A 90-DEGREE PHASE DIFFERENCE NETWORK FOR CIRCULAR DISPLAY OF THE EEG ON A CATHODE RAY TUBE.
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Cathode Ray Tube↗
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Comparison of conventional fluorescein angiography film images with a cathode ray tube display.
We evaluated the effectiveness of cathode ray tube (CRT) displays in the transfer of diagnostic information to the ophthalmologist. Retinal fluorescein angiography images were used and data were taken using the receiver operating characteristic experimental paradigm. Three ophthalmologists with experience ranging from two to 12 years participated in the study. Sixty-eight images were selected from proof sheets of 800 original images. Next, these images were digitized, then each set was shown on its respective display (slide projection for the proof sheet images and CRT for the digital images). These 68 images were from a variety of patients and represented a broad range of normal and abnormal retinas (including diabetic retinopathy, hypertension independent of diabetes, and sickle-cell disease). Results show (1) that there is no difference between the systems in terms of diagnostic accuracy; (2) that certainty of diagnosis was not a function of the system; and (3) that although there was an effect due to experience of the ophthalmologist, it did not affect diagnosis accuracy. We conclude that CRT displays at conventional video resolutions can deliver the needed diagnostic information as well as film. We also hypothesize that digital enhancement techniques can increase the available diagnostic information beyond that of film.
Computer Systems↗
Cathode-ray tube displays for medical imaging.
This paper will discuss the principles of cathode-ray tube displays in medical imaging and the parameters essential to the selection of displays for specific requirements. A discussion of cathode-ray tube fundamentals and medical requirements is included.
Data Display↗
Radioactivity in cathode ray tubes.
While surveying used computer equipment out of a zone posted as a Contamination Area, 100% of the computer monitors surveyed had levels of radioactivity that were significantly above background. The radioactivity was primarily on the front face of the cathode ray tube and was not amenable to decontamination. Hot spots were found also along the edges and seals of the cathode ray tube. Similar surveys of computer monitors that were never in Contamination Areas confirmed that radioactivity was incorporated into the monitor. Surveys were made of recently manufactured television sets with similar results. Gamma spectroscopy indicates that the radioactivity is due to naturally occurring radioactive materials. Since most surveys of cathode ray tubes in the literature were made while the units were energized and indicated low-energy x-rays, the use of naturally occurring radioactive materials in the manufacture of cathode ray tubes has not been widely recognized. This paper presents the results of these surveys, the results of gamma spectroscopy, and a method for releasing existing computer equipment having naturally occurring radioactive materials.
Beta Particles↗
HIGH RESOLUTION CATHODE-RAY TUBES.
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Cathode Ray Tube↗
Colored focal visual evoked potentials by cathode ray tube versus scanning laser ophthalmoscope.
We compared the focal visual evoked potentials obtained in 52 young subjects with normal vision, evoked by means of three alternating black/color checkerboards generated by a trichromic cathode ray tube (dominant wavelength, 514 nm; colorimetric purity, 0.45) and by means of a scanning laser ophthalmoscope (argon laser beam, 514 nm; colorimetric purity, approximately 1). These three checkerboards, with an area of 3.5 degrees x 3.5 degrees (stimulating the fovea), then with an area of 3.5 degrees x 3.5 degrees with a central exclusion of 1.5 degrees x 1.5 degrees (stimulating the perifoveola) and finally with an area of 1.5 degrees x 1.5 degrees (stimulating the foveola) were presented within a field (8 degrees x 8 degrees) of homogeneous luminance of 170 cd/m2 and 1500 cd/m2, respectively. Their check sizes were 30', with a reversal temporal frequency of 0.75 Hz. The transient focal visual evoked potentials recorded with these three stimuli generated by the two types of stimulators were clearly detected for at least 85% of subjects. Their characteristics (waveform, amplitude and culmination times of the different waves) were comparable, regardless of the stimulator used (cathode ray tube or scanning laser ophthalmoscope). These results suggest that, under these various conditions of luminance and colorimetric purity, the neurophysiologic circuits tested function in identical ways. The focal visual evoked potential signs, now clearly defined by means of stimuli generated by cathode ray tubes, therefore apparently can be applied to the focal visual evoked potential evoked by stimuli generated by the scanning laser ophthalmoscope.
Adult↗
Recycling of scrap cathode ray tubes.
It is estimated that approximately 50% of the weight of a computer monitor is composed of cathode ray tube (CRT) glass. Thus, the successful recycling of scrap CRT glass can greatly relieve the disposal problem created by scrap monitors. CRT glass may be considered a hazardous waste due to its high lead concentration. A CRT can be divided into panel (front) glass and funnel (back) glass. Several coatings have been applied to the surface of the CRT panel and funnel glass. These coatings may present an adverse effectto the environment by obstructing the recycling and reuse of the CRT glass. To recycle CRT glass, a series of tests has been conducted to remove the coatings from scrap CRT glass. In this study, the CRT panel and funnel glass obtained from scrap computer monitors was cleaned by wet-scrubbing and ultrasonic cleaning methods. This cleaned CRT glass is intended to be recycled and reused by CRT manufacturers. This study shows that the wet-scrubbing method has a better coating removal performance and no associated pollution problem (i.e., no additional chemical additives). Thus, the wet-scrubbing method is recommended for use as a CRT coating removal method. The results of these tests are presented in this paper.
Beta Particles↗
Comparison of a cathode-ray-tube and film for display of computed radiographic images.
The goal of the study was to compare a cathode-ray-tube (CRT) digital display with film by using task-dependent image quality assessment methods. Contrast-detail analysis was utilized. Human observers performed a simple detection task, specifically, detecting a pillbox target in a uniform Poisson field, using either film or a digital display that employed a CRT monitor. Observers performed equally well on both film and CRT when the window settings of the digital display were established subjectively by a radiologist. Changing the window settings of the digital display to match the average background luminance of a film-illuminator combination decreased the luminance contrast of the targets and observer performance was reduced, though these effects were probably not linked. The "gold standard" film had lower luminance contrast than the CRT displayed images, yet observer performance was never lower for film than for the CRT. Therefore we concluded that luminance contrast was not a limiting factor for observer performance in this study. The CRT monitor changed fairly rapidly after it was calibrated. During a period of six months the gamma of the display increased from 1.82 to 2.42 and the maximum luminance decreased from 319 to 228 cd/m2. Low luminance output demonstrated a larger percentage decrease (approximately equal to 85%) than high luminance output (approximately equal to 29%) over the same time period. These observations suggest that standard window settings should be reviewed from time to time to ensure that the display is used optimally. No special look-up table setup such as perceptual linearization was used.
Calibration↗
Raster-scan cathode-ray tubes for vision research--limits of resolution in space, time and intensity, and some solutions.
Raster-based cathode-ray tubes (CRTs) are increasingly used for stimulus presentation. While very flexible, their design based on consumer electronics can limit their value in vision research. Here their limitations of resolution in time, space, intensity and wavelength are systematically compiled. Often, ingenious ideas can circumvent such limitations for specific experiments. Some ad-hoc solutions, as well as the more general techniques of dithering and anti-aliasing, are presented.
Artifacts↗
A multichannel cathode-ray tube unit for photographic recording.
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Beta Particles↗
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↗
A note on luminance calibration of raster-scan cathode-ray tubes: temporal resolution, ripple, and accuracy.
Accurate luminance calibration is an important issue for stimuli in vision research. Raster-scan cathode-ray tubes present a rapidly scanning spot with a luminance of the order of 10,000 cd m-2 (the actual value depends on video timing and phosphor persistence). With little spatial integration this may result in overloading of the front stage of a photometer. More importantly, even if averaged over hundreds of milliseconds, the pulsed nature of the luminance signal will markedly reduce accuracy of the luminance measurement. A frame-synchronised photometer is described to increase measurement accuracy whilst still rapidly acquiring the result.
Computer Terminals↗
Comparison of readability between liquid crystal displays and cathode-ray tubes.
Flat-panel displays, especially liquid crystal displays (LCDs), are almost universally used today. Do LCDs assure better readability than cathode-ray tubes (CRTs)? Two experiments were carried out to determine which type of display is better using a newly developed device. Four types of displays were tested; negative and positive CRTs, and LCDs with and without backlighting. Variables were the type of display, age, and gender. At first, analyses of readability using eye movements were conducted. Middle-aged subjects showed slower reading speed than young subjects. Then, experiments of pupillo-accommodative functions were carried out. Non-backlit LCDs reduced focusing speed among young subjects and reading performance in middle-aged subjects. Since middle-aged workers have more difficulties than young workers, they should have their vision properly corrected for VDT viewing, more appropriate displays and a more comfortable illuminance environment than young workers.
Adolescent↗
Reaction time to accelerating lines and dots on a cathode-ray tube.
Two experiments recorded the simple RT of 13 and 10 airline pilots, respectively, to accelerating lines and dots on a cathode-ray tube. In Exp. 1, dotted lines of six lengths moved in-line or frontally, and downward or to the right. Exp. 2 compared seven different in-line-moving solid lines with dot pairs of corresponding separations, and with single dots. RT increased with the length of in-line-moving solid lines but not when dotted lines were used. RT decreased with frontal movement of dotted lines. RT to dot pairs was shorter than to solid lines or single dots. Results indicate the importance of three factors: amount of movement information, visual angle, and inhibition of the retinal area stimulated.
Humans↗
Luminance artifacts of cathode-ray tube displays for vision research.
Phosphor persistence, video bandwidth, DC restoration and high-voltage regulation affect the appearance of images presented on cathode-ray tubes (CRTs), potentially resulting in differences between nominal and actual stimuli. We illustrate these effects by measuring physical parameters of horizontal and vertical static and counter-phase flickering gratings, and we illustrate problems for vision research by measuring contrast sensitivity to these gratings. We also measured the extent to which calibration protocols actually result in the monitor being calibrated over its entire area regardless of image size. The results of our physical measurements indicate substantial differences between gratings that nominally differ only as to orientation. Consistent with these differences, our psychophysical measurements indicate different sensitivities when the bars of the gratings are parallel or orthogonal to raster lines, regardless of the retinal orientation of the gratings. The results of our calibration check show that only a small region around the target area of calibration can be regarded as effectively linearized, and only if the size of the test image used during the check is similar to the size of the calibration patch. Overall, our results indicate potentially severe problems with the use of CRTs in vision research, and we discuss some published results that are likely to have been affected by these problems.
Artifacts↗
Active matrix liquid crystal displays for clinical imaging: comparison with cathode ray tube displays.
Fifteen large-area, flat-panel displays used for clinical image review were evaluated for image quality and compared with 30 comparably sized cathode ray tube (CRT) monitors. Measurements were of image display patterns by Video Electronic Standards Association (VESA) and a commercial product. Field measurements were made of: maximum and minimum luminance, ambient lighting, characteristic curve (gamma), point shape and size, high-contrast resolution, uniformity, and distortion. Assessments were made of pixel defects, latent image patterns, ghosting artifacts, and viewing angle luminance. Also, a questionnaire was generated for users of the flat-panel and CRT units. Seventeen respondents indicated no preference for either flat panel or CRT. Results show these flat panels to have higher luminance (mean, 177.7 cd/m2); larger number of just noticeable differences (JNDs; n = 555), higher gamma, comparable uniformity, and warm-up time. CRTs had less angle viewing dependence and far fewer artifacts (ghosting and latent images). Our questionnaire showed active matrix liquid crystal displays (AMLCD) to be fully acceptable for clinical image viewing. Furthermore, the statistical results show that further testing for new AMLCDs of this type is unwarranted.
Computer Terminals↗
Diagnostic usefulness of chest computed radiography--film versus cathode-ray tube images.
Seventy-one plain chest images obtained by computed radiography (CR) with an imaging plate were interpreted on film and two kinds of cathode-ray tube (CRT) monitors installed separately at two facilities (1,024 x 1,536 pixels, 8 bits, and 1,024 x 1,280 pixels, 10 bits) by 20 radiologists and four chest internists. The clinical categories of these 71 cases included pulmonary nodules and interstitial abnormalities. Image reading sessions were held over a total of 4 days, ie, 2 days and then another 2 days, 3 weeks later. Twenty-four observers formed four groups with six members each. Two groups read either films or CRT images at one of the two facilities. In the second experiment, 26 of 71 images were compressed at 10:1, 19 of 71 were compressed at 20:1, and 26 were not compressed. Analyses of the areas under the receiver-operating characteristic curves showed no significant differences in detection of pulmonary abnormalities between film and CRT. In detecting interstitial pulmonary abnormalities, film was more sensitive than CRT monitor. There were no significant differences in observers' performances between the two different kinds of CRT workstation. Subjective evaluation of image quality showed that images irreversibly compressed to the ratios of 10:1 and 20:1 were inferior to original images. Although further considerations are needed with regard to spatial resolution requirements, image processing, and image compression, the utilization of CR CRT image as a substitute for CR film image will be possible.
Data Display↗
Do liquid crystal displays assure better readability than cathode-ray tubes?
Flat-panel displays, especially liquid crystal displays (LCDs), are now firmly established as important devices for information displays. But do LCDs assure better readability than cathode-ray tubes (CRTs)? We carried out an experiment using four types of displays: negative and positive CRTs, and LCDs with and without backlighting. A syllable-checking task using the Japanese katakana alphabet was conducted among fifteen healthy workers. They were divided into three groups; Group 1 had five young males aged 25 to 29, Group 2 was made up of five young females aged 18 to 24, and Group 3 consisted of five middle-aged workers who were 40 to 50 years old. We used four ambient light levels: 200 lx, 500 lx, 1250 lx without reflected glare, and 500 lx with reflected glare, on the display screens from behind. The illuminance of the glare was approximately 200 cd/m2. Multiple regression analysis showed that non-backlit LCDs reduced reading performance in middle-aged subjects significantly. Since middle-aged workers have more difficulties than young workers, they need more appropriate displays and a more comfortable illuminance environment than younger workers.
Adolescent↗