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PubMed2000

Frequency and impact of high-resolution monitor failure in a filmless imaging department.

The purpose of this study was to assess the image quality and the rate of failure of the high-resolution (2,048 x 1536 pixel) monitors used for primary diagnosis in a filmless radiology department and to analyze the type of problems encountered as well as the action taken to repair the monitors. Data were collected from Picture Archival and Communication System (PACS) service logs to determine rates of monitor adjustment and replacement, the symptoms reported, and the action taken. Additionally, random surveys of the high-resolution monitors were performed using a standard test pattern to assess spatial and contrast resolution in the center and outer corners of the monitors. Analysis of monitor service records showed a high rate of monitor replacement (41% per year) resulting in a relatively short "life expectancy" (defined as average time required before replacement) of 2.4 years. Random surveys of monitor quality using a standard test pattern showed suboptimal image quality in approximately 54% of the monitors with moderate image quality degradation present in at least one region of 27% of the high-resolution monitors, despite our vendor's quality control program. The results of this study support our subjective impression and those of other colleagues in the PACS community of an unacceptably high monitor failure rate and persistent image quality problems with 2,000 pixel monitors used for primary diagnosis. The relatively high incidence of suboptimal quality monitors suggests that more frequent quality control should be performed using a test pattern particularly given the fact that radiologists often are unable to discern degradation of monitor performance using clinical images. The high incidence of problems with image quality on high-resolution monitors indicates that vendors need to develop better quality control in monitor design and testing. Radiologists should review briefly a test pattern on each monitor at the beginning of each day. A computer program should be incorporated into the PACS, which asks radiologists to evaluate a test pattern and records the results in a central database, which is communicated to the service engineers. Further studies should be evaluated to determine the clinical impact of monitor image degradation, which is relatively easily seen using a test pattern but may be difficult to discern on clinical images. Requests for proposals (RFPs) for PACS and service contracts must specify carefully requirements for monitor image quality and conditions under which the vendor is required to replace these monitors.

Computer Terminals↗
PubMed2001

Quality-control issues on high-resolution diagnostic monitors.

Previous literature indicates a need for more data collection in the area of quality control of high-resolution diagnostic monitors. Throughout acceptance testing, which began in June 2000, stability of monitor calibration was analyzed. Although image quality on all monitors was found to be acceptable upon initial acceptance testing using VeriLUM software by Image Smiths, Inc (Germantown, MD), it was determined to be unacceptable during the clinical phase of acceptance testing. High-resolution monitors were evaluated for quality assurance on a weekly basis from installation through acceptance testing and beyond. During clinical utilization determination (CUD), monitor calibration was identified as a problem and the manufacturer returned and recalibrated all workstations. From that time through final acceptance testing, high-resolution monitor calibration and monitor failure rate remained a problem. The monitor vendor then returned to the site to address these areas. Monitor defocus was still noticeable and calibration checks were increased to three times per week. White and black level drift on medium-resolution monitors had been attributed to raster size settings. Measurements of white and black level at several different size settings were taken to determine the effect of size on white and black level settings. Black level remained steady with size change. White level appeared to increase by 2.0 cd/m2 for every 0.1 inches decrease in horizontal raster size. This was determined not to be the cause of the observed brightness drift. Frequency of calibration/testing is an issue in a clinical environment. The increased frequency required at our site cannot be sustained. The medical physics division cannot provide dedicated personnel to conduct the quality-assurance testing on all monitors at this interval due to other physics commitments throughout the hospital. Monitor access is also an issue due to radiologists' need to read images. Some workstations are in use 7 AM to 11 PM daily. An appropriate monitor calibration frequency must be established during acceptance testing to ensure unacceptable drift is not masked by excessive calibration frequency. Standards for acceptable black level and white level drift also need to be determined. The monitor vendor and hospital staff agree that currently, very small printed text is an acceptable method of determining monitor blur, however, a better method of determining monitor blur is being pursued. Although monitors may show acceptable quality during initial acceptance testing, they need to show sustained quality during the clinical acceptance-testing phase. Defocus, black level, and white level are image quality concerns, which need to be evaluated during the clinical phase of acceptance testing. Image quality deficiencies can have a negative impact on patient care and raise serious medical-legal concerns. The attention to quality control required of the hospital staff needs to be realistic and not have a significant impact on radiology workflow.

Calibration↗
PubMed2001

Calibration of medium-resolution monochrome cathode ray tube displays for the purpose of board examinations.

This report discusses calibration and set-up procedures for medium-resolution monochrome cathode ray tubes (CRTs) taken in preparation of the oral portion of the board examination of the American Board of Radiology (ABR). The board examinations took place in more than 100 rooms of a hotel. There was one display-station (a computer and the associated CRT display) in each of the hotel rooms used for the examinations. The examinations covered the radiologic specialties cardiopulmonary, musculoskeletal, gastrointestinal, vascular, pediatric, and genitourinary. The software used for set-up and calibration was the VeriLUM 4.0 package from Image Smiths in Germantown, MD. The set-up included setting minimum luminance and maximum luminance, as well as positioning of the CRT in each examination room with respect to reflections of roomlights. The calibration for the grey scale rendition was done meeting the Digital Imaging and communication in Medicine (DICOM) 14 Standard Display Function. We describe these procedures, and present the calibration data in. tables and graphs, listing initial values of minimum luminance, maximum luminance, and grey scale rendition (DICOM 14 standard display function). Changes of these parameters over the duration of the examination were observed and recorded on 11 monitors in a particular room. These changes strongly suggest that all calibrated CRTs be monitored over the duration of the examination. In addition, other CRT performance data affecting image quality such as spatial resolution should be included in set-up and image quality-control procedures.

Calibration↗
PubMed2002

[Office workplace at a computer monitor from an occupational-orthopedic view].

Typical back problems as well as complaints in the shoulder-arm-hand system are increasing as the volume of sedentary office work at the computer screen rises. Various legal rules precisely define preventive measures. However, basic orthopedic-biomechanical principles are not being taken into consideration. Orthopedists as well as occupational physicians are equally challenged to enforce those legal guidelines by beginning to raise awareness of the principles and thus contributing towards improvement of working conditions.

Computer Terminals↗
PubMed2004

Visual afferent information dominates other sources of afferent information during mixed practice of a video-aiming task.

The goal of the present study was to determine whether learning of a manual video-aiming task that would have to be performed in a target-only condition (transfer test) would be improved, unaffected or hindered by alternating practice between a normal vision and a target-only condition. The results of the present study indicate that a mixed schedule of practice hindered learning of the task. Specifically, participants who practiced the task in the mixed schedule showed larger direction constant error in transfer than participants who practiced only in the target-only condition. The results suggest that participants in the mixed condition continued to rely on the rapidly decaying information that was extracted in the normal vision condition to plan and control their movement in the target-only condition, which ultimately led to biased movement endpoints.

Adult↗
PubMed1999

Complete cDNA sequences of the DRB6 gene from humans and chimpanzees: a possible model of a stop codon readingthrough mechanism in primates.

The defective major histocompatibility complex (MHC) DRB6 gene is transcribed into mRNA in human [peripheral blood lymphocytes, transfected and Epstein-Barr virus (EBV)] and chimpanzee EBV cell lines. MHC-DRB6 presents several anomalies, which include stop codons in exon 2, lack of the usual polyadenilation signal of other MHC-DRB genes, and a promoter region and exon 1 taken from a locally inserted retrovirus. The complete cDNA sequences from human DRB6*0201 and three common chimpanzee alleles (Patr-DRB6*0108, Patr-DRB6*0109, Patr-DRB6*0111) have been obtained; two exon 1-exon 2 cDNA sequences from bonobos (Papa-DRB6*0101 and Papa-DRB6*0102) are also shown. In contrast to chimpanzee DRB6 transcripts, the human ones: (1) present an exon 1-exon 2 splicing site that includes the transcription of the first 141 nucleotides of intron 1, rendering a longer exon 1, and (2) show a duplication of exon 6, which would render a longer cytoplasmic tail in a putative DRB6 protein. These two characteristics are found in all the human sequences obtained, regardless of the cellular type tested, and they are not present in any of the chimpanzee alleles reported; consequently, they are human-specific. All the alleles reported here bear stop codons in the three possible reading frames; however, a certain level of expression of DRB6 has been observed by cytofluorometry. This could be due to the presence of a selenocysteine insertion sequence (SECIS) stem-loop structure located at the 3 untranslated region of the DRB6 mRNA, which directs selenocysteine incorporation at UGA codons. DRB6 transcription and translation would be the first gene model of a readingthrough stop codon mechanism in primate MHC. It is also feasible that the DRB6 gene might generate a population of short polypeptides, bound to plasmatic membranes, having non-antigen-presenting functions or which are presented by other MHC molecules as HLA-E presents HLA-G and -B leader sequence-derived peptides.

3' Untranslated Regions↗
PubMed2002

Resolution requirements for monitor viewing of digital flat-panel detector radiographs: a contrast detail analysis.

With the introduction of digital flat-panel detector systems into clinical practice, the still unresolved question of resolution requirements for picture archiving communication system (PACS) workstation monitors has gained new momentum. This contrast detail analysis was thus performed to define the differences in observer performance in the detection of small low-contrast objects on clinical 1K and 2K monitor workstations. Images of the CDRAD 2.0 phantom were acquired at varying exposures on an indirect-type digital flat-panel detector. Three observers evaluated a total of 15 images each with respect to the threshold contrast for each detail size. The numbers of correctly identified objects were determined for all image subsets. No significant difference in the correct detection ratio was detected among the observers; however, the difference between the two types of workstations (1K vs 2K monitors) despite less than 3% was significant at a 95% confidence level. Slight but statistically significant differences exist in the detection of low-contrast nodular details visualized on 1K- and 2K-monitor workstations. Further work is needed to see if this result holds true also for comparison of clinical flat-panel detector images and may, for example, exert an influence on the diagnostic accuracy of chest X-ray readings.

Computer Terminals↗
PubMed2004

Expert assessment of physical ergonomics at video-display unit workstations: repeatability, validity and responsiveness to changes.

AIMS: Inter-observer repeatability, validity and responsiveness to change were determined for an expert assessment method for video-display unit (VDU) workstation ergonomics. The aim was to determine to what extent the expert assessment of ergonomics is related to the technical measurements, tidiness and space, work chair ergonomics and responds to changes in these characteristics. METHODS: Technical measurements and video-recordings before and 2 months after an ergonomic intervention were made for 109 VDU office workstations. Two experts in ergonomics analysed and rated the ergonomics of the workstations. A researcher analysed tidiness and available space. A physiotherapist classified the work chairs used according to their ergonomic properties. RESULTS: The intra-class correlation coefficient between the workstation ergonomic ratings of the two experts was 0.74 at the baseline and 0.81 at the follow-up. Workstation tidiness and space, and work chair ergonomics, had a strong effect on the assessments of both experts. For both experts a change in the locations of the mouse, the screen and the keyboard and values of tidiness and space and work chair ergonomics during the intervention showed a significant association with the ratings. CONCLUSION: The assessment method studied can be utilized by an expert in a repeatable manner both in cross-sectional and in longitudinal settings.

Anthropometry↗
PubMed2006

What is known about temperature and complaints in the upper extremity? A systematic review in the VDU work environment.

UNLABELLED: Upper extremity musculoskeletal complaints and disorders are frequently reported among visual display units (VDU) workers. These complaints include cold forearms, hands or fingers. OBJECTIVE: The aim of this systematic review was to gain an insight into the relationship between objective and subjective temperature decrease and musculoskeletal disorders (MSDs) in the upper extremity in a VDU work environment by (internal or external) cooling of the arm and hand. Two questions were formulated: (1) Is a VDU work environment (temperature between 15 and 25 degrees C) associated with temperature decrease of the arm, hand or fingers in healthy subjects? (2) Is there a difference in arm, hand and finger temperature between patients with upper extremity MSDs and healthy subjects in a VDU work environment? METHODS: Through a systematic literature search in six databases between 1989 and October 2005, 327 articles were retrieved and 17 included. RESULTS: Forearm, hand and finger temperature significantly decreases when the ambient temperature (between 15 and 25 degrees C) decreases. The skin temperature in the hand that uses a computer mouse is lower than the other hand in the same ambient temperature. At baseline, no objective temperature differences are found between patient groups and controls, whereas in patients with cold hand complaints, lower skin temperatures are found compared to controls. The association between temperature (changes) in the forearm, hand or fingers during VDU work, and MSDs in the upper extremity is not clear. CONCLUSION: There is no consistent evidence available for the association between upper extremity MSDs and temperature changes in forearm, hand or fingers in an office work environment.

Computer Terminals↗
PubMed1998

Vibration sense in the upper limb in patients with repetitive strain injury and a group of at-risk office workers.

OBJECTIVES: To investigate in patients with repetitive strain injury (RSI) and in office workers using computer keyboard equipment (a) whether the vibration threshold in the hand was altered, (b) the immediate effects of keyboard use on vibration thresholds and (c) whether the tolerance of suprathreshold vibration was normal. METHOD: A vibrametre (Somedic Ab, Stockholm Sweden) was used to obtain threshold vibration measurements, by the method of limits, for all peripheral-nerve cutaneous distributions in the hand. Tolerance of suprathreshold stimulation was obtained by stimulation of the soft tissues of the forearm by increasing the amplitude of vibration. RESULTS: Thresholds for vibration were significantly raised for the median nerve in both the patient and office-worker groups. The patient group additionally had raised thresholds for the ulnar nerve. Following use of the keyboard, thresholds for the median nerve were further elevated in the patient group, but not in the other groups, demonstrating a work-related exacerbation. At suprathreshold stimulation. 14 members (82%) of the patient group experienced an allodynic response to vibration, indicating, possible changes in the central processing of non-noxious sensory information. This changed sensory response was not seen in either the office-worker or control groups. CONCLUSION: Patients may have a minor polyneuropathy, whereas the office workers demonstrate early signs of the condition. Quantitative measurement of vibration perception may prove useful in patient assessment and for detection of the early onset of RSI in the work environment.

Adult↗
PubMed1999

Surface EMG of shoulder and back muscles and posture analysis in secretaries typing at visual display units.

OBJECTIVE: A study was carried out to investigate temporal changes of activation of shoulder and back muscles in workers at visual display units by means of surface EMG. Moreover, postural parameters were recorded to distinguish fatigue-related from posture-related changes of the myoelectrical activity. METHODS: Nine healthy female office workers typed texts spoken from tape during three 1-h-long sessions. After the first and again after the second hour there was a break of 15 min. Sixteen-channel surface EMG was bipolarly recorded from the erector spinae, trapezius, deltoid and sternocleidomastoid muscles. Root mean square (RMS) and power spectrum median frequency of the EMG were calculated. Sitting posture was assessed using an eight-channel movement analysis system with ultrasound markers. The position of the seventh cervical spinous process and the left and the right acromion were analysed synchronously with the EMG characteristics using regression analysis. RESULTS: The normalised RMS of the left and right trapezius muscle increased, while the median frequency did not change. The increase of the normalised RMS was significantly lower when the linear influence of posture was excluded. On average, the distance between C7 and the left and right acromion decreased within each working an hour. C7 became lower on average by 5.5 mm within an hour, whereas the acromions became lower by only 1.7 mm (left) and 3.3 mm (right). CONCLUSION: The increase in trapezius muscle activity was partly related to a lifting of the shoulders to compensate a slight slumping of the back. Another part of the EMG activity increase has to be attributed to fatigue, to attention-related activity or to the combination of both. Therefore, training of the back muscles and a varied organisation of work might have a preventive effect with respect to musculoskeletal complaints in VDU workers.

Adult↗
PubMed2003

Motor unit identification in two neighboring recording positions of the human trapezius muscle during prolonged computer work.

Work-related shoulder-neck pain is a major health risk in computer operators. To understand the physiological mechanisms behind the development of these disorders, EMG recordings of some minutes up to several hours must be accurately decomposed. For this reason we developed EMG-LODEC, an automatic decomposition software program, especially designed for multi-channel long-term recordings of signals detected during slight muscle movements. The subjects executed a 30-min computer task to simulate real work conditions while working at an ergonomically designed workstation. Six-channel intramuscular EMG signals were recorded from two positions of the upper trapezius muscle. The EMG signals were decomposed into individual motor unit action potential trains using EMG-LODEC. The study design enabled us first to study the dependence of intramuscular analysis on the insertion points and second to test the accuracy of the decomposition technique under laboratory conditions during a real experiment. The two positions yielded 887 motor units--452 located in position 1 and 435 in position 2. Although the numbers of detected action potentials were strongly correlated between the two insertion positions, different motor units were mostly recorded. In particular, the detection of continuously active motor units is specific for the selected insertion points and may not be representative of a muscle, not even for parts with common functions. The approach for the quantitative evaluation of the decomposition technique was to independently decompose two signals that were simultaneously detected by separate sets of wire electrodes placed close to each other in the muscle. Common trains discovered in each signal were compared for consistency. A cross-correlation analysis was performed to find corresponding motor unit pairs that were concurrently active. Concurrently active motor units were found in six subjects. For these motor units the extent of simultaneous occurrence of motor unit action potentials between the two positions ranged from 23% to 78% depending on the distinction of the single motor units and the number of superimposed motor unit action potentials. High concordance was seen in 3 out of the 15 motor unit pairs. Based on the results, EMG-LODEC is capable of providing reliable decompositions with satisfying accuracy and reasonable processing time. EMG-LODEC is suitable for the study of motor unit discharge patterns and recruitment order in subjects with and without musculoskeletal pain during long-term measurements to study work-related musculoskeletal disorders.

Adult↗
PubMed2003

The effect of physical and psychosocial loads on the trapezius muscle activity during computer keying tasks and rest periods.

UNLABELLED: The overall aim was to investigate the effect of psychosocial loads on trapezius muscle activity during computer keying work and during short and long breaks. In 12 female subjects, surface electromyography (EMG) was recorded bilaterally from the upper trapezius muscle during a standardized one hand keying task-interspaced with short (30 s) and long (4 min) breaks-in sessions with and without a combination of cognitive and emotional stressors. Adding psychosocial loads to the same physical work did not increase the activity of the trapezius muscle on either the keying or the control side, both of which remained at median and static EMG activity levels of around 5% and 2.5% of the maximal voluntary electrical activity (EMG(max)), respectively. The difference between the keying and the control side was significant; and further the control side activity was significantly increased above resting level. During both short and long breaks, exposure to psychosocial loads also did not increase the activity of the trapezius muscle either on the side of the keying or the control hand. Of note is that during long breaks the muscle activity of the keying side as well as that of the control side remained at the same level as during the short breaks, which was increased above resting level. This was to be seen from the static and the median EMG activity levels as well as gap times, the overall mean values being: 0.4%EMG(max), 1.1%EMG(max), and 50% in gap time, respectively. IN CONCLUSION: psychosocial loads are not solely responsible for increased non-postural muscle activity; and increasing the duration of breaks does not per se cause muscle relaxation.

Activities of Daily Living↗
PubMed2006

Eye blink frequency during different computer tasks quantified by electrooculography.

The purpose of the study was to evaluate electrooculography (EOG) as an automatic method to measure the human eye blink frequency (BF) during passive and interactive computer tasks performed at two screen heights. Ten healthy subjects (5 males and 5 females) participated in the study in a 23 degrees C temperature and 30-35% relative humidity controlled simulated office environment. Each test subject completed a 2 x 10 min active task of computer work and a 3 x 10 min passive task of watching a film on a video display unit (VDU). Both tasks included two viewing angles: standard (the monitors' upper edge was in the same height as the subjects' eyes) and low (lowered by 25 degrees). EOG signals were recorded with two Ag/AgCl surface electrodes positioned above and below the right eye, and a reference electrode was placed behind the ear. The experiments were video filmed, and eye blinks were counted manually from the video recordings and compared to the EOG measurements. The method showed a high validity to detect blinks during computer work: 95.4% of the blinks were retrieved by the EOG method and very few artefacts from eye movements were erroneously classified as eye blinks (2.4%). By use of the EOG method, the computer task was found to significantly decrease the BF by 69% compared to the passive task (P < 0.001), and a small decrease (12-14%) was found by lowering the viewing angle by 25 degrees.

Adult↗
PubMed2001

Ergonomic principles of task alignment, visual display, and direction of execution of laparoscopic bowel suturing.

BACKGROUND: Laparoscopic suturing is technically a demanding skill in laparoscopic surgery. Ergonomic experimental studies provide objective information on the important factors and variables that govern optimal endoscopic suturing. Our objective was to determine the optimum physical alignment, visual display, and direction of intracorporeal laparoscopic bowel suturing using infrared motion analysis and telemetric electromyography (EMG) systems. METHODS: Ten surgeons participated in the study; each sutured 50-mm porcine small bowel enterotomies toward and away from the surgeon in the vertical and horizontal bowel plane with either isoplanar (image display corresponds with actual lie of the bowel) or nonisoplanar (bowel displayed horizontally but mounted vertically in the trainer and vice versa) display. The end points were the placement error score, execution time, leakage pressure, motion analysis, and telemetric EMG parameters of the surgeon's dominant upper limb. RESULTS: Suturing was demonstrably easier in the vertical than in the horizontal plane, resulting in a better task quality (placement error score, p < 0.0001; leakage pressure, p < 0.005) and shorter execution time (p < 0.05). Nonisoplanar display of the surgical anatomy degrades performance in terms of both task efficiency and task quality. On motion analysis, a wider angle of excursion and lower angular velocity were observed during the vertical suturing with isoplaner display. Compared to horizontal suturing, supination at the wrist was significantly greater during vertical than horizontal suturing (p < 0.05). Within each category (vertical vs horizontal suturing), the direction of suturing (toward/away from the surgeon) did not influence the extent of pronation/ supination at the wrist. In line with the degraded performance, significantly more muscle work was expended during horizontal suturing. This affected the forearm flexors (p < 0.05), arm flexors and extensors (p < 0.005 and p < 0.05, respectively), and deltoid muscles (p < 0.005) and was accompanied by significantly more fatigue in the related muscles. Small bowel enterotomies sutured toward the surgeon in both the vertical and the horizontal planes exhibited less placement error score than when sutured away from the surgeon, with no significant difference in the motion analysis and EMG parameters. CONCLUSIONS: Optimal laparoscopic suturing (better task quality and reduced execution time) is achieved with vertical suturing toward the surgeon with isoplanar monitor display of the operative field. The poorer task performance observed during horizontal suturing is accompanied by more muscle work and fatigue, and it is not improved by monitor display of the enterotomy in the vertical plane.

Animals↗
PubMed2001

Evaluation of the usability of two types of image display systems, during laparoscopy.

BACKGROUND: This study was performed to assess the optimal display location of a flat-screen monitor for laparoscopy. It was also performed to assess the posture (objective), opinion, and preference (subjective) of subjects using a flat-screen monitor positioned in the optimal display location and a cathode-ray tube monitor on a tower next to the operating table (current situation). METHODS: Twelve surgeons performed cholecystectomies using the two display systems alternately. The postures of the operator and the assistant were assessed by an infrared video analysis system. RESULTS: The posture of the assistant is significantly better when using a flat-screen monitor [more neutral head flexions (p = 0.036) and neutral neck torsions (p = 0.012)]. No significant differences were found for the posture of the operator. The operators and assistants felt more comfortable when using a flat-screen monitor (p = 0.008) and they preferred this display to the use of a monitor on a tower. CONCLUSIONS: The use of flat-screen monitors is better for the physical and psychological comfort of the users, even though the technical performance is inferior in comparison with that of regular monitors.

Cholecystectomy↗