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Results for “Measuring algorithm”

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At least 1,657 records · Page 92Linked to original sources

PubMed2003

Improved cardiovascular risk stratification by a simple ECG index in hypertension.

BACKGROUND: We determined the prognostic value of the Cornell/strain [C/S] index, a simple electrocardiographic (ECG) index for left ventricular hypertrophy (LVH) defined by the presence of either a classic strain pattern or a Cornell voltage (sum of R in aVL + S in V(3)) >2.0 mV in women or 2.4 mV in men, or both. METHODS: In a prospective, cohort study, 2190 initially untreated subjects (age 51 [+/- 12], 47% women) with essential hypertension without prior events were followed for up to 14 years (median, 5 years). RESULTS: Prevalence of LVH at entry was 16.3% by using the C/S index, which yielded 33.6% sensitivity and 91.0% specificity. Other ECG criteria for LVH including Sokolow-Lyon, Romhilt-Estes, Framingham, Cornell, and strain alone, achieved a lower sensitivity and prevalence. Over the subsequent follow-up, 244 patients experienced a first major cardiovascular event. Event rate (x 100 person-years) was 2.01 in those without and 4.44 in those with LVH by the C/S index (P <.001). After adjustment for age, sex, smoking, and other counfounders, the C/S index identified subjects at increased risk of events (relative risk 1.76; 95% confidence interval 1.32-2.33). The C/S index achieved the highest population-attributable risk (16.1%) for cardiovascular events. CONCLUSIONS: A simple ECG index that can be quickly measured from nondigital machines and without algorithms identifies LVH in a consistent proportion (16.3%) of hypertensive subjects. The LVH defined by such technique allows identification of individuals at high risk for cardiovascular events.

Aged↗

PubMed2003

Knowledge-based approach to septic shock patient data using a neural network with trapezoidal activation functions.

In this contribution we present an application of a knowledge-based neural network technique in the domain of medical research. We consider the crucial problem of intensive care patients developing a septic shock during their stay at the intensive care unit. Septic shock is of prime importance in intensive care medicine due to its high mortality rate. Our analysis of the patient data is embedded in a medical data analysis cycle, including preprocessing, classification, rule generation and interpretation. For classification and rule generation we chose an improved architecture based on a growing trapezoidal basis function network for our metric variables. Our results extend those of a black box classification and give a deeper insight in our patient data. We evaluate our results with classification and rule performance measures. For feature selection we introduce a new importance measure.

Abdomen↗

PubMed1995

Intraarterial biocompatibility of polyethylene terephthalate self-expandable stents implanted in porcine peripheral arteries.

RATIONALE AND OBJECTIVES: We tested deployment feasibility and intraarterial biocompatibility of polyethylene terephthalate (PET) self-expandable vascular stents in a porcine peripheral artery model. METHODS: To assess the thrombogenicity and neointimal response to oversized PET self-expandable stents, we implanted 10 stents in porcine common iliac arteries, followed by a 6-mm balloon inflation to 6 atm. RESULTS: All pigs survived until the study termination 6 weeks after stent implantation. Control angiography revealed stent closure in three pigs. Minimal stent luminal diameter (MSLD) was measured using a semiautomated edge detection algorithm. The difference in MSLD after stent implantation and at control after 6 weeks was not significant (4.9 +/- 0.5 mm-->4.7 +/- 1.0 mm). Histopathologic examination showed signs of thrombotic occlusion and revascularization in occluded stents. In patient stents only a mild fibromuscular neointimal response was seen. CONCLUSION: PET self-expandable stents implanted in porcine iliac arteries are possibly thrombogenic but do not lead to a significant neointimal response.

Animals↗

PubMedDate not supplied

2D structure depiction.

A comprehensive algorithm for the depiction of 2D coordinates of chemical structures is described. The methods used represent a significant improvement to the state of the art with regard to molecular connection graphs which pose particular difficulty to most layout efforts. Resulting coordinates are consistently of publication quality for a large subset of chemistry. The algorithm is discussed in detail, and measurements of its overall success are presented.

Journal Article↗

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↗

PubMed2006

Measurement of brain metabolites in patients with type 2 diabetes and major depression using proton magnetic resonance spectroscopy.

Type 2 diabetes and major depression are disorders that are mutual risk factors and may share similar pathophysiological mechanisms. To further understand these shared mechanisms, the purpose of our study was to examine the biochemical basis of depression in patients with type 2 diabetes using proton MRS. Patients with type 2 diabetes and major depression (n=20) were scanned along with patients with diabetes alone (n=24) and healthy controls (n=21) on a 1.5 T MRI/MRS scanner. Voxels were placed bilaterally in dorsolateral white matter and the subcortical nuclei region, both areas important in the circuitry of late-life depression. Absolute values of myo-inositol, creatine, N-acetyl aspartate, glutamate, glutamine, and choline corrected for CSF were measured using the LC-Model algorithm. Glutamine and glutamate concentrations in depressed diabetic patients were significantly lower (p<0.001) in the subcortical regions as compared to healthy and diabetic control subjects. Myo-inositol concentrations were significantly increased (p<0.05) in diabetic control subjects and depressed diabetic patients in frontal white matter as compared to healthy controls. These findings have broad implications and suggest that alterations in glutamate and glutamine levels in subcortical regions along with white matter changes in myo-inositol provide important neurobiological substrates of mood disorders.

Adult↗

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↗

PubMed2002

Study of the three-dimensional geometry of the central conducting airways in man using computed tomographic (CT) images.

Clinical research on the deposition of inhaled substances (e.g. inhaled medications, airborne contaminants, fumes) in the lungs necessitates anatomical models of the airways. Current conducting airway models lack three-dimensional (3D) reality as little information is available in the literature on the distribution of the airways in space. This is a limitation to the assessment or predictions of the particle deposition in relation to the subject's anatomy. Detailed information on the full topology and morphology of the airways is thus required to model the airway tree realistically. This paper presents the length, diameter, gravity, coronal and sagittal angles that together describe completely the airways in 3D space. The angle at which the airways branch out from their parent (branching angle) and the rotation angle between successive bifurcation planes are also included. These data are from the study of two sets of airways computed tomography (CT) images. One CT scan was performed on a human tracheobronchial tree cast and the other on a healthy male volunteer. The airways in the first nine generations of the cast and in the first six conducting generations of the volunteer were measured using a computer-based algorithm. The data contribute to the knowledge of the lung anatomy. In particular, the spatial structure of the airways is shown to be strongly defined by the central airways with clear angular lobar patterns. Such patterns tend to disappear with a mean gravity, coronal and sagittal angles of 90 degrees in each generation higher than 13-15. The mean branching angle per generation appears independent of the lobe to which the airways belong. Non-planar geometry at bifurcation is observed with the mean (+/- SD) bifurcation plane rotation angle of 79 +/- 410 (n = 229). This angle appears constant over the generations studied. The data are useful for improving the 3D realism of the conducting airway structure modelling as well as for studying aerosol deposition, flow and biological significance of non-planar airway trees using analytical and computational flow dynamics modelling.

Adult↗

PubMed2003

Bachmann's bundle versus right atrial appendage capture.

The tissue in the high intraatrial septum in the region of Bachmann's Bundle (BB) exhibits electrophysiological properties that differ from the right atrial appendage (RAA). As BB pacing emerges as an alternative to RAA pacing, the feasibility of using automatic capture recognition technology in this location should be examined. At implant, active-fixation leads were consecutively placed in the RAA, then the BB in 18 patients (55.5% men, mean age 77.1 +/- 9.1). There was no significant difference between BB and RAA in the average capture threshold (1.12 vs 1.77 V, P = 0.09), sensing threshold (3.85 vs 3.69 mV, P = 0.84), impedance (508 vs 529 Ohms, P = 0.64), evoked response (1.78 vs 1.67 mV, P = 0.83), and polarization (0.41 vs 0.46 mV, P = 0.84) between. The difference in tissue characteristics was not associated with a different evoked response measured by the ventricular capture recognition algorithm. Based on the analogous evoked response and polarization values, capture recognition technology designed for the atrium will most likely be applicable at both pacing sites.

Aged↗

PubMed2000

Improving the quality of postoperative pain relief.

A review of the literature shows a constant need to improve the quality of postoperative pain management. The objective of this study was to decrease the intensity and variation of postoperative pain by developing a nurse-based pain service on the ward. An acute pain nurse was appointed and an educational programme with detailed algorithms was started. Regular pain intensity measurements were implemented. Postoperative pain intensity, treatments and side-effects were assessed both before and after the introduction of the new system in 400 patients divided into two consecutive groups of equal size. The number of patients with inadequately treated pain (actual pain > 3/10) dropped by 64% after major gynaecological surgery (25 vs 9%, 95% CI for differences 7-24%; p<0.001 for pain scores). On an average, inadequate pain relief (retrospective average pain > 3/10) on the first postoperative day was more frequent on the ward before than after the reform (47 vs. 21%; 95% CI for differences 15-35%; p<0.001 for pain scores). The incidence of side-effects was similar in both groups (p> 0.05). The intensity and variation of postoperative pain on the ward decreased by developing a nurse-based pain service with an acute pain nurse, an educational programme and regular pain intensity measurements.

Activities of Daily Living↗

PubMed2000

The role of the D-dimer in the diagnosis of venous thromboembolism.

Classic enzyme-linked immunosorbent assay (ELISA) D-dimer assays are sensitive in screening for thromboembolic disease; however, they are cumbersome and time consuming to perform, which limits their routine use. Latex agglutination assays are easier to perform, but they are not as sensitive as the ELISA assays. New D-dimer assays incorporating novel technologies can be performed rapidly with a sensitivity approaching that of classic ELISA assays. D-dimer assays are uniformly sensitive in detecting thromboembolic disease in different patient populations; however, low specificity limits the clinical utility of D-dimer measurements in medical inpatients and postoperative patients. Increasingly, these measurements are being incorporated into diagnostic algorithms for venous thromboembolism and are reducing the need for invasive diagnostic studies.

Journal Article↗

PubMed2006

[Management of abnormal uterine bleeding].

Bleeding disorders are one of the most frequent gynecological problems. The causes of bleeding disorders, and their frequency in particular, vary depending on the age of the woman affected. In premenopause and perimenopause, the most frequent causes are hormonal, in up to 90 % of cases, as well as organic changes in the uterus such as myomas, adenomyosis uteri, or endometrial polyps, in up to 70 % of cases. Coagulation defects cause increased bleeding, particularly in girls and young women, with no other recognizable cause. The treatment of bleeding disorders is causally based, although if the woman does not wish to have children, the therapeutic algorithm in many cases leads to similar symptomatic measures. The following therapeutic approaches, listed in order of increasing efficacy, are mainly used in the treatment of increased bleeding: gestagen, estrogen-gestagen combination, levonorgestrel (Mirena) and endometrial ablation or myoma enucleation, with comparable success rates, and finally hysterectomy. Embolization of the uterine artery in myomas or adenomyosis uteri, nonsteroidal anti-inflammatory drugs, and antifibrinolytic agents represent alternatives that may be useful in individual cases. The paper provides an overview of the various causes, useful diagnostic measures, and treatment options in uterine bleeding disorders.

Algorithms↗

PubMed2001

An analysis of neural receptive field plasticity by point process adaptive filtering.

Neural receptive fields are plastic: with experience, neurons in many brain regions change their spiking responses to relevant stimuli. Analysis of receptive field plasticity from experimental measurements is crucial for understanding how neural systems adapt their representations of relevant biological information. Current analysis methods using histogram estimates of spike rate functions in nonoverlapping temporal windows do not track the evolution of receptive field plasticity on a fine time scale. Adaptive signal processing is an established engineering paradigm for estimating time-varying system parameters from experimental measurements. We present an adaptive filter algorithm for tracking neural receptive field plasticity based on point process models of spike train activity. We derive an instantaneous steepest descent algorithm by using as the criterion function the instantaneous log likelihood of a point process spike train model. We apply the point process adaptive filter algorithm in a study of spatial (place) receptive field properties of simulated and actual spike train data from rat CA1 hippocampal neurons. A stability analysis of the algorithm is sketched in the. The adaptive algorithm can update the place field parameter estimates on a millisecond time scale. It reliably tracked the migration, changes in scale, and changes in maximum firing rate characteristic of hippocampal place fields in a rat running on a linear track. Point process adaptive filtering offers an analytic method for studying the dynamics of neural receptive fields.

Adaptation, Physiological↗

PubMed2000

A jigsaw puzzle theory of memory.

The principal novel feature of this paper is the notion that a coherent memory can be synthesised from a set of partially coherent memory fragments by maximising a particular function, Harmony (Smolensky, 1986). The appeal of Harmony is that it fulfils two functions: it is at the heart of the synthesis algorithm and it provides a natural measure for "feeling-of-knowing". The model is applied to feeling-of-knowing data, flashbulb memories, flashbacks, repression, dissociation, memory stability across repeated recalls, and the effects of cue size on retrieval.

Cues↗

PubMedDate not supplied

The effect on speech intelligibility of varying compression time constants in a digital hearing aid.

The identification of nonsense syllables in quiet and in three types of background (babble, cafeteria and single female speaker) was measured using four hearing aid compression algorithms differing in attack and release time constants, and using linear amplification. The speech level was always 65 dB SPL. The compression algorithms, which were implemented in a Phonak Claro ITE hearing aid, were: (1) 'very fast'--the attack time was 8 ms and the release time was 32 ms, for all 20 channels; (2) 'slow-fast'--the attack and release times decreased from 500 ms for low frequencies to about lOOms for high frequencies; (3) 'fast-slow'-the attack and release times increased from about 50ms for low frequencies to 500 ms for high frequencies; and (4) 'slow + fast'-a very slow-acting gain control signal was combined with a fast-acting gain control signal, for each channel in a 10-channel system. Acoustical stimuli were presented monaurally via a circumaural headphone mounted over the hearing aid. The linear condition did not use the Claro aid; instead, the signal was digitally filtered to implement the Cambridge formula prior to delivery via the earphone. Five subjects with moderate sensorineural hearing loss were tested in a counter-balanced order across conditions. In quiet, performance was best for linear amplification and worst for the slow + fast algorithm. In the presence of background sounds, the highest scores were obtained with the linear-gain Cambridge formula implemented via headphones; a supplementary experiment suggested that this was due to the greater high-frequency gain resulting from the use of this formula. No significant differences were found between scores for the different compression algorithms. We conclude that the intelligibility of speech at a fixed level, presented in background sounds, is not markedly affected by rather substantial variations of the time constants in a multichannel compression system.

Aged↗

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↗

PubMed1997

Magnetic fields from domestic appliances in the UK.

In a survey of 50 UK homes the 50 Hz fundamental and harmonic magnetic fields generated by 806 domestic appliances found in the homes, and used regularly by mothers, were measured. Measurements were made in the direction of most likely access, and from the surface of the appliances. Mothers completed a questionnaire on the use of appliances and were monitored for 24 h so that acquired exposure could be compared with the measured ambient fields in the home. Appliances were measured at standard distances and an algorithm was used to calculate fields at 100 and 50 cm to remove room background contributions. A few appliances generated fields in excess of 0.2 microT at 1 m: microwave cookers 0.37 +/- 0.14 microT; washing machines 0.27 +/- 0.14 microT; dishwashers 0.23 +/- 0.13 microT; some electric showers 0.11 +/- 0.25 microT and can openers 0.20 +/- 0.21 microT. Of continuously operating devices, only central heating pumps (0.51 +/- 0.47 microT), central heating boilers (0.27 +/- 0.26 microT) and fish-tank air pumps (0.32 +/- 0.09 microT) produced significant fields at 0.5 m. There were no obvious ways to group different types of appliances as high- or low-strength sources. Mothers spent on average about 4.5 h per day in the kitchen, where the strongest sources of magnetic field were located.

Algorithms↗

PubMed2003

Attenuation and scatter correction for in-beam positron emission tomography monitoring of tumour irradiations with heavy ions.

An in-beam dual-head positron camera is used to monitor the dose application in situ during the tumour irradiation with carbon ion beams at the experimental heavy ion therapy facility at GSI Darmstadt. Therefore, a positron emission tomograph has been mounted directly at the treatment site. A fully 3D reconstruction algorithm based on the maximum likelihood expectation maximization (MLEM) algorithm has been developed and adapted to this spatially varying imaging situation. The scatter and attenuation correction are included in the forward projection step of the maximum likelihood image reconstruction. This requires an attenuation map containing the information on the material composition and densities. This information is derived from the x-ray computed tomograms of the patient and the patient fixation system including the head-rest. The normalization of scattered events relative to the unscattered events is done by a global scatter fraction factor which is estimated by means of a Monte Carlo simulation. The feasibility of the proposed algorithm is shown by means of computer simulations, phantom measurements as well as patient data.

Algorithms↗