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PubMed1980

Quantitative study of the rabbit aortic endothelium using vascular casts.

A quantitative study of the en face size and shape of rabbit endothelial cells from the ventral mid-thoracic and ventral infrarenal abdominal aorta has been carried out in 6 rabbits. Photomicrographs were taken from vascular casts of the rabbit aorta and the endothelial cell outlines were analyzed quantitatively using a digitizer and digital computer. The morphology of the endothelial cells was described using 8 calculated parameters (area, perimeter, length, width, angle of orientation, width:length ratio, axis intersection ratio and shape index). The endothelial cells in both locations had the same surface area (P greater than 0.30); however, the cells in the abdominal aorta were longer (P less than 0.01) and narrower (P less than 0.01) than those in the thoracic aorta. This fact is reflected by the smaller value for the shape index and width : length ratio in the abdominal aorta (P less than 0.01). Cells in both the thoracic and abdominal aorta were aligned with the flow direction.

Animals↗
PubMed1982

Calibration and performance of a 3-dimensional television system for kinematic analysis.

A three-dimensional television system for kinematic analysis has been developed using television cameras connected to a digital computer. Reflective markers on the limbs of the subject are illuminated by stroboscopes, and show up as bright spots in the television image. A television/computer interface generates the two-dimensional coordinates of these spots, and stores them on disk for later analysis. A three-dimensional calibration procedure has been developed which requires an initial survey to be made of the measurement area, but thereafter takes only a few minutes to perform on a day-to-day basis. The television system has been in routine use for over a year, and it has proved rapid, reliable and easy to use, both for purely kinematic studies, and together with a pair of forceplates for combined kinetic/kinematic studies.

Biomechanical Phenomena↗
PubMed1983

A new approach to the human muscle model.

Hill's (1938) two component muscle model is used as basis for digital computer simulation of human muscular contraction by means of an iterative process. The contractile (CC) and series elastic (SEC) components are lumped components of structures which produce and transmit torque to the external environment. The CC is described in angular terms along four dimensions as a series of non-planar torque-angle-angular velocity surfaces stacked on top of each other, each surface being appropriate to a given level of muscular activation. The SEC is described similarly along dimensions of torque, angular stretch, overall muscle angular displacement and activation. The iterative process introduces negligible error and allows the mechanical outcome of a variety of normal muscular contractions to be evaluated parsimoniously. The model allows analysis of many aspects of muscle behaviour as well as optimization studies. Definition of relevant relations should also allow reproduction and prediction of the outcome of contractions in individuals.

Computers↗
PubMed1983

Comparative evaluation of techniques for the harmonic analysis of human motion data.

Four mathematical techniques for the estimation of the Fourier coefficients of pseudoperiodic non-exact discrete functions were submitted to comparative evaluation. These techniques were devised within the following basic procedures: (1) numerical harmonic analysis applied either directly or after redistribution of the data points through some interpolation procedure, so that they be evenly spaced in time and exactly fit on cycle period; (2) fitting of the empirical data with an analytical model followed by the calculation of the Fourier integrals of this model. The evaluation was carried out with special reference to the use of these techniques for processing human motion photogrammetric data. The following criteria were used: (1) accuracy of the Fourier coefficient estimates, (2) capability of yielding information about this accuracy, (3) a priori information needed regarding the statistical properties of the experimental error, (4) factors concerning implementation in digital computers. Practical information was obtained for the non-specialist user with regard to the choice of one technique among the several possible in particular circumstances.

Fourier Analysis↗
PubMed1988

A dynamic model for finger interphalangeal coordination.

In this paper a dynamic model to investigate interphalangeal coordination in the human finger is proposed. Suitable models which describe the relationship between the tendon displacement and the joint angles have been chosen and incorporated into the skeletal dynamic model. A kinematic and kinetic model for interphalangeal coordination is suggested. Digital computer simulations are carried out to study interphalangeal (IP) flexion. Moreover, the effect of two different optimization methods is contrasted. The two optimization algorithms are employed to obtain a set of feasible values for the forces in the tendons or muscles of the finger.

Biomechanical Phenomena↗
PubMed1994

Hydrodynamic simulation of arterial networks which include compliant and rigid bypass grafts.

The conditions required to produce an ideal bypass graft have not yet been determined. In order to understand the hemodynamic impact of bypass grafts on cardiovascular function, a hydrodynamic model for the part of the human arterial network below the renal arteries has been constructed. The results from this physical model were used to validate a digital computer model of the arterial network developed by the authors, that incorporated loops which occur due to bypass grafts. The hydrodynamic model was designed to study the interaction between an arterial stenosis and bypass graft and, in particular, the effect of the compliance of the graft on their function. In the model, similarity laws have been maintained with regard to geometry, viscosity, peripheral resistance, wall elastic properties, pulse shape, and blood flow rate. Measured and predicted pressure and flow wave-forms showed an increase in their mean and peak values for the healthy leg when the bypass graft was closed. There was also a severe pressure drop across the stenosis and a marked decrease in mean and pulsatile flow in the stenotic leg. The stenosis in the hydrodynamic model produced similar behaviour to published results obtained on animals. When the graft was open, the agreement between our experimental and theoretical model was within 5% and both the pressure and flow waves were almost similar at the maxima and minima in both legs. Although the arterial system is non-linear, the non-linearities are shown to be of insignificant magnitude and therefore, we have concluded that the pressure flow relationship is essentially linear. The effect of the degree of compliance of the graft and the 'steal' phenomenon due to the graft have been investigated. It was found that there were no significant differences in the flow delivery between the compliant graft and stiff graft. Also, there was no 'steal'. Thus the compliance of the graft is not a significant factor in promoting its patency.

Arteries↗
PubMed1979

A semi-automatic method of measuring leucocyte movement.

A semi-automatic system has been developed for measuring the migration of leucocytes within a micropore filter. The distance in micrometers is displayed digitally or analysed on-line by a digital computer. These improvements have resulted in considerable saving in time, permitting the full potential of the micropore method to be utilised. To illustrate this technique we report results from experiments to measure dose-response relationships of leucocytes to casein and the variation in response to Staphylococcus aureus and casein of cells from normal human subjects.

Caseins↗
PubMed1989

Quantitative and subjective analysis of temporomandibular joint radiographs.

The lateral oblique transcranial radiograph of the temporomandibular joint is commonly used in dentistry. Changes in horizontal angulation of the x-ray beam can produce changes in radiographic condylar position. This study used quantitative and subjective methods to assess and rank changes in radiographic condylar position as a function of known horizontal x-ray beam changes. Six dry skulls were positioned in a craniostat device where known angulations could be measured. Nine sequential transcranial temporomandibular joint radiographs were made of each joint and five of these 12 sets were randomly selected for analyses. The quantitative method involved film digitization, computer calculations, and expressed condylar position as a ratio between posterior and anterior joint space distributions. Eight observers viewed the same films and ranked radiographic condylar position from anterior to posterior. The two methods agreed with known rankings 81.8% of the time. Subjective rankings were more variable than quantitative rankings. Intraobserver differences were insignificant and the observers were consistent among themselves as a group.

Cephalometry↗
PubMed1981

A new method for image layer analysis in rotational panoramic radiography.

The position and form of the image layer in rotational panoramic radiography vary from one manufacture to another. A method utilizing a digital computer to calculate the position, form, and relative thickness of the image layer from data obtained from two test radiographs is described. The image layer analysis permits the performance of different rotational panoramic radiographic units to be compared independent of various parameters such as beam width and magnification. The image layers for several commercially available units are illustrated.

Computers↗
PubMed1996

The naturally occurring accommodative response of the oscar, Astronotus ocellatus, to visual stimuli.

Observation of the naturally-occurring accommodative response of a highly visual teleost species provides the opportunity to study its stimulus-response accuracy. A video recording system, linked to a computer digitizing program, was used to measure accommodative changes in lens position in the oscar, Astronotus ocellatus, in response to known food stimuli. The largest lens deviations occurred along an axis c. 22 deg from the pupillary plane. Consistent underaccommodation was reported for the closest of targets, a finding reminiscent of accommodative lag reported in human studies.

Accommodation, Ocular↗
PubMed1983

Subtemporal decompressions for shunt-dependent ventricles: mechanism of action.

The literature suggests that subtemporal decompression is an effective treatment for the syndrome of shunt-dependent ventricles because it allows the ventricle to enlarge around the shunt catheter tip. Pre- and post craniectomy ventricular areas were measured from computed tomography scans with a computer digitizing technique in three patients with this syndrome who had undergone four surgical procedures. All patients improved symptomatically following craniectomy. A significant decrease in total ventricular area was noted in all instances. The results suggest that subtemporal craniectomy causes the ventricles to become smaller, not larger. Other possible explanations for the effectiveness of the procedure are discussed.

Cerebrospinal Fluid Shunts↗
PubMed1980

Radioisotope angiography in diagnosis of varicocele.

A varicocele, the most common surgically correctable cause of subfertility in men, is a manifestation of abnormal retrograde venous blood flow through the internal spermatic vein into the peritesticular pampiniform plexus. Methods of diagnosing the varicocele, including careful physical examination using a Valsalva maneuver as well as a Doppler stethoscope, remain somewhat subjective. Venography, while a reliable and objective technique, is invasive and not without morbidity. In the present study, 16 patients with clinically detectable varicoceles of various sizes were studied using a testicular radioisotope angiogram developed in our laboratory. Following the injection of 15 mg. of stannous pyrophosphate which results in tagging of the circulating red cell pool, 20 mCi. of 99m-technetium were administered in an intravenous bolus injection. The isotope binds to the pyrophosphate thus tagging the red blood cells and creating a blood-pooling agent with a relatively short half-life (six hours). Perfusion studies as well as static views of the scrotal contents, both in the supine and erect position, with and without Valsalva maneuver, were obtained using a gamma camera. The activity in each hemiscrotum then was quantitated using a digital computer. It is proposed that quantitation of this differential blood pool will make the identification of even subclinical varicoceles a potentially objective determination.

Humans↗
PubMedDate not supplied

Quantitative electrocardiography during extended space flight.

To assess the effects of prolonged space flight on the electrophysiological properties of the heart, vectorcardiograms (VCG) were obtained on the Skylab crews at regular intervals during flight and the pre- and postflight periods. The VCG signals were telemetered from Skylab and analyzed by digital computer. Conventional 12-lead electrocardiograms were derived from the VCG signals by a lead transformation program. Standardized exercise loads were incorporated into the experiment protocol to increase the sensitivity of the VCG for effects of deconditioning and to detect susceptibility for arrhythmias. In Skylab II, 24 preflight, 21 inflight, and 19 postflight experiments were analyzed. Statistically significant inflight changes observed in two or more crew members included: decreased resting heart rate, increased QRS duration, anterior shift QRS vector, increased QRS vector magnitude, anterior shift T vector, and increased T vector magnitude. One astronaut had occasional premature ventricular contractions (PVC) during the pre- and postflight phases. He had a single episode of multiple PVC's during heavy-load exercise testing in flight. A second astronaut had no arrhythmia during pre- or inflight testing. On postflight day 21 he had multiple PVC's and salvos of ectopic ventricular beats. He has had no recurrence of the arrhythmia. With the exception of the cardiac arrhythmias, no deleterious electrophysiological changes were observed during Skylab II.

Arrhythmias, Cardiac↗
PubMed1983

Outdoor bicycle for exercise in paraplegics and quadriplegics.

The design of a three-wheel bicycle is described which can be used for exercise and locomotion in paraplegic and quadriplegic subjects. This device is constructed from a standard three-wheel bicycle which has been modified with a sensor to show the position of the pedals. The output of the sensor (a 360 degrees potentiometer) is read by the A/D converter of a small digital computer carried on the bicycle. The microprocessor system controls stimulation to four key muscle groups to allow locomotion. The speed of the bicycle is controlled with a throttle control as on a motorcycle. The device offers a potentially attractive system for increasing muscle strength and endurance, reducing muscle atrophy, increasing bone density and cardiovascular training in wheelchair bound patients.

Bicycling↗
PubMed1990

Automated three-dimensional finite element modelling of bone: a new method.

Three-dimensional finite element stress analysis of bone is a key to understanding bone remodelling, assessing fracture risk, and designing prostheses; however, the cost and complexity of predicting the stress field in bone with accuracy has precluded the routine use of this method. A new, automated method of generating patient-specific three-dimensional finite element models of bone is presented--it uses digital computed tomographic (CT) scan data to drive the geometry of the bone and to estimate its inhomogeneous material properties. Cubic elements of a user-specified size are automatically defined and then individually assigned the CT scan-derived material properties. The method is demonstrated by predicting the stress, stain, and strain energy in a human proximal femur in vivo. Three-dimensional loading conditions corresponding to the stance phase of gait were taken from the literature and applied to the model. Maximum principal compressive stresses of 8-23 MPa were computed for the medial femoral neck. Automated generation of additional finite element models with larger numbers of elements was used to verify convergence in strain energy.

Adult↗
PubMed1987

An iterative method for the deconvolution of microcalorimeter thermograms.

An iterative method for the deconvolution of microcalorimetry thermograms suitable for small digital computers is presented. The method employs a measured impulse response function directly as the deconvolution kernel, thus explicit system simulation is not required. Data are presented showing the performance of the method and the exchange of signal-to-noise ratio for time resolution that is made when deconvolution techniques are employed. An improvement in the system time resolution of fifty times is demonstrated with measured data.

Algorithms↗
PubMed1981

Single electrode voltage clamp by iteration.

A technique for providing conditions of voltage clamp which differs considerably from other voltage clamp schemes has been developed. The feedback network which determines the current which will clamp the cell to the desired voltage does not operate in real time. Instead, the system uses a form of discontinuous feedback. The event to be clamped, which must be one which can be made to repeat itself without change, is elicited and allowed to run to completion without the intervention of feedback. During each repetition of the event, a current waveform is injected whose shape is based on the foregoing trials (iterations). Successive repetitions of this process develop a current waveform which ever more closely clamps the voltage to the desired value. Implementation involves a means of converting the intracellular voltage signal to digital form (a transient recorder), a means of processing the digitalized voltage signal (a digital computer), and a means of delivering the clamping current back to the preparation. The system has two advantages over other voltage clamp techniques. First, that the feedback loop is open in real time confers great stability. This advantage is exploited in the use of iterative voltage clamp in single electrode preparations. Secondly, iterative voltage clamp is essentially unlimited in the speed with which it can respond to transients. This would make the technique of interest even in preparations such as squid giant axon, where two electrodes are used and very fast responsiveness is desired.

Animals↗
PubMed1987

A device for spike train sampling with built-in memory.

The described interface to a digital computer measures interspike interval durations with a resolution of 10 microseconds. A built-in first-in first-out (FIFO) memory relieves the host computer from frequent I/O intensive tasks. The internal FIFO buffer can store up to 512 data words (wordlength is 16 bit) and works on the dual-port principle. This way the acquisition of a neuronal spike train is completely independent of the computer's simultaneously ongoing data access. A simple handshake protocol between the interface and the computer prevents any overhead communication. The buffer architecture of the instrument releases the host computer from high speed I/O handling schemes like real-time, clock-controlled, polling or interrupt procedures, that would request assembly language support. The body of two software, driver routines in the BASIC and the PASCAL language is presented. A complete and detailed schematic diagram of the circuitry is included.

Computer Literacy↗