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At least 1,297 records · Page 72Linked to original sources
PubMed1990

Automated administration of lidocaine for the treatment of ventricular arrhythmias.

An automated lidocaine infusion system has been developed for the treatment of ventricular arrhythmias. A drug serum concentration which is in the therapeutic range is initially achieved and maintained by an open-loop infusion regimen. The lidocaine infusion rate is then adjusted using closed-loop control to regulate the rate of premature ventricular contractions (PVC rate) at a setpoint. The major system components are a portable computer, a computer-controlled drug infusion pump, and an arrhythmia monitor which is used to measure the PVC rate. During closed-loop control, the drug infusion rate is constrained to keep the predicted serum concentration below an upper limit (ceiling concentration) so that toxic serum concentrations are avoided. The infusion rate is also constrained to keep the predicted serum concentration above a minimum value (floor concentration) to ensure the maintenance of a therapeutic serum level during closed-loop control. The system has been evaluated in initial clinical trials.

Algorithms↗
PubMed2006

Diffusion anisotropy changes in the brains of professional boxers.

BACKGROUND AND PURPOSE: Professional boxing may result in brain injury. We hypothesize that quantitative MR diffusion imaging may be useful in determining early white matter changes. METHODS: Forty-nine professional boxers (age 30 +/- 4.5 years) and 19 healthy control subjects (age 32 +/- 9.5 years) were imaged on a clinical 1.5T scanner. None of the subjects had neurologic disorder or deficit. The average diffusion constant (D(av)) and diffusion anisotropy (FA) were determined pixel by pixel. Regional diffusion measurements were done in the corpus callosum (CC) and internal capsule (IC). The whole brain diffusion constant (BD(av)) was also determined. Student t test was used to analyze the diffusion difference between boxers and the healthy control subjects. P < .05 was considered statistically significant. RESULTS: Of the 49 professional boxers, 42 had normal conventional MRIs. The remaining 7 boxers had abnormal MR imaging findings dominated by nonspecific white matter disease. There was a significant difference in diffusion and anisotropy measurements in all the boxers compared with the healthy control subjects. In the boxer group, BD(av) increased and FA decreased significantly in the CC and posterior limb of IC. The measured FA and D(av) inversely correlated in regions of CC and IC in boxers but not in healthy control subjects. BD(av) also robustly correlated with both FA and D(av) in the splenium of CC in boxers. CONCLUSION: Increased BD(av) and the decreased FA in the CC and IC may represent preclinical signs of subtle brain injury in professional boxers.

Adult↗
PubMed1994

Multiple imputation as a missing data machine.

This paper deals with problems concerning missing data in clinical databases. After signalling some shortcomings of popular solutions to incomplete data problems, we outline the concepts behind multiple imputation. Multiple imputation is a statistically sound method for handling incomplete data. Application of multiple imputation requires a lot of work and not every user is able to do this. A transparent implementation of multiple imputation is necessary. Such an implementation is possible in the HERMES medical workstation. A remaining problem is to find proper imputations.

Algorithms↗
PubMed1996

[NIHS information and computing infrastructure (NICI)].

We describe the information and computing infrastructure in National Institute of Health Sciences, which were constructed until May, 1996. The in house computer network and computing facilities for common usage in NIHS have been developed under the initiative of Division of Chem-Bio Informatics since 1989. The present LAN (Local Area Network) consists of coaxial cables and optic fibers which are connected by a LAN Switch. The LAN is connected to the Internet via IMnet, the inter ministry network back bone of the Science and Technology Agency. Various types of workstations and personal computers such as SUN WS, Silicon Graphics WS, IBM WS & PC, Macintosh, and NEC PC are connected to the LAN. This computing network environment which we named NICI (NIHS Information and Computing Infrastructure) not only provides network communications but also facilitates advanced computating systems for chemical safety research at NIHS as a COE.

Biological Science Disciplines↗
PubMed1993

Using cell replication data in mathematical modeling in carcinogenesis.

Risk estimation involves the application of quantitative models of dose versus response to carcinogenicity data. Recent advances in biology, computing, and mathematics have led to the application of mathematically complicated, mechanistically based models of carcinogenesis to the estimation of risks. This paper focuses on two aspects of this application, distinguishing between models using available data and the development of new models to keep pace with research developments.

Animals↗
PubMedDate not supplied

[A mathematical model of operative analysis and prognosis in outbreaks of hospital infections in newborn infants (exemplified by Klebsiella infection)].

The results of investigations on the development of a mathematical model (computer program) for the study (imitation) of outbreaks of hospital infections among newborns, caused by Klebsiella pneumoniae. The mathematical model, when "saturated" with real data of the outbreak, opens wide possibilities for the operative analysis and prognosis of morbidity and mortality levels among newborns at the intensive therapy departments of maternity clinics and hospitals. The possibilities of the model (computer program) are illustrated by the prognostic calculations of 3 outbreaks (hypothetical) of hospital infections at the intensive therapy department of the university clinic of Universitario del Valle, Cali (Colombia), resulting from violations of sanitary regulations by medical staff members.

Colombia↗
PubMed1991

Software for the development and evaluation of probabilistic identification matrices.

A number of programs are described for the development and evaluation of probabilistic identification matrices for use with computer-assisted identification. The program BEST reads an initial matrix of per cent probabilities for all the binary characters examined during a cluster analysis and determines the most useful set of tests for distinguishing taxa in the matrix. Program RESORT creates from the initial matrix an identification matrix in which the order of the tests may be different or the number of tests reduced. A printed version of a matrix can be produced by MATPRINT, which creates tables giving the per cent probability of a positive test result and the test results presented as '-', 'v' and '+' depending on a user-specified threshold. Program IDSC evaluates an identification matrix by calculating the best identification score for each taxon in the matrix using the expected result for each test. The programs were written in FORTRAN 77 and can be run on any micro-computer using the PC/MS-DOS operating system.

Algorithms↗
PubMed1988

A comparison of the risk of vertebral fracture in menopausal osteopenia and other metabolic disturbances.

The risk of atraumatic compression fracture in postmenopausal women increases as vertebral trabecular bone density decreases. To determine whether the risk is similar for patients who have other metabolic disorders, we compared eight-nine patients who had various disturbances affecting bone and sixty-three postmenopausal women who had no evidence of underlying disease. Trabecular bone density was measured by quantitative computed tomography of the lumbar spine. The relationship between frequency of fracture and bone density was modeled mathematically with spline threshold, quadratic polynomial, and decaying exponential functions. Analysis of covariance showed that the diagnostic category did not influence the relationship between frequency of fracture and bone density in any of the three models. We concluded that the risk of atraumatic compression fracture, as assessed by measurement of vertebral trabecular bone density using quantitative computerized tomography, is independent of the underlying metabolic disturbance.

Adult↗
PubMed1995

A Bayesian framework for understanding texture segmentation in the primary visual cortex.

This paper presents a mathematical theory for understanding the computations involved in texture segmentation in the primary visual cortex. We propose that texture segmentation is a part of the early visual system's overall strategy to infer surfaces of objects in a visual scene. Based on this insight, we use the Bayesian inference paradigm to formulate the texture segmentation problem into a maximum a posteriori surface inference problem. The dynamical system for finding the optimal solution of this problem can be characterized by two concurrent and interactive processes: a gradual sharpening of the boundary signals and a simultaneous smoothing of the surface signals. The behavior of these dynamical processes was studied using both analytical and computational methods. We present some computational results and mathematical predictions. This theory suggests a novel framework for understanding the functional roles of the complex cells in the primary visual cortex.

Bayes Theorem↗
PubMed2004

Computational cardiac anatomy using MRI.

Ventricular geometry and fiber orientation may undergo global or local remodeling in cardiac disease. However, there are as yet no mathematical and computational methods for quantifying variation of geometry and fiber orientation or the nature of their remodeling in disease. Toward this goal, a landmark and image intensity-based large deformation diffeomorphic metric mapping (LDDMM) method to transform heart geometry into common coordinates for quantification of shape and form was developed. Two automated landmark placement methods for modeling tissue deformations expected in different cardiac pathologies are presented. The transformations, computed using the combined use of landmarks and image intensities, yields high-registration accuracy of heart anatomies even in the presence of significant variation of cardiac shape and form. Once heart anatomies have been registered, properties of tissue geometry and cardiac fiber orientation in corresponding regions of different hearts may be quantified.

Algorithms↗
PubMed2004

Neuropsychological correlates of basal ganglia and medial temporal lobe NAA/Cho reductions in traumatic brain injury.

BACKGROUND: Proton magnetic resonance spectroscopy can assess neurochemical sequelae in traumatic brain injury. Metabolic abnormalities are present in the acute or subacute period in patients with traumatic brain injury and correlate with outcome on clinical scales. OBJECTIVE: To investigate the use of proton magnetic resonance spectroscopy in detecting possible gray subcortical neurochemical impairments and their relationship with neuropsychological performance. DESIGN: Group comparisons and correlations of brain metabolites with clinical and neuropsychological variables. PATIENTS AND METHODS: Metabolite concentrations were acquired from voxels localized to the basal ganglia and medial temporal region in 20 patients with long-term moderate and severe traumatic brain injury and 20 matched control subjects. Both groups underwent neuropsychological assessment. RESULTS: N-acetylaspartate-choline-containing compounds ratios were decreased in patients in the basal ganglia (t = -3.28, P =.002) and medial temporal region (t = -3.52, P =.001). The basal ganglia ratio correlated to measures of speed, motor scanning, and attention. CONCLUSION: Patients with long-term TBI present a regional correlation pattern that may help identify the neurological basis of cognitive sequelae in traumatic brain injury.

Adolescent↗
PubMed2000

Delay and dispersion effects in dynamic susceptibility contrast MRI: simulations using singular value decomposition.

Dynamic susceptibility contrast (DSC) MRI is now increasingly used for measuring perfusion in many different applications. The quantification of DSC data requires the measurement of the arterial input function (AIF) and the deconvolution of the tissue concentration time curve. One of the most accepted deconvolution methods is the use of singular value decomposition (SVD). Simulations were performed to evaluate the effects on DSC quantification of the presence of delay and dispersion in the estimated AIF. Both delay and dispersion were found to introduce significant underestimation of cerebral blood flow (CBF) and overestimation of mean transit time (MTT). While the error introduced by the delay can be corrected by using the information of the arrival time of the bolus, the correction for the dispersion is less straightforward and requires a model for the vasculature.

Adult↗
PubMed1995

Sample self-stacking and sample stacking in zone electrophoresis with major sample components of like charge: general model and scheme of possible modes.

A theoretical study is presented of zone electrophoretic behavior of samples that contain one or more minor analytes and at least one major ionogenic component of like charge. Based on a simple model comprising weak univalent anionic electrolytes, conditions are derived under which analytes are temporarily focused isotachophoretically into very narrow zones by a sample self-stacking effect provided by the major sample components. Requirements for minimal/maximal mobility and a background coion concentration dependent minimal concentration of a major sample component (stacker) are presented. For systems in which sample self-stacking does not apply, an expression for the concentrating factor is derived that involves the effects of both nonselective (classical) and selective sample stacking, the latter being a consequence of electrophoretic separation of the minor analyte from the major component. The theory derived is discussed with selected model examples by using both numerical calculation and computer simulation.

Electric Conductivity↗