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PubMed2001

An investigation of how acute muscle pain modulates performance during computer work with digitizer and puck.

The purpose was to investigate the influence of muscle pain on work performance during computer work with digitizer and puck. Muscle pain was induced by infusion of hypertonic saline in the trapezius and the extensor carpi ulnaris (ECU) muscles on two separate days. Twelve healthy subjects participated. A computer task was performed in three 6 min sessions: baseline, pain, after pain. The computer task comprised production of drawings at maximal work pace. One drawing was defined as a work cycle. Work cycle time, number of puck button clicks, and screen pixels the cursor had moved per cycle were assessed. Shoulder pain did not influence these variables. Cycle time decreased from 13.8 (SD 2.2) to 13.0 s (SD 1.9) compared to baseline (p < 0.05) during ECU muscle pain. The increased or unchanged performance suggests that acute moderate muscle pain has minor influence on performance during computer work with digitizer and puck.

Adult↗

PubMed1985

A Pascal computer program for digitizing lateral cephalometric radiographs.

The authors describe a new program for cephalometric analysis which uses a commonly available microprocessor (computer) and digitizing pad to register fifteen commonly identified cephalometric landmarks to produce a meaningful analysis which is printed out for permanent or hard-copy record. Conventional and digitizing errors of cephalometric measurement are reviewed, with a discussion of the advantages of computer-assisted programs. The authors describe a program that uses vectors and vector algebra and the capabilities of the Pascal computer language to determine angular measurements and distances. It is suggested that computer-assisted cephalometric programs will likely be widely used in the near future, providing the orthodontist with a superior method of cephalometric analysis with respect to accuracy and speed of completion.

Cephalometry↗

PubMed1962

Some formal approaches to the analysis of kinetic data in terms of linear compartmental systems.

A formal approach to the routine analysis of kinetic data in terms of linear compartmental systems is presented. The methods of analysis are general in that they include much of the theory in common use, such as direct solution of differential equations, integral equations, transfer functions, fitting of data to sums of exponentials, matrix solutions, etc. The key to the formalism presented lies in the fact that a basic operational unit-called "compartment"-has been defined, in terms of which physical and mathematical models as well as input and output functions can be expressed. Additional features for calculating linear combinations of functions and for setting linear dependence relations between parameters add to the versatility of this method. The actual computations for the values of model parameters to yield a least squares fit of the data are performed on a digital computer. A general computer program was developed that permits the routine fitting of data and the evolution of models.

Biophysical Phenomena↗

PubMed1980

A distributed computer network using microcomputers for on-line data processing in clinical monitoring and medical research.

Microelectronic technology has made possible a rapid expansion in the exploitation of the digital computer in medicine, but software development remains an increasingly significant problem. This paper describes a distributed computer network which combines the low cost computing power of the microcomputer with the highly developed features of a minicomputer. Powerful data processing facilities are provided through centralization of major resources on the minicomputer. Parallel real-time computing is assigned to microcomputers which have access to the minicomputer filestore, and to its comprehensive software development aids.

Animals↗

PubMed1982

A simulation study of motion artefacts in computed tomography.

In order to increase understanding of artefacts caused by patient motion in computed tomography, rigid translational and rotational motions in the plane of reconstruction have been considered. Motion artefacts were simulated on a digital computer and demonstrated in actual CT scans of a phantom. The types of motion artefacts observed included streaking, boundary splitting and subtle distortions of shape. A method for removing artefacts from a CT image without rescanning the patient is discussed, and some examples of possible improvement are shown using the simulation model. It is assumed that perfect knowledge of patient motion is known since this represents the theoretical limit on possible improvement to the degraded image. A qualitative discussion of streaking, the most common type of motion artefact, is also included.

Humans↗

PubMed1976

Method for the analysis of the entrainment between heart rate and ventilation rate.

A digital computer program was developed which allows to continuously represent the relation between heart rate and ventilation rate. Using this program, experiments in anesthetized rabbits were performed. We found periods of synchronization, periods of transient entrainment and escape, and periods of complete desynchronization. By testing the respective roles for the entrainment mechanism of ventilation rate and heart rate it was found that spontaneous adjustments of the ventilation rate play a more pronounced role. Thus, as soon as spontaneous or induced variations of the heart rate and/or the ventilation rate shift both rhythms close to synchronization, variations of the ventilation pattern, which seem to be of reflex nature, tend to induce entrainment.

Analog-Digital Conversion↗

PubMed2005

A technique to detect and to quantify fasciocutaneous blood vessels in small laboratory animals ex vivo.

PURPOSE: A microangiographical technique is described, which allows visualization of small and capillary blood vessels and quantification of fasciocutaneous blood vessels by means of digital computer analysis in very small laboratory animals. MATERIALS AND METHODS: The left carotid artery of 20 nu/nu mice was cannulated (26 gauge) and a mixture of gelatin, bariumsulfate, and green ink was injected according to standardized protocol. Fasciocutaneous blood vessels were visualized by digital mammography and analyzed for vessel length and vessel surface area as standardized units [SU] by computer program. RESULTS: With the described microangiography method, fasciocutaneous blood vessels down to capillary size level can be clearly visualized. Regions of interest (ROIs) can be defined and the containing vascular network quantified. Comparable results may be obtained by calculating the microvascular area index (MAI) and the microvascular length index (MLI), related to the ROIs size. Identical ROIs showed a high reproducibility for measured [SU] < 0.01 +/- 0.0012%. CONCLUSION: Combining microsurgical techniques, pharmacological knowledge, and modern digital image technology, we were able to visualize small and capillary blood vessels even in small laboratory animals. By using our own computer analytical program, quantification of vessels was reliable, highly reproducible, and fast.

Angiography↗

PubMed1989

[Differential diagnostic signs of metastases to the mediastinal lymph nodes in rats with a transplanted Walker tumor].

Density of contrast-free and contrasted mediastinal lymph nodes was studied in simulated chronic pneumonia and lung cancer using the DED-3 type digital computer in combination with the REIS-D X-ray source. Direct high (over 80 times) X-ray magnification may be used to measure lymph node density using digital print-out. This, in turn, may be employed for mathematical analysis and development of differential algorithm for computer. In cases of involvement, the higher mean density of contrast-free lymph nodes was matched by the lower one in contrasted lymph nodes, as compared with normal lymph nodes and those in chronic inflammation. Different values of lymph node tissue heterogeneity (A) and that of mean density of lymph nodes (B3) may be used to find differential algorithm for computer diagnosis of metastasis.

Animals↗

PubMed1996

Angiographic and electron-beam computed tomography studies of retrograde cardioplegia via the coronary sinus.

Retroperfusion of the coronary sinus does not provide homogeneous distribution of cardioplegic solution. The goal of this study was to analyze the distribution of flow during retrograde cardioplegic infusion in cadaveric human hearts with two different techniques of coronary sinus cannulation: (1) internal occlusion of the coronary sinus by balloon inflation and (2) external occlusion by tightening the orifice of the coronary sinus around a simple catheter. To evaluate differences between the two techniques, angiographic and electron-beam computed tomographic studies were performed. Computed digital angiography was performed on 14 hearts. Angiographic patterns varied according to type of coronary sinus cannulation. With the balloon inflation technique, the marginal vein and the anterior descending vein were perfused first; the posterior descending vein was not perfused. This vein was opacified secondarily through a venovenous anastomosis located at the apex of the heart. Backward flow into the right atrium (steal phenomenon) was demonstrated. At completion of retroperfusion, the inferior part of the septum remained poorly opacified. Conversely, angiographic findings after external occlusion of the coronary sinus revealed simultaneous injection of all venous channels. The entire septum was well opacified at completion of retroperfusion. Electron-beam computed tomographic study was performed on eight hearts with the external occlusion technique and nine with the internal occlusion technique. The computed tomographic findings confirmed the results of digital angiography. The peak myocardial enhancement and the peak rising rate of myocardial enhancement within the interventricular septum were significantly more important (p < 0.0001) when the external coronary sinus occlusion mode was used than when the internal coronary sinus occlusion mode was used. In all hearts except one, the right ventricular wall was not opacified, regardless of the type of cannulation and the type of radiologic analysis. This study demonstrates the importance of coronary sinus cannulation technique in optimizing the protection of the interventricular septum with retrograde cardioplegic infusion.

Adult↗

PubMed2005

Fermi-Pasta-Ulam, solitons and the fabric of nonlinear and computational science: history, synergetics, and visiometrics.

This paper is mostly a history of the early years of nonlinear and computational physics and mathematics. I trace how the counterintuitive result of near-recurrence to an initial condition in the first scientific digital computer simulation led to the discovery of the soliton in a later computer simulation. The 1955 report by Fermi, Pasta, and Ulam (FPU) described their simulation of a one-dimensional nonlinear lattice which did not show energy equipartition. The 1965 paper by Zabusky and Kruskalshowed that the Korteweg-de Vries (KdV) nonlinear partial differential equation, a long wavelength model of the alpha-lattice (or cubic nonlinearity), derived by Kruskal, gave quantitatively the same results obtained by FPU. In 1967, Zabusky and Deem showed that a localized short wavelength initial excitation (then called an "optical" and now a "zone-boundary mode" excitation ) of the alpha-lattice revealed "n-curve" coherent states. If the initial amplitude was sufficiently large energy equipartition followed in a short time. The work of Kruskal and Miura (KM), Gardner and Greene (GG), and myself led to the appreciation of the infinity of denumerable invariants (conservation laws) for Hamiltonian systems and to a procedure by GGKM in 1967 for solving KdV exactly. The nonlinear science field exponentiated in diversity of linkages (as described in Appendix A). Included were pure and applied mathematics and all branches of basic and applied physics, including the first nonhydrodynamic application to optical solitons, as described in a brief essay (Appendix B) by Hasegawa. The growth was also manifest in the number of meetings held and institutes founded, as described briefly in Appendix D. Physicists and mathematicians in Japan, USA, and USSR (in the latter two, people associated with plasma physics) contributed to the diversification of the nonlinear paradigm which continues worldwide to the present. The last part of the paper (and Appendix C) discuss visiometrics: the visualization and quantification of simulation data, e.g., projection to lower dimensions, to facilitate understanding of nonlinear phenomena for modeling and prediction (or design). Finally, I present some recent developments that are linked to my early work by: Dritschel (vortex dynamics via contour dynamics/surgery in two and three dimensions); Friedland (pattern formation by synchronization in Hamiltonian nonlinear wave, vortex, plasma, systems, etc.); and the author ("n-curve" states and energy equipartition in a FPU lattice).

Journal Article↗

PubMed1981

Bessel filtering of brain stem auditory evoked potentials.

It has been shown previously that conventional high-pass filtering of the brain stem auditory evoked potential (BAEP) results in significant wave form distortion. This distortion can be drastically reduced by using digital filters with zero-phase properties, but this approach requires the use of a digital computer. The Bessel filter is an approximation to a linear phase characteristic, and has the advantage that it may be implemented using analog circuitry. We have considered its use as an alternative-to-digital zero-phase filtering. For the low-pass case, the Bessel phase characteristic is approximately linear throughout the pass band. However, for the high-pass case there is significant phase non-linearity extending well into the pass band. Typical Bessel high-pass filters seriously distort the BAEP wave form; thus, these filters are not an acceptable alternative to the zero-phase digital approach.

Adult↗

PubMed1989

Spatial velocity distribution and acceleration in serial subvalve tunnel and valvular obstructions: an in vitro study using Doppler color flow mapping.

To evaluate the spatial distribution of flow velocities, turbulence and spatial acceleration in serial tunnel-valve obstruction, Doppler color flow mapping was performed in a pulsatile flow model with a tunnel obstruction (1.0 or 1.5 cm2) inserted at 2, 20 and 40 mm proximal to a mildly stenotic bioprosthetic valve studied at flow rates of 1, 2.7 and 4.9 liters/min. Measured pressure gradients were consistently higher across the tunnel (mean +/- SD 32.7 +/- 26.5 mm Hg) than across the tunnel plus valve (28.8 +/- 26.9 mm Hg, p less than 0.01). Doppler color flow map images were analyzed using a Sony RGB video-digitizing computer, providing numerical velocity assignments for the blue, red and green (variance) pixel components to allow the flow maps to be constructed into digital velocity maps and pseudo three-dimensional velocity maps. The maximal velocity stream extended distal to the tunnel (2 to 19 mm), and the length of this extension correlated well with the pressure gradient measured across the tunnel (r = 0.89), with a rapidly decelerating and turbulent spray area seen immediately distal to the valve. Pressure gradient calculated from the maximal velocity derived from the color flow map, which could only be estimated from the velocity maps for the 1.5 cm2 tunnel, correlated well with the gradient measured across the tunnel (18.0 +/- 14.1 versus 19.2 +/- 14.5 mm Hg, respectively, r = 0.98). Acceleration was seen proximal to both tunnels.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Flow Velocity↗

PubMed1996

Lower extremity blood flow and responses to occlusion ischemia differ in exercise-trained and sedentary tetraplegic persons.

OBJECTIVE: To test whether lower extremity blood flow and hyperemic responses to vascular occlusion differ among electrically stimulated exercise trained and sedentary tetraplegic persons and subjects without tetraplegia (control). DESIGN: Blinded cross-sectional comparison, control group. SETTING: Academic medical center. PARTICIPANTS: Ten sedentary tetraplegic men, 10 tetraplegic persons previously habituated to electrically stimulated cycling exercise for 0.4 to 7 years, and 10 nondisabled controls. OUTCOME MEASURES: Subjects underwent quantitative Doppler ultrasound examination of the common femoral artery (CFA). End-diastolic arterial images and arterial flow-velocity profiles obtained at rest and following five minutes of suprasystolic thigh occlusion were computer digitized for analysis of heart rate (HR), CFA peak systolic velocity (PSV), CFA cross-sectional area (CSA), flow velocity integral (FVI), and computed CFA inflow volume (IV). RESULTS: No group main effects were observed for resting HR or FVI. At rest, trained tetraplegic men had 14.9% greater PSV, 29.8% larger CSA, and 51.3% greater IV (p values < .05) than sedentary tetraplegic subjects. Resting PSV and IV of the trained subjects did not differ from controls, although CSA was smaller than controls (p < .05). Following occlusion, PSV, CSA, and IV averaged 16.5%, 33.4%, and 65.1% greater for trained tetraplegics persons, respectively, than sedentary tetraplegic subjects (p values < .05). Only CSA differed between the control and the trained groups (p < .05). CONCLUSION: Tetraplegic persons conditioned by electrically stimulated cycling have greater lower extremity blood flow and hyperemic responses to occlusion than do their sedentary counterparts.

Adult↗

PubMed1981

Reverse cholesterol transport from fibroblasts to high density lipoproteins: computer solutions of a kinetic model.

A model for cholesterol balance between fibroblasts and high density lipoproteins which includes first steps in cholesterol egress is proposed. Kinetic solutions of this model, obtained by digital computer integration of associated differential equations, showed that 15-fold variations in high density lipoprotein levels might be expected to cause less than 8% change in cell cholesterol and twofold variations in lecithin:cholesterol acyltransferase activity might be expected to cause less than 10% change in cell cholesterol. These theoretical calculations are limited by deficiencies in the model. However, they can be used as adjuncts to direct experiment to evaluate the hypothesis that high density lipoproteins and lecithin:cholesterol acyltransferase are involved in cholesterol removal from peripheral cells.

Biological Transport↗

PubMed1978

The impact of computers on electrocardiography.

The development of the electrocardiograph was the culmination of a scientific effort aimed at perfection of a device conceived for the elucidation of a physiologic phenomenon. The development of the digital computer was the culmination of a scientific effort aimed at perfection of warfare. Both of these fairly recent innovations of modern technology have been moderately successful in their initial objectives. Electrocardiography has had a profound influence on the practice of medicine. On the global scene, computers have so far had an insignificant influence on the practice of electrocardiography. In North America, however, computer interpretation of ECGs has already made a modest impact, perhaps more in terms of commercial gains rather than producing a substantial benefits to health care. The introduction of computers into clinical electrocardiography has not resulted in any widespread application of improved diagnostic criteria. The automation of ECG interpretation has not resulted in reduction of the cost of health care, on the contrary, in general it has increased the cost. Perhaps the most dismal failure has been the negligible use of computers in epidemiologic studies and heart disease prevention efforts. Palmistry, astrology, the art of palpation of the pulse, auscultation and acupuncture have had a more profound influence on the practice of medicine than computer analysis of the electrocardiogram. On the positive side, one of the beneficial effects of the use of computers has been the increasing awareness of the limited diagnostic accuracy of currently used ECG criteria, and the recognition of the fact that a substantial improvement is warranted; if such improvement can not be achieved in the foreseeable future, electrocardiography will lose much of its current clinical utility. Computers have had a profound influence on research in electrocardiology, and although a very few tangible concrete results have thus far diffused into clinical electrocardiography, their impact can be expected during the last two decades of this century. Computers will produce at least containment of costs if not actual net cost reduction in clinical electrocardiography. Computer analysis will rapidly antiquate the present primitive visual ECG classification in epidemiologic studies and clinical heart disease intervention trials. Computer analysis will enhance the diagnostic accuracy of the electrocardiogram. However, a radical departure from the current ECG display and interpretation practice will be mandatory before any substantial breakthrough can be materialized. All these anticipated evolutionary and perhaps even revolutionary changes will require a continuing intensive research effort, a change in the professional attitude of practicing electrocardiographers and a considerable effort in professional education. Finally, the elucidation and exploration of the full diagnostic and predictive value of the ECG remains the challenge of first magnitude in electrocardiography...

Adult↗

PubMedDate not supplied

Computers in anesthesiology--a look ahead.

The anesthesiologist is the "systems" person in the operating room whose primary function is making decisions with respect to the patient's pharmacologic and physiologic status. The introduction of digital data processing equipment in the operating room must aid this decision-making function. Instruments that are used to monitor the anesthesia machine or patient variables will provide input to a digital computer. The computer will serve to aggregate and organize signals for data processing and display. Engineering a suitable display with appropriate interfacing with the anesthesiologist is one of the major problems to be solved. As higher levels of processing become available and as the display technique develops, the array of instruments in the operating room will become an integrated information system to better support and aid the anesthesiologist.

Anesthesiology↗

PubMed1993

Radiographic estimation of long bone cross-sectional geometric properties.

Because of their biomechanical significance, cross-sectional geometric properties of long bone diaphyses (areas, second moments of area) have been increasingly used in a number of form/function studies, e.g., to reconstruct body mass or locomotor mode in fossil primates or to elucidate allometric scaling relationships among extant taxa. In the present study, we test whether these biomechanical section properties can be adequately estimated using biplanar radiographs, as compared to calculations of the same properties from computer digitization of cross-sectional images. We are particularly interested in smaller animals, since the limb bone cortices of these animals may not be resolvable using other alternative noninvasive techniques (computed tomography). The test sample includes limb bones of small (25-5,000 g) relatively generalized quadrupedal mammals--mice, six species of squirrels, and Macaca fascicularis. Results indicate that biplanar radiographs are reasonable substitutes for digitized cross-sectional images for deriving areas and second moments of area of midshaft femora and humeri of mammals in this size range. Potential application to a variety of questions relating to mechanical loading patterns in such animals is diverse.

Animals↗

PubMed1988

Principles and clinical applications of image analysis.

Image processing has traveled to the lunar surface and back, finding its way into the clinical laboratory. Advances in digital computers have improved the technology of image analysis, resulting in a wide variety of medical applications. Offering improvements in turnaround time, standardized systems, increased precision, and walkaway automation, digital image analysis has likely found a permanent home as a diagnostic aid in the interpretation of microscopic as well as macroscopic laboratory images.

Cytogenetics↗