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An electronic apparatus was developed which measures the effective current flow of the monophasic stimulation pulses while the tip of the electrode is passing through the tissue. This current flow can be observed as a function of time on the screen of a cathode ray tube.
The effect of prolonged cathode ray tube (CRT) work on the afferent visual neural and focusing system of the human eye was examined by visually evoked potentials (VEPs) and laser optometer techniques, respectively. These measures were compared with parallel measurements of search performance. Ten volunteers performed three 4-hr sessions of a search/decision task on a high-resolution-red/green/blue (RGB) monitor. Stimuli were numbers and symbols presented in a blue/black, red/black, or red/green foreground/background combination. Results showed minimal changes in the neural and focusing responses to each foreground/background combination over time on task. Weak correlations were found between neural-optical and search performance measurements. These data suggest that the use of chromatic stimuli in the color combinations examined do not have a detrimental effect on visual performance.
Liquid crystal displays maintain superior contrast under bright sunlight conditions compared with cathode-ray tube displays. This attribute, along with reduced weight, volume, and power requirements, make liquid crystal displays especially desirable for use in vehicular applications. The present experiment was designed to determine the luminance requirements for transmissive liquid crystal displays viewed under a wide range of lighting conditions typical of many vehicular environments. Both the ambient illumination incident on the display surface and the forward-field-of-view adaptation luminance were parametrically manipulated. The visual task involved speeded spatial discrimination responses for detection of the gap in a modified Landolt-C acuity target. The results indicate that under the worst lighting conditions tested, a display luminance of approximately 180 cd/m2 yielded asymptotic spatial discrimination performance. The results have been incorporated into a predictive visual performance model for spatial discrimination tasks, which describes the present data well and represents a first step toward a device-independent model of display visibility.
Liquid crystal displays (LCDs) are gradually replacing cathode-ray tubes (CRTs) as the primary means of electronic display of digital radiographs. The transition from CRT to LCD is fueled by advantages of the LCD technology such as enhanced maximum luminance and smaller form factor. This transition is expected to extend to digital mammography as well. The purpose of this study was to report the on-axis luminance and contrast performance of five medical-grade LCDs in terms of compliance with the DICOM grayscale display function (GSDF) and AAPM TG18 guidelines. The display devices included two 3 Mpx monochrome LCDs (Planar Dome C3, and NDS 20.8" Nova), two 5 Mpx monochrome LCDs (NDS 21.3" Nova, and Totoku ME511L), and one 9 Mpx color LCD (IBM T221). The on-axis luminance values were measured at all 8-bit driving levels using the TG18-LN test patterns and a baffled luminance meter and the results averaged. The luminance data were analyzed according to the AAPM TG18 methodology. The measured L(min), L(max), mean DeltaJND/Deltap, and maximum local deviation in DeltaJND/Deltap from GSDF, kappa(256), ranged within 0.43-0.87 cd/m(2), 263-715 cd/m(2), 2.15-2.72, and 0.79-1.46 intervals, respectively. While the values varied notably between different devices, all devices conformed to the TG18 criteria for primary class displays in terms of on-axis luminance response, and thus judged suitable for mammographic applications from on-axis luminance standpoint. Notwithstanding the findings, other factors such as matrix size, angular response, and color functionality should further be taken into consideration.
A feasibility study has indicated that a Prescion Encoding and Pattern Recognition (PEPR) cathode ray tube prescreening system for cervical smears can be both accurate and fast. Smears are prepared using a syringing technique and are stained with a Feulgen-type nuclear stain and a protein counter-stain. The use of film as an intermediate step between the cells and Bio PEPR allows the scanning of fields as large as 8 x 8 mm. The morphological features of the cells are measured as directed by a hierarchical decision strategy. Additional programs detect artifacts, overlaps, and leukocytes. For clean samples, false positive and false negative rates on the cell level have been obtained that will allow acceptable smear level rates (10% false positive, 1% false negative). These rates have been reached without compromising the required speed goals of 120 to 180 smears per hr. The efficiency of the system is dependent on the quality of the smears. Measurements on a set of 192 routinely prepared smears indicate acceptable false negative rates and a false positive rate of about 18%. A reduction of this rate is expected with small improvements in cell preparation and measuring software, leading to the overall system efficiency required for commercial feasibility.
A computer program has been developed to assist the physician in managing patients with hypercalcemia. The program requests appropriate information, such as the patient's serum calcium concentration, age and x-ray results. Based on the abnormalities detected, the program asks additional questions needed to suggest the most helpful course of action for evaluating or treating the patient's hypercalcemia. As soon as the data have been entered, the program generates an evaluation note that includes diagnostic possibilities, suggestions for additional laboratory studies, therapeutic recommendations and references to the medical literature. The program can be used from any general purpose teletype-compatible terminal (including cathode ray tube displays) connected to the Bell Telephone System. The time required to enter the data and obtain the evaluation note is approximately 4 minutes with a teletypewriter, and less if a faster terminal is used. The cost for computer time is comparable to that of a laboratory test. Comparison of diagnoses produced by the program with those obtained from pathologic examination of from consulting endocrinolgists shows that the program is sufficiently accurate for clinical use. Finnally, the explanation of the pathophysiology contained in the evaluation note may be useful to the student.
OBJECTIVE: Televised images are the most common stimulus for provoking photosensitive seizures in photosensitive persons. To inhibit photosensitive seizures in photosensitive persons who do or do not have epilepsy, the authors sought nonpharmacologic methods for reducing the levels of photic stimulation of televised images. BACKGROUND: The authors found two types of pathophysiologic mechanisms (wavelength-dependent and quantity of light-dependent mechanisms) for photoparoxysmal responses (PPR). METHODS: The authors tested two different types of optical filters, one reflecting long-wavelength red light selectively, which stimulates a wavelength-dependent mechanism, and the other absorbing light in the visible spectrum evenly (neutral density filters). Inhibiting effects of optical filters were studied by conventional intermittent photic stimulation (IPS) using strobe light and novel photic stimulation using flashing cathode ray tubes (CRT). RESULTS: Both filters individually inhibited PPR insufficiently (less than 50%). Compound optical filters, composed of both types of filters, can inhibit the PPR, approximately 90% for IPS and 95% for photic stimulation with CRT. These compound optical filters do not destroy chromaticity of emissions from the television's CRT. CONCLUSIONS: These compound filters may be useful to prevent seizures induced by television in photosensitive persons.
Thresholds for diffuse, broad-band illumination were obtained for the goldfish (Carassius auratus) by avoidance conditioning. The light source was a television cathode-ray tube whose output was controlled over a range of 140 dB by a combination of 'brightness' control, blanking of scan lines, and neutral density filters. The threshold was calculated in terms of irradiance to be 2-9 X 10(-6) muW cm-2 (+/- a standard deviation of 1-4). The determination of absolute, rather than relative, values, and the use of overhead, diffuse illumination provided data that would be ecologically and behaviourally relevant.
For monitoring the changes in intracellular free Ca2+ concentration ([Ca2+]i), we developed a simple system combining a fluorescence microscope, an image intensifier, a video-camera, a cathode ray tube display and a photodiode, employing quin2 as a Ca2+ indicator. We recorded increases of the fluorescence intensity due to [Ca2+]i rises, when high K+ medium, neurotransmitter and Ca2+ ionophore were applied to the single cells of nervous system origin in culture. The present system is capable of simultaneous detection of the [Ca2+]i changes from multiple separate cells.
Chest radiographs from 50 patients, including 25 with lung cancer, were digitized at a resolution of 100 dots/inch (40 dots/cm) and saved in JPEG format at a low compression ratio. The average size of the stored images was 55 kByte (range 6-86 kByte). Four respiratory specialists observed these images on the cathode ray tube (CRT) display of a PC-based teleconferencing system with a resolution of 800 x 600 pixels. One month later they observed the original chest radiographs. A receiver operating characteristic (ROC) analysis was performed on their diagnoses, based on a five-point confidence scale about the presence of lung cancer. The observer-specific Az values for the teleconferencing system ranged from 0.801 to 0.944, and the corresponding Az values for the conventional radiographs from 0.926 to 0.957. No significant differences were found between the teleconferencing images and the original images, which suggests that a PC-based teleconferencing system could be useful in the diagnosis of lung cancer on chest radiographs.
OBJECTIVES: To evaluate the validity of approximal caries detection on digital bitewing radiographs displayed at different image sizes on either a cathode ray tube (CRT) monitor or a thin film transistor (TFT) monitor. METHODS: Five observers assessed digital radiographs of a charge-coupled device (CCD)-based sensor system (Sidexis) of 160 unrestored premolars and molars for approximal caries using a six category caries rating scale. Images were displayed at ratios of 1:1, 1:2 and 1:7 on a CRT monitor (Nokia 446 XS) and a TFT display (Panasonic LC 50S). Histological assessments of serial sections were used as the validation standard. Diagnostic accuracy was expressed as area under the receiver operating characteristic (ROC) curve (AUC) and was calculated at two levels of caries penetration: presence of caries (I) and presence of a lesion in the dentine (II). The influence of the factors "monitor type", "image size" and "validation threshold" were analysed with repeated measures analysis of variance. RESULTS: The ROC curve areas for approximal caries detection at both histological penetration levels were not influenced by the type of monitor display, whereas image size had a significant impact (P<0.01). AUCs for image size 1:7 (I, 0.62; II, 0.65) were smaller compared with ratios of 1:1 and 1:2 (P<0.01). No differences were observed between image size ratios 1:1 (I, 0.69; II, 0.74) and 1:2 (I, 0.68; II, 0.73). CONCLUSIONS: In this study, the type of monitor did not influence approximal caries detection on digital radiographs. Image sizes with a display ratio of 1:1 and 1:2 resulted in better diagnostic validity than those with a ratio of 1:7.
Prior reports of CT-guided lung biopsy of the small lung nodules of less than 2 cm have been unsatisfactory. In January 1998, we began a preliminary study of CT-guided lung biopsy in our conventional CT room. With the basic results achieved, we constructed a novel CT-guided lung biopsy system. Together with Hitachi Corporation we have developed CT, the Radix Prima, exclusive for interventional procedures especially for CT-guided lung biopsy. As reconstruction delay time of the procedures has been shortened from 1.0 sec. to 0.6 sec., real time CT fluoroscopy monitoring is possible on the Cathode Ray Tube (CRT) monitor in the CT room, very closed to the patient. Multiple confirmations of the tip of the biopsy needle have been possible with this specially equipped CT. A semi-automatic-type needle have been selected for reliable biopsy, because the old fully-automatic-type needle was very heavy and easily misfired. Multiple punctures have been also used, because single punctures have a greater risk of obtaining inadequate specimens. In our clinical study at our IVR center, the subjects comprised 41 patients (26 males, 15 females, ranging in age from 34 to 79, mean 64 years old). The mean nodule diameter was 1.9 cm, the mean distance from skin surface to lesion was 5.5 cm, and the mean number of punctures was 3.0. The biopsy results included 23 malignancies. In 13 patients the results were benign tumors or specific inflammation. In 4 patients the results were nonspecific inflammation. In only 1 patient was the specimen inadequate. There was no false negative. The correct rate of benign/malignant diagnoses was 98%. A complication of pneumothorax was observed in 22 patients, but all were improved by conservative treatment. Pulmonary hemorrhage was observed in 21 patients, 7 of whom also had hemoptysis. Each of these patients also responded to conservative treatment from specialist medical staff at the IVR center. The 98%accuracy of our results indicates that multiple punctures using a semi-automatic-type biopsy needle and multiple confirmations of the needle tip on our method of real time CT fluoroscopy are extremely important for CT-guided lung biopsy of small lung nodules of less than 2 cm.
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The spatiochromatic receptive-field structure of neurons in the macaque visual system has been studied almost exclusively with stimuli based on the human foveal cone fundamentals of Smith and Pokorny [Vision Res. 15, 161 (1975)] and generated on cathode ray tube displays. In the current study the artifacts evoked by cone-isolating, spatially structured stimuli due to variations in the eye's preretinal absorption characteristics and axial chromatic aberration are quantified. In addition, the luminance artifacts evoked by nominally isoluminant sinusoidal grating stimuli due to the same factors are quantified. The results indicate that the spatiochromatic stimuli commonly employed to map receptive fields of neurons at eccentricities > 10 deg are especially prone to artifacts and that these artifacts are maximal for the high-contrast S-cone-isolating stimuli that are often used. On the basis of these simulations, a method is introduced that improves spatiochromatic receptive-field estimates by compensating for response contributions from the incompletely silenced cone mosaics during cone-isolating stimulation.
We consider the reproduction of color subject to material and neighborhood constraints. By "material constraints," we mean any constraints that are applied to the amount of ink, lights, voltages, and currents that are used in the generation of color. In the first instance we consider the problem of reproducing a target color constrained by maximum additive color signals, such as in the phosphorescence process in a cathode ray tube. In the second instance we consider the more difficult problem of reproducing color subject to constraints on the maximum primary color variations in a (spatial) neighborhood. We introduce the idea of adjacent color variance (ACV) and then attempt to reproduce colors subject to an upper bound on the ACV. An algorithm that is suitable for this task is the method of vector space projections (VSP). In order to use VSP for constrained color reproduction, we use a novel approach to linearize nonlinear CIE-Lab space constraints. Experimental results are furnished that demonstrate that using the ACV as a bound helps to reduce reproduction artifacts in a color image.
Heterochromatic brightness matches with checkerboard patterns made up of a white reference and a chromatic test element for various element sizes from 3' to 2 degrees 30' square and with a 5 degrees bipartite field were carried out with a color cathode-ray tube. The brightness-to-luminance (B/L) ratios of six chromatic stimuli were obtained, and the brightness additivity for the mixture of red and green was tested. When the reference and test elements were juxtaposed without a gap, the B/L ratio of the test chromatic stimulus decreased with decreasing element size. Brightness additivity failed for an element size of 30' and a 5 degrees bipartite field. Brightness additivity held for a small element size of 3'. When the reference and test elements were separated by a gap 3' in width, the B/L ratios were generally greater than unity regardless of element size. Under these conditions, the brightness additivity also failed for the smallest, that is, the 3' element size.
We compared discrimination and detection in the parafovea for oblique, cathode-ray-tube-generated, square-wave gratings. There is a band of frequencies between roughly 10 and 20 cycles/deg wherein such gratings are detected only in an apparently aliased form. The existence of aliasing is consistent with the cone density and optical quality of the parafoveal visual system, but the spatial frequency at which the aliasing is observed is only about half of what is suggested by cone density. The reason for this result is unclear, but one provocative possibility is that the site of the aliasing is neural rather than receptoral.
We extended our studies of lightness and brightness in complex scenes to cathode-ray-tube simulations of an array of 35 gray reflective patches under spatially varying illuminants. There were three illuminance profiles, an abrupt step, a linear gradient, and a simulation of side illumination, with nine steepnesses of each. In half the sessions observers adjusted a test patch at one end of the illumination gradient in order to match the lightness of a standard patch at the other end of the gradient. In the remaining sessions they matched the brightness of the test patch to that of the standard. For all three illuminance profiles the lightnesses of the patches matched when they had approximately the same simulated reflectance; i.e., there was excellent lightness constancy even though the illuminance gradients were clearly visible.