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PubMed2006

Microvascular stress analysis. Part I: simulation of microvascular anastomoses using finite element analysis.

PURPOSE OF THE STUDY: To develop a finite element model (FEM) to study the effect of the stress and strain, in microvascular anastomoses that result from the geometrical mismatch of anastomosed vessels. MATERIAL AND METHODS: FEMs of end-to-end and end-to-side anastomoses were constructed. Simulations were made using finite element software (NISA). We investigated the angle of inset in the end-to-side anastomosis and the discrepancy in the size of the opening in the vessel between the host and recipient vessels. The FEMs were used to predict principal and shear stress and strain at the position of each node. RESULTS: Two types of vascular deformation were predicted during different simulations: longitudinal distortion, and rotational distortion. Stress values ranged from 151.1 to 282.4MPa for the maximum principal stress, from -122.9 to -432.2MPa for the minimum principal stress, and from 122.1 to 333.1MPa for the maximum shear stress. The highest values were recorded when there was a 50% mismatch in the diameter of the vessels at the site of the end-to-end anastomosis. CONCLUSION: The effect of the vessel's size discrepancy on the blood flow and deformation was remarkable in the end-to-end anastomosis. End-to-side anastomosis was superior to end-to-end anastomosis. FEM is a powerful tool to study vascular deformation, as it predicts deformation and biomechanical processes at sites where physical measurements are likely to remain impossible in living humans.

Anastomosis, Surgical↗

PubMed2006

Vitamin D status and bone mass in UK South Asian women.

INTRODUCTION: Low vitamin D status is prevalent among South Asians living in the UK. The relationship, however, between serum 25-hydroxyvitamin D level (25OHD), serum parathyroid level (PTH) and bone mass in this group of women is unknown. The aim of this study was to determine the association between serum PTH, 25OHD and bone mass in a population based sample of young UK South Asian women. MATERIALS AND METHODS: Names of South Asian women aged 18 to 36 years of Pakistani origin living in the Greater Manchester area were identified from primary care registers using validated computer software. Subjects were invited to attend for (i) a blood test for assessment of serum calcium (Ca), albumin, PTH and 25OHD and (ii) for bone mineral density (BMD) scanning using the following: areal BMD at the hip (femoral neck, total hip) and lumbar spine using dual X-ray absorptiometry (Hologic QDR 4500), and volumetric BMD at the distal radius using peripheral quantitative computed tomography (Norland Stratec XCT 2000). Linear regression was used to determine the association between serum 25OHD, PTH and BMD at the different sites with adjustments made for age. RESULTS: In all, 78 women (mean age 29.2 years) were included in the analysis. Mean serum Ca level was 2.42 mmol/l, 25OHD, 7.9 ng/ml and PTH, 52.8 pg/ml. The majority of women (94%) had serum 25OHD levels 15 ng/ml, though rose progressively in subjects with levels below 10 ng/ml. Serum 25OHD was positively associated with BMD at the hip and spine while PTH was negatively associated with BMD at the hip and spine. When categorized by serum 25OHD level there was an increase in BMD at the total hip and distal radial site at least up to levels of 15 ng/ml. CONCLUSIONS: Despite widespread recognition, hypovitaminosis D is still prevalent among young UK South Asian women. In these women a decrease in serum 25OHD level <or=15 ng/ml is associated with a progressive reduction in bone mass at the hip and wrist.

Adolescent↗

PubMed2005

An evaluation of automated neonatal seizure detection methods.

OBJECTIVE: To evaluate 3 published automated algorithms for detecting seizures in neonatal EEG. METHODS: One-minute, artifact-free EEG segments consisting of either EEG seizure activity or non-seizure EEG activity were extracted from EEG recordings of 13 neonates. Three published neonatal seizure detection algorithms were tested on each EEG recording. In an attempt to obtain improved detection rates, threshold values in each algorithm were manipulated and the actual algorithms were altered. RESULTS: We tested 43 data files containing seizure activity and 34 data files free from seizure activity. The best results for Gotman, Liu and Celka, respectively, were as follows: sensitivities of 62.5, 42.9 and 66.1% along with specificities of 64.0, 90.2 and 56.0%. CONCLUSIONS: The levels of performance achieved by the seizure detection algorithms are not high enough for use in a clinical environment. The algorithm performance figures for our data set are considerably worse than those quoted in the original algorithm source papers. The overlap of frequency characteristics of seizure and non-seizure EEG, artifacts and natural variances in the neonatal EEG cause a great problem to the seizure detection algorithms. SIGNIFICANCE: This study shows the difficulties involved in detecting seizures in neonates and the lack of a reliable detection scheme for clinical use. It is clear from this study that while each algorithm does produce some meaningful information, the information would only be usable in a reliable neonatal seizure detection process when accompanied by more complex analysis, and more advanced classifiers.

Action Potentials↗

PubMed2006

SCEW: a Microsoft Excel add-in for easy creation of survival curves.

Survival curves are frequently used for reporting survival or mortality outcomes of experimental pharmacological/toxicological studies and of clinical trials. Microsoft Excel is a simple and widely used tool for creation of numerous types of graphic presentations however it is difficult to create step-wise survival curves in Excel. Considering the familiarity of clinicians and biomedical scientists with Excel, an algorithm survival curves in Excel worksheet (SCEW) has been developed for easy creation of survival curves directly in Excel worksheets. The algorithm has been integrated in the form of Excel add-in for easy installation and usage. The program is based on modification of frequency data for binary break-up using the spreadsheet formula functions whereas a macro subroutine automates the creation of survival curves. The advantages of this program are simple data input, minimal procedural steps and the creation of survival curves in the familiar confines of Excel.

Algorithms↗

PubMed2004

Retrieving definitional content for ontology development.

Ontology construction requires an understanding of the meaning and usage of its encoded concepts. While definitions found in dictionaries or glossaries may be adequate for many concepts, the actual usage in expert writing could be a better source of information for many others. The goal of this paper is to describe an automated procedure for finding definitional content in expert writing. The approach uses machine learning on phrasal features to learn when sentences in a book contain definitional content, as determined by their similarity to glossary definitions provided in the same book. The end result is not a concise definition of a given concept, but for each sentence, a predicted probability that it contains information relevant to a definition. The approach is evaluated automatically for terms with explicit definitions, and manually for terms with no available definition.

Bayes Theorem↗

PubMed2005

Evaluation frameworks for nursing informatics.

Rigorous evaluation of informatics applications in healthcare is important so that the impact of such systems can be understood. Although many quantitative methods have been employed to evaluate informatics systems, there is a growing trend to utilized qualitative methods during both the formative and summative phases of research. Several evaluation frameworks that have been proposed highlight the need for both qualitative and quantitative evaluation methods in the development and post-implementation phases of informatics systems development. Recommendations regarding the timing, type and use of qualitative methods differ for each of these frameworks. This paper examines the strengths and weaknesses of the published evaluation frameworks and enumerates the qualitative research methods in use in each of these frameworks.

Nursing Informatics↗

PubMed2005

Evaluation of teleconsultation systems.

The aim of this study was to identify criteria used for evaluation of teleconsulatation systems in evaluation studies, and to estimate trend of their changes. Evaluation of teleconsultation (TC) systems was made on the basis of 82 evaluation studies from the inventory of evaluation studies in medical informatics consisting of all the information and communication technology (ICT) evaluation studies published in 1982-2002. In order to estimate trend of changes in using evaluation criteria, the whole period with at least one evaluation study, it means the period of 1995-2002 was divided to 2 of 4 years, 1995-1998 and 1999-2002. Proportions of evaluation studies according to any single criterion were calculated. Index of changes I(ci) for ith criterion was defined as difference of proportion of studies evaluating teleconsultation by using a certain criterion in the second period and the same proportion in the first period divided by the number of all studies evaluating teleconsultation systems. This research showed that hardware and technical aspects were the leading evaluation criterion, but it has been decreasing (from 74.2% in the first period to 43.1% in the second one). Satisfactions of both health care provider and patient achieved the highest increase in the second period (from 3.2 to 19.6% and from 0 to 15.7%, respectively). Appropriateness and cost of patient care were on the second place (from 22.6 to 33.3% and from 16.1 to 23.5%, respectively). Considering defined index of changes it can be concluded that there are four criteria for evaluation of teleconsultation systems, having a positive trend (in frequency of evaluation studies): user satisfaction (Ic=0.20), satisfaction of patient with patient care (Ic=0.19), appropriateness of patient care (Ic=0.13) and cost of patient care (Ic=0.09). Hardware and technical aspects shows negative trend in the number of evaluation studies (Ic=-0.38), as well as cost of IT (Ic=-0.10).

Biotechnology↗

PubMed2005

Dolphin Imaging Software: an analysis of the accuracy of cephalometric digitization and orthognathic prediction.

The purpose of this study was to examine and compare the reproducibility and reliability of digitization using Dolphin Imaging Software (Version 8.0) with traditional manual techniques. In addition, orthognathic prediction was compared with actual outcomes. Sixty lateral cephalograms were evaluated by two methods: manual tracing and indirect digitization using Dolphin Imaging Software (Version 8.0). Method error (reliability) using duplicate measurements for each method, and comparison of both techniques (reproducibility), were investigated using alternative statistical methods, Bland and Altman (1986) and Lin's Correlation of Concordance (1989). Each technique was significantly reliable at the 95% level (method error). Comparing the standard deviations of the differences, manual tracing proving more reliable for SNA (1.36 degrees manually, 2.07 degrees digitally), SNB (1.19 degrees and 1.69 degrees ), SNMx (1.39 degrees and 2.66 degrees ), and MxMd (1.77 degrees and 2.26 degrees ), and Dolphin digital tracing more reliable for UIMx (3.49 degrees digitally and 3.97 degrees manually) and LIMd (2.90 degrees and 3.04 degrees ). However, systematic error in the software's calculation of LAFH% resulted in measurements 4% larger than manual techniques, a difference which is clinically significant. Comparison of actual outcome and software generated prediction for 26 orthognathic cases demonstrated clinically significant differences for all measurements (rhoc 0.32 for ANB to 0.91 for LIMd; P<0.05). The investigation revealed the impact of radiographic magnification when used in an uncalibrated system. These findings indicate that Version 8.0 of Dolphin Imaging Software needs to be re-assessed for software errors that may result in clinically significant miscalculations, and to facilitate compensation of radiographic magnification when using linear measurements.

Cephalometry↗

PubMed2004

Cognitive and usability engineering methods for the evaluation of clinical information systems.

Increasingly healthcare policy and decision makers are demanding evidence to justify investments in health information systems. This demand requires an adequate evaluation of these systems. A wide variety of approaches and methodologies have been applied in assessing the impact of information systems in health care, ranging from controlled clinical trials to use of questionnaires and interviews with users. In this paper we describe methodological approaches which we have applied and refined for the past 10 years for the evaluation of health information systems. The approaches are strongly rooted in theories and methods from cognitive science and the emerging field of usability engineering. The focus is on assessing human computer interaction and in particular, the usability of computer systems in both laboratory and naturalistic settings. The methods described can be a part of the formative evaluation of systems during their iterative development, and can also complement more traditional assessment methods used in summative system evaluation of completed systems. The paper provides a review of the general area of systems evaluation with the motivation and rationale for methodological approaches underlying usability engineering and cognitive task analysis as applied to health information systems. This is followed by a detailed description of the methods we have applied in a variety of settings in conducting usability testing and usability inspection of systems such as computer-based patient records. Emerging trends in the evaluation of complex information systems are discussed.

Biomedical Engineering↗

PubMed2005

Using qualitative studies to improve the usability of an EMR.

The adoption of electronic medical records (EMRs) and user satisfaction are closely associated with the system's usability. To improve the usability of a results management module of a widely deployed web-based EMR, we conducted two qualitative studies that included multiple focus group and field study sessions. Qualitative research can help focus attention on user tasks and goals and identify patterns of care that can be visualized through task modeling exercises. Findings from both studies raised issues with the amount and organization of information in the display, interference with workflow patterns of primary care physicians, and the availability of visual cues and feedback. We used the findings of these studies to recommend design changes to the user interface of the results management module.

Attitude to Computers↗

PubMed2005

Heuristic evaluation of paper-based Web pages: a simplified inspection usability methodology.

Online medical information, when presented to clinicians, must be well-organized and intuitive to use, so that the clinicians can conduct their daily work efficiently and without error. It is essential to actively seek to produce good user interfaces that are acceptable to the user. This paper describes the methodology used to develop a simplified heuristic evaluation (HE) suitable for the evaluation of screen shots of Web pages, the development of an HE instrument used to conduct the evaluation, and the results of the evaluation of the aforementioned screen shots. In addition, this paper presents examples of the process of categorizing problems identified by the HE and the technological solutions identified to resolve these problems. Four usability experts reviewed 18 paper-based screen shots and made a total of 108 comments. Each expert completed the task in about an hour. We were able to implement solutions to approximately 70% of the violations. Our study found that a heuristic evaluation using paper-based screen shots of a user interface was expeditious, inexpensive, and straightforward to implement.

Computer Graphics↗

PubMed2005

Assessment of non-invasive intervertebral motion measurements in the lumbar spine.

This study compared the accuracy of new, FDA-approved, image-analysis software to conventional radiographic assessment techniques for the measurement of intervertebral motion. Six adult human cadaveric lumbar spines (L1-S1) were individually mounted in a custom Plexiglas device and electromagnetic sensors were rigidly mounted to the spinous processes of L3, L4, and L5. Lateral radiographs of the spines in neutral, full flexion, and full extension were digitized and analyzed both using the software and manually by three orthopedic surgeons. Compared to intervertebral rotations determined from the electromagnetic device, the errors in rotations reported by the software and surgeons were 0.47+/-0.24 degrees and 2.16+/-0.78 degrees , respectively. Rotations measured by the surgeons were significantly less accurate and more variable than that of the software (p<0.05).

Cadaver↗

PubMed2004

Using computerized medical databases to measure and to improve the quality of intensive care.

This article reviews the potential for using computerized databases to measure the quality of care in the intensive care unit. There are 2 types of computerized databases used to assess quality of care: administrative databases used primarily for purposes other than medical care and electronic medical record databases collected specifically for clinical purposes. Quality of care is a difficult property to measure but is generally assessed along 3 domains: structure, process, and outcome. There are several problems with using computerized medical databases to measure and improve quality of care. Many factors known to be important to measuring the severity of illness and process of care in critically ill patients are not captured in routine administrative databases. The criteria for the ethical use of electronic medical record data for research, clinical care, and quality improvement are identical to those that should be applied to using paper medical records. Standardizing a minimal intensive care unit dataset, identifying and measuring optimal processes of care, and understanding the limits of risk adjusted outcomes are all important steps in the process of the optimal use of computerized databases to study and improve the quality of care in the intensive care unit.

Confidentiality↗

PubMed2004

Clinical information systems: CareSuite from Picis.

In this article, we discuss the implementation of the CareSuite system (Picis, Wakefield, MA) in 5 intensive care units of the Erasmus Medical Center, Rotterdam, the Netherlands. We give a description of the implementation process, and the system as it is currently being used. We also confront the lessons learned during the implementation of this clinical information systems with insights from the research field of implementation, and thereby show the value of a socio-technical approach to clinical information systems implementation.

Computer Communication Networks↗

PubMed2005

Development of an automated Selvester Scoring System for estimating the size of myocardial infarction from the electrocardiogram.

Although the Selvester Scoring System for estimating the size of myocardial infarction from the standard 12-lead electrocardiogram (ECG) has potential clinical value, it has found limited application because of the difficulties in making precise and reproducible measurements. The objective of this study was to develop software to automate the Selvester Scoring System, thus allowing wider application of the technique. The study was carried out using a training set consisting of ECG data recorded from 705 individuals with and without previous myocardial infarction. Algorithms for the 50 criteria in the Selvester Scoring System were iteratively improved by comparison of scores obtained by 2 experienced cardiologist investigators with those generated by the program. The final version was evaluated in a test set consisting of 60 ECGs by comparing scores derived by cardiologist investigator with those obtained by the program. The disagreements occurred only in 1.1% of the score comparisons and in 1.6% of the specific measurements. In all cases in which a disagreement occurred, it resulted from very small differences in measurements. These results indicate that the algorithm for automated application of the Selvester Scoring System is adequate for both clinical and research applications.

Algorithms↗

PubMed2004

Transcriptional reprogramming in murine liver defines the physiologic consequences of biliary obstruction.

BACKGROUND/AIMS: While the metabolic and histological responses to cholestasis are recognized, the consequences of impaired biliary flow on liver gene expression are largely undefined. We hypothesized that biliary obstruction results in transcriptional reprogramming that dictates the physiologic response. METHODS: We determined global gene expression in murine livers 1-21 days following bile duct ligation. Total hepatic cRNA from experimental and sham mice was hybridized to Affymetrix gene chips. Gene expression data was analyzed by GeneSpring software and validated by Northern analysis. RESULTS: We found 92 genes over-expressed > or =2-fold at one or more time points following bile duct ligation. Functional classification of these genes revealed the activation of three main biological processes in a sequential and time-restricted fashion. At day 1, genes involved in sterol metabolism were uniquely over-expressed, including HMG-CoA reductase, the rate-limiting enzyme of cholesterol biosynthesis. This was followed by an increased expression of growth-promoting genes at day 7, the time point coinciding with peak cholangiocyte proliferation. In later phases (days 14-21), the liver over-expressed genes encoding structural proteins and proteases. CONCLUSIONS: Transcriptional reprogramming in the liver following biliary obstruction favors the activation of genes regulating metabolism, cell proliferation, and matrix remodeling in a time-restricted and sequential fashion.

Animals↗

PubMed2004

Behavioral analysis during the forced swimming test using a joystick device.

The behavioral test described by Porsolt in 1977 for screening potential antidepressant drugs is extensively used both in basic research and in the pharmaceutical industry. The measured behavior is the immobility time during the swimming test (preformed in rodents), which decreases upon acute antidepressant treatment. Several research groups have suggested some modifications on the original Porsolt paradigm and its analysis. Nevertheless, there are still inaccuracies resulting from either undefined intermediate behaviors or from considering the movement of the whole body as one unit without analyzing the motion of the limbs. Herein, we propose a novel and simple scoring method, based on continuous measurement of the limbs motion, using a joystick, a computer screen and simple software. We validated the method, using antidepressant drugs and studied examples of false positives and false negatives of the traditional Porsolt paradigm. The proposed method is easy to use, it accounts for all range of movements and the analysis is relatively fast. Moreover, the results obtained using this analysis method show a normal Gaussian distribution in a population of rats (while the traditional Porsolt analysis does not) which allows selective breeding of 'motivated' and 'depressed' lines of animals.

Animals↗

PubMedDate not supplied

FindEM--a fast, efficient program for automatic selection of particles from electron micrographs.

The FindEM particle picking program was tested on the publicly available keyhole limpet hemocyanin (KLH) dataset, and the results were submitted for the "bakeoff" contest at the recent particle picking workshop (Zhu et al., 2003b). Two alternative ways of using the program are demonstrated and the results are compared. The first of these approximates exhaustive projection matching with a full set of expected views, which need to be known. This could correspond to the task of extending a known structure to higher resolution, for which many 1000's of additional images are required. The second procedure illustrates use of multivariate statistical analysis (MSA) to filter a preliminary set of candidate particles containing a high proportion of false particles. This set was generated using the FindEM program to search with one template that crudely represents the expected views. Classification of the resultant set of candidate particles then allows the desired classes to be selected while the rest can be ignored. This approach requires no prior information of the structure and is suitable for the initial investigation of an unknown structure--the class averages indicate the symmetry and oligomeric state of the particles. Potential improvements in speed and accuracy are discussed.

Algorithms↗