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PubMed2006

Optimization of reading conditions for flat panel displays.

Task Group 18 (TG 18) of the American Association of Physicists in Medicine has developed guidelines for Assessment of Display Performance for Medical Imaging Systems. In this document, a method for determination of the maximum room lighting for displays is suggested. It is based on luminance measurements of a black target displayed on each display device at different room illuminance levels. Linear extrapolation of the above luminance measurements vs. room illuminance allows one to determine diffuse and specular reflection coefficients. TG 18 guidelines have established recommended maximum room lighting. It is based on the characterization of the display by its minimum and maximum luminance and the description of room by diffuse and specular coefficients. We carried out these luminance measurements for three selected displays to determine their optimum viewing conditions: one cathode ray tube and two flat panels. We found some problems with the application of the TG 18 guidelines to optimize viewing conditions for IBM T221 flat panels. Introduction of the requirement for minimum room illuminance allows a more accurate determination of the optimal viewing conditions (maximum and minimum room illuminance) for IBM flat panels. It also addresses the possible loss of contrast in medical images on flat panel displays because of the effect of nonlinearity in the dependence of luminance on room illuminance at low room lighting.

Computer Terminals↗
PubMed1994

PACS for radiology conferences--improvement of application software.

The introduction of PACS in a radiology department means that most functions that are available in the film-based system must be included. One important function is the radiology conference. The handling and application programs of digital workstations are normally not developed for demonstrations of many images in a limited time. This paper describes a workstation with specially designed software for radiology conferences. The application is separated in preparation and presentation of the cases to be demonstrated. Very fast image handling is achieved during the conference because the function is based on the principle of prefetching of the selected images. The images are presented on a large screen with high resolution. The experiences of digital radiology conferences are good. However, reference films from previous examinations create extra work because they have to be shown on the conventional lightbox.

Computer Terminals↗
PubMed2003

Microplate based biosensing with a computer screen aided technique.

Melanophores, dark pigment cells from the frog Xenopus laevis, have the ability to change light absorbance upon stimulation by different biological agents. Hormone exposure (e.g. melatonin or alpha-melanocyte stimulating hormone) has been used here as a reversible stimulus to test a new compact microplate reading platform. As an application, the detection of the asthma drug formoterol in blood plasma samples is demonstrated. The present system utilizes a computer screen as a (programmable) large area light source, and a standard web camera as recording media enabling even kinetic microplate reading with a versatile and broadly available platform, which suffices to evaluate numerous bioassays. Especially in the context of point of care testing or self testing applications these possibilities become advantageous compared with highly dedicated comparatively expensive commercial systems.

Animals↗
PubMed1997

Differences in time to interpretation for evaluation of bone radiographs with monitor and film viewing.

RATIONALE AND OBJECTIVES: The authors evaluated how observers search hard-copy versus soft-copy images to determine why viewing times are longer for images displayed on a monitor. METHODS: Twenty-seven nonconsecutive bone-trauma computed radiographs were collected from the routine emergency practice. Eye positions of three bone radiologists and three orthopedic surgeons were recorded as they searched images on a view box and digital images at a workstation. RESULTS: Overall viewing time was longer for images displayed on a monitor. Time to first fixate a lesion and true-negative dwell times were significantly longer with the monitor than with the film. Absolute numbers of clusters and dwell times were greater for diagnostic image areas on the monitor than on the film. Twenty percent of the clusters for images viewed on the monitor were on the image-processing menu. CONCLUSION: The amount and type of information that is processed during search is different when images are viewed on a monitor rather than on film.

Bone and Bones↗
PubMed2003

Aliasing in the visual EEG: a potential pitfall of video display technology.

Computerized clinical electroencephalographic (EEG) systems are now widely used, with interpretation performed solely on video monitors. The possibility of artifacts from aliasing of EEG data on a computer screen has received little attention. We describe and illustrate several examples. Photographs of the video display were used. Three cases are shown. Two had escaped initial review and one led to transient changes in patient management. Aliasing artifacts are seen frequently with computerized EEG systems; some may be misinterpreted as EEG activity. Even compliance with current guidelines may not prevent all such artifacts.

Adult↗
PubMed1997

Application of a three-dimensional reconstruction method to analysis of the residual ridge.

The purpose of this study was to develop a new method of analysing the shape of the residual ridge. The line of the residual ridge crest was regarded as the reference for artificial tooth arrangement and a method of determining it was evaluated. The shape of a plaster model was measured with a contact-type shape measurement system. The measurement data in each frontal section were interpolated by cubic splines. The points corresponding to the residual ridge crest were calculated and superimposed onto the image of the plaster model on a monitor screen of an image processor. Using these points and the image of the plaster model, the line of the residual ridge crest was marked on the plaster model. It was concluded that this method could be used to determine the line of the residual ridge crest on a plaster model.

Algorithms↗
PubMed2002

Full-screen magnification for windows using DirectX Overlays.

This paper presents the basic features of software-based magnifiers used by some visually impaired people to read information from a computer screen. The paper briefly presents two major approaches to full-screen magnification for modern multiple window systems (the paper focuses on Microsoft Windows). This paper describes in detail the architecture and operation of a full-screen magnifier that uses Microsoft DirectX Overlays. This approach leads to a robust magnifier that has a low computational overhead. The magnifier has problems with video cards that use a YUV color model but these problems may be addressed by RGB to YUV translation software--an issue that is still to be investigated. The magnifier also has problems when the generic device driver, rather than the manufacturer's device driver, is installed on the system. The paper presents two further strategies for full screen magnification, namely, using multimonitor support and true type fonts for text enlargement.

Algorithms↗
PubMed2005

Effect of VDT keyboard height and inclination on musculoskeletal discomfort for wheelchair users.

This study investigated the effect of keyboard height and inclination on musculoskeletal discomfort for wheelchair users. Eight Taiwanese male wheelchair users (28.75 +/- 8.75 years) were recruited as participants to perform nine experimental combinations of data entry tasks. Three keyboard heights and three inclinations were evaluated. Musculoskeletal discomfort was estimated by Rating of Perceived Exertion and Subjective Preference Ranking. Each subject performed a data entry task for all nine experimental combinations in a random order. The seated posture of all participants during the data entry operation was the upright posture. The height of the screen's center was adjusted according to the eye level of each subject. Analysis showed the keyboard height and keyboard inclination significantly affected rating of musculoskeletal discomfort. It is suggested that the optimum keyboard height choice is elbow-level height or 5 cm below elbow level with the keyboard inclination horizontal to the seat of the wheelchair.

Adult↗
PubMed1995

Problems with integrating legacy systems.

The economic and organizational impact of imposing state-of-the-art technology to the large number of proprietary legacy systems operational in most hospitals requires integrated clinical professional workstations to provide flexible encapsulation mechanisms for these systems rather than reengineering these systems to this new technology. In this paper the implications of different input/output and translation models of legacy systems for their integration into a clinical workstation is described. Examples of legacy systems that have been integrated in the HERMES clinical workstation are presented as examples of the range of difficulties one might encounter. The features that an integrated workstation should offer for integrating a broad range of legacy systems are also addressed in this paper.

Computer Systems↗
PubMedDate not supplied

[The individual typological characteristics of operator activity during long-term monotonous work on the computer].

Individual neurophysiological and psychophysiological characteristics were analyzed in two groups of subjects with different extraversion and genetically determined levels of cortical activity during learning the novel for them monotonous computer operation. Most of the subjects improved their performance to the end of four-hour work. The degree of visual fatigue correlated with changes in P70 component of the evoked potentials. The intergroup difference was revealed in overcoming the visual discomfort during attention concentration. The visual cortex was facilitated in the introverts with high-voltage cortical activity (1st group) and disfacilitated in the extraverts with the low-voltage cortical activity (2nd group). Increase of the simple motor reaction time in the extraverts is considered as a result of temporary impairment of the visual function during the monotonous operator's work, and the worsening of the emotional condition as a consequence of the visual discomfort. The problems are discussed concerning different adaptation mechanisms in realization of the activity under study depending on the genetically determined features of the CNS.

Adaptation, Physiological↗
PubMed1994

End-tidal PCO2 as an index of psychophysiological activity during VDT data-entry work and relaxation.

The present study was designed to assess the utility of end-tidal PCO2 (peak concentration of carbon dioxide in a single breath of exhaled air) as an index of psychophysiological activity during performance of a computer-based task and during relaxation. Eleven data-entry operators were monitored continuously for three consecutive, 6 hour work days under the following conditions: (a) during a self-relaxation baseline period; (b) during an abbreviated progressive muscle relaxation period; and (c) during a period of computer-based data-entry work. End-tidal PCO2, respiration frequency, and cardiac inter-beat interval (a measure of heart rate and its variability) were monitored continuously during the three conditions of the study. Self-ratings of relaxation and tension were also monitored at periodic intervals. Consistent with a decrease in psychophysiological arousal, end-tidal PCO2 and self-ratings of relaxation were significantly higher during progressive muscle relaxation than during baseline relaxation. Consistent with an increase in psychophysiological arousal, end-tidal PCO2, cardiac inter-beat interval, and relaxation ratings during data-entry work were significantly lower than during either baseline relaxation or progressive muscle relaxation, while respiration frequency and tension ratings were higher. The findings indicate that end-tidal PCO2 discriminates among different psychophysiological states, and that end-tidal PCO2 may be useful in indexing the stress-health effects of human-computer interactions.

Adult↗
PubMed1997

P31 phosphor persistence at photopic mean luminance level.

P31 phosphor screens are frequently used for short-term presentation of dot and grating patterns, but experimental data obtained with this technique have been criticized because of possible parasitic effects of phosphor persistence on subjects visual performance. Recently, this issue provoked a controversial discussion in Vision Research (Groner et al., 1993; Westheimer, 1993, 1994; Irwin, 1994; Di Lollo et al., 1994) which was concerned with persistence effects of P31 screens for dot patterns. Supplementing this discussion, the present work deals with the effects of different types of patterns (dot pattern vs. gratings) and background mean-luminance levels (scotopic vs. phototopic) on phosphor persistence. Physical measurements of P31 persistence occurring with grating patterns of a mean luminance of 20 cd m-2 (i.e. photopic range) were obtained by using an extremely linear photometer with high temporal resolution. Under this photopic condition, the measurements demonstrate a fast decay of residual grating contrast to 1.4% of its original value within 50 ms after pattern offset. This phosphor behavior must be considered when designing an experiment with a P31 screen though it certainly embodies no problems in many applications.

Computer Terminals↗
PubMed1990

Congenital malformations among children of women working with video display terminals.

In a case-base study among 214,108 commercial and clerical employees in Denmark the potential effect of the use of video display terminals on the risk of congenital malformations in pregnancy was investigated. The study base was identified by means of register linkage of the Medical Birth Register and the National Register of In-Patients. In the source population 24,352 pregnancy outcomes were registered, 661 of which with congenital malformations entered the case group, and a base sample of 2252 pregnancies was drawn. Data concerning the use of video display terminals, job stress, ergonomic factors, exposure to organic solvents, and life-style factors were obtained from postal questionnaires. The results of this study did not support the hypothesis that the use of video display terminals during pregnancy is associated with an increased risk of congenital malformations.

Adolescent↗
PubMedDate not supplied

[Modular project of the Picture Archiving and Communication System (PACS). Preliminary clinical experience. II].

In the previous paper in this volume the PAC System installed in the Radiology Department of the University of Trieste has been described and its advantages and limitations have been analyzed, mainly from an operational point of view. This paper deals with the clinical evaluation of the system in ordinary operative conditions. A series of cases with specific characteristics was monitored in order to reveal different performances in both diagnostic process and conclusions using the PACS viewing console (DW) vs. conventional CRT film images on alternators. In a first test, 100 routine (not pre-selected) brain CT cases were independently analyzed by 4 radiologists, each of them giving 2 interpretations of the same case, one based on film and the other on PACS. The data were analyzed by conventional statistical methods, showing a substantial agreement of the results obtained with the 2 modalities. A second test concerned the evaluation of 100 lumbar intervertebral disks by CT, with the same procedure as above. Four radiologists were again asked to decide on film and PACS images about normality, protusion, or herniation of the disks. The results demonstrate the possibility of adequately reporting on the PACS monitor and stress the need of an adequate training period and the efficacy of the image processing capabilities of the system.

Brain Diseases↗
PubMed1992

The effects of continuous exposure to 20-kHz sawtooth magnetic fields on the litters of CD-1 mice.

Mated CD-1 mice were exposed to 20-kHz sawtooth magnetic fields similar to those associated with video display terminals (VDT). Four groups of animals were continuously exposed from day 1 to day 18 of pregnancy to field strengths of 0, 3.6, 17, or 200 microT. There were no less than 185 mated dams in each exposure group. On day 18, the dams were sacrificed and assessed for weight gain and pregnancy. The litters were evaluated for numbers of implantations, fetal deaths and resorptions, gross external, visceral and skeletal malformations, and fetal weights. There were no less than 140 pregnant females in each group, and there were no significant differences between any of the exposure groups and the sham group (0 microT) for any of the end points. The results of this study do not support the hypothesis that the 20-kHz VLF magnetic fields associated with video display terminals are teratogenic in mammals.

Abnormalities, Radiation-Induced↗
PubMed2006

Detection of masses and microcalcifications of breast cancer on digital mammograms: comparison among hard-copy film, 3-megapixel liquid crystal display (LCD) monitors and 5-megapixel LCD monitors: an observer performance study.

The purpose of the study was to compare observer performance in the detection of masses and microcalcifications of breast cancer among hard-copy reading and soft-copy readings using 3-megapixel (3M) and 5-megapixel (5M) liquid crystal display (LCD) monitors. For the microcalcification detection test, we prepared 100 mammograms: 40 surgically verified cancer cases and 60 normal cases. For the mass detection test, we prepared 100 mammograms: 50 cancer cases and 50 normal cases. After six readers assessed both microcalcifications and masses set for each modality, receiver operating characteristic (ROC) analysis was performed. The average A(z)s for mass detection using a hard copy and 3M and 5M LCD monitors were 0.923, 0.927 and 0.920, respectively; there were no significant differences. The average A(z) for microcalcification detection using hard copy, 3M and 5M LCD monitors was 0.977, 0.954 and 0.972, respectively. There were no significant differences, but the P-values between the hard copy and 3M LCD monitor and that between the 3M and 5M LCD monitor were 0.08 and 0.09, respectively. In conclusion, the observer performances for detecting masses of breast cancers were comparable among the hard copy and two LCD monitors; however, soft-copy reading with a 3M LCD monitor showed slightly lower observer performance for detecting microcalcifications of breast cancers than hard-copy or 5M LCD monitor reading.

Adult↗
PubMed1989

Microcomputer-controlled administration of vasodilators following cardiac surgery: technical considerations.

Hypertension in the early postoperative period after cardiopulmonary bypass is associated with increased morbidity, and is commonly managed by the infusion of short-acting vasodilators. Automatic arterial blood pressure control by closed-loop infusion has been shown to be superior to manual control in several studies. The investigators have developed a closed-loop arterial pressure control system based on the Atari 1040ST microcomputer (Atari, Sunnyvale, CA). The program uses a proportional-integral-derivative control algorithm, developed from that described by Sheppard and his colleagues. The arterial waveform is sampled digitally, and the waveform analysis routine incorporates several artifact detection and rejection functions. Additional safety features are provided in the computer-infusion pump subroutine, which cause alarms to be activated if computer-pump communication fails to occur within a specified time period. A novel feature of this system is the clinical staff's use of a "mouse" to enter data and control the program, which makes keyboard skills unnecessary. This system is in routine service in the cardiac intensive care unit (CICU), both for direct clinical use and for research into various aspects of arterial pressure control, and has proved to be acceptable to the clinical staff.

Algorithms↗
PubMed2005

Are simple feedback interventions involving workplace data associated with better working environment and health? A cluster randomized controlled study among Swedish VDU workers.

OBJECTIVE: To test whether feedback and discussion of ergonomic and psychosocial working environment data during 1 short session with individual, groups, or supervisors of VDU workers had effects on (1) the quality of implemented modifications in workplace design, working technique, or psychosocial aspects; (2) psychological demands, decision latitude, and social support; (3) comfort during computer work, emotional stress, and prevalence of musculoskeletal symptoms or eye discomfort. METHODS: Thirty-six workgroups from 9 organizations were randomized to 3 feedback conditions (individual, workgroup, supervisor) or control. Follow-up was 6 months after intervention. Questionnaire data aggregated on the workgroup level were used. RESULTS: Effect (positive) on social support was indicated from feedback to supervisors. CONCLUSION: Feedback and discussion of ergonomic and psychosocial working environment data with supervisors of white-collar VDU workers may have positive effect on social support measured as a group characteristic. Sources of potential bias are discussed.

Adult↗