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PubMed2004

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↗
PubMed1990

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↗
PubMed1993

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↗
PubMed1989

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↗
PubMed2005

Cathode-ray-tube monitor artefacts in neurophysiology.

We demonstrate that cathode-ray-tube (CRT) monitors commonly used as stimulus generators in visual neuroscience produce signal artefacts. This arises from two factors, one being the finite time needed for the raster scan of the CRT to cross the receptive field being stimulated, and the other being the restraint imposed by the impulse response of the phosphor itself. Together these factors result in smearing or blurring that manifests as high frequency noise, distorting the desired signal applied by the investigator. Our analysis identifies those conditions that promote these artefacts and we describe methods for their minimisation. We suggest that a monitor frame rate >/=100 Hz provides a reasonable trade-off between refresh and the generators of high frequency noise.

Artifacts↗
PubMed2002

The effect of pixel nonlinearity on cathode-ray tube-based visual acuity tests.

BACKGROUND: Pixel nonlinearity of a cathode-ray tube (CRT) display can cause differences between the actual image and the nominal image. One of the discrepancies, the anisotropy of interactions between neighboring pixels on the same raster line and between neighboring raster lines, may have an impact on the CRT-based visual acuity test where small horizontal and vertical gaps are used. We evaluated this impact. METHOD: Two high-quality color CRT monitors were tested. The stimulus target was a black square ring on a white background. White gaps of one stroke width were opened in the middle of the straight sides of the square ring. In a gap width comparison study, the up and down gaps were flanked with a one-pixel band on the left and right side. The pixel value of the bands was varied to determine the luminance that made up and down gaps appear to have the same width as left and right gaps. The comparison was made at 1 and 2 m. In a visual acuity study, horizontal gap (left/right) acuity and vertical gap (up/down) acuity were measured separately at several distances between 8 and 11 m. Similar measurements were made when the monitor was rotated 90 degrees. RESULTS: Gaps with edges that were parallel to raster lines (raster-parallel gaps) appeared wider than gaps with edges that were perpendicular to raster lines (raster-perpendicular gaps). To match the apparent width of the left and right gaps, the two one-pixel bands flanking the up and down gaps required a pixel value that corresponded approximately to a luminance of mid gray, indicating that the apparent width of a four-pixel left or right gap was similar to that of a five-pixel up or down gap. Raster-parallel gaps produced a higher percentage of correct responses than raster-perpendicular gaps in a visual acuity test. When nominal gap widths were equal, left and right gaps produced 10% or more correct responses than up and down gaps at some target sizes, which translated to a two-letter acuity difference. This acuity difference could not be accounted for by uncorrected astigmatism because the anisotropy persisted when the monitor was turned 90 degrees. CONCLUSIONS: Pixel nonlinearity of a CRT-display results in an anisotropy of gap width that can be observed at and above visual acuity size. This anisotropy may introduce uncertainties in the results of CRT-based visual acuity tests where gaps of different orientations are used.

Anisotropy↗
PubMed2002

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↗
PubMed1998

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↗
PubMed1997

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↗
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↗
PubMed2004

Comparison of liquid crystal versus cathode ray tube display for the detection of simulated chest lesions.

The purpose of the study was to compare the detection performance of a cathode ray tube (CRT) monitor versus a liquid crystal display (LCD) monitor for simulated subtle pulmonary lesions. Ten templates containing simulated lung lesions were superimposed on an anthropomorphic chest phantom. Posteroanterior radiographs were obtained using flat panel technology and were displayed on a CRT and an LCD monitor. Image processing and reading conditions were equivalent for both softcopy displays. Five observers assessed lesion detectability using receiver-operating characteristic (ROC) methodology. A multivariate test (Pillai trace) was used to test the significance of differences (P<0.05). The multivariate test revealed significantly different detection rates for the lesion types, but no significant difference between the two display modes. Detection performance for both monitors was higher for nodules and micro-nodules and lower for lines and patchy opacities. Analysis of lesion subgroups according to their location in lucent/obscured lung areas was also not statistically significant. Under ideal reading conditions, CRT and LCD displays perform equivalently for the detection of simulated subtle pulmonary lesions.

Data Display↗