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PubMed2003

Angular dependence of the luminance and contrast in medical monochrome liquid crystal displays.

Active-matrix liquid crystal displays (AMLCDs) are light-modulating devices that generate images by differentially transmitting a nearly uniform luminous field provided by a backlight. While emissive displays exhibit a quasi-Lambertian emission with almost constant contrast at off-normal viewing, the anisotropy of the electro-optic effect that controls light transmission in AMLCDs causes a pixel luminance that varies, sometimes strongly, with viewing angle. These variations are not identical for all gray levels and can eventually cause grayscale inversions. In this paper, we measured the luminance emission of a monochrome medical AMLCD, a medical cathode-ray tube monitor, and a color desktop AMLCD, using a collimated photopic probe positioned on a manual rotation arm, and a research radiometer with automatic readout. The probe measures luminance with a small acceptance angle and provides optical shielding from emissions at other viewing directions that contaminate the readings. We obtained luminance response curves versus angle in the vertical, horizontal and at 45 degrees diagonal directions. The display systems were calibrated to reflect the DICOM Part 3.14 standard grayscale display function (GDF) when measured using the manufacturer's probe and software tools. We analyzed the measurements at different viewing directions with respect to their departure from the GDF by computing the normalized contrast (deltaL/L) as a function of the DICOM just-noticeable difference index. Although cathode-ray tubes are known to be quasi-Lambertian emitters, the luminance at normal viewing is higher than the luminance observed at large angles. This decrease in luminance is however proportionally similar for all gray levels, resulting in a relatively flat contrast response for all angles. In addition to being more pronounced, the angular variation in AMLCDs does not follow the same profile at different intensities with the subsequent variation in the achieved display contrast. The changes due to off-normal viewing are substantial at large angles in the horizontal and vertical directions, and much worse in the diagonal viewing directions.

Anisotropy↗
PubMed2003

The utilization of visual feedback in the control of movement direction: evidence from a video aiming task.

The purpose of the present study was to establish the contribution of visual feedback in the correction of errors during movement execution (i.e., online) and the utilization of visual feedback from a completed movement in the programming of upcoming trials (i.e., offline). Participants performed 2 dimensional sweeping movements on a digitizing tablet through 1 of 3 targets, which were represented on a video monitor. The movements were performed with and without visual feedback under 4 criterion movement times (150, 250, 350, 450 msec). We analyzed the variability in directional error at 25%, 50%, 75%, and 100% of the distance between the home position and the target. There were significant differences in variability between visual conditions at each movement time. However, in the 150-msec condition, the form of the variability profiles did not differ between visual conditions, suggesting that the contribution of visual feedback was due to offline processes. In the 250-, 350-, and 450-msec conditions, there was evidence for both online and offline control, as the form of the variability profiles differed between the vision and no vision conditions.

Adolescent↗
PubMed2005

Sequencing of random Euplotes crassus macronuclear genes supports a high frequency of +1 translational frameshifting.

Programmed translational frameshifts have been identified in genes from a broad range of organisms, but typically only a very few genes in a given organism require a frameshift for expression. In contrast, a recent analysis of gene sequences available in GenBank from ciliates in the genus Euplotes indicated that >5% required one or more +1 translational frameshifts to produce their predicted protein products. However, this sample of genes was nonrandom, biased, and derived from multiple Euplotes species. To test whether there truly is an abundance of frameshift genes in Euplotes, and to more accurately assess their frequency, we sequenced a random sample of 25 cloned genes/macronuclear DNA molecules from Euplotes crassus. Three new candidate +1 frameshift genes were identified in the sample that encode a membrane occupation and recognition nexus (MORN) repeat protein, a C(2)H(2)-type zinc finger protein, and a Ser/Thr protein kinase. Reverse transcription-PCR analyses indicate that all three genes are expressed in vegetatively proliferating cells and that the mRNAs retain the requirement of a frameshift. Although the sample of sequenced genes is relatively small, the results indicate that the frequency of genes requiring frameshifts in E. crassus is between 3.7% and 31.7% (at a 95% confidence interval). The current and past data also indicate that frameshift sites are found predominantly in genes that likely encode nonabundant proteins in the cell.

Animals↗
PubMed2006

Evaluation of low-cost computer monitors for the detection of cervical spine injuries in the emergency room: an observer confidence-based study.

BACKGROUND: To compare the diagnostic value of low-cost computer monitors and a Picture Archiving and Communication System (PACS) workstation for the evaluation of cervical spine fractures in the emergency room. METHODS: Two groups of readers blinded to the diagnoses (2 radiologists and 3 orthopaedic surgeons) independently assessed-digital radiographs of the cervical spine (anterior-posterior, oblique and trans-oral-dens views). The radiographs of 57 patients who arrived consecutively to the emergency room in 2004 with clinical suspicion of a cervical spine injury were evaluated. The diagnostic values of these radiographs were scored on a 3-point scale (1 = diagnosis not possible/bad image quality, 2 = diagnosis uncertain, 3 = clear diagnosis of fracture or no fracture) on a PACS workstation and on two different liquid crystal display (LCD) personal computer monitors. The images were randomised to avoid memory effects. We used logistic mixed-effects models to determine the possible effects of monitor type on the evaluation of x ray images. To determine the overall effects of monitor type, this variable was used as a fixed effect, and the image number and reader group (radiologist or orthopaedic surgeon) were used as random effects on display quality. Group-specific effects were examined, with the reader group and additional fixed effects as terms. A significance level of 0.05 was established for assessing the contribution of each fixed effect to the model. RESULTS: Overall, the diagnostic score did not differ significantly between standard personal computer monitors and the PACS workstation (both p values were 0.78). CONCLUSION: Low-cost LCD personal computer monitors may be useful in establishing a diagnosis of cervical spine fractures in the emergency room.

Attitude of Health Personnel↗
PubMedDate not supplied

Costs and benefits of picture archiving and communication systems.

A picture archiving and communication system (PACS) is an electronic and ideally filmless information system for acquiring, sorting, transporting, storing, and electronically displaying medical images. PACS have developed rapidly and are in operation in a number of hospitals. Before widespread adoption of PACSs can occur, however, their cost-effectiveness must be proven. This article introduces the basic components of a PACS. The current PACS cost-analysis literature is reviewed. Some authors conclude that the PACS would pay for itself, while others find the PACS much more expensive. Explanations for these differences are explored. Almost all of these studies focus on direct costs and ignore indirect costs and benefits. The literature characterizing the indirect costs of PACS is reviewed. The authors conclude that there is a need for uniform, well-defined criteria for the calculation of the costs and savings of PACSs.

Computer Communication Networks↗
PubMed2004

Possible association between heavy computer users and glaucomatous visual field abnormalities: a cross sectional study in Japanese workers.

STUDY OBJECTIVE: To study the association between computer use and visual field abnormalities (VFA) and to assess whether heavy computer users have an increased risk of glaucoma. DESIGN: Cross sectional multicentre study. Subjects and observation procedures: A total of 10 202 randomly selected Japanese workers (mean (SD) age 43.2 (9.8) years) were screened for VFA using the frequency doubling technology perimetry (FDT-VFA), in addition to undergoing a general medical check up, and then ophthalmologically examined. Information about their computer use and refractive errors was obtained from a questionnaire and interview, respectively. MAIN RESULTS: As a result of FDT test, 522 and 8602 subjects were positive and negative for FDT-VFA, respectively. A significant (p = 0.004) interaction was found between computer use and refractive errors regarding the risk of FDT-VFA. In stratified analysis, heavy computer users with refractive errors showed a significant positive association with FDT-VFA (odds ratio (OR) = 1.74, 95% confidence interval (CI) 1.28 to 2.37), while those without refractive errors did not. Comparison of 165 subjects with an ophthalmological diagnosis of glaucoma and 2918 controls showed that the OR for glaucoma of heavy computer users with refractive errors was 1.82 (95% CI 1.06 to 3.12). Of 165 subjects with glaucoma, 141 had refractive errors, especially myopia (96.4%, 136 of 141). CONCLUSIONS: Although there are limitations to this study, such as its cross sectional design, heavy computer users with refractive errors seem to have an increased risk of FDT-VFA. Glaucoma might be involved in an underlying disease and myopia in a risk factor for FDT-VFA.

Adult↗
PubMed2004

Perceived muscular tension, job strain, physical exposure, and associations with neck pain among VDU users; a prospective cohort study.

AIMS: To determine whether perceived muscular tension, job strain, or physical exposure are associated with increased risk of developing neck pain among VDU users. METHODS: A baseline questionnaire was answered by 1283 respondents, of whom 671 were free from neck pain at baseline. Perceived muscular tension, job strain, and physical exposure were assessed at baseline. Information about newly developed neck pain was collected in 10 follow up questionnaires and the case definition was the first report of such pain in any of the follow up questionnaires. Median follow up time was 10.9 months. RESULTS: Both men and women who perceived muscular tension at least a few times per week, compared to those who had not perceived muscular tension the preceding month, had an incidence rate ratio (IRR) of 1.9 (95% CI 1.25 to 2.93) for developing neck pain, when stratifying for sex. High perceived muscular tension was associated with an increased risk (IRR 1.6, 95% CI 1.02 to 1.91), even when controlling for job strain, physical exposure, and age in the model stratified by sex. CONCLUSIONS: Perceived muscular tension was associated with an increased risk of developing neck pain among VDU users. The combination of high job strain and high perceived muscular tension was associated with higher risk of developing neck pain than the combination of high physical exposure and high perceived muscular tension. There was an indication of an excess risk due to interaction between high physical exposure and high job strain.

Adult↗
PubMed2005

Self-reported workplace related ergonomic conditions as prognostic factors for musculoskeletal symptoms: the "BIT" follow up study on office workers.

AIMS: To identify prognostic ergonomic and work technique factors for musculoskeletal symptoms among office workers and in a subgroup with highly monotonous repetitive computer work. METHODS: A baseline questionnaire was delivered to 5033 office workers in 11 Danish companies in the first months of 1999, and a follow up questionnaire was mailed in the last months of 2000 to 3361 respondents. A subgroup with highly monotonous repetitive computer work was formed including those that were repeating the same movements and/or tasks for at least 75% of the work time. The questionnaire contained questions on ergonomic factors and factors related to work technique. The outcome variables were based on the frequency of musculoskeletal symptoms during the last 12 months. Logistic regression analyses were used to identify prognostic factors for symptoms in the three body regions. RESULTS: In total, 39%, 47%, and 51% of the symptomatic subjects had a reduced frequency of symptom days in the neck/shoulder, low back, or elbow/hand region, respectively. In all regions more men than women had reduced symptoms. In the multivariate logistic regression analyses, working no more than 75% of the work time with the computer was a prognostic factor for musculoskeletal symptoms in the neck/shoulder and elbow/hand, and a high influence on the speed of work was a prognostic factor for symptoms in the low back. In the subgroup with highly monotonous repetitive computer work, the odds ratios of the prognostic factors were similar to those for the whole group of office workers. CONCLUSION: When organising computer work it is important to allow for physical variation with other work tasks, thereby avoiding working with the computer during all the work time, and further to consider the worker's own influence on the speed of work.

Adolescent↗
PubMed2006

A randomised controlled trial evaluating the effects of two workstation interventions on upper body pain and incident musculoskeletal disorders among computer operators.

BACKGROUND: Call centre work with computers is associated with increased rates of upper body pain and musculoskeletal disorders. METHODS: This one year, randomised controlled intervention trial evaluated the effects of a wide forearm support surface and a trackball on upper body pain severity and incident musculoskeletal disorders among 182 call centre operators at a large healthcare company. Participants were randomised to receive (1) ergonomics training only, (2) training plus a trackball, (3) training plus a forearm support, or (4) training plus a trackball and forearm support. Outcome measures were weekly pain severity scores and diagnosis of incident musculoskeletal disorder in the upper extremities or the neck/shoulder region based on physical examination performed by a physician blinded to intervention. Analyses using Cox proportional hazard models and linear regression models adjusted for demographic factors, baseline pain levels, and psychosocial job factors. RESULTS: Post-intervention, 63 participants were diagnosed with one or more incident musculoskeletal disorders. Hazard rate ratios showed a protective effect of the armboard for neck/shoulder disorders (HR = 0.49, 95% CI 0.24 to 0.97) after adjusting for baseline pain levels and demographic and psychosocial factors. The armboard also significantly reduced neck/shoulder pain (p = 0.01) and right upper extremity pain (p = 0.002) in comparison to the control group. A return-on-investment model predicted a full return of armboard and installation costs within 10.6 months. CONCLUSION: Providing a large forearm support combined with ergonomic training is an effective intervention to prevent upper body musculoskeletal disorders and reduce upper body pain associated with computer work among call centre employees.

Adult↗
PubMed1991

Environmental, occupational, and personal factors related to the prevalence of sick building syndrome in the general population.

Possible relations between prevalence of sick building syndrome (SBS) and environmental, occupational, and personal factors were studied in a random sample (0.1%) of the general population aged 20-65 in a three county region in middle Sweden. Childhood exposure to environmental tobacco smoke from smoking mothers and a childhood in urban areas was related to SBS symptoms. Current urban residency, fresh paint, and preschool children in the dwelling were also related to symptoms. Other residential factors such as age of building, type of building, degree of crowding, mechanical ventilation, or signs of moisture or mould growth were not related to symptoms. Other factors related to symptoms were history of atopy, allergy to nickel, proneness to infection, hyperreactivity, static electricity, work with video display units (VDU), work satisfaction, and climate of cooperation at work. Age, sex, marital state, education level, work stress, obesity, current or earlier smoking, regular physical exercise, or occupational exposure to chemicals did not correlate with symptoms. Women had a higher proportion of symptoms than men but these differences were not significant when adjusting for differences in allergy to nickel, hyperreactivity, and proneness to infection. Maternal smoking was related to a twofold increase of both atopy and allergy to nickel in the adult offspring. Eye symptoms were most common in administrative, managerial, and service work. Airway symptoms were most common in transport and communication work. Dermal symptoms were most common in professional and technical and related work. General symptoms were most common in service, health, hospital, and social work. The lowest prevalence of symptoms was found in agricultural, forestry, and sales work. Women and subjects allergic to nickel worked more often in occupations without exposure to chemicals, but no evidence was found for selection mechanisms causing sensitive persons to move from exposed to unexposed occupations. It was concluded that symptoms included in SBS are common in the general population, and of multifactorial origin related to both personal, occupational, and residential factors, and certain environmental exposures such as maternal smoking, the urban environment, VDU work, and volatile organic hydrocarbons from newly painted dwellings.

Adult↗
PubMed1992

Spontaneous abortion and work with visual display units.

OBJECTIVE: To determine whether women who work with visual display units are at increased risk of spontaneous abortion. DESIGN: Case-control study. SETTING: Women were recruited during the three years 1987-9 from the Royal Berkshire Hospital in Reading, and from a large group practice situated within the hospital's catchment area. SUBJECTS: Cases were 150 nulliparous working women with a clinically diagnosed spontaneous abortion and controls were 297 nulliparous working women attending for antenatal care. MAIN OUTCOME MEASURES: Cases and controls were contacted and personally interviewed using the same structured questionnaire. Exposure to visual display units (VDUs) at work was assessed from information supplied at interview. RESULTS: No evidence of an increased risk of spontaneous abortion was found in women who reported that they used a VDU at work compared with women who reported that they did not (odds ratio (OR) = 0.9, 95% confidence interval (95% CI) = 0.6-1.4); and no relation with the amount of time spent actively using a VDU was evident (OR = 0.9, 95% CI = 0.5-1.6 for women who worked with a VDU for 21 hours or more each week). No effect of passive exposure to VDUs at work was found (OR = 0.9, 95% CI = 0.6-1.6 for women who reported working less than 10 feet away from a VDU that was usually switched on). These findings were not explained by maternal age, marital state, housing tenure, partner's social class, educational level, smoking, alcohol consumption, or number of previous spontaneous abortions. CONCLUSION: Given the findings and their consistency with the results from other recent studies it is concluded that pregnant women who work with VDUs are not at increased risk of clinically diagnosed spontaneous abortion. For the many women who use VDUs in their jobs, this finding provides reassurance.

Abortion, Spontaneous↗
PubMed2003

Work related and individual predictors for incident neck pain among office employees working with video display units.

AIMS: To investigate work related and individual factors as predictors for incident neck pain among office employees working with video display units (VDUs). METHODS: Employees in three administrative units of a medium sized city in Finland (n = 515) received mailed questionnaires in the baseline survey in 1998 and in the follow up survey in 1999. Response rate for the baseline was 81% (n = 416); respondents who reported neck pain for less than eight days during the preceding 12 months were included into the study cohort as healthy subjects (n = 232). The follow up questionnaire 12 months later was completed by 78% (n = 180). Incident neck cases were those reporting neck pain for at least eight days during the preceding 12 months. RESULTS: The annual incidence of neck pain was 34.4% (95% CI 25.5 to 41.3). Poor physical work environment and poor placement of the keyboard increased the risk of neck pain. Among the individual factors, female sex was a strong predictor. Smoking showed a tendency for an increased risk of neck pain. There was an interaction between mental stress and physical exercise, those with higher mental stress and less physical exercise having especially high risk. CONCLUSION: In the prevention of neck disorders in office work with a high frequency of VDU tasks, attention should be given to the work environment in general and to the more specific aspects of VDU workstation layout. Physical exercise may prevent neck disorders among sedentary employees.

Adult↗
PubMed1992

Biological interactions and potential health effects of extremely-low-frequency magnetic fields from power lines and other common sources.

Various different effects of ELF magnetic fields have been reported to occur at the cellular, tissue, and animal levels. Certain effects, such as the induction of magnetophosphenes in the visual system, have been established through replication in several laboratories. Many other effects, however, have not been independently verified or, in some cases, replication efforts have led to conflicting results. A substantial amount of experimental evidence indicates that the effects of ELF magnetic fields on cellular biochemistry, structure, and function can be related to the induced current density, with a majority of the reported effects occurring at current density levels in excess of 10 mA/m2. These effects, therefore, occur at induced current-density levels that exceed the endogenous currents normally present in living tissues. From this perspective, it is extremely difficult to interpret the results of recent epidemiological studies that have reported a correlation between cancer incidence and exposure to 50-Hz or 60-Hz magnetic fields with very low flux densities. The levels of current density induced in tissue by occupational or residential exposure to these fields are, in nearly all circumstances, significantly lower than the levels found in laboratory studies to produce measurable perturbations in biological functions. There is a clear need for additional epidemiological research to clarify whether exposure to ELF magnetic fields is, in fact, causally linked to cancer risk. Laboratory animal studies conducted under controlled conditions are also needed to determine whether ELF magnetic fields can initiate or promote tumors. In addition, more studies of both a theoretical and experimental nature are needed to elucidate the molecular and cellular mechanisms through which low-intensity magnetic fields can influence living systems. A growing body of evidence indicates that cell membranes play a key role in the transduction and amplification of ELF field signals. Elucidation of the physical and biochemical pathways that mediate these transmembrane signaling events will represent a major advance in our understanding of the molecular basis of magnetic field effects of biological systems.

Bedding and Linens↗
PubMedDate not supplied

High-fidelity electronic display of digital radiographs.

A fully digital radiography system requires high-fidelity electronic display devices that preserve diagnostic quality. Current cathode-ray tube monitors do not meet desired performance criteria for displaying radiographs and have excessive size, weight, and power consumption. Recent developments in flat-panel display technology (in particular active-matrix liquid crystal displays, field-emission displays, and organic light-emitting displays) suggest that high-fidelity, lightweight displays will be available in the near future. Large-size active-matrix liquid crystal display devices have been demonstrated. High brightness can be easily achieved with bright back illumination. Further developments in optical design for monochrome displays should provide high fidelity and improve the angular dependence of the emitted light. Field-emission display devices have attractive emission distribution and potential for low veiling glare. This technology needs to be extended to a large area, and problems with cathode aging and nonuniformity have to be contemplated. Organic light-emitting displays represent a simple and potentially inexpensive display technology with the ability to achieve high image quality. However, extensive research and development is required to achieve large-area manufacturing methods.

Computer Terminals↗
PubMed2004

Effect of monitor luminance and ambient light on observer performance in soft-copy reading of digital chest radiographs.

PURPOSE: To examine the combined effects of monitor luminance and ambient light on observer performance for detecting abnormalities in a soft-copy interpretation of digital chest radiographs. MATERIALS AND METHODS: A total of 254 digital chest radiographs were displayed on a high-resolution cathode ray tube monitor at three luminance levels (25, 50, and 100 foot-lamberts) under three ambient light levels (0, 50, and 460 lux). Six chest radiologists reviewed each image in nine modes of combined luminance and ambient light. The observers were allowed to adjust the window width and level of the soft-copy images. The abnormalities included nodule, pneumothorax, and interstitial disease. Observer performance was analyzed in terms of the receiver operating characteristics. The observers reported their subjective level of visual fatigue with each viewing mode. A statistical test was conducted for each of the abnormalities and for fatigue score by using repeated-measures two-way analysis of variance with an interaction. RESULTS: The detection of nodules was the only reading that was affected by the ambient light with a statistically significant difference (P <.05). Otherwise, observer performance for detecting a nodule, pneumothorax, and interstitial disease was not significantly different in the nine-mode comparison. There was no evidence that the luminance of the monitors was related to the ambient light for any of the abnormalities. The fatigue score showed a statistically significant difference due to both the luminance and ambient light. CONCLUSION: When adequate window width and level are applied to soft-copy images, the primary diagnosis with chest radiographs on the monitor is unlikely to be affected under low ambient light and a monitor luminance of 25 foot-lamberts or more.

Computer Terminals↗
PubMed1993

Subtle orthopedic fractures: teleradiology workstation versus film interpretation.

The purpose of this study was to evaluate whether radiologists perform equally well with plain radiographs or digitized images displayed on a video monitor in interpretation of difficult orthopedic trauma cases. Interpretations with film and those made from a teleradiology system with spatial resolution of 2.35 line pairs per millimeter were compared in 120 difficult cases, 60 with the selected abnormality (ie, fracture or dislocation) and 60 that were control cases. Seven senior radiology residents and one radiology fellow each interpreted 60 randomly ordered cases with the teleradiology system (1,280 x 1,024-pixel monitors) and 60 cases with the original radiographs. The overall accuracy of the readers was 80.6% for film interpretations and 59.6% for teleradiology screen readings (P < .001). Sensitivity was 78.5% for film and 48.8% for on-screen images (P < .001), and specificity was 83.2% for film and 72.3% for on-screen images (P < .025). Receiver operating characteristic analysis showed rejection of the null hypothesis in favor of film interpretation (P < .0049). It was concluded that the teleradiology system was not acceptable for primary diagnostic interpretation of difficult fracture cases.

Computer Terminals↗
PubMedDate not supplied

Importance and effects of altered workplace ergonomics in modern radiology suites.

The transition from a film-based to a filmless soft-copy picture archiving and communication system (PACS)-based environment has resulted in improved work flow as well as increased productivity, diagnostic accuracy, and job satisfaction. Adapting to this filmless environment in an efficient manner requires seamless integration of various components such as PACS workstations, the Internet and hospital intranet, speech recognition software, paperless electronic hospital medical records, e-mail, office software, and telecommunications. However, the importance of optimizing workplace ergonomics has received little attention. Factors such as the position of the work chair, workstation table, keyboard, mouse, and monitors, along with monitor refresh rates and ambient room lighting, have become secondary considerations. Paying close attention to the basics of workplace ergonomics can go a long way in increasing productivity and reducing fatigue, thus allowing full realization of the potential benefits of a PACS. Optimization of workplace ergonomics should be considered in the basic design of any modern radiology suite.

Asthenopia↗