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At least 793 records · Page 44Linked to original sources
PubMed1980

Spread of cancer cells in tissues: modelling and simulation.

Continuing previous studies in which tumor diseases were interpreted as unstable control loops, the present paper tries to determine the spatial structure and the time behaviour of cell renewal systems. For this purpose a computer model for the two-dimensional cell space was developed, which is described by a set of specifications and growth statements. Selected case studies are then simulated by means of a digital computer (CYBER 76). The development of this model enables a deeper insight into the structure and function of disturbed cell renewal processes. Furthermore, it is possible with this computer model to simulate simple basic cases which, in reality, could hardly or not at all be tested.

Animals↗
PubMed1980

Computer studies of the spatial structure and temporal growth of tumor cells.

In the present paper we attempt to determine the spatial structure and the time behaviour of cell renewal systems, continuing previous studies in which tumor diseases were interpreted as unstable control loops. A computer model wa developed for the two-dimensional cell space, which is described by a set of specifications and growth statements. Selected case studies are then simulated by means of a digital computer (CYBER 76). In the development of this model special emphasis was given to (i) the existence of several cell systems with different mean life spans, growing in competition; (ii) the variability of the mean life spans of a cell and of the initial configuration of cell patterns; (iii) the description of the cell-to-cell interactions; (iv) the perturbation of normal cell growth by tumor cells and their elimination in medicine comparable with a direct irradiation or removal by surgery; (v) the consideration of the loss of tumor cells. The development of this model enables a deeper insight into the structure and function of disturbed cell renewal processes. Systematic studies were made on the influence of the size of a tumor nucleus and the mean life span of a tumor cell on the tumor growth assuming constant cell loss. Furthermore it is possible with this computer model to simulate simple basic cases which are difficult to test in real life.

Cell Division↗
PubMed1978

Volume of brain ventricles in man determined by computer tomography.

In order to measure the absolute ventricular volumes in ml we developed a method using the numerical prints of CT (EMI, CT 1000) on which--by comparing with corresponding Polaroid photos--the margin between brain tissue and ventricles was drawn. For further evaluation, a curve digitizer and a digital computer were used. In 51 patients without any abnormal findings in CT, we studied the volume of single ventricles. The mean value of the whole ventricular system was 30.9 +/- 5.7 ml. Reproducibility by this method is within a range of 5%.

Cerebral Ventricles↗
PubMed1990

Digital imaging techniques in dermatology.

Digital imaging is a versatile technique that has been infrequently used in dermatology to record visual images. We have used this technology for 10 patients to follow cutaneous lesions, including alopecia mucinosa, psoriasis, and dysplastic nevi. The setup included a personal computer, digitizer board, monitor, video camera, and lights. An introduction to electronic (digital) imaging is given and some of the many possible applications in dermatology are discussed.

Humans↗
PubMed1983

[Using computer for radiotherapy planning].

Our Computer system linked with CT has been found to be very useful for radiotherapy treatment planning. We apply this system to treatment planning of about one half of the total cases of external beam radiotherapy and of all cases of brachytherapy. In the field of computer aided automation of radiotherapy treatment, we estimate automatic verification of treatment parameters and automatic recording of them are practically useful in routine radiotherapy. Conformation Radiotherapy can be realized to be practical when digital computer and CT are employed. On the basis of 300 cases of our clinical experiences of computer controlled conformation radiotherapy, the indication of conformation radiotherapy and clinical significance are described in this paper.

Aged↗
PubMed1977

Computer-assisted analysis of particulate axoplasmic flow in organized CNS tissue cultures.

Using organized nervous system tissue cultures of embryonic mouse spinal cord, time-lapse motion pictures of intra-axonal particle movements were made using Nomarski optics. The paths of 272 particles were followed and analyzed using digital computer methods. Particles had a bidirectional saltatory motility with net anterograde and retrograde velocities which were shown to be the same (about 1 micron per second). When anterograde moving and retrograde moving particles were analyzed separately for anterograde and retrograde saltations, the velocities of saltation in the direction of net movement were found to be 1.5 times greater than saltations against the direction of net movement. These differences were statistically significant. In addition, it was shown that there were regions within the axon where variations in particle motion were similar from particle to particle as they passed, and that more disturbed motion was found to occur near intra-axonal objects which were judged to be mitochondria. No decrease of particle velocity was noted in regions away from mitochondria nor was in increase in velocity noted near them. Computer-drawn particle plots illustrate the various facets of particle motion.

Animals↗
PubMed1985

Perioperative Holter monitoring and computer analysis of dysrhythmias in cardiac surgery.

In order to increase the accuracy and efficiency of studying perioperative dysrhythmias, 52 patients undergoing cardiac surgery were fitted preoperatively with a Holter monitor adapted for intraoperative recording, and the preoperative, intraoperative and early postoperative cardiac electrical activities were classified with a digital computer. Forty patients underwent coronary artery bypass grafting (CABG), eight had valve replacements, and four had combined procedures. The results showed the following: (1) high incidence of various dysrhythmias occurring during anesthesia induction and thoracotomy prior to aortic cross-clamp; (2) high incidence of continued atrial activity during cardioplegia; (3) lack of correlation between peak serum CPK-MB levels and dysrhythmias; and (4) a higher overall incidence of dysrhythmias in valve patients. Adapting the Holter monitor technique for cardiac surgery can solve the problem of observer vigilance inherent to such a study using a human "monitor watcher," and facilitate the accurate analysis of the vast amount of data obtained. This is important in quantitating the electrophysiologic effects of various perioperative interventions, such as the anesthetic agents, beta-blockers, calcium antagonists, and cardioplegic solutions.

Arrhythmias, Cardiac↗
PubMed1981

Computer-derived image compositing.

A computer-derived composite image is obtained of the details contained in successive photomicrographs taken by optical sectioning of the collagen networks in the pulmonary interalveolar wall. Three-dimensional information is therefore contained in a two-dimensional portrayal, providing a basis for computer digital analysis otherwise not readily available.

Computers↗
PubMed1993

Time-optimized analysis of slit-scan chromosome profiles on a general-purpose personal computer.

Slit-scan flow cytometry provides a method to analyze large numbers of metaphase chromosomes in a relatively short time due to morphological features. The high detection rate requires fast computing for on-line analysis. Up to now, this has been achieved using special-purpose computers, parallel systems or other complex hardware. Here, we describe an algorithm that can be implemented on a general-purpose personal computer. Digitized chromosome profiles can be classified by several criteria especially for the detection of chromosome abnormalities in biological dosimetry. A data set of approximately 4600 profiles was used. Programming in assembler results in an average computing time of about 600 microseconds per profile. Thus on-line evaluation of slit-scanning data appears to become feasible for many flow cytometers running nowadays.

Algorithms↗
PubMed2003

General-purpose computation with neural networks: a survey of complexity theoretic results.

We survey and summarize the literature on the computational aspects of neural network models by presenting a detailed taxonomy of the various models according to their complexity theoretic characteristics. The criteria of classification include the architecture of the network (feedforward versus recurrent), time model (discrete versus continuous), state type (binary versus analog), weight constraints (symmetric versus asymmetric), network size (finite nets versus infinite families), and computation type (deterministic versus probabilistic), among others. The underlying results concerning the computational power and complexity issues of perceptron, radial basis function, winner-take-all, and spiking neural networks are briefly surveyed, with pointers to the relevant literature. In our survey, we focus mainly on the digital computation whose inputs and outputs are binary in nature, although their values are quite often encoded as analog neuron states. We omit the important learning issues.

Algorithms↗
PubMed1983

Computer analysis of the spatial angular parameters of the canine QRSsE loop from necropsy-verified normal dogs.

Vectorcardiograms were recorded by the canine modification of the axial lead system of McFee and Parungao from 38 necropsy-verified normal dogs placed in the recommended position of right lateral recumbency. A digital computer program was used to identify and analyze the spatial characteristics of the QRSsE loop. In order to define the QRSsE loop in more complete terms, a total of 27 angular parameters were evaluated. Time to specified parameters and angular values at specified times were assessed. The smallest angular range for a frontal plane vector was 15.7 degrees which occurred with the maximum leftward vector. In the sagittal plane the most narrow range was 29.8 degrees found with the half-area vector. The most narrow angular range in the transverse plane was 29.7 degrees with the maximum leftward vector. Other characteristics of the normal dog were found, such as the simultaneous occurrence of the following vectors: the peak spatial magnitude vector; frontal plane maximum vector; maximum leftward vector; maximum caudal vector; sagittal plane half-area vector; and transverse plane maximum vector. Also occurring together, but at a different time, were the sagittal plane maximum vector and the transverse plane half-area vector.

Animals↗
PubMed1976

Aerobic microbial growth in semisolid matrices: heat and mass transfer limitation.

A conceptual model of aerobic microbial growth in semisolid matrices were developed as a first step in the prediction of the rate of breakdown in semisolid cellulosic material. The conceptual model was described by a series of equations simplified by the assumption of steady-state microbial activity, and heat and mass transfer limitation. Temperature and oxygen distribution in compost piles were measured experimentally at the Butler County Mushroom Farm, Butler County, Pennsylvania, to test the validity of these assumptions. The compost piles consisted of ground corn husks, straw, and race horse manure. The data fit with the model was excellent with deviation between model predictions (as solved by an anglog computer) and actual temperature measurements never exceeding 3 degrees C. The effects of compost pile geometry, external temperature, compost density, external oxygen concentration, and insulation at the bottom of the pile were then predicted using a digital computer to solve the model. The predicitions show that the maximum breakdown rate occurs for an optimum height (which depends upon the system), insulating the base increases the breakdown rate, increasing the external temperature increases the initial breakdown rate but decreases the pseudo-steady-state breakdown rate and the uniformity and any increase in the external oxygen concentration increases the breakdown rate but decreases the uniformity.

Aerobiosis↗
PubMed1986

Continuous noninvasive real-time monitoring of stroke volume and cardiac output by thoracic electrical bioimpedance.

Thoracic electrical bioimpedance (TEB) is a noninvasive method for the estimation of left ventricular stroke volume (SV). Objections to TEB in the past have included systematic overestimation of SV and cardiac output in normals, poor correlation in absolute terms with standard cardiac output reference techniques, motion and ventilation artifacts which distorted recorded waveforms except when patients remained in apnea during measurements, and lack of a computer to yield rapid heat-to-beat quantitation of SV and cardiac output. The present study entails real-time, beat-to-beat cardiac output determinations using TEB and assessing its agreement via a digital computer against a reference standard, thermodilution. A correlation coefficient of 0.88 is reported with 85% of data points falling within 20% confidence limits on either side of the line of identity.

Adult↗
PubMed2005

On titanium frameworks and alternative impression techniques in implant dentistry.

PURPOSE: The objectives of this thesis were to compare the clinical and material performance of implant-supported titanium frameworks with gold-alloy frameworks in the edentulous jaw and to test a digitized impression technique to optimize material characteristics and clinical and laboratory procedures. MATERIALS AND METHODS: Two different kinds of laser-welded titanium frameworks and one type of digitized computer numeric controlled (CNC)-milled titanium framework for the edentulous jaw were evaluated and compared with gold-alloy frameworks in two clinical 5-year follow-up studies. The CNC frameworks were also evaluated and compared with gold-alloy frameworks in two experimental studies according to fit, preload, and surface roughness. Furthermore, a digitized photogrammetric technique for recording implant positions in the edentulous jaw was experimentally tested and compared with two conventional impression techniques. RESULTS: Laser-welded titanium frameworks had a lower success rate after 5 years in function than gold-alloy frameworks. The 5-year performance of CNC frameworks was similar to that of gold-alloy frameworks. The fit and precision of implant-supported CNC frameworks was significantly better compared with gold-alloy frameworks. Applications of veneering material did not significantly affect the fit of the titanium frameworks. The preload of CNC frameworks was similar to that of gold-alloy frameworks, both exhibiting significantly decreased preloads after repeated tightening. The preloads of titanium frameworks were similar before and after veneering. Unloaded milled titanium screw sites had significantly rougher surfaces than loaded sites, and loaded gold screws had rougher surfaces than unloaded. No correlation between surface of the screw joints and preload of veneered titanium frameworks was observed. The precision of photogrammetric impressions was comparable to that of conventional impression techniques. CONCLUSIONS: Implant-supported CNC-milled titanium frameworks are a viable alternative to gold-alloy castings in the edentulous jaw, and because a digital platform is used to manufacture these titanium frameworks, photogrammetric impressions can be made.

Adult↗
PubMed1998

The lacrimal keyhole, orbital door jamb, and basin of the inferior orbital fissure. Three areas of deep bone in the lateral orbit.

OBJECTIVES: To calculate the volume of bone in 3 areas of the deep lateral orbit that are available for removal in decompression surgery and to demonstrate these 3 areas within a 3-dimensional computed tomographic reconstruction of the orbit. DESIGN: The 3 areas of bone in the deep lateral orbit were designated the lacrimal keyhole, the sphenoid door jamb, and the basin of the inferior orbital fissure. By means of digitized computed tomographic scans, these 3 areas of bone were analyzed by measuring preoperative and postoperative orbital volumes and predicted bony expansion volumes in 9 patients (17 orbits) who underwent deep lateral orbital decompression surgery. We also calculated the volume of bone that could be removed from 11 normal orbits. A 3-dimensional computer reconstruction of an orbital computed tomographic scan was created, and the 3 areas of potential bone were delineated within it. RESULTS: The average volumes of the basin of the inferior orbital fissure, the sphenoid door jamb, the lacrimal keyhole, and the total of the 3 regions were 1.2, 2.9, 1.5, and 5.6 cm3, respectively. The 3 areas of bone contributed variably to the total, with the door jamb contributing the most volume of the 3, nearly twice the value of the other 2. There was, however, a significant amount of interpatient variability, especially for the door jamb region. CONCLUSION: Orbital decompression surgery of the deep lateral wall can provide adequate volume expansion because of the amount and location of potential space that exists in the 3 areas of deep bone.

Adult↗
PubMed1962

Computation of impulse initiation and saltatory conduction in a myelinated nerve fiber.

A mathematical model of the electrical properties of a myelinated nerve fiber is given, consisting of the Hodgkin-Huxley ordinary differential equations to represent the membrane at the nodes of Ranvier, and a partial differential cable equation to represent the internodes. Digital computer solutions of these equations show an impulse arising at a stimulating electrode and being propagated away, approaching a constant velocity. Action potential curves plotted against distance show discontinuities in slope, proportional to the nodal action currents, at the nodes. Action potential curves plotted against time, at the nodes and in the internodes, show a marked difference in steepness of the rising phase, but little difference in peak height. These results and computed action current curves agree fairly accurately with published experimental data from frog and toad fibers.

Action Potentials↗
PubMed1986

Variability analysis of fetal heart rate signals as obtained from abdominal electrocardiographic recordings.

The present paper introduces an original method of digital signal processing for an automatic analysis of non-invasive abdominal ECG recordings on pregnant women starting from the 25th week of gestation. The procedure has been implemented on a DEC-VAX 750 digital computer at the Department of Electrical Engineering, Polytechnic of Milano and the signals are recorded at the Department of Obstetrics and Gynecology "L. Mangiagalli", University of Milano, Italy. The experimental results presented in here are still preliminary as only few cases have been considered up to now (about 20) and the goal of the paper is mainly focused on the algorithmic aspects of the whole procedure implemented in the computer and on the approach of heart rate variability (HRV) signal analysis both in the mother and in the fetus. Abdominal ECG lead processing is illustrated starting from the step of maternal (M) and fetal (F) QRS recognitions through linear digital filtering (derivative and low-pass FIR filter, Weber-Cappellini window) and weighted averaging techniques synchronized with maternal QRS's. Figure 1 a shows the original abdominal lead; figure 1 b the filtered signal for MQRS recognitions; figure 2 a the template of maternal cardiac cycle as obtained after the averaging operation synchronized with the instants of MQRS occurrence. The subtraction of the template results in the abdominal lead shown in figure 1 c in which the contribution of MECG is practically entirely reduced even in the case of MQRS and FQRS overlapping.(ABSTRACT TRUNCATED AT 250 WORDS)

Electrocardiography↗
PubMed1986

Origins of medical informatics.

Medical informatics is a new knowledge domain of computer and information science, engineering and technology in all fields of health and medicine, including research, education and practice. Medical informatics has evolved over the past 30 years as medicine learned to exploit the extraordinary capabilities of the electronic digital computer to better meet its complex information needs. The first articles on this subject appeared in the 1950s, the number of publications rapidly increased in the 1960s and medical informatics was identified as a new specialty in the 1970s.

History, 20th Century↗