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PubMed2000

Computer-aided ergonomics: a case study of incorporating ergonomics analyses into workplace design.

One of the primary goals of computer-aided ergonomics is to develop software tools that allow ergonomics information to be accessed at the earliest stages of design. This case study discusses a PC-based software program that allows a designer to quantify a worker's biomechanical risk for injury based on a proposed workplace design. The program couples an established software tool for biomechanical analysis, the Three-Dimensional Static Strength Prediction Program (3DSSPP), with a widely used computer-aided design software package, AutoCAD. The use of this "3DSSPP/AutoCAD interface" in the proactive analysis of an automotive assembly task is described and the results compared with an independent assessment using observations of workers performing the same task. Both studies yield similar conclusions, suggesting that proactive use of software such as the 3DSSPP/AutoCAD interface may be a valid tool in evaluating proposed workplace designs. In this context, issues in the analysis of workplace designs regarding the use of supporting ergonomic tools, assumptions, and posture selection are discussed.

Accidents, Occupational↗

PubMed1999

A short echo proton magnetic resonance spectroscopy study of the left mesial-temporal lobe in first-onset schizophrenic patients.

BACKGROUND: Past 1H magnetic resonance spectroscopy (MRS) studies of the temporal lobe in schizophrenic patients have shown decreased levels of N-acetylaspartate (NAA) suggesting reduced neuronal density in this region. However, the measured volumes have been large and included contributions from mostly white matter. METHODS: Short echo 1H MRS was used to measure levels of NAA and other metabolites (i.e., glutamate and glutamine) from a 6 cm3 volume in the left mesial-temporal lobe of 11 first-episode schizophrenic patients and 11 healthy control subjects of comparable age, gender, handedness, education, and parental education levels. Spectra were quantified without operator interaction using automated software developed in our laboratory. Metabolite levels were normalized to the internal water concentration of each volume studied. Images were also obtained to determine temporal lobe gray and white matter volumes. RESULTS: No significant differences were found between levels of NAA or other metabolites, or gray and white matter volumes, in first-episode schizophrenic patients and comparison subjects. CONCLUSIONS: Since the volume studied was small compared to previous studies and contained mostly gray matter, this result suggests consequential NAA decreases may be restricted to regions of white matter.

Adolescent↗

PubMed2000

Quantitative morphodynamics of endothelial cells within confluent cultures in response to fluid shear stress.

To evaluate shear stress-induced effects on cultured cells we have extended the mechanical setup of a multichannel in vitro rheological system and developed software allowing entire processing control and image data analysis. The values of cell motility, degree of orientation (alignment), and cell elongation were correlated as a function of time (morphodynamics). Collective and individual endothelial cells within confluent cultures displayed a shear stress-dependent characteristic phase behavior of the following time course: resting conditions (phase I), change of motility (phase II), onset of alignment (phase III), and finally cell elongation (phase IV). Especially cell motility was characterized by a randomized zigzag movement around mean trajectories (fluctuations) together with mean cell locomotion. Onset of shear stress caused a down-regulation of fluctuations of 30% within <10 min and simultaneously increased locomotion velocities preferring the flow direction (phase II). After a lag period of 10 to 20 min cells orientated in the direction of flow (phase III) without significant cell elongation, which finally occurs within hours (phase IV). These data provide first evidence that cells within confluent endothelial monolayers respond to shear stress with a characteristic phase behavior.

Animals↗

PubMed1994

A multidimensional spectrophotometer for monitoring thermal unfolding transitions of macromolecules.

We describe a multidimensional spectrometer that is capable of (nearly) simultaneous measurement of circular dichroism, steady-state fluorescence, and absorbance values on the same sample in a standard 1 x 1 cm cuvette. With a computer controlled thermoelectric cell holder, this instrument is capable of measuring the above types of spectral data at various wavelengths as a function of temperature. We have developed software to control the various acquisition functions and to convert the data files to a format appropriate for use with the nonlinear least squares program, NONLIN (Johnson and Frasier, 1985). We have tested various features of this instrument and we have applied this instrument and data analysis procedure to study the thermal unfolding of ribonuclease A, under conditions were the unfolding of this protein involves an intermediate state.

Biophysical Phenomena↗

PubMed2002

Evaluation in the design of health information systems: application of approaches emerging from usability engineering.

This paper examines the role of evaluation in the design of health care information systems. A framework is presented for considering evaluation in the context of software development processes, in particular, the systems development life cycle (SDLC). Variations on standard design methodologies are then discussed, including methods based on rapid development and continual evaluation of prototype systems. Usability testing is presented as a key method for conducting evaluations during iterative system development. The emergence of design methodologies, where evaluation is viewed as a central part of the development cycle is also discussed. Evaluation methodologies are then considered along a continuum, ranging from studies involving a high degree of experimental control to observational approaches. A full cycle approach to evaluation of health care systems is argued for, involving deployment of new methods across the SDLC. Implications for future work exploring the integration of design and evaluation processes in health informatics are discussed.

Biomedical Engineering↗

PubMed1999

Estimating medical resources required following a nuclear event.

Large quantities of medical resources are necessary for the treatment of patients suffering from acute radiation syndrome in combination with blast and thermal injuries (combined injuries). So far, however, there is no tool available for evaluating the resources required for the treatment of combined injuries. The purpose of this manuscript is to describe the scientific basis for a newly developed software tool designed to estimate the medical resources needed for treating the combined injuries of individuals/high numbers of casualties who may be involved in civil defense, emergency medical care and various military activities (namely out of area) in the case of a nuclear event.

Blast Injuries↗

PubMed2002

An intelligent system for multivariate statistical process monitoring and diagnosis.

A knowledge-based system (KBS) was designed for automated system identification, process monitoring, and diagnosis of sensor faults. The real-time KBS consists of a supervisory system using G2 KBS development software linked with external statistical modules for system identification and sensor fault diagnosis. The various statistical techniques were prototyped in MATLAB, converted to ANSI C code, and linked with the G2 Standard Interface. The KBS automatically performs all operations of data collection, identification, monitoring, and sensor fault diagnosis with little or no input from the user. Navigation throughout the KBS is via menu buttons on each user-accessible screen. Selected process variables are displayed on charts showing the history of the variables over a period of time. Multivariate statistical tests and contribution plots are also shown graphically. The KBS was evaluated using simulation studies with a polymerization reactor through a nonlinear dynamic model. Both normal operation conditions as well as conditions of process disturbances were observed to evaluate the KBS performance. Specific user-defined disturbances were added to the simulation, and the KBS correctly diagnosed both process and sensor faults when present.

Algorithms↗

PubMed2001

Computerized analysis of fetal heart rate parameters by gestational age.

OBJECTIVE: The aim of this study is to define the reference ranges for fetal heart rate (FHR) parameters according to gestational age, by determining the relationship between the FHR and gestational age using a computerized FHR analysis system. METHODS: Using our own software developed by Hanyang University Hospital in Korea, non-stress tests were performed for 20 min. FHR parameters for 6455 subjects were analyzed for various gestational groups; <25 weeks, 25-28 weeks, 29-32 weeks, 33-36 weeks, 37-40 weeks, and >40 weeks. RESULTS: The FHR parameters were related to gestational age. The mean baseline FHR, signal loss, and fetal movements decreased significantly with gestation (P<0.0001). The variability and accelerations of FHR were highest for the 37-40 weeks gestational group (P<0.05). CONCLUSIONS: The results showed that overall, the differences in the FHR parameters between gestational groups were statistically significant, and the gestational age of the fetus should be considered when interpreting FHR patterns.

Female↗

PubMed1996

Cerebral gray matter and white matter volume deficits in adolescent girls with anorexia nervosa.

OBJECTIVES: This study was undertaken to determine whether the increased cerebrospinal fluid (CSF) volumes found in anorexia nervosa (AN) are the result of differences in gray matter or white matter volumes or both. METHODS: Thirteen adolescent girls with AN who were receiving inpatient care at a tertiary-care university children's hospital and eight healthy female control subjects were studied by using magnetic resonance imaging. Images were processed by means of software developed to classify all pixels as either CSF, gray matter, or white matter. Pixels of each class were then summed across all sections. RESULTS: The AN group had larger total CSF volumes in association with deficits in both total gray matter and total white matter volumes. Lowest reported body mass index was inversely correlated with total CSF volume and positively correlated with total gray matter volume. Urinary free cortisol levels were positively correlated with total CSF volume and inversely correlated with central gray matter volume. CONCLUSIONS: These findings add support to the view that the brain abnormalities found in AN are in large part the result of the effects of the illness. The extent to which these differences in gray matter and white matter volumes are reversible with recovery remains to be established.

Adolescent↗

PubMed2003

A comparative analysis of optical and conventional axiography for the analysis of temporomandibular joint movements.

STATEMENT OF PROBLEM: Currently available systems for pantographic tracing are heavy, bulky, and can interfere with jaw movements. PURPOSE: This study describes the development and clinical application of optoelectronic axiography designed to overcome system inherent problems of conventional bulky frame-based registration axiography. The purpose of this study is the comparison of the newly developed system and conventional axiography. MATERIAL AND METHODS: Three-dimensional recordings of condylar pathways were acquired by means of infrared digitizers interfaced to newly developed software. Ten distinct curves in each of 10 subjects were recorded by synchronous optoelectronic axiography (100 tracings) and by conventional axiography (100 tracings). Usually, two 3-dimensional (3D) light weight sensors are provisionally fixed to the facial surface of a maxillary and mandibular incisor by means of a single orthodontic bracket. To allow for direct comparison of all 100 pairs of curves in this study, the 3D sensors of the optoelectronic system were attached to the bulky double face-bow system of the axiograph. The conformity of tracings (protrusion, opening/closing, mediotrusion, and laterotrusion) was evaluated by means of correlation analysis. Resulting axiographic recordings from both systems were evaluated by 3 experts (dentists, experienced in axiographic investigations, who were blind to the source of the data), focusing on standardized qualitative criteria of the recordings (homogeneity/smoothness, pathway-characteristics, excursion, and left/right-symmetry). After testing for normal distribution of the ratio scaled data (length of pathway, horizontal condylar inclination [HCI], Bennett angle) with the Kolmogoroff-Smirnov test (alpha=.01), axiographic curves were quantitatively compared by means of an intraclass correlation coefficient ([ICC] alpha =.01). The Wilcoxon test (alpha=.01) was used to evaluate equivalence of ordinally scaled values (homogeneity of tracings) and Cohen's Kappa was used to compare excursion and left/right symmetry. RESULTS: High correspondence between curves recorded by conventional and optoelectronic axiography was observed. The mean differences of lengths between the protrusive, opening/closing, and mediotrusive pathways were 0.0 mm, 0.6 mm, and 0.1 mm, respectively. Pathways and values for HCI were found highly correlated (pathways: 95% CI of ICC 0.9776-0.9908; HCI: 95% CI of ICC 0.8641-0.9597). The 95% CIs for differences of pathways, HCI-value, and Bennett angle were -0.1mm/0.3mm, -3.4 degrees/1.9 degrees, and -2.8 degrees/4.8 degrees, respectively. Pathway characteristics also corresponded well (Cohen's Kappa: 0.73 for symmetric and 0.72 for asymmetric movements), 0.77 for left/right symmetry, whereas other characteristics showed less significant correlation (Cohen's Kappa of excursion: 0.21 for symmetric and 0.09 for asymmetric movements, homogeneity: 0.08 for symmetric and 0.15 for asymmetric movements). CONCLUSION: Within the limitations of this study, optoelectronic axiography proved to be an applicable, promising technique, leading to diagnostic interpretations equivalent (with respect to the CIs) to conventional axiography.

Dental Occlusion↗

PubMed1999

A new design of stochastic partnership models for epidemics of sexually transmitted diseases with stages.

A problem of importance in modelling epidemics of sexually transmitted diseases is the development of mathematical structures accommodating sexual and other contacts among members of a population. Because these models may be complex, it is often necessary to use computer intensive methods in their analysis, which raises questions on the design of computer models. In this paper a new approach to designing models sexual contacts is presented within the context of a stochastic model accommodating the formation and dissolution of partnerships in heterosexual populations. Emphasis will be placed on the development of algorithms with a view towards developing software to implement computer intensive methods. Unlike previous formulations, rather than using rejection methods in Monte Carlo simulations to impose necessary constraints on random functions describing partnership formation, in the new formulation all constraints are satisfied with probability one.

Algorithms↗

PubMed1989

Ensemble proprioceptive activity in the cat step cycle: towards a representative look-up chart.

Analysis of the control of movement in tasks such as stepping is severely restricted by the lack of quantitative data on the ensemble activity of afferents in the numerous muscles involved. We have started to build up a quantitative "look-up-chart" of the ensemble afferent and efferent profiles in the cat step cycle. To this end, we have developed software which allows us to digitize afferent firing, muscle length and electromyogram (EMG) activity, and to align segments for averaging by choosing one or more reference points in the step cycle. The ensemble firing of triceps surae Ia afferents showed lower than expected mean and peak rates, whereas triceps group II and Ib afferents were more active than predicted. There were small but significant transients in Ia firing at foot-off and touch-down which could not be explained in terms of origin-to-insertion length lone. They were most likely caused by propagated mechanical transients or tendon compliance effects giving rise to small differences between the origin-to-insertion length and the intramuscular length "seen" by spindles. Net ensemble Ia rates, based on previous estimates of spindle populations, probably exceed 25 kilo-impulses/second (ki.p.s.) in some muscles. Inputs as large as this are likely to contribute significantly to reflex control.

Animals↗

PubMed2000

High pressure liquid chromatography of dentin primers and bonding agents.

OBJECTIVE: The purpose of this study was to analyse the composition of representative dentin primers and bonding agents, and to investigate the relationship between chromatographic retention times and partition coefficient (log P) values. METHODS: Dentin bonding systems (DBS) were analysed with reversed phase high-performance liquid chromatography (HPLC). The log P values were obtained computationally with the advanced chemistry development software. RESULTS: The DBS were analysed and the monomers were identified. The log P values were calculated and the relationship between log P and retention times for the monomers was described by the equation: log P = 2.436R(t) - 3.636, with a correlation value (r) of r = 0.9095. SIGNIFICANCE: The components of the DBS were successfully resolved and identified, thus illustrating the analytical power of HPLC regarding those systems. Also the log P values correlated with the retention times of monomers. Thus, they can be used as a prediction tool in future analysis. These findings are important for a mechanistic understanding of Primer and Adhesive actions in the bonding to the dentin.

Algorithms↗

PubMed1999

Computer-assisted, interactive fundus image processing for macular drusen quantitation.

PURPOSE: To design and validate a software package to quantitate the area subtended by drusen in color fundus photographs for the conduct of efficient, accurate clinical trials in age-related macular degeneration. DESIGN: Algorithm and software development. Comparisons with manual methodologies. PARTICIPANTS: Evaluation and testing on color fundus photographs from patient records and from eyes enrolled in the Choroidal Neovascularization Prevention Trial. METHODS: Fundus photographs of eyes with drusen were digitized. The green channel was selected for maximum contrast and preprocessed with filtering and shade correction to minimize noise, improve contrast, and correct for illumination and background inhomogeneities. Local thresholding and region-growing algorithms identified drusen. Multiple levels of supervision were incorporated to maximize robustness, accuracy, and validity. Validation studies compared computer-assisted with manual grading by an experienced grader. Intraclass correlation coefficients were calculated as a measure of the concordance between manual and computer-assisted fundus gradings. MAIN OUTCOME MEASURES: Drusen area and concordance with manual grading. RESULTS: Automated supervised image analysis offers extreme robustness and accuracy. Most images were segmented with little or no supervision, with processing times on the order of 5 seconds. More complicated images required supervision and a total analysis time varying from 20 seconds to 5 minutes, with most of this time devoted to inspection and comparison. Interactive image processing affords arbitrarily close concordance with manual drusen identification, with calculated intraclass correlation coefficients of 0.92 and 0.93 for comparison of manual with automated, supervised grading by two observers. CONCLUSIONS: Automated supervised fundus image analysis is an efficient, robust, valid technique for drusen quantitation from color fundus photographs. This approach should prove useful in the conduct of efficient accurate clinical trials for age-related macular degeneration.

Algorithms↗

PubMed1999

Computer-vision-enabled augmented reality fundus biomicroscopy.

PURPOSE: To guide treatment for macular diseases and to facilitate real-time image measurement and comparison, investigations were initiated to permit overlay of previously stored photographic and angiographic images directly onto the real-time slit-lamp biomicroscopic fundus image. DESIGN: Experimental study in model eyes, and preliminary observations in human subjects. METHODS: A modified, binocular video slit lamp interfaced to a personal computer and framegrabber allows for image acquisition and rendering of stored images overlaid onto the real-time slit-lamp biomicroscopic fundus image. Development proceeds with rendering on a computer monitor, while construction is completed on a miniature display interfaced directly with one of the slit-lamp oculars. Registration and tracking are performed with in-house-developed software. MAIN OUTCOME MEASURES: Tracking speed and accuracy, ergonomic acceptability. RESULTS: Computer-vision algorithms permit robust montaging, tracking, registration, and rendering of previously stored photographic and angiographic images onto the real-time slit-lamp fundus biomicroscopic image. In model eyes and in preliminary studies in a human eye, optimized registration permits near-video-rate image overlay with updates at 3 to 10 Hz and misregistration errors on the order of 1 to 5 pixels. CONCLUSIONS: A prototype for ophthalmic augmented reality (image overlay) is presented. The current hardware/software implementation allows for robust performance.

Algorithms↗

PubMed1999

Postoperative intraocular lens rotation: a randomized comparison of plate and loop haptic implants.

OBJECTIVE: To compare the postoperative rotation of plate and loop haptic implants of spherical power to ascertain the optimal design appropriate for toric intraocular lenses (IOLs). DESIGN: Randomized, controlled trial. PARTICIPANTS: Forty-eight patients attending for routine cataract surgery by phacoemulsification. METHOD: Patients with cataract as the only ocular disease were randomly implanted with plate or loop haptic implants after uncomplicated phacoemulsification. The baseline position of the IOL was determined from a video frame acquired at the conclusion of surgery. Postoperative IOL position was documented using digital retroillumination images at 2 weeks and 6 months after surgery. Capsular fusion patterns were recorded using slit-lamp biomicroscopy. Correlation of IOL rotation with axial length, capsular contraction, and fusion was attempted. MAIN OUTCOME MEASURES: Early IOL rotation, occurring between surgery and 2 weeks after surgery, was graded as mild (<10 degrees), moderate (10 degrees < to <30 degrees), or severe (>30 degrees) by a semiobjective online comparison of the images. Late IOL rotation, occurring between 2 weeks and 6 months, was measured more precisely using software developed specifically for the study. RESULTS: Twenty-three patients were allocated the loop haptic and 25 the plate haptic IOL. The groups were comparable for demographic variables and numbers of patients excluded from analysis (P > 0.05). Five (24%) of 21 of plate haptic IOLs underwent severe early rotation compared to 2 (9%) of 22 loop haptics (P = 0.36). The median late rotation was 6.8 degrees for loop haptics compared to 0.6 degrees for plate haptics (P = 0.0073). Between 2 weeks and 6 months, anticlockwise rotation had occurred in 16 (89%) of 18 loop haptic IOLs compared to 11 (52%) of 21 plate haptic IOLs (P = 0.0081). CONCLUSIONS: Plate haptic IOLs show greater rotational stability than do loop haptics made from polypropylene once capsular fusion has taken place. Loop haptics invariably rotate anticlockwise after 2 weeks.

Capsulorhexis↗

PubMed2001

Intrauterine growth retardation does not alter the distribution of tyrosine hydroxylase-immunoreactive neurons of A8, A9 and A10 groups in the rat: a three-dimensional reconstruction study.

The purpose of the present investigation was to evaluate possible effects of severe prenatal hypotrophy on the number and spatial distribution of tyrosine hydroxylase-immunoreactive neurons of the A8, A9 and A10 cell groups in the rat brain. Prenatal hypotrophy was induced in rat pups by ligaturing one uterine artery in pregnant rats on the 17th day of gestation. This procedure induces a severe growth retardation, which is never caught up with, even at adulthood. In both control and growth-retarded adult rats, serial coronal sections were cut through the retrorubral field, the substantia nigra, and the ventral tegmental area (A8, A9 and A10 cell groups, respectively). The number of tyrosine hydroxylase-immunoreactive neurons was determined, and their spatial localization was recorded by means of a 3-dimensional reconstruction software developed in our laboratory. Our 3-dimensional models provide a visual illustration of the heterogeneous continuum formed by the dopaminergic neurons. They illustrate the difficulty in demarcating the A8, A9 and A10 cell groups. Finally, our results show that intrauterine growth retardation did not affect either the number or the 3-dimensional organization of tyrosine hydroxylase-immunoreactive neurons in the adult rat brain.

Animals↗

PubMed2002

Evaluation of redox indicators and the use of digital scanners and spectrophotometer for quantification of microbial growth in microplates.

The growth indicators 2,3,5-triphenyltetrazolium chloride (TTC), 2-[4-iodophenyl]-3-[4-dinitrophenyl]-5-phenyltetrazolium chloride (INT), 2,3-bis[2-methoxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxanilide inner salt (XTT), 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT), and resazurin were tested for their ability to indicate bacterial growth/growth inhibition. Two reading devices were evaluated and compared, a microplate spectrophotometer and a digital flatbed scanner. The bacteria used in the study were cultivated in 96-wells microplates and readings were made after 24 h. The scanned pictures were analysed with a software developed in-house to generate numerical values. It was found that resazurin was difficult to use since it shifts between three colours. MTT and TTC had a high correlation between the spectrophotometer data and the data from the scanned images. The reproducibility was similar for both reading devices. In no case was there a need to resuspend the pellets before reading. Both the XTT and INT showed lower correlations. It is concluded that bacterial growth/growth inhibition can be easily and reproducibly measured from microplate cultivations with a flatbed scanner or with a microplate spectrophotometer.

Bacteria↗