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At least 595 records · Page 33Linked to original sources
PubMed1966

Measurement of the incidence of tuberculous infection.

For certain purposes it is desirable to know the incidence of tuberculous infection in various population groups with a high degree of accuracy. The most accurate method for obtaining such information is the follow-up method, in which the population is tuberculintested on two separate occasions in order to determine the proportion who become infected with tubercle bacilli during the interval. The method is illustrated by means of data collected on children under 9 years old in Tunisia. The data indicate that the use of the same limit between "positive" and "negative" reactions in the two tests would lead to biased estimates of infection rates. A method of analysis involving the use of different limits has therefore been developed and applied to the data. The accuracy of the incidence rates obtained is indicated by a comparison of hypothetical prevalence rates computed from them with the observed prevalence rates.

Child↗
PubMed1999

Dynamic three-dimensional freehand echocardiography using raw digital ultrasound data.

In this paper, we present a new method for simple acquisition of dynamic three-dimensional (3-D) ultrasound data. We used a magnetic position sensor device attached to the ultrasound probe for spatial location of the probe, which was slowly tilted in the transthoracic scanning position. The 3-D data were recorded in 10-20 s, and the analysis was performed on an external PC within 2 min after transferring the raw digital ultrasound data directly from the scanner. The spatial and temporal resolutions of the reconstruction were evaluated, and were superior to video-based 3-D systems. Examples of volume reconstructions with better than 7 ms temporal resolution are given. The raw data with Doppler measurements were used to reconstruct both blood and tissue velocity volumes. The velocity estimates were available for optimal visualization and for quantitative analysis. The freehand data reconstruction accuracy was tested by volume estimation of balloon phantoms, giving high correlation with true volumes. Results show in vivo 3-D reconstruction and visualization of mitral and aortic valve morphology and blood flow, and myocardial tissue velocity. We conclude that it was possible to construct multimodality 3-D data in a limited region of the human heart within one respiration cycle, with reconstruction errors smaller than the resolution of the original ultrasound beam, and with a temporal resolution of up to 150 frames per second.

Adult↗
PubMedDate not supplied

Documentation and coding of medical records in a tertiary care center: a pilot study.

BACKGROUND: Since the medical record is the major source of health information, it is necessary to maintain accurate, comprehensive and properly coded patient data. We reviewed 300 medical records from patients at King Faisal Specialist Hospital and Research Center, representing four departments (medicine, surgery, pediatrics and obstetrics and gynecology). METHODS: The records were audited following the guidelines of the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) for accuracy and completeness of documentation and coding of primary and secondary diagnoses and procedures performed. RESULTS: Of 1051 items abstracted, 876 (83.3%) were accurately documented, 41 (3.9%) were inaccurately documented, and 134 (12.7%) were not documented. Of the items abstracted, 736 (70%) were assigned a correct code, 110 (10.5%) were assigned an incorrect code, and 205 (19.5%) were not coded. More items classified as accurately documented were coded correctly (71.1%) than items inaccurately documented (49.7%) (P < 0.0001). The difference in comprehensiveness of documentation, which reflects physician performance, was not statistically significant among the four departments (P value < 0.234). The difference in the accuracy of coding, which reflects coder performance, was statistically significant (P value < 0.036). CONCLUSIONS: Only 60% of the audited records met the benchmark for good quality medical records with regards to documentation and coding. A positive correlation between the accurate documentation and correct coding was noted, which supports the conclusion that high quality documentation enhances coding accuracy. These data, although encouraging, suggest room for improvement, which can be achieved through the collaboration of clinicians, who have extensive clinical experience, and coding professionals, who have comprehensive classification system expertise.

Documentation↗
PubMedDate not supplied

Only two-phase models, computed independently for males and females, are appropriate to describe fetal head growth.

OBJECTIVE: To establish an accurate mathematical model describing fetal head growth, taking into account gender differences and changes in growth rate during gestation. METHODS: Ultrasound measurements of head circumference and biparietal diameter were made on 1,336 normal fetuses (684 males and 652 females) in the Maternité Régionale de Nancy (France). A new two-phase model, taking into account an alteration in growth kinetics at 30 gestational weeks, was computed independently for male and female data. The accuracy of this model was tested and compared with three current mathematical models: a linear-quadratic, a linear-cubic, and the Rossavik and Deter (1984) models. RESULTS: In all models, including ours, the coefficients of determination (R(2)) were high (> or =0.999), so long as male and female data were computed separately. However, the standard error estimates (SEE) of our two-phase model were much lower (0.13 < or = SEE < or = 0.57) than the SEE of the three other models when computed over the whole gestational period (0.49 < or = SEE < or = 2.69); nevertheless, when these three other models were computed for these two successive periods, their SEE decreased, and data fitting was improved. CONCLUSION: Only two-phase mathematical models, computed independently for male and female data, accurately describe the kinetics of fetal head growth. They should be used to calculate growth standards and to perform an exact diagnosis of impaired growth.

Cephalometry↗
PubMed1994

The ultrasonic diagnosis of infantile hypertrophic pyloric stenosis: technique and accuracy.

The role of ultrasound for the diagnosis of pyloric stenosis has yet to be definitely established. We have carried out 147 ultrasound examinations of 142 infants (99 male and 43 female) with a history of projectile vomiting or the possibility of a pyloric mass. Measurements of the pyloric canal length, transverse pyloric diameter and muscle wall thickness were taken from a longitudinal view of the pylorus and related to previously described control data. The accuracy of the ultrasound examination was related to the finally established diagnosis. The results obtained revealed a sensitivity of 97% and specificity of 99% with positive predictive value of 99%. The three diagnostic errors (1 false positive and 2 false negative) occurred during the 'learning curve' of the radiologists and were the 15th, 29th and 35th cases examined, indicating that almost a 100% accuracy can potentially be achieved. This study confirms that ultrasound examination is the first line of investigation in a child in whom the clinical diagnosis of hypertrophic pyloric stenosis is uncertain and indicates that unnecessary surgery can thereby be prevented.

False Negative Reactions↗
PubMed1996

[Influence of respiration and pulsatility on the accuracy of MR-phase contrast flow measurements: "in vitro" evaluation].

PURPOSE: Determination of the influence of pulsatility of blood flow and respiration-induced vascular motion on the accuracy of MR phase contrast flow measurements. MATERIAL AND METHODS: Flow measurements in phantoms were performed with the phase contrast technique in a 1.5 Tesla MRI system using different flow volumes, varying degrees of flow pulsatility and a varying number of image phases. To determine the influence of respiratory motion on flow measurement accuracy, flow data was collected during motion of the whole phantom. RESULTS: Flow measurements based on 6 and 16 image phases were significantly more accurate (p < 0.05) than those based on one phase. An increase in the degree of pulsatility resulted in a widening of the error range. Hence, increasing pulsatility demands an increase in the number of acquired phases to maintain sufficient measurement accuracy. Simulated respiratory motion with an excursion depth of only 5 mm resulted in a significant overestimation of true flow ranging between 22.9 and 42.1%. Measurements without simulated respiratory motion were more accurate (p < 0.001). An excursion depth of 15 mm led to a vast increase in the apparent vessel size in excess of 100%. Flow volume measurements increased accordingly to 1126 ml/min (true flow = 720 ml/min). CONCLUSION: Accurate phase-contrast based flow measurements require an adjustment of acquisition parameters to correspond to the physiology of the vessel under consideration. Flow data in vessels subject to respiratory motion should only be collected in apnoea.

Blood Flow Velocity↗
PubMed1990

Analysis of high-resolution electron diffraction patterns from purple membrane labelled with heavy-atoms.

Progress in the structure determination of bacteriorhodopsin, the protein component of purple membrane from Halobacterium halobium has been limited by the lack of three-dimensional phase information between 6 and 3 A resolution. By analogy with X-ray methods, it is possible that heavy-atom labelling of the membrane crystal may provide heavy-atom derivatives that can be used for phasing by the multiple isomorphous replacement method. This paper describes the screening of heavy-atom compounds as potential derivatives, and the evaluation of the data collected from these heavy-atom-labelled membranes. Improvements in the methods for collecting electron diffraction data and analysing and merging the data are presented. Diffraction patterns of purple membrane samples were taken at -120 degrees C to minimize radiation damage. About 30 heavy-atom compounds were tested for use as potential derivatives. The diffraction patterns from labelled membranes were analysed by examining 6.5 A difference Fourier maps. Two heavy-atom compounds were selected for three-dimensional data collection at 3 A resolution. In addition, a full set of native data at -120 degrees C was collected to 2.7 A resolution. The intensity merging, heavy-atom derivative evaluation, heavy-atom refinement and the calculation of phases are presented. Phases are compared to those determined by electron microscope imaging, and limitations of the method are discussed. It is concluded that, with the present accuracy of data collection and the present magnitude of delta F/F available for the derivatives, the phasing power is too small. The phases that are obtained are not sufficiently accurate to provide a reliably interpretable map. It may be possible, however, to use the heavy-atom derivative data in difference Fourier calculations in which the presence of a peak would confirm the phases calculated from a model or obtained by electron microscope imaging.

Bacteriorhodopsins↗
PubMed2001

His-391 of beta-galactosidase (Escherichia coli) promotes catalyses by strong interactions with the transition state.

His-391 of beta-galactosidase (Escherichia coli) was substituted by Phe, Glu, and Lys. Homogeneous preparations of the substituted enzymes were essentially inactive unless very rapid purifications were performed, and the assays were done immediately. The inactive enzymes were tetrameric, just like wild-type beta-galactosidase and their fluorescence spectra were identical to the fluorescence spectrum of wild-type enzyme. Analyses of two of the substituted enzymes that were very rapidly purified to homogeneity and rapidly assayed while they were still active (at only a few substrate concentrations so that the data could be rapidly obtained), showed that the kinetic values were very similar to the values obtained with the same enzymes that were only partially purified. This showed that the kinetics were not affected by the degree of purity and allowed kinetic analyses with partially purified enzymes so that large numbers of points could be used for accuracy. The data showed that His-391 is a very important residue. It interacts strongly with the transition state and promotes catalysis by stabilizing the transition state. Activation energy differences (deltadelta G(S) double dagger), as determined by differences in the kcat/Km values, indicated that substitutions for His-391 caused very large destabilizations (22.8-35.9 kJ/mol) of the transition state. The importance of His-391 for transition state stabilization was confirmed by studies that showed that transition state analogs are very poor inhibitors of the substituted enzymes, while inhibition by substrate analogs was only affected in a small way by substituting for His-391. The poor stabilities of the transition states caused significant decreases of the rates of the glycolytic cleavage steps (galactosylation, k2). Degalactosylation (k3) was not decreased to the same extent.

Amino Acid Substitution↗
PubMed2006

Constrained least-squares optimization for robust estimation of center of rotation.

This paper presents a new direct method for estimating the average center of rotation (CoR). An existing least-squares (LS) solution has been shown by previous works to have reduced accuracy for data with small range of motion (RoM). Alternative methods proposed to improve the CoR estimation use iterative algorithms. However, in this paper we show that with a carefully chosen normalization scheme, constrained least-squares solutions can perform as well as iterative approaches, even for challenging problems with significant noise and small RoM. In particular, enforcing the normalization constraint avoids poor fits near plane singularities that can affect the existing LS method. Our formulation has an exact solution, accounts for multiple markers simultaneously, and does not depend on manually-adjusted parameters. Simulation tests compare the method to four published CoR estimation techniques. The results show that the new approach has the accuracy of the iterative methods as well as the short computation time and repeatability of a least-squares solution. In addition, application of the new method to experimental motion capture data of the thumb carpometacarpal (CMC) joint yielded a more plausible CoR location compared to the previously reported LS solution and required less time than all four alternative techniques.

Algorithms↗
PubMed1994

Computerized databases for emergency care: what impact on patient care?

A field-based evaluation is conducted of a Clinical Computerized Information System (CCIS). Following training, the use of the CCIS database, word processing and other programs by thirteen full-time practicing emergency physicians in two urban emergency departments of a University-associated teaching hospital was studied over a one-year period. A tracking program automatically logged frequency and duration of use by the physicians, and user satisfaction was assessed by a reliable and validated questionnaire instrument. Based on utilization data and verbal reports of these physicians, CCIS database searching was not only found to be easy-to-learn but was readily accessible during emergency shifts. Individual physicians were found to perform an average of 3.5 searches per month lasting a mean search time of 8 min. Positive notes about the CCIS system included ease-of-use, accuracy of data, accessibility of system, and value of output while negative perceptions included a lack of integration with other systems, a lack of system completeness, and a high subscription cost. It was suggested that a less costly telephone link to a high-volume Centre would be desirable in actual implementation of the system.

Attitude of Health Personnel↗
PubMedDate not supplied

A method for estimation of bias and variability of continuous gas monitor data: application to carbon monoxide monitor accuracy.

A method is presented for the evaluation of the bias, variability, and accuracy of gas monitors. This method is based on using the parameters for the fitted response curves of the monitors. Thereby, variability between calibrations, between dates within each calibration period, and between different units can be evaluated at several different standard concentrations. By combining variability information with bias information, accuracy can be assessed. An example using carbon monoxide monitor data is provided. Although the most general statistical software required for these tasks is not available on a spreadsheet, when the same number of dates in a calibration period are evaluated for each monitor unit, the calculations can be done on a spreadsheet. An example of such calculations, together with the formulas needed for their implementation, is provided. In addition, the methods can be extended by use of appropriate statistical models and software to evaluate monitor trends within calibration periods, as well as consider the effects of other variables, such as humidity and temperature, on monitor variability and bias.

Bias↗
PubMed1999

Use of a priori information in estimating tissue resistivities--application to measured data.

A statistically constrained minimum mean squares error estimator (MiMSEE) has been shown to be useful in estimating internal resistivity distribution by the use of simulated data. In this study, the performance of the MiMSEE algorithm is tested by using measured data from resistor phantoms. The MiMSEE uses a priori information on body geometry, electrode position, statistical properties of tissue resistivities, instrumentation noise and linearization error to calculate the optimum inverse matrix which maps the surface potentials to unknown regional resistivities. In this study, the MiMSEE is also constrained with the variance-covariance of the modelling error to improve the estimation accuracy. The data are obtained from two different phantom geometries, namely five-region and thorax. Using the measured data, the estimations are realized and errors are calculated. Then, the results are compared with the results obtained by using a conventional least squares error estimator (LSEE). The five-region model results show similarity with the simulation study results of Baysal and Eyüboğlu. On the thorax model, the total estimation error is 34.2% with the MiMSEE compared with 856% with the LSEE. It is concluded that the MiMSEE is more robust than the LSEE and applicable to measured data.

Algorithms↗
PubMed1999

Excess maternal transmission of type 2 diabetes. The Northern California Kaiser Permanente Diabetes Registry.

OBJECTIVE: To assess excess maternal transmission of type 2 diabetes in a multiethnic cohort. Previous studies have reported higher prevalence of diabetes among mothers of probands with type 2 diabetes than among fathers. This analysis is vulnerable to biases, and this pattern has not been observed in all populations or races. RESEARCH DESIGN AND METHODS: We assessed evidence for excess maternal transmission among 42,533 survey respondents with type 2 diabetes (probands) by calculating the prevalence of diabetes in their siblings and offspring. To assess data quality, we evaluated completeness of family history data provided. Accuracy of family information reported by probands was also evaluated by comparing survey responses in a subsample of 206 probands with family histories modified after further interviews with relatives. RESULTS: Siblings (n = 60,532) of probands with affected mothers had a greater prevalence of diabetes (20%) than those with affected fathers (17%) (P < 0.001 for adjusted odds ratios). Prevalence of diabetes was higher among the offspring (n = 72,087) of female (3.4%) versus male (2.2%) probands (P < 0.001 for adjusted odds ratios). These patterns were evident in all races and both sexes; however, the effect size was clinically insignificant in African-Americans and male offspring. In general, probands provided more complete data about diabetes status for the maternal arm of the pedigree than the paternal arm. Completeness of knowledge was not related to proband sex, but was related to education and race, and inversely to age. Accuracy of proband-reported family history was consistently good (kappa statistics generally > 0.70). CONCLUSIONS: Excess maternal transmission was observed in all races and both sexes, although the size of the excess was negligible in African-Americans and male offspring. Potential reporting and censoring biases are discussed.

Adolescent↗
PubMed1995

Accuracy of leukocyte indices and C-reactive protein for diagnosis of neonatal sepsis: a critical review.

To evaluate the value of C-reactive protein and leukocyte indices in the workup of patients suspected of having infection in a neonatal intensive care setting, a literature search was conducted in all languages using MEDLINE (1966 to May, 1994), EMBASE (1988 to May, 1994), bibliographic lists of primary and review articles and personal files. Citations identified as potentially relevant were reviewed by two independent investigators; only studies meeting preset criteria for population, diagnostic test and data presentation were included. Two observers independently assessed studies using explicit methodologic criteria. All data from the articles were extracted by one observer, whereas the second reviewer checked these data for accuracy. Four of the selected studies dealt with leukocyte count and ratios. The chi square test for homogeneity of proportions revealed significant heterogeneity across studies (P = 0.014 for the ratios; P < 0.001 for white blood cell count), suggesting that test properties varied widely across studies. Fifteen of the selected studies evaluated C-reactive protein; of these six were qualitative using a latex agglutination method. Among these studies the chi square test for homogeneity of proportions was highly significant (P < 0.01), reflecting the great heterogeneity across studies. Among the nine studies that evaluated five different quantitative methods heterogeneity was again present (P < 0.001). Because of the striking heterogeneity among the studies evaluated, pooling to give a summary point estimate of the sensitivity and specificity of the various studies was not possible and the results are reported as ranges.(ABSTRACT TRUNCATED AT 250 WORDS)

Biomarkers↗
PubMed2001

Georeferenced regional simulation and aquatic exposure assessment.

A simulation model system of the waste water pathways and the aquatic fate assessment is coupled to a discrete digitized river network. Temporal concentration distributions of down-the-drain chemicals are calculated from variable and uncertain input data and compared to monitoring data. The accuracy of the predictions are within a factor of three for the studied pilot catchments. Spatial distributions of the whole catchment give stochastic information on a regional basis for probabilistic risk assessments.

Computer Simulation↗
PubMed2003

Meshfree representation and computation: applications to cardiac motion analysis.

For medical image analysis issues where the domain mappings between images involve large geometrical shape changes, such as the cases of nonrigid motion recovery and inter-object image registration, the finite element methods exhibit considerable loss of accuracy when the elements in the mesh become extremely skewed or compressed. Therefore, algorithmically difficult and computationally expensive remeshing procedures must be performed in order to alleviate the problem. We present a general representation and computation framework which is purely based on the sampling nodal points and does not require the construction of mesh structure of the analysis domain. This meshfree strategy can more naturally handle very large object deformation and domain discontinuity problems. Because of its intrinsic h-p adaptivity, the meshfree framework can achieve desired numerical accuracy through adaptive node and polynomial shape function refinement with minimum extra computational expense. We focus on one of the more robust meshfree efforts, the element free Galerkin method, through the moving least square approximation and the Galerkin weak form formulation, and demonstrate its relevancy to medical image analysis problems. Specifically, we show the results of applying this strategy to physically motivated multiframe motion analysis, using synthetic data for accuracy assessment and for comparison to finite element results, and using canine magnetic resonance tagging and phase contrast images for cardiac kinematics recovery.

Algorithms↗
PubMed1997

Image-guided endoscopic surgery: results of accuracy and performance in a multicenter clinical study using an electromagnetic tracking system.

Image-guided surgery has recently been described in the literature as a useful technology for improved functional endoscopic sinus surgery localization. Image-guided surgery yields accurate knowledge of the surgical field boundaries, allowing safer and more thorough sinus surgery. We have previously reviewed our initial experience with The InstaTrak System. This article presents a multicenter clinical study (n=55) that assesses the system's capability for localizing structures in critical surgical sites. The purpose of this paper is to present quantitative data on accuracy and performance. We describe several new advances including an automated registration technique that eliminates the redundant computed tomography scan, compensation for head movement, and the ability to use interchangeable instruments.

Adolescent↗
PubMed1998

Three-dimensional determination of femoral-tibial contact positions under in vivo conditions using fluoroscopy.

OBJECTIVE: A method has been developed to accurately measure three-dimensional (3-D) femoral-tibial contact positions of artificial knee implants in vivo from X-ray fluoroscopy images using interactive 3-D computer vision algorithms. DESIGN: A computerized graphical (CAD) model of an implant component is displayed as an overlay on the original X-ray image. An image matching algorithm matches the silhouette of the implant component against a library of images, in order to estimate the position and orientation (pose) of the component. The operator further adjusts the pose of the graphical model to improve the accuracy of the match. BACKGROUND: Previous methods for in vivo measurement of joint kinematics make only indirect measurements of joint kinematics, require invasive procedures such as markers or pins, or make simplifying assumptions about imaging geometry which can reduce the accuracy of the resulting measurements. METHODS: Fluoroscopic videos are taken of implanted knees in subjects performing weight-bearing motion. Images from the videos are digitized and stored on a computer workstation. Using computerized model matching, the relative pose of the two knee implant components can be determined in each image. The resulting information can be used to determine where the two components are contacting, the area of the contact region, liftoff angle, and other kinematic data. RESULTS: Accuracy tests done on simulated imagery and in vitro real imagery show that the pose estimation method is accurate to less than 0.5 mm of error (RMS) for translations parallel to the image plane. Orientation error is less than or equal to 0.35 degrees about any axis. Errors are larger for translations perpendicular to the image plane (up to 2.25 mm). In a clinical study, the method was used to measure in vivo contact points, and characterize the kinematic patterns of two different knee implant designs. CONCLUSIONS: The ability to accurately measure knee kinematics in vivo is critical for the understanding of the behavior of knee implant designs and the ultimate development of new, longer lasting implants. RELEVANCE: This work shows that it is possible to accurately measure the three-dimensional position and orientation (pose) of artificial knee implants in vivo from X-ray fluoroscopy images using interactive 3-D computer graphics. The method can be applied to any joint when accurate CAD models are available. The resulting data can be used to characterize the kinematics of current knee implant designs.

Journal Article↗