High-resolution Cathode Ray Tube Research Articles

Estimating the critical duration for temporal summation of standard achromatic perimetric stimuli.

To estimate the critical duration of temporal summation for achromatic Goldmann III stimuli under the conditions of standard automated perimetry (SAP) and quantify response variability for short-duration stimuli. Contrast thresholds were gathered using the method of constant stimuli for seven circular (0.48° diameter) incremental stimuli of varying duration (sum-of-frames equivalent: 8.3-198.3 ms), at an eccentricity of 8.8° along the four principal meridians of the visual field in two healthy, psychophysically experienced observers. Stimuli were presented on a high-resolution cathode ray tube display with a background luminance of 10 cd/m(2). Psychometric functions were fitted using a probit model and nonparametric local-linear analysis. The critical duration was estimated using iterative two-phase regression analysis, the results also being compared with values produced using previously published methods of analysis. The median critical duration estimated using iterative two-phase regression analysis was 27.7 ms (IQR 22.5-29.8). A slight steepening of the psychometric function slope (lower variability) was observed for longer stimulus durations, using both probit and local-linear analysis techniques, but this was not statistically significant. Critical duration estimates in this study are substantially shorter than those previously reported for a Goldmann III stimulus, under the conditions of SAP. Further work is required to firmly establish the relationship between measurement variability and the degree of local temporal and spatial summation.

LCD and CRT display of storage phosphor plate and limited cone beam computed tomography images for the evaluation of root canal fillings

The aim was to compare quality of liquid crystal display (LCD) and high resolution cathode ray tube (CRT) screens for the evaluation of length and homogeneity of root canal fillings in storage phosphor plate (SPP) and limited cone beam computed tomography (LCBCT) images. Endodontic treatment was performed to 17 extracted permanent lower incisor teeth. Images of each tooth positioned in a dried mandible were obtained with Digora SPP and Accu-I-Tomo LCBCT systems. Six observers scored the quality of all images on CRT and LCD screens. Results were compared using McNemar's and Cochran's Q tests (p < 0.05). The differences among the LCBCT and SPP images were determined by binomial test. No significant difference was found between ratings of CRT and LCD displays (p > 0.05). Agreement among observers' scores was higher with CRT display. Within the limits of this ex vivo study, differences between LCD and CRT monitors for the evaluation of root canal fillings are clinically insignificant independent on whether conventional radiographs, captured by means of image plates, or cone beam images are being displayed.

Influence of liquid crystal display monitors on observer performance for detection of diffuse pulmonary disease on chest radiographs

The purpose of this study was to assess the influence of liquid crystal display (LCD) monitors on the detectability of diffuse pulmonary diseases depicted on chest radiographs by comparing them with a high-resolution cathode ray tube (CRT) monitor. A group of 17 radiologists interpreted 87 soft-copy images on LCD monitors with pixel arrays of 1024 x 1280, 1200 x 1600, 1536 x 2048, and 2048 x 2560 and on a CRT monitor with a pixel array of 2048 x 2560. They were asked to indicate their individual confidence levels regarding the presence of diffuse pulmonary diseases. The luminance distributions of all monitors were adjusted to the same distributions, and the ambient illumination was 200 lux. Observer performance was analyzed in terms of the receiver operating characteristics (ROC). The average ROC curves for the five monitor types were similar, and there were no statistically reliable effects of the five monitor types on the readers' diagnostic performances (P = 0.7587). The detectability of diffuse pulmonary disease on the LCD monitors with a spatial resolution equal to or higher than a matrix size of 1024 x 1280 was found to be equivalent to that on the high-resolution CRT monitor.

The influence of liquid crystal display (LCD) monitors on observer performance for the detection of nodular lesions on chest radiographs

To access the influence of liquid crystal display (LCD) monitors on the detectability of nodular lesions depicted on chest radiographs by comparing them with a high-resolution cathode ray tube (CRT) monitor. Ten radiologists interpreted 247 soft-copy images on LCD monitors with pixel arrays of 1,024x1,280, 1,200x1,600, 1,536x2,048 and 2,048x2,560, and a CRT monitor with a pixel array of 2,048x2,560, and were asked to indicate their individual confidence levels regarding the presence of a nodule. These images were chest radiographs with and without a lung nodule from the "Standard Digital Image Database" created by the Japanese Society of Radiological Technology. The luminance distributions of all monitors were adjusted to the same, and the ambient illumination was 200 lux. Observer performance was analyzed in terms of the receiver-operating characteristics. No significant statistical differences in nodule detection performance were found among the four LCD monitors and the CRT monitor. The nodule detection performance on the LCD monitors with a spatial resolution higher than a matrix size of 1,024x1,280 was found to be equivalent to that on the high-resolution CRT monitor.

13.3: MTF and NPS Study of High-Resolution LCDs and CRTs for Mammography

This paper presents a closer look on the link between the physical parameters (MTF and NPS) that characterize the performance of a liquid crystal display (LCD) and the architecture that generates the images. Understanding the major architectural difference between the cathode ray tube (CRT) and LCD displays can lead to better image quality analysis and characterization of the LCD displays. The aim of this research is to quantify two major image quality control parameters namely, modulation transfer function (MTF) and noise power spectrum (NPS) and understand their significance with respect to the architecture of the LCD and CRT displays. The experimentation was performed at Fischer Imaging Corporation research and development division in Denver, CO. We conclude the following: (1) The MTF of LCD is higher than that of CRT, and (2) LCD has higher NPS. The results thus infer that the LCD is better suitable display compared to CRT displays for mammography applications particularly considering its superior resolution.

Detectability of Catheters on Bedside Chest Radiographs: Comparison between Liquid Crystal Display and High-Resolution Cathode-Ray Tube Monitors

To compare observer performance with a flat-panel liquid crystal display (LCD) monitor and with a high-resolution gray-scale cathode-ray tube (CRT) monitor in the detection of simulated support catheters on bedside chest radiographs. The ethics committee did not require approval or patient informed consent when this study began. Because of a change in regulations, before images were acquired the nature of the study and procedures were explained to patients or their relatives, and consent was then obtained. A total of 131 catheter fragments (12-14 per radiograph) were superimposed over 10 anteroposterior bedside chest radiographs obtained with storage phosphor technology. Images were displayed on an LCD monitor (1536 x 2048 matrix) and a CRT monitor (2048 x 2560 matrix). Five radiologists independently located the catheter fragments and rated their confidence in detection with bright and subdued ambient light. A two-way analysis of variance and the Friedman test were used for statistical analysis. There was no significant difference for either display type with respect to correctly detected catheter fragments (mean sensitivity, 56.6% and 56.0% for the CRT and the LCD monitors, respectively, with bright light and 61.2% for both monitors with subdued light). With both display types, detection rate with bright light decreased significantly (P < .05). False-positive rates and confidence ratings were not significantly affected by monitor type or ambient light. In a study with simulation of clinical conditions, performance of the LCD monitor and high-resolution CRT monitor for detection of support catheters on bedside chest radiographs was equivalent. With both displays, detection performance was equally reduced with bright ambient light.

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

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. 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. 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. 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.

Diagnostic performance of liquid crystal and cathode-ray-tube monitors in brain computed tomography

The aim of this study was to evaluate feasibility of reporting brain CT examinations on liquid crystal display (LCD) flat-screen monitors vs state-of-the-art cathode-ray-tube (CRT) monitors. Ninety-five brain CT examinations of 95 patients were displayed on Picture archiving and communications system (PACS) workstations equipped either with a dedicated medical imaging LCD colour monitor or on a high-resolution CRT which is used for routine reporting of CT, MRI and digital radiography images in our institution. Fifty cases were negative and 45 cases were positive for early brain infarction (EBI), the latter being defined by a combination of one or more signs: dense artery; hypodensity of brain parenchyma; and local brain swelling verified by control scans. Ten radiologists had to rate presence or absence of EBI on a five-point scale. Ratings were evaluated by CORROC2 ROC software and areas under the ROC curve (A(z)) were computed. Significance of differences between the two viewing conditions were evaluated with Wilcoxon test. Mean A(z) of the ten observers was 0.7901 with LCD vs 0.7695 with CRT which did not show statistical significance (p=0.2030). In the setting investigated, reporting of CT studies from high-performance LCD monitors seems feasible without significant detriment to diagnostic performance.

Laboratory Test System for Performance Evaluation of Advanced Star Sensors

Latest-generation star sensors are characterized by innovative features that need additional testing capability in comparison to previous star trackers; therefore, novel indoor test facilities are required in some cases to assess theirperformance. Thispaperreportson design, realization, and operation of such a laboratory system. Itisbased on simulation of stare eld scenesto be acquired by thesensor undertest. Thescenes aregenerated on a 21-in. highresolution cathode ray tube display by means of a simulation software running on a personal computer. Selected components are commercial, off-the-shelf products, hence offering low-cost and short-time development. Results of a study conducted to identify performance of an advanced star sensor are reported in detail. A satisfactory accuracy, 35 arcsec, is achieved for pitch and yaw pointing angles. Adequate results have been attained also for the corresponding rates: 230 arcsec/s during slow rotations and 10% of the maximum angular rate during fast ones. These values are adequate for most spacecraft operating conditions. Larger uncertainties are attained for roll rotations: in the range of 70 ‐420 arcsec for angle and of 1000 ‐1750 arcsec/s for angular rate measurements. Consequently, roll values are acceptable only for fast rotations and medium- or low-accuracy operations.

Video moire cancellation filter for high-resolution CRTs

The appearance of moire limits the performance of high-resolution cathode ray tubes (CRTs). Until now, cancellation circuits have used a small alternating image shift (wobble) to disguise moire, but these circuits introduce other artefacts like flicker. We present a novel solution for suppressing video moire with a specific non-linear filter. Advantages include simple digital video signal processing and negligible degradation of the image quality, even in graphics with very fine detail.

Detection of caries with conventional digital imaging and tuned aperture computed tomography using CRT monitor and laptop displays

Objective. The purpose of this study was to compare the diagnostic performance of conventional digital images and tuned aperture computed tomography (TACT) slices in caries detection through use of cathode-ray tube monitor and laptop displays. Study design. Forty-two extracted posterior teeth were mounted and imaged with a direct digital radiography system. Conventional digital bitewing projections and TACT slices were acquired. Images were viewed on a high-resolution cathode-ray tube monitor and on an active-matrix laptop display. Eight observers assessed caries status of occlusal and proximal surfaces of the teeth using all combinations of image and display modality. Observers’ assessments were compared with the results of histologic examination of tooth sections. Possible differences in receiver operating characteristic curve areas among displays, image modalities, observers, and surfaces were analyzed by means of analysis of variance. Results. There was no statistically significant difference between the diagnostic performances provided by the cathode-ray tube monitor and laptop displays in caries detection ( P = .588). In addition, the performances of digital images and TACT slices were not significantly different ( P = .843). Conclusions. Modern active-matrix laptop displays provide diagnostic quality for caries detection comparable to that obtainable with cathode-ray tube monitors. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1999;88:234-8)

Influence of film and monitor display luminance on observer performance and visual search

The purpose of this study was to measure the influence of display luminance on detection performance and visual search behavior. The results of the study should be helpful in establishing minimally acceptable display conditions for viewing radiographs on cathode-ray tube (CRT) monitors. Two groups of six radiologists each viewed 50 pairs of mammograms. One group viewed film images on a standard mammographic view box; the other viewed images on a high-resolution CRT monitor. Two luminance levels were studied for each display type. Observers reported on the presence or absence of masses or microcalcification clusters and on their confidence in that decision. Confidence data were analyzed by using alternative free-response receiver operating characteristic (AFROC) techniques. Eye position also was recorded as observers viewed the images. For both the film and monitor studies, detection performance (AFROC area under the curve) was not affected significantly by display luminance, but search behavior was. Total viewing and decision dwell times were shorter with the higher-luminance displays, especially for true-negative decisions. Significantly more fixation clusters were generated during the search of lesion-free than of lesion-containing images with the lower-luminance displays. Display luminance affects visual search performance with both film and monitor displays without affecting detection performance significantly. Higher-luminance displays yield more efficient search performance. The true-negative dwell times and number of clusters are suggestive that lower-luminance levels prolong the search and recognition of normal, lesion-free areas compared with lesion-containing areas.

Behind Gamma's Disguise

A simple power law is often used to describe the light output of cathode ray tubes (CRTs). Its exponent gamma (γ) has been measured many times in many ways, with varying results. The failure of this simple formula to accurately characterize high-resolution CRTs used in film recording applications has led to a model that explains the observed light output from very low beam currents to high drive levels. It comprises a cathode model and an anode current “trim” function; the relationship between anode and cathode currents establishes the key parameters. The cathode current is represented by a blend of two power laws. The anode current is a fraction of the cathode current, determined by the intersection of a gaussian beam with a circular aperture. The resulting model successfully predicts the behavior of high-resolution CRTs, even at low output levels. It also explains the many varying results when attempting to measure a single value for gamma.

High-resolution computer display of portable, digital, chest radiographs of adults: suitability for primary interpretation.

The suitability of using a high-resolution computer-display system for primary interpretation of adult chest radiographs obtained with portable apparatus and storage phosphor technology was evaluated with receiver operating characteristic analysis and subjective methods. Sixty portable digital chest radiographs showing abnormalities that approached the resolution limits of our computed radiography system were selected. The original digital data making up the 2140 x 1760 x 10 bit images were transferred to a cathode ray tube (CRT) display system composed of two Megascan monitors. Postprocessing rendered two images, one for each monitor, to emulate the two-on-one hard-copy format produced by the computed radiography system. Each image set was interpreted independently by three radiologists experienced with hard-copy format. Limited level and window adjustments were allowed during CRT interpretation. For both CRT and hard-copy display, images were graded on the basis of the interpreter's confidence in the presence of pneumothorax and parenchymal abnormalities. Three types of foreign devices were subjectively analyzed: endotracheal tubes, nasogastric tubes, and temporary epicardial pacer wires. No significant differences were found in detecting pneumothorax or focal infiltrates. One radiologist found the hard copy better for detecting diffuse infiltrates (p = .02); two radiologists favored CRT for visualizing nasogastric tubes (p < .005, p < .02); and one radiologist favored CRT for visualizing temporary epicardial pacer wires (p = .05). We conclude that an optimized high-resolution CRT system is quite promising for primary interpretation of digital portable chest radiographs, but further investigation and greater statistical power are necessary to confirm our results.

Performance of high‐resolution monitors for digital chest imaging

High-resolution cathode-ray tubes (CRT's) are currently the most viable soft-copy display for digital radiography. We present here methods for measuring large-area contrast ratio and detail contrast ratio. A two-dimensional charge coupled device (ccd) array signal-averaged with a video frame buffer permits linear microradiometric measure of individual beam lines. Results from three different 1000-line monitors demonstrate the shift variance of resolution. The detail contrast ratio (or modulation depth) was found to vary from 100% to less than 10% across the face of one CRT. Dynamic focus in both the horizontal and vertical deflection circuitry proved effective in reducing this shift variance. Comparisons of three phosphors demonstrate the utility of long persistence phosphors (P164) for static display in producing brighter images with less flicker. Recommendations for CRT design and selection for high-resolution digital radiography are included.

Three-dimensional Imaging of Bone from Computerized Tomography

An automatic computer technique was designed to produce three-dimensional (3D) images of bony anatomy on a cathode ray tube (CRT) from computerized tomography (CT) data. The authors transferred CT scan data of a cadaver and 11 patients to a computer system via magnetic tape. An automatic edge extraction algorithm generated an outline of bone specified by a range of CT numbers for each scan slice. These outlines were stacked in the computer and various graphics options used to represent the 3D anatomy of bone on a high-resolution CRT screen. The 3D image data were interfaced with a three-axis computer numerically controlled milling device to produce solid models of these bone images. Comparison of the dimensions of the solid models of the femur, hemipelvis, and femoral medullary canal to the actual cadaver specimen demonstrated that the models were accurate in size to within 1-3 mm. These 3D images and solid models will be helpful for preoperative diagnosis, surgical planning, and customized prosthesis manufacture in complex orthopaedic cases.

A high luminance high-resolution cathode-ray tube for special purposes

For those applications where light sources of high radiance or displays of high resolution are necessary, miniature cathode-ray tubes have been developed with monocrystalline luminescent screens. These newly developed screens consist of cerium-doped yttrium-aluminum garnet (YAG), epitaxially grown on commercially available YAG substrates; they have an excellent heat conductivity and are optically clear. The construction of the tube and its performance in two modes of operation are described. When the tube is operated with a continuous undeflected beam, the luminance of the spot is limited by thermal quenching of the phosphor material. Under these circumstances, the maximum luminance of 1.9 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8</sup> cd/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> (0.55 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8</sup> FTL or 4 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> W/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> sr) is reached at a power of 70 mW in a 3.5-µA 20-kV beam, focussed to a spot of 9 µm diameter. Equipped with appropriate deflection coils and scanned with an interlaced field of 575 active lines and 25-Hz repetition frequency, the tube can handle up to 20 W of beam power in a 12 × 16 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> image area. In this mode, the luminance is limited by the design of the electron gun and the desired resolution. At 20 kV and 100 µA (i.e., at 7500 cd/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) the tube has a half-intensity linewidth of 60 µm, which is equivalent to 500-TV limiting response lines in the same 12 × 16 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> area.

A new automatic flat-bed microdensitometer for use in x-ray crystallography.

A computer-controlled microdensitometer has been designed and built mainly for use in X-ray crystallography. The instrument is a hybrid of two earlier microdensitometers and combines accurate positioning with fast measurement. It incorporates a stage mechanically driven by stepping motors. The source of light is a high-resolution cathode ray tube which is imaged on to the film plane, the optical densities being measured by photomultipliers. The instrument is used routinely to scan oscillation photographs of biological macromolecules.

High-efficiency cathode-ray tubes for dry-process recording

Typically, dry-process-recording media is sensitive only in the ultraviolet (UV) region of the spectrum, where current phosphors and faceplate glasses are either inadequate or unavailable. Thus, it was considered necessary to develop new phosphors and fiber-optic faceplates for incorporation in high-resolution cathode-ray tubes (CRTs) to be used for these dry-process real-time-recording applications. Two rugged UV phosphors, which emit radiation centered near 320 nm and 380 nm, are joined with newly developed fiber-optic faceplates to produce CRTs that may be used to write on almost any of the mentioned recording media. Up to tenfold improvement in writing speed on appropriate media is shown to be possible.

Electronic halftones

To derive the greatest advantage from automation in the production of newspapers and books the present optical method of producing halftone dot patterns must be replaced by an electronic method. This article discusses developmental electronic-halftone techniques that use a high-resolution cathode-ray tube as the display device.