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At least 271 records · Page 15Linked to original sources
PubMed1995

An algorithm for analysing probed partial digestion experiments.

A partial digestion of DNA (e.g. cosmid. Lambda, YAC, chromosome) is performed and the lengths of thoses fragments which hybridize to a labeled probe are measured using gel electrophoresis. We give an efficient algorithm that takes as input this experimental data and proposes one or more candidate solutions. Each solution designates the location of each restriction site and specifies the endpoints of each fragment. (Further experiments can then be designed to select the correct solution from this small set of candidates.) The algorithm works well even when the experiment gives inexact values for the lengths.

Algorithms↗
PubMed1984

On the construction of functional maps in positron emission tomography.

A linear algorithm for the rapid calculation of local rate constants is proposed. The method is applicable to the three-compartment models currently used in the analysis of positron camera measurements with [11C]methionine, [11C]deoxyglucose, and [11C]glucose. The same technique can also be used for the regional measurement of local blood flow with the aid of a freely diffusible tracer. The algorithm was applied to measurements on humans with [11C]glucose. As a comparison, the same data were also analyzed with a standard nonlinear technique. Good agreement between the two methods was obtained.

Brain↗
PubMed1979

Automated scene analysis of CT scans.

Since the advent of computed tomography, there has been an increasing realization that CT scans contain quantitative as well as qualitative information useful in the diagnostic process. Often however, the use of this information is impeded by the tedious manual outlining of the areas of interest in the scan. To alleviate this problem, we have developed a scene segmentation algorithm which will automatically delineate areas of interest in a CT scan. This procedure uses known information about the expected objects in the scan in conjuction with an algorithm to label those objects. The resultant scene segmentation divides the scan into four anatomical areas: skull, normal brain, high density lesions and CSF. After an area of interest is interactively selected by the clinician, volume, density or other quantitative measures may be computed. Limitations of the algorithm and its clinical applications are discussed.

Absorptiometry, Photon↗
PubMed1991

Volume rendering and connectivity algorithms for MR angiography.

Several display algorithms for three-dimensional angiographic data are evaluated. The mathematical analysis assumes additive Gaussian noise to predict the background distribution function for maximum intensity projection, sum projection, and connectivity display methods. In the maximum intensity projection method the mean noise level increases with the number of voxels in the ray, while in the sum projection the noise distribution width increases with the projection thickness, but the mean level remains constant. Comparisons of maximum intensity projection, sum projection, and connectivity algorithms applied to an MR angiogram of the circle of Willis are made. Measurements of the noise distribution are in agreement with the analysis. Algorithms combining connectivity with maximum intensity and sum projection are also evaluated. In these methods, a projection image is created using only the voxels marked by connectivity, typically with a 6% threshold of the data. Fine vessels are resolved and background noise is reduced in agreement with the analysis.

Algorithms↗
PubMed1989

A program package for self-assessment and examination in biochemistry.

A BASIC program has been developed for self-evaluation and testing of an individual's knowledge of main categories in biochemistry. The computer tests permit sequential or random distribution of items, random distribution of answers in each item at each new run, effective feedback control with the student, use of a program clock to determine different time allowance, precise and quick analysis and grading of student's answer thus saving the time and labour of examiners. Editing, deleting and appending of new items is easily achieved. Information is obtained for verifying the quality of the test itself. Examination versions of tests in ten categories have been combined into an annual computer test in biochemistry.

Algorithms↗
PubMed1986

Simulation of the spatial distribution of muscle fibres in human muscles.

A composite muscle cross section model was simulated on a VAX 780 computer. The various motor unit territories in the cross section area were circular, partially overlapping each other. The radii of the territories of the motor units, their centres, and the number of muscle fibres in each motor unit were treated as random variables. Two different models were generated, one with a uniform distribution of the fibres in the motor unit territories, and the other with a normal distribution of the fibres. An algorithm for simulation of fibre density measurements was written, and the effects of varying the parameters of the model on fibre density measurements were investigated. The results of the computer simulation were in agreement with analytical and laboratory findings.

Computers↗
PubMed2026

Prediction of antimicrobial minimum inhibitory concentration from bacterial genomes using a scalable and interpretable machine learning approach.

Although machine learning models can predict antimicrobial susceptibility from bacterial whole genome sequencing (WGS), state-of-the-art approaches are computationally demanding or dependent on knowledge of genetic resistance determinants. Here, we describe an efficient data-driven approach to predicting minimum inhibitory concentration (MIC) by progressively extending and refining predictive genome segments, independent of prior knowledge of resistance determinants. Resultant models had high interpretability - known and potentially novel resistance determinants were captured. Using 762 clinical E. coli strains, 71.6% of predictions were within one dilution of the measured MIC. Models trained with this algorithm generalised better onto external data (F1 score = 0.85) compared with alternative models trained on annotated resistance determinants (F1 = 0.82) or k-mer counts (F1 = 0.74). Computational demands were low (RAM usage 23.6GB vs 38.8GB for k-mer model). These advantages represent an important advance in predicting antimicrobial susceptibility from WGS, with potential applications for clinical diagnostics, drug development, and surveillance.

Journal Article↗
PubMed1977

An acoustic-perceptual method for the quantitative evaluation of hypernasality.

A computer implementation is proposed as a method for assessing the quality of an individual's speech from a perceptual and communicative point of view. The input to this procedure is a standardized set of speech samples (vowels and selected consonants) designed to permit an evaluation of the speaker's phonology. The output is a numerical specification of the functional adequacy of the target values of the phonetic segments under analysis. The computer program consists of three parts: a simulated auditory analyzer, the output of which is a spectral representation of each test item; an algorithm that computes a psychoacoustically based measure of distinctiveness or perceptual distance for each pair of test spectra, and a routine for comparing, in terms of this measure, the test items with the corresponding reference items drawn from a population of normal speakers or a recording made before patient intervention.

Acoustics↗
PubMed1989

A three-dimensional electron pencil-beam algorithm.

We describe the implementation of a three-dimensional electron-dose algorithm based on a Gaussian pencil-beam model. The algorithm calculates dose to an arbitrarily distributed set of points in a heterogeneous volume. Multiple non-coplanar beams can be positioned relative to the volume. The algorithm consists of three basic components: (i) the transport of a pencil-beam through a heterogeneous volume, (ii) the evaluation of the pencil-beam fluence at a given depth in the volume in the presence of irregular fields, and (iii) the matching of points in the volume receiving a significant fluence contribution from a pencil-beam at a given depth in the volume and the calculation of dose to those points. An efficient point-matching algorithm reduces the computation time to the level of conventional two-dimensional implementations. The algorithm uses an optimised subdivision for irregular fields, and accurately predicts output factors for irregular fields placed between the final collimators and the patient. We show comparisons between the new algorithm and conventional two-dimensional calculations using measurements and calculations for finite heterogeneities, irregular fields and output factors.

Algorithms↗
PubMed1984

Algorithms for restriction map comparisons.

An algorithm is presented which compares two restriction maps, yielding a measure of distance between the maps and relating the maps by an alignment. This new algorithm finds the minimum weighted sum of genetic events required to convert one map into the other, where the genetic events are the appearance/disappearance of restriction sites and changes in the number of bases between restriction sites. The algorithm is illustrated by comparison of the beta-delta region of the globin gene cluster of four primate species. The results are in excellent agreement with known evolutionary relationships.

Animals↗
PubMed1995

A real-time electrical impedance tomograph.

Electrical properties of tissues in the human body can be imaged using a technology known as Electrical Impedance Tomography. In this modality, sinusoidal electrical currents are applied to the body using electrodes attached to the skin, and voltages that are developed on the electrodes are measured. Using these data, a reconstruction algorithm computes the conductivity and permittivity distributions within the body. This paper describes the reconstruction algorithm, image display algorithm, and hardware of a real-time Electrical Impedance Tomograph known as the Real-Time Imaging System. The reconstruction algorithm, executed by a commercially available coprocessor board that resides in a 386-based personal computer, is a modification of the Newton's One Step Error Reconstructor (NOSER) that minimizes algorithm execution time by precomputing many quantities. The image display algorithm, also executed by the coprocessor board, maps the output of the reconstruction algorithm into an image which is displayed using a video graphics board. The architecture of the system and execution times of algorithms implemented by the system are discussed. Using the continuous data acquisition mode of the Real-Time Imaging System, data from the thorax of a normal human subject were collected. Admittivity changes in the chest, as a result of respiration and the cardiac cycle, are presented. Data that were collected from the leg of a normal subject are shown which demonstrate capabilities of the triggered data acquisition mode of the system, allowing data acquisition synchronization with an electrocardiogram.

Algorithms↗
PubMedDate not supplied

Characterization of a p(66)Be(49) neutron therapy beam II: skin-sparing and dose transition effects.

Results of buildup measurements in A-150 tissue equivalent plastic are presented for a p(66)Be(49) neutron beam. These measurements were taken in air and behind various materials to answer questions about skin-sparing, bolussing materials, recovery of skin-sparing, and dosimetry in small radiobiological samples. The depth for Dmax for this beam is 1.6 g cm-2. An algorithm is also presented that reproduces the measured dose buildup curves.

Computers↗
PubMed1991

Envelope expansion methods for speech enhancement.

The last decade has seen increasing interest in techniques for the enhancement of digital speech signals. Significant gains have been made in terms of signal-to-noise ratio (SNR) and quality, but few techniques have produced improvements in intelligibility. A method for speech enhancement based on nonlinear expansion of the spectral envelope is presented. The expansion is consistent with both the long-term spectrum of the speech and with the probability that speech is present in a given sample. Objective SNR measures are used to compare this algorithm with the well-known spectral subtraction method, with an alternative expansion scheme, and with limiting SNRs resulting from perfect recovery of the amplitude spectrum. For the purpose of intelligibility assessments, a simplified version of the algorithm has been implemented on a Texas Instruments TMS320-C25 system. Listening trials with this real-time system, conducted using a modified rhyme test, have produced small, but consistent, improvements in articulation scores.

Acoustics↗
PubMed1984

Myocardial contrast two-dimensional echocardiography: comparison of contrast disappearance rates in normal and underperfused myocardium.

A computer algorithm was developed and applied to measure brightness decay rates of myocardial contrast opacification observed with two-dimensional echocardiography (2DE). An agitated mixture of diatrizoate meglumine and saline (Renografin-saline) was injected into the left main coronary artery of 17 closed-chest dogs during the control state as well as after placement of an intracoronary plug to induce 85% stenosis in the left anterior descending coronary artery (LAD) in five dogs. In 12 dogs, injections were also performed distally to complete intracoronary balloon occlusion of the LAD. For each injection, up to 35 electrocardiographic-gated, end-diastolic 2DE frames were digitized into an image-processing computer that determined mean pixel brightness of each of 12 myocardial segments per 2DE short-axis cross-section. Time-activity curves for each segment were generated, and contrast decay half-life (t 1/2) was calculated. Mean t 1/2 for control-state injections was found to be 24.1 +/- 7.7 sec, as opposed to 293.8 +/- 164.5 sec after complete coronary occlusion (p less than .001). In the five dogs in which 85% LAD stenosis was induced, prolongation of contrast t 1/2 from 18.3 +/- 8.9 sec during control to 44.3 +/- 21.0 sec (p less than .001) after plug insertion occurred in myocardial segments subserved by the stenosed vessel. No significant change occurred in segments that were not supplied by the stenosed vessel (21.9 +/- 9.1 sec during control vs 24.9 +/- 11.6 after plug insertion into the LAD). A reproducibility study of injection-to-injection t 1/2 in the control state indicated a correlation coefficient of r = .84 and a standard error of the estimate (SEE) equal to 5.86 sec, while interobserver t 1/2 reproducibility was r = .91 and SEE = 5.21 sec. The t 1/2 measurement derived by computer analysis of myocardial contrast 2DE may serve as an index for characterization of regional myocardial blood flow and may be applicable to evaluate interventions that alter perfusion.

Animals↗
PubMed1994

Stages of change in adopting healthy diets: fat, fiber, and correlates of nutrient intake.

The stages of change construct, which addresses the readiness to change, has only recently been applied to dietary behavior, such as fat consumption. This article describes the application of the stages of change construct to dietary fat and fiber consumption and examines the association of dietary stages to eating practices and related demographic and psychosocial factors in a large, geographically diverse population of workers. We present results from the baseline survey of 17,121 employees in the Working Well Trial. We assessed stage from an algorithm based on seven items and measured dietary intake with an 88-item food frequency questionnaire. Findings indicated that a greater proportion of the population has actively tried to reduce fat intake than to consume more fiber. Stage of change was associated with fat, fiber, and fruit and vegetable intake in a stepwise manner, as predicted. In multivariate analyses that controlled for demographic characteristics, stage of change predicted between 8 and 13% of the variance in dietary intake, and more than demographic variables. These findings have implications for the design of nutrition interventions and for the evaluation of intermediate outcomes.

Adult↗
PubMed1981

Stereotactic surgical system controlled by computed tomography.

The three-dimensional data obtained by computed tomographic (CT) scanning offer an advantage in using this imaging technique for stereotactic surgical procedures. This requires interfacing of CT image data with a stereotactic guide. In the performance of functional procedures where the surgical target must be identified from brain landmarks, such as the anterior and posterior commissures, an image reconstruction technique that presents in an image high spatial resolution structural information must be used. The description of a fully hardware- and software-interfaced CT-directed stereotactic surgical system is presented. The logic of operation and examples of images reconstructed with a high spatial resolution algorithm are illustrated. The experimentally determined measurement of an electrode tip localization with this system is within 1 pixel or +/- 0.5 mm in any direction.

General Surgery↗
PubMed1992

Pressure ulcers in adults: prediction and prevention. Quick reference guide for clinicians. Agency for Health Care Policy And Research.

These guidelines are presented in a user-friendly format for quick reference in daily practice. The goals are to: 1) identify at-risk individuals needing prevention and the specific factors placing them at risk; 2) maintain and improve tissue tolerance to pressure in order to prevent injury; 3) protect against the adverse effects of external mechanical forces; and 4) reduce the incidence of pressure ulcers through educational programs. An algorithm helps to specify appropriate prevention measures.

Adult↗