric feedback, and for a thirst threshold.
41 citations
TL;DR: The most reliable method for the measurement of blood pressure is the use of catheter-type pressure gauges, despite its considerable errors associated with them, but the effect due to the reflection of the pressure wave at the tip of the catheter and at the occluding point of the artery and the increase of thepressure wave attenuation produced by the insertion of theCatheter into blood vessels is discussed.
Abstract: The most reliable method for the measurement of blood pressure is the use of catheter-type pressure gauges, despite its considerable errors associated with them. Many workers have discussed the errors of this method. No one, however, has discussed the effect due to the reflection of the pressure wave at the tip of the catheter and at the occluding point of the artery and the increase of the pressure wave attenuation produced by the insertion of the catheter into blood vessels. In this paper, the problem is discussed both theoretically and experimentally. The error due to the wave reflection is sometimes very large. To reduce this error, the diameter of the catheter must be quite small. However, if the diameter of catheter is too small, the error due to distortion of the wave during its propagation in the catheter becomes quite large. Therefore, a catheter of appropriate diameter must be used for each experiment. For example, if a catheter of 2 mm in diameter is used for an experiment on a large dog in a controlled state, the error is expected to be less than 5 per cent.
38 citations
TL;DR: The application of the mass spectrometer to the continuous monitoring of blood gases in humans is described and the system has been successfully employed in the study of arterial nitrogen washout and the determination of human cerebral blood flow by the nitrous oxide technique.
Abstract: The application of the mass spectrometer to the continuous monitoring of blood gases in humans is described. At the heart of the system is an intravascular catheter consisting of a cannula impermeable to gas tipped with a membrane whose special gas permeability characteristics permits accurate calibration. Expressions are presented which describe gas flow through the membrane in response to a step increase in gas concentration; characterize thermal effects on gas diffusion and illustrate the effect of the cannula and carrier tubing on steady state gas flow. The system has been successfully employed in the study of arterial nitrogen washout and the determination of human cerebral blood flow by the nitrous oxide technique.
32 citations
TL;DR: It was shown that after strong muscular work there is a relative increase of the high frequency components in the spectrum in relation to thehigh frequency decay that is known to occur during contraction.
Abstract: A method for frequency analysis of the EMG is described. The analyser uses four octave band filters with the centre-frequencies 50, 200, 800 and 1600 Hz, and feeds a four channel integration unit. The output from a number of measurement points, semi-randomly selected in the muscle, is processed by a digital computer together with suitable calibration values into a form suitable for data reduction and judgement. The method has greatly increased the possibilities of inter- and intra-subject comparisons. This is exemplified by an experimental series showing the spectra before and after muscular work. It was shown that after strong muscular work there is a relative increase of the high frequency components in the spectrum. This has been discussed in relation to the high frequency decay that is known to occur during contraction.
30 citations
TL;DR: A list of factors which may influence the result of strength tests on bone is given and discussed and it is suggested that by careful consideration of these factors and by standardization of the variables among them, the scatter of results could be reduced.
Abstract: Some of the more recent studies into the compressive and tensile strengths of small human bone samples are discussed. The scatter of results is compared to that for tests on cement which, like bone, is a composite material. A list of factors which may influence the result of strength tests on bone is given and discussed. It is suggested that by careful consideration of these factors and by standardization of the variables among them, the scatter of results could be reduced.
28 citations
TL;DR: Evaluation of the electrodes shows good appearance, good mechanical stability, excellent ability of picking up bioelectrical signals and low interface impedance between electrode and tissue, and Histological examination shows growth of epidermis around the electrode.
Abstract: Solid percutaneous electrodes made of vitreous carbon were inserted surgically in the forearm of human subjects. The electrodes were left in the arm for several months without any particular care or protection.
TL;DR: To diminish the pulse distortion in the high-pass and low-pass filter of the output stage, the filter elements were placed in the feed-back loop of an amplifier with high closed loop gain.
Abstract: Action potentials of sensory nerve evoked by stimuli of 70 mA may be as small as 0·05 μV. They are buried in noise and require electronic averaging. The signal-to-noise ratio can be improved by the use of an input transformer and by limiting the frequency range (Buchthal andRosenfalck, 1966). When recording near the point of stimulation the amplitude of the artefact exceeds that of the sensory potential by a factor of 104 and prevents its recording because of the pulse distortion caused by the limited frequency range. This was diminished by decreasing the lower limiting frequency of the input transformer by means of positive feedback. To diminish the pulse distortion in the high-pass and low-pass filter of the output stage, the filter elements were placed in the feed-back loop of an amplifier with high closed loop gain. The small tail of the stimulus artefact arising mainly from the transmission through the isolating transformer in the output of the stimulator was reduced by compensation with a pulse of the same shape and amplitude but of opposite sign.
TL;DR: The development of new types of prostheses would be furthered by accurate reproduction of loading and lubricating conditions by using an accurate joint simulating machine for the study of artificial lubricants.
Abstract: Total joint replacement by prosthesis in the hip is being increasingly practised (e.g. Charnley, Stanmore, McKee-Farrar, Ring), and to a lesser extent in the knee (Walldius, Shiers). The mechanical strength, friction and wear properties of the materials used in such prostheses are of the greatest importance. Standardised engineering test equipment such as pin-on-disc machines will give a certain amount of information, but they cannot simulate the widely fluctuating loads to which the joint is subjected in physiological conditions. Some joint simulating machines have been described (Duff-Barclay andSpillman, 1967), but there are in-adequacies in these machines such as an unsatisfactory sequence or lack of provision of any self centring device for a joint in motion. For these reasons an accurate joint simulating machine is necessary.
TL;DR: Equipment is described which may be attached to a standard hospital bed for the measurement of motility which proved reliable and easy to use and weight change was found to be an important factor influencing motility scores.
Abstract: The measurement of nocturnal motility as an index of sleep is discussed. Equipment is described which may be attached to a standard hospital bed for the measurement of motility. The apparatus proved reliable and easy to use. Weight change, common in psychiatric practice, was found to be an important factor influencing motility scores. Calibration of the bed for subject weight enabled a factor to be calculated which corrects the motility scores for changes and differences in weight.
TL;DR: A new family of myo-electric control equipment is described, with an example of its application to a forequarter amputee and modular design, flexibility of function, reduced size and weight and improved packaging characterize this new equipment.
Abstract: A new family of myo-electric control equipment is described, with an example of its application to a forequarter amputee. Modular design, flexibility of function, reduced size and weight and improved packaging characterize this new equipment.
TL;DR: A heart ratemeter operating over a range of 30–900 beats per minute has been designed, which is triggered from any measured cardiac variable to produce a linear d.c. beat-by-beat readout.
Abstract: A heart ratemeter operating over a range of 30–900 beats per minute has been designed. The device is triggered from any measured cardiac variable to produce a linear d.c. beat-by-beat readout. The cardiac frequency is found by a true reciprocal computing process provided by a variable-slope ramp generator operating on the period between beats. This computer, and other circuitry within the ratemeter, uses low-cost operational amplifiers to simplify the design and construction.
TL;DR: A simple model for the extracellular action potential of a single muscle fibre in situ is proposed, a dipole moving at a uniform speed in an axial direction, immersed in a volume conductor of extent large compared with the dipole length.
Abstract: A simple model for the extracellular action potential of a single muscle fibrein situ is proposed. This model is a dipole moving at a uniform speed in an axial direction, immersed in a volume conductor of extent large compared with the dipole length. The peak to peak duration of the potential recorded by a small electrode increases with distance of the electrode from the site of maximum amplitude. The model can be applied to show why the measured duration of the action potential of a motor unit is necessarily longer than that of the constituent single fibre.
TL;DR: The electronic circuitry and mechanics of an apparatus capable of collecting any given percentage of bile while simultaneously returning the remainder to the experimental animal is described in detail.
Abstract: The electronic circuitry and mechanics of an apparatus capable of collecting any given percentage of bile while simultaneously returning the remainder to the experimental animal is described in detail. The importance of this apparatus in studying the enterohepatic circulation of bile in the intact animal is discussed.
TL;DR: The modulus of elasticity of each specimen was calculated following its observed resonance using the small-deflection linear beam theory, the degree of validity of which was shown by finding the ratio of frequencies of the consecutive modes and the position of the nodes.
Abstract: Specimens of bone cut from tibiae of older beef cattle have been subjected to sinusoidal vibration in flexural and longitudinal modes. From the known dimensions and density of the specimens the modulus of elasticity of each specimen was calculated following its observed resonance. The calculation was based on the small-deflection linear beam theory, the degree of validity of which was shown by finding the ratio of frequencies of the consecutive modes and the position of the nodes. A mean value of the modulus of 3·4×106 lbf/in2(23·4×109 N/m2) was obtained for the 10 specimens tested.
TL;DR: An electronic cell detector which provides good cell volume distribution is described and a device for selecting transit times has been incorporated, whereby a measurement of only the cells within the central axis of the aperture is recorded.
Abstract: An electronic cell detector which provides good cell volume distribution is described. Consideration has been given to bandwidth and input noise with respect to aperture size and resistance. The instrument uses a low noise current pre-amplifier, and switched upper and lower bandwidth providing an overall response time of 5 μsec. It produces a shaped output pulse suitable for most pulse height analyzers and also records the total cell count and time taken for a given volume measurement, which provides an instant check if the aperture becomes partially blocked.
TL;DR: A method of passing EMG's through a summing amplifier and then quantifying the output for the evaluation of total muscular activity was developed, which greatly reduces the system components normally necessary for such studies.
Abstract: In the present investigation a method of quantifying electromyograms (EMG's) from different muscle groups of the body to evaluate total muscular activity is described.
TL;DR: In this article, the performance of miniature silicon diaphragm pressure transducers is discussed with respect to the measurement of pressure inside the cranial cavity and a modification to the basic unit is described which allows the baseline pressure reading and pressure calibration to be checked at any time throughout the period of implantation.
Abstract: The performance of miniature silicon diaphragm pressure transducers is discussed with respect to the measurement of pressure inside the cranial cavity. A modification to the basic unit is described which allows the baseline pressure reading and pressure calibration to be checked at any time throughout the period of implantation. There has been no discernable reaction to the presence of the devices inside the cranial cavity and it has been possible to obtain continuous recordings of intracranial pressure for as long as 7 days without complications.
TL;DR: It is shown both theoretically and experimentally, that the change in the capacitance between the surface of the segment and an encircling flexible screen cuff at a fixed distance from the skin is related to the fractional change in volume of the part by a simple constant which can be determined from the initial capacitance.
Abstract: An improved capacitance system for blood flow measurement by venous occlusion plethysmography is described. It is shown both theoretically and experimentally, that the change in the capacitance between the surface of the segment and an encircling flexible screen cuff at a fixed distance from the skin is related to the fractional change in volume of the part by a simple constant which can be determined from the initial capacitance. Thus, neither calibration nor measurement of segment volume is needed.
TL;DR: It is pointed out that absorption in biological materials modifies the effective distribution in clinical practice as well as the directivity of the probe depends upon its construction.
Abstract: The applications of ultrasonic Doppler techniques in medical diagnosis are reviewed. The directivities of ultrasonic probes may be measured by observation of the echo amplitudes from various target configurations, and with long ultrasonic pulses. Instrumentation operating at a frequency of 2 MHz is described. Measurements of the directivities of several transducer arrangements for both spherical and flat targets are presented, and some of the results are compared with theoretical predictions. The directivity of the probe depends upon its construction. In general, with separate transmitting and receiving transducers, there is a region of maximum central axial sensitivity (in water) which is closer to the array than the cross-over point of the beams. It is pointed out that absorption in biological materials modifies the effective distribution in clinical practice. Off-axis measurements, and the effects of target angulation, are presented in selected cases. Methods based on Schlieren observations and the use of moving targets for beam plotting are also discussed.
TL;DR: The thickness of the pulsatile laminar boundary layer is found to be approximately one millimeter for conditions in the vicinity of the heart, and for separation and turbulence differ from those in steady flow.
Abstract: Potential flows of the form ϕ=(ax2+by2+cz2)f(t) may be utilized to represent motions produced in pulsating bulbs. While the initial bulb shape may be arbitrary, sequential shapes are related by affine transformations. Two components appear in the distribution of pressure, one dependent on the instantaneous velocity and the other on the acceleration. For flows with stationary streamlines the inertial impedance is that of a simple mass, and is proportional to the first moment of the actual mass of fluid contained within the bulb. Examples treated are: (1) expanding and collapsing circular cylinders and (2) elliptical cylinders in which the perimeter is held constant.
TL;DR: A mathematical model of some of the circulatory properties of the heart is described and it is demonstrated how information about the volume of the ventricle can be retrieved from dye dilution curves using the value of the volume flow rate, the time for maximum dye concentration to appear at the sampling site, and the mean transit time of the dye.
Abstract: This paper describes a mathematical model of some of the circulatory properties of the heart, and it is demonstrated how information about the volume of the ventricle can be retrieved from dye dilution curves using the value of the volume flow rate, the time for maximum dye concentration to appear at the sampling site, and the mean transit time of the dye. A nomograph has been developed in order to eliminate the need for mathematical calculations. The validity of the model described is assessed in seven dog experiments by comparing results obtained using the dye dilution technique with results from cineangiocardiographic films taken almost simultaneously of dispersed radiographic contrast fluid. The flow measurements have been checked using a new method employing a suspension of radio-opaque particles.
TL;DR: A new member of the family of POD catheters which has been found useful for selective examination of the bronchial tree is developed and has been used to deliver contrast material for selective bronchography and the removal of excess contrast material.
Abstract: We have developed a new member of the family of POD catheters which has been found useful for selective examination of the bronchial tree This flexible magnetic catheter is controlled with external hand held permanent magnets It has been used to deliver contrast material for selective bronchography and the removal of excess contrast material The device has application to the recovery of saline washed bacteriological and cytological specimens, for guiding endobronchial biopsy devices to suspected lesions and to selectively deliver medication to disease sites
TL;DR: A new synthetic membrane presently under clinical evaluation at Strathclyde shows much higher UFR for any applied pressure compared with cellulose films under the same conditions, and a different water transport mechanism is evident from the resulting curves which are obtained by plotting “Permane” UFR against applied pressure.
Abstract: Ultrafiltration rates (UFR) have been measured for different membranes in a modified dialysis test cell under a range of positive pressures from 50 to 300 Torr. The test cell interior is filled with 200 ml distilled water and water escape rate is measured through one 5·1 cm diameter disc. A linear relationship between UFR and applied pressure exists for cellulose materials and experimental results confirm those of previous workers. A new synthetic membrane presently under clinical evaluation at Strathclyde (Series 10 or “Permane”) shows much higher UFR for any applied pressure compared with cellulose films under the same conditions. A different water transport mechanism is evident from the resulting curves which are obtained by plotting “Permane” UFR against applied pressure. Several methods exist for controlling “Permane” UFR.