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At least 1,531 records · Page 85Linked to original sources
PubMedDate not supplied

Exposure and organ dose estimation in diagnostic radiology.

This paper discusses a methodology which uses a specially developed computer program that enables estimation of output parameters of an x-ray machine from a single test exposure. Exposure at skin entrance values can be estimated, as well as using the data from the program for organ dose estimates. To perform the estimation procedure, curves and analytical expressions for the curves are presented for conversion of half-value layers to total filtration and for conventional mR/mAs output curves. Results are given showing that the estimation procedure is reasonably accurate.

Humans↗
PubMed1999

Neocognitron's parameter tuning by genetic algorithms.

The further study on the sensitivity analysis of Neocognitron is discussed in this paper. Fukushima's Neocognitron is capable of recognizing distorted patterns as well as tolerating positional shift. Supervised learning of the Neocognitron is fulfilled by training patterns layer by layer. However, many parameters, such as selectivity and receptive fields are set manually. Furthermore, in Fukushima's original Neocognitron, all the training patterns are designed empirically. In this paper, we use Genetic Algorithms (GAs) to tune the parameters of Neocognitron and search its reasonable training pattern sets. Four contributions are claimed: first, by analyzing the learning mechanism of Fukushima's original Neocognitron, the correlations amongst the training patterns are claimed to affect the performance of Neocognitron, tuning the Neocognitron's number of planes is equivalent to searching reasonable training patterns for its supervised learning; second, a GA-based supervised learning of the Neocognitron is carried out in this way, searching the parameters and training patterns by GAs but specifying the connection weights by training the Neocognitron; third, other than traditional GAs which are unsuitable for the large searching space of training patterns set, the cooperative coevolution is incorporated to play this role; fourth, an effective fitness function is given out when applying the above methodology into numeral recognition. The evolutionary computation in our initial experiments is implemented based on the original training pattern set, e.g. the individuals of the population are generated from Fukushima's original training patterns during initialization of GAs. The results prove that our correlation analysis is reasonable, and show that the performance of a Neocognitron is sensitive to its training patterns, selectivity and receptive fields, especially, the performance is not monotonically increasing with respect to the number of training patterns, and this GA-based supervised learning is able to improve Neocognitron's performance.

Cognition↗
PubMed1992

Impact of drug use evaluation upon ambulatory pharmacy practice.

OBJECTIVE: To review the expansion of ambulatory drug use evaluation (DUE). A description of ambulatory DUE characteristics and methodology is included. In addition, DUE computer usage, documentation concerns, and future research issues are addressed. DATA SOURCES: A MEDLINE search was used to identify pertinent literature, including reviews. STUDY SELECTION: Primary and secondary literature describing ambulatory DUE was selected. Articles describing inpatient DUE were excluded. DATA EXTRACTION: Rigorous studies evaluating current ambulatory DUE programs are limited, but the available literature and a description of existing program characteristics are included. All studies available at the time of publication were reviewed. DATA SYNTHESIS: Ambulatory DUE can provide useful information to assist in providing pharmaceutical care. The Omnibus Budget Reconciliation Act of 1990 has prompted an expansion of DUE programs, and most of the formalized programs are retrospective in design. Prospective programs provide online, patient-specific drug use assessment whenever new prescriptions are entered into point-of-service databases. CONCLUSIONS: Although more well-designed evaluations of existing ambulatory DUE programs are needed, initial results indicate these programs may be extremely useful in identifying significant medication therapy problems and improving patients' drug therapy.

Ambulatory Care↗
PubMed2004

Evolutionary fuzzy modeling human diagnostic decisions.

Fuzzy CoCo is a methodology, combining fuzzy logic and evolutionary computation, for constructing systems able to accurately predict the outcome of a human decision-making process, while providing an understandable explanation of the underlying reasoning. Fuzzy logic provides a formal framework for constructing systems exhibiting both good numeric performance (accuracy) and linguistic representation (interpretability). However, fuzzy modeling--meaning the construction of fuzzy systems--is an arduous task, demanding the identification of many parameters. To solve it, we use evolutionary computation techniques (specifically cooperative coevolution), which are widely used to search for adequate solutions in complex spaces. We have successfully applied the algorithm to model the decision processes involved in two breast cancer diagnostic problems, the WBCD problem and the Catalonia mammography interpretation problem, obtaining systems both of high performance and high interpretability. For the Catalonia problem, an evolved system was embedded within a Web-based tool-called COBRA-for aiding radiologists in mammography interpretation.

Breast Neoplasms↗
PubMed2003

Development of a clinical data warehouse for hospital infection control.

Existing data stored in a hospital's transactional servers have enormous potential to improve performance measurement and health care quality. Accessing, organizing, and using these data to support research and quality improvement projects are evolving challenges for hospital systems. The authors report development of a clinical data warehouse that they created by importing data from the information systems of three affiliated public hospitals. They describe their methodology; difficulties encountered; responses from administrators, computer specialists, and clinicians; and the steps taken to capture and store patient-level data. The authors provide examples of their use of the clinical data warehouse to monitor antimicrobial resistance, to measure antimicrobial use, to detect hospital-acquired bloodstream infections, to measure the cost of infections, and to detect antimicrobial prescribing errors. In addition, they estimate the amount of time and money saved and the increased precision achieved through the practical application of the data warehouse.

Blood-Borne Pathogens↗
PubMed1999

Relation of education to brain size in normal aging: implications for the reserve hypothesis.

OBJECTIVE: To examine the relations between education and age-related changes in brain structure in a nonclinical sample of elderly adults. BACKGROUND: Education may protect against cognitive decline in late life--an observation that has led to the "reserve" hypothesis of brain aging. Little is known, however, about the effect of education on age-related changes in brain structure. METHODS: Quantitative MRI of the brain was performed in 320 elderly volunteers (age range, 66 to 90 years) living independently in the community (Mini-Mental State Examination scores > or =24), all of whom were participants in the Cardiovascular Health Study. Blinded measurements of global and regional brain size were made from T1-weighted axial images using computer-assisted edge detection and trace methodology. High measurement reliabilities were obtained. RESULTS: Regression analyses (adjusting for the effects of intracranial size, sex, age, age-by-sex interactions, and potential confounders) revealed significant main effects of education on peripheral (sulcal) CSF volume-a marker of cortical atrophy. Each year of education was associated with an increase in peripheral CSF volume of 1.77 mL (p<0.03). As reported previously, main effects of age (but not education) were observed for all of the remaining brain regions examined, including cerebral hemisphere volume, frontal region area, temporoparietal region area, parieto-occipital region area, lateral (Sylvian) fissure volume, lateral ventricular volume, and third ventricle volume. CONCLUSIONS: The authors' findings demonstrate a relation between education and age-related cortical atrophy in a nonclinical sample of elderly persons, and are consistent with the reserve hypothesis as well as with a small number of brain imaging studies in patients with dementia. The neurobiological basis and functional correlates of this education effect require additional investigation.

Aged↗
PubMed2004

Reduction of computation time for crossed-grating problems: a group-theoretic approach.

A systematic approach based on group theory is established to deal with diffraction problems of crossed gratings by exploiting symmetries. With this approach, a problem in an asymmetrical incident mounting can be decomposed into a superposition of several symmetrical basis problems so that the computation efficiency is improved effectively. This methodology offers a convenient and succinct way to treat all possible symmetry cases by following only several mechanical steps instead of intricate mathematical considerations or physical intuition. It is also general, applicable to both scalar-wave and vector-wave problems and in principle can be easily adapted to any numerical method. A numerical example is presented to show its application and effectiveness.

Journal Article↗
PubMed2005

Bioinformatics approaches for detecting gene-gene and gene-environment interactions in studies of human disease.

Neurological and mental disorders occur often, with approximately 450 million people suffering from them worldwide. Like most other common diseases, neurological disorders are hypothesized to be highly complex, with interactions among genes and risk factors playing a major role in the process. In recent years it has become obvious that for common diseases there may be more complex interactions among genes with and without strong independent main effects. These effects are more difficult to detect using traditional methodologies. In this manuscript the author introduces the concept of epistasis and the challenges associated with detecting it. Next, she briefly mentions a number of bioinformatics approaches that have been developed to deal with this issue. Multifactor dimensionality reduction is a methodology developed specifically to deal with the challenge of detecting interaction effects in the absence of statistically detectable main effects in studies of common disorders, such as Alzheimer disease or brain cancer. Finally, the author describes the future directions for this technique and related methodologies.

Computational Biology↗
PubMed2005

Effectiveness of a return-to-work intervention for subacute low-back pain.

The effectiveness of return-to-work intervention for subacute low-back pain on work absenteeism, pain severity, and functional status was examined by means of a systematic review of randomized controlled trials. Publications in English that met the selection criteria were identified in a computer-aided search and assessed for methodological quality. A best-evidence synthesis was performed instead of statistical data pooling, because of the heterogeneity of the interventions and study populations. Five of nine studies comparing return-to-work intervention with usual care were identified as methodologically high-quality studies. Strong evidence was found for the effectiveness of return to work intervention on the return-to-work rate after 6 months and for the effectiveness of return-to-work intervention on the reduction of days of absence from work after > or = 12 months. It can be concluded that return-to-work interventions are equal or more effective regarding absence from work due to subacute low-back pain than usual care is.

Behavior Therapy↗
PubMed2005

US, MRCP, CCT and ERCP: a comparative study in 131 patients with suspected biliary obstruction.

BACKGROUND: Recent years have witnessed a rapid and continuous evolution in the diagnosis of biliary obstructive disease. Traditional methodologies, such as US (ultrasonography), CT (computed tomography), ERCP (endoscopic retrograde cholangiopancreatography) and PTC (percutaneous transhepatic cholangiography), have been supplemented by MRCP (magnetic resonance cholagiopancreatography) and CCT (cholangio computed tomography) The purpose of our study was to compare the reliability of diagnostic US, MR and other imaging techniques in intrinsic biliary obstructive disease. MATERIAL/METHODS: Between June 1999 and July 2003 we conducted a prospective study on 131 patients--60 males and 71 females--ranging in age from 37 to 79 years, with clinical features of biliary obstructive disease. Imaging studies were done on each patient using several different techniques. The US, MRCP, CCT and ERCP results were read by radiologists blinded to other imaging findings. RESULTS: US is generally accurate in diagnostic imaging of obstructive biliary disease. MRCP and CCT are significantly more accurate only in completing the staging of malignant stenosis. CONCLUSIONS: If the suspicion posed by clinical and laboratory findings is not confirmed at US, the diagnosis must be achieved with the aid of MRCP or--where MRCP does not provide a diagnosis--CCT, so as to select candidates for therapeutic ERCP, PTC or surgery. If laboratory and clinical findings are supported by US, ERCP is required for therapeutic purposes, or--if necessary--surgery is performed.

Adult↗
PubMedDate not supplied

Analysing qualitative research data using computer software.

An increasing number of clinical nurses are choosing to undertake qualitative research. A number of computer software packages are available designed for the management and analysis of qualitative data. However, while it is claimed that the use of these programs is also increasing, this claim is not supported by a search of recent publications. This paper discusses the advantages and disadvantages of using computer software packages to manage and analyse qualitative data.

Attitude of Health Personnel↗
PubMed1994

Short-term, within-person variability in clinical chemistry test results. Experience from the Atherosclerosis Risk in Communities Study.

We report the within-person, between-person, and methodological variances of a number of chemical analytes for free-living, middle-aged adults who participated in the Atherosclerosis Risk in Communities Study's Intraindividual Variability Study. The Atherosclerosis Risk in Communities Study is a National Institutes of Health-sponsored multicenter study of atherosclerotic risk factors. In the Atherosclerosis Risk in Communities Study and its Intraindividual Variability Study, concentrations of the following 12 chemical analytes were measured in serum from fasting individuals: sodium, calcium, potassium, creatinine, albumin, total protein, magnesium, phosphorus, urea, insulin, glucose, and urate. The analytes are listed in order of the increasing reliability coefficient (ie, the fraction that between-person variance represents of the total observed population variance), which ranged from .59 for sodium to .91 for urate. The reliability coefficient is a strong predictor of the possibility of finding statistical correlations between measured analyte concentrations and disease occurrence in an epidemiological study like the Atherosclerosis Risk in Communities Study. The within-person variance and methodological variance are also useful in computing confidence intervals for sequential laboratory test results in patients and evaluating limits for internal quality control and proficiency testing programs.

Aged↗
PubMed1993

Power spectral analysis of heart rate variability: a noninvasive signature of cardiac autonomic function.

Power spectral analysis of short segments of beat-to-beat heart rate variability (PS/HRV) reveals three distinct peaks. In human PS/HRV, the high frequency (HF) band (0.15 to 0.4 Hz) is correlated with respiratory driven vagal efferent input to the sinus node. The low frequency band (LF) 0.06 to 0.15 Hz is believed to be due to baroreceptor mediated blood pressure control. Therefore, PS/HRV represents a noninvasive signature of the balance between sympathetic and parasympathetic components of the autonomic nervous system. This paper reviews the literature on the methodological issues relevant to signal processing, computational, and clinical applications of PS/HRV. Factors affecting the power in the LF and HF bands are examined in healthy controls. Recent work from several laboratories suggests that PS/HRV is a potentially powerful tool for exploring neurocardiac dysfunction in patients with a variety of cardiac and autonomic disorders. Mathematical models which simulate neurocardiac control are examined. Concerns regarding the lack of standardization between different laboratories are expressed. As the PS/HRV attains the status of a clinical diagnostic test, we hope that this review serves as a source of integrated information for researchers in this field.

Adult↗
PubMed1995

Effect of the environment and role of the pi-pi stacking interactions in the stabilization of the 3(10)-helix conformation in dehydroalanine oligopeptides.

A quantum-mechanical study of the chain-length dependent stability of the extended, 2(7)-ribbon and 3(10)-helix conformations in dehydroalanine (delta Ala) oligopeptides has been performed. To address the study, the oligopeptides delta Ala(n), where n varies from 1 to 6, were computed by using the semiempirical AMI methodology. Cooperative free-energy effects permit one to predict the stabilization of the 3(10)-helix with respect to the extended and 2(7)-ribbon conformations when the number of residues in the polypeptide chain increases. The interactions associated with the pi-electron density of the side chains can easily explain this finding. The effects of the solvent and the crystalline packing on the different conformations were modeled using a self-consistent reaction field (SCRF) method and a molecular mechanics approach to the packing, respectively. Both the aqueous and crystal environments seem to be a key factor in the stabilization of the helical conformation. Finally, the variations of electrostatic parameters such as atomic point charges and dipole moments in delta Ala-containing peptides with internal (conformation) and external (solvent) effects are discussed.

Alanine↗
PubMed1996

[Heart rate and blood pressure variability: analytical methods, physiological significance, and its applications].

This paper reviews the literature on the methodological issues relevant to signal processing, computation, and clinical applications of heart rate (HR) and blood pressure (BP) variability. Linear techniques for both single signal and relations between the signals, and clinical role of HRV and BPV analysis are examined. Some recent studies in this field are also mentioned.

Animals↗